Optimization of Pumping Systems in HVAC

8/2/2019 Optimization of Pumping Systems in HVAC

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B. Srinivasa RajkumarSales Manager (HVAC)

Commercial Building ServicesGrundfos India

Optimization of Pumping System in HVAC

ACREX 2012


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All system operated as variable flow systemPrimary variable pumping

Use of thermal storageCombination of active and passive systemsUse of tertiary pumps (zone dividing)

Challenges in condenser water pumpingRemote monitoring of pumping systems

HVAC pumping schemes


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All system operated as variable flow system

Constant flow system:Constant flow systems will use three way val-

ves and will give a variable flow in distribution

net and variable flow in the load.

Variable flow system:Variable flow systems will use two way valvesand give a variable flow in both the load and inthe distribution net.

By using Tertiary pumps the flow in load canbe held constant but with a variabletemperature.

MAB A

B

Variable flowConstant temperature

Constant flowVariable temperature Load

M

Constnt flowVariable temperature

Variable flowConstant temperature Load

M

Constnt flowVariable temperature

Variable flowConstant temperature Load


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The way to - Primary variable flow

Improvedperformance

Chiller

Chiller

Chiller

Load

Load

Load

Load

Load

Load

Load

Load

Load

Constant flowThree way valvesConstant speed pumps

Chiller

Chiller

Chiller

Load

Load

Load

Load

Load

Load

Load

Load

Load

Commonpipe

Constant flow (primary)

Variable flow (secondary)Two way valvesConstant/variable speed pumps

Chiller

Chiller

Chiller

Load

Load

Load

Load

Load

Load

Load

Load

LoadBuffer tank

Constant flow (primary)Variable flow (secondary)Two way valvesConstant/variable speed pumps

Chiller

Chiller

Chiller

Load

Load

Load

Load

Load

Load

Load

Load

Load

Variable flowTwo way valvesVariable speed pumps


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Primary variable flow

Also the using primary variable flow has been discussion inleading technical magazines like The ASHRAE Journal.The conclusion often end up in favour of:Primary variable flow


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Advantages:Lower first costLess space required (less pumps)Reduced pump power designLower energy consumption

Between a flow at50% to 80% we havethe highest numberof operation hours,and here the saving

is significant.


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Primary/tertiary dedicated pumps:

If there is a demand for standby pumps

there has to be installed one standby per

chiller. The pump controller has to be

able

take out the pump of control sequence

when the chiller is switches off.Primary/tertiary common pumps:

There is a demand for control valves on

each chiller to be able to control the flow

in the chiller, and there is only demand

for one standby pump for all the chillers.

Load

Load

Load

Load

Load

Load

Load

Load

Load

Chiller

Chiller

Chiller

Load

Load

Load

Load

Load

Load

Load

Load

Load

Chiller

Chiller

Chiller

For both system types there is a demand for controlled bypass tosecure the minimum flow.


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Use of thermal storage tanks

Chillerplant

Charge mode flow Discharge mode flow

Stage storage tank

Distribution net

Basis thermal storage tank principal

Reduced refrigeration equipment investmentLess expensive than chiller capacity in large systemsLess inefficient part-load operation of plantCapacity for emergencies and growth


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Capacityhandle bychillers

Capacityhandle by

chillers andstorage

Load

24 hours

Use of thermal storage tanks

Use of thermal storage provide a good opportunities tocover the peak load instead of installing more capacity, alsoin situation where the system is expanded.


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Combination of active and passive systems

To reduce the size of the air part (ducts and AHUs) passive systems areoften used it could be cooling ceilings or cooling floors. The passivesystem also has an advantage in operating with a higher flowtemperature (15-17oC) which fit with alternative cooling sources andmake it possible to operate with a higher system Dt.The big challenge is to avoid condensation on floors and ceilings.

M

M

M

15oC

18oCCooling Ceiling/floors as apart of the building

construction


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Typical buildings where passive system can be use arebuildings with large public areas like:

Air portsHotel receptions

MuseumsOpera housesetc.

Passive systems always has to combined with chilled airsystem to provide fresh air.

Combination of active and passive systems


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Use of tertiary pumps

Chiller

Chiller

Chiller

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Chiller

Chiller

Chiller

De-coupling

Load

Load

Load

Load

Load

Load

Load

Load

Load

De-couplingChiller

Chiller

Chiller

No matter if the system design is a Primary variable flow or Primarysecondary flow tertiary can be used larger systems. The mainpurpose is to increase the hydraulic balancing and to lower the headof the Primary/Secondary pumps and there by reduce the operationcost.The system will be much more flexible easier to make changes.

Load

Load

Load

Load

Load

Load

Load

Load

Load

Chiller

Chiller

Chiller


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Indirect connection

with flowtemperature control,

and and heatexchanger

Indirect connection

with flowtemperature control,and by-pass control

Indirect connectionwith flow

temperature control

Connection with

booster pumpand high pressure

bypass

Connection withbooster pump

Connection withcontrol valve

Direct connection

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

Load

The tertiary system/pumps can be connected to thedistribution net in different ways depending on the individualconditions.

