TFE/E181吸收式制冷机热力学性能研究

Thermodynamic investigation of the TFE/E181 absorptive type refrigerator

吸收式制冷机在工业余热回收利用中有非常广泛的应用前景,能有效改善因工业生产造成的热污染。从热力学定律和火积效率定义出发,介绍了吸收式制冷机的工作原理,并在质量和能量守恒定律基础上设计了吸收制冷机各部件的数学模型。在建立的热力学方程中,有5个假定:1)系统在稳态和热平衡条件下运行;2)各部件的热损和压降可以忽略不计;3)离开发生器和吸收器的溶液是饱和的;4)发生器出口蒸汽是纯工质,且离开发生器的稀溶液是平衡的;5)节流阀前后是等熵过程。研究了各个系统参数随火积效率(G*)的变化趋势。结果表明,当发生温度不变时,蒸发温度、制冷量、放气范围和系统COP随火积效率的增加而增加,而系统循环比、泵功和系统火用效率随之下降;如果火积效率一定,蒸发温度、制冷量、放气范围和系统COP随发生温度的增加而增加,系统循环比、泵功和系统火用效率则随之下降。因此,在吸收制冷机中,可以通过改变火积效率G*来改善系统性能。

The paper is aimed to present the results of our thermody namic investigation of the TFE/E181 absorptive type refrigerator, which is well accepted for industrial waste heat recovery due to its ef ficiency in reducing the thermal pollution caused by industrial produc tion. For our research purpose, we have investigated the said refrig erator from the point of view of the working principle of the thermody namics and the definition of entransy efficiency. Furthermore, wehave also developed a mathematical model on the balance between the mass and the energy for all the components of the absorptive refrigera tion. To be brief, the thermodynamic equations of the system model we would like to discuss are based on the following five assumptions： （ 1 ） the refrigeration system is founded on the steadfast state and heat balance conditions; （2） the thermal loss and the pressure drop can be neglected in various components; （3） the solution can be found saturated while leaving the absorber and the generator; （4） the vapor at the exit of the generator can be taken as a pure refrigerant and in equilibrium with the weak solution leaving the generator; （5） the ex pansion done through the throttle valve can be thought as being isen thalpic. In so doing, we can obtain the curves of different operation parameters with the change of the entransy efficiency （ G ）. From the curve graphics, it is possible to deduce that, while keeping the heatgenerating temperature constant, the higher the entransy effi ciency is, the higher the evaporating temperature, the cooling capaci ty, the deflation ratio and COP would be. However, the circulation ratio, pump work and the energy efficiency would be reduced with the increase of G . Nevertheless, on the condition that the entransy effi ciency is fixed, the variation of such parameters as the evaporating temperature, the cooling capacity, the deflation ratio as well as COP would enjoy the same tendency with the generating temperature. Meanwhile, the other parameters, such as the circulation ratio, pump work and the energy efficiency, would be reduced with the increase of the generating temperature. Thus, we can arrive at a conclusion that, with the absorptive refrigeration being certain, it would be possible to improve the system performance by altering the entransy efficiency G . Thus this research will be able to provide a theoretical base for optimizing the TFE/E181 absorption refrigeration.