Existing capillary tube models rely on general friction factor correlations, which were not designed for the flow of refrigerant through these tubes. Additionally, it is unknown whether the two-phase flow in them is homo- or heterogeneous. This work presents the development of an improved friction factor correlation, which was implemented in a numerical capillary tube model. The accuracy of the latter increased by ±1,3 % as a result of this. A visualization of the flow was also performed. It showed that the flow is a predominantly heterogeneous plug flow. In addition to the performed experiments, an algorithm for the optimization of capillary tube-suction line heat exchangers was also developed. Comparison of different optimization algorithms showed that evolutionary algorithms performed most favourably.
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