Cooling load calculation

1. IMPACT OF ROOM ORIENTATIONS ON COOLING
LOAD CALCULATION: A STUDY ON COMPUTER LAB
PRESENTED BY:
2017334021 DIPONKOR DAS BRINTO
2017334025 MD. SAZID ALAM PATWARY
SUPERVISOR:
DR. ABUL MUKID MOHAMMAD MUKADDES
Professor
Dept. Of IPE
Shahjalal University of Science & Technology, Sylhet

2. Outlines
 Introduction
 Background
 Objectives
 Relevant terminology
 Literature review
 Research Gap
 Methodology
 Results and Discussion
 Conclusion
 References

3. INTRODUCTION
When designing a building to cool in summer and heat in winter, it is
important to calculate the thermal loads so that the equipment and room
orientation can be chosen appropriately.
To maintain human comfort and efficient system performance with the
introduction of refrigerated air conditioning systems in this century, the
cooling load calculation method has to be developed.
Cooling load calculation is used to determine the size or capacity of air
conditioning and refrigeration equipment, which is required to maintain
desired inside conditions during a period of high temperatures.

4. • The CLTD/SCL/CLF method is a one-step, manual cooling load calculation
process. The cooling load corresponding to the first three modes of heat
gain as well as the cooling load from infiltration and ventilation can be
roughly calculated using this method.
• One place to make improvements to energy efficiency is computer labs.
Because they include such a huge number of technological gadgets, these
areas frequently have high energy requirements.
• The orientation of a room can affect the amount of solar radiation that enters
the space, which in turn can impact the amount of cooling required to
maintain a comfortable temperature.
BACKGROUND OF THE STUDY

5. OBJECTIVES
We had three main objectives in our study:
a. To find the best suitable orientation for the Computer Lab room of a non-
residential building.
b. To compare concrete and glass as wall materials representation of cooling
load calculation.
c. To increase energy efficiency.

6. RELEVANT TERMINOLOGY
• Cooling Load Temperature Difference (CLTD) – an equivalent temperature
difference used for calculating the instantaneous external cooling load
across a wall or roof. It is the temperature difference between indoor and
outdoor air with the inclusion of the heating effects of solar radiation.
• Cooling Load Factor (CLF) – the cooling load at a given time compared to
the heat gain from earlier in the day. It is the time lag between the outdoor
and indoor temperature peaks.
• Solar Cooling Load (SCL) – accounts for the variables associated with the
solar heat load.
• Shading coefficient (SC) – is used widely in the evaluation of heat gain
through glass and windows

7. Cont.
• Heating, Ventilation, and Air Conditioning (HVAC) System - it controls indoor
environmental conditions to create a comfortable and healthy indoor environment.
 It consists of heating, ventilation, and air conditioning systems, which work together to achieve
energy efficiency and sustainability goals.
 Heating increases indoor temperature using central heating systems, furnaces, or heat pumps.
 Ventilation supplies and removes air through mechanical and natural systems to maintain indoor air
quality, temperature, and humidity.
 Air conditioning cools and dehumidifies indoor air using central air conditioning systems, ductless
mini-split systems, and portable air conditioners.

8. LITERATURE REVIEW SUMMARY
No. Paper and Authors Objective Finding
1
“The Influence of Building’s Orientation
on the Overall Thermal Performance” by
Aiman Albatayneh et al.
To assess the impact of building
orientation on thermal performance to
find ways to reduce greenhouse gas
emissions by designing energy
efficient buildings.
Larger windows should be in
the southern walls in the
northern hemisphere to
provide the most heat to the
building through the window
2
“The impact of building orientation on
energy performance in new Minia, Egypt”
by Sara Elahadad et al.
To assess the energy performance of a
building with a focus on building
orientation.
North facade is the best
orientation in terms of
energy consumption, while
the south facade represents
the worst orientation and
uses the most energy.
3
“Development of cooling load temperature
differential values for building envelopes in
Thailand” by Somsak Chaiyapinunt et al.
To develop cooling load temperature
differential (CLTD) values for
building envelopes.
With more accurate CLTD
values, cooling load
calculations can be
performed more easily and
effectively.

