This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2011-161356, filed on Jul. 22, 2011, the entire contents of which are incorporated herein by reference.
The embodiments disclosed herein are related to a cooling unit that cools electronic components mounted in an electronic device, using coolant.
In recent years, in PC servers, the rack-mount system has become mainstream. In the rack-mount system, a plurality of server modules are mounted so that they are stacked on top of each other in a rack cabinet. One or more integrated circuit elements (LSIs) typified by processors (CPUs) are mounted on each server module. In a server or a personal computer, a dedicated fan is placed immediately above a component that generates a large amount of heat, such as a CPU or an LSI, and the component is air-cooled so as to stabilize the operation. However, in the rack mount system, in order to improve performance and to save space, as many server modules as possible have to be stacked in a rack cabinet. For this reason, the thickness of individual server modules has to be reduced. Thus, in rack-mounted server modules, it is difficult to attach a fan directly to a component that generates a large amount of heat, such as a CPU or an LSI. In addition, since the server modules are stacked, it is difficult to release the heat generated in individual server modules to the outside. In order to solve these problems, there is a method to cool a CPU, an LSI, or the like, including circulating coolant over a heat-generating component, such as a CPU or an LSI, circulating the coolant that has absorbed heat from the CPU, LSI, or the like to a radiator with a pump, and cooling the coolant with a cooling fan
The following is reference documents:
According to an aspect of the invention, a cooling unit includes: at least one pump that circulates coolant; a tank having a first inlet through which coolant is caused to flow in and at least one first outlet through which the coolant is expelled to the at least one pump; and an air bubble accumulating portion provided in an upper part of the tank, wherein the first inlet is disposed at a position such that the coolant is caused to flow into the air bubble accumulating portion, and the at least one first outlet is provided below the air bubble accumulating portion.
The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.
The preferred embodiments of the present disclosure will be described in detail with reference to the drawings.
A radiating fin 10 is disposed at an end of the inside of the server module 100 (in the upper part of
The server is usually installed in a temperature controlled room. Thus, the plurality of fans 70 may be rotated in the opposite direction to suck in outside air through the end of the server module 100 to cool the radiating fin 10 with the outside air. Also in this case, a cooling effect is achieved.
A tank 40 that stores coolant is disposed inside the server module 100. In the case of this embodiment, in order to save space, the tank 40 is disposed on the top of the cooling jacket 92 on the top of one of the CPUs 90. A plurality of pumps 80 are connected to a side surface of the tank 40. Coolant pressurized by the pumps 80 is sent out from the tank 40 to a pipe 60.
In this embodiment, in order to improve reliability, not only a single pump but a plurality of pumps are provided. If one of the pumps brakes down and stops working, the flow of coolant may be maintained by the other pump, and the temperature rise of heat-generating components such as CPUs 90 may be suppressed. It is also possible to control the number of working pumps to change the flow rate of coolant to adjust the cooling effect according to the operating conditions of the CPUs 90.
Coolant sent out from the tank 40 absorbs heat from the CPUs 90 in the cooling jackets 92 and is sent to the radiating fin 10 through a pipe 61. Coolant is cooled in the radiating fin 10 by the fans 70 and is returned to the tank 40 by a pipe 62. The cooling unit includes the tank 40, the pipe 60, the cooling jackets 92, the pipe 61, the radiating fin 10, and the pipe 62. Coolant circulates through these components, which form a radiating circulation loop. By arranging this radiating circulation loop linearly and setting the route short, coolant may be returned in a short time and the heat radiating efficiency may be improved. The circuit board 95 is designed centering around the CPUs 90, which are the nerve centers of the circuit, and thus the CPUs 90 are often disposed in the center of the circuit board 95. Thus, the radiating circulation loop is also often disposed across the center of the circuit board 95.
For example, a propylene glycol based antifreeze is used as coolant. However, examples of coolant are not limited to this. Parts of the pipes 60, 61, and 62 are made of a flexible heat-insulating material such as rubber or resin. Parts of the pipes 60, 61, and 62 near the cooling jackets 92 are made of a material having good thermal conductivity such as metal in order to efficiently transfer heat from the CPUs 90 to coolant.
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Coolant cooled by the radiating fin 10 is caused to flow through the pipe 62 and the inlet 50 into the coolant storing chamber 42. The pumps 80 suck coolant through pump suction ports 54 of the coolant storing chamber 42 located below the coolant mixing chamber 44, and pump suction pipes 82, and then expel coolant through pump expelling pipes 84 and pump expelling ports 56 into the coolant mixing chamber 44.
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In addition to coolant flowing through the radiating circulation loop, coolant for replacing coolant lost through the surface of rubber that makes up the pipes and the surface of resin that makes up the pumps is stored in the tank 40.
At the stage of manufacturing the server module 100, the radiating circulation loop is filled with coolant. The coolant storing chamber 42 and the coolant mixing chamber 44 in the tank 40 are also filled with coolant. Coolant filling is usually performed at room temperature. At this time, air is dissolved in coolant.
When the server module 100 operates and the cooling of the CPUs 90 starts, the temperature of coolant rises, and air dissolved in coolant at room temperature vaporizes to become air bubbles. The air bubbles move through the radiating circulation loop with the flow of coolant. If the air bubbles accumulate in the pumps 80, air locks may arise in the pumps 80, and the ability to expel coolant may decrease significantly.
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The pumps 80 suck out coolant from the tank 40A and expel coolant to the tank 40A, thereby producing a flow of coolant. Coolant expelled from the pumps 80 is returned to the radiating circulation loop through an outlet 52 provided in one of the surfaces of the tank 40A to which the pumps 80 are connected, and the pipe 60.
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In this embodiment, six pumps 80 are provided in order to improve reliability and cooling efficiency. For this reason, the coolant mixing chambers 44 for collecting coolant expelled from the plurality of pumps 80 and returning the collected coolant to the radiating circulation loop are used. In order not to stop the flow of coolant even if one of the pumps 80 brakes down, three pumps 80 are connected in parallel to one coolant mixing chamber 44. Three pumps 80 are connected in parallel to one coolant mixing chamber 44 so that if one of the pumps 80 brakes down, the flows of coolant of the other pumps 80 are not stopped.
Coolant cooled by the radiating fin 10 is caused to flow through the pipe 62 and the inlet 50 into the coolant storing chamber 42. The pumps 80 on the left and right sides suck coolant through pump suction ports 54 of the coolant storing chamber 42 located below the coolant mixing chambers 44, and pump suction pipes 82, and then expel coolant through pump expelling pipes 84 and pump expelling ports 56 into the left and right coolant mixing chambers 44.
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Owing to the above-described structure, also in this embodiment, air locks of the pumps 80 may be suppressed. Since air bubbles generated in the radiating circulation loop finally accumulate in the coolant storing chamber 42, the amount of coolant flowing through the radiating circulation loop is substantially stable, and a decrease in cooling efficiency may be suppressed.
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All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
Number | Date | Country | Kind |
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2011-161356 | Jul 2011 | JP | national |