THERMALLY CONTROLLED ACTIVE HEAT SWITCH SYSTEM

Abstract: A heat transfer changeover switch capable of effecting or cutting off positively heat transfer, requiring no contact or separation of a solid contact of a switch piece, easily being incorporated in a fine electronic device and generating no heat or vibration during a switch operation, wherein a heat pipe having a pipe for storing a beating medium therein is disposed between a hot heat source and a cold heat source and a heating medium supplying/discharging device for supplying/discharging the heating medium to and from the pipe is provided, whereby heat transfer between the hot heat source and the cold heat source via the heat pipe is effected or cut off by using the heating medium supplying/discharging device that changes over between supply and discharge of the heating medium to and from the pipe.

Description: TECHNICAL FIELD The present invention relates to a heat switch for switching between heat transmission and interruption of heat transmission between an intense heat source and a cold heat source. This technique can be used for controlling heat transmission (On) to and interruption of heat transmission (Off) of an electronic device and the like. BACKGROUND ART Members (superconducting members) made of superconducting material may be used for an electronic device and the like in some cases. Such superconducting members are necessary to be maintained in an environment of an extremely low operating temperature. Therefore, a refrigerator that functions as a cold heat source is used and a cold head of the refrigerator and the superconducting member to be cooled are connected through a heat pipe to maintain heat transmission between them. However, energy consumption increases when the refrigerator is always operating. Because the superconducting member has low resistance and a low calorific value, it is possible to maintain a heat conductive member in the operating environment of the extremely low temperature for a while by only interrupting the heat transmission to the superconducting member from the refrigerator even if operation of the refrigerator is stopped. At this time, a change-over switch for switching between heat transmission and interruption of heat transmission between the heat conductive member and the cold head of the refrigerator is necessary. Although contact of and separation between a switch piece and a solid contact is used in a conventionally-conceived heat switch, incorporating such a change-over switch that requires mechanical movement into a minute electronic device adds many constraints to a structure and driving of the switch piece involves vibration or heat generation in many cases. Therefore, development of a change-over switch that can reliably switch between heat transmission and interruption of heat transmission, does not require contact of and separation between the switch piece and the solid contact, and does not generate heat or vibration during operation of the switch is desired. A controllable heat pipe is disclosed in GB 2003596. In the GB2003596 the heat pipe is controllable in that the quantity of working fluid is adjusted. The heat pipe is communicated with a container through conduit 6 and value 8 and the work fluid flows from heat pipe to the container through them using pressure change of the container. Therefore the work fluid can not be removed from heat pipe completely at a time of switching off and a part of work fluid remains in the heat pipe. Because the remaining work fluid in the heat pipe transmits the heat, perfect interruption of the heat transmission cannot be realized at a time of switching off. The present invention has been accomplished with the above circumstance in view and it is an object of the invention to provide a change-over switch for heat transmission that can reliably switch between heat transmission and interruption of heat transmission, does not require contact of and separation between a switch piece and a solid contact, can be easily incorporated into a minute electronic device, and does not generate heat and/or vibration during operation of the switch. DISCLOSURE OF THE INVENTION Corresponding to the object a thermally controlled active heat switch system includes a heat pipe having a pipe that can contain heating medium and disposed between an intense heat source and a cold heat source and a heating medium supply and exhaust device for supplying and exhausting said heating medium to and from said pipe, said heating medium supply and exhaust device including a valve and a vacuum pump, wherein said system transmits heat and interrupts heat transmission between said intense heat source and said cold heat source through said heat pipe by switching between supplying the heating medium to said pipe and exhausting of said heating medium from said pipe by opening said valve thereby reducing pressure in said pipe and shifting a state of said heating medium from gas-liquid two phase coexisting state to a gas-phase state, and then exhausting said gas-phase state heating medium using said vacuum pump resulting in the inside of said heat pipe being brought into a vacuum-insulated state. BRIEF DISCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory block diagram showing a heat switch system, FIG. 2 is a phase diagram showing an actuation principle of a heat pipe used as a heat switch. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing an embodiment. In FIG. 1, a reference numeral 1 designates a heat switch system. The heat switch system 1 has a heat pipe 2 and a heating medium supply and exhaust device 3. The heat pipe 2 is disposed between a cold head 5 of a refrigerator 4 and a superconducting member 6 to be cooled. The heat pipe 2 is a heat-transmitting element for transferring heat by reducing pressure within a pipe 9 made of aluminum, stainless steel, copper, or the like, transferring heating medium such as Freon, ammonia, air, water through the pipe 9, and giving and receiving latent heat of vaporization. Such a heat pipe 2 itself is well known to those skilled in the art. The heat pipe 2 has a condenser section 7, a heat transmission interrupting section 8, and an evaporator section 11. The condenser section 7 and the cold head 5 for transmitting heat therebetween and the evaporator section 11 and the superconducting member 6 for transmitting heat therebetween are housed in a cryostat 12. The heating medium supply and exhaust device 3 has a supply and exhaust pipe 13 that communicates with an inside of the pipe 9 of the heat pipe 2. To the supply and exhaust pipe 13, an exhaust pipe 15 is connected through a safety valve 14. Pressure in the supply and exhaust pipe 13 is measured by a pressure gauge 16. To the supply and exhaust pipe 13, a buffer tank 17, a vacuum pump 18, an air intake pipe 21, and a heating medium cylinder 22 are connected. To the air intake pipe 21, an air-desiccating device 23 is connected. Reference numerals 24, 25, 26, 27, and 28 respectively designate valves. An operation of active heat control by a heat switch system 1 having the above structure is as follows. Heat medium is selected by switching between the valves 25 and 26. If the heating medium is air, the valves 25 and 28 are opened to cause the air to flow into the buffer tank 17 temporarily, and then the valve 24 is opened to cause the air to flow into the heat pipe 2 through the supply and discharge pipe 13. A required amount of the air that has flowed into the heat pipe 2 is liquefied by a condenser section 7 and then, the valve 24 is closed. In the heat pipe 2, the air operates as the heating medium and transfers heat from the superconducting member 6 to be cooled to the cold head 5 by transferring vapor and giving and receiving latent heat of vaporization. Such an operation of the heat pipe 2 is known. Next, in order to interrupt the heat transmission between the superconducting member 6 and the cold head 5, the valve 24 is opened. Thus, as shown in the phase diagram in FIG. 2, by shifting a state from gas-liquid two-phase coexisting state 1 to a gas-phase state 2 in the phase diagram, and then by quickly reducing pressure in the heat pipe 2 and exhausting the heat pipe 2 of the air by using the vacuum pump 18, the inside of the heat pipe 2 is brought into a vacuum heat-insulated state. Thus, the heat-transmitting function of the heat pipe 2 is stopped and the heat transmission between the superconducting member 6 and the cold head 5 is interrupted. Air as the heating medium can be obtained easily in an environment shown in FIG. 2 and the heat pipe 2 can be easily filled with air again. When the heating medium is gas such as nitrogen, the heating medium cylinder 22 filled with the heating medium is necessary. Especially, when the heat pipe 2 is a thermosiphon, swift switching between On (heat transmission) and Off (interruption of heat transmission) is possible by miniaturization. The thermosiphon is a gravity circumfluent-type wickless heat pipe having a sealed cylindrical pipe containing a small amount of liquid (heating medium). INDUSTRIAL APPLICABILITY As described above, according to the active heat control heat switch of the invention, because supply and exhaust of the heating medium which are indispensable to the operation of the heat pipe are controlled to turn on and off a function of the heat pipe, the change-over switch of heat transmission which can reliably switch between heat transmission and interruption of heat transmission, does not require contact of and separation between the switch piece and the solid, can be easily incorporated into the minute electronic device, and does not generate heat or vibration during operation of the switch can be obtained.

Claims: A thermally controlled active heat switch system (1) comprising: a heat pipe (2) having a pipe (2) that can contain heating medium and disposed between an intense heat source (6) and a cold heat source (5) and a heating medium supply and exhaust device (3) for supplying and exhausting said heating medium to and from said pipe, said heating medium supply and exhaust device including a valve (24) and a vacuum pump (18), wherein said system transmits heat and interrupts heat transmission between said intense heat source and said cold heat source through said heat pipe by switching between supplying the heating medium to said pipe and exhausting of said heating medium from said pipe by opening said valve (24) thereby reducing pressure in said pipe and shifting a state of said heating medium from gas-liquid two phase coexisting state to a gas-phase state, and then exhausting said gas-phase state heating medium using said vacuum pump (18) resulting in the inside of said heat pipe being brought into a vacuum-insulated state.

Inventors: NAKANOU AKIHIRO, SHIRAISHI MASAO, NAKANOU, AKIHIRO, SHIRAISHI, MASAO, NAKANOU, AKIHIRO,
Applicants: AGENCY IND SCIENCE TECHN, JAPAN AS REPRESENTED BY DIRECTOR-GENERAL
Application year: 1999
Main classification: F28D15
IPC codes: F25D19, F28D15, F17C3