Question

4. On a typical autumn day, outside air with a dry bulb temperature of 15°C and 40% relative humidity is brought into a processing facility where it is to be used for a controlled storage chamber. The air must be heated to 37°C and humidified to 90% relative humidity.

Calculate: (11 marks total)

1. The relative humidity of the air when it is heated to 37°C, but BEFORE it is humidified. (No water has been added to the air yet). (2 marks)
2. The heat required to raise the temperature of the incoming air before it is humidified on a “per kg dry air” basis. (This is the air in part a of this question). (3 marks)
3. The amount of water that must be added to the heated incoming air to achieve the desired relative humidity. (Do not worry about the temperature of the water used to humidify it or any evaporative cooling effects etc.) (2 marks)
4. The amount of moisture lost by the heated and humidified air if it was cooled to 21°C and used as supply air for another controlled environment room. (2 marks)
5. Would it be comfortable for a person to work in the 21°C room described in Part d? (Assume that 21°C is a good working temperature and the air was filtered and deemed safe for further use). (2 marks)

(HINT: Calculate using the Normal Temperature Psychometric Chart when applicable)