Thermoeconomic optimisation of the condenser in a vapour compression heat pump

In the paper, the design optimisation of a heat exchanger is discussed, using a thermoeconomic approach. The investigation is referred to the tube-in-tube condenser of a conventional vapour-compression heat pump, with a two-phase refrigerant flowing in the inner tube and a single-phase fluid flowing in the annulus. A cost function to be minimised is introduced, defined as the sum of two contributions: (i) the amortisation cost of the condenser, related to the heat exchange area; (ii) the operating cost of the electric-driven heat pump in which the heat exchanger will work, depending on the overall exergy destruction rate in the system. In the paper, this latter contribution is related to the local irreversibility rate in the condenser, using the so-called structural approach. The optimal trade-off between amortisation and operating cost is therefore investigated, by minimising the above-mentioned cost function. A numerical example is discussed, in which, for a commercial heat exchanger, the design improvements needed to obtain a cost-optimal configuration are investigated. The analysis is carried out for three different refrigerants: R22, R134a and R410A.