ME321 (Spring 08) - Take-home Quiz 1 ---- Name________________________

In a cooling application in a very warm environment it is required to reduce the temperature of air flowing through an insulated duct from 35°C to 10°C. One approach is to use an high-pressure R134a air conditioning system, as sketched in the figure below:

Use the R134a tables to determine relevant properties at the various stations, and derive all equations used starting from the basic energy equation for a flow system, the basic definition of Coefficient of Performance of an air conditioning system (COP_AC), and the equation of enthalpy of an ideal gas.

• a) Neatly sketch the complete air conditioning cycle above on the P-h diagram provided, showing clearly all four processes (1) - (2) - (3) - (4) - (1).
  
• b) Determine the mass flow rate of the refrigerant in the system. Note that the volumetric flow rate of the refrigerant (0.6 liters/minute) is measured at the outlet of the condenser.
  
• c) Determine the heat transferred from the air blowing through the insulated cooling duct to the evaporator [kW], the work done on the compressor [kW], and the Coefficient of Performance (COP_AC) of the air conditioning system.
  
• d) Consider the air passing through the insulated duct of the evaporator section. Notice that the temperature of the air passing through the duct is decreased by 25°C. Neglecting the work done by the fan determine the mass flow rate of the air through the duct..

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Declaration of Honesty - I hereby declare that this take-home quiz is my own work, and that I did not collaborate with or receive help from anyone else while doing it.

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