Abstract
Recently power generation systems using ammonia-water binary mixtures as a working fluid have been attracting much attention for their efficient conversion of low-grade heat sources into useful energy forms. This paper presents the First and Second Law thermodynamic analysis for a heat recovery vapor generator (HRVG) of ammonia-water mixtures when the heat source is low-temperature energy in the form of sensible heat. In the analysis, key parameters such as ammonia mass concentration and pressure of the binary mixture are studied to investigate their effects on the system performance, including the effectiveness of heat transfer, entropy generation, and exergy efficiency. The results show that the ammonia concentration and the pressure of the mixture have significant effects on the system performance of the HRVG.
Highlights
A thermodynamic analysis based on the First Law can give a good estimation of the expected performance of a thermal system, it apparently has the inherent limitations of no distinction between work and heat and no provision for quantifying the quality of heat [1]
Ammonia mass concentration and pressure of the mixture are considered as the key system parameters of the system, and their effects are investigated on the temperature distributions and the system performance variables such as the effectiveness of heat transfer, entropy generation, and exergy efficiency
The heat source is a low-temperature heat source in the form of sensible energy and the heat recovery vapor generator (HRVG) consists of pre-heater, evaporator, and superheater
Summary
A thermodynamic analysis based on the First Law can give a good estimation of the expected performance of a thermal system, it apparently has the inherent limitations of no distinction between work and heat and no provision for quantifying the quality of heat [1]. The Second Law of Thermodynamics deals with quantifying the quality of energy, so it is suitable for evaluating the performance of heat exchanger systems and heat transfer intensification techniques It shows that not all the energy input into a system can be used effectively and the irreversibility of the heat exchange process could be characterized by the increase of entropy generation [5]. Kim et al [22,23,24] investigated the thermodynamic performances of ammonia-water based power generation cycles for the recovery of low-temperature heat sources They showed that the characteristics of temperature distributions in the fluid streams of the heat exchangers vary quite complicatedly and sensitively with changing system parameters. Thermodynamic analysis of entropy and exergy is performed for heat recovery vapor generator (HRVG) of ammonia-water mixture to covert low-temperature heat source to useful form of energy. Ammonia mass concentration and pressure of the mixture are considered as the key system parameters of the system, and their effects are investigated on the temperature distributions and the system performance variables such as the effectiveness of heat transfer, entropy generation, and exergy efficiency
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