US3658125A - Internal configuration for a radial heat pipe - Google Patents

Internal configuration for a radial heat pipe Download PDF

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Publication number
US3658125A
US3658125A US697181A US3658125DA US3658125A US 3658125 A US3658125 A US 3658125A US 697181 A US697181 A US 697181A US 3658125D A US3658125D A US 3658125DA US 3658125 A US3658125 A US 3658125A
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United States
Prior art keywords
heat
heat pipe
cylindrical wall
wall
capillary
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Expired - Lifetime
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US697181A
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English (en)
Inventor
Robert A Freggens
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RCA Corp
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RCA Corp
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Publication date
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/027—Collectors
    • H01J23/033—Collector cooling devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
    • F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
    • F28D15/04—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J19/00—Details of vacuum tubes of the types covered by group H01J21/00
    • H01J19/28—Non-electron-emitting electrodes; Screens
    • H01J19/32—Anodes
    • H01J19/36—Cooling of anodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2893/00—Discharge tubes and lamps
    • H01J2893/0001—Electrodes and electrode systems suitable for discharge tubes or lamps
    • H01J2893/0012—Constructional arrangements
    • H01J2893/0027—Mitigation of temperature effects

Definitions

  • a radial heat pipe has a plurality of radial struts covered with [51] lnt.Cl.
  • the heat pipe also has a tube extending down 3,405,299 10/1968 Hall et al ..165/ x its central axis which Permits force to he applied to the heat source member to separate the heat source member from the FOREIGN PATENTS OR APPLICATIONS heat P 965,696 8/1964 Great Britain ..317/234 11 Claims, 2 Drawing Figures 0 a? 91 r 1 1 1 Z/ 9 1 7 7 f I 1 I -Z8 l 1 l 1 w-f I I 7642/ 45% 78 4 I g I A I 2 4:50
  • the invention relates to an improved heat exchanger for electron tubes and particularly to a heat exchanger incorporating the principles of a heat pipe in which heat transfer is effected radially.
  • One type of heat pipe is a vapor device which is used to convey heat radially outward from a central heat source member such as an electron tube to surrounding heat dissipation means.
  • This type of heat pipe comprises, for example, a closed annular structure having a lining of capillary material, and a vaporizable working medium therein.
  • the closed annular structure is defined by an inner cylindrical wall and a coaxial outer cylindrical wall radially spaced from the inner wall. Disklike top and bottom walls connect the ends of the inner and outer cylindrical walls and complete the annular structure.
  • the capillary lining covers the inner surfaces of the walls surrounding this annular structure and may consist of wire mesh or porous matrix material.
  • the working medium saturates the capillary lining and is selected to have a vaporization temperature equal to the operating temperature of the heat pipe. For most efficient operation, all undesirable foreign gases are removed from the annular space which constitutes the active area of the heat pipe and the working medium.
  • the exterior surface of the heat input wall forms the wall of a central cylindrical heat input cavity.
  • the heat source member to be cooled is inserted into this central heat input cavity and thereby placed in thermal contact with the exterior surface of the heat input wall of the heat pipe.
  • Some electronic devices such as the collector of a klystron and other external anodes of power tubes have a configuration which makes them especially suitable for cooling by a radial heat pipe, since they can be designed to fit tightly into the heat input cavity.
  • the heat pipe operates as an efficient heat flux transformer by transferring heat from the smaller surface area of a heat source to a larger area which is suitable for air cooling.
  • Heat from the heat source is conducted through a metallic heat input wall and causes the liquid working medium which saturates the capillary lining on the interior surface of the heat input wall to vaporize and till the annular space between the heat pipe walls.
  • the vaporized working medium then condenses on the capillary lining of the outer or heat output wall of the heat pipe giving up its heat of vaporization. In this way, heat is transferred from the heat source to an area where it can be effectively dissipated to the ambient by radiation, convection or other conventional means.
  • the heat transfer ability of heat pipes utilizing this radial heat transfer configuration has been limited by an inability to replenish the supply of liquid working medium in the heat input wall quickly enough.
