HEAT EXCHANGER WITH ANGLED SECONDARY FINS EXTENDING FROM PRIMARY FINS
A heat exchanger, method of fabrication and cooled electronics system employing the heat exchanger are provided. The heat exchanger, which in one embodiment cools air provided to heat generating components of a computer system, is disposed at an angle with respect to a direction of airflow. The heat exchanger includes a plurality of primary fins oriented parallel, and at least one plurality of secondary fins extending from at least one of a leading edge and a trailing edge of the plurality of primary fins. Each secondary fin extends from a respective primary fin at an angle other than 0° to facilitate airflow through the heat exchanger. Additionally, the secondary fins are fixedly positioned relative to and integral with the primary fins, thereby providing an increased heat transfer surface area.
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This application contains subject matter related to the subject matter of the following co-pending application, which is assigned to the same assignee as this application and which is hereby incorporated herein by reference in its entirety:
“Heat Exchanger with Angled Fin”, Campbell et al., Ser. No. 11/420,237, filed May 25, 2006.
TECHNICAL FIELDThe present invention relates generally to heat transfer mechanisms, and more particularly, to cooling of heat generating components used in computing system environments. Still more particularly, the present invention relates to cooling of heat generating components used in large computing environments, such as rack or blade mounted computer server units.
BACKGROUND OF THE INVENTIONAs is well known, as circuit density of electronic devices increases in order to achieve faster and faster processing speeds, there is a corresponding increasing demand for the removal of heat generated by these devices. The increased heat load arises both because the devices are packaged more closely together and because the circuits themselves are operated at increasingly higher clock frequencies. Nonetheless, it is also known that thermal runaway conditions and excessive heat generated by circuits is a leading cause of failure of electronic devices. Furthermore, it is anticipated that the demand for heat removal from these devices will increase indefinitely.
Accordingly, there is a large and significant need to provide useful cooling mechanisms for electronic components, individually and at all levels of packaging, including for example, rack-mounted or blade-mounted electronic components of various large computer systems today.
SUMMARY OF THE INVENTIONBriefly summarized, provided herein in one aspect is a heat exchanger which includes: a plurality of primary fins oriented parallel; and at least one plurality of secondary fins extending from at least one of a leading edge and a trailing edge of the plurality of primary fins. Each secondary fin extends from a respective primary fin at an angle other than 0° to facilitate airflow through the heat exchanger.
In another aspect, a cooled electronics system is provided which includes: at least one heat generating component; a housing containing the at least one heat generating component; an air-moving device for moving air within the housing containing the at least one heat generating component; and an air-to-liquid heat exchanger disposed within the housing. The air-to-liquid heat exchanger includes a plurality of primary fins oriented parallel and at least one plurality of secondary fins extending from at least one of a leading edge and a trailing edge of the plurality of primary fins. Each secondary fin extends from a respective primary fin at an angle other than 0° to facilitate airflow through the air-to-liquid heat exchanger, wherein the airflow through the air-to-liquid heat exchanger is at least partially established by the air-moving device.
In a further aspect, a method of fabricating a heat exchanger is provided. The method includes: forming a plurality of primary fins oriented parallel, the plurality of primary fins having a leading edge and a trailing edge relative to an anticipated direction of airflow through the heat exchanger, wherein the heat exchanger is to be disposed at an angle with respect to the direction of airflow; and wherein the forming includes forming at least one plurality of secondary fins extending from at least one of the leading edge and the trailing edge of the plurality of primary fins, each secondary fin extending from a respective primary fin at an angle other than 0°, wherein the angle that at least some secondary fins extend from the respective primary fins is selected to reduce pressure drop through the heat exchanger based on anticipated orientation of the heat exchanger relative to the direction of airflow on at least one of an air inlet side or an air outlet side of the heat exchanger.
Further, additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
As used herein, “electronics system” comprises one or more heat generating components of a computer system or other electronics system requiring cooling. By way of example, an electronics system may comprise a mainframe server in one implementation. The term “electronics rack” includes any housing, frame, rack, blade server system, etc., having a heat generating component of a computer system or electronics system, and may be, for example, a stand alone computer processor having high, mid or low end processing capability. In one embodiment, an electronics rack may comprise multiple electronics drawers, each comprising an electronics system with one or more heat generating components requiring cooling. Each heat generating component may comprise an electronics device, such as an electronics component, an integrated circuit chip, a single-chip electronics module, a multi-chip electronics module, etc.
