Nishio Lab. Nishio Lab.This Laboratory aims at contributing to a better understanding of the thermal phenomena related to heat transfer/transport and developing new thermal control techniques for cooling and material processing systems. In the heat transfer/transport phenomena, we focus on the phenomena of phase change from liquid phase and oscillation-induced heat transport phenomena (thermoacoustic phenomena). In the thermal control techniques, we focus on the followings;heat transfer enhancement, cooling stability of superconducting cables, immersion cooling of electronic devices, cooling in the thermo-mechanical control process for steel, and cooling in rapid solidification.
(1)Elementary Processes and Heat Transfer in Phase Change Phenomena
In the phenomena of phase change from liquid phase, such as boiling and solidification, very complicated structures are produced by elementary processes such as nucleation, heterogeneous growth of a new phase, and formation of stable/unstable interfaces. Thus, to develop heat transfer models with such phase change phenomena, a better understanding on the elementary processes and inclusion of such processes into models are indispensable. Based on such recognition, investigated for boiling phenomena are:the thermodynamic stability criteria of a pre-existing vapor nucleus trapped in a cavity to estimate nucleation site density;the thermal/hydrodynamic restriction imposed on liquid- solid contact to develop a transition boiling model;and the stability and dynamic behavior of vapor- liquid interface to describe the whole of film boiling behavior. In solidification, we focus on the stability of the contact line between a moving chilled surface and a melt meniscus to elucidate and suppress the formation of contact resistance in rapid solidification.(2)Analysis and Application of Oscillation-Induced Heat Transport Phenomena
Both steady and oscillatory viscous laminar flows can induce extraordinary heat diffusion or heat pumping effects. We call such phenomena an "Oscillation-Induced Heat Transport Phenomena." If the oscillating fluid is a liquid, the enhanced diffusion effect is much stronger than the heat pumping effect, and heat transport devices such as the so-called dream pipe can be developed by using this phenomena. We analyzed and developed phase-shifted oscillation-controlled heat-transport tubes with effective thermal conductivities much higher than those of prototype dream pipes. If the oscillating fluid is a gas, the heat pumping effect can overcome the enhanced diffusion effect. In this case, new type refrigerators without low-temperature moving parts can be developed by using this phenomena, and a new type of pulse-tube refrigerators is currently examined.(3)Heat Transfer Enhancement
Development of heat transfer enhancement techniques is strongly anticipated in various fields. In the case of turbulence promoters, turbulent heat transfer is enhanced at the expense of increase in pumping power. Therefore, perforated-rib-type turbulence promoters have been developed to reduce the increase in pumping power. As for cooldown of a surface by boiling heat transfer, it was found that a thin insulating coating can reduce markedly the cooling time of the surface. We named this phenomena the "paradox of insulating coating." Heat transfer enhancement by the electro- hydrodynamic effects have been also examined to enhance boiling heat transfer and reduce the effect of surface orientation.(4)Thermal Control Techniques in Cryogenic, Electronic and Material Processing Systems
One of the emerging technologies is the development of thermal control techniques for superconducting cables, electronic/optical device cooling, micro-machines, space equipments, and material processing. Some of our achievements are summarized as follows:The paradox of insulating coating is proven to be effective in securing the stability of superconducting cables cooled by liquid helium;In spray cooling, experimental data of the effects of surface and flow parameters have been accumulated to stabilize the cooling process of steel slabs;Fine particles of amorphous metal are proven to be fabricated in rapid solidification caused by small scale vapor explosion.
Color high-speed video(1000fps)
High speed video(2048fps)
Image processing system
Transient memory recorders
Regulated DC power supply(16V-500A max)
Regulated DC power supply(30V-300A max)
Infrared heating equipments
Circulated-type thermostats
Shigefumi NISHIO, Dr., Professor
Shinichi NAGATA, Research Associate
Hitsuhiro UEMURA, Technical Associate
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