On the pressure drop in Plate Heat Exchangers used as desorbers in absorption chillers

Abstract

a b s t r a c tThe influence of the pressure drop in Plate Heat Exchangers (PHE) in the boiling temperature of LiBr H 2 O and NH 3 H 2 O solutions is studied. For the NH 3 H 2 O solution, the pressure drop temperature saturation relationship estates that high pressure drops can be allowed in the solution with negligible changes in the saturation temperature, and in the PHE performance. Besides, in the case of the LiBr H 2 O solution, as the working pressure is usually very low, the analysis of the pressure drop must be taken as a main limiting parameter for the use of Plate Heat Exchangers as vapour generators. In this case, the pressure drop may considerably change the boiling temperature of the solution entering the heat exchanger and therefore a higher heating fluid temperature may be required. A guideline to design these systems is proposed.

Parametric study of operating and design variables on the performance of a membrane-based absorber

“…However, its generalisation remains limited for small cooling power applications. One of the main constraints for the development of small air conditioning units using H 2O-LiBr absorption chillers is the size required, which is still, by far, larger than the size of the conventional mechanical compression systems: volume to refrigeration power ratio in single effect absorption chillers is in the order of 0.04 m 3 /kW, without considering the volume occupied by the cooling system, for refrigeration capacities between 10 and 30 kW, whereas mechanical compressor systems can have a ratio equal to 0.02 m 3 /kW for the same range of refrigeration capacities (García-Hernando et al [1]). In order to increase the cooling capacity to volume ratio in absorption systems new absorber designs have been investigated based in changes in the vapour-solution interface configuration by means of bubbles, sprays and droplets, liquid jets and sheets, etc.…”

A simple model to predict the performance of a H2O–LiBr absorber operating with a microporous membrane

“…Nevertheless, their use is limited, compared to mechanical refrig eration systems, because they are generally larger in size, limiting to a great extend their use in low and medium power applications. For instance, a typical value for the volume to refrigeration power ratio in single effect absorption chillers is in the order of 0.04 m 3 / kW (without considering the volume occupied by the cooling system) for refrigeration capacities between 10 and 30 kW, whereas mechanical compressor systems can have a ratio equal to 0.02 m 3 /kW for the same range of refrigeration capacities (García Hernando et al [1]). …”

“…Venegas, M.; Vega, M.; García-Hernando, N.; Ruiz-Rivas, U. (2016) A microporous membrane is used in combination with rectangular microchannels in the absorber of an absorption chiller with the aim of reducing the size of this cooling technology.…”

Flow boiling and frictional pressure gradients in plate heat exchangers. Part 1: Review and experimental database

“…In still other studies, the boiling characteristics of several other solutions and binary mixtures in PHEs were evaluated for LiBr -H 2 O and NH 3 -H 2 O by Garcia-Hernandoa et al (2011b), NH 3 -LiNO 3 and NH 3 -NaSCN solutions by Cerezo et al (2011a), NH 3 -LiNO 3 and NH 3 -(LiNO 3 + H 2 O) by Oronel et al (2013a) and etrabutylammonium bromide (TBAB) -clathrate hydrate slurry (CHS) as a secondary refrigerant in an air conditioning system by Ma and Zhang (2011c). Other work in the literature on plate evaporators is exemplified by several other researchers: Kedzierski, Garcia-Cascales et al, Qiao et al (2007aQiao et al ( , 1997aQiao et al ( , 2013b.…”