Abstract
This paper provides an illustrated description of a proposed LiBr-H2O vapour absorption refrigerator which uses a thermally activated solution pumping mechanism that combines controlled variations in generator vapour pressure with changes it produces in static-head pressure difference to circulate the absorbent solution between the generator and absorber vessels. The proposed system is different and potentially more efficient than a bubble pump system previously proposed and avoids the need for an electrically powered circulation pump found in most conventional LiBr absorption refrigerators. The paper goes on to provide a sample set of calculations that show that the coefficient of performance values of the proposed cycle are similar to those found for conventional cycles. The theoretical results compare favourably with some preliminary experimental results, which are also presented for the first time in this paper. The paper ends by proposing an outline design for an innovative steam valve, which is a key component needed to control the solution pumping mechanism.
Highlights
The use of thermally activated refrigerators has the potential to reduce CO2 and other damaging emissions
A drawback to the wider use of LiBr-H2 O absorption refrigerators has been their relatively high capital cost compared to electric vapour compression machines with similar cooling capacities
A significant contribution to the capital cost of small-scale, sub-kilowatt, absorption refrigerators is thought to be that of the solution recirculation pump
Summary
The use of thermally activated refrigerators has the potential to reduce CO2 and other damaging emissions. The idea of using a thermo-syphon effect instead of a bubble pump to circulate the solution between the generator and absorber of an absorption cycle heat transformer system was investigated by Abrahamsson, Gidner and Jernqvist [16]. They described an experimental study of a 10 kW NH3 -H2 O absorption heat transformer incorporating a self-circulation mechanism based on the thermo-syphon principle. For reasons which were not clear, the action of the automatic steam valve, described and discussed, was reversed This resulted in incurring significant sensible heating losses as the solution in the generator needed to cool to ambient conditions between each pumping cycle. The results of the research are discussed and the design of an automatic steam valve, a key component, is outlined
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