How to calculate BTU value? | British Thermal Unit
BTU –
British Thermal Unit
Just we need to collect the rough details according to the particular place:
1. Area Length
2. Area Width
3. Area Height
4. Maximum Persons within the Room
5. Average outdoor Temperature
Also, we need to have two Assumptions regarding the temperatures.
Assumption
1:
Assume indoor
temperature as 20 Celsius, when the air conditioning process is over (A/C).
Assumption
2:
Assume the roof
temperature as 35 Celsius. This value is based on the outdoor temperature of the
area and might differ from the outdoor temperature but generally, when we do the calculations, we assume it as 35 Celsius.
Calculations
Calculation
1:
Total Area
of walls: A
How to
calculate the area of walls: - (Length * Height)*Number of walls +
(Width * Height)*Number of walls
The
answer should be in square meters (m2).
Calculation
2:
Total Area
of floors: B
How to
calculate the area of floors: (Length * Width)
The answer should be in square meters (m2).
Calculation
3:
Total Area
of Roof: C
How to
calculate the area of the roof: (Length * Width)
The
answer should be in square meters (m2).
Calculation
4:
The Heat
Transformation from Walls and Floors: D
The heat
transformation:
= (Total Area of walls & floors) * (Constant
Value) * (Cooling load temperature difference)
The constant value is equal to 2.15 for walls
= (A+B) * 2.15 *
(Average outdoor temperature – Assumption 1)
= (D) W
The
answer will be from Watt.
Calculation
5:
The Heat Transformation from Roof: E
The heat
transformation:
= (Total Area of Roof) *
(Constant Value) * (Cooling load temperature difference)
The constant value is equal to 1.316 for the roof
= C * 1.316 *
(Assumption 2 – Assumption 1)
= (E) W
The answer will be from Watt.
Calculation
6:
Internal
heat by occupants: F
= (Number of occupants * Constant
Value1) + (Number of occupants * Constant Value2)
The constant
value 1 is equal to 50 and Constant value 2 is equal to 80
= (Number of occupants * 50)
+ (Number of occupants * 80)
= (F) W
The
answer will be from Watt.
Calculation
7:
Total
Required Cooling Load = D + E + F
=
(D + E + F) W
Calculation
8:
Convert W
to BTU = (D + E + F) *
Constant Value
Constant
Value is equal to 3.4121
=
(D + E + F) * 3.4121
=
(Final Answer) BTU
We should
use an air conditioner machine that consists of more than this value (Final
Answer) BTU to remove heat.
Example 1:
There is a room consisting of 04 walls, a floor and a roof.
· Length - 6m
· Width - 5m
· Height - 3m
· Maximum Persons - 02
· Outdoor Temperature - 30⁰C
· Assumption 1- Assume that the indoor temperature as 20 Celsius, when the air conditioning process is over.
· Assumption 2- Assume roof temperature as 35 Celsius.
Calculation
1
Total area
of walls = (Length *
Height)*Number of walls + (Width * Height)*Number of walls
=
(6*3)*2 + (5*3)*2
=
36+30
=
66 m2
Calculation
2
Total area
of floors = (Length *
Width)
=
6*5
=
30 m2
Calculation
3
The area of
roof = (Length *
Width)
=
6*5
=
30m2
Calculation
4
The heat
transformation = (Total Area
of walls & floors) * (Constant Value) * (Cooling load
temperature difference)
=
(66+30) * 2.15 * (Average outdoor temperature – Assumption 1)
=
(66+30) * 2.15 * (30-20)
=
96*2.15*10
=
2064 W
Calculation
5
The heat
transformation = (Total Area
of Roof) * (Constant Value) * (Cooling load temperature
difference)
=
30 * 1.316 * (35-20)
=
30 * 1.316 * 15
=
592.2 W
Calculation
6
Internal
heat by occupants = (Number of
occupants * Constant Value1) + (Number of occupants * Constant
Value2)
=
(Number of occupants * 50) + (Number of occupants * 80)
=
(2*50) + (2*80)
= 260 W
Calculation
7
Total
Required Cooling Load = 2064 +
592.2 + 260
=
2916.2 W
Calculation
8
Convert W
to BTU = (2916.2) * Constant Value
= 2916.2 * 3.4121
=
9950.367 BTU
We should
use an air conditioner machine which consists of more than 9950.367 BTU to
remove heat.
Example 2:
There is a room consisting of 04 walls, a floor, and a roof.
· Length - 10m
· Width - 8m
· Height - 5m
· Maximum Persons - 12
· Outdoor Temperature - 33⁰C
· Assumption 1- Assume that the indoor temperature as 20 Celsius, when the air conditioning process is over.
· Assumption 2- Assume roof temperature as 35 Celsius.
Calculation
1
Total area
of walls = (Length *
Height)*Number of walls + (Width * Height)*Number of walls
=
(10*5)*2 + (8*5)*2
=
100+80
=
180 m2
Calculation
2
Total area
of floors = (Length *
Width)
=
10*8
=
80 m2
Calculation
3
The area of
roof = (Length *
Width)
=
10*8
=
80m2
Calculation
4
The heat
transformation = (Total Area
of walls & floors) * (Constant Value) * (Cooling load
temperature difference)
=
(180+80) * 2.15 * (Average outdoor temperature – Assumption 1)
=
(180+80) * 2.15 * (33-20)
=
260*2.15*13
=
7267 W
Calculation
5
The heat
transformation = (Total Area
of Roof) * (Constant Value) * (Cooling load temperature
difference)
=
80 * 1.316 * (35-20)
=
80 * 1.316 * 15
=
1579.2 W
Calculation
6
Internal heat
by occupants = (Number of
occupants * Constant Value1) + (Number of occupants * Constant
Value2)
=
(Number of occupants * 50) + (Number of occupants * 80)
=
(12*50) + (12*80)
=
1560 W
Calculation
7
Total
Required Cooling Load = 7267 + 1579.2
+ 1560
=
10406.2 W
Calculation
8
Convert W
to BTU = (10406.2) * Constant Value
= 10406.2 * 3.4121
=
35506.995 BTU
We should
use an air conditioner machine which consists of more than 35506.995 BTU to
remove heat.
Example 3:
There is a factory consisting of 04 walls, a floor, a roof, and lighting resources. Additionally, we have to add the number of lights and the wattage of each one.
· Length - 10m
· Width - 8m
· Height - 5m
· Maximum Persons – 12
· Number of bulbs – 20
· Wattage of one bulb – 60 W
· Outdoor Temperature - 33⁰C
· Assumption 1- Assume that the indoor temperature as 20 Celsius, when the air conditioning process is over.
· Assumption 2- Assume roof temperature as 35 Celsius.
Calculation
1
Total area
of walls = (Length *
Height)*Number of walls + (Width * Height)*Number of walls
=
(10*5)*2 + (8*5)*2
=
100+80
=
180 m2
Calculation
2
Total area
of floors = (Length *
Width)
=
10*8
=
80 m2
Calculation
3
The area of
roof = (Length *
Width)
=
10*8
=
80m2
Calculation
4
The heat
transformation = (Total Area
of walls & floors) * (Constant Value) * (Cooling load
temperature difference)
=
(180+80) * 2.15 * (Average outdoor temperature – Assumption 1)
=
(180+80) * 2.15 * (33-20)
=
260*2.15*13
=
7267 W
Calculation
5
The heat
transformation = (Total Area
of Roof) * (Constant Value) * (Cooling load temperature
difference)
=
80 * 1.316 * (35-20)
=
80 * 1.316 * 15
=
1579.2 W
Calculation
6
Internal
heat by occupants = (Number of
occupants * Constant Value1) + (Number of occupants * Constant
Value2)
=
(Number of occupants * 50) + (Number of occupants * 80)
=
(12*50) + (12*80)
=
1560 W
Light
Calculation
Number
of bulbs = 20
The wattage of one bulb = 60 W
Calculation
=
Wattage of one bulb * 1.25 * Number of bulbs
=
60 * 1.25 * 20
=
1500 W
Calculation
7
Total
Required Cooling Load = 7267 +
1579.2 + 1560 + Light Calculation
= 7267 + 1579.2 + 1560 + 1500
=
11906.2 W
Calculation
8
Convert W
to BTU = (11906.2) * Constant Value
= 11906.2 * 3.4121
=
40625.145 BTU
We should
use an air conditioner machine which consists of more than 40625.145 BTU to
remove heat.
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