U.S. patent application number 11/858174 was filed with the patent office on 2008-07-31 for water cooling apparatus.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Katsumi Hisano, Hideo Iwasaki, Tomonao Takamatsu.
Application Number | 20080179046 11/858174 |
Document ID | / |
Family ID | 39666639 |
Filed Date | 2008-07-31 |
United States Patent
Application |
20080179046 |
Kind Code |
A1 |
Hisano; Katsumi ; et
al. |
July 31, 2008 |
WATER COOLING APPARATUS
Abstract
In a cooling apparatus, a heating element is thermally connected
to a container that defines a first channel through which a coolant
flows. A porous block having a large number of pores is
accommodated in the container so as to block the first channel. The
porous block has second channels formed in the porous block along
the first channel and each having an opening on an upstream side of
the first channel. Further, third channels are formed in the porous
block along the first channel, each have an opening on an upstream
side of the first channel, and communicate with the second channels
via the pores.
Inventors: |
Hisano; Katsumi;
(Matsudo-shi, JP) ; Iwasaki; Hideo; (Kawasaki-shi,
JP) ; Takamatsu; Tomonao; (Tokyo, JP) |
Correspondence
Address: |
AMIN, TUROCY & CALVIN, LLP
1900 EAST 9TH STREET, NATIONAL CITY CENTER, 24TH FLOOR,
CLEVELAND
OH
44114
US
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
39666639 |
Appl. No.: |
11/858174 |
Filed: |
September 20, 2007 |
Current U.S.
Class: |
165/104.11 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 2924/0002 20130101; F28D 15/00 20130101; F28F 13/003 20130101;
H01L 2924/00 20130101 |
Class at
Publication: |
165/104.11 |
International
Class: |
F28D 15/00 20060101
F28D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2007 |
JP |
2007-021125 |
Claims
1. A cooling apparatus comprising: a heating element; a container
thermally connected to the heating element to define a first
channel through which a coolant flows; a porous block having a
large number of pores formed in the container so as to block the
first channel; second channels formed in the porous block along the
first channel and each having an opening on the upstream side of
the first channel; and third channels formed in the porous block
along the first channel and each having an opening on an upstream
side of the first channel, the third channel communicating with the
second channels via the pores.
2. The apparatus according to claim 1, wherein the porous block is
made of an anisotropic porous material, and the pores are formed in
the anisotropic porous material so as to extend in a direction
crossing the first channel, and the second channels and the third
channels are substantially arranged in a grid in a cross section of
the first channel.
3. The apparatus according to claim 1, wherein the porous block is
made of an anisotropic porous material, and the pores are formed in
the anisotropic porous material so as to extend in a direction
crossing the first channel, and the second channels and the third
channels are substantially arranged in a zigzag in a cross section
of the first channel.
4. The apparatus according to claim 1, wherein each of the pores
has a diameter of several .mu.m to tens of .mu.m.
5. The apparatus according to claim 1, wherein each of the second
and third channels has a diameter of 100 .mu.m to 1000 .mu.m.
6. The apparatus according to claim 1, wherein the second and third
channels have a first diameter at a side of the heating element and
a second diameter at a opposite side of the heating element, the
second diameter being larger than the first diameter.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application No. 2007-021125,
filed Jan. 31, 2007, the entire contents of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a cooling apparatus, and in
particular, to a cooling apparatus having a porous block.
[0004] 2. Description of the Related Art
[0005] A year-on-year increase in the amount of heat generated by
semiconductor devices has been making it increasingly difficult to
cool the semiconductor devices. Air cooling apparatuses are
conventionally used to cool the semiconductor devices. However,
owing to the insufficient cooling capacity of the air cooling
apparatus, liquid cooling apparatuses using an antifreeze solution
or the like as a coolant have been developed. The liquid cooling
apparatus using the antifreeze solution or the like as a coolant
employs a technique for enhancing heat transfer from a solid wall
surface to the coolant to cool semiconductor devices. One type of
such a technique is a cooling apparatus utilizing micro-channels,
which was described by D. B. Tuckerman in the early 1980s, in D. B.
Tuckerman, R. F. Pease, High-Performance Heat Sinking for VLSI,
1981, IEEE EDL-2(5), pp. 126-129. In this cooling apparatus, a
semiconductor device as a heating element is placed on a heat
receiving block to which heat from the semiconductor element is
transferred. A channel is defined in the heat receiving block such
that a coolant can flow through the channel. Comb-shaped fins
formed by etching Si or the like are arranged parallel to one
another in the channel. In this structure, micro-channels of width
several tens of micrometers to several hundred micrometers are
defined among the fins such that the coolant can flow through the
micro-channels. It is known that in such a structure, narrower
channels reduce the thickness of a temperature boundary layer to
provide improved heat transfer performance.
