Advanced Materials Research Vols. 199-200

Abstract: Mathematical programming model for synthesis of heat exchanger network for distillation unit is established. MINLP problem for heat exchanger network is solved by branch-bound method. Two kinds of heat exchanger network with splitting stream and without splitting stream are obtained. 142 heat exchangers, 8 coolers and 4 heaters are needed in the heat exchanger network without splitting stream. 34 heat exchangers, 8 coolers, 4 heaters, 11 splitters and 11 mixers are needed in the heat exchanger network with splitting stream. The matching situation including heat load, heat exchange area, duty of utilities, flow fraction of splitting, temperature of inlet and outlet, etc. for cold and hot streams in the heat exchanger network with splitting stream is presented in detail, Analysis the relationship between total heat exchange area, total heat load, total capital cost and annual operation cost of the heat exchanger network. Taking the number of heat exchangers and operational flexibility of heat exchange network into consideration, the heat exchanger network with splitting stream is suggested to be selected.

Abstract: Pin fins are widely applied in heat exchanger industry. The heat transfer characteristics of pin fins can be found in many textbooks and handbooks related to heat transfer or heat exchanger. However, most heat transfer experts recognized from their own experiences that the heat radiation effect equation contained the fourth order exponential of temperature and the emissivity of oxidized metal are higher, the inaccuracy of heat transfer rate might be higher while ignoring the effect of heat radiation. In this study, numerical simulation using computational fluid dynamics (CFD) code was conducted to verify the heat transfer characteristics of pin fins. It is found that the error of heat transfer rate generated by ignoring heat radiation will be as high as 45 % while heat convection coefficient is 10 (Wm^-2K^-1 ) associated with the emissivity of fin surface is 1.0. It also revealed the heat radiation effect cannot be neglected for pin fins, especially for the application under high emissivity and low heat convection coefficient conditions.

Abstract: The performance of brushless permanent magnet motor for electric vehicle applications is simulated by commercial CFD codes Fluent 6.3. It is difficult to model motor winding area and to well pose the motor external boundary conditions for using CFD method. A possible approach to simplify the thermal resistance computation is to use an empirical equivalent thermal conductivity of the system winding impregnation and insulation. The empirical equivalent thermal conductivity is case sensitive and regressed in the experiment. The same is true for the boundary condition of motor. In this paper, we proposed a new model to compute equivalent thermal conductivity and overcome the above problem. This model takes advantage of the packing bed heat transfer model proposed by Zehner and Schlünder. Besides, the boundary conditions are also obtained by the numerical experiments. The validity of CFD method using in the present paper is validated utilizing the experimental data. The numerical data are concurred with the experimental data. As a result, the CFD method is shown to be a feasible method for modern thermal design for brushless permanent magnet motor.

Abstract: LASH or large-and-small-hole baffle is a new kind of baffle which induces axial flow in the shell-side of heat exchangers. In this paper, pressure drop and heat transfer of heat exchangers with LASH baffles were experimentally studied and compared with those in common heat exchangers with segmental baffle. It is founded that compared with the segmental baffles, pressure drops caused by LASH baffles are greatly decreased. Although the shell-side heat transfer coefficient with the LASH baffles is decreased, more comprehensive performance for heat exchangers with LASH baffles can be achieved.

Abstract: After heat treatment, the surface hardness and effective depth of hardened layers of automotive transmission countershaft, determines the quality of the part itself as well as the normal and reliable operation of the transmission assembly. The paper analyzes the specific reasons for such problems as soft zone on the hardened surface of transmission countershaft when proceeding with carbonitriding in the controlled atmosphere furnace, a multi-purpose furnace. And with process parameters adjusted, the process parameters of heat treatment are corrected that the soft zone has been eliminated and the quality of parts has been effectively controlled.

Abstract: The storage cells of conventional submarines are usually charged up by in the snorkeling state, when the diesel engines that charge the storage cells work underwater. The reverse flow of sea water into the diesel engine from the exhaust pipelines can be avoided effectively by using a water-collecting box (WCB), which has other functions as well. In this paper, a three-dimensional model of WCB was established and based on which the flow and temperature fields were studied by computational fluid dynamics (CFD) computations. From the comparison of distribution on interior fields for four different structural WCBs, an optimized scheme of enhancing the cooling effect and not raising the exhausting resistance was probed. The results show that the temperature drop of exhaust gas after washing the WCB IV (WCB with truncated tubes) is 40 percent higher than that of the WCB I, and the pressure drop has a low of 3 percent as well. The comprehensive characteristics of WCB IV are foremost between the four WCBs.

Abstract: In the thermal design of embedded high-power chips microwave modules, structural parameter is one of the main reasons affect the thermal resistance, thus influences the reliability of the modules, the structural parameter optimized of the microwave components was studied in this paper. The goal of this work is to decrease the temperature and achieves the best structural dimensions. Using the ANSYS software build the EPCM module, through simulation analysis, Linear regression equation be fitted by RSM, which concerning the module maximum temperature with board area, substrate thickness, molybdenum thickness and encapsulation thickness. Based on genetic algorithms, structural parameter optimization algorithm of thermal model was proposed and the optimization structural parameter of embedded high-power chips microwave modules was achieved by corresponding optimization program. Based on ANSYS work, before optimization the model of maximum temperature is 86.717°C, the maximum temperature module of the optimization structural parameter is lower 1.28°C than before, so the thermal resistance decreased. The result show that the maximum temperature module of the optimization structural parameter is in good accord with the FEA results. It turns out that the RSM –GA approach proposed in this work can be effective and robust in providing structural parameter optimization in EPCM.

Abstract: In modern machine tool design, it is an important precondition of precision control to forecast accurately the relation between the final output precision of machine tool and its error cell. In this paper, the error cell characteristic of machine tool is described as the change of value and direction during the source error transfer. By supposing the source error of error cell as unit error, and forecasting their action effect, the characteristic of every error cell can be contained and compared. An example is provided lastly.

Abstract: To research the relationship between the coolant heat power and engine working conditions, and to guide the reasonable design of all heat-radiating components, an experiment method of heat balance at all operating modes was developed and implemented for a certain type of small gasoline engine. Based on the multivariate regression analysis, the correlation between the coolant thermal power and the engine rotation speed and torque was obtained. Tested by the experimental results and significant approach, the multivariate regression equations established have a high precision, and a certain theoretical and practical value for the cooling system analysis and design for small gasoline engine.

Abstract: Thermal design, finite element analysis of a satellite borne PCB is introduced in this paper. Some methods were adopted to help heat conduct and a simplified computing model was built. The analysis results show that the temperature scope of the main structure is from 45.5°C to 72.3°C in high temperature work case and all of junction temperatures of components are lower than the derated maximum junction temperatures themselves and leave enough design margins, which match the requirements of thermal analysis.