 # Sensible Heat Formula

## What is sensible heat?

The sensible heat is a form of energy emitted into the atmosphere or absorbed. The concerned of sensible heat is only the change in the temperature of gas or material but not the phase shift. The phase shift between the solid, liquid and gas is relevant to the latent heat. The sensible heat formula is used to calculate the flow of air in the electric furnace.

The sensible heat formula with a change in temperature is expressed as

Q sensible= 1.10 x cfm x (to – ti)

Where

Q sensible = Heat gain from outside in Btu/h

1.10 = product of heat capacity of air 0.018 Btu/oF

Cfm = rate of flow of air entering from outside

to= Temperature outside in oF

ti = Temperature inside in oF

Example 1

Calculate the sensible heat gain of a ventilation flow rate of 10,000 cfm when the temperature (to) of outside air is 88oF and inside air temperature (ti) is 78oF.

Solution

Qsensible = 1.10 x cfm x (to – ti)

Qsensible = 1.10 x 10000 x (88 – 78)

Qsensible = 110,000 Btu/h

Hence, the sensible heat gain is 110,000 Btu/h.

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