Study On Performance Of Silica Gel Coated Heat Exchanger

Humidity control is of great significance to living conditions and improving production quality.Solid desiccant dehumidification technology can effectively use industrial waste heat,solar energy and other low-grade thermal energy for driving,and has the advantages of energy conservation and environmental protection.However,the traditional solid desiccant dehumidification equipment will reduce its dehumidification performance due to the adsorption heat released by the desiccant during the adsorption process.Desiccant coated heat exchanger was prepared by combining raditional heat exchanger and solid desiccant material.In the dehumidification process,not only the moisture in the air was removed,but also the adsorption heat is taken away by internal cooling.Compared with other dehumidification technologies,desiccant coated heat exchanger not only preserves the advantages of solid adsorption dehumidification technology,but also has the advantages of low adsorption heat and low cost.In this paper,a cross-flow silica gel coated heat exchanger with internal cooling is taken as the research object,and the influence of operating conditions at low regeneration temperature on crossflow silica gel coated heat exchanger is deeply discussed through experimental study,which provides reference for its application in low-grade heat energy recovery and utilization.Firstly,the desiccant and its production process were optimized to develop the silica gel coated heat exchanger,and the absorption and heat transfer performance of the silica gel coated,and the changes of specific surface area,pore volume and pore diameter after coating were analyzed.Secondly,an experimental test platform was built by using the desiccant coated heat exchanger,and the experimental principle of was introduced,and the performance evaluation index is also established.Finally,the effects of regeneration air temperature,supply air humidity ratio content,supply air temperature,supply air velocity and cooling air velocity on the performance of desiccant coated heat exchanger are analyzed.The experimental results show that: When the binder mass is 15% of the silica gel desiccant mass,it can make a good silica gel coated adhesion effect,but the amount of silica gel coating is reduced due to the blockage of the holes,make its entrance specific surface area,pore volume decreased to 72.3% and 63.9% respectively,the average pore diameter are increased by 13.1%,but there was no significant change in the distribution of voids;When the relative humidity was 60%,the adsorption rate of the silica gel coated was reduced by 10.5% compared with the Silica gel particles,which ensured its adsorption performance.In terms of heat transfer performance,compared with the formation of the coating,the heat transfer ability of the original silica gel particles was improved by 89.5 times.Through the analysis of the operating parameters,it is found that the silica gel coated heat exchanger can effectively reduce the humidity ratio of the outlet air of the silica gel coated heat exchanger at the regeneration temperature of 50-80 ℃,and achieve the dehumidification effect.Under the experimental conditions,the outlet air of the silica gel coated heat exchanger contains lower moisture and temperature at the flow rate of 1.5m/s after was fed into the cooling air than the outlet air without the cooling air,and the average dehumidification capacity,COP and DCOP are increased by 36%,58.5% and 62.9% respectively.Moreover,the greater the flow in the cooling air is,the more obvious the effect will be.The regeneration air temperature has a greater impact on the performance of the silica gel coated heat exchanger.As the regeneration air temperature increases,the average dehumidification capacity of the silica gel coated heat exchanger is higher.When the regeneration air temperature rises from 50 ℃ to 80 ℃,the average dehumidification capacity of the silica gel coated heat exchanger increased by 311.7%.However,the excessive regeneration temperature will cause the COP and DCOP decrease.Under the given experimental conditions,when the regeneration air temperature is 70 ℃,the comprehensive performance of the silica gel coated heat exchanger is better.The supply air status has a direct effect on the heat and mass transfer of silica gel coated heat exchanger: when the supply air humidity ratio was increased from 12g/kg-dry air to 18g/kg-dry air,the average dehumidification capacity,COP and DCOP increased by nearly 12.1%,67.4% and 45.2% respectively;when the supply air velocity was increased from 1m / s to 2m / s,the average dehumidification capacity decreased by nearly 51%,and COP increased by nearly 34.5%,but the effect on DCOP was small;when the supply air emperatureis increased from 28℃to 32℃,the average dehumidification capacity,COP and DCOP have decreased by nearly 30.4%,48.8% and 30.3%,respectively.