4.3.1. Cooling/Heating Equations

Try these first

1. 1.

   What is sensible heat? Provide a definition.

   Hint

   Think about how heat affects temperature directly.

2. 2.

   If a mass flow rate of air is 0.5 kg/s and the specific heat is 1005 J/(kg·K), what will be the heat transfer if the temperature changes by 5 K?

   Hint

   Use the formula Q = m·cp·ΔT.

3. 3.

   What is the formula for sensible heat?

   • Q = m·cp·ΔT
   • Q = m·hf·Δω
   • Q = m·c·ΔV

   Hint

   Recall which formula deals with temperature change.

4. 4.

   True or False: Latent heat affects only the temperature of the air.

   • True
   • False

   Hint

   Think about moisture and temperature changes.

5. 5.

   Given a mass flow rate of air as 0.25 kg/s and a latent heat of vaporization of 2,256 kJ/kg, calculate the heat transfer if the humidity ratio changes from 0.005 kg/kg to 0.01 kg/kg.

   Hint

   Identify the change in humidity ratio and apply the latent heat equation.

6. 6.

   An HVAC system experiences a heat gain of 40,000 BTU/hr due to internal loads. How much cooling capacity (in kW) is required if 1 BTU/hr = 0.000293 kW?

   Hint

   Remember to convert BTUs to kW using the conversion factor.