[0006] On the other hand, the reduced thickness of the thermal
boundary layer is associated with the reduced thickness of a
velocity boundary layer. Accordingly, it can be easily expected
that the improved heat transfer performance based on the
miniaturized channels may increase pressure loss of the
coolant.
[0007] It is also well known that the thermal boundary layer
becomes progressively thicker with a downstream distance from the
inlets of the channels. Thus, the increased length of the channels
increases heat transfer area but unfortunately fails to
correspondingly improve the heat transfer performance.
[0008] In the design of the cooling apparatus, the width or length
of the channels is determined taking into account the tradeoff
between the heat transfer performance and the pressure loss. If
very high heat transfer performance is demanded, practical design
solutions may not be obtained from the above structure only by
dimensional adjustments. That is, increased pressure loss results
from an increase in the length of the channels in an attempt to
increase the contact area between the coolant and the solid wall
surface. However, the heat transfer performance is not improved in
proportion to the increase in the channel length. Further, a
reduction in the length of the channels in an attempt to reduce the
pressure loss may directly decrease heat transfer area.
[0009] As a method for solving this problem, a structure has been
proposed in which serpentine fins are arranged in the channels.
This structure is adopted for a heat exchanger disclosed in JPA
2005-123496 (KOKAI). Further, instead of the cooling apparatus,
some filters have adopted structures similar to the serpentine
fins. The fins comprising plates with a large number of
through-holes are expected to improve the heat transfer performance
of the micro-channels at the through-hole portions. The serpentine
of the plates increases the area of the plates with the
through-holes in the cooling apparatus, that is, the number of
through-holes, to ensure both improved heat transfer performance
and reduced pressure loss. However, with the structure adopting the
serpentine fins, a reduction in the diameter of the through-holes
and an increase in the flow rate of the coolant, both carried out
to improve the heat transfer performance, may increase the
difference in pressure between the front and back surfaces of the
thin plate. This may prevent the fins from being made sufficiently
strong.
[0010] Another problem is how to mount the thin plates for the fins
on the wall surfaces of the channels. For example, the channels in
which the serpentine fins are provided are each formed to be a
substantially rectangular cavity enclosed by six wall surfaces.
With this cooling structure, the cooling performance is intended to
be improved by reducing the thickness of the walls defining the
cavity portion to increase the number of turnups. Thus, in design,
the walls are desirably thinner. However, in actuality, the reduced
thickness of the walls is expected to make it difficult to mount
the end surfaces of the walls on a container.
[0011] As described above, with the cooling apparatus using the
micro-channels, disclosed in D. B. Tuckerman, R. F. Pease,
High-Performance Heat Sinking for VLSI, 1981, IEEE EDL-2(5), pp.
126-129, the improved heat transfer performance based on the
miniaturized channels may worsen the pressure loss of the coolant.
Another problem with this cooling apparatus is that the increase
length of the channels increases the heat transfer area but fails
to correspondingly improve the heat transfer performance.
[0012] With the heat exchanger having the serpentine fins,
disclosed in JPA 2005-123496 (KOKAI), a reduction in the diameter
of the through-holes and an increase in the flow rate of the
coolant, both carried out to improve the heat transfer performance,
may prevent the fins from being made sufficiently strong. Another
problem is how to mount the thin plates for the fins on the wall
surfaces of the channels.
BRIEF SUMMARY OF THE INVENTION
[0013] According to an aspect of the present invention provides a
cooling apparatus comprising:
[0014] a heating element;
[0015] a container thermally connected to the heating element to
define a first channel through which a coolant flows;
[0016] a porous block having a large number of pores formed in the
container so as to block the first channel;
[0017] second channels formed in the porous block along the first
channel and each having an opening on the upstream side of the
first channel; and
[0018] third channel formed in the porous block along the first
channel and each having an opening on the upstream side of the
first channel, the third channel communicating with the second
channels via the pores.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0019] FIG. 1 is a sectional view schematically showing a cooling
apparatus in accordance with an embodiment;
[0020] FIG. 2 is a sectional view of the cooling apparatus shown in
FIG. 1, the view being taken along line II-II in FIG. 1;
[0021] FIG. 3A is a perspective view showing a fin block
incorporated into the cooling apparatus shown in FIG. 1 as viewed
from a downstream side of a flow passage for a coolant;
[0022] FIG. 3B is a perspective view showing the fin block
incorporated into the cooling apparatus shown in FIG. 1 as viewed
from the upstream side of the flow passage for the coolant;
[0023] FIG. 4 is a sectional view schematically showing a fin block
incorporated into a cooling apparatus in accordance with another
embodiment;
[0024] FIG. 5 is a sectional view schematically showing a fin block
incorporated into a cooling apparatus in accordance with yet
another embodiment; and
[0025] FIG. 6 is a sectional view schematically showing a cooling
apparatus in accordance with still another embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0026] A cooling apparatus in accordance with an embodiment of the
present invention will be described below with reference to the
drawings as required.
