Internal energy and exergy recovery in high temperature application absorption heat transformers
Abstract In this paper, the design of a triple absorption heat transformer (TAHT) using the working fluids water and lithium bromide is dissected and reassembled using heat exchange network modelling in order to determine the optimum number and locations of internal heat exchange units within the system. It is found that the conventional design of the TAHT does not employ heat exchangers effectively, and that thus by rearranging these units system COP may be increased by 11.7% while exergy destruction within the system (its irreversibility) can be reduced by 21%. Strategically adding an extra one or two heat exchangers increases the COP by 16.4% and 18.8% while decreasing exergy destruction by 28% and 31.5% respectively compared to a conventional TAHT design.
Simulation and optimization of novel configurations of triple absorption heat transformers integrated to a water desalination system
Abstract A thermodynamic analysis of six different configurations of triple absorption heat transformer systems (TAHTs) utilizing H2O/LiBr as the working pair which is integrated into water desalination systems is conducted in this study. The energy source of the desalination system is provided by the high temperature heat of the absorbers of TAHTs by utilizing the waste heat from a textile factory. A computer program is developed in the EES (Engineering Equation Solver) to study the performance of the system such as; COP, ECOP, distilled water, and absorber utilized heat, and also to optimize them in six different configurations. It is shown that modified configurations of TAHTs can increase the COP and fresh water productivity rather than that of conventional systems. The results indicated that the optimized amount of distilled water produced by the last configuration which is 0.1307 kg/s can supply 1131 residential units.
Effects of reservoir volume on performance of pulse tube cooler.
A pulse tube cooler has the advantages of long-life and low-vibration over conventional cryocoolers such as G-M and Stirling coolers because of the absence of moving parts at low temperature. On the other hand, the combination of a reservoir and orifice is indispensable to optimize the performance of pulse tube coolers. In order to make the pulse tube cooler compact for practical applications, the volume of reservoir should be minimized. This paper analyzes the effects of the reservoir volume on the thermodynamic performance of various components in a simple orifice and a double-inlet pulse tube cooler by combining a linearized model with a thermodynamic analysis. Expressions of entropy production for those components are presented. The results show that the reservoir volume has a significant influence on the entropy production in the various components when the reservoir to pulse tube volume ratio is smaller than about 5. The ratio is important to determine the minimum reservoir volume for a pulse tube cooler. Optimum settings for a double-inlet pulse tube cooler are also discussed.