9. Cont..
No. Paper and Authors Objective Finding
4
“The impact of building orientation
on residential heating and cooling.”
by Brandt Andersson et al.
To investigate the impact of
building orientation on end-use
energy consumption in residential
buildings.
Energy performance can be
improved through methods such as
shading, movable insulation, and
special glass or coatings.
5
“Cooling Load Calculations” by H M
Hashim et al.
Accurately calculating the thermal
loads of buildings to facilitate the
selection of suitable air and air
handling equipment for cooling and
heating.
For complex process of calculating
thermal loads of buildings, the
reliability calculation method is
more important.
6
“Estimation of Cooling Load for a
Computer Laboratory” by Kotingo et
al.
Determining the cooling load of a
non-residential building, such as a
computer laboratory, to improve
energy efficiency, occupant
comfort, indoor air quality, and
building durability
For energy savings and cost
reduction, cooling load estimation is
important.

10. RESEARCH GAP
• Most studies focus on the orientation of the entire building but not on the
room.
• While the orientation of the building is a key factor, the orientation of
individual rooms within the building can also have a significant impact on
the cooling load.
• Studies that investigate the effect of room orientation on cooling load
calculation could also provide guidelines for the design of individual rooms,
such as the placement of windows and other cooling equipment, to reduce
energy consumption and improve indoor comfort.
• Many studies have been performed all over the world on heating and
cooling load calculation but unfortunately, such research has been few and
far between in Bangladesh.

11. METHODOLOGY
Literature review
From the review of
previous literatures,
the research gap of
this study was
obtained.
Data Collection
We consider our
Computer Lab room
as a sample. We took
all kind of necessary
data from there.
Calculation and Result
Microsoft Excel were
used to do all the
calculation.

12. NECESSARY EQUATIONS USED IN CLC
External Cooling Load Estimation
• Roofs, walls, and conduction through glass
q = UA(CLTD)
U = design heat transfer coefficient for roof or wall
A = area of roof, wall, or glass, calculated from building plans
CLTD = cooling load temperature difference, roof, wall, or glass from tables
• Solar load through glass
q = A(SC)(SCL)
SC = shading coefficient
SCL = solar cooling load factor with no interior shade or with shade

13. Cont..
• Cooling load from partitions, ceilings, floors
q = UA(to – trc)
U = design heat transfer coefficient for partition walls and windows
A = area of partition walls and windows calculated from building Plans
to = temperature in adjacent space
trc = inside design temperature (constant) in conditioned space

14. Cont..
Internal Cooling Load Estimation
• People
qs = N(Sensible heat gain)CLF
ql = N(Latent heat gain)
N = the number of people in space, from the best available source.
CLF = cooling load factor, by hour of occupancy
Sensible and latent heat gain from the occupancy table.

15. Cont…
 Lights
qlight = (N)(W)(CLF)(BF)
N = number of lights in space.
BF = Ballast factor, 1.0 for incandescent bulb and 1.2 for fluorescent light
W = watts input from electrical plans or lighting fixture data
CLF = cooling load factor, by hour of occupancy,
 Appliances and equipment
qe = (N)(W)(CLF)
N = number of appliances and equipment in space.
W = watts input from electrical plans
CLF = cooling load factor, by hour of occupancy and room furnishings;

16. Cont..
• Ventilation and Infiltration Air Load Estimation
qsensible = 1.10cfm(To − Ti)
= 1.10cfm*TD
qlatent = 4840cfm*ahrd
cfm = ventilation rate.
To = outside air temperature, °F
Ti = inside air temperature, °F
Ahrd= Average humidity ratio difference

17. Cont..
 Cfm by Air Change Method:
The infiltration rate can be calculated as
cfm = (ACH × V) ∕ 60
Where, cfm= infiltration rate in ft3/min.
V=gross space volume in ft3, and
ACH=air change per hour.

18. AIR CONDITIONING
• An air conditioning system is a technology used to regulate and maintain the
temperature, humidity, and air quality of an indoor space.
• American Society of Heating, Refrigeration and Air conditioning Engineers
(ASHRAE) states: “Human comfort is that condition of mind, which expresses
satisfaction with the thermal environment”.
• Factors for Human Comfort:
- Temperature of the surrounding air (21º C~22º C)
- Humidity of air (50% relative humidity)
- Purity of air
- Motion of air

19. Cont..
• Both "Ton of Refrigeration" and "BTU/hr" are units used to measure the cooling capacity
of an air conditioning system.
• . In terms of cooling capacity, one Ton of Refrigeration is equal to 12,000 BTU/hr (British
Thermal Units per hour).
• BTU/hr (British Thermal Units per hour) is a unit of measurement used to express the
amount of heat that an air conditioning system can remove from space in one hour.

20. SAMPLE EXCEL SPREADSHEET WITH EQUATIONS & LEGENDS
Source Unit Unit Unit Unit
Sensible
Btu/hr
Latent
Btu/hr
Wall … - ft^2 - CLTD - U -
Wall ... - ft^2 - CLTD - U -
Glass … - ft^2 - CLTD - U -
Glass … - ft^2 - SCL - - SC -
Glass … - ft^2 - CLTD - U -
Glass … - ft^2 - SCL - SC -
Floor Area - ft^2 - TD - U -
Roof - ft^2 - CLTD - U -
Infiltration - cfm - TD - AHRD - -
Occupants - Persons - Btu-hr/watt - Btu-hr/watt - CLF - -
Lighting - W - BF - CLF -
Computer - W - Btu-hr/watt -
- -
TD= Temperature difference betweenoutside and
inside air
AHRD = Air Humidity ratio difference betweenoutside
andinside air
cfm = Infiltrationair flow rate
CLF = Coolingloadfactor
BF= Ballast Factor for light
SC = Solar Heat Transfer Coefficient
U = DesignHeat Transfer Coefficient
SCL= Solar CoolingLoad
CLTD= CoolingLoadTemperature difference
Cooling Load Calculation by CLTD method
SUM
Total CoolingLoad -

21. ARCHITECTURE
31.01
36.41
10.33
2.83 2.83
10.33
N
W
S
E
window window window
2.62
0.89
Wall thicknes N
& W
Wall thicknes S
& E
5.33 Door
Wall height
11.1
Units
are in
ft
Window
Height
5.5
Height
6.91

22. WEATHER DATA
At an average temperature of 27.0 °C | 80.7 °F, August is the hottest month of the year. January is the coldest
month, with temperatures averaging 17.3 °C | 63.2 °F. Hence, we can see that the average temperature in
Sylhet, Bangladesh is most during the July-August months.

23. Cont..
It shows the average, minimum, and maximum temperature of Sylhet, Bangladesh for 12 months
over last 20 years

24. CONSIDERATIONS AND ASSUMPTIONS
 Weather conditions are selected from a long-term statistical database.
 The solar loads on the building are assumed to be those that would occur
on a clear day in the month chosen for the calculations.
 All building equipment and appliances are considered to be operating at a
reasonably representative capacity.
 Latent as well as sensible loads are considered.
 The ventilation rates are assumed on-air changes.
 Windows are externally shaded.

25. MEASURED DATA
Wall Dimension
Length Width Height
Wall 32.9 ft 27.5ft 11.1
Window Dimension
Length Height
Window (x2) 14.6ft, 10.4ft 5.5ft

26. Cont..
• We consider the window glass type is single and the inside shade is drapery, Venetian blind,
or translucent roller shade.
• Persons: 36
• Light: 4*13 W= 52 W
• Computer: 2080 W

27. VALUES OF CONSTANT FOR FOUR DIFFERENT
ORIENTATION
 U value for existing wall 0.38 Btu/(hr ft² °F)
 U value for existing glass 0.81 Btu/(hr ft² °F)
 U value for existing floor area 0.25 Btu/(hr ft² °F)
 U value for existing roof 0.12 Btu/(hr ft² °F)
 Solar time is 13 hr
 Temperature difference (outdoor and indoor) 11 °F (for July) and 14 °F (for August)
 SC value for existing glass 0.5
 CLTD value for glass 12 ( for solar time 13)
 CLF value 0.3 for zone type D
 AHRD is 0.88%
 Computer heat gain is 3.414 Btu-hr/Watt
 The ballast Factor is 0.88 (usually)
 Air change rate 0.46

28. Cont..
July August July August
Direction CLTD CLTD SCL SCL
North 26 25 33 25
East 36 36 59 36
South 29 41 32 47
West 27 27 53 54

29. ROOM ORIENTATIONS
There are 4 different possibilities for room orientation.

30. RESULTS AND DISCUSSIONS
37000
38000
39000
40000
41000
42000
43000
NE NW SE SW
Cooling
load
Btu/hr
Room orientation
CLC
July
August
FIGURE 05: Comparison of cooling load (existing)
In the 05 bar chart, it is
shown that July month has
less cooling load in all
directions compare to
August month and the
northwest orientation has
the lowest cooling load
among the four
orientations.

31. Cont..
40000
41000
42000
43000
44000
45000
46000
47000
NE ( north is
full glass)
NW ( north is
full glass)
SE ( south is
full glass)
SW ( south is
full glass)
Cooling
load
Btu/hr
Room orientation
CLC
July
August
FIGURE 06: Comparison of cooling load (North or south side glass)
In the 06 bar charts, the
cooling load is less in
August for the
northeast and
northwest direction but
for the southeast and
southwest direction
cooling load is less in
July month when North
or South side is full
glass.

32. Cont.
45000
46000
47000
48000
49000
50000
51000
NE ( east is full
glass)
NW ( west is full
glass)
SE ( east is full
glass)
SW ( west is full
glass)
Room orientation
CLC
July
August
FIGURE 07: Comparison of cooling load (East or west side glass)
In the 07 bar charts,
we see the same result
as the 05 bar charts
when East or West
side is full glass. Here,
July month has less
cooling load in all
directions compare to
August month and the
northwest orientation
has the lowest cooling
load among the four
orientations.

33. Cont.
36000
37000
38000
39000
40000
41000
42000
43000
44000
45000
NE (north is full
glass)
NW(north is full
glass)
SE ( south is full
glass)
SW ( south is full
glass)
Cooling
load
Btu/hr
Room orientation
July
glass concrete combination
one side is full glass
FIGURE 08: Comparison of cooling load for Existing and one
side full glass in July month (North or south side glass)

34. Cont.
0
10000
20000
30000
40000
50000
60000
NE ( east is full
glass)
NW ( west is full
glass)
SE ( east is full
glass)
SW ( west is full
glass)
Cooling
load
Btu/hr
Room orientation
July
glass concrete combination
one side is full glass
FIGURE 09: Comparison of cooling load for Existing and one
side full glass in July month (East or west side glass)

35. Cont.
34000
36000
38000
40000
42000
44000
46000
48000
NE (north is full
glass)
NW(north is full
glass)
SE ( south is full
glass)
SW ( south is
full glass)
Cooling
load
Btu/hr
Room orientation
August
glass concrete combination
one side is full glass
FIGURE 10: Comparison of cooling load for Existing and one
side full glass in August month (North or south side glass)

36. Cont.
0
10000
20000
30000
40000
50000
60000
NE ( east is full
glass)
NW ( west is full
glass)
SE ( east is full
glass)
SW ( west is full
glass)
Cooling
load
Btu/hr
Room orientation
August
glass concrete combination
one side is full glass
FIGURE 11: Comparison of cooling load for Existing and one
side full glass in August month (East or west side glass)

37. Cont.
• The 08 to 11 bar charts, show the comparison of cooling load between the
existing design and when one side is full glass.
• The result is clear that the cooling load greatly increased when a side is
fully covered with glass because of the solar load.
• The the glass area affected Cooling Load significantly.

38. FINDINGS
 Cooling load greatly depends on facing the window side of the room.
 The Northwest direction is the best suitable for constructing a Computer Lab room as this facing has
the minimum cooling load compared to the other directions.
 The maximum cooling load for the existing Computer Lab room is in August month (42,502
Btu/hr).
 If we replace the wall with glass, it will increase the cooling load significantly. So, the glass area
should be chosen wisely.
 Perfect room orientations for a room that has high-performance equipment, can make the air
conditioning system more energy efficient.

39. CONCLUSION
• We investigated the impact of room orientation on the cooling load calculation of a
computer lab using MS Excel.
• The results showed that the orientation of the room had a significant impact on the
cooling load calculation, with the southeast-facing wall having the highest cooling
load and the northwest-facing wall having the lowest cooling load.
• The use of MS Excel for cooling load calculation was found to be a simple and
effective approach for small-scale projects, and the results of this study are
expected to be useful for architects, engineers, and HVAC professionals in
designing and optimizing cooling systems for computer labs.
• In conclusion, the room orientation is an important factor that needs to be
considered in the cooling load calculation of buildings, and further research is
recommended to investigate the impact of other factors on cooling load calculation
in different types of buildings.

40. RECOMMENDATION FOR FUTURE STUDY
• Real-life data can be used for future room orientations to get more accurate
results.
• A calculation can be done for the single-story building.
• The limitations of the research can be reduced using accurate location and
weather data to attain more viable results.

41. LIMITATIONS OF THE RESEARCH
 The wall no is 1 and the roof no is 2 for this study.
 The zone type was D for all cases.
 We conduct the calculation only for July and August month as these are the hottest month
for this particular region.
 The number of people in the computer lab room can be varied.
 We conducted the calculation only for a multi-story building.
 The outdoor and indoor temperature and humidity ratio differences have been taken on
average.

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