The heat gain formula is given by,
q = 1.10 × cfm × (to – ti)
Where,
- q = sensible heat gain from the outside air in Btu/h
- cfm = flow rate of outside air entering the building
- to= outside air temperature in ∘F
- ti = inside air temperature in ∘F
Example 1
Calculate the sensible heat gain for a ventilation flow rate of 9,000 cfm if the outside air temperature (to) is 88∘F and the inside air temperature (ti) is 80∘F.
Solution:
Given data:
cfm = 9000
to = 88
ti = 80
Substitute in the given formula, we get
q = 1.10 × cfm × (to – ti)
q = 1.10 × 9000 × (88-80)
q = 79200
Therefore, the heat gain is 79200.
Example 2
Calculate the total heat gain due to the ventilation for 5000 cfm of air when the enthalpy of outside air is 35 and the enthalpy of the inside air is 30.0.
Solution:
Given data:
cfm = 5000
to = 35
ti = 30
Substitute in the corresponding formula,
q = 1.10 × cfm × (to – ti)
q = 1.10 × 5000 × (35 – 30)
q = 27500
Therefore, the heat gain is 27500.