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首页> 美国卫生研究院文献>Materials >Change in Conductive–Radiative Heat Transfer Mechanism Forced by Graphite Microfiller in Expanded Polystyrene Thermal Insulation—Experimental and Simulated Investigations
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Change in Conductive–Radiative Heat Transfer Mechanism Forced by Graphite Microfiller in Expanded Polystyrene Thermal Insulation—Experimental and Simulated Investigations

机译：膨胀聚苯乙烯绝热材料中石墨微填料强制传导-辐射传热机理的变化-实验和模拟研究

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This article introduces an innovative approach to the investigation of the conductive–radiative heat transfer mechanism in expanded polystyrene (EPS) thermal insulation at negligible convection. Closed-cell EPS foam (bulk density 14–17 kg·m ) in the form of panels (of thickness 0.02–0.18 m) was tested with 1–15 µm graphite microparticles (GMP) at two different industrial concentrations (up to 4.3% of the EPS mass). A heat flow meter (HFM) was found to be precise enough to observe all thermal effects under study: the dependence of the total thermal conductivity on thickness, density, and GMP content, as well as the thermal resistance relative gain. An alternative explanation of the total thermal conductivity “thickness effect” is proposed. The conductive–radiative components of the total thermal conductivity were separated, by comparing measured (with and without Al-foil) and simulated (i.e., calculated based on data reported in the literature) results. This helps to elucidate why a small addition of GMP (below 4.3%) forces such an evident drop in total thermal conductivity, down to 0.03 W·m ·K . As proposed, a physical cause is related to the change in mechanism of the heat transfer by conduction and radiation. The main accomplishment is discovering that the change forced by GMP in the polymer matrix thermal conduction may dominate the radiation change. Hence, the matrix conduction component change is considered to be the major cause of the observed drop in total thermal conductivity of EPS insulation. At the microscopic level of the molecules or chains (e.g., in polymers), significant differences observed in the intensity of Raman spectra and in the glass transition temperature increase on differential scanning calorimetry(DSC) thermograms, when comparing EPS foam with and without GMP, complementarily support the above statement. An additional practical achievement is finding the maximum thickness at which one may reduce the “grey” EPS insulating layer, with respect to “dotted” EPS at a required level of thermal resistance. In the case of the thickest (0.30 m) panels for a passive building, above 18% of thickness reduction is found to be possible.
机译：本文介绍了一种创新的方法来研究在对流可忽略不计的情况下膨胀聚苯乙烯（EPS）绝热材料中的传导-辐射传热机理。面板形式（厚度为0.02–0.18 m）的闭孔EPS泡沫（体积密度为14–17 kg·m）使用1–15 µm石墨微粒（GMP）在两种不同的工业浓度（最高4.3％）下进行了测试的EPS质量）。发现热流量计（HFM）足够精确，可以观察到所研究的所有热效应：总热导率对厚度，密度和GMP含量以及热阻相对增益的依赖性。提出了总导热系数“厚度效应”的另一种解释。通过比较测量（有铝箔和无铝箔）和模拟（即根据文献报道的数据计算）结果，可以分离出总热导率的传导-辐射成分。这有助于阐明为什么少量添加GMP（低于4.3％）会导致总热导率明显下降至0.03 W·m·K的原因。如所提出的，物理原因与通过传导和辐射的热传递机理的改变有关。主要成就是发现聚合物基质热传导中GMP强迫的变化可能主导辐射变化。因此，基质导电成分的变化被认为是EPS绝缘材料总导热系数下降的主要原因。在比较带有或不带有GMP的EPS泡沫时，在分子或链的微观水平（例如，在聚合物中），差示扫描量热法（DSC）热分析图观察到的拉曼光谱强度和玻璃化转变温度均出现明显差异，补充支持以上说法。另一项实际成就是，在所需的热阻水平下，相对于“点状” EPS，找到了可以减少“灰色” EPS绝缘层的最大厚度。在用于被动式建筑的最厚面板（0.30 m）的情况下，可以将厚度减少18％以上。

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