Experimental Investigation On Performance Of A Novel Composite Desiccant Coated Heat Exchanger In Summer And Winter Seasons

Desiccant coated heat exchanger?DCHE?is considered as a novel and promising technology to reduce the energy consumptions of HVAC?heating,ventilation and air-conditioning?systems during the process of providing a comfortable environment and improving the indoor air quality in buildings by dehumidifying and humidifying the airflow.It is fabricated by coating desiccant material into the outer surface of a sensible heat exchanger.The desiccant material Silica gel is widely adopted in DCHE technology.However,its adsorption capacity is limited.Some materials such as hygroscopic salt has higher adsorption mass compared with silica gel under the same condition,but with the disadvantage of higher regeneration temperature and corrosion.Then in this thesis,in order to obtain optimal desiccant which can be adopted in DCHE,a novel composite desiccant material silica gel and sodium acetate is proposed.To validate the practical performance of the new composite desiccant,an experimental setup is built up to test its performance under experimental conditions of temperature,inlet air velocity,regeneration water temperature,and water cooling temperature.The Experimental investigation on the performance of novel composite desiccant Silica Gel and Sodium Acetate Coated Heat Exchanger?SASCHE?is conducted for typical summer and winter seasons in the city of Shanghai,China.First,the effects of main parameters such as regeneration temperature,hot and cooling water temperature,inlet air velocity,thermal coefficient of performance(COP_th)and energy efficiency are experimentally investigated in summer and winter for dehumidification-cooling and humidification-heating application,respectively.Then,its performance is compared with Single Silica Gel Coated Heat Exchanger?SCHE?,and Potassium Formate and Silica Gel Coated Heat Exchanger?PSCHE?.In the summer season,the experimental results showed that the new composite desiccant material can handle dehumidification-cooling process with an excellent performance regarding cooling capacity and efficiency.The dehumidification capacity of SASCHE is improved by 10%and 30%in comparison with that of PSCHE and SCHE,respectively.During the winter season for humidification-heating process,the average humidification capacity of SASCHE is two times higher than PSCHE and SCHE.Additionally,indoor comfort conditions are satisfied with high hot water temperature and low inlet air velocity for the summer season,while low hot water temperature and high inlet air velocity are recommended for the winter season.Finally,a mathematical model for the outlet air temperature and humidity ratio is proposed.The experimental results and simulated data are compared for a typical cycle time of 720 s for summer and winter season.The uncertainties for the outlet air temperature and humidity ratio are 15%and 12%respectively during the summer season.In the winter season,the uncertainties are 14%for the outlet air temperature and 17%for the outlet air humidity ratio in comparison with the theoretical results.The mathematical simulation revealed that the performance of the DCHE regarding temperature and humidity ratio are an exponential function of the time and depend on various parameters such as regeneration water temperature,cycle time and mainly of the desiccant properties.