BASIC STUDY FOR NATURAL CONVECTIVE HEAT TRANSFER OF LIQUID METAL LITHIUM UNDER MAGNETIC FIELD

点击翻译按钮获取中文摘要

Liquid metal technology is one of the key technologies of future energy resources. Liquid sodium is used in the fast breeder reactor, and liquid lithium in fusion bracket and space reactor. In the project of International Thermonuclear Experimental Reactor, liquid lithium is being planned as a candidate material for demonstration breeder branket which will be equipped in the second phase of ITER operation. Lithium will be stored in a pool through which many tubes of helium gas or water penetrate for cooling. In such an application natural convection will play larger role in heat transfer in order to avoid MHD effect from magnetic field. Natural convective heat transfer is also important theme to understand core cooling behavior after loss of flow event in fast breeder reactor.In the first year, the experimental apparatus was fabricated. It has a heater pin on the center surrounded by forced air cooled surface of the lithium container. Preliminary experiment was conducted to get heat transfer property under low surface heat flux.In the second year, experiment was conducted with magnetic field of up to 0.8 T and heat flux up to 20 w/cm^2 to get detailed temperature distribution and heat transfer property. Fluctuations in temperature were measured. With analyzing mutual correlations between arbitrary two measuring points, flow behavior was estimated of local and whole lithium region. It was found that local fluctuation in temperature was enhanced by relatively weak magnetic field from 500 G to 3000 G,flow pattern changed very much from that without magnetic field, and fluctuation disappeared above a certain magnetic field intensity. Strong correlation was found between the amplitude of the fluctuation and heat transfer coefficient. The results obtained from present experiment may be applied to the design of demonstration branket in ITER or demo reactor with using magnetic generated fluctuation to enhance heat transfer under magnetic field.