Conference Year

2016

Keywords

Regeneration, solar collector cum regenerator, liquid desiccant, desiccant cooling system, dehumidification

Abstract

A solar liquid desiccant air cooling system cools air in two stages: dehumidification followed by sensible cooling. It uses concentrated liquid desiccant to dehumidify the process air and reject the absorbed moisture to the ambient air through solar thermal heating in a solar collector cum regenerator (C/R). For the dehumidifier the liquid desiccant must be cold and strong in desiccant to reduce tendency of evaporation of water in the solution so that it can absorb water vapor from the process air. But, in the solar regenerator the solution must be hot to enhance evaporation of water from the solution to the regeneration air which requires thermal energy. The solar collector cum regenerator performance decides the overall cooling performance because for every kilogram of water dehumidified, at least the same amount must be rejected in the solar regenerator. Direct coupling of the solar regenerator with the dehumidifier may not be possible since the moisture removed in the dehumidifier may not get evaporated in the solar regenerator simultaneously. The solar thermal energy collection and the operating conditions decide the regeneration capacity of the solar collector cum regenerator. This paper presents experimental solar regeneration performance of CaCl2-H2O and LiCl-H2O solutions using two different sized solar C/R of absorber area 1.47 and 4 m2 inclined at 14o from the horizontal. The diurnal mass of water evaporated from LiCl and CaCl2 solutions at different concentrations is reported. The water evaporation per unit absorber area was found to be independent of C/R size for experiments carried out on the two regenerators for both LiCl and CaCl2 solutions for similar levels of irradiance and initial desiccant concentration. In addition, the paper discusses some basic solar C/R design issues and explores the coupling possibility of a solar C/R with a liquid desiccant cooling system. The results presented are useful in deciding the size of a solar C/R for coupling with a liquid desiccant cooling system of desired capacity.

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