The central cubical area of an office building at sea level has a floor area of 4000 ft2 and is occupied by 30 people who each produce 200 Btu/h of sensible heat and 250 Btu/h of latent heat. Heat gains from the lighting for the space produces a load of 1.2 W/ft2. (Heat gains from lights and people represent the only cooling load in the space.) The office is to be maintained at 72°F and 50% relative humidity. Conditioned air is supplied at 60°F to meet the sensible and latent loads. To meet the loads, what must be the mass flow rate and humidity ratio of the supply air?

a. What are the sensible and total loads in the space?

b. What is the sensible heat ratio (SHR) of the load?

c. What supply air mass flow rate is required to meet the sensible load?

d. Given that the supply air temperature is 60°F and the flow rate from c), what are the enthalpy and humidity ratio of the supply air to meet both the sensible and latent loads?