內(nèi)置式PV-Trombe墻空氣流動(dòng)與傳熱的數(shù)值模擬
發(fā)布時(shí)間：2018-08-02 08:47
【摘要】：綠色建筑技術(shù)利用新能源和可再生能源進(jìn)行供暖通風(fēng)和空氣調(diào)節(jié),具有節(jié)能環(huán)保的優(yōu)點(diǎn),是近年來國內(nèi)外的研究熱點(diǎn)課題。Trombe墻是一種利用太陽能進(jìn)行供暖和通風(fēng)的建筑節(jié)能技術(shù)。PV-Trombe墻則通過把太陽能電池貼于Trombe墻玻璃蓋板,從而實(shí)現(xiàn)了發(fā)電和供暖、通風(fēng)的聯(lián)供。然而太陽能電池阻礙了太陽輻射進(jìn)入Trombe墻流道內(nèi)部,從得熱率的角度看,Trombe墻的太陽能利用效率將降低。為了更好地利用太陽能,本文提出了一種新型內(nèi)置式PV-Trombe墻,它將光伏電池貼在Trombe墻的集熱墻表面,太陽輻射完全穿過玻璃蓋板進(jìn)入Trombe墻內(nèi),并被集熱墻表面的光伏電池和通道內(nèi)的空氣所吸收。其中,一部分太陽能被轉(zhuǎn)換成電能,其余部分則用于加熱通道內(nèi)的空氣,實(shí)現(xiàn)建筑采暖、通風(fēng)和發(fā)電等功能。本文以水平進(jìn)口內(nèi)置式PV-Trombe墻為研究對(duì)象,基于計(jì)算流體力學(xué)原理,運(yùn)用FLUENT軟件對(duì)模型流道內(nèi)的空氣流動(dòng)情況和對(duì)流換熱特點(diǎn)進(jìn)行了模擬研究。采用rNG κ-ε湍流模型、DO輻射模型以及SIMPLEC算法對(duì)溫度場(chǎng)和流場(chǎng)進(jìn)行計(jì)算,得到了流道內(nèi)空氣溫度、壓力和速度分布的詳細(xì)結(jié)果。文中探討了太陽輻射和結(jié)構(gòu)尺寸對(duì)模型通風(fēng)和傳熱性能的影響,分析了流道內(nèi)部空氣的溫度、速度、流態(tài)、局部換熱系數(shù)和質(zhì)量流量以及模型熱電性能的變化情況。通過對(duì)各變量進(jìn)行量綱分析,引入無量綱準(zhǔn)則數(shù)Nu數(shù)、Re數(shù)、Ra*數(shù)和熱效率ηth等,基于最小二乘法原理,對(duì)各無量綱數(shù)進(jìn)行線性擬合分析,得到了表征內(nèi)置式PV-Trombe墻通風(fēng)傳熱性能的擬合關(guān)聯(lián)式。通過本文研究,得到以下主要結(jié)論：(1)流道內(nèi)部空氣沿著寬度方向,溫度與速度分布并不是均勻一致。在玻璃蓋板和光伏電池的近壁處,存在明顯的溫度和速度邊界層,邊界層厚度隨著太陽輻射的增強(qiáng)而增大,邊界層內(nèi)溫度梯度和速度梯度較大,而遠(yuǎn)離壁面的主流區(qū),溫度和速度變化較為平緩。(2)空氣在豎直流道內(nèi)流動(dòng)屬于有限空間自然對(duì)流,其流態(tài)可以用以流道寬度b為特征尺寸的Ra*數(shù)來判斷。通過流線圖和理論分析可知,空氣的流態(tài)隨著太陽輻射和高度的增加變化較小,而寬度才是影響流道內(nèi)空氣流動(dòng)狀態(tài)的關(guān)鍵參數(shù)。(3)流道內(nèi)空氣的局部對(duì)流換熱系數(shù)分布存在入口段和充分發(fā)展段兩個(gè)區(qū)段；太陽輻射和模型高度的增加有助于提高模型的通風(fēng)性能,而空氣質(zhì)量流量隨著寬度的增加卻出現(xiàn)先增大然后逐漸減小的情況；空氣在流道內(nèi)流動(dòng)產(chǎn)生的回流會(huì)增強(qiáng)局部對(duì)流換熱系數(shù),卻會(huì)阻礙空氣流動(dòng),降低模型通風(fēng)性能。(4) 已經(jīng)定義出表征模型的平均對(duì)流傳熱系數(shù)Nu數(shù)、表征模型通風(fēng)量大小的Re數(shù)、表征模型結(jié)構(gòu)尺寸和壁面熱流密度變化的Ra*數(shù)以及熱效率ηth,并通過線性擬合方法得到各無量綱數(shù)之間的通用冪函數(shù)關(guān)聯(lián)式,為模型計(jì)算和工程應(yīng)用提供參考。
[Abstract]:Green building technology uses new and renewable energy for heating, ventilation and air conditioning, which has the advantages of energy saving and environmental protection. Trombe wall is a kind of building energy saving technology using solar energy for heating and ventilation. PV-Trombe wall can realize the joint supply of power generation, heating and ventilation by attaching solar cells to Trombe wall glass panels. However, solar cells prevent solar radiation from entering the channel of Trombe wall, and the efficiency of solar energy utilization of Trombe wall will be reduced from the point of view of thermal efficiency. In order to make better use of solar energy, a new type of built-in PV-Trombe wall is proposed in this paper. The photovoltaic cell is attached to the surface of the collector wall of the Trombe wall, and the solar radiation is completely passed through the glass cover into the Trombe wall. It is absorbed by the photovoltaic cells on the surface of the collector wall and the air in the passage. Some of the solar energy is converted to electricity, while the rest is used to heat the air in the passage to provide building heating, ventilation and power generation. Based on the principle of