Investigation Of Heat Pipe Charge Air Cooler And The Application Of Heat Pipe Charge Air Cooler In The Vehicle Cooling System

With increasingly stringent emissions regulations and increasing degree of engine enhancement, the requirement of compression ratio becomes much higher and the compression ratio of turbocharger compressor can achieve higher and higher. Furthermore, exhaust gas recirculation (EGR) technology is adopted, hence the charge air temperature becomes even higher, promoting a substantial increase of the heat exchanger thermal stress. In addition, the vehicle underhood space is increasingly crowded, the air flow is limited and the heat exchanger cannot reject heat timely. Tensile strength of aluminum begins to aggravate above the temperature of more than140· and deteriorate seriously above2009℃. Therefore, high stress operating time of turbo is a challenge to the mechanical and fatigue resistance properties and thermal performance of the current word wide aluminum charge air cooler. In some cases, it has reached the inherent material performance limitations of aluminum at high temperatures. In view of the technical features of heat pipe, such as highly efficient heat transfer characteristics and high heat flux, a kind of heat pipe heat exchanger is designed for the cooling system of the commercial vehicle in this research. Then the application feasibility of heat pipe charge air cooler in the vehicle cooling system is conducted. The heat transfer and pressure drop performance of heat pipe charge air cooler and the optimization design of heat pipe charge air cooler are studied by theoretical analysis, numerical simulation and experimental research. Meanwhile the matching optimization of the heat pipe heat exchanger and front cooling module is investigated. Under the premise of meeting the cooling requirements of the truck, the structure of the aluminum charge air cooler is improved and finally a new compact and efficient cooling system module is developed. The main contents of this paper include:1. Considering the requirements of heat transfer performance for the charge air cooler and vehicle underhood space limitation, a heat pipe heat exchanger is designed and the influence of tube pitch, condenser length, number of pipes, inlet and outlet conditions of cooling and hot air on the heat transfer and pressure drop characteristics of the heat pipe charge air cooler are investigated using the logarithmic mean temperature difference method and ε-NTU (effectiveness-number of heat transfer units) method.2. For the heat pipe charge air cooler, a single heat exchanger unit model and an overall heat exchanger model are established and simulated using the CFD (Computational Fluid Dynamics) method. Finally, the effects of the structural parameters of heat exchanger and the inlet conditions of cooling and hot air on the flowing and heat transfer characteristics of the heat pipe charge air cooler are analyzed according to the field synergy theory.3. Heat transfer performance and resistance performance prediction model of heat pipe intercooler are established based on a small amount of test data. Then the heat transfer performance and resistance performance of the heat pipe charge air cooler are predicted by means of the BP neural network method, the prediction results-are compared with the experimental results and it is found that the prediction results are in good agreement with the experimental results. For the heat transfer performance network model, the maximum relative error is8.0%and the average relative error is3.5%; For the resistance performance network model, the maximum relative error is13.1%and the average relative error is5.1%, which means that the prediction model can predict the thermal performance of the heat pipe charge air cooler well and can be used for engineering design combining with experimental method. Finally, the structural parameters are optimized by the BP neural network model and the optimal design parameters are obtained.4. The heat transfer and pressure drop characteristics of the heat pipe charge air cooler are investigated in a small wind tunnel A. The influence of cooling air velocity, inlet temperature of hot air, mass flow of hot air, tube pitch, condenser length, pipe line on the flowing and heat transfer characteristics of the heat pipe heat exchanger are discussed. Then, the experimental results are compared to the theoretical results. Meanwhile, the outlet temperature field of cooling air and the temperature distribution of hot air channel are discussed by means of experiments and CFD simulations. Finally, by multi-parameter linear regression analysis of a large number of experimental results, the correlations of Nu and Eu are obtained.5. The flowing and heat transfer characteristics of the package of a heat pipe charge air cooler and front cooling module are studied by CFD simulation and experimental research in the wind tunnel B. Then, two kinds of optimization of the intercooler are done to improve the performance. The results show that the airflow uniformity index and the pressure drop are improved efficiently; the heat pipe intercooler could well reduce the inlet temperature of the aluminum intercooler, while the optimized intercooler can satisfy the cooling requirements well, and thereby the aluminum intercooler has further room for improvement. On this basis, compared to the original, the heat rejection of radiator has a larger enhancement between3.36%-13.08%. Thus the cooling module can be optimized to be more compact to meet the cooling requirements, which is very significant to the optimization of the front-end cooling module and improvement of the overall heat transfer.