  • Liquid working medium is transported from the heat output wall where it condenses, to the heat input wall by the pumping action of the capillary lining.
  • the liquid medium In order to reach the heat input wall after it has condensed on the heat output wall of the heat pipe, the liquid medium must flow across the disklike top and bottom walls of the annular structure. This is a relatively long distance and since the pumping action of the capillary lining is slow, it can require a relatively long time to return the liquid working medium to the heat input wall where it can be reused. This limits the amount of heat which can be transferred from the heat source member.
  • An improved thermal contact may be provided between the heat source member and the heat pipe which will allow the heat pipe to be removed readily from the heat source.
  • Means to apply pressure to the heat source member to further facilitate the removal of the heat pipe may also be included in the heat pipe.
  • FIG. 1 is a longitudinal sectional view of a preferred embodiment of an improved radial heat pipe
  • FIG. 2 is a sectional view taken along 2-2 of FIG. 1.
  • the heat pipe 10, shown in FIG. 1 is an annular structure which transfers heat outwardly from a cylindrical heat input wall 12 to a surrounding cylindrical heat output wall 14 where the heat is dissipated.
  • the heat output wall 14 is spaced radially from the heat input wall 12 forming an annular space 16 in the area between these walls.
  • a disklike bottom wall 18 connects the heat input wall 12 and the heat output wall 14 closing one end of the annular space 16.
  • the heat output wall 14 extends beyond the heat input wall 12 allowing heat from a heat source member to be transferred to a relatively large surface area which is suitable for air cooling.
  • the heat output wall 14 may be made coextensive with the heat input wall 12, but in this case more efficient cooling means such as liquid cooling should be employed to dissipate heat from the exterior of the heat output wall 12.
  • a centrally located heat input cavity 20 is adapted to receive a heat source member to be cooled and is designed to provide good thermal contact between the heat source member and the exterior of the heat input wall 12.
  • the sides of the cylindrical heat input cavity 20 are defined by the exterior surface of the heat input wall 12 and are coextensive therewith.
  • the cavity 20 has an opening 22 surrounded by the disklike bottom wall 18 through which a heat source member may be inserted.
  • the cavity 20 is terminated at its upper end, as viewed in FIG. 1, by a disklike member 24.
  • the disklike member 24 having a central opening 25 is attached to one end of the heat input wall 12 and acts as an additional heat input area.
  • a thin lining 26 of deformable thermally conducting material, such as gold or aluminum foil, is attached to the surface of the heat input cavity 20 to insure good thermal contact between the heat source member and the walls of the heat input cavity 20.
  • the portion of the heat pipe structure above the heat input cavity 20 comprises a second annular area 27 which is defined by the cylindrical heat output wall 14 and a central tubular structure 28.
  • the tubular structure 28 is coaxial with the heat output wall 14 and is connected at one end to the disklike member 24 at the top of the heat input cavity 20.
  • a disklike top wall 30 having a central opening 31 connects the other end of the tubular structure 28 with the surrounding heat output wall 14 and closes one end of the second annular structure 27.
  • the tubular structure 28 allows pressure to be exerted on the top of a heat source within the heat input cavity 20 by a threaded rod 32 to force the heat source member out of the cavity 20 and thereby disconnect the heat pipe from the latter member.
  • the tubular structure 28 is open at both of its ends. One end portion of the tubular structure 28 extends through the central opening 31 in the top disklike wall 30 and the other end portion extends through the central opening 25 in the disklike member 24 and opens into the heat input cavity 20.
  • Screw threads 34 extend over a portion of the inner surface of the tubular structure 28.
  • the threaded rod 32 may be inserted into the tubular structure 28 through the opening in the top wall 31, and by utilizing the mechanical advantage of the screw threads can exert a large axial force on a heat source member within the input cavity 20.
  • All the interior walls of the heat pipe structure are lined with a layer of capillary material 36 which stores a liquid working medium and transports the liquid working medium throughout the heat pipe by capillary action.
  • the capillary lining 36 may be made, for example of wire mesh or porous matrix material.
  • the working medium in liquid form saturates the capillary lining 36 of the heat pipe and vaporizes in those areas where heat is applied.
  • a liquid such as mercury, vaporizable at the operating temperature of the heat pipe, can be utilized as a working medium.
