U.S. patent application number 11/792100 was filed with the patent office on 2008-10-30 for magnetic convection heat circulation pump.
Invention is credited to Kenji Higashi, Shinichi Nakasuka, Hironori Sahara.
Application Number | 20080264068 11/792100 |
Document ID | / |
Family ID | 36565056 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080264068 |
Kind Code |
A1 |
Nakasuka; Shinichi ; et
al. |
October 30, 2008 |
Magnetic Convection Heat Circulation Pump
Abstract
A magnetic convection heat circulation pump, wherein magnets are
disposed inside a magnetic field flow passage for passing a
magnetic fluid therein or on a part of the inner wall surface of a
circulation flow passage in a magnetic pump thermally joined to a
heat receiving part. The magnetic fluid is driven since a magnetic
force is directly applied to the magnetic fluid and a large
temperature gradient is produced between the heat receiving part
and the magnetic pump due to a difference between a heat quantity
transferred from the heat receiving part indirectly to the magnetic
pump and the heat quantity of the magnetic fluid led into the
magnetic pump.
Inventors: |
Nakasuka; Shinichi;
(Bunkyo-ku, JP) ; Sahara; Hironori; (Bunkyo-ku,
JP) ; Higashi; Kenji; (Yamatotakada-shi, JP) |
Correspondence
Address: |
MILLEN, WHITE, ZELANO & BRANIGAN, P.C.
2200 CLARENDON BLVD., SUITE 1400
ARLINGTON
VA
22201
US
|
Family ID: |
36565056 |
Appl. No.: |
11/792100 |
Filed: |
November 30, 2005 |
PCT Filed: |
November 30, 2005 |
PCT NO: |
PCT/JP2005/021956 |
371 Date: |
June 1, 2007 |
Current U.S.
Class: |
62/3.3 |
Current CPC
Class: |
F28F 2250/08 20130101;
F28F 23/00 20130101; F28D 15/0266 20130101 |
Class at
Publication: |
62/3.3 |
International
Class: |
F25B 21/02 20060101
F25B021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2004 |
JP |
2004-350757 |
Claims
1. A magnetic convection heat pump comprising a heat receiving
section, a heat discharging section, a circulation path for a
magnetic fluid, and at least one magnet member for magnetically
driving said magnetic fluid, wherein said magnet member is disposed
in said circulation path in such a way that a portion thereof lies
in said heat receiving section whereby a temperature gradient is
created in said magnetic fluid flowing through said circulation
path in the vicinity of said magnet member.
2. A magnetic convection heat pump comprising a heat receiving
section, a heat discharging section, a magnetic pump section
including at least one magnet member and being thermally coupled to
said heat receiving section, and a circulation path for circulating
a magnetic fluid, said circulation path connecting said heat
receiving section, said heat discharging section and said magnetic
pump section in fluid communication, wherein said magnet member is
disposed in said circulation path in such a way that a portion
thereof lies in said heat receiving section whereby a temperature
gradient is created in said magnetic fluid flowing through said
circulation path in the vicinity of said magnet member.
3. The magnetic convection heat pump according to claim 1 wherein
said circulation path comprises a length of conduit.
4. The magnetic convection heat pump according to claim 1 wherein
said magnetic fluid contains a particulate ferromagnetic material
having an average particle size less than 30 .mu.m, said
ferromagnetic material being a ferrite comprised of a divalent
transitional metal and iron oxide.
5. The magnetic convection heat convection pump according to claim
1 wherein said magnetic fluid is an ionic liquid exhibity
magnetism
6. The magnetic convection heat convection pump according to claim
1 wherein said heat receiving section and said heat discharging
section are detachably connected to each other.
7. The magnetic convection heat pump according to claim 2 wherein
said magnetic flow path extends in said heat receiving section and
said magnetic pump to form a common magnetic flow section for both
of them.
8. The magnetic convection heat pump according to claim 2 wherein
said heat receiving section and said magnetic pump are constructed
from different materials having mutually different heat
conductivity values.
9. The magnetic convection heat pump according to claim 2, wherein
said magnetic fluid contains a particulate ferromagnetic material
having a coating of an ionic surfactant, and wherein said magnet
member has on their surfaces with which said magnetic fluid
contacts a coating of the same ionic surfactant as the coating of
said particulate ferromagnetic material.
