共查询到13条相似文献,搜索用时 15 毫秒
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Xia Jiliang Xin Mingdao Zhang Hongji 《保鲜与加工》1989,(5):20-26
A numerical analysis is carried out for the unsteady and steady, two-dimensional, laminar natural convection heat transfer in a square partial cavity. The partial cavity consists of two horizontal adiabatic surfaces, a vertical hot surface and a cold surface with varied opening. The results are obtained for Ra = 10~3-10~6 and Y0 = 0.0-1.0. This study shows that the opening size has significant effect on the flow and heat transfer in partial cavity, and the. extent of its effect changes with different Rayleigh numbers. 相似文献
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Lin Chengxian Xin Mingdao Zhang Hongji 《保鲜与加工》1991,(6):1-7
A numerical study is carried out for the combined heat transfer of turbulent natural convection and surface radiation in an two-dimensional open square cavity with only one heated wall. The results show that the radiation significantly affects the velocity and temperature fields,and it can reduce the turbulent natural convection heat transfer as well as enhance it. For different Rayleigh number and temperature difference ratio,the overall heat transfer rates and the portion of radiation present different variation patterns. 相似文献
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Cao Jiming Xia Jiliang Xin Mingdao 《保鲜与加工》1992,(6):85-91
The present paper decribes numerical analytical results of natural convection in a closed cavity partially filled with porous medium by means of Forchheimer-Brinkman model. The effects of heated rate,permeability,height of porous region,heat conduction coefficients and aspect ratio on flow and heat transfar in the cavity are systematically investigated. Velocity and temperature fields in the cavity are given and dependence of average Nu on time is obtained. 相似文献
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This paper discusses the mechanism of the reduction ofheat flux through a roof pond with floating plants.A thermal model ispresented and the analytical results are obtained.The results are ingood agreement with the experimental observation. 相似文献
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Zhang Hongji Li Longjian 《保鲜与加工》1992,(2):32-39
The effect of the convective heat transfer in the entrance region of the tube on the temperature field and the maximum temperature of the tube material in the tube -mouth region of the high temperature heat exchange equipment is examined by numerical analysis. The computations on the basis of four different formulas for convection heat transfer coefficient are performed. The computed results indicate that the efect can not be ignored as for heat protection of the tube -mouth region and it is resapnable and secure that the mean convective heat transfer coefficient with taking account of the effect of the entrance region is used in the thermal design of the tube -mouth region. 相似文献
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Li Longjian Zhang Hongji 《保鲜与加工》1991,(2):79-84
In this paper the heat transfer in the tube-mouth region of the high temperatur heat exchange equipment is deeply analysed. The effect; of the heat conducting cross-section area of the tube-mouth region and axial heat conduction along the tube on the temperature field is emphatically examined by numerical computation, and then the relation of the highest temperature in the tube with the elongated tube length is established. The computed results in this paper are compared with those without taking account of these two factors. It is shown that the effect can not be ignored for the corrosion-protection by controlling temperature. 相似文献
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Zeng Xin Xin Mingdao Zhang Daming 《保鲜与加工》1992,(2):40-45
The one-dimensional heat transfer of microwave thawing in a food analogue material is experimentally studied. The results show that the phase change region is narrow and the latent heat is quickly released due to the effect of the microwave energy. Besides, in the rising section of the temperature after thawing. the internal heat source makes the temperature at the central point rise more quickly than that at other parts of the tested element. 相似文献
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Li Yourong 《保鲜与加工》1991,(5):64-68
A second law analysis is carried out on convective heat transfer through a horizontal annulus with constant heat flux. The entropy generation rate expression is obtained,and the influence of heat transfer across a finite temperature difference and fluid friction on the entropy generation rate is discussed. The optimum geometric parameters of a horfzontal annulus is found for which the entropy generated is minimum. The optimum fluid velocity which corresponds to the optimum geometric parameters is recommended. 相似文献
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Da Yang Xin Mingdao 《保鲜与加工》1989,(5):27-34
An analytical model was proposed for the condensation heat transfer on the horizontal low-finned tube attached by a porous drainage strip, and compared with the experimental data with a good agreement. The permeability of the porous drainage strip was also experimentally determined. 相似文献
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The exact three di me nsional temperatu re distribution and thermal analysiS to inte-grated circuit substrates have been presen ted by means of numerical method of a fin ite difference.Thismethed.which will overcome the di fficuItv of mathematical deduction mav be consltieredas an analytical way aided by com puters for thermal design of electron ic compon ents. 相似文献