Energy and exergy analysis of vapor compression–triple effect absorption cascade refrigeration system

Abstract

In the present work, an absorption-compression cascade refrigeration system (ACCRS) has been analyzed theoretically for low temperature cooling applications. It comprises of a triple effect H2O-LiBr series flow vapor absorption refrigeration system in higher temperature section associated with vapor compression refrigeration (VCR) system using R1234yf refrigerant in lower temperature section. The cascade system provides lower temperature i.e. 223.15–263.15 K for freeze drying, pharmaceuticals, chemical and petroleum industry at lower running cost using waste available from the exhaust of gas turbine or steam turbine to run the triple effect vapor absorption refrigeration system which reduces the overall high grade energy (electricity) consumption of the cascade system. Moreover, the use of R1234yf protects the environment from global warming and ozone depletion. Energetic and exergetic analysis have been performed for the parametric investigation of the system. An EES software based computational model has been formulated for the computation of performance parameters. The analysis determines the effect of generator temperature (448.15–473.15 K), absorber temperature (298.15–313.15 K) and evaporator temperature (223.15–263.15 K) on the energetic (COP) and exergetic (exergetic-efficiency, exergy destruction rate and exergy destruction ratio performances of the system. The results illustrate that the electricity savings of triple effect cascade system are 45.84% in comparison to conventional VCR cycle. The COP and exergetic-efficiency of VCR circuit in the cascade system boost up by 85.26% and 85.28% respectively. The COP and exergetic efficiency of triple effect cascade system are higher than that of single and double effect absorption compression cascade refrigeration systems. The system circulation pump and absorber are the sites of lowest and highest irreversibility in comparison to the other system components.