10. The magnetic convection heat pump according to claim 2 wherein
said magnet member has on their surfaces with which said magnetic
fluid contacts an oil-repellent coating.
Description
TECHNICAL FIELD
[0001] The present invention relates to a device for transferring
heat energy. More particularly, it relates to a magnetic convection
heat circulation pump which utilizes a magnetic fluid exhibiting
temperature-dependent saturation magnetization.
[0002] Heat transfer devices utilizing magnetic convection of a
magnetic fluid exhibiting temperature-dependent saturation
magnetization have long been known, but they have not been put into
commercial practice for several reasons including the difficulty of
producing of a magnetic fluid having uniform distribution of finely
divided ferromagnetic particles of little or no residual
magnetism.
[0003] Attempts have been made to obviate the above problems in
recent years. For example, JP 10/231814A discloses a fluid flow
control device utilizing a paramagnetic gas exhibiting
temperature-dependent saturation magnetization, while JP 3/102804A
discloses a heat transfer device utilizing a magnetic fluid
exhibiting temperature-dependent saturation magnetization. In these
devices, a heater is provided in the vicinity of magnetic field to
create a temperature gradient in a fluid flow path by heating
externally.
[0004] However, the devices having external heating means have only
limited uses and are not suitable for cooling an object.
[0005] A system for moving a magnetic fluid through a fluid flow
path is known. The system comprises a plurality of electromagnets
disposed spaced apart in row alongside the fluid flow path and a
controller for sequentially energizing the electromagnets. However,
the system is complicated and expensive because of the controller
and requisite wiring.
DISCLOSURE OF THE INVENTION
[0006] It is an object of the present invention to provide a
magnetic convection heat circulation pump which utilizes a magnetic
fluid exhibiting temperature-dependent saturation magnetization
wherein the magnetic fluid is circulated in a flow path without
need for external power source, and wherein a large temperature
gradient of the magnetic fluid is created in the flow circuit to
thereby generate a gradient of the magnitude of saturation
magnetization of the magnetic fluid under the influence of a
magnetic field.
[0007] The above object is accomplished by the magnetic convection
heat circulation pump according to the present invention which
comprises a heat receiving section, a heat discharging section, and
a fluid circulation path for circulating a magnetic fluid between
said heat receiving section and said heat discharging section
wherein at least a magnet is disposed within said fluid circulation
path or part thereof in said heat receiving section so that a
magnetic convection is continuously created in said magnetic fluid
due to a temperature gradient in said fluid circulation path.
[0008] In the magnetic convection heat circulation pump of the
present invention, the magnetic fluid in the fluid circulation path
receives heat in said heat receiving section to decrease the
magnitude of saturation magnetization in response to the magnetic
field applied to the fluid circulation path and tends to displace
in the fluid circulation path toward the heat discharging section
creating magnetic convection. Therefore, the pump is simple in
structure, operates as far as a temperature differential is present
between the heat receiving and discharging sections, and has an
advantage of transferring a large quantity of heat by circulating
the magnetic fluid as fast as possible using a large temperature
differential.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic view of the magnetic convection heat
pump of the present invention having a magnet disposed in the fluid
circulation path.
[0010] FIG. 2 is a schematic view of similar heat circulation pump
having a pair of linearly connected magnets.
[0011] FIG. 3 is a schematic view of similar heat circulation pump
having a pair of magnets arranged in parallel.
[0012] FIG. 4 is a schematic view of similar heat circulation pump
having a pair of magnets arranged at an angle.
[0013] FIG. 5 is a schematic view of similar heat circulation pump
having a pair of magnets attached to the legs of an inverted
U-shaped ferromagnetic support member.
[0014] FIGS. 6 and 7 show schematically the magnetic convection
heat circulation pump of the present invention having a magnet
disposed in the fluid circulation path.
[0015] FIGS. 8 and 9 show schematically the magnetic convection
heat circulating pump of the present invention having a fluid
circulation path partly defined by a ring-shaped magnet.