Use of tertiary pumps


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Potential Challenges in Condensers Circuit

Condensers circuit are Primarily a much easier to manage. However,troubles still persist occasionally in some system. Lets have a brief look

at

some of the potential challenges:

1. Pump Cavitations due to insufficient inlet pressure

2. Air entering pumps due to the formation of vortex at collection basinor incorrect setting of bypass

3. Over sizing of pump due to over estimation of frictional losses in thecircuit

4. Fouling of pipes and condenser tube

5. Changes in operating condition for circuit with bypass line


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Closed Loop and Open Loop system

In a large chilled water system consists two difference kind of circuit

Closed loop system- Distribution circuit

Closed systems are characterized as systems with pumps that onlyhave to overcome the sum of friction losses, which are generated by

all the components Open loop system- Heat rejection circuit

Open systems are systems, where the pump is used to transportliquid from one point to another

Thing to note between these two type of circuit while sizing the pump is

Static head consideration.


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System Curve for Closed/ Open Loop system

Closed Loop system Open Loop system


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Typical Heat Rejection Circuit

Chiller

Condenser Pump

Cooling Tower


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Points to note to avoid cavitations on Condenserpump

Condenser side is an open loop system, the only positive pressure to the

pump suction are the elevation of cooling tower and atmospheric

pressure, therefore, here are a few notes;-

Always locate the condenser pumps as close as possible to the tower

Design the pumps below As much as possible below the collection basinwater level

Locate the condenser pumps before Condenser to avoid large pressuredrop of this component

Ensure sufficient NPSHA.

Avoid using high pressure drop strainer, check Valve and balancing Valveat pump suction line

(If strainer has to be installed, try to use large mesh opening up to 3/16 atthe suction, propose is just to protect the pump and install a fine meshstrainer at the pump discharge to protect all other equipments)

Avoid Overhead suction piping


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Vortex at Collection basin Exit

Vortex at Collection basin iscreated when, there is insufficientwater level above the collectionbasin exit for the velocity that thewater is exiting.

Facts contributing to the vortexing:-1. Sudden decrease in exit pipe

size (Suction line) causes thewater velocities above themaximum allowable limit,vortex created

2. Over sizing of pumps due toover estimation of frictionallosses

3. In correct setting of bypassline (If any)


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Points to note to avoid formation of Vortex

Cooling Tower exit pipe follows collection basin exit at least for thelength of 10x the diameter before reducing it to the pump suctionsize

Throttle valve to control flow (energy consideration)

Modifying impeller diameter

Speed control


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Remote monitoring of pumping systems

Why to own when you can rent theservices ?

World is moving towards cloudcomputing. So does the buildingservices

No hassles of maintaining a localnetwork

All devices talk to each other and to acentral network

Nominal charges for web servicemaintenance to the use


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Remote monitoring of pumpingsystems

Easy-to-install, low-cost monitoring andmanagement of pumping systems.

Web access to reports and trend data for all relevantemployees.

Automatic event log and service log for all pumpsin the system.

Plug n

Play integration with Controls

monitoring of all pumps and sensors.

Centrally hosted database andapplication server.Users only need an Internet PC.

Alarms on SMS and Email distributed according tobuilt-in week schedule.


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Cloud Overview

Pump LogicControllers

Data logger

Internet

GSM

Central Web Server

Users

Users


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Online monitoring of pumpingsystem efficiency

Close monitoring of specificenergy consumption

Immediate course correction inevent of any performancedegradation

Get access to data andperform basic functions suchas acknowledge alarms,start/stop pumps, reset

controllers from your mobilephone / PDA

Business model could coverAMC or 24/7 operation supportto benefit users

Remote monitoring of pumping systems Userbenefits


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Focus on energy saving (Carbon footprint)

Energy saving:To reduce operation costTo reduce CO2 emissionUtilizing energy sources better

The use of Life Cycle Cost more and more common


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How to evaluate the most efficient pump solution

The best way to evaluate theefficiency of a pump system is touse:Life Cycle Cost Analysis (LCC)LCC shows the total life time cost of

a pump system.The lifetime of a quality pumpsystem will be no less than 20years.When used as a comparison toolbetween possible design oroverhaul alternatives, the LCCprocess will show the most cost-effective solution within the limits ofavailable data.


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The LCC equation

Normally only 3 elements in theequation will add value whencalculating HVAC systems inCommercial Buildings :

Initial costMaintenance costEnergy cost


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B. Srinivasa Rajkumar

Manager Sales (HVAC)

Commercial Building Services

Grundfos Pumps India

Direct: (+91) 44 4596 6891Mobile: (+91) 99406 79196

Mail: [email protected]

Optimization of Pumping Systems in HVAC

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