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

Abstract

SUMMARYThe first and second law of thermodynamics have been used to analyze the performance of an experimental single-stage heat transformer operating with the water/lithium bromide mixture. Enthalpy coefficients of performance (COP), external coefficients of performance (COP EXT ), exergy coefficient of performance (ECOP), exergy destruction or irreversibility in the system and components (I) and the improvement potential (Pot) have been calculated against the gross temperature lift and the main operating temperatures of the system. The results showed that the highest COP, COP EXT and ECOP values are obtained at the highest solution concentrations meanwhile the Pot and the I of the cycle remain almost constant against these parameters. Also it was shown that the COP, COP EXT and ECOP decrease with an increase with the absorber temperature, meanwhile the Pot and the I increase. Moreover, it was observed that in all the cases independently of the operating temperatures of the system, the absorber accounts with most of the half of the total irreversibility in the system. Finally, it was shown that the improvement potential is considerable for the system.

Thermoeconomic optimization of LiBr/H2O-R134a compression-absorption cascade refrigeration cycle

“…Although the main aim of this study is to find out global optimum value of the cycle but also some of our studies have been carried out, in order to understand the variation of aim functions of the system with different working temperatures (T 3, T 5, T 8 , and T 12) , different solution heat exchanger effectiveness and isentropic efficiency of compressors. LiBr is a salt, and it has a crystalline structure in its solid state.…”

“…Related costs in Eq. (12) can be written as [17]: For the base case, the cost flow rates [C ($ h À1 )] and cost per exergy unit [c ($ GJ À1 )] for each stream of the system that are presented in Table 3.…”

“…Rivera et al [12] carried out first and second law thermodynamic analyses of an experimental single-stage heat transformer operating with the water/LiBr mixture. The results showed that the highest COP, external COP and ECOP values were obtained at the highest solution concentrations (59%) meanwhile the improvement potential of the cycle and irreversibility remain almost constant against this parameter.…”

Recycling waste heat energy using vapour absorption heat transformers: A review

“…Siqueiros and Romero [17] demonstrated that by raising the evaporator temperature by 1 1C the COP of the cycle can be increased by up to 78%, while a 2 1C augmentation in the heat source temperature can result in an increase in the COP of up to 121%. To the author's best knowledge, the only SSHT publication to contradict any of the above trends was presented by Rivera et al [18], who found that their experimental COP decreased with an increase in the evaporator temperature. No analysis was provided regarding possible reasons for this deviation.…”

“…Rivera et al [18] demonstrated experimentally that the absorber accounts for half of the total irreversibility followed by the condenser and the generator whose exergetic efficiencies are shown to be similar. Rivera et al [24] similarly attributed 30% of the irreversibility to the absorber, followed by the condenser.…”