Energy and exergy analysis of a double absorption heat transformer operating with water/lithium bromide

Abstract

SUMMARYIn the present study, the first and second law of thermodynamics have been used to analyze in detail the performance of a double absorption (lift) heat transformer operating with the water-lithium bromide mixture. A mathematical model was developed to estimate the coefficient of performance (COP), the exergy coefficient of performance (ECOP), the total exergy destruction in the system (C TD ) and the exergy destruction (C D ) in each one of the main components, as a function of the system temperatures, the efficiency of the economizer (EF EC ), the gross temperature lift and flow ratio (FR). The results showed that the generator is the component with the highest irreversibilities or exergy destruction contributing to about 40% of the total exergy destruction in the whole system, reason why this component should be carefully designed and optimized. The results also showed that the COP and ECOP increase with increase in the generator, the evaporator and the absorber-evaporator temperatures and decrease with the absorber and condenser temperatures. Finally, it was observed that the COP and ECOP are very dependent of the FR and the economizer efficiency (EF EC ) values. Also the optimum operating region of the analyzed system is shown in the present study.

Modeling and analysis of energetic and exergetic efficiencies of a LiBr/H20 absorption heat storage system for solar space heating in buildings

“…Improved cycle with a solution heat exchanger As in absorption refrigeration machines (Martínez and Rivera 2009) and as already mentioned in the analyses of the basis cycle, the SHX (Fig. 10) could increase the system's energetic and exergetic performances.…”

“…During the discharging phase, the exergy is mainly destroyed in the solution tank and the absorber. Like in absorption refrigeration machines (Aprhornratana and Eames 1995;Arora and Kaushik 2009;Gebreslassie et al 2010;Izquierdo et al 2000;Kaushik and Arora 2009;Martínez and Rivera 2009;Morosuk and Tsatsaronis 2008;Şencan et al 2005), the generator and the absorber of the absorption heat storage system are responsible of a large part of the exergy destruction. However, because of the expansion and the mixing of the solution in the solution tank, this component is responsible for most of the exergy destruction in this absorption heat storage system.…”

“…It is a useful tool to specify the location and to highlight the causes of thermodynamic irreversibilities. Numerous combined energetic and exergetic analyses have been reported for lithium bromide/water absorption refrigeration systems, among which (Aprhornratana and Eames 1995;Arora and Kaushik 2009;Gebreslassie et al 2010;Izquierdo et al 2000;Kaushik and Arora 2009;Martínez and Rivera 2009;Morosuk and Tsatsaronis 2008;Şencan et al 2005). These studies highlight that in absorption refrigeration systems the irreversibilities are mainly located in the generator and in the absorber.…”

Optimum performance of a double absorption heat transformer

“…Two-stage AHTs can obtain GTL as high as 80°C with COP around 0.36. The double absorption heat transformers (DAHT) which can achieve similar thermodynamics performance and require fewer components seemed to be a better alternative [12][13][14].…”

Energy and exergy analysis of an experimental single-stage heat transformer operating with the water/lithium bromide mixture

“…The results showed good accuracy between the training data and the output results. Martı´nez and Rivera [28] analyzed the theoretical performance of a doubleabsorption heat transformer reporting values of exergy coefficients of performance (COP) and irreversibilities for the whole system and the main components. As can be seen from the literature review, it is clear that there are not complete exergy studies based on the experimental performance of absorption single-stage heat transformers, because of this, in the present study, a detailed analysis is presented for the experimental heat transformer operating with the water/lithium bromide mixture.…”