APPLIED ENGINEERING THERMODYNAMICS
MAE 115
1. How will the specific humidity and the relative humidity of the air contained in a well-sealed room change as it is heated?
2. Atmospheric air at a pressure of 1 atm and dry-bulb temperature of 32oC has a wet-bulb temperature of 18oC. Using the psychrometric chart, determine:
a. The relative humidity
b. The humidity ratio
c. The enthalpy
d. The dew-point temperature
e. The water vapor pressure
3. Atmospheric air at a pressure of 1 atm and dry-bulb temperature of 90oF has a dew-point temperature of 75oF. Using the psychrometric chart, determine:
a. The relative humidity
b. The humidity ratio
c. The enthalpy
d. The wet-bulb temperature
e. The water vapor pressure
4. An air-conditioning system operates at a total pressure of 1 atm and consists of a heating section and a humidifier that supplies wet steam (saturated water vapor) at 100oC. Air enters the heating section at 10oC and 70% relative humidity at a rate of 35 m3/min, and leaves the humidifying section at 20oC and 60% relative humidity. Determine:
a. The temperature and relative humidity of the air when it leaves the heating section
b. The rate of heat transfer in the heating section
c. The rate at which water is added to the air in the humidifying section
5. An automobile air conditioner uses refrigerant R-134a as the cooling fluid. The evaporator operates at 100 kPa gauge and the condenser operates at 1.5 MPa gauge. The compressor requires a power input of 6 kW and has an isentropic efficiency of 85%. Atmospheric air is 25oC and 60% relative humidity. The air enters the evaporator and leaves at 8oC and 90% relative humidity. Determine the volumetric flow rate of the atmospheric air entering the evaporator of the air conditioner in m3/min.
6. Two humid air streams are adiabatically mixed at 1 atm pressure to form a third stream. The first stream has a temperature of 40oC , a relative humidity of 40%, and a volumetric flow rate of 3 L/s. The second stream has a temperature of 15oC, a relative humidity of 80%, and avolumetric flow rate of 1 L/s. Calculate the temperature and relative humidity of the third stream.
7. A wet cooling tower is to cool 40 kg/s of water from 40oC to 30oC. Atmospheric air enters the tower at 1 atm with dry and wet-bulb temperatures of 22 and 16oC respectively, and leaves at 32oC with a relative humidity of 95%. Determine:
a. The volumetric flow rate of air into the cooling tower
b. The mass flow rate of the required makeup water