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An Experimental Study on Energy Recovery by a Pelton-Type Expander in a Domestic Refrigeration System

A Pelton-type two-phase expander was developed to replace the throttling valve for energy recovery in a domestic vapor-compression refrigeration system. The Pelton-type expander was designed and fabricated based on thermodynamic and mathematical analysis. It consists of two Laval nozzles and one simplified twin-arc blade impeller. A combined expander-generator prototype was validated in a R-410A domestic refrigeration system and demonstrated a stable operation within a wide speed range of up to 26,500 rpm. Experimental results showed the feasibility of integrating the Pelton-type expander into a domestic refrigeration system. A maximum isentropic efficiency of 32.8% was achieved under the experimental conditions. The relationships between the recovery work, the expander efficiency, and the impeller rotational speed were investigated. The results indicated that the velocity ratio was around 0.17 when the recovery work achieved the maximum value. The results also showed that the increase in the cooling capacity by 6.5% and the coefficient of performance (COP) by 5.4% could be obtained under the testing conditions.