本文選題：室外熱環(huán)境數(shù)值仿真　切入點：下墊面　出處：《華南理工大學(xué)》2013年碩士論文

【摘要】：在室外熱環(huán)境分析中，正確描述下墊面對太陽輻射的吸收是一個重要前提，由于下墊面換熱是集太陽輻射吸收、喬木樹冠遮陽、含水表面蒸發(fā)冷卻、空氣對流傳熱和大氣長波輻射的耦合換熱過程，在利用大型商業(yè)CFD軟件進(jìn)行室外熱環(huán)境數(shù)值解析時，對這種復(fù)雜換熱過程的邊界條件進(jìn)行數(shù)值解析是非常困難，計算機(jī)時成幾何級增長，收斂難度也大大增加。目前工程中常用建成區(qū)下墊面實測溫度作為熱環(huán)境分析的邊界條件，對規(guī)劃方案進(jìn)行數(shù)值預(yù)測，雖然這種做法可以簡化數(shù)值計算過程，但是建成區(qū)的下墊面鋪裝與規(guī)劃方案只是一定程度的類似，計算結(jié)果誤差較大。本文在下墊面熱平衡方程的基礎(chǔ)上，綜合考慮下墊面水分蒸發(fā)散熱和喬木樹冠遮陽對下墊面太陽輻射吸收的影響，提出等效太陽輻射吸收系數(shù)，簡化大型商業(yè)CFD軟件中邊界條件的設(shè)置，縮短計算機(jī)時，提高數(shù)值解析結(jié)果的工程可信度。 首先，本文介紹目前國內(nèi)外下墊面換熱邊界條件研究現(xiàn)狀，重點介紹大型商業(yè)CFD軟件在模擬室外熱環(huán)境的優(yōu)勢，以及在處理室外熱環(huán)境時下墊面邊界層設(shè)定遇到的問題，提出解決思路。其次，在傳熱與傳濕控制方程的基礎(chǔ)上，對透水地面、草地和植林地三種典型下墊面鋪裝方式的換熱過程進(jìn)行數(shù)值解析，推導(dǎo)下墊面溫度和等效太陽輻射吸收系數(shù)的計算模型。第三，通過對下墊面逐時溫度與實測溫度的比較分析，驗證下墊面溫度計算模型的可靠性和準(zhǔn)確性。分析表明，模擬值與實測值吻合較好，相關(guān)度在0.98以上，最大相對誤差均在7%以內(nèi)。第四，將等效太陽輻射吸收系數(shù)的計算值作為下墊面邊界條件對太陽輻射吸收的等效轉(zhuǎn)換，對對比分析的測試環(huán)境進(jìn)行整體熱環(huán)境數(shù)值仿真。分析表明，模擬值與實測值吻合較好，最大溫度偏差在2℃以內(nèi)，最大相對誤差均在5%以內(nèi)。最后，分析三種下墊面鋪裝方式的等效太陽輻射吸收系數(shù)的影響因素，得出提高草地葉面積密度，提高透水性下墊面的含濕量和縮小喬木間距使增大陰影率和增加喬木葉面積密度，能減少等效太陽輻射吸收系數(shù)，提高喬木對地面的陰影率對減少等效太陽輻射吸收系數(shù)效果更為顯著。 等效太陽輻射吸收系數(shù)比較客觀地描述下墊面蒸發(fā)冷卻和喬木樹冠遮陽的對室外熱環(huán)境的影響，該系數(shù)的提出為工程界對小區(qū)規(guī)劃方案的熱環(huán)境進(jìn)行快速分析提供了可能，，具有重要的工程應(yīng)用價值。
[Abstract]:In the analysis of outdoor thermal environment, it is an important prerequisite to correctly describe the absorption of solar radiation from the underlying surface. Because the heat transfer of the underlying surface is the absorption of solar radiation, the canopy of the tree is shaded, and the surface of the water is evaporated and cooled.In the coupled heat transfer process of air convection and atmospheric long wave radiation, it is very difficult to analyze the boundary conditions of this complex heat transfer process by using commercial CFD software.Computer time into geometric level growth, convergence difficulty is also greatly increased.At present, the measured temperature of the underlying surface of the built area is used as the boundary condition for the thermal environment analysis, and the planning scheme is predicted numerically, although this method can simplify the process of numerical calculation.However, the underlying surfacing of the constructed area is only similar to the planning scheme to some extent, and the error of calculation results is large.Based on the heat balance equation of the underlying surface and considering the effects of water evaporation and canopy shading on the solar radiation absorption of the underlying surface, an equivalent solar radiation absorption coefficient is proposed in this paper.The setting of boundary conditions in large-scale commercial CFD software is simplified and the engineering reliability of numerical analysis results is improved when the computer is shortened.Firstly, this paper introduces the current situation of the research on the heat transfer boundary conditions of the underlying surface at home and abroad, and focuses on the advantages of the large-scale commercial CFD software in simulating the outdoor thermal environment, and the problems encountered in the setting of the underlying surface boundary layer when dealing with the outdoor thermal environment.The solution is put forward.Secondly, based on the governing equations of heat transfer and moisture transfer, the heat transfer process of three typical underlying surface paving modes, namely, permeable ground, grassland and planted forest land, is analyzed numerically, and the calculation model of underlying surface temperature and equivalent solar radiation absorption coefficient is derived.Thirdly, the reliability and accuracy of the model are verified by comparing the hourly temperature of the underlying surface with the measured temperature.The analysis shows that the simulated value is in good agreement with the measured value, the correlation degree is more than 0.98, and the maximum relative error is less than 7%.Fourthly, the calculated values of the equivalent solar radiation absorption coefficient are taken as the equivalent transformation of the underlying surface boundary conditions to the solar radiation absorption, and the overall thermal environment numerical simulation is carried out for the test environment compared and analyzed.The analysis shows that the simulated value is in good agreement with the measured value, the maximum temperature deviation is less than 2 鈩

本文編號：1704061