[0016] FIG. 10 is a perspective view of the magnetic convection
heat circulation pump of the present invention having reduced pump
thickness.
[0017] FIG. 11 shows schematically the arrangement of magnets
supported in a yoke member.
BEST MODE FOR CARRYING OUT THE INVENTION
[0018] According to the present invention, one or more magnets are
disposed in the circulation path of a magnetic fluid. Alternatively
part of the fluid circulation path may be defined by one or more
magnets. Preferably, the magnets are plated with nickel or the like
on the surfaces directly contacting the magnetic fluid and the
plated surfaces are coated with a surfactant having the same ionic
charge as the surfactant used for coating the particulate
ferromagnetic material dispersed in the magnetic fluid. The above
treatment allows direct application of the magnetic field to the
magnetic fluid with reduced flow resistance.
[0019] Preferably, a ferromagnetic material having strongly
temperature-dependent saturation magnetization such as a ferrite
comprising manganese and zinc is employed as the particulate
ferromagnetic material of the magnetic fluid. The particulate
ferromagnetic material has an average particle size less than about
10 nm, preferably less than 6 nm, most preferably about 1 nm. The
selection of suitable ferromagnetic material and optimum particle
size contributes to minimum residual magnetization and most
efficient heat circulation by the pump.
[0020] It is also preferable to construct the heat receiving
section and the magnetic pump section from different materials
having mutually different heat conductivity values in association
with a common magnetic flow path.
[0021] Now a few exemplifying embodiments of the present invention
will be described with reference to FIGS. 1-6 of the accompanying
drawings.
[0022] The embodiment shown in FIG. 1 comprises a circulation path
(3) for circulating a magnetic fluid between a heat receiving
section (1) and a heat discharging section (2), and a magnet
assembly comprising a pair of elongated magnets (4,5) centrally
disposed in the circulation path (3). When the magnetic fluid
receives heat in the heat receiving section (1), a temperature
gradient is created between the magnetic fluid retained in the heat
receiving section (1) and the heat discharging section (2) and the
magnetic fluid retained in the heat receiving section (1) having
decreased magnetization is expelled by the magnetic fluid retained
in the heat discharging section (2) having higher magnetization
than the fluid retained in the heat receiving section (1) under the
influence of the magnetic field of the elongated magnet centrally
disposed in the circulation path (3). Thus heat transfer occurs
from the heat receiving section (1) to the heat discharging section
(2) by the magnetic convection.
[0023] In the embodiment shown in FIG. 1, the magnetic force is
directly exerted to the magnetic fluid not only resulting in
efficient circulation of heat but also remarkably decreasing the
effect of leaked magnetic flux to various electronic devices when
used for discharging heat therefrom.
[0024] The magnetic fluid used in the present invention comprises a
dispersion of particulate ferromagnetic material in a suitable
dispersion medium. The particulate ferromagnetic material
preferably has an average particle size less than 30 nm, more
preferably in a range between 1 nm and 10 nm.
[0025] The ferromagnetic material used in the present invention is
preferably comprised of a ferrite compound having highly
temperature-dependent saturation magnetization such as a ferrite
comprising a divalent transition metal.
[0026] The particles of ferromagnetic material preferably have a
coating of an ionic surfactant, i.e. either anionic or cationic
surfactant on their surfaces to impart individual particles with
repulsing force so that the particles may be stably and uniformly
dispersed in a dispersion medium to contribute to decreased effect
of residual magnetization and decreased flow resistance in the
circulation path.
[0027] Preferably, the magnets disposed in or forming part of the
circulation path also have on their surfaces contacting the
magnetic fluid a coating of the same ionic surfactant as the
coating of the ferromagnetic particles. The coating of ionic
surfactant on the surfaces of the magnet also contributes to
decreased effect of residual magnetization and decreased flow
resistance in the circulation path.
[0028] The efficiency of magnetic convection pump may be remarkably
promoted by the use of a ferromagnetic material exhibiting highly
temperature-dependent saturation magnetization. In a preferred
embodiment, a manganese-zinc ferrite of the formula 1/2 Zn 1/2 Mn
Fe.sub.2O.sub.4 is employed. However, other ferrites having
comparable temperature-dependent saturation magnetization may be
used as well.