[0027] FIGS. 1 and 2 show a cooling apparatus in accordance with
the embodiment of the present invention. FIG. 1 is a sectional view
of a cooling apparatus taken along a coolant flow passage. FIG. 2
shows a cross section of the cooling apparatus shown in FIG. 1, the
cross section being taken along line II-II in FIG. 1.
[0028] In the cooling apparatus in FIGS. 1 and 2, a heating element
1 is mounted on a wall surface of a heat receiving block 2 having
an external shape substantially like a rectangular parallelepiped.
A channel 3 is formed in the heat receiving block 2. As a coolant
4, water or an antifreeze solution is allowed to flow through the
channel 3. A fin block 5 is mounted on an inner surface of the heat
receiving block 2 in proximity to the wall surface of the heat
receiving block 2 on which the heating element 1 is mounted. Heat
generated by the heating element 1 is transmitted to the coolant
via the fin block 5 and discharged to the exterior of the heat
receiving block 2 as the coolant flows through the channel.
[0029] The fin block 5 is made of an anisotropic porous material
with a large number of pores 6. The pores 6 penetrate the fin block
5 and have a diameter of several .mu.m to several tens of .mu.m.
The pores 6 are formed in the fin block 5 so as to extend through
the block 5 along a Y direction in FIGS. 1 and 2. The fin block 5
has an upstream side surface 5a that faces the upstream side of the
coolant channel 3 and a downstream side surface 5b that faces the
downstream side of the coolant channel 3. The upstream side surface
5a and the downstream side surface 5b are located opposite each
other.
[0030] A plurality of coolant introduction holes 7 and a plurality
of coolant discharge holes 8 are formed in a grid in the YZ surface
of each of the upstream side surface 5a and the downstream side
surface 5b. In the arrangement shown in FIGS. 1 and 2, the coolant
introduction holes 7 and the coolant discharge holes 8 are
alternately arranged along the Y direction. The coolant
introduction holes 7 and the coolant discharge holes 8 are arranged
in respective lines along the Z direction. As shown in FIGS. 3A and
3B, the coolant introduction holes 7 and the coolant discharge
holes 8 have a diameter of, for example, 100 to 1,000 .mu.m, which
is sufficiently larger than that of the pores 6. The coolant
introduction holes 7 and the coolant discharge holes 8 are arranged
to cross the pores 6, for example, to extend substantially
orthogonally to the pores 6. The coolant introduction holes 7 and
the coolant discharge holes 8 are further arranged so as not to
cross one another or communicate directly with one another. The
coolant introduction holes 7 and the coolant discharge holes 8
extend through the fin block 5 so that the inner diameter of each
hole decreases progressively. In FIGS. 3A and 3B, the direction in
which the pores 6 extend is shown by arrow A, and the direction in
which the coolant 4 flows is shown by arrow B. The coolant
introduction holes 7 extend from the upstream side surface 5a along
arrow B and do not penetrate the fin block 5 or open in the
downstream side surface 5b. The coolant introduction holes 7
communicate with the large number of pores 6, crossing the coolant
introduction holes 7, and communicate with the coolant discharge
holes 8, with which the large number of pores 6 communicate.
Similarly, the coolant discharge holes 8 extend from the downstream
side surface 5b in a direction opposite to that of arrow B and do
not penetrate the fin block 5 or open in the upstream side surface
5a. The coolant discharge holes 8 communicate with the large number
of pores 6, crossing the coolant discharge holes 8, and communicate
with the coolant introduction holes 7, with which the large number
of pores 6 communicate. The coolant introduction holes 7 and the
coolant discharge holes 8 are further arranged so as not to cross
one another or communicate directly with one another. Consequently,
a coolant flowing into the fin block 5 through the upstream side
surface 5a flows out through the downstream side surface 5b of the
fin block 5 via the coolant introduction holes 7, the pores 6, and
the coolant discharge holes 8.
[0031] The anisotropic porous material as the fin block 5 is
produced by, for example, one of the methods shown in Jpn. Pat.
