Analysis Of Heat Transfer Characteristics In The Melting Process Of Polyurethane Foam Film By The Deflagration Method

As a porous material with good mechanical properties,reticulated polyurethane foam has gradually become an important industrial product in people’s daily work and life.The deflagration method is the best method for removing the film of the polyurethane foam to obtain the reticulated polyurethane foam.However,there is still no theoretical guidance for the melting process of the polyurethane foam film.This paper uses a combination method of numerical simulation and experiment to explore the effects of the premixed gas parameters(the excess coefficient of premixed gas,gas type and gas concentration)and the polyurethane foam parameters(the pore diameter and film thickness)on the melting degree of the polyurethane film.This paper can provide theoretical basis for efficient and standardized production of reticulated polyurethane foam by the deflagration method.The main work of this paper is as follows:(1)According to the relevant specifications of the industrially produced reticulated polyurethane foam,the physical model of the cavity cell of polyurethane foam was established.The standard k-ε model was applied and the melting-solidification model based on the enthalpy-porosity method were used to establish the numerical calculation of the melting process of polyurethane foam.(2)According to the related production process of deflagration method for producing the reticulated polyurethane foam,the experimental platform for producing polyurethane foam were designed.The comparison between the experimental results and the numerical simulation results confirmed that the numerical calculation model of the melting process of polyurethane foam is feasible.(3)Based on the feasibility of the numerical calculation model in the polyurethane foam film melting process,the influence of the premixed gas characteristics on the melting process of polyurethane foam was simulated by FLUENT software.By studying the temperature distribution and liquid phase rate distribution of polyurethane foam under different premixed gas characteristics,the effects of the excess coefficient of the premixed gas,gas type and gas concentration on the film melting process were investigated.The results show that: the larger the amount of the premixed gas,the higher the calorific value of the gas will be,which finally resulted in the higher degree of the film melting of polyurethane foam;the polyurethane foam has the highest degree of melting when the gas concentration is equivalent concentration in the air.With the increase of the excess coefficient of the premixed gas,three different melting phenomena will occur in the polyurethane foam melting process.Through the analysis of the three melting phenomena,the excess coefficients of premixed gas corresponding to the best melting results of the polyurethane foam model considering in this paper were obtained.(4)Based on the feasibility of the numerical calculation model of the melting process of the polyurethane foam film the FLUENT was used to simulate the effects of polyurethane foam pore size and film thickness on the melting process of the polyurethane film.The results show that the larger the pore size of the polyurethane foam,the higher the average stabilized temperature of the outer surface will be;as the pore size increases,the time required for the temperature field in the polyurethane foam cavity to stabilize also increased.The thicker the thickness of the polyurethane foam film,the lower the average stabilized temperature of the outer surface will be;as the thickness of the film increases,the time required for the temperature field of the polyurethane cavity to stabilize is longer.For the polyurethane foam with small pore size or large film thickness,it is difficult to melt the polyurethane foam and the opening degree of polyurethane foam film is relatively small.