Kuniyasu Kanemaru

Heat transfer correlation of film boiling from a downward‐facing horizontal circular plate

Correlation equations for saturated and subcooled film boiling heat transfer from a downward-facing horizontal circular plate are proposed based on a theoretical study using an integral method. For the case of subcooled liquids, a dimensionless heat transfer parameter is introduced to effectively correlate within ±15% the experimental data obtained under both quenching and steady-state conditions.

Numerical Analysis for Heat and Mass Transfer of Granular Flow in a Duct by the Discrete Particle Simulation

The solid-gas or liquid-gas two phase flow has many industrial applications such as spray drying, pollution control, transport systems, fluidized beds, energy conversion and propulsion, material processing, and so on. Though the solid-gas multiphase flow has been studied experimentally and numerically, the transport phenomena have not been cleared due to its complexity, computational time and economical costs for the hardware. In this study the heat and mass transfer of solid-gas collision dominated flow is analyzed by the Discrete Particle Simulation (DPS), a kind of the Dispersed Element Method (DEM)[1]. This method describes the discrete phase and the continuous phase by Lagrange and Euler methods respectively, and has been used to simulate the multiphase flow of various geometrical systems. In order to analyze the thermal field we took account of the energy equation and heat conduction between colliding particles. The heat transfer rate is summation of conductive heat transfer and convective heat transfer. Furthermore, the fluid flow has a two dimensional velocity profile, because the void fractions are analyzed as two dimensions. But momentum space has not been resolved by the two dimensional simulation. We call this method, the quasi two-dimensional simulation in this paper. To obtain the temperature distribution of the continuous phase the energy equation is solved in addition to the momentum equations. We treated the interaction between continuous and discrete phases as one and two way couplings. The positions, the momentum and the temperature information of particles and the velocity and the temperature distribution of the fluid were obtained as functions of time from results of these numerical simulations. When the hot air that is suspending small glass particles flows in a duct from bottom up, we traced the particles and got the temperature distribution of fluid and compared with the former results of one-dimensional flow. At the beginning, the cooler particles decrease the fluid temperature near the bottom of the vessel. The temperature profile of the particles obtained by the one-dimensional simulation is as same as quasi two-dimensional simulation. After 0.5 second the particles cool the downstream air. At 1.2 second, particles do not decrease the air temperature because the temperatures of particles are close to the inlet temperature of the air.© 2009 ASME

Film Boiling Around a Vertical Cylinder With Top and Bottom Horizontal Surfaces

Saturated and subcooled film boiling heat transfer around a vertical finite-length silver cylinder with top and bottom horizontal surfaces has been investigated, experimentally and analytically, in terms of cooling curve, and the correlations of heat transfer were proposed in the present paper. Pool film boiling experiments were carried out by quenching method. Cooling curves are obtained for saturated water at atmospheric pressure. The heated cylinder is made of silver and 18 kinds of cylinder are tested in the ranges of the diameter from 8 to 100 mm and the length from 8 to 160 mm. For subcooled water, the experiments were carried out in the similar method to the case of saturated water. The ranges of the diameter and length of the cylinder are 32 to 50 mm and 16 to 64 mm, respectively. The degree of liquid subcooling ranges from 2 to 30 K. In order to predict the film boiling characteristics, the overall heat transfer rate from a cylinder with finite length was modelled by taking into account each convective heat transfer on the bottom, side and top surfaces of the vertical cylinder. Present correlation equations for heat transfer and the lower limit of film boiling are good agreement with the experimental data for saturated and subcooled water. The values of wall heat flux and temperature at the lower limit of film boiling are obtained as the point where the cooling rate has a minimum value on the cooling curve. For the case of saturated water, wall temperature at the lower limit of film boiling is about 136 K and irrespective of the configuration of a cylinder. For subcooled water, the correlation is proposed for the effect of liquid subcooling on wall temperature at the lower limit of film boiling.Copyright

Numerical Analysis of Heat and Mass Transfer on Collision Dominated Particles Flow in a Vessel

Though the solid-gas multiphase flow has been studied experimentally and numerically, the transport phenomena have not been cleared due to its complexity, computational time required and economical costs for hardwares. In this study the heat and mass transfer of solid-gas collision dominated flow in a rectangular vessel is analyzed by the Discrete Particle Simulation (DPS), a kind of the Dispersed Element Methods (DEM)[1]. This method describes the discrete phase and continuous phase by the Lagrange and the Euler methods respectively, and has been used to simulate the multiphase flows of various geometrical systems. In order to analyze the thermal field we took account of the energy equation and heat conduction between colliding particles. We treated the continuous phase as a pseudo two dimensional flow, and the interaction between continuous and discrete phases as two way coupling. The positions, the momenta and the temperature information of particles and velocity and temperature distribution of fluid were obtained as functions of time from results of these numerical simulations. When the hot air flowed from bottom to top in the vessel of packed bed, we traced the particles and got the temperature distribution of fluid. The particles at the surface of the packed bed jumped first and made the void areas at the middle of vessel. We found the void areas that rise in the dispersed particles.Copyright