Three-Dimensional Surface Heat Transfer Coefficient and Thermal Stress Analysis for Ceramics Tube Dipping into Molten Metal

2010 ◽  
Vol 452-453 ◽  
pp. 233-236 ◽  
Author(s):  
Yasushi Takase ◽  
Wen Bin Li ◽  
Hendra ◽  
Hiroki Ogura ◽  
Yusuke Higashi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Stress ◽  
Transfer Coefficient ◽  
Molten Metal ◽  
Thermal Stresses ◽  
Three Dimensional ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Surface Heat Transfer Coefficient

The low pressure die casting machine has been used in industries because of its low-cost and high efficiency precision forming technique. In the low pressure die casting process is that the permanent die and filling systems are placed over the furnace containing the molten alloy. The filling of the cavity is obtained by forcing the molten metal, by means of a pressurized gas, to rise into a ceramic tube, which connects the die to the furnace. The ceramics tube, called stalk, has high temperature resistance and high corrosion resistance. However, attention should be paid to the thermal stress when the ceramics tube is dipped into the molten metal. It is important to reduce the risk of fracture that may happen due to the thermal stresses. To calculate the thermal stress, it is necessary to know the surface heat transfer coefficient when the ceramics tube dips into the molten metal. In this paper, therefore, the three-dimensional thermo-fluid analysis is performed to calculate surface heat transfer coefficient correctly. The finite element method is applied to calculate the thermal stresses when the tube is dipped into the crucible with varying dipping speeds and dipping directions. It is found that the thermal stress can be reduced by dipping slowly when the tube is dipped into the molten metal.

Comparison of Surface Heat-Transfer Coefficient of GCr15 Steel Quenched by Clear Water and Nitrogen-Spray Water

2013 ◽  
Vol 444-445 ◽  
pp. 1290-1294
Author(s):  
Li Jun Hou ◽  
He Ming Cheng ◽  
Jian Yun Li ◽  
Bao Dong Shao ◽  
Jie Hou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Thermal Stresses ◽  
Surface Heat ◽  
Water Quenching ◽  
Surface Heat Transfer ◽  
Surface Heat Transfer Coefficient ◽  
The Heat Transfer Coefficient

In order to simulate the thermal stresses, thermal strains and residual stresses of steel during quenching by numerical means, it is necessary to obtain an accurate boundary condition of temperature field. The explicit finite difference method, nonlinear estimate method and the experimental relation between temperature and time during water and nitrogen-spray water quenching have been used to solve the inverse problem of heat conduction. The relations between surface heat-transfer coefficient in water and nitrogen-spray water quenching and surface temperature of cylinder have been given. In numerical calculation, the thermal physical properties of material were treated as the function of temperature. The results show that the relations between surface heat-transfer coefficient and surface temperature are non-linear during water and nitrogen-spray water quenching, the heat-transfer coefficient is bigger when water quenching than when nitrogen-spray water before 580°C, the heat-transfer coefficient is smaller when water quenching than when nitrogen-spray water after 400°C. The results of calculation coincided with the results of experiment. This method can effectively determine the surface heat-transfer coefficient during water and nitrogen-spray water quenching.

The Use of Electrical Models in Cooling Studies of Electrical Machines

1969 ◽  
Vol 184 (9) ◽  
pp. 15-22 ◽  
Author(s):  
J. R. Simonson
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Three Dimensional ◽  
Surface Heat ◽  
Traction Motor ◽  
Surface Heat Transfer ◽  
Axial Temperature ◽  
Electrical Analogy ◽  
Surface Heat Transfer Coefficient

The electrical analogy of heat transfer is a well-established experimental approach to complex heat transfer problems. In this paper the theory of the analogy is summarized and the results of applying the analogy to cooling studies of traction motor armatures are discussed. Electrical models, simulating two- and three-dimensional heat flow in 375-kW traction motor armatures were constructed, and temperatures in the armature conductors, core, and teeth were predicted for varying speed conditions. An axially varying surface heat transfer coefficient was found to give considerable axial temperature variation, due to the low thermal conductivity of the armature core in that direction. Values of surface heat transfer coefficient were obtained which gave predicted temperatures in agreement with measurement. The effects of increasing the axial cooling duct area were investigated.

The Research on the Key Factor Affect the Precision in Stress Analysis for the Rotor of Steam Turbine

2013 ◽  
Vol 275-277 ◽  
pp. 83-86
Author(s):  
Chun Lin Zhang ◽  
Nian Su Hu ◽  
Wen Yang ◽  
Jian Mei Wang ◽  
Min Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Numerical Calculation ◽  
Transfer Coefficient ◽  
Stress Analysis ◽  
Surface Heat ◽  
Flow State ◽  
Surface Heat Transfer ◽  
Surface Heat Transfer Coefficient ◽  
Key Factor

With the development of the power grid, the proportion of large capacity unit is increasing rapidly. It requires a more in-depth study on the reliability of the unit, especially for the unit adjusting the peak. This paper concerned on the research of the surface heat transfer coefficient, which is the key factor affect the precision in thermal stress analysis. The surface heat transfer coefficient is obtained via the numerical calculation for the steam’s flow state and the transient heat transfer between rotor. This paper mainly describes the steam’s flow state and the transient heat transfer with the steam seal, and the results show that the direct numerical calculation is resultful in this subject.

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