A “heat exchanger” means any heat exchange mechanism through which coolant can circulate; and includes, one or more discrete heat exchange devices coupled either in series or in parallel. A heat exchange device may comprise, for example, one or more coolant flow paths, formed of thermally conductive fluid conduit (such as copper, brass or other tubing) in thermal or mechanical contact with a plurality of air-cooled primary fins (formed of a thermally conductive material, such as copper). Unless otherwise specified, size, configuration and construction of the heat exchangers described herein below can vary without departing from the scope of the present invention.
One example of coolant passing through the thermally conductive fluid conduit of the heat exchanger is water. However, the concepts disclosed herein are readily adapted to use with other types of coolant. For example, the coolant may comprise a brine, a fluorocarbon liquid, a liquid metal, or other similar coolant, or a refrigerant, while still maintaining the advantages and unique features of the present invention.
As explained briefly above, advances in semiconductor technology have led to an exponential increase in microprocessor performance over the past several years. This has led to a steep increase in consumed rack power within the air-cooled data center equipment, representing a significant thermal design and cooling challenge. Increasing heat load and local heat flux in mid-range and high-volume server packages has become a significant factor in the implementation of new CMOS technology. Current air-cooled heat sinks, even those employing vapor-chamber heat spreaders, are reaching the limit of their extendibility to the new hotter microprocessors.
Data center equipment can house several hundred, and sometimes several thousand, microprocessors. Facility level air cooling of these data center systems is typically carried out using large air conditioning units that supply chilled air to the front of the server racks by an under-floor or overhead ducting system. These air cooling options have limitations with respect to the maximum heat flux they can support, which is typically in the 50-200 Watts per square foot range. Data center heat fluxes, especially in localized regions can far exceed these values, and can be as high as 500 Watts per square foot, when current high performance, high power server racks (20-35 kW/rack) are brick-walled to form high density clusters. The efficient cooling of such computer systems is one focus of the present invention. However, the concepts disclosed herein are equally applicable to other computing environments, including personal computers and laptops.
Disclosed herein are various heat exchanger embodiments referred to as “angled fin heat exchangers” and “heat exchangers with angled secondary fins extending from primary fins”. Angled fin heat exchangers are described below with reference to
As shown in
In
The angled heat exchanger design provides for cooling rack-mounted modular electronic units, and addresses some of the defects existing in the prior art by combining an air cooling approach with an air-to-water heat exchanger fixed within the server cabinet. In this regard, the oblique heat exchanger 350 design of
As an alternate electronics system implementation to that illustrated in
As illustrated in
The pressure drop through the heat exchanger in an oblique orientation is primarily a function of the degree of air turning and the channel flow length. The degree of air turning is represented by an angle of attack ψ. Angle ψ is defined as the angle between the upstream airflow direction and the folded fins/channels and is related to the heat exchanger angle θ and fin angle φ as shown in
As illustrated,
For example, an attack angle of zero degrees represents the “no air turning” configuration shown and discussed above in conjunction with the embodiment of
As the angle of attack increases from a value of zero, the air turning contribution to pressure drop increases, but the channel pressure drop decreases because of the decreasing channel flow length. A computational fluid dynamics analysis was undertaken to demonstrate that there is an optimum attack angle, and thus an optimum fin angle, for which pressure drop is a minimum. The results of the analysis are provided in
Note that angle θ, for this graph has been consistently kept at a value of 16.54 degrees as illustrated. At a zero attack angle, as shown, the air pressure drop value is 0.058 inches of water and this value actually decreases to less than 0.04 inches of water at around a 15 degree angle of attack and then from that point on the air pressure drop value increases. It should be noted that the example provided in the graph depicted in
The problem of optimizing the value of different angles including the angle of attack has now been explored, and attention is turned to methods of manufacturing such an optimal folded fins with optimal angles. As will be appreciated by those skilled in the art, a variety of different embodiments can be used to achieve such fabrication goals. For ease of understanding, however, a couple of such methodologies will be explored below. As suggested, however, such methods are only provided as examples and should not be restrictive and limiting as with regards to the teaching of the present invention. A first and second method of fabricating a folded finned heat exchanger with an optimal angle is illustrated in
In the embodiment illustrated, air flows in a direction 1130a at an air inlet side of the heat exchanger and in a direction 1130b at an air outlet side of the heat exchanger, which in this example is the same direction as the direction of airflow on the air inlet side. Thus, the secondary fins on the leading edge of the primary fins are angled to extend in the direction of airflow, and the secondary fins at the trailing edge of the primary fins are also angled to extend in the direction of airflow. The secondary fins 1120a at the leading edge of the primary fins receive and direct the airflow 1130a into the air passageways or channels 1140 defined by the primary fins 1110, which in the embodiment illustrated are defined by a folded fin construction. After flowing across the primary fins, the airflow is then redirected by the secondary fins 1120b at the trailing edge of the primary fins to align to the direction of airflow 1130b on the outlet side of the heat exchanger.
