Heat pumps, industrial processes, energy efficiency, exergy efficiency
Industrial processes may use heat pumps to recover low grade heat or to combine heating and cooling needs. In many cases, this technology leads to reduced energy consumption and greenhouse gases emissions. In this paper, a methodology, based on exergy analysis of heat sources and heat sinks, helping in optimizing industrial heat pumps design is presented. The optimization variables are: the refrigerant choice (pure fluid, azeotropic mixture, non azeotropic mixture), the thermodynamic state of the refrigerant (subcritical, supercritical) and the architecture of the heat pump (heat pump in reverse series). The heat pump is modelled in Modelica language: "pinch" method is used to model the heat exchangers and the compressor model is based on an isentropic efficiency assumption. The objective function is the maximization of the exergy efficiency. Genetic algorithm is used to perform the optimisation. The methodology is applied on a case study of an industrial process where a fluid is heated from 60°C to more than 120°C, and industrial effluents are available at 50°C.