Ken-ichiro Sugiyama

Simulation of Potassium Condensation by DSMC Method.

The evaporation and condensation phenomena of alkali metals are not correctly described by the analysis using the continuum equations, because discontinuity of physical quantities such as temperature at the vapor-liquid interface occurs in the phase change process. The authors apply the direct simulation Monte Carlo (DSMC) method, which is based on the molecular gas dynamics, to the problem of potassium condensation. The simulation results are found to be in excellent agreement with the experimental results previously reported by two of the authors, when the condensation and evaporation coefficients are set to unity. It is also confirmed that a slight shift of evaporation and condensation coefficients from unity considerably changes the simulation result so that it disagrees with the experimental data. The authors conclude from these results that the direct simulation Monte Cairo method is very useful to predict the phase change problems of alkali metals.

Combined convective heat transfer of liquid sodium flowing across tube banks Examination with single row of tube normal to flow in direction of gravity.

In order to clarify the heat transfer characteristics of combined convection of liquid sodium, a numerical analysis is performed for liquid sodium which flows through a single horizontal row of tubes in the direction of gravity. The correlation of heat transfer char- acteristics between liquid sodium and ordinary fluids is also discussed.The heat transfer characteristics at large Reynolds numbers are improved when the Richardson number is increased, and the improvement rate is enlarged with increase in p/d value, since convection effect is relatively large. However heat transfer coefficients do not differ from those of forced convection at small Reynolds numbers even when the Richardson number reaches a high value bacause of conduction effect. A good consistence of heat transfer characteristics of combined convection between liquid sodium and air is obtained at the same Peclet number and Richardson number, This means that the fundamental heat transfer characteristic of combined convection of liquid sodium can be investigated with ordinary fluids.

Natural Convection Heat Transfer from a Horizontal Cylinder to Liquid Sodium

The objective of the present study is to clarify the heat transfer characteristics of laminar natural convection around a horizontal circular cylinder immersed in liquid sodium. We show at first that the Boussinesq approximation is more applicable to sodium than to air with a good accuracy. The Boussinesq-approximated Navier-Stokes and energy equations are solved by using a finite-difference method. The following correlation equation is obtained from the present numerical results:ln Nu=0.172+0.164 ln GrPr2+0.003 (ln GrPr2)2, (104≤Gr≤109). It is found from the comparison with the present results that previous correlation equations predict lower value than the present one.