Thermodynamic analysis and optimization of a new ammonia based combined power/cooling cycle

A detailed thermodynamic analysis of a combined thermal power and cooling cycle is conducted. This cycle innovatively combines Rankine and absorption refrigeration cycles and uses ammonia-water mixture as a working fluid. It can provide power output as well as refrigeration with power generation as a primary goal. The concept of this cycle is based on the unique feature of a multi-component working fluid, varying temperature boiling process. Therefore, a better thermal match is obtained in the boiler between sensible heat source and working fluid. It also takes advantage of the low boiling temperature of ammonia vapor so that a temperature lower than ambient is achieved at the exit of the turbine. This cycle can be used as a bottoming cycle using waste heat from a topping cycle or as an independent cycle using low temperature sources such as geothermal and solar energy.; A parametric analysis has been conducted for the proposed cycle under idealized conditions. It helps to understand the behavior of the cycle and also shows that cycle working conditions could be optimized for best performance. The effect of irreversibilities on the cycle performance has also been studied.; An optimization algorithm, Generalized Reduced Gradient (GRG) algorithm, is introduced to optimize the performance of the proposed cycle. It searches a feasible region of free variables defined by their constraints to optimize the performance criteria. Second law efficiency is chosen as the primary optimization objective while the cycle could be optimized for any other performance parameter.; Cycle performance over a range of source and ambient temperatures was investigated. It was found that for a source temperature of 360K, which is in the range of flat plate solar collectors, both power and refrigeration outputs are achieved under optimum conditions. All performance parameters, including first and second law efficiencies, and power and refrigeration outputs decrease as the ambient temperature goes up. On the other hand, for a source of 440K, optimum conditions do not provide any refrigeration. However, refrigeration can be obtained even for this temperature under non-optimum performance conditions. In addition, some specific applications of the proposed cycle are studied.