Air inlet channel with thermoelectric cooling element

An example electronic device may include a chassis, a circuit board in the chassis that includes a first active component, a number of fans, a number of guide walls that define an air inlet channel, and a thermoelectric cooler (TEC). There may be an airflow path such that, when the fans operate, air flows along the airflow path from an intake opening of the air inlet channel to an exhaust of the chassis, with the first active component being located in the airflow path downstream of the intake opening of the air inlet channel. A cold portion of the TEC may extend into the airflow path upstream of the first active component and a hot portion of the TEC may extend into the airflow path downstream of the first active component.

BACKGROUND

Electronic devices, such as servers, may include components that are sensitive to heat. One approach to cooling such components includes causing air to flow over the component, for example via a fan.

DETAILED DESCRIPTION

In certain example electronic devices described herein, an airflow path is arranged so as to cool a heat-sensitive component, and a thermoelectric cooler (TEC) is placed in the airflow path such that a cool side of the TEC is in the airflow path upstream of the heat-sensitive component and a hot side of the TEC is in the airflow path downstream of the heat-sensitive component. Because of the location and arrangement of the TEC, the TEC may draw heat out of (i.e., cool) the air in the airflow path upstream of the heat-sensitive component, and may release heat into (i.e., heat) the air in the airflow path downstream of the heat-sensitive component. Thus, the air in the airflow path may be cooler when it reaches the heat-sensitive component than it otherwise would have been without the TEC, and therefore the air may be able to better cool the heat-sensitive component. This example technique of using the TEC to cool air in the airflow path upstream of the heat-sensitive component may be referred to herein as “pre-cooling.”

In certain examples, the airflow path may flow to the heat-sensitive component via an air inlet channel formed by a number of guide walls, and the TEC may be arranged such that the cool side thereof extends into the air inlet channel. In certain examples, the air flow path may flow over the cool side of the TEC in one direction, reverse directions downstream of the cool side of the TEC, and then flow over the hot side of the TEC in a second direction that is opposite of the first direction.

Pre-cooling may be particularly beneficial when, for example, the air that is upstream of the heat-sensitive component is too hot to satisfactorily cool the heat-sensitive component. For example, other devices and/or other components within the same device as the heat-sensitive component may heat the air upstream of the heat-sensitive component such that it is too hot to satisfactorily cool the heat-sensitive component. As another example, the ambient air itself may be too hot to satisfactorily cool the heat-sensitive component even without being pre-heated by other components within the device.

For example, pre-cooling may be particularly beneficial in an example electronic device in which a number of first components (e.g., compute modules, storage modules, server blades, etc.) and a number of second components (e.g., networking modules) are arranged in the same chassis, with the first components being upstream of the second components in an airflow path for cooling the components. For example, certain blade server enclosures may adopt such a configuration, with hot-pluggable blades being housed in a front of the chassis, networking modules being housed in a rear of the chassis, a mid-plane connecting the front and rear components, and fans to cause air to flow through the chassis. In such an example system, without the pre-cooling described above, the first components may heat the air in the airflow path such that it is too hot to adequately cool the second components. However, by using the example pre-cooling techniques described above to cool the air at a location in the airflow path that is downstream of the first components and upstream of the second components, the air that impinges on the second components may be made cool enough to satisfactorily cool the second components.

FIGS. 1-4illustrate an example electronic device implementing an example of the above-described pre-cooling techniques.FIG. 1is a block-diagram illustrating features of the example electronic device in a plan view.FIGS. 2 and 3are block diagrams illustrating, in a plan view, variations on the features shownFIG. 1.FIG. 4is a perspective view of a specific implementation example of the features shown inFIG. 1. Certain features are illustrated in multiple ones of the figures, but such features will be described once herein to avoid duplicative descriptions.

InFIGS. 1-3, certain features (such as the guide wall10B) are not illustrated so as to avoid obstructing the view of certain other features. InFIG. 5, the guide walls10B and10C are made semi-transparent to show the interior of the air inlet channel10. InFIGS. 1-4, certain features (such as additional electronic components on the circuit board40) are not shown to reduce the complexity of the illustration and ease of understanding.