As shown in the figures, secondary fins 1120a, 1120b function as airflow direction fins or vanes which are integrally formed with the plurality of primary fins 1110. Thus, in addition to guiding the airflow into and out of the fin core, the secondary fins also provide greater heat transfer surface area compared with the primary fins alone. In the exemplary embodiment, each primary fin of the plurality of primary fins has a first, similar heat transfer surface area, and each secondary fin of the plurality of secondary fins has a second, similar heat transfer surface area, wherein the first surface area is greater than the second surface area. Although the height of each secondary fin is (in one example) the same or similar to the height of each primary fin, the distance that each secondary fin extends from the primary fin can vary between implementations, for example, dependent upon size restrictions imposed by the airway conduit within which the heat exchanger is to be placed. As best shown in
Further, although shown with a first plurality of secondary fins 1120a and a second plurality of secondary fins 1120b, dependent on the implementation, secondary fins may be employed only on the leading edge 1111 or the trailing edge 1112 of the plurality of primary fins 1110. Further, the angle that the secondary fins form on the leading edge and the angle that the secondary fins form on the trailing edge may be different and unrelated depending, for example, on the configuration of the airway passage within which the heat exchanger is to be placed.
A thermal and hydraulic analysis was carried out for a section of fins representative of a heat exchanger core. The fins were oriented at an angle to the airflow so that the airflow was forced to turn upon entering and leaving the heat exchanger. Three cases were considered. A conventional heat exchanger such as depicted in
Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention, and that these are therefore considered to be within the scope of the invention as defined in the following claims.
Claims
1. A heat exchanger comprising:
- a plurality of primary fins oriented parallel; and
- at least one plurality of secondary fins extending from at least one of a leading edge and a trailing edge of the plurality of primary fins, each secondary fin extending from a respective primary fin at an angle other than 0° to facilitate airflow through the heat exchanger.
2. The heat exchanger of claim 1, wherein at least the leading edge of the plurality of primary fins is disposed at angle α with respect to a direction of airflow, wherein angle α≠0°, and wherein at least some secondary fins of the at least one plurality of secondary fins extend from the plurality of primary fins at an angle β to the plurality of primary fins, wherein β=α.
3. The heat exchanger of claim 1, wherein the heat exchanger further comprises a first plurality of secondary fins and a second plurality of secondary fins, wherein the first plurality of secondary fins extend from the leading edge of the plurality of primary fins and the second plurality of secondary fins extend from the trailing edge of the plurality of primary fins, wherein the first plurality of secondary fins extend from the plurality of primary fins at an angle aligned to a direction of airflow on an air inlet side of the heat exchanger, and wherein the second plurality of secondary fins extend from the plurality of primary fins at an angle aligned to a direction of airflow on an air outlet side of the heat exchanger.
4. The heat exchanger of claim 1, wherein the at least one plurality of secondary fins are fixedly positioned relative to and integral with the plurality of primary fins and provide an increased heat transfer surface area over the plurality of primary fins alone.