  • a plurality of thermally conducting radial fins 37 are attached to the exterior surface of the heat output wall 14 to dissipate heat from the heat output wall. Forced air can be directed through the fins 37 by any conventional means if additional cooling is desirable.
  • a plurality of radial struts 38 extend across the annular space 16 and connect the capillary lining on the heat output wall 14 with the capillary lining on the heat input wall 12 to facilitate the movement of liquid working medium from the heat output wall to the heat input wall.
  • the radial struts 38 comprise channels having a metallic base strip 40 and lateral metallic sides 41 perpendicular to the base strip 40.
  • a strip of capillary material 42 is attached to the base strip 40 between the perpendicular walls 41.
  • each of the struts 38 is attached to a narrow capillary ring 44 extending inwardly from the heat output wall 14 and the other end is attached to a narrow capillary ring 46 which extends outwardly from the heat input wall 12.
  • Capillary strips 42 within the struts 38 are contiguous with the capillary rings 44 and 46.
  • the heat pipe has 16 radial struts or channels 38 arranged in four levels 48, 50, 52 and 54 having four channels in each level.
  • the channels in each of the four levels are equally spaced circumferentially around the heat input wall 12.
  • the channels in each of the four levels are also equally spaced circumferentially from the adjacent channels which are in the adjacent levels.
  • each of four channels in each quadrant of the annular space 16 is in a different level and the channels are made sufficiently narrow so that spaces 56 are provided between the channels 38.
  • This arrangement permits the channels 38 to provide a uniform flow of liquid working medium from the heat output wall 14 to the heat input wall 12 and yet avoids hindering the vapor circulation in the heat pipe to a significant extent.
  • the radial channels 38 slope downwardly with respect to the operational position of the heat pipe from the heat output wall 14 to the heat input wall 12 so that gravity aids the flow of the working medium in liquid form toward the heat input wall 12 when the heat pipe is oriented as shown in FIG. 1.
  • An angle of from about 10 to about 80 with respect to the vertical position as shown in FIG. l is sufficient to provide the proper flow of liquid working medium to the heat input wall 12. The exact angle of inclination for best results depends on the capillary material used in the channels, the fluid viscosity of the working medium and the length of the channels 38.
  • This heat pipe configuration has been used to cool the collector of a klystron (not shown).
  • the collector of the klystron may be fitted tightly into the cylindrical heat input cavity 20 so that there is good thermal contact between the collector and the walls of the heat input cavity 20.
  • Heat from the collector is conducted through the metallic wall of the heat input cavity 20 causing the working medium within the capillary lining 36 on the heat input wall 12 to vaporize and expand throughout the interior of the heat pipe.
  • the working fluid vaporizes, it absorbs heat, thereby cooling the collector.
  • the vaporized working fluid condenses on the heat output wall 14 giving up its latent heat of vaporization. This heat is then dissipated by the metallic fins 37 attached to the exterior of the heat output wall 14.
  • the radial channels 38 provide a direct connection across the annular space 16 between the capillary lining 36 on the heat output wall 14 and the capillary lining on the heat input wall 12. These channels 38 greatly decrease the distance which the working fluid must flow through the capillary lining 36 to reach the heat input wall 12 from the heat output wall 14 since it is no longer necessary for the liquid working medium to flow only through the capillary lining on the disklike bottom wall 18 or top wall 31). inclining the channels 38 downwardly from the heat output wall 14 to the heat input wall 12 further increases the return flow of working liquid.
  • the spacial arrangement aforementioned of the radial channels 38 contributes to a uniform and relatively rapid distribution of liquid working medium to all points on the heat input wall 12.
  • the vaporized working medium condenses on the heat output wall 14, it flows through the capillary lining 36 until it reaches one of the capillary rings 44. Since the rings 44 extend through the capillary lining on the heat output wall 14, the flow in the capillary wall lining 36 is interrupted and the liquid then flows along the capillary ring 44 until it reaches one of the radial channels 38. Capillary action in the rings 44 will cause the liquid working medium to flow into the contiguous capillary strips 42 on the channels 38 and move through the channel 38 toward the capillary rings 46 on the heat input wall 12. If the channels 38 are inclined downwardly from the heat output wall 14 to the heat input wall 12 gravity will aid capillary action to move the liquid working medium through the channels 38.
