Study On The Dehumidification Enhancement Of Desiccant-coated Heat Exchanger

Desiccant-coated heat exchanger (DCHE) is a kind of internal cooled/heated dehumidifier, which is made by fin-tube heat exchanger coated with solid desiccant materials. Compared with conventional adiabatic dehumidifier, DCHE can overcome the decrease of dehumidification cased by adsorption heat and the decrease of regeneration cased by desorption heat, which in turn enhances the dehumidification and regeneration respectively. The media used to regenerate the desiccant is hot water, so solar energy and other low grade thermal energy can be used. In this paper, DCHE is experimentally and theoretically investigated.An experimental setup is build to test the performance of DCHE driven by solar water. It is found that the energy consumed can be reduced and proper supply air conditions can be reached by controlling the regeneration time and the supply points respectively. According to the test results of several typical conditions in a whole day, the average moisture removal rate and average cooling capacity are predicted and they could be tripled by using three devices at the same time.A one-dimensional heat and mass transfer model of DCHE is used to analyze the effects of several parameters on system performance in terms of dynamic air outlet humidity ratio as well as temperature. In order to describe the phase between two operation modes, in which hot and cold water blend together, two equations are added to the original model. At the same time, the fundamental dimensionless groups like the number of transfer units were derived. The simulation results conclude that the temperature of water affects greatly the dehumidification performance. While in comparison with the effects caused by water temperature, air temperature affects less. In this paper, the humidification function of DCHE in winter is also predicted. The simulation results based on typical meteorological parameters of Shanghai shows that DCHE can provide humidification and heating rate 0.107g/s, when the hot water temperature is 70℃.As an attempt to utilize the magnetic fields in the desiccant cooling system, the influences of magnetic fields on the adsorption of water on silica gel and composite desiccant are investigated. Results show that under given conditions, the magnetic fields can reduce the adsorption amount to some extent.