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Development and Performance Evaluation of a Two-Stage Cascade Refrigeration System for Ice Block Production

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Document pages: 17 pages

Abstract: A development and performance evaluation of a two-stage cascade refrigeration system for ice block production was carried out in this work. Two single stage vapour compression refrigeration systems were thermally coupled. The cascade refrigeration system thus formed enhances cooling effect and fast track ice production. This machine was designed for a refrigeration capacity of 3kW to achieve the conversion of 128.25m3 of water at 300C to ice block at -150C using R407A R410A as working fluids. Experimental test of the machine was conducted under fixed and variable load conditions with the temperature and pressure both at the inlet and exit of each of evaporator, compressor and condenser taken. From the data obtained the refrigerating effect, COP and overall efficiency were determined. The result of the performance evaluation shows that as the evaporator temperature increases from -150C to -30C keeping the temperature difference in the cascade condenser and condenser temperature constant, the refrigerating effect increases from 189.17kJ kg to 201.34kJ kg, the COP increases from 4.13 to 6.90 and the overall efficiency of the system increases from 61.03 to 64.27 . As the condenser temperature increases from 400C to 490C keeping the evaporator temperature and temperature difference in the cascade condenser constant, the refrigerating effect decreases from 189.17kJ kg to 184.37kJ kg, the COP decreases from 4.13 to 3.80 and the overall efficiency of the system decreases from 61.03 to 50.92 . However, as the temperature difference in the cascade condenser decreases from 60C to 20C keeping the evaporator and condenser temperature constant, the refrigerating effect increases from 190.76kJ kg to 197.06kJ kg, the COP increases from 4.18 to 4.62 and the overall efficiency of the system increases from 60.64 to 63.25 . The machine achieved the designed condition in six (6) hours and the ice blocks so produced retained its solid state for 48 hours with the cover remained closed which denote a very impressive transformation capacity and reliability of the device compare with other homemade.

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