  • the capillary rings 46 are located at four different levels on the heat input wall 12, they serve to distribute the liquid uniformly to both the top and bottom of heat input wall. Since the capillary rings 46 extend around a circumference of the heat input wall 12, the liquid working medium will flow along them to all points on the surface of the heat input wall 12 and not just to the areas adjacent to the channels 38. Distributing the liquid working medium uniformly to all points on the heat input wall 12 provides more uniform cooling for the heat source and improves the overall heat transfer capability of the apparatus.
  • radial struts 38 have been shown in a channel structure in the preferred embodiment, other strut configurations will perform satisfactorily.
  • FOr example a planar strut having no lateral sides 41 can be used rather than the channels shown. If the strip of capillary material 42 is rugged enough to be self-supporting, it can be used without the underlying supporting strip 40 or the lateral sides 41 so that the entire strut is made of capillary material.
  • the walls defining the cavity 20 are lined with a thin metallic lining 26 to provide good thermal contact between the heat source and the exterior of the heat input wall 12.
  • the thin deformable metallic lining 26 may be a gasket which is attached as by brazing to the walls of the cavity 20.
  • the metal gasket 26 may be a thin layer of a malleable metal such as gold or aluminum. Alternatively, a thin layer of such a malleable metal may be plated onto the surface of the cavity 20. In either case, this thin layer of metal will deform easily, so that it readily accommodates itself to the respective shapes of the heat source member, not shown, and the cavity and thereby provides good thermal contact with the heat input wall 12.
  • the cylindrical sides of the cavity 20 may be tapered inwardly from opening 22 at a small angle of about 1 for example. This slight tapering will provide a truncated cylindrical surface on which good contact will exist between the cylindrical surfaces of the heat source member and the heat input wall 12.
  • the presence of the central threaded tube 28 facilitates the removal of the heat pipe from a heat source member.
  • Surface diffusion occurring over an extended period of high temperature operation tends to fuse the exterior metal surfaces of the heat source member and of the walls of cavity 20 making it difficult to separate the two
  • a threaded rod 32 may be inserted through the opening 31 in the ringlike top wall 30 and into the tubular structure 28. This rod extends through the tube 28 and exerts pressure against the top of the heat source member through the opening in disklike member 24.
  • the mechanical advantage derived from the screw threads allows sufficient pressure to be brought to bear at the center of the heat source member to cause it to be removed from the heat pipe. Since the heat pipe has a longer potential useful life than the klystron collector, it is advantageous to be able to remove the heat pipe so that it is available for reuse.
  • first and said second cylindrical walls being spaced radially to define an annular space therebetween;
  • said radial struts being arranged in a plurality of discrete levels along said vertical axis, each of said struts being circumferentially spaced from the struts in the adjacent levels so that no strut is located vertically above any part of another strut in an immediately adjacent lower level;
  • capillary means disposed on at least one surface of said radial struts and connected at each end thereof to said capillary structure.
  • said struts in each level being equally circumferentially spaced around said second cylindrical wall.
  • a heat pipe as described in claim 1 including a first group of capillary rings extending into said annular space from said first cylindrical wall and a second group of capillary rings extending into said annular space from said second cylindrical wall,
  • each of said radial struts extending between one of said first group of capillary rings and one of said second group of capillary rings.
  • a heat pipe radially arranged about a central vertical axis for cooling a portion of a heat source member comprising:
  • first and said second cylindrical walls being spaced radially to define an annular space therebetween;
  • capillary means disposed on at least one surface of said radial struts and connected at each end thereof to said capillary structure.
  • a heat pipe for cooling a part of an electron tube comprising:
  • means including a capillary structure within said annular space for transferring heat from said second cylindrical wall to said first cylindrical wall.
  • a heat pipe as described in claim 8 wherein said thin deformable metallic lining comprises a thin layer of metal plated on the inner surface of said cavity.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
  • Containers, Films, And Cooling For Superconductive Devices (AREA)
US697181A 1968-01-11 1968-01-11 Internal configuration for a radial heat pipe Expired - Lifetime US3658125A (en)