[0029] The use of a magnetic ionic liquid as the magnetic fluid is
within the scope of the present invention. Typical example of the
magnetic ionic liquid is comprised of ferric oxychloride anion and
1-butyl-3-methylimidazolium cation.
[0030] FIGS. 2-4 show further embodiments of the magnetic
convection circulation pump of the present invention. In the
embodiment shown in FIG. 2, a magnet assembly comprises a plurality
of magnets (4,4b, 5, 5b) connected in series. The magnet assembly
is disposed in the magnetic fluid (3) with the magnet having
stronger magnetic force extending toward the heat receiving
section. In the embodiment shown in FIG. 3, a pair of magnets are
disposed in opposed positions in the circulation path (3). In the
embodiments shown in FIG. 4, a pair of magnets are disposed in the
circulation path (3) at an angle so that the spacing between the
magnet pair is minimum at the ends facing toward the heat receiving
side. By creating the strongest magnetic field on the heat
receiving side in the circulation path (3) as shown, the magnetic
fluid retained in the heat discharging side will be moved to the
heat receiving side more easily.
[0031] In the embodiment shown in FIG. 5, a pair of magnets are
attached to a support member (10) made of ferromagnetic material.
The support member (10) has an inverted U-shape and the pair of
magnets are supported by the legs at opposing positions. This
configuration contributes to the reduction of leakage of magnetic
flux and also to stronger magnetic force between the opposing
magnets.
[0032] The embodiment shown in FIG. 6 is provided with three
circulation paths (7,8,9). The magnet having opposite poles (4,5)
are disposed in the first circulation path (7) in the heat
receiving section (1) to create a magnetic flow path (6). The
magnet may be disposed any one of three circulation paths and the
magnetic flow path (6) may be created on both sides of the magnet.
The magnetic heat pump shown in FIG. 6 operates with fewer volume
of the magnetic fluid than the magnetic heat pump shown in FIG.
1.
[0033] In the embodiment shown in FIG. 7, the heat receiving
section (1) is separated from the heat discharging section (2).
Both section have their own fluid circulation paths which are
connected end-to-end in closed loop with connecting tubings made of
flexible materials. By connecting two sections with flexible
tubings, their relative positions may be changed as desired.
[0034] In the embodiment shown in FIG. 8, the magnetic convection
heat pump comprises a pair of magnet rings (4a,5a) which are
concentrically connected to the end of associated fluid circulation
path as part of connecting conduit (12) between the heat receiving
section (1) and the heat discharging section (2). According to this
embodiment, the heat receiving and heat discharging sections (1,2)
may be constructed by common parts and allows easy connection and
disconnection of circulation path at magnetic connection site (11)
and facilitates filling and withdrawing the magnetic fluid into and
from the fluid circulation path (3).
[0035] The magnet disposed in the fluid circulation path (3) may be
secured by any means, for example, movable engagement into a mating
groove, glueing and the like.
[0036] The heat receiving section (1) and the heat discharging
section (2) are preferably constructed from a material having a
high heat conductivity such as copper, aluminum or graphite. More
preferably, such a material has low magnetic permeability.
[0037] Now still further embodiments of the magnetic convection
heat circulation pump of the present invention will be described
making reference to FIGS. 9-11. The term "magnetic pump (14)
section" as used herein refers to the section in which the magnet
(13) placed in the associated magnetic flow path (6) is located. In
the embodiment shown in FIG. 9, the end portion of the magnetic
flow path (6) on the heat receiving section side is tapered to
prevent reverse flow of the magnetic fluid and the magnet (13) and
the magnetic flow path (6) extend in part into the heat receiving
section (1). Moreover, the heat receiving section (1) and the
magnetic pump section (14) each constructed from a mutually
different material having different heat conductivity are thermally
coupled together.
