A comparison between the novel absorption refrigeration cycle and the conventional ammonia-water absorption refrigeration cycle

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.

One of the recently proposed systems that are capable of reaching to the low temperature of -40 ºC is the novel absorption refrigeration cycle with expander and compressor that works as a co-generation or cooling/power system. This cycle provides better COP than other co-generation low temperature cycles when the refrigerating temperature is low enough. By increasing the evaporation temperature to more than 253 ºC the conventional refrigeration cycle shows better COP and exergetic efficiency in comparison to the novel absorption refrigeration cycle. The purpose of the current study was to analyze the novel absorption refrigeration cycle from the viewpoint of exergy or second law in order to evaluate whether the cycle is practically efficient or not. The exergy destruction rate and the exergetic efficiency for each component were calculated and presented in the corresponding graphs to recognize the components with lower efficiency or higher exergy destruction rate. The influences of an expander in COP and exergetic efficiency were identified by ignoring the expander and super heater from the configuration of the novel absorption refrigeration cycle. Furthermore, energy and exergy balances of a conventional ammonia-water absorption refrigeration cycle were formulated to assess the performance of the system in low and high evaporation temperatures. Our results showed that the novel absorption refrigeration cycle obtains a COP of 0.1109 and exergetic efficiency of 0.1156 when the generation temperature is 360 K and evaporation temperature is 233 K. At the same situation, this cycle without using an expander obtains a COP of 0.0525. In addition, the lowest temperature that can be provided by a conventional refrigeration cycle is 252 K but with a much higher COP. Our results approved that it is possible to choose an absorption refrigeration cycle for a special application without wasting time and consuming extra exergy.