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In: Mechanical Engineering

2. A refrigeration machine has been designed based on R134a. The design capacity is 15 tons.  ...

2. A refrigeration machine has been designed based on R134a. The design capacity is 15 tons.   The evaporator coil design temperature is 8 oC. The refrigerant enters the compressor as a slightly superheated vapor at 15 oC. The condenser coil design pressure is 14 bar. Refrigerant enters the expansion valve as a compressed (subcooled) liquid at 44 C. Note that the temperature of the air passing over the tubing in the evaporator coil will be higher than 8 oC and the temperature of the air passing over the condenser coil will be lower than the coil temperature. Use 80% for the compressor isentropic efficiency.
a. Calculate the power required to run the compressor under these design conditions and the required mass flow rate of R134a. (30 pts)

b. Find the rate of heat transfer for the condenser (high pressure side) of the system. (15 pts)

c. Find the quality of the refrigerant as it enters the evaporator. (10 pts)



3. A small gas turbine engine is used to produce power for auxiliary systems. This is a simple gas turbine open to the atmosphere. Air enters the compressor at 1 bar, 300 K. The compressor pressure ratio is 3.5:1. After passing through the combustion chamber, the air enters the turbine at a temperature of 1300 K. Determine the mass flow rate of air needed for the turbine to produce 60 kW of power. Also determine the heat that must be generated in the combustors. (30 pts) Solar collector …

Solutions

Expert Solution

For Question 2.....

process 1 to 2 is isentropic compression

process 1 to2' is actual compression

process 2' to 3 is isobaric heat rejection

process 3 to 4 is isenthalpic expansion

process 4 to 1 is isobaric heat addition

samet mamat answered 3 months ago
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