An optimal design method for a heat exchanger for a dual-stage circulating high-temperature heat pump system

This paper presents an optimal design method for heat exchangers in a dual-stage circulating high-temperature heat pump (HTHP) system. The paper first presents a series of steady-state models of components and a simulation platform of whole system; the output of the simulated system is verified by the operational data of a real heat pump plant. The method is investigated and implemented by the simulation platform based on these models, and it consists of four steps: 1) the selection of an optimal condenser and evaporator (the C-E plant), 2) the optimization of the total heat transfer area of the C-E plant, 3) the optimization of the condenser-to-evaporator heat transfer area ratio (AR) and 4) a matching scheme for the AR and heat transfer area of the regenerator. The method adopts the coefficient of performance (COP) as the optimization target and employs the heating capacity, water velocities and water-side pressure drops and the compressor discharge temperature as constraints. The case studies demonstrate that the presented method is effective at solving the problem of mismatches among single components. The optimal design scheme provides the same heating capacity with a 13% decrease in the total area of the exchangers.