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Optimal Study on Heat Transfer Performance of the Wall and the Window for Solar House

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Tutor: DingGuoZhong
School: Huazhong University of Science and Technology
Course: Refrigeration and Cryogenic Engineering
Keywords: Solar house,Heat transfer characteristic,decrement factor,Time lagOptimization
CLC: TU111.4
Type: Master's thesis
Year:  2012
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Abstract:
In today¡¯s increasingly severe energy crisis, the efficient use of solar energy is one ofthe focuses. Solar house is one way of using solar energy, but the energy saving effect islimited by the solar energy¡¯s instability. This instability can be reduced through areasonable design and selection of solar house maintenance structure. In the maintenancestructure, the wall and window affect thermal performance of the solar house significantly.Researchers at home and abroad have done many researches about this, but the wall andwindow heat transfer optimization rarely have been studied and carried out throughsimulation. Since the use of mathematical calculation software and fluid simulationsoftware in the analysis of the heat transfer characteristics of the solar house becomepopular, there is a need for researcher to establish a model to analyze the wall¡¯s andwindow¡¯s impact on the heat transfer characteristics of solar house, in order to optimize itsheat transfer performance.In the article, the numerical methods was applied to study the heat transfercharacteristics of the wall for solar house, the decrement factor and time lag have beenanalyzed. One-dimensional transient heat conduction equation was solved using softwareunder convection boundary conditions. To the outer surface of the wall, periodic boundaryconditions were applied. The results are as following:1. The total thickness of the wall remains unchanged, its decrement factor did notchange significantly, the time lag was lowest when the thickness of air-layer is0.06m.2. The thickness of polyurethane board remains unchanged, the decrement factor andtime lag is proportional to the thickness of the air-layer.3. The thickness of air-layer remains unchanged, the decrement factor before0.04mdid not change significantly, after this point it increases with polyurethane board¡¯sthickness; the turning points of Time lag was about0.04m.It was found that insulation thickness has a very profound effect on the time lag and decrement factor.The theoretical analysis and software simulation of the heat exchanger inside theinsulating glass has been studied. Theoretical analysis shows that the flow pattern of airinside the glass was different annular flow. As the air-layer thickness decreases, it becomesmonocyclic flow, the heat transfer performance was optimal. The calculated optimalthickness of air-layer under the Wuhan regional climate conditions was between14-16mm.FLUENT simulation results show that the velocity vector and temperature diagram isconsistent with the theoretical prediction.Based on the previous work, the optimal relation of walk thickness and the thicknessof air-layer in the hollow glass was selected, in order to study the optimal thickness of thewall, to provide useful guidance for analyzing the proper thickness of air-layer.
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