SIMULATION STUDY OF HYBRID GEOTHERMAL HEAT … · Thesis Prepared for Degree of MASTER OF SCIENCE...

APPROVED: Yong Tao, Major Professor and Chair of

the Department of Mechanical and Energy Engineering

Sandra Boetcher, Committee Member Junghyon Mun, Committee Member Costas Tsatsoulis, Dean of the College of

Engineering James D. Meernik, Acting Dean of the

Toulouse Graduate School

SIMULATION STUDY OF HYBRID GEOTHERMAL HEAT PUMP SYSTEM

IN THE HOT-HUMID CLIMATE

Jiang Zhu, B.E.

Thesis Prepared for Degree of

MASTER OF SCIENCE

UNIVERSITY OF NORTH TEXAS

August 2011

Zhu, Jiang, Simulation study of hybrid ground source heat pump system in

the hot-humid climate. Master of Science (Mechanical and Energy Engineering),

August 2011, 111 pp., 3 tables, 39 illustrations, references, 33 titles.

The beachfront hotel with hybrid geothermal heat pump system (HyGSHP),

located in the hot-humid climate, is simulated by TRNSYS in the thesis, and the

simulation results are validated by the measured data. The simulation of

alternative HVAC systems, complete ground source heat pump and conventional

air source heat pump, are included to conduct the comparative study with

HyGSHP based on the energy consumption and life cycle analysis. The

advantages and disadvantages of HyGSHP are discussed in the thesis.

Two ground source heat exchanger parameters, U-tube size and grout

materials, are investigated in order to study the effects on the ground heat

exchanger thermal performance. The preliminary work and results are shown in

the thesis.

ii

Copyright 2011

by

Jiang Zhu

iii

ACKNOWLEDGMENTS

I would like to thank my parents, my sister and my girlfriend for their

support and encouragement mentally.

I would like to extend my sincere gratitude and appreciation to my adviser,

Dr. Yongx. Tao, for his support, understanding, constructive guidance, and it is

my privilege to have the opportunity to work with Dr Tao, It was his inspiration,

integrity and understanding that got many things this far.

My sincere appreciation also extends to the members of my master thesis

committee, Dr. Sandra Boetcher and Dr. Junghyon Mun for their committed

service and support, their ideas, and suggestions that helped improve my work

significantly.

Last but not the least; I want to express my thanks to all other faculties and

classmates in the Mechanical and Energy Engineering Department for their

assistance and excellent lectures for my knowledge and life.

The findings in this paper are made possible by the financial support from

US Department of Energy Geothermal Program under the Award No.DE-

EE0002802, which is greatly appreciated.

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TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS ....................................................................................... iii

LIST OF TABLES ................................................................................................ vii

LIST OF FIGURES ............................................................................................. viii

NOMENCLATURE ...............................................................................................xi

1. INTRODUCTION .............................................................................................. 1

1.1 Overview of Ground Source Heat Pump and Hybrid Ground Source

Heat Pump .......................................................................................... 2

1.2 Motivation of the Thesis ......................................................................... 7

1.3 Objective ............................................................................................... 8

1.4 Thesis Outline ........................................................................................ 8

2. LITERATURE REVIEW .................................................................................. 10

2.1 Hybrid Ground Source Heat Pump ...................................................... 10

3. MODEL OF HYBRID GROUND SOURCE HEAT PUMP SYSTEM ............... 17

3.1 TRNSYS .............................................................................................. 17

3.2 Building Model ..................................................................................... 19

3.3 Water to Air Heat Pump Component ................................................... 20

3.4 Closed Circuit Cooling Tower .............................................................. 23

3.5 Ground Heat Exchanger ...................................................................... 25

3.6 Pump ................................................................................................... 28

v

4. CASE STUDY-SIMULATION OF HYRID GEOTHERMAL HEAT PUMP FOR BEACH FRONT HOTEL ................................................................................. 30

4.1 Introduction .......................................................................................... 30

4.2 Building Model ..................................................................................... 31

4.3 System Model ...................................................................................... 35

4.4 Summary of Validation and Building Energy ....................................... 40

4.5 Results and Discussion ....................................................................... 46

4.6 Conclusions and Future Work ............................................................. 53

5. PARAMETRIC STUDY OF GROUND SOURCE HEAT PUMP SYSTEM IN HOT HUMID CLIMATE .................................................................................. 55

5.1 Introduction .......................................................................................... 55

5.2 Methodology and Simulation Model ..................................................... 58

5.3 Preliminary Results .............................................................................. 62

5.4 Future Work ......................................................................................... 64

6. CONCLUSIONS AND RECOMMENDATIONS .............................................. 65

6.1 Conclusions ......................................................................................... 65

APPENDIX A INPUT SUMMARY FOR THE HYGSHP SIMULATION MODEL .. 69

APPENDIX B LISTING OF 20 TONS WATER TO AIR SOURCE HEAT PUMP COOLING CAPACITY PERFORMANCE DATA ............................................ 72

APPENDIX C LISTING OF 20 TONS WATER TO AIR HEAT PUMP HEATING CAPACITY PERFORMANCE DATA .............................................................. 76

APPENDIX D LISTING OF 20 TONS WATER TO AIR HEAT PUMP COOLING CAPACITY CORRECTION PERFORMANCE DATA .................................... 80

APPENDIX E LISTING OF 20 TONS WATER TO AIR HEAT PUMP HEATING CAPACITY CORRECTION PERFORMANCE DATA ..................................... 85

vi

APPENDIX F LISTING OF 20 TONS AIR SOURCE HEAT PUMP COOLING CAPACITY PERFORMANCE DATA .............................................................. 87

APPENDIX G LISTING OF 20 TONS AIR SOURCE HEAT PUMP COOLING CAPACITY PERFORMANCE DATA .............................................................. 97

APPENDIX H LISTING OF INDOOR WATER SOURCE HEAT PUMPS IN EACH THERMAL ZONE ......................................................................................... 106

REFERENCES ................................................................................................. 108

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LIST OF TABLES

Page

Table 4-1 Summary of Life Cycle Analysis ......................................................... 51

Table 5-1 Benchmark of Ground Heat Exchanger Specification ........................ 61

Table 5-2 Thermal Conductivities of Typical Grouts and Backfills ..................... 62

viii

LIST OF FIGURES

Page

Figure 1-1 Open loop system. .............................................................................. 3

Figure 1-2 Horizontal loop system. ....................................................................... 3

Figure 1-3 Vertical loop system. ........................................................................... 4

Figure 1-4 Surface water loop system .................................................................. 4

Figure 1-5 Schematic of a typical vertical ground source heat pump system. ...... 5

Figure 1-6 A schematic of a hybrid ground source heat pump system, with cooling tower. ................................................................................................... 6

Figure 3-1 A sample TRNSYS map in the simulation studio ............................ 18

Figure 3-2 Geometric and thermal zone in Google SketchUP . .......................... 19

Figure 3-3 The zone window in the TRNBUILD . ................................................ 20

Figure 3-4 Heat pump schematic . ...................................................................... 21

Figure 3-5 Standard layout of the ground source heat pump, ground heat exchanger (GHX) . ......................................................................................... 22

Figure 3-6 Variables flow chart of the type 504 water source heat pump . ......... 23

Figure 3-7 A closed circuit cooling tower (Picture from www.baltimoreaircoil.com). ....................................................................................................................... 23

Figure 3-8 Flowchart of the basic simulation operation of CCCT component model . ........................................................................................................... 25

Figure 3-9 Schematic view of vertical ground heat exchanger . ......................... 26

Figure 3-10 Schematic of vertical ground heat exchanger . ............................... 27

Figure 3-11 Flowchart of operation of Type 557 vertical ground heat exchanger. ....................................................................................................................... 28

ix

Figure 4-1 Lighting consumption schedule (KJ) in TRNSYS. ............................. 32

Figure 4-2 Equipment schedule (KJ) in TRNSYS. .............................................. 32

Figure 4-3 Southwest view of building. ............................................................... 33

Figure 4-4 Southwest view of simulation building model. ................................... 33

Figure 4-5 Northeast view of building (www.springhillsuitespensacolabeach.com) ....................................................................................................................... 34

Figure 4-6 Building model by GOOGLE SKTCHUP ........................................... 34

Figure 4-7 Schematic diagram the existing HyGSHP configuration. ................... 36

Figure 4-8 TRNSYS map for HyGSHP system. .................................................. 37

Figure 4-9 TRNSYS map for ASHP system........................................................ 40

Figure 4-10 Validation of average entering water temperature to heat pumps. .. 42

Figure 4-11 Validation of DHW and SPA heating consumption. ........................ 43

Figure 4-12 Validation of building calendar energy consumption. ...................... 44

Figure 4-13 The simulated energy consumption composition. ........................... 45

Figure 4-14 The statistic from utility company. ................................................... 45

Figure 4-15 Plot of hourly ground temperature and exiting fluid temperature of ground heat exchanger for HyGSHP. ............................................................. 48

Figure 4-16 Plot of hourly ground temperature and exiting fluid temperature of ground heat exchanger for GSHP. ................................................................. 48

Figure 4-17 Comparison of annual system energy consumption among three types of system. ............................................................................................. 50

Figure 5-1 Building geometry created by Google Sketchup. ............................. 58

Figure 5-2 The cooling and heating load diagram. ............................................ 59

Figure 5-3 GSHP system map in TRNSYS. ....................................................... 60

Figure 5-4 Heat pump consumption with different pipe sizes. ............................ 63

Figure 5-5 Heat pump consumption with different grout and backfills. ............... 63

x

NOMENCLATURE

a Thermal diffusivity [m²/s]

C Volumetric heat capacity [J/m3K]

EWT Entering water temperature to the heat pump

ℎ𝑎𝑖𝑟 Enthalpy of entering ambient air [KJ]

ℎ𝑠𝑎𝑡 Enthalpy of saturated air [KJ]

��𝑎𝑖𝑟 Mass of air flow [Kg/h]

q Heat rejection per unit volume [J/m3]

Q Heat transfer rate (Btu/hr-ft [W/m])

𝑄𝑓𝑙 Rate of heat transfer in the CCCT [KJ/h]

r1 Radius of outer boundary [inch]

rb Outer pipe radius [inch]

Rb Thermal resistance per unit pipe length [K/(m·W)]

Tf Fluid temperature[℃(℉)]

Tm Mean temperature[℃(℉)]

V Volume (ft3 [m3])

y Empirical constant, 0.6

𝜆𝑑𝑒𝑠𝑖𝑔𝑛 Constant based on design condition

λ Thermal conductivity [W/(m·K)]

ω Relative humid [% (base 100)]

1

CHAPTER 1

INTRODUCTION

Due to the increasing seriousness of the threats of climate change and the

energy shortage, and what’s more, with the facts that: the building energy

consuming 40% percents of demanding energy, and the HVAC (heating,

ventilation, and air conditioning) taking up of more than half of the building

energy consumption [1], the innovation and improvement in HVAC is required to

help to relieve the tension and pressure of energy depletion and environment

protection issues.

