發(fā)布時(shí)間：2017-12-27 03:20

  本文關(guān)鍵詞：日光溫室不同厚度土墻蓄放熱特性研究　出處：《山東農(nóng)業(yè)大學(xué)》2017年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 日光溫室 土質(zhì)墻體厚度 蓄放熱特性 溫度場(chǎng)模擬

【摘要】：土質(zhì)墻體的日光溫室因具有蓄放熱性能好、取材方便、成本低等優(yōu)點(diǎn),深受廣大農(nóng)民的青睞。目前,我國(guó)日光溫室土墻的厚薄差異較大,甚至有很大一部分為超厚土墻,墻體占地面積加大,造成土地資源浪費(fèi)。日光溫室是我國(guó)獨(dú)有的溫室類型,其夜間維持作物生長(zhǎng)的熱量主要來源于日間溫室墻體及地面吸收的太陽輻射熱量,研究日光溫室不同厚度土質(zhì)墻體蓄放熱、接受太陽輻射得熱量及土墻體傳熱特性,對(duì)日光溫室土墻體建造的輕便化設(shè)計(jì)和提高土地利用率都具有十分重要的理論及實(shí)踐意義。本研究選取泰安市山東農(nóng)業(yè)大學(xué)南校區(qū)建造的2棟土墻厚度不同的下挖式日光溫室為研究對(duì)象,在溫室北墻中間部位按不同高度設(shè)置5個(gè)測(cè)試層,每層水平布設(shè)溫度傳感器,室內(nèi)墻體表面布設(shè)熱流傳感器及輻射計(jì)�；诟鳒y(cè)試層監(jiān)測(cè)的溫度、太陽輻射照度和熱流密度等數(shù)據(jù),研究了不同天氣情況下土墻內(nèi)溫度變化規(guī)律、各測(cè)試層太陽輻射量分布特性及土墻傳熱特性。主要結(jié)果如下:1.日光溫室土墻體內(nèi)溫度變化分析及墻體放熱效率評(píng)價(jià)以泰安市3.0 m厚土墻下挖式日光溫室為研究對(duì)象,基于溫室北墻5個(gè)測(cè)試層最冷季節(jié)(30 d)溫室內(nèi)氣溫、墻體溫度、室外氣溫及室外太陽輻照度測(cè)試數(shù)據(jù),分析了土墻日光溫室內(nèi)部空氣溫度及墻體內(nèi)溫度的分布規(guī)律。結(jié)果表明:各測(cè)試層墻體表面及由表面至墻內(nèi)0.1~0.6 m處測(cè)點(diǎn)的溫度均呈現(xiàn)出隨溫室內(nèi)氣溫周期性變化而變化的規(guī)律,且隨著墻體厚度的增加溫度的波動(dòng)幅值逐漸減小,時(shí)間相位明顯后移;0.7 m以后各測(cè)點(diǎn)的溫度波動(dòng)幅值變化很小且趨于穩(wěn)定,處于穩(wěn)態(tài)向室外的導(dǎo)熱過程;由此可以推定:日光溫室后墻體內(nèi)側(cè)約0.7 m的厚度為晝夜間蓄放熱的關(guān)鍵厚度。基于墻體溫度分布、墻體白天蓄熱量、夜間的放熱量分析,計(jì)算得出墻體夜間放熱效率約為43%,表明土墻白天蓄積熱量的43%用于改善夜間溫室內(nèi)熱環(huán)境。2.陰晴天情況下,日光溫室不同厚度土墻墻體蓄放熱特性基于晴好天氣(2015年12月30日—2016年1月2日)及連陰天氣(2016年1月4—6日)數(shù)據(jù)分析可知:連續(xù)晴好天氣及連陰天時(shí),1#溫室厚墻體(頂寬2.0m,底寬6.0 m)和2#溫室薄墻體(頂寬1.0m,底寬3.0 m)的5個(gè)測(cè)試層的放熱量均為從第1層至第5層逐漸增加,兩溫室土墻體各層次的溫度變化趨勢(shì)相同;連續(xù)晴好天氣(2015年12月30日—2016年1月2日)時(shí),1#厚墻體溫室和2#薄墻體溫室的5個(gè)測(cè)試層的每天平均蓄熱量分別為1971.2 k J和1888.9 k J,平均放熱量分別為808.1 kJ和763.1 kJ,1#和2#溫室的蓄熱量和放熱量的差值分別為82.3 k J和45.0 k J,數(shù)值差異很小。連陰天氣(2016年1月4—6日)的前兩天云層較薄有些散射光時(shí),1#和2#溫室的蓄熱量都很小,第三天云層較厚,散射光也很弱,蓄熱量甚至為零,基本為全天放熱,平均放熱量分別為1551.4 k J和935.5 k J,兩溫室差值為615.9 k J,數(shù)值差異較大;雖然溫室厚墻體放熱量明顯高于薄墻體放熱量,但距離墻體內(nèi)表面0.1 m處的平均氣溫也只差0.6℃,溫室內(nèi)較前部的氣溫差異更小。從維持整個(gè)溫室內(nèi)最低氣溫的效果來看其作用也是甚微。3.不同天氣狀況下日光溫室墻體5個(gè)測(cè)試層輻射得熱量分布及墻體傳熱量分布特性基于多云、多云轉(zhuǎn)陰、霧霾及晴好天氣2#溫室5個(gè)測(cè)試層采集數(shù)據(jù),分析了各測(cè)試層接受太陽輻射量分布。結(jié)果表明:室外氣象條件對(duì)溫室接受太陽輻射強(qiáng)度的影響較大。晴好天氣時(shí)墻體各測(cè)試層接受的太陽輻射量明顯高于多云和輕度霧霾天氣,重度霧霾(測(cè)試天PM2.5指數(shù)253)和陰天接受輻射量非常小。墻體表面不同高度接受的太陽輻射量從上至下為第2測(cè)試層最大,其次是第3測(cè)試層,2和3測(cè)試層輻射總量值比較接近;再次為第4、第1和第5測(cè)試層。同時(shí),基于上述不同天氣的墻體5測(cè)試層采集數(shù)據(jù),分析了墻體5個(gè)測(cè)試層及后屋面向室外傳熱量分布特性。結(jié)果表明:北墻1~5個(gè)測(cè)試層的傳熱量占總傳熱量的比例依次為:第1測(cè)試層(墻體厚度為147 cm)約為21%,第2測(cè)試層(墻體厚度為186 cm)約為19%,第3測(cè)試層(墻體厚度為224 cm)約為17%,第4測(cè)試層(墻體厚度為263 cm)約為14%,第5測(cè)試層(墻體厚度為300 cm)約為12%,后屋面約為17%;溫室內(nèi)熱量向室外的傳遞從低處至高處依次增強(qiáng),因此,保溫隔熱措施應(yīng)該是順勢(shì)加強(qiáng)。4.構(gòu)建了日光溫室墻體溫度場(chǎng)模型基于ANSYS有限元分析軟件構(gòu)建了求解日光溫室墻體溫度場(chǎng)的計(jì)算模型,以墻面實(shí)測(cè)溫度為自由度約束施加于模型邊界上,采用穩(wěn)態(tài)傳熱方法,模擬了陰晴天條件下不同時(shí)刻墻體內(nèi)溫度場(chǎng)變化,并對(duì)模擬數(shù)據(jù)與實(shí)測(cè)數(shù)據(jù)進(jìn)行比較分析,結(jié)果發(fā)現(xiàn)模擬曲線擬合較好,其模擬值與實(shí)測(cè)值的平均誤差為±1.0℃之內(nèi)。利用ANSYS熱分析方法構(gòu)建的墻體溫度場(chǎng)計(jì)算模型可以有效地預(yù)測(cè)溫室墻體內(nèi)部溫度場(chǎng)的變化,能為泰安地區(qū)墻體設(shè)計(jì)及傳熱特性分析提供理論參考。