Appln. No. P2005-322629 and Jpn. Pat. Appln. No. P2006-121730. That
is, molten metal is poured into a mold in which carbon fibers are
arranged parallel to one another. After the metal is solidified,
the carbon fibers are oxidized and removed to form the pores 6; the
material thus becomes porous. With the carbon fibers remaining in
the solidified metal, the coolant introduction holes 7 and the
coolant discharge ports 8 are formed in the fin block 5 by
machining. The carbon fibers are then removed. This manufacturing
method enables the production of a cooling apparatus that prevents
the pores from being crushed during machining to avoid obstructing
the flow of the coolant.
[0032] The coolant flows from the coolant introduction holes 7
through the pores 6 and flows out from the coolant discharge holes
8. As previously described, the inner walls of the small-diameter
pores 6 contribute to improving the heat transfer performance.
Further, the possible pressure loss between the inlet and outlet of
each pore 6 is imposed on the inner walls of the corresponding
coolant introduction holes 7 and coolant discharge holes 8, which
constitute curved surfaces. Accordingly, the increased flow rate of
the coolant and the reduced diameter of the pores make it possible
to maintain sufficient strength even with an increase in pressure
loss.
[0033] Moreover, the entire bottom surface of the fin block 5 can
be utilized to mount the fin block 5 on the wall of the channel in
the heat receiving block. This facilitates production.
[0034] FIG. 4 is a sectional view showing the fin block 5 in
accordance with another embodiment of the present invention. As
shown in FIG. 4, the coolant introduction holes 7 and the coolant
discharge holes 8 are arranged in a zigzag. Two lines of coolant
introduction holes 7 and two lines of the coolant discharge holes 8
are alternately formed in each of the upstream side surface 5a and
the downstream side surface 5b. It is assumed that the surface
shown in FIG. 4 is the upstream side surface 5a. Then, given that
in the first line from the left end of the drawing, one line of the
three coolant introduction holes 7 are formed, in the third line,
one line of the coolant discharge holes 8 are formed. In the fifth
line, one line of the three coolant introduction holes 7 are
formed, and in the seventh line, one line of the coolant discharge
holes 8 are formed. Further, given that in the second row from the
left end of the drawing, the coolant introduction channel 7 and the
coolant discharge channel 8 are formed, in both the fourth and
sixth lines, the coolant introduction channel 7 and the coolant
discharge channel 8 are formed. Inside the fin block 5, the pores 6
are arranged so that their axes extend in a horizontal direction (Y
direction). When the coolant introduction holes 7 and discharge
holes 8 are arranged in a grid as shown in FIGS. 1 and 2, that is,
the coolant introduction holes 7 and discharge holes 8 are arranged
in respective lines in the Y direction, the coolant does not flow
in some of the pores 6. However, when the coolant introduction
holes 7 and discharge holes 8 are arranged in a zigzag as shown in
FIG. 4, the coolant flows as shown by arrow 4 in FIG. 4. This makes
it possible to improve the utilization of the pores and thus the
cooling performance.
[0035] FIG. 5 is a sectional view showing the fin block 5 in
accordance with another embodiment of the present invention. The
fin block 5 shown in FIGS. 1 and 2 is made of the anisotropic
porous member having the pores extending linearly inside the
material in the Y direction. In contrast, the fin block 5 shown in
FIG. 5 is made of a porous member having pores extending in a
plurality of directions in the YZ surface. The coolant is allowed
to flow in the respective axial directions. Since the pores do not
extend in any single direction inside the fin block 5, the coolant
flows between the coolant introduction holes 7 and the coolant
discharge holes 8 wherever the coolant introduction holes and
discharge holes are arranged in the YZ surface. To clarify the
arrangement of the coolant introduction holes 7 and the arrangement
of the coolant discharge holes 8, the coolant discharge holes 8 are
marked with reference character x so as to be distinguished from
the coolant introduction holes 7.
[0036] FIG. 6 shows a cooling apparatus in accordance with another
embodiment of the present invention. The coolant introduction holes
7 and discharge holes 8 formed close to the heating element 1 are
set to have a smaller diameter, whereas the coolant introduction
holes 7 and discharge holes 8 formed away from the heating element
1 are set to have a smaller diameter. In the thus configured
cooling apparatus, the inner surfaces of the pores 6 have a larger
surface area in an area in the fin block 5 which is closer to the
heating element 1 and which thus has a higher temperature. This
improves radiating performance.
[0037] As described above, the cooling apparatus in accordance with
the present invention makes it possible to effectively cool a
heating element with a large heating value.
[0038] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *