and sensible loads to the lower left of the building zone conditions on the psych chart. 7. At current outdoor air conditions, does it make any sense to operate the evaporator to assist in meeting the total cooling load? 8. Assuming the evaporator coil is turned off and all cooling is met by the cooling coil, at what rate is water being removed from the air by the cooling coil? (lbmw/hr)/n4. What is the latent load of the building zone (Btu/hr)? 5. What is the sensible load of the building zone (Btu/hr)? 6. Now, using the information you have about the sensible and latent loads, determine the condition of the supply air (S) being provided to the building zone. Hint: Draw your latent and sensible loads to the lower left of the building zone conditions on the psych chart. 7. At current outdoor air conditions, does it make any sense to operate the evaporator to assist in meeting the total cooling load?/n1. Identify the indoor condition on the psychrometric chart for 5000 ft elevation (attached). Determine the following properties of the humid air: a. Wet-bulb temperature b. Humidity ratio c. Dew point temperature d. Enthalpy 2. What is the required mass flow rate of ventilation air (lbmda/hr) when at max occupancy? 3. Calculate the total cooling rate that must be provided by the evaporator and the cooling coil to maintain the building zone at its current conditions and the design airflow rate (Btu/hr)./nPart A: Psychrometrics An HVAC system for a small restaurant is being designed using 100% outdoor air and a design planned occupancy of 150 people, indoor temp at 68°F, and a relative humidity of 50%. The ventilation requirement is 10 cfm per person, measured at the ventilation air inlet (A). The building zone (Z) has a cooling load (LT) of 50,000 Btu/hr with a SHR of 0.67. Outdoor conditions (A) are 85°F dry-bulb and 70°F wet-bulb. Answer the following questions about this system. Ventilation air A Exhaust air Figure 6.13a © John Wiley & Sons, Inc. All rights reserved. Evaporator 0 Processed air C Supply air Return air S Building zone Z Cooling coil Ls i₁ 1. Identify the indoor condition on the psychrometric chart for 5000 ft elevation (attached). Determine the following properties of the humid air: a. Wet-bulb temperature b. Humidity ratio C. Dew point temperature d. Enthalpy
Fig: 1
Fig: 2
Fig: 3
Fig: 4