5. The heat exchanger of claim 1, wherein the at least one plurality of secondary fins comprises n secondary fins, and the plurality of primary fins comprises m primary fins, wherein n≦m, and wherein the n secondary fins at least one of:
- extend at the leading edge of the plurality of primary fins from at most every other primary fin of the m primary fins; and
- extend at the trailing edge of the plurality of primary fins from at most every other primary fin of the m primary fins.
6. The heat exchanger of claim 1, wherein the at least one plurality of secondary fins comprises at least one of:
- a first plurality of secondary fins extending from the leading edge of the plurality of primary fins at a first angle, wherein the first plurality of secondary fins extend from all primary fins of the plurality of primary fins; and
- a second plurality of secondary fins extending from the trailing edge of the plurality of primary fins at a second angle, wherein the second plurality of secondary fins extend from all primary fins of the plurality of primary fins.
7. The heat exchanger of claim 1, wherein the at least one plurality of secondary fins are fixedly positioned relative to and integral with the plurality of primary fins, and wherein the plurality of primary fins comprise a plurality of primary folded fins fabricated of a thermally conductive material, and wherein the heat exchanger further comprises at least one fluid conduit extending through and coupled to the plurality of primary folded fins for carrying fluid through the heat exchanger, wherein heat is transferred between the airflow and the fluid via the plurality of primary folded fins and the at least one plurality of secondary fins extending therefrom.
8. The heat exchanger of claim 1, wherein primary fins of the plurality of primary fins each have at least a first surface area and secondary fins of the at least one plurality of secondary fins each have at most a second surface area, wherein the first surface area is greater than the second surface area, and wherein the angle that each secondary find extends from a respective primary fin is selected to reduce pressure drop through the heat exchanger based on anticipated orientation of the heat exchanger relative to a direction of airflow on at least one of an air inlet side or an air outlet side of the heat exchanger.
9. A cooled electronics system comprising:
- at least one heat generating component;
- a housing containing the at least one heat generating component;
- an air-moving device for moving air within the housing containing the at least one heat generating component; and
- an air-to-liquid heat exchanger disposed within the housing, the air-to-liquid heat exchanger comprising: a plurality of primary fins oriented parallel; and at least one plurality of secondary fins extending from at least one of a leading edge and a trailing edge of the plurality of primary fins, each secondary fin extending from a respective primary fin at an angle other than 0° to facilitate airflow through the air-to-liquid heat exchanger, wherein the airflow through the air-to-liquid heat exchanger is at least partially established by the air-moving device.
10. The cooled electronics system of claim 9, wherein the housing contains a computing environment and comprises a server frame, and wherein the heat exchanger is disposed in a side-mounted sub-frame of the server frame, the heat exchanger being disposed so that airflow forms a closed airflow loop through the server frame and the sub-frame and enters and exits the heat exchanger as part of the closed airflow loop, and wherein the air-to-liquid heat exchanger extracts heat from the air and transfers the heat to fluid passing through at least one fluid conduit coupled to the plurality of primary fins.
11. The cooled electronics system of claim 9, wherein at least the leading edge of the plurality of primary fins is disposed at angle α with respect to a direction of airflow, wherein angle α≠0°, and wherein at least some secondary fins of the at least one plurality of secondary fins extend from the plurality of primary fins at an angle β to the plurality of primary fins, wherein β=α.
12. The cooled electronics system of claim 9, wherein the heat exchanger further comprises a first plurality of secondary fins and a second plurality of secondary fins, wherein the first plurality of secondary fins extend from the leading edge of the plurality of primary fins and the second plurality of secondary fins extend from the trailing edge of the plurality of primary fins, wherein the first plurality of secondary fins extend from the plurality of primary fins at an angle relative to the primary fins aligned to a direction of airflow on an air inlet side of the heat exchanger, and wherein the second plurality of secondary fins extend from the plurality of primary fins at an angle aligned to a direction of airflow on an air outlet side of the heat exchanger, wherein the air-to-liquid heat exchanger is disposed at an angle relative to at least one of the direction of airflow on the air inlet side and the direction of airflow on the air outlet side thereof.
13. The cooled electronics system of claim 9, wherein the at least one plurality of secondary fins comprises n secondary fins, and the plurality of primary fins comprises m primary fins, wherein n≦m, and wherein the n secondary fins at least one of:
- extend at the leading edge of the plurality of primary fins from at most every other primary fin of the m primary fins; and
- extend at the trailing edge of the plurality of primary fins from at most every other primary fin of the m primary fins.
