Kohoichi Suzuki

Effect of condition of heating surface on pool boiling heat transfer. On boiling for unwettable surface and grooving surface.

Boiling heat transfer was investigated by experiment for grooving surfaces and some unwetted heating surfaces which were coated on the small copper surface with Teflon and some silicon materials. For a Teflon coated surface, the boiling curve showed the same characteristics as that of the copper surface, but the coefficient of heat transfer was considerable low in the nucleate boiling region. For some silicon coated surfaces, the boiling curve was much different from the usual heat transfer in pool boiling. The heat flux increased monotonously with the increase of the super heat and no critical heat flux and minimum heat flux were observed. For grooving surfaces, the critical heat flux was considerable low and observed at lower superheat than that in conventional boiling heat transfer.

A Study on Mass Transfer between Recirculation Zone and Outside Flow of Annular Premixed Flame

A mass transfer between recirculation zone and outside flow of an annular premixed propane flame was investigated experimentally using MgO powder tracing method and NaCl flame emission. The loacation of the stagnation point in the recirculation zone of the burning flow moved gradually from the nozzle exit with an increase of the gas exit velocity and became constant independently of the gas exit velocity in the very high velocity region. In the region of lower gas exit velocity, the average residence time of the fluid in the recirculation zone of the burning flow was evidently smaller than the time of the cold flow (air) at the same exit velocity, and both residence times decrease gradually with an increase of the gas exit velocity and became a same constant value in the region of very high velocity. Thus, the rate of mass transfer through the surface of the recirculation zone of a high velocity burning flow issuing from the annular nozzle was estimated by the data on the annular air jet.

A study on swirling turbulent diffusion flames (On turbulence intensity at the burner port of hydrogen flames)

The flame length of swirling turbulent diffusion flames of hydrogen, rising vertically from a cylindrical tube in free air, was measured by means of photography, and the turbulence intensity of the gas flow at the burner port was measured by LDV. The swirling intensity had a strong effect on the flame length, and the empirical equation was obtained as a function of the swirl number at the burner port for the flame length in the fully developed turbulent region. The turbulence intensity increased linearly with the swirl number at the burner port, and the mixing length in the eddy diffusivity at the burner port decreased exponentially with the swirl number.