Heating and Cooling Load Calculations-Report

HEATING AND COOLING LOAD CALCULATIONS

COMPOSITE MATERIALS LABORATORY, DEPARTMENT OF MECHANICAL ENGINEERING, COLLEGE OF E&ME, NUST

NS ASAD UR REHMAN | NS BASIT YAQOOB | NS EHTISHAM TANVIR | NS FOUZAN ABDULLAH MECHANICAL ENGINEERING

DE-33-B

MAY 23, 2014

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ABSTRACT

This report encompasses the detailed calculations, keeping in mind the ASHRAE standards,

of overall heating and cooling load calculations for Composite Materials Laboratory in

Department of Mechanical Engineering, College of E&ME, NUST. With thoroughly

researched design considerations, it has been calculated that the heating load of the room is

1.11 tons and the cooling load of the room is 1.6 tons.

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Table of Contents

INTRODUCTION: .................................................................................................................................................................. 3

IMPORTANT DEFINITIONS: .............................................................................................................................................. 3

Cooling Load: ....................................................................................................................................................................... 3

Heating Load: ....................................................................................................................................................................... 3

Thermal Resistance: .............................................................................................................................................................. 3

Overall Heat Transfer Coefficient: ........................................................................................................................................ 3

Infiltration: ............................................................................................................................................................................ 3

Sensible Heat Loss: ............................................................................................................................................................... 3

Latent Heat Loss: .................................................................................................................................................................. 3

Relative Humidity: ................................................................................................................................................................ 3

Humidity Ratio: .................................................................................................................................................................... 4

Cooling Load Factor (CLF): ................................................................................................................................................. 4

REFERENCE VALUES: ........................................................................................................................................................ 4

Thermal Resistances: ............................................................................................................................................................ 4

Overall Heat Transfer Coefficients: ...................................................................................................................................... 4

IMPORTANT EQUATIONS: ................................................................................................................................................ 4

DESIGN CONDITIONS: ........................................................................................................................................................ 5

WINTER: .............................................................................................................................................................................. 5

SUMMER: ............................................................................................................................................................................ 5

COMPOSITE MATERIALS LABORATORY LAYOUT (SOLIDWORKS MODEL) .................................................... 6

HEATING LOAD CALCULATIONS ................................................................................................................................... 8

CALCULATIONS FOR NORTH-FACING WALL: ........................................................................................................... 8

CALCULATIONS FOR ROOF WITH SUSPENDED CEILING: ....................................................................................... 9

CALCULATIONS FOR WEST-FACING WALL: ............................................................................................................ 10

CALCULATIONS FOR EAST-FACING WALL: ............................................................................................................. 11

CALCULATIONS FOR SOUTH-FACING WALL: .......................................................................................................... 11

TOTAL HEATING LOAD FOR THE LABORATORY: .................................................................................................. 12

COOLING LOAD CALCULATIONS ................................................................................................................................. 13

CALCULATIONS FOR NORTH-FACING WALL: ......................................................................................................... 13

CALCULATIONS FOR ROOF WITH SUSPENDED CEILING: ..................................................................................... 14

CALCULATIONS FOR WEST-FACING WALL: ............................................................................................................ 15

CALCULATIONS FOR EAST-FACING WALL: ............................................................................................................. 16

CALCULATIONS FOR SOUTH-FACING WALL: .......................................................................................................... 16

CALCULATIONS FOR LIGHTING: ................................................................................................................................ 17

CALCULATIONS FOR EQUIPMENT: ............................................................................................................................ 17

CALCULATIONS FOR PEOPLE (Moderately active office work): ................................................................................. 17

TOTAL COOLING LOAD FOR THE LABORATORY: ................................................................................................. 18

REFERENCES: ..................................................................................................................................................................... 19

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INTRODUCTION: This procedure to calculate the heating and cooling load of the room specified, is a mixture of

analytical and practical aspects. In these calculations, ASHRAE standards and practical

measurements of the room were taken precisely to calculate the exact amount of the said

loads in order to determine the tonnage of the heaters and air conditioners for the room and

hence the heating and cooling costs of the entire room.

IMPORTANT DEFINITIONS: Important terminologies and their definitions are given below:

Cooling Load:

The amount of heat that must be removed to keep temperature and humidity of the air

maintained at a comfortable level during summer season is called the cooling load.

Units: BTU/hr, tonnes

Heating Load:

The amount of heat that must be added to keep temperature and humidity of the air

maintained at a comfortable level in winter season is called the cooling load.

Units: BTU/hr, tonnes

Thermal Resistance:

The thermal resistance R of a material is its ability to resist the flow of heat through it.

