Experimental Research On The Regeneration Of The Solar Desiccant Solutions At Boiling Condition Under Atmospheric Pressure

Liquid desiccant, an efficient desiccant which makes use of a variety energy sources to meet the need for air dehumidification, outweights conventional dehumidification such as condensing dehumidification. Solar energy as a clean and renewable energy,has caught increasing attention and study due to its abundant reserves, widely distribution and environmentally friendly property. With sever energy situation and increasing requirement for air quality, solar liquid desiccant will be widely applied.Regenerator is a key component of desiccantsystem. It directly affects whether the air conditioning system can meet the need for usage, technical & economic characteristics. However, currently, the widely used regenerative mode can be affected by the state regeneration air, which limits the use of liquid desiccant air conditioner. Boiling heating can achieve relatively high heat transfer coefficient under relatively lower temperature. The regeneration mode of liquid desiccant by boiling will not be influenced by the state of regenerative air.This study focuses on investigating the boiling form of liquid regeneration under standard pressure. Firstly, the priority liquid concentrations for common liquid desiccant Li Br, LiCl, CaCl2 and the mixture of LiCl and CaCl2 with 1:1 ratio during cooling and dehumidification process are 55%~60%, 40~45% 37~42%, and 38~43%, respectively. Secondly, based on the surface vapor pressure of dehumidification liquid and crystallization equation, the h-d-ξgraphs corresponding to the above liquids were drawn, in order to determine the concentration and temperature for those liquids. Thirdly, four types of desiccant solution were tested for boiling temperature and boiling regeneration rate under the same concentration and equivalent concentrations, using the self-built device. The weighting factor analysis was used to compare boiling temperature, regeneration rate, cost, corrosion properties, and transmission and distribution of energy for the four desiccant solutions under equivalent concentrations. The results show that CaCl2 is the most appropriate solution for boiling regeneration mode. Moreover, orthogonal experiments, designed based on device operation and the specific need for the experiments, were performed under standard pressure to assess the solution regeneration process. The orthogonal experiments included as initial concentration for the solution, initial temperature, heat flux density, and cooling water flux. The results show that heat flux density prominently impacts the rates of boiling regeneration in LiBr solution, CaCl2 solution and the mixture solution. In conclusion, according to the analysis on the distribution of solar energy in Guangzhou, current solar product characteristics and the cost, medium temperature of solar collector as essential heat source for desiccant solution of boiling regeneration under standard pressure is feasible. Nevertheless, in order to ensure the operation, it should rely on more stable heat source.