computational fluid dynamics (CFD), the air flow and convection heat transfer characteristics in the model runner are simulated by using FLUENT software based on the horizontal inlet built-in PV-Trombe wall. The temperature field and flow field are calculated by using rNG 魏-蔚 turbulence model and SIMPLEC algorithm. The detailed results of air temperature, pressure and velocity distribution in the channel are obtained. The effects of solar radiation and structure size on the ventilation and heat transfer performance of the model are discussed. The variation of air temperature, velocity, flow state, local heat transfer coefficient and mass flow rate and the thermoelectric properties of the model are analyzed. Through dimensionality analysis of each variable, the dimensionless criterion number Nu and re number Ra* and thermal efficiency 畏 th are introduced. Based on the principle of least square method, linear fitting analysis is carried out for each dimensionless number. A fitting correlation is obtained to characterize the ventilation heat transfer performance of built-in PV-Trombe walls. The main conclusions are as follows: (1) the temperature and velocity distribution of the air in the channel is not uniform along the width direction. There are obvious temperature and velocity boundary layers in the near wall of the glass cover and photovoltaic cells. The thickness of the boundary layer increases with the increase of solar radiation. The temperature gradient and velocity gradient in the boundary layer are larger, but far from the mainstream area of the wall. The variation of temperature and velocity is relatively gentle. (2) the flow of air in vertical channel belongs to natural convection in finite space and its flow pattern can be judged by Ra* number of channel width b as characteristic size. According to the streamline diagram and theoretical analysis, the flow state of the air changes little with the increase of solar radiation and height. The width is the key parameter to affect the air flow state in the channel. (3) there are two sections of the local convection heat transfer coefficient distribution in the channel: the inlet section and the fully developed section; The increase of solar radiation and the height of the model helps to improve the ventilation performance of the model, but the air mass flow increases first and then decreases gradually with the increase of the width. The circumfluence caused by air flow in the channel will enhance the local convection heat transfer coefficient, but it will hinder the air flow and reduce the ventilation performance of the model. (4) the average convection heat transfer coefficient Nu number that characterizes the model and the re number representing the model ventilation rate have been defined. The Ra* number and the thermal efficiency 畏 _ (th) of the structural size and the wall heat flux change are characterized, and the general power function correlation between the dimensionless numbers is obtained by the linear fitting method, which provides a reference for the model calculation and engineering application.
