Workers in the petrochemical industry often wear flame-retardant jumpsuits. Unfortunately, the material from which they are made hinders evaporation of perspiration, and consequently heat stress can be a hazard in plants where it is hot and humid. A control room in a petrochemical facility with dimensions 20 ft times 40 ft times 10 ft is used by workers to relax periodically in a cool environment. One summer day, the ambient air temperature is 33 degree C and the relative humidity is 96%. The air conditioning (AC) unit in the control room takes in ambient air and cools it to 11 degree C, 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 22 degree C, and there are 15 changes of room air per hour. The process may be shown schematically as follows.

(a) Use the psychrometric chart to estimate the following properties of the ambient air, cooled air, and exhaust air: moisture content, dew point, humid volume, and enthalpy at the process condition. Also estimate the volumetric flow rate (m ³ /h) and relative humidity of the exhaust air. How could you know simply by inspection of the ambient air properties that some of the water entering the air conditioner would be condensed?

(b) Draw and fully label a flowchart of the process.

(Suggestion: Label the molar flow rates of each stream component.) Then calculate the rate of condensation of water (kg/h).

Transcribed Image Text:

Ambient air 33°C, h,= 96% ¦ (kW) AC UNIT Condensate 11°C Cooled air 11°C ¦ė, (kW) 1 CONTROL ROOM Exhaust air V= 15 room volumes/h 22°C Ambient air 33°C, h,= 96% ¦ (kW) AC UNIT Condensate 11°C Cooled air 11°C ¦ė, (kW) 1 CONTROL ROOM Exhaust air V= 15 room volumes/h 22°C

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