An Experimental and Theoretical Analysis of Capillary Tube-Suction Line Heat Exchangers

This report describes the complete process of testing capillary tube-suction line heat exchangers (CfSLHX). and presents preliminary data for non-adiabatic flow of R-134a in the capillary tube, as well as the comparison between the experimental data and simulation results. Mass flow rate is proportional to cross-sectional area, so manufacturer-specified tolerances of ??O.OOl" correspond to mass flow uncertainties up to 10%. Therefore a laminar water test method was developed for determining diameter much more accurately. Nitrogen tests are subject to greater uncertainty, and were found to be incapable of discerning tube roughness. Three two-phase friction factor correlations were examined and compared to the data. Three CTSLHX's were tested over a range of subcooled inlet temperatures and pressures, and mass flows measured with a coriolis meter. Hysteresis was observed; mass flow is multivalued and depends on whether the flash point is moving upstream or downstream. The same effect was observed in an operating refrigerator, affecting its thermodynamic cycle efficiency by 3%.Air Conditioning and Refrigeration Project 6