The equivalent low-dissipation combined cycle system and optimal analyses of a class of thermally driven heat pumps

Abstract

The performance characteristics, operation, and design strategies of a class of thermally driven heat pumps are investigated due to their important roles in the efficient utilization of low-grade thermal energy. In order to establish a more generic thermodynamic model of thermally driven heat pumps mainly including absorption, adsorption, and ejector heat pumps, low-dissipation assumption is adopted. Accordingly, the associated dissipation parameters accounting for the specific information on the irreversibilities in each heat-transfer process are introduced rather than specifying heat-transfer law. Based on the proposed model, the theoretical results of the coefficient of performance and heat load are derived with regard to two key parameters denoting the size ratio of the two involved subsystems and the matching deviation from reversible limit. The performance characteristics and the optimally operating regions of the whole system are determined and the differences between thermally driven heat pump and refrigerator are highlighted. The proposed model and obtained results further develop the low-dissipation model and may provide a useful description for the operation and design of practical thermally driven heat pumps.

Comparative Assessment of Various Low-Dissipation Combined Models for Three-Terminal Heat Pump Systems

“…The application of low-dissipation assumption for the thermodynamic devices operating between chemical potential reservoirs have been discussed by Refs. [ 15 , 34 ]. Therefore, the details of the extensions will not be given for saving the length in the present paper.…”

“…However, multi-terminal thermodynamic systems play the important roles in the utilization of low-grade energies [ 27 , 28 , 29 , 30 ] and the energy resources at microscopic scale [ 31 , 32 ]. In this regard, the low-dissipation assumption has been used to construct the combined cycle models of thermally driven refrigerator and heat pump by considering the constraint of reversible entropies inside two subsystems in the last two years [ 33 , 34 ], which obtains the bounds of the COP at maximum cooling power and heating load for the first time and extends the application scope of low-dissipation model to multi-terminal thermodynamic systems.…”

Performance Analysis and Four-Objective Optimization of an Irreversible Rectangular Cycle

“…Some scholars have introduced finite time thermodynamics theory into the performance analyses of the RC on this basis. Considering that the specific heats (SHs) of the working fluid (WF) were constants, Liu et al [ 18 ] derived the work output and TEF of an endoreversible RC. Based on [ 23 ], Liu et al [ 24 ] analyzed the influences of heat transfer loss and friction loss on the power output (POW) and TEF of an irreversible RC.…”

“…After decades of development, a series of instructive and practical achievements have been obtained in finite time thermodynamics [1][2][3][4][5][6][7][8], the research objects of which include heat engines [9][10][11][12][13][14][15], refrigerators [16,17], heat pumps [18], chemical cycles [19], and quantum cycles [20,21]. The rectangular cycle (RC) is composed of four thermodynamic processes, its endothermic processes are closed to the endothermic processes of the dual cycle, and its exothermic processes are closed to the exothermic processes of the Miller cycle.…”

“…Some scholars have introduced finite time thermodynamics theory into the performance analyses of the RC on this basis. Considering that the specific heats (SHs) of the working fluid (WF) were constants, Liu et al [18] derived the work output and TEF of an endoreversible RC. Based on [23], Liu et al [24] analyzed the influences of heat transfer loss and friction loss on the power output (POW) and TEF of an irreversible On the basis of the irreversible RC model with constant SH of WF built in [24], this paper will firstly obtain the analytical expressions of cycle PD and effective power by using finite time thermodynamics theory and compare the performance differences of the cycle under the conditions of the maximum PD, maximum effective power, and maximum POW; secondly carry out MOO for the dimensionless POW, TEF, dimensionless PD, and dimensionless effective power by taking the cycle expansion ratio as the optimization variable and applying the NSGA-II; and finally obtain the optimal solutions of four-objective, three-objective, and two-objective optimizations by using three decision-making methods.…”