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In this paper a microporous membrane is used in combination with rectangular microchannels in the absorber of an absorption chiller, working in two different configurations: cooled by a water flow and adiabatically. In the non-adiabatic case, the configuration of the channels allows the heat released during absorption to be extracted using a cooling water flow. The results for solution concentration, pressure potential, absorption coefficient, absorption rate, temperatures and power exchanged/stored by the working fluids along the absorption channels are presented. The ratio between the cooling power of the chiller equipped with the simulated absorber and the absorber volume, r qV , is used to characterise the absorber compactness. A parametric analysis is also performed to evaluate the influence on the ratio r qV of the inlet solution mass flow rate, the solution inlet temperature, and the height and width of the solution channels, for both absorbers. For the base case considered in this study, both absorber configurations offer r qV higher than 1 MW m −3 . This ratio is higher than usual values found in falling film absorbers using conventional circular tubes. Moreover, the new adiabatic configuration presented has significant advantages respect to the non-adiabatic one in terms of higher r qV and fabrication simplicity. [ABSTRACT FROM AUTHOR]

The simulation of the heat and mass transfer in a H 2 O–LiBr microchannel desorber endowed with a microporous membrane is presented. The heat and mass transfer processes are modelled by means of selected correlations gathered from the open literature. The simulation provides the evolution along the channels of the parameters involved in the process: heat and mass transfer coefficients, solution concentration, temperatures of the working fluids and pressure potential. The calculated values of the desorption rate are compared to experimental data gathered from the open literature. For the case considered in this study, the maximum ratio between cooling capacity of the chiller and desorber volume is 2312 kW m −3 . This value is more than one order of magnitude higher than the ones found in conventional small-size absorption cooling chillers. [ABSTRACT FROM AUTHOR]

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. The simulation of the heat and mass transfer between the solution and the vapour phase in a H 2 O–LiBr absorber using porous fibres is considered. Heat and mass transfer processes are modelled by means of selected correlations and data gathered from the open literature. This new model is applied for the simulation of the absorber under typical operating conditions of absorption cooling chillers. Absorption rate, heat and mass transfer coefficients, solution concentration, temperatures of the working fluids and pressure potential along the absorption channels are calculated. For the case considered in this study, the absorber channels are of 5 cm length, offering a maximum ratio between cooling capacity of the chiller and absorber volume of 1090 kW/m 3 . This ratio is higher than twice the usual values found in falling film absorbers using conventional circular tubes. The mean absolute error between the model results and the experimental data gathered from the open literature is 8.5%, showing the capability of the model to predict the performance of membrane-based absorbers. [ABSTRACT FROM AUTHOR]