日光温室后墙夜间非稳态导热特性研究
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摘要
【目的】对日光温室后墙夜间的非稳态导热特性进行研究,为发挥后墙保温作用提供理论依据。【方法】在位于山东泰安的试验温室内,分别于温室后墙距地面0.1,1.1,2.1,3.1和4.1m处及地面距离后墙0.1m处设置测点,选取2015年越冬季某一晴天和阴天,在18:00至翌日06:00,每隔1h测定后墙各测点的温度和热流密度,计算各测点温度变化率、热流密度积分值、后墙内部热量流动量,以及后墙与地面之间的热量流动量,研究夜间温室后墙不同高度蓄热量变化与放热量之间的关系、地面温度与后墙温度之间的关系,以及后墙内部和后墙与地面之间的热量流动。【结果】晴天夜间后墙中上部蓄热量变化基本相同且大于后墙下部蓄热量变化,后墙中上部放热量逐渐降低然后趋于平稳,后墙下部放热量逐渐增多,后墙中部放热总量最多;后墙温度24:00之前高于地面温度,24:00之后低于地面温度,后墙与地面之间存在热量流动;后墙内部热量流动数量占后墙放热总量的比值为14.2%。阴天夜间后墙中上部蓄热量变化基本相同且大于后墙下部蓄热量变化,后墙放热量从上到下逐渐增多;后墙温度低于地面温度,地面流入后墙热量占后墙放热总量的比值为3%;后墙内部热量流动数量占后墙放热总量的比值为25.5%。【结论】后墙高度、后墙不同高度蓄热量影响后墙不同高度放热量;后墙高度对放热量的影响贯穿后墙放热过程的始终,后墙蓄热量对放热量的影响主要集中在后墙放热前期;后墙热量存在自上而下的整体迁移流动。
【Objective】This study investigated the characteristics of unsteady heat conduction of the back wall of solar greenhouse at night to provide basis for improving the heat-releasing ability of back wall.【Method】In the test greenhouse in Tai'an,Shandong,test points were set up at 0.1,1.1,2.1,3.1,and 4.1 m on the back wall and at ground 0.1 maway from the back wall.The temperature and heat flow density of each test point were measured every 1 hour from 18:00 to 06:00 of the following day on a sunny day and a cloudy day in winter,2015.The change rate of temperature at each test point,the integral value of heat flow density,the internal heat transfer of the back wall,and the heat flow between the back wall and the groundwere calculated.The relationship between heat storage and heat-releasing volume at different heights of back wall,the relationship between the ground temperature and the back wall temperature,the internal heat transfer of the back wall,and the heat flow between the back wall and the ground surface were studied.【Result】The variations of heat storage in the middle and upper parts of the back wall were basically the same and larger than that in the lower part during sunny night.The heat-releasing volumes of the middle and upper parts of the back wall firstly decreased gradually and then tended to be steady.The temperature of the back wall was higher than the ground temperature before midnight and lower than that after midnight,and there was heat flow between the back wall and the ground.The internal heat migration flow from the middle and upper parts to the lower part was 14.2%of the total heat-releasing volume of the back wall.The variations of heat storage in the middle and upper parts of the back wall during cloudy night were basically the same and larger than that in lower part,the heat-releasing volume increased gradually from the upper part to the lower part,and the temperature of the back wall was lower than that of the ground.The heat flow volume during cloudy night from the back wall to the ground was 3%of the total heat-releasing volume of the back wall,and the internal heat migration flow from the middle and upper parts to the lower part was 25.5%of the total heat-releasing volume of the back wall.【Conclusion】The heat-releasing volumes at different heights of the back wall are affected by the wall height,and heat storages at different heights of the back wall.The effect of the wall height is existing in the whole heat-releasing process,and the effect of heat storage of the back wall is mainly at early period.There is heat migration flow of internal back wall.
【Objective】This study investigated the characteristics of unsteady heat conduction of the back wall of solar greenhouse at night to provide basis for improving the heat-releasing ability of back wall.【Method】In the test greenhouse in Tai'an,Shandong,test points were set up at 0.1,1.1,2.1,3.1,and 4.1 m on the back wall and at ground 0.1 maway from the back wall.The temperature and heat flow density of each test point were measured every 1 hour from 18:00 to 06:00 of the following day on a sunny day and a cloudy day in winter,2015.The change rate of temperature at each test point,the integral value of heat flow density,the internal heat transfer of the back wall,and the heat flow between the back wall and the groundwere calculated.The relationship between heat storage and heat-releasing volume at different heights of back wall,the relationship between the ground temperature and the back wall temperature,the internal heat transfer of the back wall,and the heat flow between the back wall and the ground surface were studied.【Result】The variations of heat storage in the middle and upper parts of the back wall were basically the same and larger than that in the lower part during sunny night.The heat-releasing volumes of the middle and upper parts of the back wall firstly decreased gradually and then tended to be steady.The temperature of the back wall was higher than the ground temperature before midnight and lower than that after midnight,and there was heat flow between the back wall and the ground.The internal heat migration flow from the middle and upper parts to the lower part was 14.2%of the total heat-releasing volume of the back wall.The variations of heat storage in the middle and upper parts of the back wall during cloudy night were basically the same and larger than that in lower part,the heat-releasing volume increased gradually from the upper part to the lower part,and the temperature of the back wall was lower than that of the ground.The heat flow volume during cloudy night from the back wall to the ground was 3%of the total heat-releasing volume of the back wall,and the internal heat migration flow from the middle and upper parts to the lower part was 25.5%of the total heat-releasing volume of the back wall.【Conclusion】The heat-releasing volumes at different heights of the back wall are affected by the wall height,and heat storages at different heights of the back wall.The effect of the wall height is existing in the whole heat-releasing process,and the effect of heat storage of the back wall is mainly at early period.There is heat migration flow of internal back wall.
