Research on thermal conductivity of rigid polyurethane foams
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.
engineering thermophysicsporous materialheat transfer characteristicsSEMporosity
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