JP2001068611A - Boiling cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire a boiling cooler capable of preventing dryout of boiling surface even for increased vapor generation. SOLUTION: A refrigerant bath comprising a thin box-shaped vessel and an outside board 2B for closing the opening face of the vessel is externably formed in a thin rectangular parallelpiped. A plurality of ribs 10 are formed on the outside board 2B by extrusion forming. The length of each rib is formed a little longer than the vertical width of boiling surface of the refrigerant vessel. A path width (d) of a refrigerant path 6a formed by the ribs 10 is set less than twice (desirably 1 mm or less) the Laplace length. This makes the outer diameter of bubbles larger than the path width (d) on the occasion of boiling and vaporization of the liquid refrigerant in the refrigerant vessel caused by the heat generated from CPU and causes upstream of the bubbles through each refrigerant path 6a to raise the liquid refrigerant by bubbles and the liquid surface of each refrigerant path 6a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiling cooler for cooling a heating element by the action of boiling and condensing refrigerant.

[0002]

2. Description of the Related Art Conventionally, there is a boiling cooler for cooling a heating element such as an electronic device. This boiling cooler
It is composed of a refrigerant tank that stores liquid refrigerant, and a heat radiating unit that radiates heat by exchanging heat with the external fluid for refrigerant vapor that has boiled by receiving heat from the heating element in the refrigerant tank. In order to reduce the amount of filled refrigerant, a thinned refrigerant tank is known.

[0003]

However, as the thickness of the refrigerant tank is reduced, the amount of vapor generated in the refrigerant tank increases (for example, when the heat generation density is large). There is a problem in that the so-called dry-out in which the ratio decreases, the liquid level decreases, and the temperature of the boiling surface rapidly rises, is likely to occur. SUMMARY OF THE INVENTION The present invention has been made based on the above circumstances, and an object of the present invention is to provide a boiling cooler which can prevent dry out of a boiling surface even when an amount of generated steam increases.

[0004]

Means for Solving the Problems (1) A refrigerant tank comprises a plurality of refrigerant tanks extending at least vertically on a boiling surface of a refrigerant chamber (a surface on which a refrigerant boils by receiving heat from a heating element). A passage portion is formed, and the passage width of the passage portion is set to twice or less the Laplace length. According to this configuration, the size of the bubble of the refrigerant vapor that has been boiled by the heat of the heating element in the refrigerant chamber becomes larger than the passage width of the passage portion, so that the liquid refrigerant is lifted when the bubble rises in the passage portion. Is generated. Thus, even when the amount of generated steam increases, the decrease in the liquid level can be suppressed, and the liquid refrigerant can be supplied to the boiling surface of the refrigerant chamber.

The length of the plurality of passages in the vertical direction is equal to or longer than the length of the heating element. In this case, the liquid refrigerant can be supplied to the upper portion of the boiling surface with the rise of the bubbles, so that dry-out does not occur even at the upper portion of the boiling surface.

The coolant tank has an outer wall forming one surface or the other surface, and the inner wall of the outer wall defines a space between adjacent passages. A plurality of ribs are provided integrally. In this configuration, the heat transfer area of the boiling surface can be enlarged by the rib, and the pressure resistance of the refrigerant tank can be improved.

(Means of Claim 4) The outer wall having a plurality of ribs is made of extruded material. In this case, the ribs can be easily formed by the extruded material. For example, the cost can be reduced compared to a method of forming the ribs by cutting, or a method of forming the ribs separately and joining them to the outer wall. Can be.

(Embodiment 5) The boiling cooler described in claims 1 to 4 cools a computer chip (eg, CPU) disposed on a printed circuit board as a heating element. In this case, since the heat radiating portion is provided on the other surface of the coolant tank, the heat radiating portion does not interfere with the printed circuit board.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 2 is a perspective view of the boiling cooler 1. As shown in FIG. 2, the boiling cooler 1 of the present embodiment has a refrigerant tank 2 for storing therein a liquid refrigerant (for example, water, alcohol, fluorocarbon, chlorofluorocarbon, etc.), and heat generated by the heating element in the refrigerant tank 2. The refrigerant vapor that has boiled in response to an external fluid (for example, outside air)
And a heat radiating unit 3 that is liquefied by heat exchange with
Manufactured by integral brazing.

