Numerical and Experimental Study of Heat Transfer Performance of Braking Resistor for Train
|School||Lanzhou Jiaotong University|
|Course||Thermal Power Engineering|
|Keywords||Braking resistor band Flow and heat transfer Experimental study|
To ensure the safe operation of high-speed train, braking quipment played a veryimportant role during running. During braking process, the kinetic energy of train istransferred into other forms of energy storage or consumption. Among them, the resistorbraking converts the kinetic energy into electrical energy; electrical energy is converted intoheat energy which distributed into the atmosphere. With the speed of the train becominghigher, the heat load of the braking resistance increases, higher request of heat dispersion ofbraking resistance has to be put forward. In order to ensure braking resistances work stablywith higher heat transfer efficiency, reliable and economical solution to the cooling problemin the high-temperature part of break resistances was urgent needed. The working medium ofbraking resistors was air, so the study about flow and heat transfer performance of air in thechannel of braking resistor with high wall temperature was essential.Based on the practical application of the brake resistors, the cooling solution wasdetermined, and the physical model of the braking resistors was also built. The test-bed forstudying heat transfer performance of train braking resistors was built according to designscheme. To several different structures, for example, lamellar spacing was14mm,15mmand16mm, the tests about the thermal performance of braking resisto was under the sameheating power and different wind conditions were conducted, and the parameters underdifferent conditions were obtained. According to the data of the experiments, the thermalcooling characteristics of three structures were compared. The heat transfer law of the brakingresistors was studied, the parameters of heat transfer and the friction factor that generatedwhen fluid flows through the braking resistors were calculated. So, the mathematical model tocalculate the heat transfer coefficient h and friction factor f was given. This study canprovide the corresponding theoretical basis and experimental data conclusions for improvingthe structure of the braking resistance band.The major results of the study are:1. The regularities of the the heat transfer coefficient h and friction factor f is calculated:with the attack angle, the same length and the same distance between the fins, the heattransfer coefficient h increases with the increase of Re, the resistance coefficient f decreaseswith increase of Re; with the attack angle, the same length and the same Re but the differentdistances between the fins, the heat transfer coefficient h and friction factor f increase whenthe distance increases.2. the heat transfer coefficient h increased with the increase of Re, that is to say, heat transfer performance was enhanced as the increase of Re number, the maximum heat transfercoefficient was26.30W/(m~2K);3. The resistance coefficient f decreased with increase of Re.It’s the smallest when thedistance is16mm;4. The local heat transfer coefficient of braking resistor is analyzed. According to theresearch, surface heat transfer coefficient is higher and heat transfer performance is betterwhen an attack angel exits;5. Compared with the numerical results, the regularities of the the heatransfer coefficienth and friction factor f are basically the same.