[0038] In addition, the magnetic flow path (6) and the fluid
circulation path (3) in the heat receiving section (1) is connected
in fluid flow communication to the heat discharging section (2) by
a connecting flexible conduit made of, for example, fluorocarbon
resin. In the heat circulation pump as shown in FIG. 9, heat
inputted in the heat receiving section (1) is directly transferred
to part of the magnetic flow path extending in the heat receiving
section (1) but the heat is transferred only indirectly to the
magnetic pump section (14). Furthermore, since the magnetic pump
section (14) is made of a material having a heat conductivity less
than the material of the heat receiving section (1), the quantity
of heat transferred to the magnetic pump section (14) is not
sufficient to raise the temperature of that section as high as the
temperature of the heat receiving section (1). This creates a
temperature gradient within the area of magnetic flow path (6) and
the magnetic fluid retained in the region of magnetic flow path
having higher temperature is magnetically expelled by the magnetic
fluid retained in the region of magnetic flow path having lower
temperature due to the gradient of the magnitude of saturation
magnetization. Once this has occurred, cold magnetic fluid will
flow into the magnetic pump section (14) from the heat discharging
section (2) to begin with the circulation of magnetic fluid through
the entire heat circulation path (3). In order to create a
temperature gradient sufficient to drive the magnetic fluid by the
magnetic force the heat receiving section (1) and the magnetic pump
section (14) are constructed, for example, from aluminum or like
metallic material and a polymeric material respectively.
[0039] Although not shown in FIG. 9, the direction of magnetization
of the magnet 13 may be either in the longitudinal direction or the
direction perpendicular thereto. In case of longitudinal
magnetization direction, for example, the location where the
temperature gradient occurs will be shifted from the point where
the magnetic field is strongest to the central part of the magnet
where the magnetic field is weakest as the heat input decreases.
Accordingly, it is envisaged to have a magnetic convection heat
circulation pump for maintaining the temperature of a heat
generating parts at constant by using a magnet adapted for such
applications.
[0040] Also not shown in the drawings, the fluid circulation path
preferably has at least partially on the surfaces contacting the
magnetic fluid a coating of either an oil repellent material such
as SITOP sold by Asahi Glass or an ionic surfactant of the same
type used for coating the particulate ferromagnetic material of the
magnetic fluid. For example, a cationic surfactant is used for
coating both the circulation path and the particulate ferromagnetic
material. The coating of the fluid circulation path contributes to
decreased shear stress of the path and also to the prevention of
agglomeration of particulate ferromagnetic material.
[0041] FIG. 9 illustrates an embodiment of the magnetic heat pump
of the present invention having a magnetic flow path (6) common
between the heat receiving section (1) and the magnetic pump
section (14). However, the magnetic flow path (6) does not
necessarily require to be common when the heat receiving section
(1) is thermally couple to the magnetic pump section (14) using a
metal having good thermal conductivity.
[0042] In the embodiment shown in FIG. 10, the heat receiving
section (1) and the magnetic pump section (14) are constructed from
the same material having the same heat conductivity. However, the
heat receiving section (1) has an overall thickness greater than
that of the magnetic pump section (14). Accordingly, the heat
receiving section functions as a heat sink and reduces the quantity
of heat to be transferred to the magnetic pump section (14) to
create a remarkable temperature gradient in the magnetic flow path
(6) in a similar manner when the both sections are constructed from
different materials having mutually different heat
conductivity.
[0043] In the embodiment shown in FIG. 11, a pair of magnets (13)
having opposite polarity are supported by a yoke member (15) in
diametrically opposing positions to strengthen the magnetic field
therebetween. The plane not occupied by the magnets serves as a
magnetic flow path (6) and the magnetic fluid can flow thereon
without any disturbance. The leakage of magnetic flux may greatly
reduced by this structure.
[0044] The magnetic heat pump according to the present invention
can convey a large quantity of heat per unit area. The heat pump
may be constructed in small sizes suitable for mounting on a
variety of electric and electronic instruments. Therefore, it finds
use in a cooling system for instruments having a high power
consumption density such as CPU, laser diode optics and other
electronic devices.
[0045] The magnetic heat pump according to the present invention
operate without need for power supply. Therefore, it finds use in
heat dissipation of self-operated instruments, utilization of solar
heat energy, and recycling waste heat energy.
[0046] The magnetic heat pump according to the present invention
utilizes essentially non-volatile magnetic fluid. Because of this,
it may find use in heat transfer in space stations and
satellites.
* * * * *