[Abstract]:The solar greenhouse in the soil wall has the advantages of good heat storage and heat storage, convenient material extraction and low cost, which are favored by the vast majority of farmers. At present, there is a large difference in the thickness of the earth wall in China's solar greenhouse, and even a large part of the earth wall is super thick, and the area of the wall is increased, which causes the waste of land resources. Solar greenhouse is our unique greenhouse type, the night to maintain calorie crop growth mainly from solar radiation heat wall and ground absorb daytime greenhouse, greenhouse of different thickness of soil wall heat storage, solar heat and heat transfer characteristics of the wall body, on greenhouse soil wall design and construction of light improvement has great theoretical and practical significance of land utilization. This study selected 2 wall thickness to build Tai'an city Shandong Agricultural University South Campus under different dig in greenhouse as the research object, in the middle part of the north wall of the greenhouse with different height to set up 5 test layers, each layer level distributed temperature sensor, indoor wall surface heat flux sensor and radiometer layout. Based on the data of monitoring temperature, solar irradiance and heat flux, the temperature variation rule of the earth wall, the distribution characteristics of the solar radiation and the heat transfer characteristics of the earth wall under different weather conditions are studied. The main results are as follows: analysis and evaluation of 1. greenhouse wall heat release rate in wall temperature changes in Tai'an city 3 m thick wall dug under the sunlight greenhouse as the research object, based on the north wall of the 5 layer of greenhouse test the coldest season (30 d) in the greenhouse temperature, wall temperature, outdoor air temperature and solar irradiance data. Analysis of temperature distribution of the internal wall of greenhouse air temperature and wall. The results showed that the test layer of wall surface and wall surface by 0.1~0.6 to m temperature measuring points were shown with the temperature indoor temperature cycle which changes with the increase of the thickness of wall temperature fluctuation amplitude decreases obviously after temporal phase shift; 0.7 m after each measuring point amplitude the temperature fluctuation is small and stable, steady heat conduction process to the outside; it can be presumed: greenhouse walls inside about 0.7 m thickness of the thickness of the heat storage key day and night. Based on wall temperature distribution, wall heat storage during the day and heat release at night, it is calculated that the night heat release efficiency of the wall is about 43%, indicating that 43% of the daily thermal storage capacity of the earth wall is used to improve the thermal environment in the greenhouse at night. 2. sunny days under greenhouse of different thickness of wall wall heat storage based on the characteristics of fine weather (December 30, 2015 - January 2, 2016) and overcast weather (January 2016 4 - 6 days) data analysis shows that: continuous fine weather and cloudy, greenhouse 1# thick wall (top width 2.0m, bottom width 6 m) and 2# thin greenhouse the wall (top width 1.0m, bottom width 3 m) 5 test layer heat is gradually increased from first to fifth, the two levels of greenhouse temperature change trend in the same soil wall; continuous fine weather (December 30, 2015 - January 2, 2016), the 5 layer of 1# thick wall temperature test chamber and 2# thin the average daily room wall temperature heat storage were 1971.2 K J and 