Experimental And Numerical Studies Of Heat Transfer Characteristics Of The Layer Combined With Aluminum Extrusion And Multi Insulation Material Layers

With the rapid development of high-speed trains, people have more and morerequirements to the railway passengers that not only the safety and high speed operation isguaranteed, but also the healthy and comfortable travel environment is provided. Therefore, itis very important to maintain a constant temperature in the passenger compartment, and theinsulating properties have a great influence to the air conditioning load. The heat transfercharacteristics of the car body assembles of high-speed trains are important to determine theheat duty exchanged between the inner and outside environments, which include the heattransfer of the aluminum extrusions which makes up the body structure, the heat conductionof the insulation materials and decoration materials. For facility engineering application, theseheat transfer characteristics are included in a parameter named the equivalent thermalconductivity of car body assembles. The smaller its value is the less energy lost through thecar body assembles. To provide design reference for the car body optimization design anddetermine the air conditioning load of high-speed trains, heat transfer characteristics in amodel of the car body assembles, a combined layer with aluminum extrude and multiinsulating layers is studied with experimental and numerical methods in this paper.The role of natural convection in the aluminum extrusion is experimentally studied bychanging the position of the hot wall related to the direction of the gravity and the temperaturedifference between two wall surfaces; and numerical study is carried out to solve a complexcoupled heat transfer process-natural convection in the cavity, the radiation heat transfer ofinner surfaces and heat conduction of solid materials with uniform heat flux as the boundarycondition of the hot wall. Equivalent thermal conductivity of car body assembles is obtainedthrough analysis their heat transfer characteristics.The results indicate that the equivalent thermal conductivity of the combined layer doesnot depend on the temperature difference and the position of the hot wall related to thedirection of the gravity, and the roles of the natural convection and the radiation heat transferin the aluminum extrusion are very weak; the temperature of the wall and the fin is uniformbecause of the metal fins along the heat transfer direction transports most amount of heat, theradiation heat transfer between the walls forming the hollow metal wall is very weak.