Units: hr-ft2-F/BTU

Overall Heat Transfer Coefficient:

Overall Heat Transfer Coefficient is the reciprocal of the thermal resistance.

Units: BTU/hr-ft2-F

Infiltration:

Infiltration occurs when outdoor air enters through building openings, due to wind

pressure. Openings of most concern are cracks around windows, doors, edges and open

doors.

Sensible Heat Loss:

Sensible heat loss is heat lost by a body or thermodynamic system that reduces the

temperature, and some macroscopic variables of the body, but leaves unchanged certain other

macroscopic variables, such as volume or pressure.

Latent Heat Loss:

Latent heat loss is the energy released by a body or a thermodynamic system during a

constant-temperature process.

Relative Humidity:

The amount of water vapour present in air expressed as a percentage of the amount needed

for saturation at the same temperature.

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Humidity Ratio:

The ratio of the mass of the water vapour to the mass of dry air contained in the sample.

Cooling Load Factor (CLF):

The cooling load factor CLF accounts for the storage of part of the solar heat gain.

REFERENCE VALUES: The following tables contains all the reference values used in the calculation for heating and

cooling loads:

Thermal Resistances:

Common brick 0.2 hr-ft2-F/BTU /in

Plaster material 0.2 hr-ft2-F/BTU /in

Air film (still air) 0.68 hr-ft2-F/BTU

Air film (moving air in winter) 0.17 hr-ft2-F/BTU

Air film (moving air in summer) 0.25 hr-ft2-F/BTU

Concrete block 0.241 hr-ft2-F/BTU /in Table 1

Overall Heat Transfer Coefficients:

Door 0.49 BTU/hr-ft2-F

Window 1.10 BTU/hr-ft2-F Table 2

IMPORTANT EQUATIONS: =

= 1.1

= 0.68 ( )

= 1 + 2 + 3 +

=

= (For people)

= (For people)

= 3.4 (For lighting)

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DESIGN CONDITIONS: We have considered the following design conditions:

Room Location: 33.6000 N, 73.0333 E

WINTER:

Outside temperature 2.7C (36.9F) Desirable room temperature 25C (77F) Indoor temperature 13.85C (56.95F) Relative Humidity 66%

Month January

SUMMER:

Outside temperature 46.6C (116F) Desirable room temperature 25C (77F) Indoor Temperature 35.8C (96.5F) Relative Humidity 46%

Month June

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COMPOSITE MATERIALS LABORATORY LAYOUT

(SOLIDWORKS MODEL)

Figure 1: SIDE VIEW

Figure 2: BACK VIEW

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Figure 3: FRONT VIEW

Figure 4: ISOMETRIC VIEW

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HEATING LOAD CALCULATIONS

CALCULATIONS FOR NORTH-FACING WALL:

A. Brick wall and plaster material

Area of wall with window: 13566.875 in2

Area of window: 4719 in2

Area of wall without window= 8847.875 in2 = 61.4435 ft2

Thickness of wall= 10.25

Thickness of Bricks=8.75

Thickness of plaster material= 1.5

Thermal resistance for bricks for specified thickness= 1.75 hr-ft2-F/BTU

Thermal resistance for plaster material for specified thickness= 0.3 hr-ft2-F/BTU

Thermal resistance for inside air film= 0.68 hr-ft2-F/BTU

Thermal resistance for outside air film= 0.17 hr-ft2-F/BTU

Total thermal resistance = 2.9 hr-ft2-F/BTU

Heating Load for wall = 849.49 BTU/hr

B. Beams and plaster material

Area of left hand beam = 5236.875 in2

Thickness of left hand beam = 19.75

Thickness of concrete = 18.75

Thickness of plaster material = 1

Thermal resistance of concrete block of specified thickness = 4.51875 hr-ft2-F/BTU

Thermal resistance of plaster material of specified thickness = 0.2 hr-ft2-F/BTU




Heating load for left hand beam= 289.9832 BTU/hr

Area of right hand beam = 1.701 ft2

Thickness of right hand beam = 18.5



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Heating load for right hand beam = 12.8941 BTU/hr

C. Window

Area of window = 32.77 ft2

Overall heat transfer coefficient for window of specified area = 1.10 BTU/hr-ft2-F

Heating load for window = 1445.485 BTU/hr

D. Infiltration Losses

i. Sensible Heat Loss:

Crack length for window = 36.25 ft

CFM value of window for specified crack length = 13.4125 ft3/min

Sensible heat loss through infiltration = 591.62 BTU/hr

ii. Latent Heat Loss:

