A single compressor system using R-12 as refrigerant has three evaporators of capacities 18 tonnes, 27 tonnes and 9 tonnes of refrigeration. The temperatures in the three evaporators are to be maintained at $-5^{\circ} \mathrm{C}, 0^{\circ} \mathrm{C}$ and $7^{\circ} \mathrm{C}$ respectively. The system is provided with multiple expansion valves and back pressure valves. The condenser pressure is 9.61 bar. The liquid refrigerant leaving the condenser is sub-cooled at $30^{\circ} \mathrm{C}$. The vapours leaving the evaporators are dry and saturated. Assume isentropic compression, determine the following: (i) Mass of refrigerant flowing through each evaporator. (ii) Power required to drive the compressor. (iii) Coefficient of performance of the system. (Pages : 3) Reg. No. : $\_\_\_\_$ Name : $\_\_\_\_$ G - 3444 Reg. No Name : $\_\_\_\_$ # Seventh Semester B.Tech. Degree Examination, June 2019 <br> 08.704 : REFRIGERATION AND AIR CONDITIONING (M) (2008 Scheme) Time : 3 Hours Max. Marks : 100 Instructions: (1) Use of Psychometric chart and refrigeration tables are Permitted. (2) Answer all question from Part A. Each carries 4 marks. And one full question from each Module of Part B. Each carries 20 marks.
Explanation
The mass of refrigerant flowing through each evaporator is calculated using the compressor displacement volume and the specific volume of saturated vapor at the evaporator conditions. The power required to drive the compressor is calculated using the mass flow rate, the pressure difference between the evaporator and condenser, and the specific enthalpy of vaporization. The coefficient of performance of the system is calculated using the power required to drive the compressor and the heat transfer rate at each evaporator.
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