question archive Assume that you operate your own vegetable processing plant in which you process cucumbers into pickled products
Assume that you operate your own vegetable processing plant in which you process cucumbers into pickled products
Subject:PhysicsPrice: Bought3
Assume that you operate your own vegetable processing plant in which you process cucumbers into pickled products. Your supply of raw material, that is, freshly harvested cucumbers comes from farmers with whom you have entered into contractual agreement. The farmers deliver the cucumbers to central cooling centers maintained at 18°C from where you collect and deliver to the factory daily. However, because of an unexpected breakdown of one of processing lines, you are now forced to store 50% of the delivered material (equivalent to 88,000 kg) so as to repair the line and resume processing after 24 h. The storage is to be done in one of the factory’s cold room that is maintained at 5°C using HFC-134a vapor-compression refrigeration system. The evaporator works at -5°C while the condenser is set at 30 °C. Before entering the compressor, the refrigerant vapors leaving the evaporator are heated an additional 15°C, beyond the saturation point. Similarly the liquid refrigerant discharging from the condenser is sub-cooled an additional 15°C beyond the saturation point. Assuming that the compressor efficiency is 85% and the specific heat capacity of cucumbers is 4.061 kJ kg-1°C-1, respond to the following:Represent this process on the pressure enthalpy chart provided (6 marks)Calculate the refrigeration effect of the system (2 marks)Calculate the mass flow rate of the refrigerant (3 marks)Calculate the compressor power requirement (2 marks)Calculate coefficient of performance (2 mark)Calculate the mass flow rate, compressor power requirement, and coefficient of performance of the same system but without superheating and sub-cooling. (3 marks)Comment on the importance of super-heating and sub-cooling of the refrigerant by comparing the results you have computed in ii – v, with those computed in vi. (2 marks)Question Three (10 Marks)A cold storage room is being maintained at 2 °C using a vapour compression refrigeration system that uses R-134a. The evaporator and condenser temperatures are -5 °C and 40 °C, respectively. The refrigeration load is 20 tons. Assuming that the unit operates under saturated conditions and the compressor efficiency is 85%,represent this process on the pressure enthalpy chart (5 Marks)Calculate the mass flow rate of refrigerant (2 Marks)Calculate the compressor power requirement and the C.O.P. (3 Marks)
