Sensible Heat Formula

What is sensible heat?

The sensible heat is a type of energy released or absorbed in the atmosphere. Sensible heat concerns about changes in temperature of a gas or object but no change in phase.Latent heat is relevant to changes in phases between solids, liquids and gases. You can use sensible heat formula to calculate the flow of air for an electric furnace. The formula provides the amount of airflow. The sensible heat formula with change in temperature is given by

Q sensible= 1.10 x cfm x (to – ti)


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

Air consists of 100 grams of moisture per pound of dry air and inside air contains 72 grams per pound of dry air. Calculate the sensible heat gain.


Qsensible = 0.68 x cfm x (100 – 72)

= 0.68 x 10000 x (100 – 72)

= 190400 Btu/h

Hence, the sensible heat gain is 190400 Btu/h.


Example 2

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.


Qsensible = 1.10 x cfm x (to – ti)

= 1.10 x 10000 x (88 – 78)

= 110,000 Btu/h.

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


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