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In this study, CFD analysis of air-heating vaporizers was conducted. A longitudinally finned vertical pipe was used to represent the air-heating vaporizer in the CFD model. Nitrogen gas was used as the working fluid inside the vertical pipe, and it was made to flow upward. Ambient air, which was the heat source, was assumed to contain no water vapor. To validate the CFD results, the convective heat transfer coefficients inside the pipe, hi-c, derived from the CFD results were first compared with the heat transfer coefficients inside the pipe, hi-p, which were derived from the Perkins correlation. Second, the convection heat transfer coefficients outside the pipe, ho-c, derived from the CFD results were compared with the convection heat transfer coefficients, ho-a, which were derived from an analytical solution of the energy equation. Third, the CFD results of both the ambient-air flow pattern and temperature were observed to determine whether they were their reasonability. It was found that all validations showed good results. Subsequently, the heat transfer coefficients for natural convection outside the pipe, ho-c, were used to determine the Nusselt number outside the pipe, Nuo.. This was then correlated with the Rayleigh number, Ra. The results show that Ra and Nuo have a proportional relationship in the range of 2.7414×1012 ≤ Ra ≤ 2.8263×1013. Based on this result, a relation for the Nusselt number outside the pipe, Nuo, was proposed. [ABSTRACT FROM AUTHOR]

To control a heat source easily in the forming process of steel plate with heating, the electro-magnetic induction process has been used as a substitute of the flame heating process. However, only few studies have analyzed the deformation of a workpiece in the induction heating process by using a mathematical model. This is mainly due to the difficulty of modeling the heat flux from the inductor traveling on the conductive plate during the induction process. In this study, the heat flux distribution over a steel plate during the induction process is first analyzed by a numerical method with the assumption that the process is in a quasi-stationary state around the inductor and also that the heat flux itself greatly depends on the temperature of the workpiece. With the heat flux, heat flow and thermo-mechanical analyses on the plate to obtain deformations during the heating process are then performed with a commercial FEM program for 34 combinations of heating parameters. An artificial neural network is proposed to build a simplified relationship between deformations and heating parameters that can be easily utilized to predict deformations of steel plate with a wide range of heating parameters in the heating process. After its architecture is optimized, the artificial neural network is trained with the deformations obtained from the FEM analyses as outputs and the related heating parameters as inputs. The predicted outputs from the neural network are compared with those of the experiments and the numerical results. They are in good agreement. [ABSTRACT FROM AUTHOR]

The general cooling tower is a device for cooling water in industrial condensers or heat exchangers. The present cooling towers have defects with noises, complicated structures and environmental problems. This paper focuses on a new water cooling system using the latent heat of evaporation in an enclosed vacuum tank and a water driven ejector system. Several experiments were carried out to improve high vacuum pressure and water cooling characteristics. The ejector performance was tested with various water temperatures. Based on the vacuum pressure of the water driven ejector, the water cooling characteristics were investigated for the condensed and vaporized air and the effect of increased evaporating surface area in an enclosed tank. [ABSTRACT FROM AUTHOR]

The aquaculture tank is used for breeding fish in sea water which was pumped up to land. The flow characteristics in the aquaculture were investigated with varying the tank geometry and flow rate. The numerical analysis has been employed for calculating the velocity and temperature distributions in a water tank of rectangular type. The finite volume method and SIMPLE algorithm with 3-dimensional standard k-ε turbulence model were used for the numerical analysis. For comparison with experimental results, the PIV system was applied to visualize the flow patterns quantitatively. The numerical results showed good agreements with the experimental results. The mean velocity and temperature versus aquarium depth were represented for various circulating flow rates. Especially, the aquaculture environment is recommended that the aquarium depth has to be d=0.5 m, and this case is the condition of higher velocity and temperature in winter season. [ABSTRACT FROM AUTHOR]