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Heat radiation equation contains 4th exponential order of temperature which makes mathematics analysis very complicated and troublesome. Therefore, most heat transfer experts and scholars believe, based on their own experiences, that the heat radiation effect can be ignored due to small temperature difference between insulated surfaces and surrounding to simplify analysis. Due to this reason, insulation examples shown in most heat transfer, air conditioning and refrigeration text books, and some commercial packages for the design of insulations, commonly ignore the effect of heat radiation. However, this paper demonstrates that the heat radiation effect can not be ignored in the situations of thin insulation with low ambient convective heat coefficient and a large surface emissivity. In those situations, ignoring the heat radiation will result in an inaccurate insulation design. The paper also shows that a smaller insulated surface emissivity can largely promote the insulation effect. [ABSTRACT FROM AUTHOR]

A model of heat transfer through greenhouse covering materials was developed in this study. The influences of the thermal properties of covering materials, the construct parameters of greenhouse and the environment inner and outer of greenhouse were completely considered in the model. Heat transfer flux density through covering layer can be simulated and forecasted by using this model. The simulated values of heat transfer flux density through covering layer were in accordance with the values got from some experiments. This model can be used for many purposes, such as greenhouse design, analysis and control for thermal environment in greenhouse. [ABSTRACT FROM AUTHOR]