模擬太陽能追蹤器位於地表和建築物屋頂的流場模擬; Flow Simulation Over A Solar Tracker On The Ground Surface And On The Rooftop of A Building

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Title:	模擬太陽能追蹤器位於地表和建築物屋頂的流場模擬;Flow Simulation Over A Solar Tracker On The Ground Surface And On The Rooftop of A Building
Authors:	廖冠翔;Liao,Kuan-Hsiang
Contributors:	機械工程學系
Keywords:	太陽追蹤器;表面受力分布;渦流曳放現象;LES紊流模型;Solar tracker;force distribution on surface;vortex shedding;LES turbulence model
Date:	2013-07-29
Issue Date:	2013-08-22 12:14:49 (UTC+8)
Publisher:	國立中央大學
Abstract:	太陽追蹤器(solar tracker)安裝在戶外故需考量風力影響、表面受力分布及周圍流場現象，本文針對台灣地區追蹤器常見安裝位置（仰角α=30o，方位角ψ=0o-180o）進行模擬，數值解針對大型追蹤器置放於地面與在風洞的追蹤器模型實驗數據做比較，此外也分析太陽追蹤器置放於建築物平面屋頂時的氣流場。目前追蹤器的氣流場分析研究很缺乏，本文模擬旨在提供有意義的分析和增進對流場現象的瞭解。本文以ANSYS FLUENT軟體模擬大型太陽追蹤器流場，論文的研究重點包括：比較LES紊流模型與RNG k-ε紊流模型模擬結果不同、計算太陽光電板表面截線壓力係數(cp)分布、上下表面合力及合扭矩及特定方位角產生的渦流曳放現象，並探討大型追蹤器置放於地面及建築物平面屋頂時之流場差異。研究發現LES紊流模型相較於RNG k-ε紊流模型，對追蹤器表面的cp分布更能有效預測，對渦流的預測範圍更廣泛且較合理，故本文採用LES紊流模型。其中紊流數值解對大型追蹤器置放於地面的迎風面cp分布與追蹤器模型置放於地面實驗數據相當吻合，背風面數值解與實驗值二者的變化趨勢大致相仿。考量建築物影響時，大型追蹤器置放於建築物平面屋頂位於仰角α=30o，與不同方位角（ψ=0o、30o及150o），追蹤器後方會產生渦流曳放現象，而大型追蹤器置放於地面對應發生渦流曳放的方位角則略為不同（ψ=60o及150o）。紊流數值解對斜面30o屋頂與大型追蹤器置放於建築物平面屋頂ψ=0o, α=30o呈現明顯不同流場特性，斜面屋頂表面徑線沿屋頂上表面爬升且屋頂左右兩側流速極快；大型追蹤器置放於建築物平面屋頂受建築物干擾影響明顯，徑線圖顯示大型追蹤器周圍有渦流，約大型追蹤器高度2 m以上為流速較快區域。 It is common that the solar tracker installed with elevation angle (α) and azimuth angle (ψ) corresponding to the values of 30o and 0o-180o respectively in Taiwan. As the solar tracker is operated outdoor, it is important to consider effects of the wind load on surface and aerodynamics around it. This numerical simulation analyzed and compared two cases (the full-scale large tracker installed on ground and its reduced model in wind tunnel). In addition, the aerodynamics of the same full-scale large tracker installed on the flat roof of a four-story building was simulated. Because of short of research in aerodynamics of solar tracker, this study aims to provide meaningful analysis and enhance the understanding of flow physics over solar tracker. This study used ANSYS FLUENT to simulate the flow over solar tracker and several issues were investigated, including comparison between LES and RNG k-ε turbulence models, the distribution of pressure coefficient (cp) on the photovoltaic (PV) panel, resulting aerodynamics forces and moments over the PV panel, and vortex shedding on specific azimuth angles. The comparison between the large solar tracker installed on the ground and on the rooftop of building was focused on their flow characteristics. Results shown that prediction with LES model can resolve better in cp and capture wide variation of vortex. Accordingly, this paper uses the LES turbulence model. Numerical solutions of windward surface of the large tracker on ground were in good agreement with its reduced model in wind tunnel experiment. Considering building effect on the solar tracker, vortex shedding was predicted occur at downstream of large tracker at 30o elevation angle and different azimuth angles (ψ=0o, 30o and 150o), while the vortex shedding occur at ψ=60o and 150o when the solar tracker placed on ground. Turbulent simulation shown significant difference between the building with inclined roof of 30o and the tracker placed on the building with flat roof at 30o elevation angle. Very fast flow at the lateral sides of inclined roof and the flow pathline stretch above the inclined surface was predicted. While the case of tracker installed on the building, due to interference of building on the tracker, there were vortices surround the tracker and a region of higher velocity at 2 m above the tracker.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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