Research On Heat Transfer Characteristics Of GFRP Interfaces Under Vacumm Condition

GFRP(Glass Fiber Reinforced Plastic) is special composite material, which is made with glass fiber and synthetic resin. GFRP is used as support components of many storage and transport equipments such as cryogenic container, tanker, storage tanks. These cryogenic products use high vacuum multilayer insulation and the heat transfer through GFRP supports is dominant. When cryogenic products work, GFRP supports contact with stainless steel vessel which produces thermal resistance. The thermal resistance forms protective screen for heat transfer. The quantity of thermal resistance is important for the performance of cryogenic system. However, there are few relevant data. It has important reality meaning to explore the discipline of thermal contact conductance for GFRP interfaces.The combination of experimental research and theoretical analysis is used to research the thermal contact conductance of stainless steel/GFRP interface and GFRP/GFRP interface. First, the history and current situation of thermal contact conductance are reviewed. Previous research of thermal contact conductance focuses on metal contact interfaces. Many experimental results and theoretical models are gathered, which paves the road for the research in this paper.An experimental apparatus based on steady heat flux used for thermal contact conductance test is set up and detailed thermal analysis is performed. Ten test specimens are made. Five pairs are made of stainless steel/GFRP and other five pairs are made of GFRP/GFRP. Every pair has different surface roughness. Experimental research on thermal contact conductance for GFRP interfaces is done under vacuum condition. The effect of contact pressure, surface roughness, interface temperature, material properties on thermal contact conductance is analyzed. The range of contact pressure is from 4.81 MPa to 74 Mpa and the range of interface temperature is from 200 K to 335 K. Experimental data are compared with existing models( Bush elastic model, Mikic elastic model, Mikic plastic model and CMY model). Comparison results show that Bush elastic model agrees well with experimental data under large roughness and low pressure. When contact pressure increases, the deviation becomes larger and larger. For the four existing models, Bush elastic model has best prediction effect and Mikic plastic model and CMY model predict poorly. New models need to be developed.The number of contact spots and real contact area are deduced based on surface microscopic topography and asperity deformation. General equation for thermal contact conductance is obtained. Theoretical models for stainless steel/GFRP interface and GFRP/GFRP interface are established through regression analysis method.For 50m3 LNG tanker, detailed thermal analysis is performed using theoretical model of stainless steel/GFRP interface. Calculated heat flow through tanker is compared with experimental test value. The theoretical model is validated.Finally, “Hysteresis” effect is researched systematically. The emphasis is on the effect of surface roughness, interface temperature, material properties on thermal contact conductance. Theoretical analysis indicates that incomplete recovery of deformed asperity during unloading process is the intrinsic reason which causes “Hysteresis” effect.