A) The refrigerant tank 2 includes a box-shaped thin container 2A,
An outer wall plate 2B for closing the opening surface of the thin container 2A is provided, and the outer shape is provided in a thin rectangular parallelepiped. Thin container 2
A and the outer wall plate 2B are both made of a metal material having excellent thermal conductivity (for example, aluminum). This refrigerant tank 2
Is used in a substantially upright posture as shown in FIG. 3, and one surface in the thickness direction comes into contact with a heat-dissipating surface of the CPU 4 as a heating element, and bolts are attached to the printed circuit board 5 on which the CPU 4 is installed. And so on.

[0011] As shown in FIG.
A refrigerant chamber 6, a set of header connection ports 7, a liquid return passage 8, a refrigerant injection section 9, and the like are formed. The refrigerant chamber 6 has a CPU
The space for storing the liquid refrigerant corresponding to the mounting portion 4 has a groove structure G (see FIG. 1) formed in a groove shape by a plurality of ribs 10 provided on the outer wall plate 2B. In addition, the front end surface in the height direction of the rib 10 is brought into contact with and joined to the inner side surface of the thin container 2 </ b> A, so that the adjacent rib 10 is formed.
A refrigerant passage 6a is formed between them. Header connection port 7
Is a space for assembling a header, which will be described later, is provided on both upper sides of the refrigerant chamber 6, and has the other surface 2 a of the refrigerant tank 2.
It is open to. In addition, one header connection port 7 shown in FIG. 4 communicates with the upper side of the refrigerant chamber 6 (each refrigerant passage 6 a), and the other header connection port (not shown) through the liquid return path 8. And leads to a lower side of the refrigerant chamber 6 (each refrigerant passage 6a).

The liquid return passage 8 is a passage for returning the condensed liquid liquefied in the heat radiating section 3 to the refrigerant chamber 6, and is provided adjacent to one side of the refrigerant chamber 6, and has a passage shape downward from the other header connection port. And leads to a lower portion of the refrigerant chamber 6 (each refrigerant passage 6a). The refrigerant injection section 9 is a connection port to which the injection pipe 11 is connected, and is provided below one header connection port 7 and communicates with the refrigerant chamber 6. In addition, the refrigerant is injected to a substantially upper end position of the refrigerant chamber 6 (below the header connection port 7).

Here, the groove structure G will be described. As shown in FIG. 5, the outer wall plate 2B is integrally provided with a plurality of pillars 10A at a predetermined interval by extrusion molding, and thereafter, the both ends in the longitudinal direction of each pillar 10A are fixed by a predetermined length. The rib 10 is formed by removing the rib. FIG. 5A is a perspective view of the outer wall plate 2B, and FIG.
Is a plan view of the outer wall plate 2B. However, the length of each rib 10 is set slightly longer than the vertical width of the boiling surface (equivalent to the length of the heating element in this embodiment) indicated by the broken line in FIG.

The passage width d (see FIG. 1) of the refrigerant passage 6a formed by the rib 10 is set to twice or less (preferably 1 _mm or less) the Laplace length defined by the following equation. . Laplace length = {σ / g (ρ ₁ −ρ ₂ )} σ: surface tension of liquid refrigerant, ρ ₁ : density of liquid refrigerant, ρ ₂ : density of vapor refrigerant, g: gravitational acceleration When the operating temperature (refrigerant temperature) is different, the values of σ, ρ ₁ , and ρ ₂ fluctuate. Therefore, as shown in FIG. 6, the Laplace length is set smaller as the operating temperature increases. You.

B) The heat dissipating portion 3 is composed of a set of headers 12 and a heat dissipating core (a heat dissipating tube 13 and a heat dissipating fin 14). During operation, an external fluid is introduced via the duct 15 (see FIG. 3). It is assumed that the external fluid introduced into the heat radiating section 3 flows upward from below in FIG. 2 by a cooling fan (not shown). A set of headers 12
Is a vapor-side header 12A into which refrigerant vapor boiled by receiving heat from the CPU 4 in the refrigerant tank 2 flows, and a liquid-side header 12A into which condensed liquid liquefied in each radiation tube 13 of the radiation core flows.
B, one end of each in the longitudinal direction is inserted into the inside of the refrigerant tank 2 from the header connection port 7 opened on the other surface 2 a of the refrigerant tank 2, and is assembled in a substantially vertical direction with respect to the refrigerant tank 2. .

