3D Heat Conductivity Model of Mold Based on Node Temperature Inheritance

A novel 3D conductive heat transfer model was developed based on node temperature inheritance. Heat transfer of the mold and billet could be analyzed synchronously. In the model, heat transfer in the copper wall was in a steady state, whereas heat transfer in the billet was in a transient state. The temperature distribution indicated that the maximum temperature on the copper wall reached approximately 30 mm below the meniscus. The results were in better agreement with industrially measured data than those of traditional 2D heat transfer models. The model was applied to study the effect of water scale on heat transfer of a billet mold. When the scale thickness increased from 0 to 0.5 mm, the maximum temperature on the copper wall increased from 174 °C to 364 °C, which will lead to mold deformation and peeling of the coating. In addition, the shell thickness slightly decreased with increasing scale thickness.

Corrosion rate determination of vessel walls agitated by double impeller and gas sparging

Recently, multiple impeller gas sparged vessels have found wide application in many industries, such as food, pharmaceuticals, and biofuels. In this study, the rate of diffusion-controlled corrosion of the wall of nitrogen gas sparged-double impeller agitated vessel was studied by the dissolution of copper wall in acidified dichromate solution technique. The variables studied were the impeller rotation speed, the superficial gas velocity, and the clearance between the two impellers. The results were reported in terms of dimensionless number depicting the process conditions, Re, Sc, and the impeller clearance. For the agitated vessel, the corrosion rate correlation was ${\rm{CR}} = 1.6\; \times \;{10^{\; - \;16}}{\rm{R}}{{\rm{e}}_{{\rm{Ag}}{\rm{.}}}}^{0.668}{\left( {{{{C_2}} \over H}} \right)^{0.183}}{\rm{S}}{{\rm{c}}^{0.33}}.$ For the condition: 2800<ReAg.<19,600, 0.19<C2/H<0.58 and Sc=960, with an average deviation of ±2.9%. For the agitated sparged vessel, the data were correlated by ${\rm{CR}} = 2.5\; \times \;{10^{\; - \;15}}{\rm{R}}{{\rm{e}}_{{\rm{Ag}}{\rm{.}}}}^{0.134}{\rm{Re}}_{{\rm{Sp}}{\rm{.}}}^{{\rm{0}}{\rm{.381}}}{\rm{S}}{{\rm{c}}^{0.33}}.$ For the condition: 2800<ReAg.<19,600, 370<ReSp.<1855 and Sc=960, with an average deviation of ±6.7%. These results show that, under these conditions, the rate of corrosion of agitated vessels is controlled by the rate of agitation and the clearance between the impellers. However, when gas sparging is introduced, the rate of corrosion is much more influenced by the gas flow rate, whereas the effect of the clearance between the impellers nearly disappears.

The Role of Liquid Fuels Channel Configuration on the Combustion inside Cylindrical Mesoscale Combustor

This research intended to investigate combustion of liquid fuel in 3.5 mm inner diameter quartz glass tube mesocombustor, based on liquid film evaporation by using heat recirculation. The mesocombustor has a copper section for heating and evaporating the liquid fuel. In mesocombustor type A, the fuel was glided through the narrow canal in the copper wall while the air was glided through the axial of combustor. The flame could only be successfully stabilized in high-ratio equivalent ranging from ɸ =1.1 to ɸ=1.6, due to the gap without combustion reaction caused by high air-fuel mixture over the limits of flame stability. Mesocombustor type B, which has annulus-shaped canal, could shift the flame stability from ɸ =0.8 to ɸ =1.2; however, it also narrowed the limits of flame stability due to the wall cooling. In mesocombustor type C, both liquid fuel and air were glided through the annulus-shaped canal in the copper wall to fix the fuel evaporation and air mixture. The flame of type C was successfully stabilized, from ɸ =0.73 to ɸ =1.48 wider than types A and B. The flame of type C mesocombustor is circle-shaped and fitted to cross section of mesocombustor, but it still has thin gap without any flames due to thermal quenching by the wall.

Molecule Dynamics Simulation of Heat Transfer Between Argon Flow and Parallel Copper Plates

Molecular dynamics (MD) simulation aiming to investigate heat transfer between argon fluid flow and two parallel copper plates in the nanoscale is carried out by simultaneously control momentum and temperature of the simulation box. The top copper wall is kept at a constant velocity by adding an external force according to the velocity difference between on-the-fly and desired velocities. At the same time the top wall holds a higher temperature while the bottom wall is considered as physically stationary and has a lower temperature. A sample region is used in order to measure the heat flux flowing across the simulation box, and thus the heat transfer coefficient between the fluid and wall can be estimated through its definition. It is found that the heat transfer coefficient between argon fluid flow and copper plate in this scenario is lower but still in the same order magnitude in comparison with the one predicted based on the hypothesis in other reported work.

Optimization of Natural Air Cooling in a Vertical Channel of Electronic Equipment

The natural convection cooling capability in a compact item of electronic equipment was investigated quantitatively by experiment and numerical simulation with a simple channel model. The optimization of the channel sizes, especially the clearance between heated walls, was discussed. The channel model, which consists of a vertical duct of rectangular section, was applied as the experimental model of electronic equipment in this study. The channel model consists of two heated copper walls and two transparent acrylic walls. The clearance between the copper walls of the channel was varied from 5 mm to 15 mm. Temperature measurement on the copper wall surfaces and velocity measurement of natural air flow in the channel by using a particle image velocimetry (PIV) were conducted for a few clearances of the channel. Numerical simulation was also carried out, with a model following the experimental setup, for more detailed discussion of various clearances of the channel. The relationship between the clearance and the temperature rise of the walls or velocity profile was investigated. The correlation between the Rayleigh number and the Nusselt number was obtained from measured temperature. The natural cooling capability and the velocity profiles depend on the clearance between the copper walls. When the wall clearances are more than 15 mm, the cooling is not enhanced. On the other hand, in the case that the clearance becomes less than 7 mm, the cooling capability becomes significantly lower. Consequently, it is clarified that the clearance from 8 mm to 10 mm is the best size for natural cooling from the view point of the space and the capability.

Optimization of Natural Air Cooling in a Vertical Channel of Electronic Equipment

The natural convection cooling capability in a compact item of electronic equipment was investigated quantitatively by experiment and numerical simulation with a simple channel model. The optimization of the channel sizes, especially the clearance between heated walls, was discussed. The channel model, which consists of a vertical duct of rectangular section, was applied as the experimental model of electronic equipment in this study. The channel model consists of two heated copper walls and two transparent acrylic walls. The clearance between the copper walls of the channel was varied from 5 mm to 15 mm. Temperature measurement on the copper wall surfaces and velocity measurement of natural air flow in the channel by using a particle image velocimetry (PIV) were conducted for a few clearances of the channel. Numerical simulation was also carried out, with a model following the experimental setup, for more detailed discussion of various clearances of the channel. The relationship between the clearance and the temperature rise of the walls or velocity profile was investigated. The correlation between the Rayleigh number and the Nusselt number was obtained from measured temperature. The natural cooling capability and the velocity profiles depend on the clearance between the copper walls. When the wall clearances are more than 15 mm, the cooling is not enhanced. On the other hand, in the case that the clearance becomes less than 7 mm, the cooling capability becomes significantly lower. Consequently, it is clarified that the clearance from 8 mm to 10 mm is the best size for natural cooling from the view point of the space and the capability.