A refrigeration process with interstage cooling uses refrigerant R134a. The outlet of the condenser is to be saturated liquid at 40°C. The evaporator is to operate at -20°C, and the outlet is saturated vapor. The economizer is to operate at 10°C. Refer to Fig. 5.10 for stream numbers in your solution.

(a) Determine the required flowrate of stream 1 if the cooling capacity of the unit is to be 8250 kJ/h.

(b) Determine the pressure of stream 3, and the work required by the first compressor if it has an efficiency of 85%.

(c) What are the flowrates of streams 7 and 6?

(d) What is the enthalpy of stream 4?

(e) Determine the work required by the second compressor (85% efficient) and the COP

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Flash Chamber 8 6 Hot Side Condenser Throttle Valve 7 1 Throttle Valve Vapor Phase Only Evaporator Cold Side 2nd Stage Compressor 5 1st Stage Compressor Figure 5.10 Flash chamber intercooling. 2 T P Liquid 8, 6 /4 const. P H 4 7 Two-Phase Region S 3 5