Calculate the Enthalpy of the Refrigeration Unit

Question

Consider the T-S diagram of a refrigerator unit. The working flid is R-22. The refrigerator operates between a low pressure of 0.60 bar absolute (measured in the evaporator) and high pressure of 18.0 bar absolute (measured in the condenser). Assume negligible pressure loss in either condenser (path 1 -> 2) or the evaporator (path 3-> 4). A throttle controls the pressure change between states 2 and 3. A perfectly insulated compressor provides the work for the cycle (Path 4->1). The quality of state 2 is 0.00 and the quality of state 4 is 1.00.

 

1) Cooling water at 25° C is used to facilitate heat exchange in the condenser (path 1->2). If the temperature of the cooling water can rise no more than 5° C, what is the minimum flow rate (kg/min) of water that is necessary to completely condense the R-22? Assume that the temperature of R-22 at state 1 is 130°C and the pressure is 18 bar. Take state 2 to be a saturated liquid with a quality of 0.0 and a pressure of 18 bar. The flow rate of R-22 is 1.5 kg/min. For cooling water, you can estimate the change in the enthalpy as dh =CpdT, where Cp is 4.2 kJ/kg*K.  

Summary    

The question belongs to Chemical Engineering and it is about refrigeration unit. The unit operates at low pressure of 0.60 bar and high pressure of 18 bar. The question is about estimating the enthalpy of the refrigeration unit where water cooled to 25°C is used for heat exchange.

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