Development of a novel cogeneration system by combing organic rankine cycle and heat pump cycle for waste heat recovery

This paper presents a competitive cogeneration system, which combines the organic Rankine cycle with the heat pump cycle through a"built-in"evaporator. With this innovative structure, the input waste heat temperature in both the sub-cycles can simultaneously be maintained at a high level. The optimal working fluid is screened. Energy and economic advantages of the proposed system are proven. Moreover, the influence of main thermodynamic parameters on system performance is investigated. The results indicate that, compared with the traditional system, the thermal efficiency and waste heat recovery efficiency of the proposed system using the "built-in" evaporator increased by 6.4% and 1.2%, respectively. Meanwhile, it can be found that the thermal efficiency of the proposed system increased linearly, while the waste heat recovery efficiency showed a variation that followed a quadratic function with the increase of evaporation temperature. The peak value of the waste heat recovery efficiency was 9.9% for the evaporation temperature of 335 K. Moreover, the exergy performance of the system was very sensitive to the variation of evaporation temperature. An increase of 24 K in the evaporation temperature resulted in a drop in total exergy losses of nearly 76%, which resulted in an increase in the system exergy efficiency by about 27%. (C) 2020 Elsevier Ltd. All rights reserved.