Study of the single-stage mixed-gases refrigeration cycle for cooling temperature-distributed heat loads

Abstract

The single-stage mixture refrigeration cycle is the simplest of numerous existing mixture refrigeration cycles. In this paper, detailed study was made on the use of a single-stage closed throttling refrigeration cycle with multicomponent zeotropic mixtures for cooling temperature-distributed heat loads. The heat capacity balance of the heat exchanger with temperature-distributed heat loads was calculated with an equation of state. Because of the important contribution of specific heat capacity from latent heat, the result shows that with optimal mixtures, the single-stage cycle can provide excellent performance for cooling temperature-distributed heat loads associated with gas liquefaction. The optimization result was also compared with other published results of calculations. A small-scale prototype based on the single-stage cycle was also developed and tested, which is driven by an oil-lubricated air-conditioning compressor with a nominal input power of 1.1 kW. Electrical resistances were used to simulate the temperature-distributed heat loads along the heat exchanger. The temperature-distributed heat loads were just used to simulate the gas liquefaction heat loads. Preliminary experimental results of 0.77 liter liquid methane per 1.2 kW·h and 1.3 liter liquid CF 4 per 1.2 kW·h were achieved. The significance of using single-stage mixture refrigeration cycle is that the configuration of the refrigeration system becomes much simpler than the traditional liquefaction system, while maintaining a high efficiency.