Ejector configuration for designing a simple and high performance solar cooling system

Ejector refrigeration cycle is a simple system, which can provide cooling by using solar thermal energy. Instead of a mechanical compressor of refrigeration cycle, refrigerant in evaporator is evacuated by an ejector using supersonic flow generated by the vapor pressure at temperatures being higher than around 60 °C. The ejector configuration design is a key to get a high efficiency of the cycle. In order to realize the behavior of the refrigerant in ejector, computational fluid dynamics (CFD) is applied to get the best geometry parameters, and then the parameters are confirmed by experimental trials. The CFD is developed as an in-house solver of the compressible Navier-Stokes equations. Through the numerical and experimental approach, four sets of configuration parameters of a mixing section area and a nozzle exit area of the ejector are being considered. A conclusion is that an appropriate mixing section area can make the greater cooling capacity but the condensing temperature decreases, while a smaller nozzle exit area can avoid the energy loss of shockwave that makes reliable repeatability and higher condensing temperature but lower cooling capacity in our experimental trials. The performances of ejector cycles having four different sets of configuration parameters cannot exceed a linear relationship between cooling capacity and condenser temperature so far. This paper reports an up-to-date result for developing an appropriate design method of ejector configuration.