You are designing a refrigeration cycle, and have the option of using either a compressor with an efficiency of 70% or a compressor that is more expensive by $5000 but has an efficiency of 80%. The following specifications are valid regardless of which compressor is used:

∎ The refrigerant is HFC-134a.

∎ The liquid leaving the condenser is saturated liquid at T = 50°C.

∎ The boiler operates at T = 0°C.

∎ The vapor leaving the boiler is saturated vapor.

∎ The cycle must have QC = 1000 kJ/min in the boiler.

A. Determine the flow rate of refrigerant. Is it the same or different in the two cycles?

B. Determine the compressor work for each of the two possible compressors.

C. Determine the coefficient of performance for the cycle with each of the two possible compressors.

D. The compressor runs on electricity, which is available for $0.10/kWhr. Assuming the refrigeration system runs constantly, how long would the system have to run in order for the higher-efficiency compressor to be cost effective?