The heat radiation core includes a plurality of heat radiation tubes 13.
And the heat radiation fins 1 interposed between the heat radiation tubes 13
And 4. The heat radiation tube 13 is formed of a metal material (for example, aluminum) having excellent thermal conductivity, and is provided in a flat tube shape having a thickness smaller than a width of an outer surface with which the heat radiation fin 14 contacts. One end of each of the heat radiation tubes 13 is connected to the vapor-side header 12A, and the other end is connected to the liquid-side header 12B. The heat-radiation tubes 13 are arranged side by side at a certain interval between the vapor-side header 12A and the liquid-side header 12B. Has been established. The radiating fins 14 are formed by alternately bending thin metal plates (for example, aluminum plates) having excellent thermal conductivity into a wavy shape, and are brazed to the outer surface of the radiating tube 13.

Next, the operation of this embodiment will be described. The liquid refrigerant stored in the refrigerant chamber 6 receives heat from the CPU 4, evaporates and evaporates, and rises as bubbles in the refrigerant passages 6 a of the refrigerant chamber 6. At this time, since the passage width d of each refrigerant passage 6a defined by the ribs 10 is set to be equal to or less than twice the Laplace length, the outer diameter of the bubble becomes larger than the passage width d. As a result, since the refrigerant passage 6a is closed by the bubble, when the bubble rises in the refrigerant passage 6a, the liquid refrigerant is lifted by the bubble, so that the liquid level of each refrigerant passage 6a rises (see FIG. 7). .

The refrigerant vapor ascending each refrigerant passage 6a and entering the vapor side header 12A from the refrigerant chamber 6 flows from the vapor side header 12A to each heat radiation tube 13, and
3, is cooled by the external fluid and condenses inside the heat radiation tube 13. The condensed refrigerant becomes droplets and is pushed down to the liquid header 12B.
B flows back to the refrigerant chamber 6 through the liquid return passage 8 in the refrigerant tank 2. The flow of the refrigerant in this operation is shown by arrows in FIG.

(Effect of the First Embodiment) In the boiling cooler 1 of the present embodiment, a groove structure G is provided on the boiling surface of the refrigerant chamber 6, and the passage width d of the groove structure G is twice or less of the Laplace length. As a result, the size of the bubbles rising in each refrigerant passage 6a becomes larger than the passage width d. As a result, the liquid refrigerant is lifted with the rise of the bubbles, so that the liquid surface of each refrigerant passage 6a can be raised to approximately the upper end of each rib 10 as shown in FIG. Thus, even when the amount of generated steam is increased, a decrease in the liquid level can be suppressed, and the liquid refrigerant can be supplied to the boiling surface of the refrigerant chamber 6, so that dryout of the boiling surface can be prevented. Further, since the ribs 10 forming the refrigerant passages 6a are provided integrally with the outer wall plate 2B, the heat transfer area of the refrigerant chamber 6 is increased, and the performance of the cooler 1 can be improved. Further, by providing the rib 10, the pressure resistance of the refrigerant tank 2 as a pressure vessel can be secured.

In the groove structure G of the present invention, it is important that the respective refrigerant passages 6a are formed continuously in the vertical direction. For example, as shown in FIG. 8, when each rib 10 is divided into a plurality of parts in the vertical direction, when the bubbles generated at the lower part of the boiling surface rise in the refrigerant passage 6a, the rib 1
Since the bubbles are dispersed from the position where 0 is interrupted, the liquid refrigerant cannot be lifted above the boiling surface, and may dry out above the boiling surface. On the other hand, in the present invention, since the ribs 10 are provided continuously without being divided, the respective refrigerant passages 6a are formed continuously in the up-down direction, and the above effects can be obtained.

(Second Embodiment) FIG. 9 is a plan view of the outer wall plate 2B viewed from the rib 10. This embodiment is a first example in which short groove structures G ₁ and G ₂ are also provided above and below a long groove structure G provided on the boiling surface of the refrigerant chamber 6. The short upper and lower groove structures G ₁ , G ₂ are formed by forming the pillar portion 10A (see FIG. 5) on the outer wall plate 2B by extrusion and then processing the upper and lower portions of the pillar portion 10A. Can be. In this case, by providing short upper and lower groove structures G ₁ and G ₂ ,
There is an effect that the heat transfer area of the refrigerant chamber 6 can be further enlarged and the pressure resistance strength can be improved.

