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.
Energy and exergy analyses on the off-design performance of an absorption heat transformer
Abstract Absorption heat transformers (AHTs) have great potential in utilization of low-level heat sources, such as industrial waste heat. However, the operation of an AHT is limited by heat sources, customer load, and cooling water. However, such conditions may change in practical applications. Thus, research on the off-design performance of an AHT is important and necessary. In this paper, mathematical models for the cycle and components of a vertical falling film AHT operating with water/lithium bromide solution were developed. The coefficient of performance, output heat capacity, and exergy efficiency were used to evaluate the performance of the AHT. Furthermore, the exergy loss distribution diagrams under off-design conditions were carried out, and the exergy loss ratio was decomposed into several factors to determine why exergy loss ratio varies under off-design conditions. Finally, exergy loss ratio in the solution heat exchanger plays an important role under off-design conditions, which is analyzed thoroughly. A kind of effective adjustment is studied and proven to be effective in improving the performance of the AHT. The present work provides a tool for thoroughly understanding the mechanism of performance change in the AHT under off-design conditions.
Molecular diversity of skin mucus lectins in fish.
Among lectins in the skin mucus of fish, primary structures of four different types of lectin have been determined. Congerin from the conger eel Conger myriaster and AJL-1 from the Japanese eel Anguilla japonica were identified as galectin, characterized by its specific binding to beta-galactoside. Eel has additionally a unique lectin, AJL-2, which has a highly conserved sequence of C-type lectins but displays Ca(2+)-independent activity. This is rational because the lectin exerts its function on the cutaneous surface, which is exposed to a Ca(2+) scarce environment when the eel is in fresh water. The third type lectin is pufflectin, a mannose specific lectin in the skin mucus of pufferfish Takifugu rubripes. This lectin showed no sequence similarity with any known animal lectins but, surprisingly, shares sequence homology with mannose-binding lectins of monocotyledonous plants. The fourth lectin was found in the ponyfish Leiognathus nuchalis and exhibits homology with rhamnose-binding lectins known in eggs of some fish species. These lectins, except ponyfish lectin, showed agglutination of certain bacteria. In addition, pufflectin was found to bind to a parasitic trematode, Heterobothrium okamotoi. Taken together, these results demonstrate that skin mucus lectins in fish have wide molecular diversity.