In recent decades, the ground source heat pump as one of the “green

HVAC” receives more and more attention from broad view due to the renewable

energy conservation from ground source and their energy savings potential; The

geothermal heat pump system can save as much as 50% of energy that the

conventional heating and cooling system does [2]. According to the report from

the department of energy [3], in 2006, there are around 64,000 geothermal heat

pump units which were sold; the residential house took up 53% of the total and

the commercial applications takes 47%. And more and more studies validate and

confirm these advantages.

2

1.1 Overview of Ground Source Heat Pump and Hybrid Ground Source Heat

Pump

Ground source heat pump (GSHP) (sometimes referred as geothermal heat

pump, ground coupled heat pump and so on) with the high efficiency, reject heat

during cooling time and extract heat during heating time from the ground.

Compared with air source heat pump, it is significantly efficient using the deep

ground as the heat source or heat sink instead of the ambient air. However, the

high initial cost and lack of design guideline have been two major obstacles in the

applications. And generally the GSHP can be classified as four main

configurations according to the loop types, each with its own strengths and

weaknesses: open loop system (Figure 1-1), horizontal loop system (Figure 1-2),

vertical loop system (Figure 1-3), surface water loop system (Figure 1-4) [4].

Scope of the research is limited to vertical, closed loop ground source system,

because most of commercial buildings are using this system. The schematic of

the vertical ground coupled system is shown in Figure 1-5 [5], and the

components are introduced in chapter 3 in details.

3

Figure 1-1 Open loop system.

Figure 1-2 Horizontal loop system.

4

Figure 1-3 Vertical loop system.

Figure 1-4 Surface water loop system.

5

Figure 1-5 Schematic of a typical vertical ground source heat pump system.

Nevertheless, in the cooling or heating dominated location, the buildings

have a great imbalance between rejection heating and extraction heating in the

ground. This will cause the ground temperature increase dramatically in the

cooling dominated location and decrease significantly in the heating dominated

location over the years of system running. Then high (low) entering water

temperature will decrease the heat pump performance adversely due to

prolonged cooling (heating). Furthermore, with severely undersized ground heat

exchangers, entering fluid temperature to the heat pump will be out of the range

of the heat pump and make the heat pump fail.

One solution is increasing the total length of the installed ground loop heat

exchanger and/or increasing the spacing between the ground loop heat

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exchanger boreholes. However, it will significantly increase the initial cost, and

also it requires more land area.

The second solution is using the innovative hybrid ground source heat pump

system. Hybrid geothermal heat pump systems (HYGSHP) is a important further

development system which combines the ground source heat pump system with

one supplemental fluid cooler (cooling tower) or one auxiliary heat extraction

device (boiler) in order to decrease the large initial cost of complete ground

source heat exchanger and maintain a higher coefficient of performance during

prolonged running period [6]. The schematic of Hybrid geothermal heat pump

system in this research is provided in Figure 1-6 .The component of composition

and working function will be introduced in details in chapter 3.

Figure 1-6 A schematic of a hybrid ground source heat pump system, with

cooling tower.

7

In this thesis, both systems are simulated based on a building which is

located in the front of beach, conventional air source heat pump system is also

included. And the building model is created based on the blue print and gathered

information from contractor, the simulation is validated based on the measure

data from the Al Barfield paper [7].The simulation tool –transient simulation

package TRNSYS [8] is employed and introduced in the chapter 3 also. The life

cycle analysis is employed to conduct the economical analysis.

Two parameters (U-tube sizes and grout thermal conductivity) involved in the

ground heat exchanger design are studied in this thesis, in order to help

understand the importance of these two parameters, a list of simulation cases is

conducted.

1.2 Motivation of the Thesis

The thesis topic comes from the funded topic Recovery Act – Geothermal

Technologies Program: Ground Source Heat Pumps which is supported by the

department of energy, based on the existing hybrid geothermal heat pump

system which is included in the data gathering in our project, the further analysis

about this building is needed to increase our understanding of the working cycle

of hybrid geothermal heat pump system. The existing hybrid geothermal heat

pump system which is located in Florida is selected as a research building

scenario in hot-humid location.

8

1.3 Objective

The key objectives of this thesis are:

• To simulation the hybrid geothermal heat pump system using the actual

building which is the hotel in the Florida by TRNSYS, and the building model

is created by the GOOGLE SKETCHUP [9].

• To validate the simulation system model in the TRNSYS according to the

available information from the contractor.

• To conduct the comparative study among three types system: hybrid ground

source heat pump system (HyGSHP), air source heat pump system (ASHP),

complete ground source heat pump system, and investigate the advantage

and disadvantage of HyGSHP system in the Florida area where the building

is cooling dominated.

• To study on the parameters based on the ground thermal heat exchanger,

such as the u-tube size, and thermal conductivity of grout which play a

important role of the energy savings of the whole system.

This thesis is arranged as a manuscript-based thesis. Therefore, each of the

studies is presented as a chapter, with relative introduction, modeling process

and conclusion.

1.4 Thesis Outline

Chapter 2 begins with a brief review of selected literature pertaining to

ground heat exchanger and its parameters, hybrid geothermal heat pump.

9

Chapter 3 describes modeling components which are used in the

simulation, such as ground heat exchanger, water to air heat pump, close circuit

cooling tower and pump.

Chapter 4 includes comparative study among HyGSHP, ASHP and

complete GSHP systems. The energy simulation processes are described, and

the calibrations in details are also included. The chapter also includes the life

cycle analysis for three type systems.

Chapter 5 describes parametric study on the ground heat exchanger in hot

humid climate. In this chapter, the sample building with GSHP system is created

to investigate the effects of these parameters in TRNSYS. The results are

discussed based on the energy consumption and cost analysis.

Finally, the main conclusions are made from Chapter 4 and 5 and some

recommendations for possible future extension of this work are presented in

chapter 6.

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CHAPTER 2

LITERATURE REVIEW

This chapter intends to give a brief overview of useful literatures in

understanding the simulation of HyGSHP system.

2.1 Hybrid Ground Source Heat Pump

The ASHRAE Ground Source Heat Pump Engineering Manual [6]

discusses the advantages of hybrid ground source heat pump applications based

on the economical benefit and land area limitation compared with complete

ground source heat pump system. It also discusses the design and sizing

procedure of ground loop heat exchanger and supplemental heat rejecters for

cooling dominated building. The procedure suggests that the capacity of ground

heat exchanger should be selected based on the average of monthly heating and

cooling load instead of the peak load. The supplemental heat rejecters will be

sized to meet the unmet cooling load. It also suggested that the usage of

supplemental heat rejecter during night hours is preferred for closely spaced

vertical boreholes. The guidelines are included in the manual about the

installation of supplemental heat rejecter into the internal pipe, the plate heat

exchanger is suggested when the open loop cooling tower is used. A few options

on the control strategies are mentioned, such as, the set point control based on

11

the upper limit of entering fluid temperatures, operation during night hours for

cold storage and the year around operation in the warmer climates.

Kavanaugh and Rafferty [10] suggest a few HyGSHP alternatives based

on peak block load of design condition. It presents that the needs of HyGSHP is

emphasized due to the high initial cost of long ground loop lengths to meet the

total building heating and cooling by ground. And the peak block load is used to

size supplemental heat rejecters which capacity is calculated based on the

difference between the ground loop heat exchanger lengths for cooling and

heating. It is recommended that the parallel piping method between main loop

and supplemental heat rejecter is preferred when the flow rate in supplement

heat rejecter is much higher that the ground loop flow rate.

Kavanaugh [11] introduces a revised and extended procedures based on

existing design ones as recommended in ASHRAE [6] and in Kavanaugh and

Rafferty [10]. The revised design procedure addresses issues on system controls,

piping arrangements (requirements), equipment efficiency, freeze protection,

maintenance, ground heat exchanger and heat buildup. The revised method

proposes a way for balancing the heat rejected and extracted from the ground

with auxiliary heat rejecter or extractor on an annual basis in order to limit heat

pump performance degradation due to the heat buildup (or ground temperature

increases). To calculate the required annual operating hours of supplemental

heat rejecter needed to balance the heat rejection and extraction from the ground,

the set point control of the ground loop temperature (a typical range of 80℉ to

12

90℉; 27℃ to 32℃) is used. The revised method is then applied to a four-story

office building for HyGSHP system which is located in three different climates (in

order to research the appropriateness of the design method). The author

considers the cost analysis including installation cost and operation cost and

concludes that the HyGSHP is more economically valuable in warm and hot

climates where the cooling loads are dominated. At last, the author mentions

that HyGSHP is less attractive in moderate climate regions and it is hard to justify

for cold climate for economic value except for the building with high internal loads.

Phetteplace and Sullivan [12] present a performance case of a 24,000

ft 2(2,230m2) military base administration building, located in Fort Polk, LA that

uses a HyGSHP system. The HyGSHP system described in the study uses 70

vertical closed-loop boreholes, each 200 ft (61 m) deep with 10 ft (3.3 m)

spacing. The 22 months performance data is collected in the paper. And the

ground loop is sized to meet the peak heating requirements of the building, and a

274 KW (78 tons) is selected as the supplemental heat rejecter which is

controlled based on the set point control which activates the cooling tower when

the heat pump exiting fluid is over 97℉ (36℃ ) and shuts off it when the

temperature falls below 95℉(35℃). From the monitored data, it shows that heat

rejection to the ground is about approximately 43 times higher than the amount of

heat extraction from ground. This indicates that the ground will have a large heat

buildup from the significant imbalance between heat rejection and heat extraction

in the ground. The loop temperature reaches 40.9℃ due to the heat buildup,

13

which is attributed to high differential controller set point, according to increase

the operation hours of cooling time (decrease the controller set point), the heat

buildup will dissipate. From the report, the consumption of the major system

components is presented: heat pumps account for 77% of the total energy, 19%

for circulating pumps, 3% for cooling tower fans and 1% for cooling tower pump.

Singh and Foster [13] reports the first cost savings that resulted from using

a HyGSHP compared to the conventional closed loop source heat pump system.

The system is designed on the 80,000 ft 2 Paragon Center building located in

Allentown, PA and an 85,000 ft 2 elementary school building in West Atlantic City,

NJ. The system in Paragon Center building consists of 88 boreholes, each 125 ft

deep and a maximum capacity 422KW (120tons) closed-circuit cooler. The

system which is designed on elementary school expansion building in West

Atlantic City consists of 66 boreholes, each 400 ft deep and the 411 KW (117

tons) closed-circuit cooler. And it is an example of a hybrid system where the

available space for the borehole field was limited for complete ground heat

exchanger. The report indicates a significant initial cost savings is achieved, but

the operating and maintenance costs go higher.

Gilbreath [14] presents a more detailed study on the HyGSHP system in

Paragon Center, and attempts to establish methods for monitoring system

according to the measurement of energy demand, energy consumption, and loop

temperatures. And the paper investigates the impact of various control options

based on the percentage assistance of the supplemental heat rejecter in

14

rejecting excess heat. And it also discusses the effects of heat recovery and fluid

flow control. The comparison between HyGSHP and complete GSHP without

cooling tower is conducted based on installation and operating cost, the results

quantify potential cost savings due to HyGSHP.