Through psychrometric charts we have calculated the following vales of humidity

ratios with relative humidity 66% for inside and outside:

Wi=92 gr W/lb

Wo=22 gr W/lb

Latest heat losses = 638.435 BTU/hr

Total heating load for the wall = 3827.9 BTU/hr

CALCULATIONS FOR ROOF WITH SUSPENDED CEILING:

Area of roof = 338 ft2

Thickness of roof = 13.5

Thickness of concrete = 13

Thickness of plaster material = 0.5

Air-gap between roof and ceiling = 21.5

Thickness of polystyrene ceiling = 0.5

Thermal resistance of concrete for specified thickness = 3.316 hr-ft2-F/BTU

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Thermal resistance of plaster material for specified thickness = 0.1 hr-ft2-F/BTU

Thermal resistance of polystyrene ceiling for specified thickness = 2.5 hr-ft2-F/BTU

Thermal resistance of air-gap = 4.176 hr-ft2-F/BTU

Thermal resistance of air films of roof = 1.36 hr-ft2-F/BTU

Thermal resistance of air films of ceiling = 1.36 hr-ft2-F/BTU

Total thermal resistance for roof = 4.776 hr-ft2-F/BTU

Total thermal resistance for ceiling = 8.036 hr-ft2-F/BTU

Heating load for roof = 1415.41 BTU/hr

Heating load for ceiling = 420.607 BTU/hr

Total heating load for roof with ceiling = 1836.02 BTU/hr

CALCULATIONS FOR WEST-FACING WALL:

A. Brick and plaster material:

Area of wall without plaster = 259.25 ft2

Thickness of wall=10.25



Area of plaster material = 266.267 ft2





Total thermal resistance for wall without beams = 3.41 hr-ft2-F/BTU

Heating Load for plaster material including air films = 1565.59 BTU/hr

B. Beam and plaster material

Area of beam = 7.018 ft2

Thickness of beam = 11.25


Heating load for beam= 51.715 BTU/hr


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CALCULATIONS FOR EAST-FACING WALL:

Total heating load the west-facing wall = 1617.302 BTU/hr

Heating load for the beam of west-facing wall = 51.7185 BTU/hr


CALCULATIONS FOR SOUTH-FACING WALL:

A. Bricks and plaster:

Area of wall = 135.68 ft2

Area of door = 24.62 ft2

Area of beams = 3.4 ft2

Area of wall without door and beams = 107.66 ft2









Heating Load = 634.6 BTU/hr

B. Beams and plaster:

Thermal resistance for concrete material for specified thickness= 1.99 hr-ft2-F/BTU





Heating load = 9.36 BTU/hr

C. Door:

Area of the door = 24.6 ft2

Overall heat transfer coefficient for the door = 0.49 BTU/hr-ft2-F

Heating load for the door = 241.08 BTU/hr

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D. Infiltration heat losses:

i. Sensible heat losses:

Total door area = 24.6 ft2

CFM value for the door = 24.6

Sensible heat loss = 527.67 BTU/hr

ii. Latent heat losses:



Wi=92 gr W/lb

Wo=46 gr W/lb



TOTAL HEATING LOAD FOR THE LABORATORY:

PART OF ROOM HEATING LOAD

Roof with ceiling 1836.02

North-facing wall 3827.9

South-facing wall 2182.21

East-facing wall 1669.02

West-facing wall 1617.302

Total Heating Load 11132.452

Total Heating Load with 20% additional load

(tons) 1.1132452

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COOLING LOAD CALCULATIONS

CALCULATIONS FOR NORTH-FACING WALL:

A. Brick wall and plaster material:

Area of wall with window: 13566.875 in2

Area of window: 4719 in2

Area of wall without window= 8847.875 in2 = 61.4435 ft2









Cooling load for wall = 826.31 BTU/hr

B. Beams and plaster material

Area of left hand beam = 36.37 ft2

Thickness of left hand beam = 19.75








Cooling load for left hand beam= 282.08 BTU/hr

Area of right hand beam = 1.701 ft2

Thickness of right hand beam = 18.5



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Cooling load for right hand beam = 13.2 BTU/hr

C. Window

Area of window = 32.77 ft2

Overall heat transfer coefficient for window of specified area = 1.10 BTU/hr-ft2-F

Cooling load for window = 1405.833 BTU/hr

D. Infiltration Losses

i. Sensible Cooling loss:

Crack length for window = 36.25 ft

CFM value of window for specified crack length = 13.4125 ft3/min

Sensible Cooling loss through infiltration = 575.39 BTU/hr

ii. Latent Cooling loss:



