Experimental And Optimal Study On The Liquid Desiccant Dehumidification System

Solution dehumidification is a technology based on strong absorbent solutions,with advantages of using low grade heat, environmental friendly and energy saving.In order to optimize the operating parameters of the system, grasp the energyconsumption in each component, and then the existing system can be improved, thisthesis carried out the following studies.Firstly, experiments on the performence of dehumidifier and regenerator arecarried out in the dehumidifying experimental platform, the solution parameters thataffecting the performance of the liquid system are analyzed, the results show betterdehumidification performance is obtained with the solution inlet temperature of32~36℃, concentration of50%~54%, the ratio of liquid flow to gas of2.5~3, thedehumidifier can be designed with the mass transfer coefficient of1kg·m-3·s-1. Byusing orthogonal experimental analysis, it is found that the air inlet humidity andsolution inlet concentration give the biggest influence on the dehumidificationperformance, while the solution inlet temperature and concentration are theparameters impact the regeneration performance much bigger, the optimal inletparameters for dehumidifier and regenerator are also got.Secondly, the liquid desiccant system driven by low temperature waste heat issimplified; the energy comsumption in each component is analyzed using the secondlaw of thermodynamics. More than80%of exergy loss is found in flue gas-solutionheat exchanger. The exergy efficiency of dehumidifier and regenerator is highly,however, the whole system exergy efficiency is about10%. Further analysis onexergy potential promotion ratio in each component is made, there is a larger space ofexergy potential promotion in the gas-solution heat exchanger as well as the wholesystem. At the same time, the increasing of regeneration temperature causes adecrease in the system’s exergy efficiency, however, a better performance of thedehumidification.Finally, a kind of two stages cross flow of solution dehumidification system isproposed, simulation analysis is made on feasibility of the new dehumidificationsystem by using Fluent and Matlab. The results show that the pressure drop in mode1and mode2system is250~300Pa.The pressure and velocity field in mode1arebasically symmetrical to mode2. At the same time, the inequality degree of airdistribution in the first filling layer is small, but relatively large in the second filling layer. The air that has not completely got through the first filler layer but directly intothe second filler layer is about1/3, which is caused by the differential pressurebetween the two level filling layers. Results of heat and mass transfer simulation onthe new system show that: in the condition of inlet air humidity of20g/kg,12.9~13.7g/kg is obtained in the outlet air humidity by traditional cross flowdehumidifier with50%of dehumidification efficiency, while9.7~11.4g/kg water iscontained in the outlet air by the two stages dehumidifier, dehumidification capacityincreased by2.3~3.2g/kg and dehumidification efficiency improved by about20%.The optimizing of operational parameters and the exergy analysis of thedehumidification system give basis for improving efficiency in system operation, thefeasibility analysis of two stages cross flow dehumidifier system provides a newscheme for achieving deep dehumidification...