Yavuzturk and Spitler [5] present a comparative study to investigate the

several control strategies by using a short time step simulation model. The

system designed on 14,205 ft2 office building consists of an open loop cooling

tower and a plate heat exchange which is to transfer heat between two loops.

Two different climatic conditions is studied based on 20 year life cycle analysis.

And the advantage and disadvantage of several control strategies for HyGSHP,

such as set point control (operating the supplemental heat rejecter when the

entering or exiting water temperature exceeds 35.8 °C (96.4 °F)), differential

temperature control (operating the supplemental heat rejecter when the

temperature difference between heat pump entering water temperature and

ambient wet bulb temperature exceeds a set value) and a scheduled control

(operation the supplemental heat rejecter based on the season or set time of the

day), is discussed in the study. The results in the thesis indicates that for all the

control strategies, the HyGSHP saves a significant initial cost due to relative the

shorter ground loop lengths compared with the complete ground source heat

pump system. The further saving will be obtained from the smaller circulating

pump. The authors conclude that the differential control strategy own the

maximum efficiency when the most favorable ambient condition is used.

15

Al Barfield [7] reports a Hybrid geothermal heat pump system design and

measurement for a beachfront hotel. The innovate HyGSHP system is

constituted by 98 boreholes at 200 ft depth and 150 tons closed circuit cooling

tower in parallel with the loop of ground heat exchanger. The system serves

three 64KBth/H water-to-water geothermal heat pumps for domestic water heat,

two 390 kBtu/h water-to-water geothermal heat pumps for swimming pool and

spa heating, 300 tons of room unitary geothermal heat pumps. And what’s more,

it uses two 100% outside air rooftop heat pump to supply the fresh air in order to

maintain the indoor air quality. In the paper, the author presents the measure

data for the first year of system operation including: domestic hot water gallons

and water heating energy, rooftop 100% outside air conditioning heat pumps

energy, main geothermal closed-loop pumping energy, closed loop evaporative

fluid cooler tower energy, average monthly return water temperature and so on.

Hackel and Thornton [15] present a simulation study on the HyGSHP

based on a sample building with assumed parameters in order to create a

HyGSHP model and optimizer to help practicing engineer to appropriately size

the ground heat exchanger, supplemental heat rejecter or extractor, in cooling or

heating dominated climate. And the author also creates a life cycle analysis

model in the TRNSYS to investigate the lowest economic combination of

HyGSHP. According to most of simulation cases based on a wide range of

climates and building types, several conclusions are made by the author: First, in

cooling dominated climate, the optimize size of the ground heat exchanger

16

should meet the heating load if the building, the supplemental heat rejecter is

sized based on the peak cooling load that is not met by GHX. The best control

strategy is the one where the cooling tower is operated at low speed whenever

the loop fluid temperature is above the ambient temperature by a set value.

Second, in the heating dominated climate, the supplemental heating device

which is put downstream of GHX can provide best operation efficiency and life

cycle saving. And according to the study, the optimal size of ground heat

exchanger in heating dominated climate is suggested to meet the cooling loads

of the building; the supplemental device will cover the unmet heating load.

Furthermore, the best control strategy is the one where fluid flows through the

ground heat exchanger whenever the temperature rises above or fall below

prescribed temperature set points with the boiler used to maintain the fluid at the

minimum allowable heat pump entering water temperature.

According to the reviewed literature, there are a few of information available

on the simulation study and design suggestions, but few of them mentioned the

validation procedures, and also there is limited literature study on the parametric

study on the ground heat exchanger. This project is providing a HyGSHP case

study with well validated building model and preliminary parametric study on the

ground heat exchanger.

17

CHAPTER 3

MODEL OF HYBRID GROUND SOURCE HEAT PUMP SYSTEM

The chapter gives an overview of the hybrid system model in TRNSYS

(software name) in order to understand the working function in the transient

simulation software package. The hybrid ground source heat pump (HyGSHP) in

TRNSYS is made up of many different components models, which representing a

discrete mechanical part or physical effect in a real HyGSHP system. The

components, such as building model, heat pumps, ground heat exchanger, and

cooling tower etc, are introduced.

3.1 TRNSYS

TRNSYS is a modular simulation program. The component is described as

a black-box with mathematical equation, and user need to specify the inputs,

outputs, parameters, etc. And TRNSYS components are often referred to as

Types (e.g. the Multiple-zone building model is known as Type 56).

And the model of the program is extremely flexible for the user to specify the

components that constitute the system and define the connection way in the

simulation studio which is the main graphic interface, from the simulation studio,

the components can be drag and drop from the TRNSYS component library [16].

Furthermore, the individual components can be modified for different simulation

18

utilizations. And The TRNSYS environment is suitable for detailed analysis of

transient behavior of systems.

Each component in the simulation studio is assigned a UNIT number which

is a reference number that TRNSYS uses to keep track of the instance of the

component in conveying the information about the component to TRNSYS [16].

Figure 3-1 shows a sample of TRNSYS map in the simulation studio.

Figure 3-1 A sample TRNSYS map in the simulation studio [17].

19

3.2 Building Model

To easily input the geometric information into the building model (it is

referred as type 56 in the simulation studio), the interface plug-in software

TRNSYS 3D is developed for the Google SketchUp (shown in Figure 3-2) which

will help the user to create the 3D geometric surface information, required for the

new detailed radiation calculations in the simulation and the thermal zones [17].

The thermal zones which are divided in the Google Sketchup are the zones of

different thermal behavior of building .The non-geometric information, such as

materials, constructions, HVAC, thermal gain, etc is defined in the TRNBUILD

(shown in Figure 3-3).

Figure 3-2 Geometric and thermal zone in Google SketchUP [18].

20

Figure 3-3 The zone window in the TRNBUILD [18].

During the simulation, the TRNBUILD program generates two files that will

be used in TYPE 56 component (multiple zones) according to reads in and

processes a file containing the building description. And the building description

and options within the TRNBUILD program determines and generates

information for the inputs and outputs of TYPE 56 [17].

3.3 Water to Air Heat Pump Component

A heat pump is a device that transfers energy from a low temperature

source to a higher temperature source, mainly including the components of

compressor, evaporator, reversing valve etc [19]. Figure 3-4 shows a schematic

diagram of a heat pump system. It could be either to heat or cool depending on

the refrigerant flowing direction. And the fan is actually included in the heat pump

model which is not shown in the schematic.

21

Figure 3-4 Heat pump schematic [20].

The ground source heat pump is a heat pump that uses the ground as the

heat source or heat sink and transfers heat between fluid loop and conditioned

thermal zones. The Figure 3-5 shows the working function of the system with

building. TRNSYS provides several ways to simulate a water source heat pump,

in this study. Type 504 is selected as the water source heat pump which

interaction between the loop fluid and indoor air is based on the user supplied

performance catalog data (appendix A shows the catalog files in this study), the

catalog data is obtained from manufacture’s performance data including the

cooling capacity and sensible capacity, heat capacity and power consumption of

the unit as a function of air flow rate, entering water temperature, dry-bulb and

wet bulb temperature [20].

22

Figure 3-5 Standard layout of the ground source heat pump, ground heat

exchanger (GHX) [6].

Figure 3-6 shows the schematic view of the flow chart that the information and

variables are implemented, when the Type 504 is called by TRNSYS: First, the

TRNSYS will first determine whether it is cooling or heating based on the control

signal from the Type 108 (5 stages room thermostat). Second, a subroutine is

called to gather all the psychometric information, such as ambient temperature

and humidity, return air temperature and humidity, supply air temperature and

humidity etc. Third, after internal calculation, the output can be obtained based

on the interpolation from the user supplied performance data. [21] (For the more

details of the simulation operation, please see the reference [21] page34-37)

23

Figure 3-6 Variables flow chart of the type 504 water source heat pump [6].

3.4 Closed Circuit Cooling Tower

Figure 3-7 A closed circuit cooling tower (Picture from www.baltimoreaircoil.com).

The closed-circuit cooling tower (CCCT) is a device which cools a liquid

stream by evaporating water that is sprayed on the outside of coils containing the

working fluid (shown in Figure 3-7) . In TRNSYS, Type510 models the closed-

circuit cooling tower based on the algorithm developed by Zweifel et al. [22], In

http://www.baltimoreaircoil.com/

24

the algorithm, the temperature of the outlet fluid of CCCT is equal to the average

temperature of the spay water, and the author prove that it is a good

approximation for all cooling towers. The cooling tower model require user to

define the one set of design condition, and the model algorithm will extrapolates

for other off-range condition based on the design conditions.

In the CCCT model, ℎ𝑠𝑎𝑡�𝑇𝑓𝑙.𝑜𝑢𝑡� is calculated by using an adjusting 𝑇𝑓𝑙.𝑜𝑢𝑡

method in such way until energy balance that the enthalpy of saturated air at

𝑇𝑓𝑙.𝑜𝑢𝑡 is equal to the enthalpy of outlet air as shown in equation (3-1)

ℎ𝑠𝑎𝑡�𝑇𝑓𝑙.𝑜𝑢𝑡� = ℎ𝑎𝑖𝑟(𝑇𝑎𝑖𝑟.𝑖𝑛) + 𝑄𝑓𝑙

𝑚𝑎𝑖𝑟(1−𝑒 −(𝜆𝑑𝑒𝑠𝑖𝑔𝑛�

��𝑎𝑖𝑟��𝑎𝑖𝑟,𝑑𝑒𝑠𝑖𝑔𝑛

�𝑦−1

)

(3-1)

Where,

ℎ𝑠𝑎𝑡: Enthalpy of saturated air

ℎ𝑎𝑖𝑟: Enthalpy of entering ambient air

𝑄𝑓𝑙 : Rate of heat transfer in the CCCT

��𝑎𝑖𝑟: Mass of air flow

y: empirical constant, 0.6

𝜆𝑑𝑒𝑠𝑖𝑔𝑛: Constant based on design condition (shown in equation 3-2)

And 𝜆𝑑𝑒𝑠𝑖𝑔𝑛 = ln[ ℎ𝑠𝑎𝑡�𝑇𝑓𝑙.𝑜𝑢𝑡,𝑑𝑒𝑠𝑖𝑔𝑛�−ℎ𝑎𝑖𝑟�𝑇𝑎𝑖𝑟,𝑖𝑛,𝑑𝑒𝑠𝑖𝑔𝑛�

ℎ𝑠𝑎𝑡�𝑇𝑓𝑙.𝑜𝑢𝑡,𝑑𝑒𝑠𝑖𝑔𝑛�−ℎ𝑎𝑖𝑟�𝑇𝑎𝑖𝑟,𝑜𝑢𝑡,𝑑𝑒𝑠𝑖𝑔𝑛� (3-2)

And then the output outlet fluid temperature, 𝑇𝑓𝑙.𝑜𝑢𝑡 for any off design condition

can be calculated based on this algorithm above with the inputs such as, inlet air

25

temperature,𝑇𝑎𝑖𝑟,𝑖𝑛, relative air humidity,𝑅𝐻𝑎𝑖𝑟,𝑖𝑛, inlet fluid air temperature,𝑇𝑓𝑙𝑜𝑤,𝑖𝑛,

inlet mass flow rate, ��𝑓𝑙 and fan control signal. The operation process is shown

in the flowchart (Figure3-8).