Wi=62 gr W/lb

Wo=210 gr W/lb


Total Cooling Load for North-Facing Wall = 3837.273 BTU/hr

CALCULATIONS FOR ROOF WITH SUSPENDED CEILING:

Area of roof = 338 ft2

Thickness of roof = 13.5

Thickness of concrete = 13

Thickness of plaster material = 0.5

Air-gap between roof and ceiling = 21.5

Temperature of air gap = 86.75 F

Thickness of polystyrene ceiling = 0.5

Thermal resistance of concrete for specified thickness = 3.316 hr-ft2-F/BTU

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Thermal resistance of plaster material for specified thickness = 0.1 hr-ft2-F/BTU

Thermal resistance of polystyrene ceiling for specified thickness = 2.5 hr-ft2-F/BTU

Thermal resistance of air-gap = 4.176 hr-ft2-F/BTU

Thermal resistance of air films of roof = 1.36 hr-ft2-F/BTU

Thermal resistance of air films of ceiling = 1.36 hr-ft2-F/BTU

Total thermal resistance for roof = 4.776 hr-ft2-F/BTU

Total thermal resistance for ceiling = 8.036 hr-ft2-F/BTU

Cooling load for roof = 1380.025 BTU/hr

Cooling load for ceiling = 410.1 BTU/hr

Total cooling load for roof with ceiling = 1790.12 BTU/hr

CALCULATIONS FOR WEST-FACING WALL: A. Bricks:

Area of wall without plaster = 259.25 ft2

Thickness of wall=10.25



Area of plaster material = 266.267 ft2





Total thermal resistance for wall without beams = 3.41 hr-ft2-F/BTU

Cooling load for wall without beams = 1522 BTU/hr

B. Beam and plaster material

Area of beam = 7.018 ft2

Thickness of beam = 11.25


Cooling load for beam= 50.423 BTU/hr

Total cooling load for the wall = 1573.06 BTU/hr

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CALCULATIONS FOR EAST-FACING WALL:

Total cooling load the west-facing wall = 1573.06 BTU/hr

Cooling load for the beam of west-facing wall = 50.423 BTU/hr


CALCULATIONS FOR SOUTH-FACING WALL:

A. Bricks and plaster:

Area of wall = 135.68 ft2

Area of door = 24.62 ft2

Area of beams = 3.4 ft2

Area of wall without door and beams = 107.66 ft2









Cooling load = 615.65 BTU/hr

B. Beams and plaster:

Thermal resistance for concrete material for specified thickness= 1.99 hr-ft2-F/BTU





Cooling load = 9.08 BTU/hr

C. Door:

Area of the door = 24.6 ft2

Overall heat transfer coefficient for the door = 0.49 BTU/hr-ft2-F

Cooling load for the door = 235.053 BTU/hr

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D. Infiltration Cooling losses:

iii. Sensible Cooling losses:

Total door area = 24.6 ft2

CFM value for the door = 24.6

Sensible Cooling loss = 527.67 BTU/hr

iv. Latent Cooling losses:


ratios for inside and outside:

Wi=62 gr W/lb

Wo=136 gr W/lb



CALCULATIONS FOR LIGHTING:

Lighting capacity for the room = 180 W

Type of lighting = Fluorescent lights

Cooling load for lighting = 765 BTU/hr

CALCULATIONS FOR EQUIPMENT:

Heat emitting equipment in room = 1 x Personal Computer + 1 x Photocopier

Heat gain for Photocopier = 2600 BTU/hr

Heat gain for PC = 400 BTU/hr

Total cooling load due to equipment = 3000 BTU/hr

CALCULATIONS FOR PEOPLE (Moderately active office work):

Average number of people in room on design day = 3

Sensible heat gains = 750 BTU/hr

Latent heat gains = 600 BTU/hr

Total cooling load due to people = 1350 BTU/hr

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TOTAL COOLING LOAD FOR THE LABORATORY: PART OF ROOM COOLING LOAD

Roof with ceiling 1790.12

North-facing wall 3837.27

People, lighting and equipment 5115

South-facing wall 2032.47

East-facing wall 1623.483

West-facing wall 1573.06

Total Cooling Load with 20% additional load (tons) 1.5971403

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REFERENCES: Air Conditioning Principles and Systems, Edward G. Pita

Non-residential cooling and heating load calculations, ASHRAE, 1997

http://www.myweather2.com

RICOH Manual for AFICIO 2045e Photocopier

Heating and Cooling Load Calculations-Report

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