The electronic device includes a circuit board40that has a heat-sensitive component30thereon, a number of guide walls10A-E that define an air inlet channel10, and a TEC20. The electronic device may also include fans60(not shown inFIGS. 1-4) and a chassis90(not shown inFIGS. 1-4) that houses the circuit board40.

The electronic device is configured such that, when the fans60operate, air flows along an airflow path100. Specifically, air flows along the airflow path100from an inlet opening15of the air inlet channel10toward an exhaust of the device. The airflow path100flows: into the air inlet channel10via the inlet opening15, past a cold portion21C of the TEC20in the air inlet channel10, out an exit opening16of the air inlet channel10, past the heat-sensitive component30, past a hot portion21H of the TEC20, and then toward the exhaust. The airflow path100flows in a first direction through the air inlet channel10(e.g., the −x direction inFIGS. 1-4), and the reverses directions after exiting the exit opening16to flow in a second direction (e.g., the +x direction inFIGS. 1-4) over the circuit board40.

Thus, both the cold portion21C and the hot portions21B of the TEC20extend into the airflow path100, but at different locations within the airflow path—specifically, the cold portion21C extends into the airflow path100upstream of the heat-sensitive component30while the hot portion21H extends into the airflow path100downstream of the heat-sensitive component30.

As noted above, the TEC20may have a cold portion21C and a hot portion21H, which are joined together. The cold portion21C may include a cold plate22C (shown as parallel to the x-z plane inFIG. 1) and a number of fins23C extending perpendicularly outward from the cold plate22C. The hot portion21H may include a hot plate22H (shown as parallel to the x-z plane inFIG. 1) and a number of fins23H extending perpendicularly outward from the hot plate22H. The TEC20may use electrical energy to transfer heat from the cold plate22C to the hot plate22H. Thus, when the TEC20is operating, the cold portion21C becomes cold and the hot portion21H becomes hot. In certain examples, an electrical connector24of the TEC20may be plugged into the circuit board40, as illustrated inFIG. 4.

A portion of the TEC20may extend through a hole in the guide wall10C such that at least part of the fins23C are in the air inlet channel10and at least part of the fins23H extend over the circuit board40. For example, the cold plate22C may be disposed on the +y side of the guide wall100and the fins23C may extend from the cold place22C in the −y direction through the hole in the guide wall100. As another example, the cold plate22C may extend through the hole in the guide wall100(i.e., the cold plate22C may be disposed in the hole in the guide wall100). As another example, the cold plate22C may be disposed within the air inlet channel10(i.e., on the −y side of the guide wall100), and a middle portion of the TEC20(and/or the hot plate22H) may extend through hole in the guide wall100. The TEC20may be secured on the guide wall100, for example, by mounting screws.

Because the cold portion21C extends into the airflow path100upstream of the heat-sensitive component30and is colder than the air at that point, the cold portion21C absorbs heat from the air in the airflow path100, thus cooling the air upstream of the heat-sensitive component30. Similarly, because the hot portion21H extends into the airflow path100downstream of the heat-sensitive component30and is hotter than the air at that point, the hot portion21H releases heat into the air in the airflow path100, thus heating the air downstream of the heat-sensitive component30.FIGS. 1-3illustrate these phenomenon by showing the cold portion21C lowering the temperature of the air in the airflow path100by 10° upstream of the heat-sensitive component and by showing the hot portion21H raising the temperature of the air in the airflow path by 10° downstream of the heat-sensitive component30. However the temperatures shown inFIGS. 1-3are merely for purposes of illustration and are not intended to be exact—in practice, the cold portion21C and the hot portion21H may lower and raise the temperature of the air more or less than what is shown. The actual amount that the air is cooled and heated by the TEC20will vary depending on, among other things, the respective temperatures of the cold portion21C and the hot portion21H, the respective temperatures of the air when it reaches the cold portion21C and the hot portion21H, and the design parameters of the TEC20(e.g., the surface areas of the cold plate22C and the hot plate22H, surface materials used, thermoelectric efficiency, amount of electrical power supplied to the TEC, etc.).