Figure 3-8 Flowchart of the basic simulation operation of CCCT component

model [21].

3.5 Ground Heat Exchanger

The ground heat exchanger (shown in Figure 3-9) (as previously mentioned,

only vertical ground heat exchanger will be discussed in this study) is the most

important part for the HyGSHP simulation. For the typical U-tube ground heat

exchanger construction, firstly, a vertical borehole is drilled into the deep ground.

Secondly, the U-TUBE ground heat exchanger will be pushed into the borehole,

the surrounding gab between the U-TUBE and borehole will be filled with the

grout or virgin soil.

26

Figure 3-9 Schematic view of vertical ground heat exchanger [6].

The configuration of vertical GHX field is illustrated in Figure 3-9. In typical

U-tube ground heat exchanger applications, the total length of ground heat

exchanger has the largest effect on the initial cost and the future operation

efficiency that impacts on the heat pump entering water temperature.

In TRNSYS, Type 557 [23] is created for the model of vertical ground heat

exchanger which thermal interaction between fluid loop and ground based on the

duct storage (DST) theory. The DST model [24] assumes that the boreholes are

placed uniformly in the cylinder storage and the transient temperature distribution

27

is calculated from three parts: a global temperature solution ( at the scale of

entire field), a local solution(at the scale of single borehole) and a stead-flux

solution( interaction between both scales). The global and local problems are

solved by the explicit finite difference method, whereas the steady flux solution is

obtained by the analytical solution. The total temperature is then calculated by

the superposition of these three parts [24].

Figure 3-10 Schematic of vertical ground heat exchanger [23].

There are lots of parameters needed to specify in the TYPE 557 in order to

obtain the output. Figure 3-11 illustrate the flowchart of the operation. The details

of calculation processes for the GHX model are provided in the reference [6]

pages 39- 40.

28

Figure 3-11 Flowchart of operation of Type 557 vertical ground heat exchanger.

3.6 Pump

Based on existing HyGSHP system, the constant speed water pump is

selected and sized in the simulation model. The pump is mainly used to circulate

the fluid in the fluid loop. Type 3b component model in TRNSYS is simplified to

TYPE 557

Vertical GHX

DST FUNCTION

Storage volume

Borehole depth

Header depth

No. of boreholes

No. of boreholes

Borehole radius

Borehole radius

kstorage

kgroute

kpipe

Pipe size

Pipe size

Cstorage

Cfluid

fuild properties

Tstorage

Tstorage

Minflow

Tinlet minlet

Tout Tstorage QN

Mout

29

control of flow rate of entire fluid loop. And the flowrate in the pump parameter list

must be specified in order to determine the fluid rate in the fluid loop [25].

30

CHAPTER 4

CASE STUDY-SIMULATION OF HYRID GEOTHERMAL HEAT PUMP

FOR BEACH FRONT HOTEL

This chapter outlines the description of building model, simulation model of

hybrid ground source heat pump (HyGSHP), ground source heat pump (GSHP)

and air source heat pump (ASHP), input parameters, validation processes and

life cycle analysis.

4.1 Introduction

A hotel with hybrid ground source heat pump system in the Pensacola is

simulated by the transient simulation software package TRNSYS. The validation

is conducted to verify the simulation result using the monthly average entering

water temperature to heat pump and monthly facility consumption data. The

building model with alternatives HVAC systems, complete ground source heat

pump with lengthened ground heat exchanger and conventional air source heat

pump are simulated also. The results are presented to show the advantages and

disadvantages of HyGSHP compared with the other two systems in terms of

energy consumption, total cost analysis and the system life time

What’s more, the hotel is installed with hybrid ground source heat pump due

to limitation of the land area according to descriptions in the designers’ report [7].

But in order to investigate the advantages and disadvantages of HyGSHP

31

compared with complete ground source heat pump system, it is assumed that

there is enough land area for a complete ground source heat pump system.

4.2 Building Model

The hotel which to be simulated is located on a barrier island on the Florida

Gulf coast, and there are 117 room facilities with large public parking area, a

meeting room, a large dining room and a limited breakfast area which is in total

80,145𝑓𝑡2, and the hotel includes some amenities such as one health club, two

large outdoor heated pools, one outdoor heated spa and a large, shallow

children’s pool [7].

Based on the blueprint and the images, the building model is created using

GOOGLE SKETCHUP which is a free 3D modeling program [2]. Figures 4-3, 4-4,

4-5 and 4-6 show the comparative views of the real building and the simulation

building model. Several considerations are made when the building model are

created in Google Sketchup and TRNSYS software package.

1. The building is divided into 9 thermal zones, which is served by one unitary

equal capacity heat pump units instead of several separate small capacity heat

pumps.

2. Building materials (walls, roofs and windows) are specified based on the

blueprints. Lighting and equipment schedule are properly assumed as shown in

Figures 4-1 and 4-2.

32

Figure 4-1 Lighting consumption schedule (KJ) in TRNSYS.

Figure 4-2 Equipment schedule (KJ) in TRNSYS.

3. The total number of occupants in the hotel is set as 300, and lighting and

equipment load is set as 1 W/𝑓𝑡2 and 1.1 W/𝑓𝑡2 based on the ASHRAE standard

90.1.

4. Infiltration is set as 1 1/h based on the beachfront location and the fresh air

requirement.

33

5. Thermostat set points of 21℃ heating and 23℃ cooling are used in all zones

during all days.

Figure 4-3 Southwest view of building.

(Picture from www.springhillsuitespensacolabeach.com)

Figure 4-4 Southwest view of simulation building model.

http://www.springhillsuitespensacolabeach.com/

34

Figure 4-5 Northeast view of building (www.springhillsuitespensacolabeach.com)

Figure 4-6 Building model by GOOGLE SKTCHUP

35

4.3 System Model

The hotel includes 117 room unitary heat pump units (180 tons in total), two

100% outside air rooftop air conditioners ,three 64KBtu/h water to water heat

pumps for domestic heat water and two 390 KBtu/h water to water heat pump for

swimming pool and spa heating equipments.

Because of the limited installation field area available for the geothermal

heat exchanger loop, the designer selected a 150 tons closed-loop evaporative

fluid cooler to parallel the ground-coupled loop field which owns 98 boreholes

with 200 depths and 1” U-tube to compose the HYGSHP system.

In order to simulate the HyGSHP system, the transient simulation software

package TRNSYS is employed to simulate the short time step for one year

period simulation (5 minutes is set as the simulation time step), and the hourly

typical meteorological year for the Pensacola is used. The HVAC system worked

with the well validated building model can predict the enter water temperate, the

system profile and the building energy consumption etc. And the building model

and all the heat rejecting and extraction system like water to water heat pumps,

air source heat pumps, cooling tower are included in the simulation system.

36

Figure 4-7 Schematic diagram the existing HyGSHP configuration.

The diagram of HyGSHP in the hotel is shown in Figure4-7; the cooling

tower is activated when the entering water temperature is over 29 ℃ . The

components such as closed circuit cooling tower, vertical ground heat exchanger,

water to air heat pump etc is included in the TRNSYS model. The TRNSYS map

for this hotel HyGSHP system is shown in Figure4-8. Figure4-9 shows the same

building model with conventional HVAC system for the purpose of comparison

with the existing HyGHSP system. Another TRNSYS map for GSHP system isn’t

listed in the paper due to using the similar components with HyGSHP system.

37

Figure 4-8 TRNSYS map for HyGSHP system.

The components which are used in the simulation model are listed below:

TYPE 56-Multi-zone building

TYPE3b-Single speed pump

TYPE 4a- Storage Tank

TYPE14e: Temperature

Pump-1

Water draw

Equa

GSHP_3RDWEST

Turn Radiation

Weather data

Psychrometrics

Sky temp

Building

Temperature

Type108

GSHP_2STEAST

GSHP_1STWEST

Monthly

Mixing Valve

Circulation Pump

Diverter2

GSHP_1STEAST

GSHP_2STWEST

Type108-2

Type108-3

Type108-4

Type108-5

GSHP_3RDEAST

GSHP_4THWEST

GSHP_4THEAST

GSHP_5THEAST

Type108-6

Type108-7

Type108-8

Closed Circuit Cooling Tower

Type11d

Cooling Water Pump

Type11f

Type108-10

Type108-9

DHW

POOL&SPA-1

POOL&SPA-2

Mixing Valve-2

Diverter2-2

Hot water tank

Ambient pressure

Type2b

Mains temperature

GROUND HEAT EXCHANGER

100% OA ROOFTOP AC 2100% OA ROOFTOP AC1

38

TYPE14h-Time Dependent Forcing Function: water draw

TYPE14b-lighting consumption/schedule

TYPE14c-other equipment consumption/schedule

TYPE108-Five-stage thermostat

TYPE69b- Effective Solar temperature

TYPE33e-Psychrometrics: dry bulb and relative humidity

TYPE504b-Water to air heat pump

TYPE557- Vertical U-tube Ground Heat Exchanger

TYPE647- Fluid Diverting Valve

TYPE 649 - Mixing valve for fluids

TYPE 665 -AIR-SOURCE HEAT PUMP

TYPE 668 -Water to Water Heat Pump

TYPE510 -Closed Circuit Cooling Tower

TYPE11f -controlled mix valve

TYPE11d –controlled fluid diverter

9 TYPE 577-water to air heat pumps (named as GSHP_1st west,

GSHP_1steast and so in the TRNSYS map) are connected with the TYPE56-the

building model in order to control the room temperature and humidity. Each heat

pump is controlled by one TYPE 108-thermostat which room set points use 21℃

for cooling and 23℃ for heating respectively. The main geothermal loop cycle

comprises of heat pumps ( including water to air heat pump for room

conditioning, water to water to water heat pumps for domestic hot water and

39

heating spa), water pumps ( controlling the flow rate of the main loop), and TYPE

557 vertical ground heat exchanger model. The TYPE 510-closed circuit cooling

tower is connected with the main loop according to TYPE11d controlled mix

valve and TYPE 11f controlled fluid diverter that are partly opened when

entering water temperature is over 29℃ monitored by TYPE108 controlled.

The weather system is installed to simulate the environment condition of

cooling tower, building, ground heat exchanger, heat pumps and so on. The

domestic hot water and heating spa are simulated by three TYPE668-water to

water heat pumps and TYPE4a-storage tank which temperature and flow rate are

controlled by the 14h- water draw and the 14e temperature. And the 100%

outside air roof top conditioner in the system is simulated by TYPE 665 air

source heat pump which supply air temperature is set as ambient temperate in

the simulation.

