Heating load and COP optimizations for a class of generalized irreversible universal steady-flow variable-temperature heat reservoir heat pump cycle model

Abstract

The heating load and coefficient of performance (COP) of a class of generalized irreversible universal steady-flow heat pump cycle model with variable-temperature heat reservoirs and the losses of heat transfer, heat leakage and internal irreversibility are investigated by using the theory of finite-time thermodynamics. The universal heat pump cycle model consists of two heat-absorbing branches, two heat-releasing branches and two adiabatic branches. Expressions of heating load and COP of the universal heat pump cycle model are deduced, respectively. By means of numerical calculations, the heat conductance distributions between hot- and cold-side heat exchangers are optimized by taking the maximum heating load as objective. There exist both optimal heat conductance distributions and optimal thermal capacity rate matching between the working fluid and heat reservoirs which lead to the double maximum heating load. The effects of heat leakage, internal irreversibility, total heat exchanger inventory and thermal capacity rate of the working fluid on the optimal performance of the cycle are discussed in detail. The results obtained herein include the optimal performance of endoreversible and irreversible, constant- and variable-temperature heat reservoir Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles. The results obtained can provide some theoretical guidelines for the designs and operations of practical heat pumps.