A novel Gamma‐type duplex Stirling system to convert heat energy to cooling power: Theoretical and experimental study

Abstract

This article aims at coupling two Stirling machines together to produce cooling power from different heat sources. Two identical Gamma-type ST500 Stirling machines are coupled together. The first machine, named Stirling engine, is powered by burning natural gas and an electrical power supply as an auxiliary starter. The Stirling engine is connected to a second Stirling machine named Stirling refrigerator by a mechanical belt. The driving force is transferred to the Stirling refrigerator using the mechanical belt. Mechanical energy is then converted to cold energy in the Stirling refrigerator. This study presents the experimental and theoretical results by examining the whole system named duplex Stirling refrigerator system. Five experiments are performed on the system at different pressures to evaluate the results. Water circulation in copper coils is used to determine the cooling flux produced by the Stirling refrigerator. Finally, the coefficient of performance (COP) is calculated. The experimental data are validated using a MATLAB-based code developed based on the presented formulas in this study. The results show that the system's maximum COP and electrical efficiency, consisting of two similar 500 W Gamma-type Stirling machines, are between 0.21% and 70.8%, respectively. Setup theoretical and experimental efficiencies are 0.24 and 0.21, respectively, at the best case. The experimental results of the duplex Stirling refrigerator system used in this study are compared with the simulation results. Finally, the experimental results of this study are compared with some other reported results from different authors on the subject of the duplex Stirling refrigerator.