The components connection in the TRNSYS map of the complete ground

source heat pump system is the same as hybrid system except only without the

cooling tower system.

Air source heat pump system (shown Figure 4-9) utilizes the 9 TYPE665 air

source heat pumps to control the room temperature and humidity. The water to

water heat pump is used to simulate the domestic hot water and heating spa.

40

Figure 4-9 TRNSYS map for ASHP system.

4.4 Summary of Validation and Building Energy

In order to verify the simulation model and building model, the validation

process is important to make the results convincing and accurate.

In this study, the first year measure data is used for validation of the first

year of simulation in order to verify the building model and system model in

TRNSYS. The hotel is monitored by Al Barfield (2006)[7] during the first year of

Turn

Radiation

Weather data

Psychrometrics

Sky temp

BuildingType108-5

Type65d2NDWEST

Type108

TYPE24

Type25c

Monthly-2

1STWEST

1STEAST

2NDEAST-4

Type108-2

Type108-3

Type108-4

3RDWEST

3RDEAST

4THWEST

4THEAST

5THEAST

Type108-6

Type108-7

Type108-8

Type108-9

100% OA ROOFTOP AC 2100% OA ROOFTOP AC1

Hot water tank

Mains temperature Water draw

Type668

Type2b

Pump-1

Pump

Type668-2

Type668-3 Diverter2-2

Mixing Valve-2

Monthly

41

hotel open to the public, and the average return water temperature, domestic hot

water and heating spa consumption and total building consumption are metered.

The simulation results and the measured data are compared

comprehensively in the Figure 4-10, Figure 4-11, Figure 4-12, Figure 4-13 and

Figure 4-14 based on the first year of system operation. According to Figure 4-10,

the Average entering water temperature from the simulation is well matched with

measure data. And several energy consumption comparisons are illustrated in

the Figures 4-11, and 4-12 which shows the DHW&SPA heating consumption,

and the total building calendar energy consumption respectively.

According to these three pictures, there is difference between the simulation

data and measure data. There are three main reasons to explain it.

1. The typical meteorological year weather data is different from the real weather

data; it causes the errors between the simulation and real operation.

2. For the validation with DHW and SPA heating, it is difficult to be consistent

with the actual operation and is hard to simulate the usage with accurate water

draw and operation schedule.

3. The assumed lighting and equipment consumption is not accurate to predict

the real energy consumption and heat gain.

Furthermore, Picture 4-13 shows the composition of the annual total building

consumption, the simulation result have less than 2% of difference with the

statistic map from utility company (shown in Picture 4-14)

42

Figure 4-10 Validation of average entering water temperature to heat pumps.

0

5

10

15

20

25

30

35

40

1 2 3 4 5 6 7 8 9 10 11 12

Average entering water temperature

(deg C)

Month

simulated data

measured data

43

Figure 4-11 Validation of DHW and SPA heating consumption.

0

5000

10000

15000

20000

25000

1 2 3 4 5 6 7 8 9 10 11 12

monthly energy (kwh)

Month

measureddata

simulateddata

44

Figure 4-12 Validation of building calendar energy consumption.

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

1 2 3 4 5 6 7 8 9 10 11 12

Monthly building energy

consumption (kwh)

Month

simulated data

measured data

45

Figure 4-13 The simulated energy consumption composition.

Figure 4-14 The statistic from utility company.

100%OA ROOFTOP AC

7%

Lighting,equipment room unitary heat

pumps consumption

64%

spa and DHW 9%

water pump 18%

cooling tower

2%

SIMULATION BUILDING ENERGY SUMMARY

46

4.5 Results and Discussion

After the validations above, the validated building model and system model

are set up well. In order to reseach the advantage and disadvange of HyGSHP

compared with other type of HVAC system, the building model with the

alternative complete GSHP and ASHP system is simulated. And Figure4-15

(screenshot from TRNSYS plotter) shows the ground temperature (red line) and

subhourly exiting water temperature of GHX for the validated HyGSHP system.

Then the HyGSHP system is substitued by the complete ground source heat

pump system which contain 245 boreholes with 200 ft depth with total estimated

250 tons capacity. Figure 4-16 shows the ground temperature and exiting fluid

temperature of GHX profile in the simulation of GSHP system.

From Figures 4-15 and 4-16, with the same HVAC system capacity, the

exiting water temperature of complete GSHP has lower fluctuation and is

controlled more effeciently than the exiting fluid temperature of HyGSHP. The

reasons are as follow:

First of all, these two HVAC systems, the spacing of boreholes and the inlet

mass flow rate of GHX is set as the equal for the HyGSHP and GSHP.

And according to the heat convenction equation(4-1):

𝑞 = ℎ 𝐴 ( 𝑇𝑠𝑢𝑟𝑓𝑎𝑐𝑒 − 𝑇𝑓𝑙𝑢𝑖𝑑 ) (4-1)

Where,

q, energy transfer rate

47

h, convection heat-transfer coefficient

𝑇𝑠𝑢𝑟𝑓𝑎𝑐𝑒 , surface temperature of U-TUBE

A, surface area of U-TUBE

Because the complete ground heat exchanger with lengthened ground heat

exchange length has the larger surface area of U-TUBE of ground heat

exchanger than surface area of U-TUBE of the HyGSHP, more heat is

transferred from fluid to the ground in the GSHP that the heat transferred in the

HyGSHP.

Therefore, according to the equation 4-2, with the same mass flow rate and

thermal conductivity for GSHP and HyGSHP, complete ground source heat pump

discharges more heat into ground; therefore, the outlet temperature 𝑇𝑜𝑢𝑡𝑙𝑒𝑡 is

lower than than for HyGSHP when the fuild goes through the ground heat

exchanger ( see Figures 4-15 and 4-16). This may explain why the case of

HyGSHP resulted in a higher ground temperature.

𝑞 = 𝑚 𝑐 ( 𝑇𝑜𝑢𝑡𝑙𝑒𝑡 − 𝑇𝑖𝑛𝑙𝑒𝑡 ) (4-2)

Where,

��, mass flow rate

C, thermal conductivity

48

Figure 4-15 Plot of hourly ground temperature and exiting fluid temperature of

ground heat exchanger for HyGSHP.

Figure 4-16 Plot of hourly ground temperature and exiting fluid temperature of

ground heat exchanger for GSHP.

49

If the same outlet temperature for these cases is assumed, the mass flow

rate for the HyGSHP has to be adjusted . This effect should be studied further in

the future.

Figure 4-17 presents the energy comparsion among three HVAC systems.

The conventional air source heat pump system consumes 6% more than

HyGSHP and 15% more than GSHP because of lower effeciency.

And Al Barfield estimates that the complete gournd source heat would have

been 40,107kwh saving compared with HyGSHP, and it is consistent with the

simulation results between HyGSHP and GSHP from the simulation (shown in

Figure 4-17).

0

100000

200000

300000

400000

500000

600000

700000

GHSP HyGSHP ASHP

Annual energy consumption

50

Figure 4-17 Comparison of annual system energy consumption among

three types of system.

(Note: the total consumption include the main loop pumping water source heat

pump (or air source heat pump) consumption, and DHW & SPA heating

consumption.)

The life cycle analysis is conducted and the economic feature of these three

systems is analyzed, the following assumptions are made:

1. $10.00 per foot at borehole is used for the calculation of the cost of the

ground heat exchanger (Kavanaugh (1998) uses the value the $6.00 per foot,

the inflation is considered in the study).

2. Cooling tower cost is $17,000 from the manufacturing company quoted price.

3. Air source heat pumps and water source heat pumps are calculated based

on $1000/ton and $983/ton respectively. [26]

4. The cost of electricity is assumed to be $0.102 per kWh.

5. Tax credit program is consider in the analysis , which offers tax credit up to a

30% of initial cost without cap. Also, in some parts southern States, a

$300/ton rebate program is offered by energy companies.

6. According to a few studies on this subject, the maintenance costs were used

as annual maintenance costs and estimated as $0.027/𝑓𝑡2 per year for the

GSHP system tonnage. For maintenance cost of conventional systems, RS

51

Means Facility Maintenance Cost Data was used. The cost is $0.102/𝑓𝑡2 per

year [27].

The equation to calculate the life cycle cost in the paper is summarized as

equation (4-3)

Life cycle cost = Initial cost after rebate + Energy cost of 20 years+

OM&R of 20 years (4-3)

Where,

Initial cost after rebate = ground heat exchanger cost+ heat pumps cost + cooling

tower cost- credit (4-4)

Credit= 30 % x (ground heat exchanger cost+ heat pump cost) (4-5)

OM&R: operation maintenance and repair cost

Compared with conventional air source heat pump system:

Payback period for GSHP or HyGSHP = (initial cost difference between

GSHP or HyGSHP and ASHP)∕(the annual net savings) (4-6)

Table 4-1 Summary of Life Cycle Analysis

HyGSHP GSHP ASHP

System description 80,145 𝑓𝑡3 building

area

98@200ft GHX

80,145 𝑓𝑡3 building

area

245@200ft GHX

80,145𝑓𝑡3 building

area

Land area 40,000 ft2 100,000 ft2 ---

52

requirement for

system

Cost of Ground heat

exchanger

$196,000 $490,000 ---

Heat pump (water

source or air source)

$294,900 $294,900 $315,000

Cooling tower cost $17,000 -- --

Credit $147,270 $235,470 ---

Initial cost after

rebate

$343,630 $549,430 $315,000

20 years

maintenance cost

$50,000 $43,278 $163,490

20 years of electricity

cost

$1,389,241 $1,278,934

$1,473,336

Life cycle cost $1,782,871 $1,871,642 $1,951,826

Payback period 2.9 years 14 years ---

Notes: 1. the land cost is not included in the initial cost. It assumes the hotel

already owns this property.

2. Electric consumption is based on the first years running (actually the

consumption will increase a little after long time operation because of increase of

the ground temperature)

53

According to the results in the Table 4-1, HyGSHP has the best economic

benefit compared with other two types of system. Even if the complete ground

source heat pump system has the advantage of better energy performance, it still

cannot beat HyGSHP system because of large initial cost and land area

utilization. Both innovated HyGSHP and GSHP system have the economic

advantage compared with the conventional air source heat pump.

4.6 Conclusions and Future Work

In the chapter, three type HVAC systems are studied and simulated based

on well validated building model. The designers of the HVAC system designed

the hybrid ground source heat pump system due to the land area limitation for

the complete ground source heat pump system. Nevertheless, in order to make a

comparison between the performance of hybrid ground source heat pump and

the complete ground source heat pump, the enough land area is assumed for the

complete ground source heat pump.

In order to avoid the degradation of ground source heat pump in the hot-

humid climate due to the imbalance between heating load and cooling load of the

building, two enhanced systems, complete ground source heat pump with

lengthened ground heat exchanger length and the hybrid source heat pump are

the two main solutions. According to the comparative simulation study above, the

complete ground source heat pump system which increases the total borehole

length has the better energy performance than the existing hybrid system.

