Mathematical modelling of desiccant dehumidifier for air conditioning system

Abstract

Air conditioning has become one of the necessities to symbolize the improved living standard. Moreover, the increase in demand for comfort and over occupation of public places put undue pressure on air conditioning system and hence pressure on energy sources. Therefore, the need of the hour is to develop such system which should be more energy efficient. The major load on the conventional air condition systems is the latent heat load i.e. the removal of the moisture from the outdoor air to improve the standard of the supply air. This load can be separated from the air-conditioning system by using Desiccant Technology in combination with conventional air-conditioning system. This leads to the development of Desiccant-Vapour Compression Hybrid Air Conditioning System. In the present study a methodology has been presented for the study of the parameters which affect the working of the heart and soul of desiccant system i.e. the dehumidifier. An analytical mathematical model has been developed for the dehumidifier by using various property and conservation equations. In this study Lithium Chloride solution has been used as the desiccant and the model shows good agreement with the experimental results obtained by the previous researchers. The developed model has been used to find the variation of condensate mass flow rate with the change in inlet air temperature. These results have been compared with the results obtained from the experimental results by Fumo et al.[8]. The modeled results are found to be within 10.62% deviation from the modeled results. Further the model has been used to study the effect of various inlet parameters like inlet desiccant temperature, inler air mass flow rate, inlet desiccant concentration and inlet air humidity on the performance of the dehumidifier. . It has been found that as the inlet desiccant temperature is decreased from 35℃ to15℃ , the reduction in humidity ratio of process air is increased by 370%.