A control room in a petrochemical facility with dimensions 20 ft x 40 ft x 10 ft is used by workers to relax periodically in a cool environment. One summer day, the ambient temperature was 33oC and the relative humidity 96%. The A/C unit in the control room takes in ambient air and cools it to 11oC, which causes condensation of water that is discharged to a drain, and delivers the cooled air to the control room. The room air is maintained at 22oC and there are 15 changes of room air per hour. The process may be depicted as shown below. i). Use the psychrometric chart to tabulate the following properties of the ambient air, cooled air, and exhaust air: moisture content, dew point, humid volume, and enthalpy at the process conditions. Also estimate the volumetric flow rate (m3/h) and relative humidity (%) of the exhaust air.
ii). Draw and fully label a flowchart of the process using mass flow rates (kg/h) and calculate the rate of condensation of water (kg/h)
iii). Prepare an inlet-outlet table for an energy balance on the A/C, taking the same reference conditions of Figure 8.4-1, and calculate the cooling load on the A/C [Qac (kW)]
iv). Calculate the net rate of heat transfer to the air in the room, Qr(kW), and list probable sources of this heat.
A control room in a petrochemical facility with dimensions 20 ft x 40 ft x 10 ft is used by workers to relax periodically in a cool environment. One summer day, the ambient temperature was 33oC and the relative humidity 96%. The A/C unit in the control room takes in ambient air and cools it to 11oC, which causes condensation of water that is discharged to a drain, and delivers the cooled air to the control room. The room air is maintained at 22oC and there are 15 changes of room air per hour. The process may be depicted as shown below. i). Use the psychrometric chart to tabulate the following properties of the ambient air, cooled air, and exhaust air: moisture content, dew point, humid volume, and enthalpy at the process conditions. Also estimate the volumetric flow rate (m3/h) and relative humidity (%) of the exhaust air.
ii). Draw and fully label a flowchart of the process using mass flow rates (kg/h) and calculate the rate of condensation of water (kg/h)
iii). Prepare an inlet-outlet table for an energy balance on the A/C, taking the same reference conditions of Figure 8.4-1, and calculate the cooling load on the A/C [Qac (kW)]
iv). Calculate the net rate of heat transfer to the air in the room, Qr(kW), and list probable sources of this heat.
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