Energy and Exergy Analysis Study of Heat Exchanger in a Refrigeration System with Different Lengths of Capillary Tube

An experimental study was conducted to demonstrate the effect of a capillary tube length on the refrigeration system performance by adding heat exchanger. The heat exchanger was designed by laterally welding 70cm of capillary tube with the suction line. Different lengths of the capillary tubes, i.e. 160, 175, and 190cm, were studied; besides different refrigerant flow rates and condenser air fan velocities for both cases of adiabatic and nonadiabatic capillary tube. The experimental results showed an increase in the system performance by 17.96% with a decrease in the nonadiabatic capillary tube length from 190 to 160 cm at mass flow rate of 17.3 kg/hr and air velocity of 3 m/s. In addition, the increase in the air-speed has led to a COP increment by 17.47% at mass flow rate of 18.9 kg/hr and capillary tube length of 190 cm. Finally, at the capillary tube length of 190cm and refrigerant mass flow rate of 2.4g/s, the maximum enhancement of the refrigeration system performance and exergy efficiency by 6.7% and 35%, respectively, was achieved for air speed of 1m/s and 3 m/s, compared to the reference case of the adiabatic capillary tubes.