Calculate Humid Heat of Air - Examples and Online Calculator

Humid heat is an important parameter used in humid air calculations and it a a nearly constant in certain temperature ranges. Humid heat mainly depends on the amount of water vapor quantity associated with dry air. In this article, you can calculate Humid Heat online and will see some examples how to calculate it manually.



Definition of Humid Heat


General definition: Required heat to raise the unit mass of dry air and it's associated water vapor through unit temperature difference at constant pressure.


Definition with example: Required heat to raise the 1kg of dry air and it's associated water vapor through 10C temperature difference at 1 atm.



Online Calculator to calculate Humid Heat

  • Pressure of ambient air = 1 bar







Example of calculating humid heat of air using equation

Definition of Humid heat is given above in this tutorial and we can formulate an equation to calculate it as explain below.



equation to calculate humid heat of air

Calculate humid heat of ambient air at 26.850C. Absolute humidity of that air is 0.01 kg of water vapour per 1 kg of dry air.

Given absolute humidity should be less than the saturated absolute humidity at given temperature.


Equations used in calculating humid heat

Humid Heat = Heat Required to Raise 1kg of Dry air from 10C + Heat Required to Raise Associated Water Vapor with Dry air from 10C

Humid Heat = [1kg × Cp, dry air × 10C] + [H × Cp, water vapor × 10C]

Humid Heat = [Cp, dry air] + [H × Cp, water vapor]



At, 300K temperature and Absolute humidity = 0.01 kg of water vapor / 1kg of dry air

  • Specific heat capacity of air, Cp, dry air = 1.006 kJ kg0 K-1
  • Specific heat capacity of water vapor, Cp, water vapor = 1.9 kJ kg-1 K-1

Humid heat = 1.005 + (0.01 × 1.9)

Humid heat = 1.025 kJ kg-1 0C-1



Humid heat variation with temperature

Though it seems as humid heat mainly depends on the absolute humidity, it depends on temperature too when considering two significant temperature ranges due to variation of specific heat capacity in different temperature ranges.



At 500K temperature, we can modify the humid heat equation,

Specific heat capacity of air, Cp, dry air at 500K = 1.029 kJ kJ kg0 K-1

Specific heat capacity of water vapor, Cp, water vapor at 500K = 1.966 kJ kJ kg0 K-1

Humid heat = 1.029 + (0.01 × 1.966)

Humid heat = 1.045 kJ kg-1 0C-1


You can see, humid heat value was changed in some extent when temperature is varied from 300K to 500K.



Have Questions?






Calculate enthalpy of Humid air How to read psychrometric chart to calculate air properties Read dry bulb and wet bulb in psychrometric chart Calculate volume per 1kg of dry air using psychrometric chart Classifications and types of refrigerants Chemical properties of refrigerants