14. The cooled electronics system of claim 9, wherein the at least one plurality of secondary fins comprises at least one of:
- a first plurality of secondary fins extending from the leading edge of the plurality of primary fins at a first angle, wherein the first plurality of secondary fins extend from all primary fins of the plurality of primary fins; and
- a second plurality of secondary fins extending from the trailing edge of the plurality of primary fins at a second angle, wherein the second plurality of secondary fins extend from all primary fins of the plurality of primary fins.
15. The cooled electronics system of claim 9, wherein the plurality of primary fins comprise a plurality of primary folded fins fabricated of a thermally conductive material, and wherein the air-to-liquid heat exchanger further comprises at least one fluid conduit extending through and coupled to the plurality of primary folded fins for carrying fluid through the heat exchanger, wherein heat is transferred between the airflow and the fluid via the plurality of primary folded fins and the at least one plurality of secondary fins extending therefrom.
16. The cooled electronics system of claim 9, wherein primary fins of the plurality of primary fins each have at least a first surface area and secondary fins of the at least one plurality of secondary fins each have at most a second surface area, wherein the first surface area is greater than the second surface area, and wherein the angle that each secondary fin extends from a respective primary fin is selected to reduce pressure drop through the air-to-liquid heat exchanger based on orientation of the air-to-liquid heat exchanger relative to direction of airflow on at least one of an air inlet side or an air outlet side of the air-to-liquid heat exchanger.
17. A method of fabricating a heat exchanger, the method comprising:
- forming a plurality of primary fins oriented parallel, the plurality of primary fins having a leading edge and a trailing edge relative to an anticipated direction of airflow into the heat exchanger, wherein the heat exchanger is to be disposed at an angle with respect to the direction of airflow; and
- wherein the forming includes forming at least one plurality of secondary fins extending from at least one of the leading edge and the trailing edge of the plurality of primary fins, each secondary fin extending from a respective primary fin at an angle other than 0°, wherein the angle that at least some secondary fins extend from the respective primary fins is selected to reduce pressure drop through the heat exchanger based on anticipated orientation of the heat exchanger relative to the direction of airflow on at least one of an air inlet side or an air outlet side of the heat exchanger.
18. The method of claim 17, wherein at least the leading edge of the plurality of primary fins is to be disposed at an angle α with respect to the direction of airflow, wherein angle α≠0°, and wherein at least some secondary fins of the at least one plurality of secondary fins are formed to extend from the plurality of primary fins at an angle β to the plurality of primary fins, wherein β=α.
19. The method of claim 17, wherein the at least one plurality of secondary fins comprises n secondary fins, and the plurality of primary fins comprises m primary fins, wherein n≦m, and wherein the n secondary fins are formed to at least one of:
- extend at the leading edge of the plurality of primary fins from at most every other primary fin of the m primary fins; and
- extend at the trailing edge of the plurality of primary fins from at most every other primary fin of the m primary fins.
20. The method of claim 17, wherein forming the at least one plurality of secondary fins comprises forming at least one of:
- a first plurality of secondary fins extending from the leading edge of the plurality of primary fins at a first angle, wherein the first plurality of secondary fins extend from all primary fins of the plurality of primary fins; and
- a second plurality of secondary fins extending from the trailing edge of the plurality of primary fins at a second angle, wherein the second plurality of secondary fins extend from all primary fins of the plurality of primary fins.
Type: Application
Filed: Jul 20, 2006
Publication Date: Jan 24, 2008
Applicant: INTERNATIONAL BUSINESS MACHINES CORPORATION (Armonk, NY)
Inventors: Levi A. Campbell (Poughkeepsie, NY), Richard C. Chu (Hopewell Junction, NY), Michael J. Ellsworth (Lagrangeville, NY), Madhusudan K. Iyengar (Woodstock, NY), Roger R. Schmidt (Poughkeepsie, NY), Robert E. Simons (Poughkeepsie, NY)
Application Number: 11/458,696
International Classification: F28D 1/04 (20060101);