However, the large initial cost and large land area limitation for the building make

54

the system as the second option, and the payback period is too long compared

with HyGSHP.

Hybrid ground source heat pump significantly decreases the initial cost and

the requirement of land area and maintains relatively high energy performance.

According to the 20 years life cycle analysis, the hybrid system owns the

economical advantage compared with other two systems in the hot-humid

climate. But for the longer time running, complete ground source heat pump will

overtake the hybrid system due to the better energy performance.

55

CHAPTER 5

PARAMETRIC STUDY OF GROUND SOURCE HEAT PUMP SYSTEM IN HOT

HUMID CLIMATE

Two parameters including U-tube sizes and grout or fill thermal conductivity

are studied based on the sample residential building in the Hot-humid climate

Tampa, Florida. In this study, a list of comparative simulation cases with varied

parameter value is simulated to research the importance and effect of U-tube

size and grout materials on the ground heat exchanger efficiency. The simulation

software TRNSYS is employed to fulfill this task. A complete building model with

traditional local building materials is created simultaneously .The results present

the profile of heat pump energy consumption comparative analysis based on

varied parameters. Future work needs to be conducted for the cost analysis,

include the installation cost and materials cost from the contractor.

5.1 Introduction

It is estimated that the installation geothermal heat pump system (GSHP)

has continuously grown from 10% to 30% recently [28]; GSHP is more efficient

than the conventional HVAC, due to utilize the ground as heat source or heat

sink. Accordingly, the innovative system is attractive to engineers in order to cut

the carbon dioxide emission, it is estimated ground source heat pump will cut

global CO2 emissions by more than 6% [29]. To improve the GSHP design and

56

save more energy, the size selection and material utilization in ground source

heat pump application are strongly recommended to study, and there is little

information available for the guidance of engineer in this area.

The U-tube size in borehole is critical and complicate to ground source heat

exchanger design due to the multiple influence factors, pumping power (pipe size

should be large enough to keep the pumping power small and flow type (pipe

size should be small enough to avoid laminar flow). The selection of grout also

depends on lots of other factors, such as chemical safety to local ground water,

the ability to support the borehole, and the cost.

However, both parameters influence the design length and performance of

heat exchanger. Allan and Kavanaugh [30] conducted experimental study to

improve the thermal conductivity of grout and discuss its importance to design

the heat exchanger length. In this study, the parameters are studied within the

ground source heat pump system with complete building model so as to study

the thermal performance of ground heat exchanger. The ground source heat

pump system model and complete building model are presented and various

simulations are conducted in the study.

Ground heat exchanger model in TRNSYS which is the key component of

ground source heat pump system model is created based on the theory of the

DST model [5].

The governing equation for fluid temperature in DST model is expressed as:

Tf(t) ≅ Tm(t) + q2πλ

�2πλRb + ln(r1rb� − 3

4] at

r12> 0.2 (5-1)

57

And Tm(t) = qπ𝐶r12

∗ t (5-2)

And the heat rejection to the ground is governed as

qπr12

= λ(Tf−Tm)l2

(5-3)

And l = r1�12

[ln �r1rb� − 3

4+ 2πλ Rb (5-4)

Where

r1: radius of outer boundary

Tf : fluid temperature

Tm : mean temperature

λ ∶ thermal conductivity,

C: volumetric heat capacity,

a : thermal diffusivity

rb: outer pipe radius

Rb: thermal resistance per unit pipe length

q: heat rejection per unit volume

From the equation, (5-1) and (5-3) the fluid temperature and heat rejection

is proportional to pipe size the thermal conductivity. As the enter water

temperature to heat pump is one of the core factors to effect the heat pump

consumption, it is easy to understand that the parameters ARE crucial and

decisive to the thermal performance of ground heat exchanger and the heat

pump energy consumption

58

5.2 Methodology and Simulation Model

The sample building is created by GOOGLE SKETCHUP which is free 3D

simulation software (shown in Figure5-1). The dimension of the sample

residential building is 60 feet length, 40 feet width and 10 feet height like the

normally residential house in Florida area. The traditional Dallas wall, roof and

floor material is applied to simulate system.

Figure 5-1 Building geometry created by Google Sketchup.

In order to determine the heat pump capacity and heat exchanger capacity

for this sample house, the cooling and heating load is simulated in the TRNSYS,

the peak heating and cooling load is 30000 KJ/h (shown Figure5-2), the 3 tons

heat pump unit is selected to condition the building within the cooling and heating

set point 70 and 73 respectively. The water pump is selected as constant 8

GPM, 1 hp (all flow rates in the research pipe size types will be in turbulent flow).

59

The specification of ground source heat pump is listed in the Table5-1, the length

of geothermal heat exchanger and borehole number is based on the similar

project design specification in Florida [31].

Figure 5-2 The cooling and heating load diagram.

Figure 5-3 Illustrates the GSHP connection diagram in the TRNSYS.

All components for in TRNSY are defined as the type like a black box

governed by the mathematical equation, which user set the parameters and

supply the input. The types which are used in this simulation are listed as below:

60

Figure 5-3 GSHP system map in TRNSYS.

Type 56-Multi-zone building

Type 557a-Vertical ground heat exchanger

Type114-Single speed pump

Type 108-Five-stage thermostat

Type 69b- Effective Solar temperature

Type 33e-Psychrometrics: dry bulb and relative humidity known

Type 504b-Water to air heat pump

Turn

Radiation

Weather data

Psychrometrics

Sky temp

Dallas green house

HEAT PUMP

WATER PUMP

GROUND HEAT EXCHANGER

OUTPUT PLOTTERTHERMOSTAT

Monthly

output

61

Table 5-1 Benchmark of Ground Heat Exchanger Specification

Specification Value

Storage volume 287534.718819 ft3

Borehole depth 300.00001 ft

Header depth 6.56168 ft

Number of boreholes 3

Borehole radius 4.5 in

Storage thermal conductivity 1.399855 BTU/hr.ft.℉

Storage heat capacity 30.060575 BTU/ft3.℉

Outer radius of u-tube pipe 0.525 in

Inner radius of u-tube pipe 0.412 in

Center-to-center half distance 1 in

Fill thermal conductivity 0.85 BTU/hr.ft.℉

Pipe thermal conductivity 0.242704 BTU/hr.ft. ℉

Initial ground temperature 65 ℉

Thermal conductivity of layer 1.4 BTU/hr.ft. ℉

During the simulation, the schedule 40 pipes with 3/4 inch, 1 inch 1 1/4 inch

1 1/2 inch and 2 inch are input to conduct the energy simulation comparison. The

range pipe size is limited because of borehole diameter. Table 2 shows the list of

grout which will be selected as research objectives. 20% Bentonite is the

62

traditional backfill type with very poor thermal conductivity, 30% Bentonite -

30%Quartizite and 20% Bentonite- 40% Quartzite is the enhanced grout with a

good thermal performance,but the price is higher. Concrete(50% quartz sand)

has the highest thermal conductivities, but it also costs highest.

Table 5-2 Thermal Conductivities of Typical Grouts and Backfills [32]

Grouts and Additivies Thermal conductivities K

(Btu/h. ft.℉)

20% Bentonite 0.42

30% Bentonite -30%Quartizite 0.70-0.75

20% Bentonite- 40% Quartzite 0.85

Concrete(50% quartz sand) 1.1-1.7

5.3 Preliminary Results

After a list of simulations with varied parameters input, Figures 5-4 and 5-5

present the energy consumption graphs with pipe sizes and grout materials

respectively. According to Figure 5-4, the energy consumption of heat pump will

decrease when the pipe size increases. There is around 1.2 % saving when the

pipe increases one diameter from the graph. And also Figure 5-5 shows, with the

thermal conductivity increasing, the heat pump consumption will decrease

proportionally. From 20% Bentonite to 30% Bentonite -30%Quartizite, the

consumption decreases 9% of annual heat pump energy consumption.

63

Figure 5-4 Heat pump consumption with different pipe sizes.

Figure 5-5 Heat pump consumption with different grout and backfills.

8.40E+03

8.45E+03

8.50E+03

8.55E+03

8.60E+03

8.65E+03

8.70E+03

8.75E+03

8.80E+03

0 0.5 1 1.5 2

Annual energy consumption

(KWH)

Pipe size (inch)

7.80E+03

8.00E+03

8.20E+03

8.40E+03

8.60E+03

8.80E+03

9.00E+03

9.20E+03

9.40E+03

9.60E+03

9.80E+03

20% Bentonite 30% Bentonite -30%Quartizite

20% Bentonite-40% Quartzite

Concrete(50%quartz sand)

Annual energy consumption( KWH)

64

5.4 Future Work

In order to further analyze the economic benefit with different U-tube sizes

and grout materials, the data of materials cost and installation cost (U-tube and

grout) will be collected to conduct the cost analysis in future. And in the study, it

is the limitation that the constant pumping size is set for all the pipe sizes, which

is using the 1 hp with 8gpm constant speed water pump. The future work will

include the pumping selection based on the effect of pipe size. And also the

commercial size building will be considered to further research the energy saving

with building size and heating and cooling load.

65

CHAPTER 6

CONCLUSIONS AND RECOMMENDATIONS

6.1 Conclusions

In this thesis, Hybrid Ground Source Heat Pump system in the Hot-Humid

area is simulated using the complete building model and TRNSYS system model.

And two key parameters, U-tube diameter and grout or fill materials, in the

Ground Source Heat Pump system is investigated based on the heat pump

consumption using the whole building system simulation method.

Firstly, the comparative simulation study is made among the HyGSHP,

complete GSHP and ASHP systems, the life cycle analysis results are presented

in the thesis. The HyGSHP system is constituted with the vertical ground heat

exchanger with 98 boreholes at 200 ft depth and 150 tons closed circuit cooling

tower in parallel connection with the main loop. Furthermore, the complete

building modeling which is divided into 9 thermal zones is created with the

defined materials, thermal gains and typical meteorological year weather data.

The innovated system includes 117 unitary water-to-air heat pumps and 5 water-

to-water heat pump which is using ground heat exchanger as the heat source

when heating is required or heat sink when cooling is required. And two 100%

outside air rooftop heat pumps are simulated in the system which supply the

fresh air to each thermal zone. The validation of system is conducted used the

66

measure data of the first year system operation, such as monthly average

entering water temperature to heat pump, cooling tower consumption etc.

Secondly, the designers of the HVAC system designed the hybrid ground

source heat pump system due to the land area limitation for the complete ground

source heat pump system. Nevertheless, in order to make a comparison between

the performance of hybrid ground source heat pump and the complete ground

source heat pump, the enough land area is assumed for the complete ground

source heat pump (borehole spacing , mass fluid rate is kept as the same with

HyGSHP, details referred as APPEDIX A). Two enhanced systems, complete

ground source heat pump with lengthened ground heat exchanger length and the

hybrid source heat pump are compared based on the life cycle analysis cost.

