Polybranched regenerative GAX cooling cycles

Abstract

After a short characterization of today's advanced absorption cooling systems, of multi-effect and generator-absorber heat exchange (GAX) type, this work introduces polybranched regenerative GAX cycles (PBR(GAX)). They combine the advantages of four cycles: GAX, branched GAX, regenerative GAX, and those with rectification heat recovery. The general case of n-stage PBR, working with volatile or non-volatile absorbents, is thermodynamically modelled. The model is applied to cycles with one to three stages working with the NH 3 H 2 O LiBr combination, selected according to a special criterion, which has in view to maximize the GAX effect. The thermal match in the GAX device is verified using our own complete algorithm. The results highlight the net superiority of the cooling COP of PBR relative to any other published GAX or multi-effect cycles. Compared with those with vapour exchange, operated with NH 3 H 2 O , one of the best GAX cycles till now, a three-stage PBR has 1.25–1.9 times higher COP values and represents 71–82% of the Carnot cooling efficiency for lifts varying between 68 and 47°C. The PBR cycles are capable of simultaneously delivering cold and warm water, at 50–70°C. Compared with a double-effect cycle, provided with rectification heat recovery, a two-stage PBR is constructively simpler and thermally with about 40% more performance.