有限热源吸收式制冷机的热力学建模与分析

THERMODYNAMIC MODELING AND ANALYSIS OF AN IRREVERSIBLE ABSORPTION CHILLER WITH FINITE HEAT CAPACITIES

考虑了有限热容、有限速率传热以及工质内部耗散的影响,建立了吸收式制冷机的热力学模型。在该模型中,吸收式制冷机被等价为一个不可逆卡诺热机驱动不可逆卡诺制冷机的联合循环系统。为描述循环的内不可逆性,引入了两个内不可逆性参数I_(he)和I_r。其中,I_(he)用于描述热机循环的内不可逆性,I_r用于描述制冷循环的内不可逆性。通过对给定供热率下热机热效率和给定制冷率下两热源制冷机性能系数解析表达式的推导,并根据等价系统的定义,获得了吸收式制冷机给定制冷率下性能系数的解析表达式,利用该表达式详细地分析了各参数对性能系数的影响。所得公式和分析结论对实际系统的理解、设计以及分析具有一定的理论指导作用。

A thermodynamic model for an irreversible absorption chiller was presented, in which not only the irreversibilities of finite-rate heat transfer and internal dissipations of the working fluid were considered, but also the effects of finite heat capacities on the system performance were considered, An absorption chiller was treated as a combined cycle system of an irreversible Carnot heat engine driving an irreversible Carnot chiller in this model. Two internal irreversibility parameters Ihe and Ir were introduced to characterize the irreversibility inside the cycle （say, Ihe is for the heat engine cycle and lr is for the refrigeration cycle）. First, the analytical expressions for the thermal efficiency of the heat engine under a given heating rate and the coefficient of performance （COP） of the two-heat-source chiller under a given cooling rate were derived, and then the analytical expression for the COP of the absorption chiller under a given cooling rate was obtained in term of the definition of the equivalent system. A detailed parametric study was performed to analyze their effects on the COP. The formulas and analytical conclusions obtained here provide a useful theoretical guide to the comprehension, design and analysis of a real absorption chiller.