3. Variable air volume (VAV) HVAC system can vary circulation flow rate for different operating conditions. Consider a VAV HAVC system operates at the same part load as in Problem 2

with ambient conditions of 86 F dry-bulb and 70 F wet-bulb. The total load is 350,000 Btu/hr with the same sensible heat ratio of 0.8 and the same zone temperature of 77 F. The ventilation flow rate is the same at 1600 cfm. The bypass factor for the coil is 0.175 and the chilled water temperature is 50 F, which is the same as design conditions. Reheat is zero. Use the same method in problem 1 to calculate the zone relative humidity, coil load, and reheat heat transfer rate. List the results in Table 2. CAV at design condition CAV in part load VAV in part load Table 2 Properties of thermodynamics states of two iterations Circulation flow rate lbm/hr cfm Zone relative humidity Total load Btu/hr 500000 350000 350000 tons Coil load Btu/hr tons Reheat Btu/hr 0 0