Application of electronic expansion valves in domestic refrigerators

The aim of this work is at investigating the applicability of electronic expansion valves (EEVs) in domestic refrigerators. To this end, a valve with an orifice of 0.19 mm of hydraulic diameter was installed in a conventional refrigerator to correlate the flow restriction with the overall energy consumption spanning different operating conditions. Tests with the same refrigerator mounted with a capillary tube were also performed. Also, a mathematical model was devised to simulate the effect of the refrigerant charge and the expansion device restriction on the system performance. More than a thousand different conditions were simulated. The results revealed that zero superheating is not necessarily the best-case scenario in terms of energy consumption. In addition, it was noticed that the lowest energy consumptions were achieved for the highest refrigerant charges and expansion restrictions. Furthermore, it was observed that, when the surrounding temperature or the compressor speed were changed, the energy consumption could be reduced by varying the restriction of the expansion device. The system with the EEV, nonetheless, presented higher energy consumptions than the system with the capillary tube for most conditions, which was mostly related to the extra thermal load generated by the valve. Nevertheless, by increasing the internal heat exchanger length and mitigating the heat dissipated by the EEV, it was found that the system with the EEV consumed between 4 and 9% less energy than the system mounted with capillary tube under operating conditions different from that the capillary tube has been sized for.