The Simulation And Optimization Of The Thermodynamic Process Of The LiBr-H₂O Double Absorption Heat Transformer

It becomes more and more important to reuse industrial waste energy and to protect human environment now. The technology of absorption heat transformer (AHT) is one of the most effective ways to simutenaeously solve these two proposed problems especially using lithium bromide-water solution as working fluid. Not only can a large quantity of waste heat in the form of hot water or steam be reused, but also the thermal pollution discharged to the enviroment will decrease if this saving energy device is applied. The single AHT has been applied widely in the past years. Due to its temperature-upgrade is only about 30C, its application is limited in some cases which need large temperature-upgrade. Double AHT (DAHT) is a new type of AHT which can realize more than 60C temperature-upgrade. As a result, much more attention is payed to the later one in very recent years.In this paper, based on the first and the second law of thermodynamics, the thermodynamic circuit process performance as well as the economic benefit of the double absorption heat transformer (DAHT) is analyzed and optimized theoretically in detail by introducing a set of mass conservation, heat conservation equations and some thermodynamic data of the lithium bromide-water solution. Furthermore, in order to simulate and optimize both the thermodynamic performance and economic profit of the DAHT, a coumputer program and its subroutines describing and simulating the solution thermodynamic circuit of the DAHT are coded. The simulating and optimizing results caculated by the computer programs are illustrated graphically in a series of analytical diagrams. At the same time, these results are used to discuss, under various working conditions, the influence of the change of some operating parameters such as the temperature of condenser (7c), evaporator (Te), absorber (Tab), generator (Tg) on the coefficient of performance (COP), the exergy coefficient of performance (ECOP), the new coefficient of performance (COP-AT), the new exergy coefficient of performance (ECOP T) and the index of exergy (El). The laws of their change also have been demonstrated.Finally, the total economic profit (EP) of the thermodynamic precess of this type of DAHT is optimized by using a restricting complex method of N dimensions. The optimizing results caculated are presented in a table. Consequently, when Tc is 20.35C, TE is 73.05C and Tab is 129.52C, the total economic profit will attain the optimal value.