引文
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[2]梁建龙,王旭峰.阿拉尔垦区日光温室墙体的保温设计[J].塔里木农垦大学学报,2002,14(1):29-30.Liang J L,Wang X F.Design of thermal insulation of greenhouse wall in Alar reclamation area[J].Journal of Tarim University of Agricultural Reclamation,2002,14(1):29-30.
[3]柴立龙,马承伟,籍秀红,等.北京地区日光温室节能材料使用现状及性能分析[J].农机化研究,2007(8):17-21.Chai L L,Ma C W,Ji X H,et al.Present situation and the performance analysis of the energy-saving material in solar greenhouse of Beijing region[J].Journal of Agricultural Mechanization Research,2007(8):17-21.
[4]樊平声,冯伟民,卢昱宇,等.不同墙体日光温室保温性能研究[J].山东农业科学,2014,46(3):25-27.Fan P S,Feng W M,Lu Y Y,et al.Effects of different walls on thermal insulation properties of solar greenhouse[J].Shandong Agricultural Sciences,2014,46(3):25-27.
[5]曲继松,张丽娟,冯海萍,等.宁夏干旱风沙区夯土砖土复合墙体日光温室保温性能初步研究[J].西北农业学报,2010,19(1):158-163.Qu J S,Zhang L J,Feng H P,et al.A preliminary study on brick-clay compound wall heat preservation effect of solar greenhouse in Ningxia arid-sandstorm area[J].Acta Agricultural Boreali-Occidentalis Sinica,2010,19(1):158-163.
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[8]佟国红,王铁良,白义奎,等.日光温室节能墙体的选择[J].可再生能源,2003(4):14-16.Tong G H,Wang T L,Bai Y K,et al.Selection of energy efficiency wall in solar greenhouse[J].Renewable Energy,2003(4):14-16.
[9]卢志权,刘在民,于锡宏,等.不同凹式墙体对温室蓄热性能的影响[J].浙江大学学报,2013,40(3):344-361.Lu Z Q,Liu Z M,Yu X H,et al.Effects of different concave type structure wall on thermal performance in the greenhouse[J].Journal of Zhejiang University,2013,40(3):344-361.
[10]温祥珍,梁海燕,李亚灵,等.墙体高度对日光温室内夜间气温的影响[J].中国生态农业学报,2009,17(5):980-983.Wen X Z,Liang H Y,Li Y L,et al.Effect of wall height on air temperature of greenhouse during night[J].Chinese Journal of Eco-Agriculture,2009,17(5):980-983.
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[12]管勇,陈超,凌浩恕,等.日光温室三重结构相变蓄热墙体传热特性分析[J].农业工程学报,2013,29(21):166-173.Guan Y,Chen C,Ling H S,et al.Analysis of heat transfer properties of three-layer wall with phase-change heat storage in solar greenhouse[J].Transactions of the Chinese Society of Agricultural Engineering,2013,29(21):166-173.
[13]管勇,陈超,李琢,等.相变蓄热墙体对日光温室热环境的改善[J].农业工程学报,2012,28(10):194-201.Guan Y,Chen C,Li Z,et al.Improving thermal environment in solar greenhouse with phase-change thermal storage wall[J].Transactions of the Chinese Society of Agricultural Engineering,2012,28(10):194-201.
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[15]杨仁全,马承伟,刘水丽,等.日光温室墙体保温蓄热性能模拟分析[J].上海交通大学学报,2008,26(5):449-453.Yang R Q,Ma C W,Liu S L,et al.The imitation analysis of heat preservation and capability of the wall of solar greenhouse[J].Journal of Shanghai Jiaotong University,2008,26(5):449-453.
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[18]佟国红,Christopher D M.墙体材料对日光温室温度环境影响的CFD模拟[J].农业工程学报,2009,25(3):153-157.Tong G H,Christopher D M.Simulation of temperature variations for various wall materials in Chinese solar greenhouse using computational fluid dynamics[J].Transactions of the Chinese Society of Agricultural Engineering,2009,25(3):153-157.
[19]方慧,杨其长,张义.基于热泵的日光温室浅层土壤水媒蓄放热装置试验[J].农业工程学报,2012,28(20):210-216.Fang H,Yang Q C,Zhang Y.Experimental study on shallow soil assisted heat release-storage system with water-water heat pump in solar greenhouse[J].Transactions of the Chinese Society of Agricultural Engineering,2012,28(20):210-216.
[20]张靖周,常海萍.传热学[M].北京:科学出版社,2015.Zhang J Z,Chang H P.Heat transmission science[M].Beijing:Science Press,2015.
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