Eisyun Takegoshi

Measurement of thermal properties of iron oxide pellets

The thermal properties of iron oxide pellets of different porosity and prepared by reduction at different rates were investigated in the range of room temperature to about 800°C. The thermal diffusivity a was measured by a laser flash method and the specific heat Cpwas measured by adiabatic scanning calorimetry. The thermal conductivity was calculated from the relation λ=aCρp, where ρ is the density of the specimen.For nonreduced iron oxide pellets, the thermal diffusivity and thermal conductivity decreased with increase in temperature and porosity. The specific heat increased with increasing temperature and there was a transformation point at which the specific heat reached a maximum. In prereduced iron oxide pellets, the thermal diffusivity and thermal conductivity were very small compared with the nonreduced pellets and they gradually increased with increasing temperature. The specific heat had a minimum and a maximum at about 300 and 600°C, respectively, and the scale of these features became smaller with increase in the reduction rate.

Lattice Boltzmann Simulation of Nucleation

We propose a lattice Boltzmann model capable of simulating nucleation. This LBM modifies a pseudo-potential so that it recovers a full set of hydrodynamic equations for two-phase flows based on the van der Waals-Cahn-Hilliard free energy theory through the Chapman-Enskog expansion procedure. Numerical measurements of thermal conductivity and of surface tension agree well with theoretical predictions. Simulations of phase transition, nucleation, pool boiling are carried out. They demonstrate that the model is applicable to two-phase flows with thermal effects. Using finite difference Lattice Boltzmann method ensures numerical stability of the scheme.Copyright

An Experimental Study on the Solidification and Melting of Water around a Vertical Heat Transfer Plate with Pin Fins.

The objectives of the present study were to perform a numerical analysis of the solidification and melting of water around a vertical heat transfer plate with pin fins by means of a finite-difference method under a quasisteady-state assumption. The characteristics of phase change, such as the shape of the solid-liquid interface, the temperature distribution and the liquid velocity, were considered for different numbers of fins, and these analytical results were compared with the experimental results. We found that the heat conduction underwent a considerable increase when the number of fins was large during the solidification, but in the range near the heat transfer plate natural convection between the fins was confirmed for every number during the melting and small-scale natural convection around the pin fins was defected.

An Investigation of the Thermal Conductivity Measurement of a Nonlinear Medium using the Transient Hot Wire Method.

The principle of thermal conductivity measurements as illustrated by the transient hot wire method is based on the assumption that thermal properties of a medium are constant, independent of temperature. However, since the thermal conductivity of the medium usually changes with temperature, the temperature rise during the measurement is a source of error. In this study, the theory of thermal conductivity measurements for such a nonlinear medium using the transient hot wire method is investigated analytically, and is compared with conventional theory for a constant conductivity medium. Furthermore, experiments are performed for a medium with a comparatively large temperature coefficient of thermal conductivity and are compared with the theory for the nonlinear medium.