硬质聚氨酯泡沫塑料导热特性研究

Research on thermal conductivity of rigid polyurethane foams

通过自行搭建的实验台,利用稳态法研究了硬质聚氨酯泡沫塑料的传热特性。在常温常压(25℃,101 kPa)下,对硬质聚氨酯泡沫塑料的不同发泡部位进行导热系数测试,同时对聚氨酯样品不同发泡部位的密度、孔隙率、开孔率、孔径等参数进行测量和表征。结果表明,通过预聚体法发泡工艺制作的硬质聚氨酯泡沫塑料不同发泡部位的结构参数和传热特性有差异。聚氨酯样品密度中间层小、边界处大,且聚氨酯发泡材料导热系数与孔隙率、开孔率、孔径等微观结构参数相关,制作工艺或人为原因造成的开孔率会强化气体导热和辐射换热,有效导热系数提升了7%~12%。最终提出一种改进的硬质聚氨酯泡沫塑料导热系数理论计算模型,模型中考虑了开孔率对气体导热和材料消光系数的影响,改进模型和实验值能实现较好的吻合。

Heat transfer characteristics of rigid polyurethane foam were studied by the steady-state method on a self-built test bench.At normal temperature and pressure(25℃,101 kPa),the thermal conductivity of different parts of rigid polyurethane foam was tested.Additionally,the density,porosity,aperture ratio and pore size of different parts of polyurethane sample were measured and characterized as well.The results show that the structural parameters and heat transfer characteristics of rigid polyurethane foams made by prepolymer foaming process are different in different foaming parts.The polyurethane sample has a small density in the middle and a large density at the boundary,and the thermal conductivity of the polyurethane foaming material is related to the poros⁃ity,aperture ratio,pore size and other microstructure parameters.The aperture ratio caused by the production process or human causes will enhance the gas thermal conductivity and radiation heat transfer,leading to an increase by 7%-12%of the effective ther⁃mal conductivity.Finally,an improved theoretical calculation model for thermal conductivity of rigid polyurethane foamed plastics was proposed,in which the effect of open porosity on thermal conductivity of gas and extinction coefficient of material was consid⁃ered.And the improved model agrees well with the experimental results.