According to the results above, the complete ground source heat pump system

which increases the total borehole length has the better energy performance than

the existing hybrid system. However, the large initial cost and large land area

limitation for the building make the system as the second option, and the

payback period is too long compared with HyGSHP. Hybrid ground source heat

pump significantly decreases the initial cost and the requirement of land area and

maintains relatively high energy performance. According to the 20 years life cycle

analysis, the hybrid system owns the economical advantage compared with other

two systems in the hot-humid climate. But for the longer time running, complete

ground source heat pump will overtake the hybrid system due to the better

energy performance.

67

Thirdly, parametric study of ground source heat pump system with sample

building model is presented in the paper, the results shows the heat pump

energy consumption varies significantly because of the parameter effect. It will

help to create the guideline of the construction of ground heat exchanger.

In the study, the comparison between the complete ground heat

exchanger and hybrid geothermal source heat pump is based on the special

case that the spacing, fluid mass fluid rate etc. for both systems are kept the

same, the future work may conduct the comparison based on other conditions or

assumptions in order to show a more completely and comprehensively

comparative study

Moreover, for the HyGSHP system design, the future work should

emphasis on the improvement of thermal performance of ground heat exchanger

in hybrid ground source heat pump system. The methodology will include the

development on the sizing of cooling tower, GHX and, the connection method

and control strategies Yavuzturk and Spitler [7] mention differential temperature

control (operating the auxiliary rejecter whenever the difference between heat

pump fluid temperature and ambient air temperature exceeds a set value) has

the economic advantage compared with the strategy with set point control

(operating the auxiliary rejecter whenever the heat pump entering or exiting fluid

temperature is over one set value ) which is used in this hotel and is simulated

for the HyGSHP in this paper . And Hackel and Thornton [15] created a general

guideline to select an equipment configuration, size equipment and control

68

strategies. More works need to be done in order to verify these conclusions in

future.

Lastly, more parametric studies need to be done in order to create more

comprehensive guidelines for ground heat exchanger design.

69

APPENDIX A

INPUT SUMMARY FOR THE HYGSHP SIMULATION MODEL

70

Construction Details Existing Building

Total Conditioned Area (m2) 7595

number of floors 5

Ext_wall layer

Gypsum broad 2”

Wall:Concrete block stucco 12”,

exterior insulation and finish

Roof Layer Insulation(R-19), 6” STUD

Floor Construction 0.08 m concrete on ground, Cork cover

Percent Glazing Area 50%

Glazing U-Value U-2.89 W/m^2k

Plant Details HyGSHP

Ground heat exchanger HyGSHP

Borehole hole 98@ 200 ft deep

Borehole spacing 20 ft

U TUBE 1 inch

Ground conductivity 5.22 KJ/hr.m.k [33]

Fill conductivity 4.2 KJ/hr.m.k

HVAC

180 tons unitary heat pump & 70 tons water to water

heat pump

50 tons 100% roof top air conditioner

150 tons cooling tower

Initial Ground water temperature 21 ℃

Total System Airflow Constant air flow

Cooling Setpoint Daytime/nighttime (oC) 23.3

Heating Setpoint - Daytime/Nighttime (oC) 21.1

Air Source Heat Pump (ASHP) ASHP

71

Cooling Setpoint Daytime/nighttime (oC) 23.3

Heating Setpoint - Daytime/Nighttime (oC) 21.1

Internal Loads

Lighting Power Density (W/ft2) 1.0 (assumed)

Lighting Controls specified

Equipment/Plug load Density (W/ft2) 1.1 (assumed)

Occupancy Density Max = 300

Operating Schedules Specified

Lighting equipment schedule See Pictures 1 and 2

Infiltration 1.0

Plant Details GSHP

Ground heat exchanger GSHP

Borehole hole 245@ 200 ft deep

Borehole spacing 20 ft

U TUBE 1 inch

Ground conductivity 4.68 KJ/hr.m.k

Fill conductivity 5.22 KJ/hr.m.k

72

APPENDIX B

LISTING OF 20 TONS WATER TO AIR SOURCE HEAT PUMP COOLING

CAPACITY PERFORMANCE DATA

73

Appendix B provides one sample cooling performance data which is converted

based on the performance file from manufacturing company. 15tons, 20 tons and

25 tons water to air source heat pump performance data is created in order to

serve and simulate the different thermal zone with relative cooling and heating

capacity.

3586.80 3586.80 !Values of Airflow in liters per second (l/s)

1.89 2.84 3.79 !Values of Liquid Flow Rate in liters per second (l/s)

10.00 21.11 32.22 43.33 !Values of Entering Liquid Temperature (degrees C)

78.04482594 52.87002103 9.69

!Total Cooling(kW) Sensible Cooling(kW) and Power(kW) at 3586.80/1.89/10

73.32638171 50.11515297 10.94

!Total Cooling(kW) Sensible Cooling(kW) and Power(kW) at 3586.80/1.89/21.11

63.68434351 47.94642705 12.36


55.97657437 43.66758943 13.57


78.60166097 53.39754895 9.39

!Total Cooling(kW) Sensible Cooling(kW) and Power(kW) at 3586.80/ 2.84/10

73.97113807 50.84783065 10.65

!Total Cooling(kW) Sensible Cooling(kW) and Power(kW) at 3586.80/ 2.84/21.11

65.06177754 48.67910473 12.12


74

57.47123683 44.95710214 13.7


79.1291889 53.92507688 9.08


74.64520153 51.55120121 10.35


65.99960496 49.93931033 11.81


58.46767847 45.92423667 13.86



73.32638171 50.11515297 10.94


63.68434351 47.94642705 12.36


55.97657437 43.66758943 13.57


78.60166097 53.39754895 9.39

!Total Cooling(kW) Sensible Cooling(kW) and Power(kW) at 3586.80/ 2.84/10

73.97113807 50.84783065 10.65


65.06177754 48.67910473 12.12

75


57.47123683 44.95710214 13.7


79.1291889 53.92507688 9.08


74.64520153 51.55120121 10.35


65.99960496 49.93931033 11.81


58.46767847 45.92423667 13.86


76

APPENDIX C

LISTING OF 20 TONS WATER TO AIR HEAT PUMP HEATING CAPACITY

PERFORMANCE DATA

77

3586.80 3586.80

!Values of Airflow in liters per second (l/s)

1.89 2.84 3.79

!Values of Liquid Flow Rate in liters per second (l/s)

-1.11 10.00 21.11 32.22

! Values of Entering Liquid Temperature in Degrees Celsius

49.8220819 10.7

!Total Heating(kW) and Power(kW) at 3586.80/1.89/-1.11

63.03958716 11.51

!Total Heating(kW) and Power(kW) at 3586.80/1.89/10

79.15849601 12.34

!Total Heating(kW) and Power(kW) at 3586.80/1.89/21.11

99.58554959 13.22


52.43041442 10.81


65.76514811 11.64


82.70465595 12.55

!Total Heating(kW) and Power(kW) at

3586.80/2.84/21.11104.2160725 13.53


78

56.26964544 10.93

!Total Heating(kW) and Power(kW) at 3586.80/3.79 /-1.11

68.49070906 11.78

!Total Heating(kW) and Power(kW) at 3586.80/3.79 /10

86.2508159 12.77

!Total Heating(kW) and Power(kW) at 3586.80/3.79 /21.11

105.5055852 13.68


49.8220819 10.7


63.03958716 11.51


79.15849601 12.34


99.58554959 13.22


52.43041442 10.81


65.76514811 11.64


82.70465595 12.55


79

104.2160725 13.53


56.26964544 10.93

!Total Heating(kW) and Power(kW) at 3586.80/3.79 /-1.11

68.49070906 11.78

!Total Heating(kW) and Power(kW) at 3586.80/3.79 /10

86.2508159 12.77


105.5055852 13.68


80

APPENDIX D

LISTING OF 20 TONS WATER TO AIR HEAT PUMP COOLING CAPACITY

CORRECTION PERFORMANCE DATA

81

15.56 18.33 21.11 26.67 32.22 37.78 !Values of Entering Air Dry-Bulb

Temperature (C)

12.78 15.56 18.33 19.44 21.11 23.89 !Values of Entering Air Wet Bulb

Temperature (C)

0.898 0.723 0.985

!Multipliers for Total Capacity, Sensible Capacity and Power at 15.56/12.78

0.912 0.529 0.994


0.967 0.5 0.997


1 0.413 1 !Multipliers for Total Capacity, Sensible Capacity and Power at

15.56/19.44

1.053 0.35 1.003


1.168 0.3 1.007


0.898 0.866 0.985


0.912 0.632 0.994


0.967 0.59 0.997


82

1 0.5 1


1.053 0.45 1.003


1.168 0.4 1.007


0.898 1.048 0.985


0.912 0.88 0.994


0.967 0.694 0.997


1 0.616 1


1.053 0.577 1.003


1.168 0.538 1.007


0.898 1.3 0.985


0.912 1.244 0.994


83

0.967 1.079 0.997


1 1 1


1.053 0.879 1.003


1.168 0.687 1.007


0.898 1.65 0.985


0.912 1.57 0.994


0.967 1.49 0.997


1 1.33 1


1.053 1.25 1.003


1.168 1.04 1.007


0.898 1.74 0.985


84

0.912 1.696 0.994


0.967 1.652 0.997


1 1.564 1


1.053 1.52 1.003


1.168 1.476 1.007


85

APPENDIX E

LISTING OF 20 TONS WATER TO AIR HEAT PUMP HEATING CAPACITY

CORRECTION PERFORMANCE DATA

86

7.22 10 12.78 15.56 18.33 20 21.11 23.89 26.67

! Values of Entering Air Dry-Bulb Temperature (C)

1.062 0.739

! Multipliers for Heating Capacity and Power at 7.22

1.05 0.79

! Multipliers for Heating Capacity and Power at 10

1.037 0.842


1.025 0.893


1.012 0.945


1.005 0.976

! Multipliers for Heating Capacity and Power at 20

1 1 ! Multipliers for Heating Capacity and Power at 21.11

0.987 1.048


0.975 1.099

87

APPENDIX F

LISTING OF 20 TONS AIR SOURCE HEAT PUMP COOLING CAPACITY

PERFORMANCE DATA

88

2831 3775 4719 !Air flow rates in liters per second (l/s)

14.44 19.44 23.89 24.22 !Return air wet bulb temperatures (C)

23.89 26.67 29.44 !Return air dry bulb temperatures (C)

29.44 40.56 46.11 !Outdoor air dry bulb temperatures (C)

62.45344502 56.9437089 21

!Total Cooling(kW), Sensible Cooling(kW) and Power(kW) at 2831\14.44\23.89\29.44

54.15953374 52.45972153 21

!Total Cooling(kW), Sensible Cooling(kW), and Power(kW) at 2831\14.44\23.89\40.56

