Heating load, COP, exergy loss rate, exergy output rate and ecological analyses and optimisations for irreversible universal steady flow variable temperature heat reservoir heat pump cycle model

摘要

The performance of an irreversible universal steady flow heat pump cycle model with variable temperature heat reservoirs is analysed and optimised by using finite time thermodynamics. The universal heat pump cycle consists of two heat absorbing branches, two heat releasing branches and two irreversible adiabatic branches, with the losses of heat resistance and internal irreversibility. Expressions of heating load, coefficient of performance (COP), exergy output rate, exergy loss rate and ecological function of Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles are derived. There exists an optimal heat conductance distribution and an optimal thermal capacity rate matching between the working fluid and heat reservoir which leads to maximum heating load, maximum exergy output rate and maximum ecological function respectively. Performance comparisons among heating load, COP, exergy output rate, exergy loss rate and ecological function objectives are carried out. The effects of the internal irreversibility, heat capacity ratio of the heat reservoirs and inlet heating fluid temperature of the cold side heat reservoir on the optimal performances of the universal heat pump cycle are discussed. The results obtained include the performance characteristics of endoreversible and irreversible, constant and variable temperature heat reservoir steady flow Brayton, Otto, Diesel, Atkinson, Dual, Miller and Carnot heat pump cycles.