Experimental Study on The Effect of Capillary Tube Geometry on The Performance of Vapour Compression Refrigeration System

Abstract

A domestic refrigerator of 5 ft3 capacity is used to study the effect of coiled diameter and pitch distance of a capillary tube. Five capillary tubes of 2 mm in diameter and 1500 mm length each are used, as same as original capillary tube of the refrigerator. The capillary tubes is formed in five shapes, each one has different coil diameter (D) namely 25, 50, 75, 100 and 125 mm in diameter, in addition three distances between each coil (pitch (P)) is tested, namely 6, 8 and 10 mm. The pressure at inlet and outlet of capillary are measured to calculate the cycle COP, as well as the power consumed by the cycle compressor is measured to calculate the mass flow rate of refrigerant. The work show that the coiled diameter of capillary tube affect the cycle COP strongly, as the capillary coiled diameter (D) increases from 25 to 100 mm the cycle COP increases from 2.8 to 3.7 when the cabinet temperature equals to 8oC. The increases of coiled diameter more than 100 mm shows insignificant effect on the cycle COP. While the pitch space of capillary tube coiled shows minor effect on the cycle COP. Moreover, to the mass flow rate of refrigerant increases with approximately ranges from 1.2−2.7