(Third Embodiment) FIG. 10 is a plan view of the outer wall plate 2B as viewed from the rib 10 side. This embodiment is a second example in which short groove structures G ₁ and G ₂ are provided also on the upper and lower portions of the long groove structure G provided on the boiling surface of the refrigerant chamber 6. Short groove structure G ₁ is top, each rib 10
Is provided to be inclined toward the one header connection port 7 side which is a vapor outlet, and the short groove structure G at the bottom is provided with a liquid return passage 8.
It is provided inclining to the exit side of. Thus, refrigerant vapor rises in the long groove structure G is the upper short groove structure G ₁ by the vapor outlet effectively flows that can to (one of the header connecting port 7), also is liquefied in the heat radiating section 3 condensate having flowed into the fluid return passage 8 Te is supplied to effectively long groove structure G by a short groove structure G ₂ of the bottom. As a result, the circulation of the refrigerant inside the refrigerant tank 2 is promoted, and the performance can be improved.

(Fourth Embodiment) FIG. 11 is a plan view of an outer wall plate 2B viewed from the rib 10. This embodiment is a third example in which short groove structures G ₁ and G ₂ are also provided above and below a long groove structure G provided on the boiling surface of the refrigerant chamber 6. In this case, although the shape of each rib 10 in the upper and lower groove structures G ₁ and G ₂ is different from that of the third embodiment, the same effect as that of the third embodiment can be obtained.

(Modification) The boiling cooler 1 of this embodiment is used in a state where the refrigerant tank 2 is in an upright position (the state shown in FIG. 2), but in a state in which the refrigerant tank 2 is turned sideways (however, The heat radiating portion 3 can be used in a state in which the heat radiating portion 3 stands upright above the refrigerant tank 2).

[Brief description of the drawings]

FIG. 1 is a plan view of an outer wall plate viewed from a rib side (first embodiment).

FIG. 2 is a perspective view of a boiling cooler.

FIG. 3 is a perspective view showing a use state of the boiling cooler.

FIG. 4 is a perspective view showing the internal structure of a boiling cooler.

FIG. 5 is a perspective view (a) and a plan view (b) of the outer wall plate.

FIG. 6 is a graph showing a relationship between a Laplace length and an operating temperature of a cooler.

FIG. 7 is a diagram illustrating the operation of the groove structure.

FIG. 8 is a diagram illustrating an operation when the groove structure is shortened.

FIG. 9 is a plan view of an outer wall plate viewed from a rib side (second embodiment).

FIG. 10 is a plan view of the outer wall plate viewed from the rib side (third embodiment).
Example).

FIG. 11 is a plan view of an outer wall plate viewed from a rib side (fourth embodiment).
Example).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Boiling cooler 2 Refrigerant tank 2B Outer wall plate (outer wall part) 2a The other surface of the refrigerant tank 3 Heat radiating part 4 CPU (computer chip / heating element) 5 Printed circuit board 6 Refrigerant chamber 6a Refrigerant passage 10 Rib

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Koji Tanaka 1-1-1, Showa-cho, Kariya-shi, Aichi Pref. F term (reference) 5E322 AA01 AB11 BB03 DB02 DB06 FA01 5F036 AA01 BA08 BA10 BA23 BA28 BB44

Claims (5)

[Claims] 1. A refrigerant chamber for storing a liquid refrigerant therein is formed,
A coolant tank in which a heating element is attached to one of two surfaces facing each other via the coolant chamber; and a coolant tank provided on the other surface of the coolant tank, and receives heat of the heating element in the coolant chamber. And a heat radiating section for radiating heat by exchanging heat of the boiling refrigerant vapor with an external fluid, wherein the refrigerant tank extends at least a boiling surface of the refrigerant chamber in a vertical direction. A boiling cooler, wherein a passage portion is formed, and a passage width of the passage portion is set to be equal to or less than twice a Laplace length. 2. The boiling cooler according to claim 1, wherein the length of the plurality of passages in the vertical direction is equal to or longer than the length of the heating element. 3. The refrigerant tank has an outer wall portion that forms the one surface or the other surface, and a plurality of partition walls that define a space between the adjacent passage portions on an inner surface of the outer wall portion. 3. The boiling cooler according to claim 1, wherein the ribs are provided integrally. 4. The boiling cooler according to claim 3, wherein the outer wall having the plurality of ribs is made of extruded material. 5. The boiling cooler according to claim 1, wherein said heating element cools a computer chip mounted on a printed circuit board.