First and second law investigation of waste heat based combined power and ejector-absorption refrigeration cycle

In the proposed cogeneration cycle, a LiBr–H2O absorption refrigeration system is employed to the combined power and ejector refrigeration system which uses R141b as a working fluid. Estimates for irreversibilities of individual components of the cycle lead to possible measures for performance improvement. Results of exergy distribution of waste heat in the cycle show that around 53.6% of the total input exergy is destroyed due to irreversibilities in the components, 22.7% is available as a useful exergy output, and 23.7% is exhaust exergy lost to the environment, whereas energy distribution shows 44% is exhaust energy and 19.7% is useful energy output. Results also show that proposed cogeneration cycle yields much better thermal and exergy efficiencies than the previously investigated combined power and ejector cooling cycle. Current investigation clearly show that the second law analysis is quantitatively visualizes losses within a cycle and gives clear trends for optimization.

► Proposed cycle provides a significant increased in thermal and exergy efficiency. ► The exergy of exhaust gases from the cogeneration cycle is 21.3% less than the energy of exhaust gases. ► Increase in turbine inlet pressure, turbine back pressure and ejector evaporator temperature gives a sharp increase in exergy efficiency of the proposed cycle.