Development and Analysis of a Multi-evaporator Cooling System with Electronic Expansion Valves

摘要

In this study, a vapor compression cooling system with three evaporators and electronic expansion valves was designed, manufactured and tested experimentally. Compressor of this system was converted to be inverter driven which enabled it to run at variable speeds. Temperature values of cold rooms were controlled more sensitive by using electronic expansion valves. Energy analysis was done by comparing the operating parameters of the system with constant and variable speeds. Programmable logic control (PLC) and cold room controls were used to control the system. The PLC device provided the variable operation of the system by determining the required operation frequency of the compressor according to the changes at the suction line. Using this program, the desired values are set on the PLC screen and the multi-evaporator cooling system was tested at various conditions. The desired conditions are determined for the system at 0,+5 and -5 degrees C temperatures. Calculations on the experimental results revealed that the cooling coefficient of performance is 1.86 for the constant frequency operation and 2.22 for the variable frequency operation. Besides, it was determined experimentally that the system running on variable frequency consumed 20% less electrical energy than the constant frequency system.