Theoretical Model And Experimental Study On Transient Heat Transfer Test Of Non-metallic Heat Transfer Structures

With the increasingly prominent energy problems,non-metallic heat exchangers have outstanding advantages such as corrosion resistance,high strength and light weight.They have become one of the most promising new heat exchange equipment in aerospace,marine ships,petrochemical industry,fuel cells,electronics and electrical appliances and other engineering fields.For industries requiring fast temperature response and high heat transfer efficiency,such as electronic appliances and manned aerospace,due to the low thermal conductivity of non-metallic materials and the neglect of the influence of transverse thermal conductivity and thermal resistance in the calculation,the existing mathematical models cannot be accurately used for the heat transfer analysis of non-metallic heat exchangers,which will directly affect the design and application of heat exchangers.Therefore,it is urgent to put forward the mathematical model and test method of transient heat transfer test method suitable for non-metallic heat transfer structures,so as to provide a wide range of application and high accuracy experimental test method of heat transfer performance for this kind of nonmetallic compact heat exchanger.In view of the above problems,this paper has carried out theoretical derivation and Experimental Research on the heat transfer problems in the transient heat transfer test technology based on non-metallic heat transfer structures.The main research work and conclusions are as follows:1)Based on the assumption of fluid flow and heat transfer in the infinite plates,the mathematical model and boundary conditions of the non-metallic heat exchanger in the transient heat transfer test process are established according to the energy conservation equation,the equations are dimensionless,and the analytical solution is derived by Laplace transform;The mathematical model that ignores the influence of transverse heat conduction degenerates into the model proposed by previous literature.The accuracy of the mathematical model proposed in this paper is verified by comparing the numerical inverse transformation results with the previous Laplace Inverse Transformation results;2)By studying the theoretical solution of the heat transfer model of the non-metallic plate during the transient heat transfer test,studied on the influence of various parameters of non-metallic heat exchanger plates on the experimental results during the transient heat transfer test.The effects of the transverse heat conduction thermal resistance,the number of transfer units NTU and the dimensionless parameter B on the dimensionless outlet temperature of the fluid flowing through the non-metallic large plates are analyzed.The effects of the temperature measurement error on the number of transfer units NTU are studied through the error amplification factor E,which provides a method guidance for the heat transfer test analysis and engineering application of non-metallic compact heat exchangers;3)The basic principle of the single blow test technology is briefly described.By analyzing the limitations of traditional models and test methods,a test method suitable for heat exchangers with transverse heat conduction resistance is proposed,and the corresponding program is embedded in the data processing system so that a new test method for non-metallic plate heat exchangers is successfully supplemented.Based on the above test methods,the test steps suitable for this experiment are proposed;4)Based on the mathematical model and test method of transient heat transfer test technology applied to non-metallic materials,the heat transfer and pressure drop characteristics of four kinds of non-metallic plates with different structural parameters are experimentally studied,and compared with the theoretical calculation values proposed by predecessors,the correctness and feasibility of the test method are confirmed.At the same time,the correlations of the heat transfer and pressure drop characteristics of the non-metallic heat exchange structures are established and compared with the traditional treatment results without considering the transverse heat conduction resistance.The variation of heat transfer coefficient j and friction coefficient f with the structural parameter wave height pitch ratio h0/P is studied,which provides a method basis for the accurate design of the non-metallic corrugated plate heat exchangers.