49.70485347 49.70485347 21


63.6550364 63.6550364 21


57.38331551 57.38331551 21


53.51477738 53.51477738 21


67.02535371 67.02535371 21


61.07601099 61.07601099 21


57.32470129 57.32470129 21


73.70737411 40.29727213 21

89


66.05821918 37.36656143 21


61.19323942 35.49090658 21


73.59014568 49.26524687 21


65.85306943 46.33453617 21


61.01739677 44.51749553 21


73.44361014 58.14530029 21


65.64791968 55.15597537 21


60.78293992 53.30962763 21


80.30147318 30.5673126 21


72.74023957 27.87105876 21


68.05110245 26.25916787 21


80.24285897 39.59390156 21

90


72.50578272 36.89764771 21


67.78733849 35.31506394 21


80.15493765 48.53256919 21


72.27132586 45.89492956 21


67.55288164 44.34165289 21


85.86982351 26.08332523 21


78.24997569 20.22190383 21


73.56083857 18.75654848 21


85.8405164 31.68098267 21


78.04482594 29.18987857 21


73.44361014 27.72452322 21


85.63536665 40.6196503 21

91


77.83967619 38.21646753 21


73.20915329 36.78041929 21


68.02179535 66.67366843 21


60.63640438 60.63640438 21


56.29895255 56.29895255 21


71.39211265 71.39211265 21


64.85662779 64.85662779 21


60.60709728 60.60709728 21


75.05550103 75.05550103 21


68.72516592 68.72516592 21


64.82732068 64.82732068 21


79.18780311 46.18800063 21

92


70.95250605 43.16936861 21


65.79445522 41.32302087 21


78.92403915 57.7643079 21


70.6301278 54.8629043 21


65.50138415 53.04586367 21


78.63096808 69.04754409 21


70.42497812 66.02891207 21


65.38415572 63.18612269 21


86.19220169 33.64455884 21


77.92759751 30.88969078 21


72.94538932 29.21918568 21


85.89913062 45.30878742 21

93


77.57591223 42.67114779 21


72.56439693 41.05925691 21


85.63536665 56.82648047 21


77.31214827 54.36468349 21


72.27132586 52.81140681 21


92.02431598 24.91104095 21


83.23218388 20.5149749 21


78.24997569 17.5842642 21


91.76055202 35.22714261 21


83.17356967 32.6481172 21


78.16205437 31.12414763 21


91.52609516 46.77414277 21

94


82.8804986 44.40026711 21


77.78106198 42.96421886 21


72.0075619 72.0075619 21


64.41702119 64.41702119 21


59.69857696 59.69857696 21


76.13986399 76.13986399 21


68.95962277 68.95962277 21


64.41702119 64.41702119 21


80.27216607 80.27216607 21


73.41430304 73.41430304 21


69.31130806 69.31130806 21


82.29435646 50.75990932 21

95


73.23846039 47.65335598 21


67.8166456 45.83631535 21


81.94267117 65.00316333 21


72.857468 61.9552242 21


67.34773189 59.99164803 21


78.04482594 78.04482594 21


73.56083857 73.47291725 21


69.54576491 69.54576491 21


89.79697585 35.52021368 21


80.88761532 32.67742431 21


75.46580053 30.9776121 21


89.38667635 49.85138901 21

96


80.3893945 47.18444227 21


75.02619392 45.54324428 21


80.53593004 73.91252385 21


80.00840211 61.5449247 21


74.61589442 59.93303382 21


95.83423989 20.5149749 21


86.74903672 17.5842642 21


81.47375746 14.6535535 21


95.59978303 37.57171117 21

97

APPENDIX G

LISTING OF 20 TONS AIR SOURCE HEAT PUMP COOLING CAPACITY

PERFORMANCE DATA

98

2830 3775 4715.89 !Air Flow Rate in liters per second (l/s)

12.78 21.11 26.67 !Indoor Dry Bulb Temperatures (C)

-23.33 -17.78 -12.22 -8.33 -1.11 4.44 8.33 10 26.67

!Outdoor Dry Bulb Temperatures (C)

23.73875667 20.5

!Heating Capacity(kW) and Power(kW) at 424.75/12.78 /-23.33

29.60017807 22

!Heating Capacity(kW) and Power(kW) at 424.75/12.78 / -17.78

35.75467054 23.5


40.00420106 25


47.18444227 26.5


62.42413791 28

!Heating Capacity(kW) and Power(kW) at 424.75/12.78 /4.44

69.01823699 29.5


71.65587662 31

!Heating Capacity(kW) and Power(kW) at 424.75/12.78 /10

81.03415086 32.5

!Heating Capacity(kW) and Power(kW) at 424.75/12.78 / 15.56

99

21.39418811 20.5

!Heating Capacity(kW) and Power(kW) at424.75/21.11/-23.33

27.40214505 22

!Heating Capacity(kW) and Power(kW) at 424.75/21.11/ -17.78

33.55663752 23.5


37.80616803 25

!Heating Capacity(kW) and Power(kW) at 424.75/21.11/-8.33

44.83987371 26.5


59.34689168 28

!Heating Capacity(kW) and Power(kW) at 424.75/21.11/4.44

65.50138415 29.5

!Heating Capacity(kW) and Power(kW) at 424.75/21.11/8.33

68.43209485 31

!Heating Capacity(kW) and Power(kW) at 424.75/21.11/10

77.66383355 32.5

!Heating Capacity(kW) and Power(kW) at 424.75/21.11/ 15.56

19.19615509 20.5

!Heating Capacity(kW) and Power(kW) at424.75/26.67 /-23.33

25.35064756 22


100

31.65167556 23.5


36.04774161 25


43.08144729 26.5


57.14885865 28


63.30335112 29.5


66.08752629 31

!Heating Capacity(kW) and Power(kW) at 424.75/26.67 /10

75.31926499 32.5

!Heating Capacity(kW) and Power(kW) at 424.75/26.67 / 15.56

23.73875667 20.5

!Heating Capacity(kW) and Power(kW) at3775/12.78 /-23.33

29.74671361 22

!Heating Capacity(kW) and Power(kW) at 3775/12.78 / -17.78

35.90120608 23.5


40.29727213 25

!Heating Capacity(kW) and Power(kW) at 3775/12.78 /-8.33

101

47.91711995 26.5


63.74295773 28

!Heating Capacity(kW) and Power(kW) at 3775/12.78 /4.44

70.19052127 29.5


72.97469643 31

!Heating Capacity(kW) and Power(kW) at 3775/12.78 /10

82.20643514 32.5

!Heating Capacity(kW) and Power(kW) at 3775/12.78 / 15.56

21.54072365 20.5

!Heating Capacity(kW) and Power(kW) at3775/21.11/-23.33

27.69521612 22

!Heating Capacity(kW) and Power(kW) at 3775/21.11/ -17.78

33.99624412 23.5


38.24577464 25

!Heating Capacity(kW) and Power(kW) at 3775/21.11/-8.33

45.71908692 26.5


60.51917596 28

!Heating Capacity(kW) and Power(kW) at 3775/21.11/4.44

102

67.11327503 29.5

!Heating Capacity(kW) and Power(kW) at 3775/21.11/8.33

70.04398573 31

!Heating Capacity(kW) and Power(kW) at 3775/21.11/10

78.98265337 32.5

!Heating Capacity(kW) and Power(kW) at 3775/21.11/ 15.56

19.48922616 20.5

!Heating Capacity(kW) and Power(kW) at3775/26.67 /-23.33

25.79025416 22


32.2378177 23.5


36.63388375 25

!Heating Capacity(kW) and Power(kW) at 3775/26.67 /-8.33

43.9606605 26.5


58.32114293 28


64.76870647 29.5


67.55288164 31

!Heating Capacity(kW) and Power(kW) at 3775/26.67 /10

103

76.78462034 32.5

!Heating Capacity(kW) and Power(kW) at 3775/26.67 / 15.56

25.05757649 20.5

!Heating Capacity(kW) and Power(kW) at4715.89 /12.78 /-23.33

31.21206896 22

!Heating Capacity(kW) and Power(kW) at 4715.89 /12.78 / -17.78

37.36656143 23.5


41.90916301 25

!Heating Capacity(kW) and Power(kW) at 4715.89 /12.78 /-8.33

49.67554637 26.5


65.79445522 28

!Heating Capacity(kW) and Power(kW) at 4715.89 /12.78 /4.44

71.94894769 29.5


74.58658732 31

!Heating Capacity(kW) and Power(kW) at 4715.89 /12.78 /10

83.67179049 32.5

!Heating Capacity(kW) and Power(kW) at 4715.89 /12.78 / 15.56

23.006079 20.5

!Heating Capacity(kW) and Power(kW) at4715.89 /21.11/-23.33

104

29.307107 22

!Heating Capacity(kW) and Power(kW) at 4715.89 /21.11/ -17.78

35.60813501 23.5


40.00420106 25

!Heating Capacity(kW) and Power(kW) at 4715.89 /21.11/-8.33

47.47751334 26.5


62.86374452 28

!Heating Capacity(kW) and Power(kW) at 4715.89 /21.11/4.44

69.31130806 29.5

!Heating Capacity(kW) and Power(kW) at 4715.89 /21.11/8.33

71.94894769 31

!Heating Capacity(kW) and Power(kW) at 4715.89 /21.11/10

80.88761532 32.5

!Heating Capacity(kW) and Power(kW) at 4715.89 /21.11/ 15.56

20.95458151 20.5

!Heating Capacity(kW) and Power(kW) at4715.89 /26.67 /-23.33

27.40214505 22


33.84970859 23.5


105

38.24577464 25

!Heating Capacity(kW) and Power(kW) at 4715.89 /26.67 /-8.33

45.71908692 26.5


60.66571149 28


67.25981057 29.5


70.04398573 31

!Heating Capacity(kW) and Power(kW) at 4715.89 /26.67 /10

78.83611783 32.5

!Heating Capacity(kW) and Power(kW) at 4715.89 /26.67 / 15.56

106

APPENDIX H

LISTING OF INDOOR WATER SOURCE HEAT PUMPS IN EACH THERMAL

ZONE

107

Heat pump model

1st floor left (Btu/h)

1st floor right (Btu/h)

2nd floor left

(Btu/h)

2nd floor right

(Btu/h)

3rd floor left

(Btu/h)

3rd floor right

(Btu/h)

4th floor left (Btu/h)

4th floor right

(Btu/h)

5th floor left(Btu/h)

K-1 38400 64000 38400 64000 38400 64000 51200 64000 K-2 31400 31400 31400 15700 15700 DD-1 76800 115200 102400 115200 102400 102400 89600 102400 DD-2

15700 15700 15700 K-ADA

12800 12800 15500 12800 DD-ADA

12800 12800 12800 2B

29800 29800 HPU1-1 24800 HPU1-2 24800 HPU1-3

24800 HPU1-4 29200 HPU1-5

29200 HPU1-6

29200 HPU1-7

29200 HPU1-8

34000 HPU1-9 41400 HPU1-10

65600 HPU1-11

65600 HPU2-1

15700 HPU2-2

18200 HPU2-3

24800 HPU3-1

15700 HPU3-2

18200 HPU3-3

24800 HPU4-1

15700 HPU4-2

18200 HPU4-3

24800 HPU5-1

18200 HPU5-2

24800 Total 266800 277600 266400 185000 266400 185000 270400 185000 267700

108

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