Experimental influence of an internal heat exchanger (IHX) using R513A and R134a in a vapor compression system

Coming refrigeration and air conditioning systems must include low GWP fluids and optimized components. An internal heat exchanger (IHX) is a common modification of the basic cycle to enhance its energy performance, and its benefits have been demonstrated with R134a and the recently developed hydrofluoro-olefin R1234yf. This paper assesses the experimental influence of a high effectiveness IHX using R134a, and the low GWP mixture R513A (a mixture of R134a and R1234yf) under different evaporating and condensing conditions (29 points tested in total). Discharge temperature has been increased up to 26 K for both fluids, and the greatest compression ratio is not feasible for R134a. The cooling capacity of the system results increased up to 5.6% for R513A whereas for R134a is around 3%. Furthermore, due to the minimum diminution of power consumption, COP also increases up to 8% for R513A and 4% for R134a. Because of the observed experimental results, high effectiveness IHX is recommended for R513A, especially for high compression ratio operations as long as the discharge temperature does not reach critical values. Finally, it has been found that Klein et al.’s and Hermes's correlations overestimate the COP benefit and the increase in power consumption should be considered.