Abstract
Three single-stage absorption heat transformer (SSHT) configurations are modeled, analyzed and compared from the viewpoints of thermodynamics and economics, using the Engineering Equation Solver (EES) software. In addition, a multi-objective optimization is carried out for the three configurations to specify the optimal design point considering the second law efficiency and the product unit cost as two objective functions. The configurations differ from one another considering the number of heat exchangers used in them. The results show that the coefficient of performance (COP) and exergy coefficient of performance (ECOP) for configuration 3 are around 35% and 30% higher than the corresponding values for configuration 1, respectively. Also, configuration 2 is found to be more economic with a product unit cost of about 21% and 5% lower than those for configurations 1 and 3, respectively. Furthermore, it is observed that relatively higher absorber temperatures can be achieved by configurations 2 and 3 compared to configuration 1. It is concluded from the multi-objective optimization that the conditions at which the evaporator, condenser and absorber temperatures are 86.51 °C, 39.03 °C and 123.1 °C, respectively, represents an optimal solution.
Highlights
In today’s industrial societies, many thermal resources and plants release large amounts of low-temperature waste heat to the environment at a temperature range of 60–100 ◦ C [1]
Absorption heat transformers (AHTs), which operate in a cycle opposite to that of absorption heat pumps (AHPs), are capable of raising the temperature of low or moderate-temperature waste heat sources
They showed that coefficient of performance (COP) and exergy coefficient of performance (ECOP) in the studied systems are improved by using an ejector located at the absorber inlet
Summary
In today’s industrial societies, many thermal resources and plants release large amounts of low-temperature waste heat to the environment at a temperature range of 60–100 ◦ C [1]. Rivera et al investigated experimentally the exergy performance of a single-stage absorption heat transformer operating with water/lithium. Siqueiros and Romero and Romero et al tried to improve the COP of an absorption heat transformer used for water purification [10,11] They demonstrated that a higher value of COP is obtained when only the evaporator and generator temperatures are increased. Horuz and Kurt studied computationally the effects of condenser, evaporator and generator temperatures on the COP and absorber heat capacity of four configurations of AHT systems [1]. Demonstrated that the ECOP (exergy coefficient of performance) of a single-stage absorption heat transformer (SSHT) shows similar trends to the COP and increases with increasing evaporator and generator temperatures before decreasing, and increases with decreasing condenser temperature [17,18].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