The TEC20may be formed from device that uses electrical energy to transfer heat from one side of the device (e.g., the cold plate22C) to the other side of the device (e.g., the hot plate22H). For example, the TEC20may use the thermoelectric effect (Peltier effect) to create a heat flux at a junction of two different materials. In particular, any commercially available TEC may be used as the TEC20. TECs may also be referred to occasionally as Peltier devices, Peltier heat pumps, and solid state refrigerators, and any such device may be used as the TEC20.

The example TEC20described above and illustrated inFIGS. 1-5has multiple fins23C/23H that are used as heat exchangers to improve the efficiency of heat exchange between the TEC20and the air in the airflow path. However, the fins23C/23H could be configured differently than how they are shown inFIGS. 1-5—for example, the fins23C/23H may be flared, more or fewer fins may be included, etc. In some examples, the fins23C/23H may be shaped to direct the airflow path100in certain direction. Moreover, other structures may be used as heat exchangers, in addition to or in lieu of the fins; for example, pins, coils, lattices, or other structures may be used as heat exchangers. In addition, in certain examples the TEC20may have no heat exchanging structures (such as the fins23C/23H) attached to the cold plate22C and the hot plate22H, in which case the cold plate22C and the hot plate22H may serve as the primary mechanisms of heat exchange between the TEC20and the air of the airflow path100.

The heat-sensitive component30may be any active electrical component, such as, for example, a processor, a memory, an application-specific-integrated-circuit (ASIC), an optical interconnect module (or component thereof), etc. For example,FIG. 4illustrates one specific implementation example in which the heat-sensitive component30is an optical interconnect module that includes an optical transceiver. The heat-sensitive component30is an example of the “first active component” recited in several of the appended claims.

The circuit board40may include other electronic components (not illustrated) in addition to the heat-sensitive component30. These other electronic components may also be cooled by the airflow path100, or they may be cooled by other airflow paths—in other words, the airflow path100need not be the only airflow path in the example device. For example, there may be additional electronic components35in the airflow path100that are downstream of the hot portion21H (seeFIG. 4); such electronic components35may be, for example, components that produce less heat or have a higher heat tolerance than the heat-sensitive component30. Moreover, in certain examples there may be multiple electronic components located in the airflow path100between the cold portion21C and the hot portion21H.

For example,FIGS. 2 and 3illustrate examples in which there are two heat-sensitive components30A and30B in the airflow path100between the cold portion21C and the hot portion21H. Certain features illustrated inFIGS. 2 and 3are similar to features illustrated inFIG. 1, and duplicative description of such corresponding features is omitted.

InFIG. 2, the heat-sensitive components30A and30B are located in the airflow path100downstream of the cold portion21C of the TEC20and upstream of the hot portion21H of the TEC20. The airflow path100passes the heat-sensitive component30B and absorbs heat therefrom and then passes the heat-sensitive component30A and absorbs heat therefrom. Thus the air in the airflow path100is at the pre-cooled temperature (e.g., 35° inFIG. 2) when it meets the heat-sensitive component30B, but is at a higher temperature (e.g., 50° inFIG. 2) when it meets the heat-sensitive component30A.

The arrangement of the example device inFIG. 3is similar to the arrangement shown inFIG. 2, except that inFIG. 3there are two exit openings in the air inlet channel10—the exit opening18and the exit opening16—each corresponding to one of the heat-sensitive components30A and30B, respectively. This allows some of the air flowing through the air inlet channel10to follow a first branch100A of the airflow path100while some of the air flowing through the air inlet channel10follows a second branch100B of the airflow path100. The first branch100A may flow to the heat-sensitive component30A, while the second branch100B may flow to the heat-sensitive component30B. The first branch100A and the second branch100B may recombine upstream of or at the heat-sensitive component30A. In certain examples, a baffle17may be included to redirect some of the air in the airflow path100along the branch100A while allowing some of the air in the airflow path100to continue along the branch100B. In certain examples, the first branch100A and the second branch100B of the airflow path100may be caused at least in part by the fins230; for example, the fins23C may be shaped to direct some of the air along the first branch100A (i.e., direct the air towards the baffle17and/or the opening18) and to direct some of the air along the second branch100B (i.e., direct the air towards the opening16).

