Numerical Simulation On Refrigerator Mold Filling Processes With Rigid Polyurethane Foams

Rigid polyurethane foam has excellent thermal isolation property, resistance of water penetration, chemical stability and light weight, easily molded. So PU is indispensable material for refrigerator insulation material. For the refrigerator door by filling with rigid polyurethane foam is easy to produce deformation after ejection. This work solves the problem by using numerical simulation method. Starting the research of polyurethane foam by the chemical reaction kinetics, understanding the mechanism of polyurethane formation, and get the key parameters that have large effect on foam properties from numerical simulation.We use rheological theory researching polyurethane foam mold filling process based on FLUENT, choose SIMPLE algorithm and the VOF model. Establish the mathematical model of polyurethane foam material. Establish the user defines scalar functions to compute the degree of chemical reaction. Taking into account the exothermic chemical reactions and endothermic physical blowing agent evaporation. We use UDF program to definition the material parameters and the source term of the control equations. Simplify the foaming process as a non-steady laminar flow process. Compute the degree of chemical reaction and fluid flow separately. Put 2.16kg polyurethane mixture in the 2-dimensional rectangular region. After 40s, we can get the temperature and density distribution. Its density down to about 30kg/m3, the highest temperature of the mixture rose to 137.8014℃, the crosslinking reaction temperature rose to 153.5989℃after 100s. The chemical reaction does highly exothermic.Measure the deformation of the refrigerator door and the physical parameters of polyurethane samples. Using a high precision caliper and optical platforms, adjust the three vertices of the refrigerator door to a horizontal plane, measure the deformation of the refrigerator door, the maximum deformation of the two doors are 2.56mm and 2.42mm. The density of the polyurethane sample inside the door is about 42.6037kg/m3, the thermal conductivity is about 0.02626W/(m·K), the specific heat capacity of about 2380.455J/(kg·K).Finally, use ABAQUS, analyze the cooling process of the polyurethane foam layer and the refrigerator door assembly, acquire the temperature field, thermal deformation. Thermal analysis showed that the shell of the refrigerator door has little effect on the temperature of the cooling process. The deformation of polyurethane foam during the cooling process is raised to the inside of the door. The deformation of the door is raised to the outside of the door's glass board. The deformation trends are same with the measured line. The results show that the shell of the door has seriously effect on the deformation of the door. The simulation results and measurement results are different because of the simplified simulation model, material parameters and other factors. When the polyurethane foam is not limited by the shell, the shrinkage is very obviously. 5mm tempered glass effectively resisted the shrinkage near the polyurethane. But the white HIPS board is not well enough to resist the shrinkage. Therefore, the trend of deformation is to shrink toward the center.Polyurethane foam is extremely difficult to decompose. Then the foam pollutes the environment. The research results will improve the quality of the refrigerator while reducing environmental pollution. And for the development of rigid polyurethane industries of our country, provide a cleaner, less cost, more environmentally friendly way.