摘要
为了进一步提高无盖板型太阳能空气集热器的集热效率,该研究提出了一种利用U型管制造反向射流强化集热板换热的无盖板型太阳能空气集热器。通过试验研究了该型集热器内部的温度分布特性,以及2020年12月10日和2021年6月20日的集热性能。试验结果表明:反向冲击射流的冷却作用可以有效降低集热板表面温度,形成覆盖大部分集热板面积的低温区域,且温度分布较为均匀;作为产生反向射流的U型管,还可以充当肋片结构对进入集热腔内的空气进行预热,夏季晴朗工况下U型管的进出口温差可达3.5℃;该型集热器在6月20日的平均集热效率可达到80%,而12月10日的热效率仅为45%,冬夏集热效率的差别较大。该研究为无盖板型太阳能集热器性能优化提供了新思路。
A Solar Air Collection(SAC) has been well known as one of the most developed technologies in solar energy industry.Therefore,the SAC heat exchanger has also been widely used to convert the solar radiation into heat energy in a broad range of fields,such as space heating and crop drying.However,the SAC utilization depends mainly on the high density and heat capacity of air,particularly for the better heat transfer between flowing air and absorption plate.Therefore,the high intensity of heat transfer can be improved by increasing the absorption areas and enhancing the turbulence in the collector cavity.Much effort has been made to improve the thermal performance of solar collector,particularly by changing the structure of the absorption plate or the flow channel in the cavity.Specifically,some new structures were proposed to increase the surface roughness,such as V-fins,W-fins,and hemispherical grooves.Furthermore,some staggered fins and baffles were added to introduce the swirling flow for the higher turbulence intensity in the collector cavity.These technologies can be utilized for the better SAC performance of the absorption plate and the air flow.In addition,the jet impact can also be expected to improve the heat exchange intensity of the collector,while the unglazed collector can be used to reduce the reflection loss of heat radiation.But,the main heat loss on the bare cover plate depends mainly on the external wind speed.Therefore,it is necessary to further promote the heat exchange intensity in the unglazed collector,in order to speed up the air in the cavity to take away the heat on the heat absorbing plate,particularly for the reduced heat loss on the plate.In this study,an optimal unglazed solar air collector was proposed for the higher efficiency of heat collection using the U-tube reverse jet for the heat exchange of the collector plate.A systematic experiment was carried out to explore the temperature distribution inside the collector and the heat collection performance under the typical winter and summer conditions.The experimental results show that the optimal cooling performance of reverse impinging jet was achieved to effectively reduce the surface temperature of the collector,particularly for the low-temperature area covering most of the area of the heat absorbing plate.The relatively uniform temperature distribution was greatly contributed to reduce the heat loss of the collector.The U-shaped tube as the reverse jet was also utilized to introduce the additional function for the air preheating,when entering the collector chamber.The relatively small temperature difference of 3.5 ℃ was found between the inlet and outlet of the U-shaped tube under the typical working conditions.The average efficiency of heat collection reached 80% on the typical working days in summer,while only 45% was obtained in winter.Consequently,the finding can provide a new idea for the performance optimization of solar collector without cover plate.
作者
胡桂
胡建军
金健
谈宏莹
Hu Gui;Hu Jianjun;Jin Jian;Tan Hongying(Hebei Province Low-Carbon and Clean Building Heating Technology Innovation Center,Yanshan University,Qinhuangdao 066004,China;Key Laboratory of Green Construction and Intelligent Maintenance for Civil Engineering of Hebei Province,Yanshan University,Qinhuangdao 066004,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2022年第10期232-238,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
中央引导地方科技发展资金项目(No.226Z1902G)
河北省自然科学基金(No.E2020203028)
河北省高等学校科学技术研究项目(No.QN2018137)。
关键词
太阳能
集热器
无盖板
集热效率
射流冲击
solar
collector
unglazed
thermal efficiency
jet impingement
作者简介
胡桂,研究方向为太阳能热利用。Email:Hugui0101@126.com;通信作者:胡建军,博士,教授,研究方向为太阳能热利用。Email:kewei729@163.com。
