Study On Mechanism Of Heat And Mass Transfer In Dehumidifier With Self-cooled Liquid Desiccant

Solution dehumidification is environmentally friendly and energy-saving.The key technical difficulty is that the dehumidification performance is degraded due to the increase of solution temperature during dehumidification.In this thesis,the heat and mass transfer mechanisms of dehumidification of adiabatic and internal cooling solutions were introduced,the defects and deficiencies of the two dehumidification mechanisms were analyzed and explored,and a new dehumidification method was proposed.In this thesis,the dehumidification method of self-cooled ternary solution is proposed for the first time.The evaporative coolant is added into the traditional dehumidification solution,and the cooling effect of evaporative coolant is utilized.The stable temperature control of the dehumidification solution could be realized in simple dehumidifier,which to some extent simplifies the component design and improves the dehumidifying performance.In this thesis,the sensible heat transfer caused by temperature difference and the latent heat change caused by humidity difference were analyzed.The heat transfer and mass transfer equation correlation determined by dimensionless quantity were derived to study the mechanisms of heat and mass transfer on the gas-liquid phase interface of multicomponent dehumidification solution.In addition,the working hypothesis of self-cooled dehumidification technology was established.In this thesis,to evaluate the dehumidification performance of the solution,a dehumidification test device was set up to test and analyze the independent factors affecting the dehumidification performance index and their relations,and a solution dehumidification test platform with a certain scale was constructed to analyze,test and verify the influence of air and solution parameters on the dehumidification performance indexes.The conditions of environmental variables were comprehensively summarized,and the experimental design of different environmental variables and solution parameters were controlled respectively.The performance of the solution dehumidification system under different control variables was evaluated by three evaluation indexes: dehumidification,dehumidification rate and dehumidification efficiency.The experimental results of the multi-component solution dehumidification show that the trend of the performance of the conventional LiCl aqueous solution and the selfcooled solution is basically the same,and 25°C and 40% are respectively considered as the optimum solution temperature and concentration.For the experimental setup under study,it is recommended that low temperature,high concentration and high solution flow rates ensure optimum performance of the self-cooled solution dehumidifier.Compared with the conventional LiCl solution,the dehumidification performance of the self-cooled solution was verified in the experiment.The dehumidification efficiency and dehumidification rate of the self-cooled dehumidification solution were higher than those of the conventional dehumidification solution,and the relative dehumidification performance index was increased by more than 40%.The working assumption of the meta-mixing component dehumidifying solution is established.The self-cooled solution before and after the introduction of the internal cooling water were substantially the same in the numerical comparison of the dehumidification performance parameters.The increase of the temperature of the inlet solution will result in a certain degree of dehumidification of the self-cooled dehumidification solution.In the "self-cooled and adiabatic" mode of operation,the dehumidification efficiency is greatly reduced,and the maximum value of the decrease is 24.79%.The research content of this thesis proposes a new idea for improving the dehumidification performance of the solution,and provides a certain theory for the dehumidification system design,new dehumidification solution,wall wetting,heat and mass transfer enhancement and other upgrading and transformation methods of the dehumidifier system.This technology has certain advantages for the upgrading of the traditional solution dehumidification system.