Experimemtal And Numerical Research Of Self-driven Solar Air Collector With Constant Temperature

With developing of society and economy of China,the ratio of sustainable energy has increased through the time,and solar collector is one of the efficiency ways of using the sustainable energy.This article is based on previous Self-Driven Solar Air Collector(SD-SAC),which its outlet temperature,outlet flow rate relay on weather condition,and its time of constant outlet temperature has short duration.To overcome these problems,this article introduces a Constant-temperature Self-driven Solar Air Collector(CTSD-SAC).CTSD-SAC adds a control method based on SD-SAC,it controls the inlet fluid velocity through manipulate power of fan in outlet using PI control.Both numerical simulation and experimental verification are carried out to study the characteristic of CTSD-SAC.Firstly,simulation uses four different days of weather conditions of Qinhuangdao in summer,TRNSYS 16.1 is applied to investigate structural and operational parameters.The result show that:the maximum thermal efficiency of CTSD-SAC is 60%,the flowrate tendency of CTSD-SAC is a quadratic function with its quadratic term is negative,and summit of flowrate is affected by both solar intensity and ambient temperature.Weather parameter effects the thermal efficiency,through them ambient temperature has more effect while ambient wind speed barely effect.Different set temperature varies greatly in fluid flowrate,but thermal efficiency decreases less,with 10℃increases in set temperature,thermal efficacy only decreases 4%.Thermal efficiency will decrease while flowrate saturation occurs in outlet fan.Every 0.1 m~2 increases in PV panel,thermal efficiency of CTSD-SAC drops 10%.Electrical efficiency remains unchanged in every circumstance.Finally,experimental investigation finds out there are two stages called nature ventilation stage and constant temperature control stage respectively during operation of CTSD-SAC,fluid flowrate has the same tendency with one in numerical simulation,and its maximum value is 65 m~3/h,maximum value of electrical efficiency is 2%,during constant temperature control stage,mean value of thermal efficiency is 70%,and it lasting around 5hours.When flowrate saturation occurs,there will be an overshoot while controller is tried to lower the flowrate,meanwhile electrical efficiency will decrease.Channing in azimuth angle will properly enhancing the character of CTSD-SAC.Thermal efficiency will reduce10%while changing in tilt angle.Thermal efficiency will have the same tendency with fluid flowrate while adding one more PV panel,and its maximum value is able to reach 70%,however,two PV panel still unable fulfill the power requirement of fan.This article has verified the feasibility of the constant-temperature self-driven collector,and performed systematic research on operational and structural parameters,this provides new path in design and optimization for new-type solar air collector.