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View Full Version : Help for refrigeration qn guys! :(



hanwei_86
24-05-2009, 01:44 PM
hey guys, i ve bumped into some problems dealing with a refrigeration qn, thermofluid based. maybe some kind and experienced souls can help me out with it. Here it goes :

A cold storage facility uses a two stage ammonia cooling system to
supply refrigeration to a blast freezer. The system is designed for air in the blast
freezer at –35oC, and ambient conditions of 40oC. Ammonia enters the low stage
compressor superheated by 10oC, enters the high stage compressor saturated, and
leaves the condenser subcooled by 5oC. Both evaporator and condenser require a
temperature difference of 5oC to transfer heat.
Intercooler pressure is set at the point where one-sixth of the mass of the liquid
from the condenser has flashed off (in reaching the intercooler pressure). Liquid is
then fed from the intercooler to the evaporator. Isentropic efficiency for each
compressor stage is 90%, and expansion is achieved via throttling.

What is the intercooler temperature (to the nearest C), and what are the
condenser, intercooler and evaporator pressures? (5 marks)
(c) Calculate the cooling effect (qrefrig). (5 marks)
(d) 120 kW of refrigeration is required. What is the refrigerant mass flow rate
through the condenser?

appreciate it!!:confused: