Study On Liquid Dehumidification Air Conditioning System With Condensing Heat Regeneration

Conventional vapour compression refrigeration system is used to create comfortable living and working environment. However, it has adverse impact on energy consumpsion and outdoor environment. High energy consumption and high environmental pollution are two major disadvantages of such system. So it is urgent to develop a kind of air conditioning system with energy-conservation and economized electricity character. Liquid desiccant air conditioning system with condensing heat regeneration was presented in this paper, which integrated vapour compression refrigeration system and liquid desiccant system. The heat rejected from the condenser was used to regenerate the liquid desiccant to improve the performance of system and conserve energy.The thermo-physical properties of liquid desiccant were presented. Combining with economic analysis, the principle of selection of liquid desiccant was provided. And lithium chloride(LiCl)was choused as a desiccant for dehumidification in this paper.Liquid desiccant air conditioning system with condensing heat regeneration was established. This paper presented the experimental tests and the numerical simulation on the main components of system dehumidifier as well as regenerator.Experiment was carried out to test heat and mass transfer performance of cross-flow dehumidifier using metal packing. The effects of air flow rate, solution flow rate and inlet parameters of air and solution on the outlet parameters were also investigated. And a great deal of data obtained from experiment was processed using multiple linear regression method. Several empirical formulas were given, i.e. coefficient of heat and mass transfer, the rates and efficiency of dehumidification evaluating performance of dehumidifier, which provided good reference and necessary information for further theoretical investigation.A mathematical model of cross-flow dehumidifier describing heat and mass transfer between air and liquid desiccant was set up. Taking the heat and mass transfer coefficients achieved from experiments as the input parameter of the model, the parameter distribution of air and liquid desiccant on the packing surface were described, which is of reference and guiding significance to the performance analysis of dehumidifier. Weak solution was sprayed on the tube bundle of evaporative condenser. Liquid solution was regenerated utilizing evaporation condensation mechanism. Performance of evaporative condensing regenerator was studied experimentally. The influences of inlet parameters such as air, solution and refrigerant on the performance of regenerator were discussed. Heat and mass transfer coefficient of regenerator was correlated with air flow rate, solution flow rate, inlet air temperature and inlet solution concentration. The results had great value in the design and improvement of evaporative condensing regenerator.A two dimensional steady state model was developed and solved numerically to predict the performance of evaporative condensing regenerator. Two dimensional parameters distribution of air, solution and refrigerant were calculated by the mathematical model. The experimental results were used to validate mathematical model. It indicated that the simulation results agreed with experimental data well. The results showed that the mathematical model could be used to predict the performance of regenerator.Research results demonstrated that liquid desiccant air conditioning system with condensing heat regeneration had remarkable energy saving effect when it was used to reduce the moisture content of fresh air in summer, and characteristics of evaporative condensing regenerator played an important role in performance of system.