1888.9 K J, the average heat release were 808.1 kJ and 763.1 kJ, the difference between 1# and 2# in greenhouse heat storage and heat release were 82.3 K J and 45 K J, the numerical difference is very small. Overcast weather (January 2016 4 - 6 days) two days before the thin cloud layer and some scattered light, the heat storage capacity of 1# and 2# in greenhouse is very small, the third day of thick clouds, scattered light is very weak, the heat storage capacity or even zero, is exothermic heat all day long, the average was 1551.4 K J and 935.5 K J, two of the greenhouse difference was 615.9 K J, numerical differences; although the greenhouse heat release was significantly higher than that of thick wall thin wall heat, but the average distance between the wall surface temperature at 0.1 M is only 0.6 degrees Celsius, the temperature in the greenhouse in front of the difference is smaller. The effect of maintaining the minimum temperature in the whole greenhouse is very small. 3. different weather conditions in the solar greenhouse wall 5 test layer of radiation heat distribution and wall heat transfer based on distribution characteristics of cloudy, cloudy, sunny weather haze and greenhouse 2# 5 layer test data collection, analysis of the test layer to receive solar radiation distribution. The results show that outdoor weather conditions have great influence on solar radiation intensity in greenhouse. The amount of solar radiation in sunny weather when the wall test layers accept was significantly higher than that in cloudy and mild haze, heavy haze (test day PM2.5 index 253) and cloudy accept the amount of radiation is very small. The solar radiation from different heights of the wall surface is second from the top to the bottom, the test layer is the largest, followed by the third test layer, 2 and 3, the radiation level of the test layer is relatively close, and the second is fourth, first and fifth test layer. At the same time, based on the different weather wall 5 test data acquisition layer, analyzed the 5 test layer and the back wall outside the room for heat distribution characteristics. The results show that the heat transfer from the north wall 1~5 test layer of total heat transfer ratio is as follows: first the test layer (wall thickness of 147 cm) is about 21%, second test layer (wall thickness of 186 cm) is about 19%, third test layer (wall thickness of 224 cm) is about 17%, fourth the test layer (wall thickness of 263 cm) is about 14%, fifth test layer (wall thickness of 300 cm) is about 12%, the back surface is about 17%; the greenhouse heat transfer to the outside from low to high in the enhancement, therefore, insulation measures should be strengthened with. 4. build the model of solar greenhouse wall temperature field based on finite element analysis software ANSYS to build a computing model for the solar greenhouse wall temperature field of the wall to measured temperature as degrees of freedom constraint imposed on the model boundary, the steady-state heat transfer method, simulated cloudy sunny conditions at different wall temperature change, and the simulation data and the measured data were compared, results showed that die
【學(xué)位授予單位】：山東農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：S625.1

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