Loop type heat pipe

Details Loop type heat pipe Loop type heat pipe

2001-02-05

2002-09-17

Wilson, Gregory (Department: 3749)

Liquid heaters and vaporizers

Wick

C165S104260

Reexamination Certificate

active

06450132

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a loop type heat pipe which can be used as a space, industrial or domestic heat transport apparatus.
2. Description of the Related Art
Among loop type heat pipes which can be used as a space, industrial or domestic heat transport apparatus, a pipe having the structure which is disclosed in, e.g., Japanese Patent Laid-Open Publication No. Hei 10-246583 has been widely used.
FIG. 6
shows the structure of a conventional loop type heat pipe. In
FIG. 6
, the loop type heat pipe has such a configuration that an evaporator
1
for applying heat and a condenser
20
for radiating the applied heat are connected by a vapor pipe
9
and a liquid pipe
11
. A working fluid is sealed in the evaporator
1
, the vapor pipe
9
, the condenser
20
and the heat pipe
11
. Vapor of the working fluid passes through the vapor pipe
9
, and on the other hand, the liquid of the working fluid passes through the liquid pipe
11
. It is to be noted that since evaporation latent heat is utilized for heat transport, a fluid having excellent vaporization properties is generally selected as the working fluid. For example, ammonia or alcohol is used as the fluid having the excellent vaporization properties.
Giving a full detail, the evaporator
1
is accommodated in an evaporator container
4
. A liquid bank
6
for storing the working fluid therein is provided inside the evaporator
1
, and both ends of the liquid band
6
are connected to a liquid supply pipe
17
, which is connected to the liquid pipe
11
to supply a liquid
13
a
of the working fluid, and the vapor pipe
9
, respectively. Furthermore, a second wick
7
is provided along the outer periphery of the liquid bank
6
, and a first wick
2
is provided along the outer periphery of the second wick
7
. The second wick
7
transports the liquid of the working fluid to the inner peripheral surface of the first wick
2
by capillary force, and the first wick
2
transports the liquid of the working fluid to the vicinity of the outer periphery of the evaporator
1
by the capillary force.
The vapor from the evaporator
1
passes through the vapor pipe
9
as indicated by an arrow
14
, and the vapor
13
b
of the working fluid is supplied to the condenser
20
, in which heat is released as indicated by arrows
21
. The vapor
13
b
becomes the liquid
13
a
of the working fluid, and this liquid
13
a
passes to the liquid bank
6
through the liquid pipe
11
as indicated by an arrow
16
.
FIG. 7
is views showing the cross section (FIG.
7
(A)) vertical to the radial direction of the evaporator
1
and the cross section (FIG.
7
(B)) vertical to the axial direction of the same in order to illustrate the structure of the evaporator
1
in
FIG. 6
in more detail. In FIGS.
7
(A) and
7
(B), the first wick
2
is provided inside the evaporator container
4
forming the outline of the evaporator
1
through a plurality of projecting portions
26
. Further, the second wick
7
is arranged on the inner peripheral surface of the first wick
2
. A vapor flow path
25
is provided between the projecting portions
26
, and the vapor
13
b
of the working fluid flows through the vapor flow path
25
.
It is to be noted that since the first wick
2
and second wick
7
must transport the liquid
13
a
of the working fluid by the capillary force, a porous body having a pore diameter of approximately 0.5 to several tens of &mgr;m is generally used. The pore diameter of the first wick
2
is smaller than that of the second wick
7
. The first wick
2
has a function for circulating the working fluid in the loop type heat pipe by generating the high capillary force, and the second wick
7
has a function for distributing the liquid
13
a
of the working fluid in the circumferential direction of the first wick
2
.
The second wick
7
does not, therefore, have as high a capillary force as the first wick
2
but has small flow path resistance. Thus, the second wick
7
can transport a large amount of the liquid
13
a
of the working fluid against the weight. A liquid bank
6
capable of storing the liquid
13
a
of the working fluid is provided on the inner periphery of the second wick
7
, and the liquid of the working fluid is supplied from the liquid pipe
11
through the liquid supply pipe
17
. Further, a vapor pipe
9
for evacuating the vapor
13
b
of the working fluid in the evaporator
1
is provided in the evaporator container
4
.
The principle of operation of the conventional loop type heat pipe having the above structure will now be described hereinafter.
In
FIG. 7
, the liquid
13
a
of the working fluid stored in the liquid bank
6
is first transported in the circumferential direction by the capillary force of the second wick
7
as indicated by the arrow
30
. Thereafter, the liquid
13
a
is transported in the radial direction of the first wick
2
by the capillary force of the first wick
2
which is arranged to be in contact with the second wick
7
. The flow of heat to be applied at this time is indicated by an arrow. That is, when heat is applied from the outer periphery of the evaporator
1
, the applied heat is conducted to the first wick
2
through the peripheral projecting portions
26
arranged between the first wick
2
and the evaporator container
4
. The liquid
13
a
of the working fluid is evaporated to become the vapor
13
b
of the working fluid on the outer peripheral surface of the first wick
2
by the conducted heat. The generated vapor
13
b
flows in the vapor flow paths
25
along the direction indicated by an arrow
41
to enter the vapor pipe
9
.
As shown in
FIG. 6
, the vapor
13
b
of the working fluid then flows into the condenser
20
. However, since heat radiation is performed in the condenser
20
along the direction indicated by an arrow
21
, the inside of the condenser
20
is maintained at a temperature lower than that of the vapor
13
b
of the working fluid. The vapor
13
b
of the working fluid is thus condensed and phase-changed again become the vapor
13
a
of the working fluid. At this time, heat radiation is carried out. Moreover, the phase-changed liquid
13
a
of the working fluid flows in the liquid pipe
11
as indicated by an arrow
16
and is again supplied into the liquid bank
6
through the liquid supply pipe
17
.
By repeating the above-described cycle, heat can be transported from the evaporator
1
to the condenser
20
.
In the above-mentioned conventional loop type heat pipe, in order to transport the liquid
13
a
of the working fluid to the inner peripheral surface of the first wick
2
, the second wick
7
must be used. As the second wick
7
, one having a pore diameter larger than that of the first wick
2
is used. Therefore, two types of wick are required, and the two-layer configuration must be employed, thereby leading to complicated manufacture.
Further, as to the liquid existing in the porous body such as a wick, the bubble nucleus which can be the nucleus of boiling generally becomes larger as the pore diameter of the porous body increases. When heated, boiling is apt to occur with a small quantity of heating. Since the second wick
7
has a large pore diameter, it has such a problem that the liquid
13
a
of the working fluid in the wick is readily boiled by applying heat. Therefore, when the liquid
13
a
of the working fluid is boiled in the second wick
7
, the liquid
13
a
of the working fluid can not be supplied to the entire inner peripheral surface of the first wick
2
and the working fluid in the loop type heat pipe can not be thereby circulated.
SUMMARY OF THE INVENTION
In order to eliminate the above-described problems, it is an object of the present invention to provide a loop type heat pipe which can be readily manufactured without providing the double structure of the wick
2
.
It is another object of the present invention to provide a loop type heat pipe by which the liquid of the working fluid is not boiled in the second wick even if a quantity of heating with respect

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