We have seen the basic concept of HVAC in our previous post "Heating ventilating and air conditioning (HVAC)".
Let us consider how we will calculate the cooling load calculation for HVAC system .Before starting the calculation of cooling load, I will suggest looking previous post "Heating ventilating and air conditioning (HVAC)" for better understanding the concept of cooling load calculations, So let us start.
Cooling load calculation
In following table, we will come to
know that how we may proceed to calculate the cooling load for our selected
site.
Sr. NO.
|
Load sources
|
Calculating equation
|
1
|
Window
& Glass Areas
|
q=
(GLF)A
|
2
|
Doors
|
q=U
d A (CLTD)
|
3
|
Above
grade exterior wall
|
q=U
W A (CLTD)
|
4
|
Partitions
for unconditioned space
|
q=U
P A Δ t
|
5
|
Infiltration
|
q
= 1.1QΔt
Where,
Q = ACH * Room volume / 60
|
6
|
Roofs
and ceiling
|
q=U
f A (CLTD)
|
7
|
Floors
those are exposed
|
q=U
f A (CLTD)
|
8
|
Internal
Loads , such as
People
Lights
Appliances
|
Let
for one person
230
BTU/Hr
|
Total Cooling Load
= L F *
Summation of sensible cooling load for individual components
|
||
Where,
q= Sensible Cooling load (Btu/h)
Δ t = Difference between temperature of air of inside and outside (0F)
Q= Volumetric air flow rate (CFM)
A= Area of surface in ft2
U= U factor for suitable construction (Btu/h. ft2. 0F)
LF = latent load multiplier
ACH = air changes / hour, 1/h
CLTD = Cooling load temperature difference, °F
GLF = glass load factor, Btu/h· ft2
We will determine cooling load room by room in order to calculate the proper air distribution
Living Room
Infiltration-
Q = ACH * Room volume / 60
Q = (0.5 x 3840)/60
Q =32
q = 1.1QΔt
q = 1.1 x 32 x (96-75)
q = 740 Btu/h
Occupant –
As we have mentioned above that one
person 230 BTU/Hr
q = 230 x 4 = 920 Btu/h
Appliances-
As we have mentioned above that 50%
load of kitchen appliance will be taken in living room, hence
q = 0.5 x 1600
q = 800 Btu/h
Kitchen-
Infiltration-
Q = ACH * Room volume / 60
Q = (0.5 x 1920)/60
Q =16
q = 1.1QΔt
q = 1.1 x 16 x (96-75)
q = 370 Btu/h
Occupant –
As we know that there is no occupant
q = 0
Appliances-
As we have mentioned above that 25%
load of utility appliance will be taken in kitchen room, hence
q = 0.5 x 1600 + 1600/4
q = 1200 Btu/h
We will find complete cooling load
calculation for living room and kitchen separately with the help of following
mentioned table
For Living room
Description
|
Area (Ft2)
|
GLF
(Btu/h· ft2)
|
Factor-U
(Btu/h. ft2. 0F)
|
CLTD
(°F)
|
Cooling Load
(Btu/h)
|
West Wall
|
91
|
0.06
|
24
|
131
|
|
Partition
|
192
|
0.07
|
12
|
161
|
|
Roof
|
480
|
0.05
|
48
|
1152
|
|
West door
|
21
|
0.32
|
24
|
161
|
|
West glass
|
35
|
44
|
1540
|
||
Shaded glass
|
13
|
19
|
247
|
For Kitchen
Description
|
Area
(Ft2)
|
GLF
(Btu/h· ft2)
|
Factor-U
(Btu/h. ft2. 0F)
|
CLTD
(°F)
|
Cooling Load
(Btu/h)
|
East Wall
|
135
|
0.06
|
24
|
194
|
|
Roof
|
240
|
0.05
|
48
|
576
|
|
East Glass
|
14
|
44
|
616
|
||
Shaded glass
|
11
|
19
|
209
|
GLF, CLTD are values taken from HVAC
design data. These are standard value based on the outdoor design temperature.
Cooling load, we have calculated by
using formula that we have mentioned above for each cases.
Complete cooling load calculation
Description
|
Roof, Door & wall
|
People
|
Glass
|
Appliances
|
Infiltration
|
Living room
|
1605
|
920
|
1787
|
800
|
740
|
Kitchen
|
770
|
825
|
1200
|
370
|
|
Storage & utility
|
1404
|
1200
|
443
|
||
Bed room#1
|
559
|
544
|
278
|
||
Bed room#2
|
686
|
548
|
278
|
||
Master Bed room with bath
|
1682
|
816
|
813
|
||
Bath room
|
540
|
276
|
295
|
||
Final /Total
|
7246
|
920
|
5096
|
3200
|
3217
|
Total cooling load = 7246 + 920 +5096 + 3200 + 3217
Total cooling load = 19679 Btu/h
We have to also consider duct losses
which will be 10 % or 1967.9
Duct losses = 1968
Summation of sensible cooling load
for individual components =
19679 + 1968 = 21647 Btu/h
Total Cooling Load = L F * Summation
of sensible cooling load for individual components
For a medium construction house L F
will be 1.15
Total Cooling Load = 1.15 x 21647 =24894 Btu/h
Total Cooling Load = 24894 Btu/h
This blog is basically based on the
process for calculating the cooling load calculations for HVAC system
.
I will suggest looking my previous post "Heating ventilating and air conditioning (HVAC)"
for better understanding of calculations as all assumptions have been taken in previous post.
For heating load calculations, please follow my next post
I will suggest looking my previous post "Heating ventilating and air conditioning (HVAC)"
for better understanding of calculations as all assumptions have been taken in previous post.
For heating load calculations, please follow my next post
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