Cogeneration can improve energy utilization efficiency significantly. In this paper, a new ammonia-water system is proposed for the cogeneration of refrigeration and power. The plant operates in a parallel combined cycle mode with an ammonia-water Rankine cycle and an ammonia refrigeration cycle, interconnected by absorption, separation, and heat transfer processes. The performance was evaluated by both energy and exergy efficiencies, with the latter providing good guidance for system improvement. The influences of the key parameters, which include the basic working solution concentration, the cooling water temperature, and the Rankine cycle turbine inlet parameters on the cycle performance, have been investigated. It is found that the cycle has a good thermal performance, with energy and exergy efficiencies of 27.7% and 55.7%, respectively, for the base-case studied (having a maximum cycle temperature of 450°C). Comparison with the conventional separate generation of power and refrigeration having the same outputs shows that the energy consumption of the cogeneration cycle is markedly lower. A brief review of desirable properties of fluid pairs for such cogeneration cycles was made, and detailed studies for finding new fluid pairs and the impact of their properties on cogeneration system performance are absent and are very recommended.
Gas hydrates at high pressure