PROPOSING AND ANALYSIS OF TWO COUPLED STIRLING ENGINES FOR HEAT-TO-COOL CONVERSIONPROPOSING AND ANALYSIS OF TWO COUPLED STIRLING ENGINES FOR HEAT-TO-COOL CONVERSION

The Stirling cycle is one of the thermodynamic cycles that has many advantages. Advantages of this cycle have made Stirling engines popular and widely applicable to the industry and other applications. One of the advantages of the Stirling cycle is its ability to operate inversely to produce cold energy. In this paper, a novel structure is proposed by which cold energy can be produced by a heat source using the coupling of two similar Stirling engines. By using this system, cold energy can be produced directly by the heat generated from renewable or non-renewable sources. The system is able to produce cold energy at different temperatures using solar energy, heat dissipation in thermal systems, biomass fuel, or other heat sources. Thermal energy is directly converted to the required mechanical energy for refrigeration in this system, which is the reason why this system is more efficient than others that convert mechanical energy to electrical energy and, then, convert the electrical energy to cold energy. In this paper, in addition to introducing and analyzing the proposed system, simulations are performed, showing that a temperature of $5^{0}C$ can be produced using a solar dish at an ambient temperature of $60^{0}C$, which is suitable for saving foodstuffs and vegetables. It is assumed that the first Stirling engine produces about 60 J work from solar energy. Then, this amount of work is transferred to the second engine using a mechanical belt. The second engine produces cold energy using the transferred work. The proposed Stirling engines include two identical ST500 Gamma-type Stirling engines coupled to each other to convert heat to cool. Environmental conditions are assumed based on actual values and requirements in the south of Iran.