Magnetic field control of cryogenic heat pipes
This paper deals with cryogenic heat pipes controlled by static magnetic field. Heat pipe is an equipment which allows a very effective heat transport. They are commonly used in electronic devices and in many other types of equipment as well. Some applications require heat flow controllability. For that purpose heat pipes are modified to many different constructions with variable heat conductance. Magnetic field control of heat transport is a new solution researched in a few laboratories in the world and still not practically applicated. According to the results of some experiments, implemented in our laboratory and several another laboratories, it seems to be possible to control heat transport in chosen types of heat pipes by a static magnetic field. The cryogenic heat pipe filled with pure oxygen has been made for that purpose and a testing device has been arranged as well. We have found out that the heat transport efficiency of the heat pipe has rapidly decreased by a magnetic field exposure. Some interesting results of our experiments will be presented in this paper.
Control of heat transport in heat pipes by magnetic fields
We have observed that gas flow can be blocked or disturbed by magnetic fields. To explain this phenomenon, we developed a model called a ‘‘magnetic curtain’’ based on the paramagnetic properties of the oxygen molecule. In this paper, we applied this phenomenon to the control of heat transport in heat pipes. We used a heat pipe 20 mm in diameter and 500 mm in length packed with oxygen as a working fluid. We positioned this device vertically in an airgap 70‐mm wide between the poles of electromagnet with 240 mm in diameter, in the direction perpendicular to the axis of the magnetic poles. The top side of the heat pipe was chilled with liquid nitrogen (77 K), and the lower side of the heat pipe was exposed to the room temperature (290 K). The efficiency of heat transport was measured by monitoring the change of the temperature at seven points inside and outside of the heat pipe in response to the step change of the top temperature from 290 to 77 K. When the middle part of the heat pipe was exposed to magneti...
Quenching of flames by magnetic fields
An experiment has been demonstrated to show a phenomenon involving quenching of candle flames using magnetic fields. An electromagnet with a pair of columnar magnetic poles in which inner sidepieces were hollowed out was used. Magnetic fields of 1.5 T at the brim gave a gradient of 50–300 T/m in the direction perpendicular to the pole axis when the distance of the airgap was in a range of 5–10 mm. A candle was burned in the hollowed space between magnetic poles, and candle flames were exposed to magnetic fields. The flames were quenched a few seconds after the onset of field exposures. A model, called a ‘‘magnetic curtain,’’ was introduced to explain this phenomenon. It is assumed that the magnetic curtain is a wall of air which is formed by magnetic fields. The magnetic curtain, which is also called an ‘‘air curtain,’’ blocks air flow in and out of the hollowed space. The interception of oxygen by the magnetic curtain quenches flames. The magnetic curtain also presses back flames and other gases.