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US69718168A 1968-01-11 1968-01-11

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US (1) US3658125A (de)
JP (1) JPS4635955B1 (de)
DE (1) DE1800984A1 (de)
FR (1) FR1584846A (de)
GB (1) GB1202959A (de)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3756217A (en) * 1971-11-23 1973-09-04 Jenn Air Corp Damper for ventilating air flow control for indoor open-air cooking device
US3811493A (en) * 1970-04-08 1974-05-21 Singer Co Thermal shield
US3943964A (en) * 1970-07-07 1976-03-16 U.S. Philips Corporation Heating device
US4012770A (en) * 1972-09-28 1977-03-15 Dynatherm Corporation Cooling a heat-producing electrical or electronic component
US4091264A (en) * 1976-08-13 1978-05-23 Seal Incorporated Heat transfer
US4582121A (en) * 1977-06-09 1986-04-15 Casey Charles B Apparatus for and method of heat transfer
US6226178B1 (en) 1999-10-12 2001-05-01 Dell Usa, L.P. Apparatus for cooling a heat generating component in a computer
US20070079954A1 (en) * 2005-10-11 2007-04-12 Chin-Wen Wang Heat-Dissipating Model
US10107560B2 (en) 2010-01-14 2018-10-23 University Of Virginia Patent Foundation Multifunctional thermal management system and related method

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB965696A (en) * 1960-05-13 1964-08-06 Philips Electrical Ind Ltd Improvements in or relating to semiconductor devices
US3405299A (en) * 1967-01-27 1968-10-08 Rca Corp Vaporizable medium type heat exchanger for electron tubes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB965696A (en) * 1960-05-13 1964-08-06 Philips Electrical Ind Ltd Improvements in or relating to semiconductor devices
US3405299A (en) * 1967-01-27 1968-10-08 Rca Corp Vaporizable medium type heat exchanger for electron tubes

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Busse, C. A. Optimization of Heat Pipe Thermionic Converters, 1965, Euratom EUR2534.e, pp. 1 and 13. *
Deverall, J. E. et al. High Thermal Conductance Devices, 4/1965, Los Alamos Scientific Laboratory LA 3211, pp. 1 and 35. *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3811493A (en) * 1970-04-08 1974-05-21 Singer Co Thermal shield
US3943964A (en) * 1970-07-07 1976-03-16 U.S. Philips Corporation Heating device
US3756217A (en) * 1971-11-23 1973-09-04 Jenn Air Corp Damper for ventilating air flow control for indoor open-air cooking device
US4012770A (en) * 1972-09-28 1977-03-15 Dynatherm Corporation Cooling a heat-producing electrical or electronic component
US4091264A (en) * 1976-08-13 1978-05-23 Seal Incorporated Heat transfer
US4582121A (en) * 1977-06-09 1986-04-15 Casey Charles B Apparatus for and method of heat transfer
US6226178B1 (en) 1999-10-12 2001-05-01 Dell Usa, L.P. Apparatus for cooling a heat generating component in a computer
US20070079954A1 (en) * 2005-10-11 2007-04-12 Chin-Wen Wang Heat-Dissipating Model
US7610947B2 (en) * 2005-10-11 2009-11-03 Pyroswift Holding Co., Limited Heat-dissipating model
US10107560B2 (en) 2010-01-14 2018-10-23 University Of Virginia Patent Foundation Multifunctional thermal management system and related method

Also Published As

Publication number Publication date
DE1800984A1 (de) 1969-08-07
JPS4635955B1 (de) 1971-10-21
FR1584846A (de) 1970-01-02
GB1202959A (en) 1970-08-26

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