Study On Dehumidification Performance Of Regenerative Desiccant Heat Exchanger

Solid desiccant dehumidification can be driven by low grade thermal energy, such as solar energy and waste heat, which has the merits of energy-saving and environmental friendly. However, due to the release of adsorption heat in the adsorption process, the dehumidification process in traditional desiccant dehumidification always deviates from the ideal isothermal dehumidification, which also leads to the reduction of overall coefficient of performance. In this thesis, a new type of regenerative desiccant heat exchanger, in which the adsorption heat is taken away by cooling water, is proposed to solve this problem,. Firstly, the selection of desiccant material is analyzed and the desiccant selection and work principle of desiccant heat exchanger are analyzed. Besides, optimal desiccant and coating processes are got by comparison, and a desiccant heat exchanger is designed and fabricated. Then a dehumidifier experimentel setup is designed to investigate the operation characteristics of under various operation conditions. Also, a mathematical model of desiccant heat exchanger is established to investigate the complex heat mass transfer mechanism and to analyze the efficient way of enhancing heat and mass transfer. Effects of parameters on the system performance are also discussed. At last, adoption of such heat exchanger in solar driven dehumidifier is analyzed.Research results show that by use of this configuration, the disadvantageous effect of adsorption heat can be solved. Meanwhile, there exist optimum tube row, fin pitch, regeneration temperature and wind speed for this desiccant heat exchanger to reach highest COP, which are: 3 rows, 1.5mm, 70℃, and 1m/s. Performance of the system is enhanced with the increasing of inlet air moisture ratio especially under the condition of low humidity ration, where the utilization of solar energy dehumidifier can reach 30%. In addition, the feasibility of integration of this heat exchanger and the heat pump dehumidifier is validated. In summary, desiccant heat exchanger is expected to be widely used in solar air-conditioning, humidity and other interrelated fields.