【學(xué)位授予單位】：東華大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU83
本文編號(hào)：2158878
[Abstract]:Green building technology uses new and renewable energy for heating, ventilation and air conditioning, which has the advantages of energy saving and environmental protection. Trombe wall is a kind of building energy saving technology using solar energy for heating and ventilation. PV-Trombe wall can realize the joint supply of power generation, heating and ventilation by attaching solar cells to Trombe wall glass panels. However, solar cells prevent solar radiation from entering the channel of Trombe wall, and the efficiency of solar energy utilization of Trombe wall will be reduced from the point of view of thermal efficiency. In order to make better use of solar energy, a new type of built-in PV-Trombe wall is proposed in this paper. The photovoltaic cell is attached to the surface of the collector wall of the Trombe wall, and the solar radiation is completely passed through the glass cover into the Trombe wall. It is absorbed by the photovoltaic cells on the surface of the collector wall and the air in the passage. Some of the solar energy is converted to electricity, while the rest is used to heat the air in the passage to provide building heating, ventilation and power generation. Based on the principle of computational fluid dynamics (CFD), the air flow and convection heat transfer characteristics in the model runner are simulated by using FLUENT software based on the horizontal inlet built-in PV-Trombe wall. The temperature field and flow field are calculated by using rNG 魏-蔚 turbulence model and SIMPLEC algorithm. The detailed results of air temperature, pressure and velocity distribution in the channel are obtained. The effects of solar radiation and structure size on the ventilation and heat transfer performance of the model are discussed. The variation of air temperature, velocity, flow state, local heat transfer coefficient and mass flow rate and the thermoelectric properties of the model are analyzed. Through dimensionality analysis of each variable, the dimensionless criterion number Nu and re number Ra* and thermal efficiency 畏 th are introduced. Based on the principle of least square method, linear fitting analysis is carried out for each dimensionless number. A fitting correlation is obtained to characterize the ventilation heat transfer performance of built-in PV-Trombe walls. The main conclusions are as follows: (1) the temperature and velocity distribution of the air in the channel is not uniform along the width direction. There are obvious temperature and velocity boundary layers in the near wall of the glass cover and photovoltaic cells. The thickness of the boundary layer increases with the increase of solar radiation. The temperature gradient and velocity gradient in the boundary layer are larger, but far from the mainstream area of the wall. The variation of temperature and velocity is relatively gentle. (2) the flow of air in vertical channel belongs to natural convection in finite space and its flow pattern can be judged by Ra* number of channel width b as characteristic size. According to the streamline diagram and theoretical analysis, the flow state of the air changes little with the increase of solar radiation and height. The width is the key parameter to affect the air flow state in the channel. (3) there are two sections of the local convection heat transfer coefficient distribution in the channel: the inlet section and the fully developed section; The increase of solar radiation and the height of the model helps to improve the ventilation performance of the model, but the air mass flow increases first and then decreases gradually with the increase of the width. The circumfluence caused by air flow in the channel will enhance the local convection heat transfer coefficient, but it will hinder the air flow and reduce the ventilation performance of the model. (4) the average convection heat transfer coefficient Nu number that characterizes the model and the re number representing the model ventilation rate have been defined. The Ra* number and the thermal efficiency 畏 _ (th) of the structural size and the wall heat flux change are characterized, and the general power function correlation between the dimensionless numbers is obtained by the linear fitting method, which provides a reference for the model calculation and engineering application.
【學(xué)位授予單位】：東華大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU83
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 蘇亞欣;柳仲寶;;太陽能煙囪強(qiáng)化自然通風(fēng)的研究現(xiàn)狀[J];科技導(dǎo)報(bào);2011年27期
，本文編號(hào)：2158878
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