共查询到18条相似文献,搜索用时 46 毫秒
1.
2.
讨论了软质聚氨酯泡沫塑料对流判据的低温传热机理.根据软质聚氨酯泡沫塑料结构简图,将各种参数和低温数据带入对流判据公式,得到对流判据L的计算结果.计算了软质聚氨酯泡沫塑料的低温热导率.为了与计算的低温热导率比较,采用测试硬质泡沫塑料热导率的稳态热流双试样保护热板装置,测试了软质聚氨酯泡沫塑料的低温热导率,最后给出了低温热导率与温度关系曲线.根据试验,讨论了低温热导率的影响因素如温度、密度、吸水率等. 相似文献
3.
4.
5.
一、引言在测量热导率的实验中,最普遍采用的方法是稳态法,即在保持被测样品各点温度不随时间变化的情况下测量热流,然后求出热导率。这种方法实验条件要求严格,不易测准。本文介绍一种热导率测量的新方法,即动态法:样品上各点的温度可以随时间发生规律性变化,再利用这种规律来求样品的 相似文献
6.
7.
8.
9.
聚氨酯泡沫材料具有密封、隔热及绝缘等优良性能而在支撑及包装材料中得到广泛应用。作为支撑和包装材料,其压缩力学性能是重要的性能参数之一。聚氨酯泡沫属于粘弹性材料,其压缩力学性能不但与温度有关,而且还应与应变速率有关。本文测试了同种配方3种发泡密度的聚氨酯泡沫塑料试件在不同应变速率下的压缩力学性能,研究了3种密度聚氨酯泡沫塑料压缩力学性能随应变速率变化的规律。 相似文献
10.
为了保护臭氧层,用于生产聚氨酯泡沫的CFC-11发泡剂已经被淘汰,新开发的环境友好型聚氨酯泡沫用于低温设计时缺乏热物理性质数据的支持。文中介绍了开发的三套实验测试系统,以对热导率、线性膨胀系数和比热容这三大热物性在从室温到低温一个宽广的制冷及低温温度区间内进行测试。测试系统采用多项措施保证低温测试所需要的真空环境及漏热问题,保证了测试的顺利进行,以期提供制冷工程设计急需的低温热物性数据,并对泡沫的生产工艺进行优化。 相似文献
11.
12.
《Journal of Macromolecular Science: Physics》2013,52(5):1097-1110
The thermal conductivity of polymers in the solid and molten phases, as functions of temperature and pressure, is an essential parameter to permit simulation of polymer processing by computer-aided engineering (CAE). A key factor for the thermal conductivity when used in CAE is the Bridgman parameter (g) as a function of temperature. This is experimentally examined for polystyrene (PS) and polycarbonate (PC) in this paper. It was demonstrated that the thermal conductivity results under pressure were well described by the Eiermann's equation. First, the product of the Bridgman parameter (g) and the compressibility (β) as a function of temperature was calculated by fitting the experimental values with the Eiermann's equation. Second, the compressibility (β) as a function of temperature was estimated from the slope, in a plot of specific volume as a function of pressure. Finally, the Bridgman parameter (g) as a function of temperature was obtained from the two previous figures. The Bridgman parameters from the experiments are discussed by comparing them with those from Eiermann's theoretical model. 相似文献
13.
Cédric Bernardin 《Journal of statistical physics》2008,133(3):417-433
We consider a d-dimensional disordered harmonic chain (DHC) perturbed by an energy conservative noise. We obtain uniform in the volume upper
and lower bounds for the thermal conductivity defined through the Green-Kubo formula. These bounds indicate a positive finite
conductivity. We prove also that the infinite volume homogenized Green-Kubo formula converges. 相似文献
14.
导热系数测定设计性实验 总被引:2,自引:0,他引:2
导热系数测定是大学物理热学中比较重要的实验,对稳态法测量不良导体导热系数的原理和实验方法进行研究,对于不同形态的导热材料,提出了几种可行的实验方案。实验内容和测量结果符合设计性实验要求,有助于启发学生的创新意识。 相似文献
15.
16.
17.