Thermoeconomic evaluation and optimization of LiBr-H2O double absorption heat transformer driven by flat plate collector

Abstract

In this paper, a solar double absorption heat transformer (SDAHT) operating with the LiBr-H2O solution is proposed to provide high temperature energy. The flat plate collector (FPC) is used to supply the demanded heat input in the present configuration, which will greatly broaden the application scope of the FPCs. The thermoeconomic concept is applied to the evaluation and optimization of the SDAHT, aimed at minimizing its annual capital cost per kilowatt heat capacity (CPK) and payback period (PP). A dedicated computer model in the software Engineering Equation Solver was developed to conduct the study by means of a parametric analysis. The results show that there exists an optimum absorber/evaporator temperature at which CPK and PP can obtain the minimum values. With solar radiation intensity at 600 W/m2, generation (evaporation) temperature at 75 °C, condensation temperature at 38 °C, absorption temperature at 135 °C and economizer efficiency set to 0.8, the optimum absorber/evaporator temperature and corresponding CPK and PP are 104.0 °C, 928.1 euros/kW and 4.0 years, respectively. The cost of the FPCs takes the major part of CPK. Moreover, the effects of the operating parameters such as the generation (evaporation), condensation, absorption temperatures and design parameters including the first and second economizer efficiencies on the optimum absorber/evaporator temperature and corresponding CPK and PP have been analyzed in detail. Besides, some suggestions derived from the results are also given to assist the engineers in estimation of the economic performance.