By directing some air that is at the pre-cooled temperature (e.g., 35° inFIG. 3) toward the heat-sensitive component30A without it first passing over the heat-sensitive component30B, the effective temperature of the air at the heat-sensitive component30A is lower in the arrangement ofFIG. 3than it is in the arrangement ofFIG. 2. In particular, while the air that follows branch100B is the same temperature after it passes the heat-sensitive component30B in bothFIGS. 2 and 3(e.g., 50°), because in the arrangement ofFIG. 3this hotter air is combined with cooler air from the first branch100A at or before the heat-sensitive component30A, the effective combined temperature of the air at the heat-sensitive component30A is lower.

InFIGS. 1-4, an example of the air inlet channel10is illustrated as having a shape roughly like a cuboid, but the air inlet channel10may have any shape. Moreover, the shapes and locations of the TEC20and the heat-sensitive component(s)30inFIGS. 1-4are not meant to be exact, and the actual shapes and locations may differ from what is illustrated. In certain examples, one or more of the guide walls10A-10E may be formed by a wall of the chassis90of the device. For example, the guide wall10A and/or the guide wall10E may be formed by the chassis90. In certain examples, the guide walls10A-E that define the air inlet channel10may perform other functions as well, such as, for example, connecting the circuit board40to the chassis90. For example, inFIG. 4a connector70is illustrated within the air inlet channel10that is to latch the circuit board40to the chassis90.

The airflow path100illustrated inFIGS. 1-3may be a portion of a larger airflow path that may extend from an inlet of the chassis90of the example device to an exhaust of the chassis90of the example device. This larger airflow path may follow any number of possible paths outside the region illustrated inFIGS. 1-3, and any such path is acceptable as long as the path behaves in the manner described above in the region near the TEC20and the heat-sensitive component30. Specially, any larger airflow path is acceptable if, when the fans60are operating, air flows at least: into the air inlet channel10, then past a cold portion21C of the TEC20in the air inlet channel10, then out an exit opening16of the air inlet channel10, then past the heat-sensitive component30, and then past a hot portion21H of the TEC20.FIGS. 5 and 6illustrate specific non-limiting examples of such larger airflow paths.

FIGS. 5 and 6illustrate an example electronic device in perspective views. Specifically,FIG. 5illustrates a portion of the electronic device corresponding to the circuit board40, whileFIG. 6illustrates a chassis90of the example electronic device with a cut-away portion to show how various features including the circuit board40may be situated within the chassis90.

The example device illustrated inFIGS. 5 and 6includes features similar to those described in relation toFIG. 1, and duplicative description of these features is omitted. In particular, the device illustrated inFIGS. 5 and 6is a more detailed example of the device illustrated inFIG. 1. In other words,FIGS. 5 and 6illustrate both the features shown inFIG. 1and additional features pertaining to a broader context in which the features ofFIG. 1may be implemented. It should be understood that the broader context illustrated inFIGS. 5 and 6is merely one example of a context in which the features ofFIG. 1may be implemented.

In the example device illustrated inFIGS. 5 and 6, the circuit board40may have two of each of the features that were described above in relation toFIG. 1, one for each of the right and left sides of the circuit board40. Specifically, an air inlet channel10L is provided on the left side of the circuit board40and an air inlet channel10R is provided on the right side of the circuit board. The air inlet channel10L may provide air via an airflow path100L to cool a heat-sensitive component30L that is located on a left-rear side of the circuit board40, while the air inlet channel10R may provide air via an airflow path100R to cool a heat-sensitive component30R that is located on a right-rear side of the circuit board40. TECs20L/R are connected to the air inlet channels10L/R in the manner described above. Portions of the airflow paths100L and100R may mix together eventually, for example near a middle region of the circuit board40.

In the example device illustrated inFIGS. 5 and 6, the circuit board40is coupled to a midplane50. The midplane50may be to, for example, couple additional electronic components80to the circuit board40. Each of the electronic components80may include a circuit board that has a number of active components, such as CPUs, memory, ASICs, etc. For example, the electronic components80may be server blades, compute modules, storage modules, etc. The electronic components80are examples of the “second circuit board(s)” or “front-end circuit board(s)” referred to in several of the appended claims. The circuit board40may be, for example, a networking module, such as a switch module.

In certain examples, the midplane50may connect to the electronic components80in such a manner that the components80may be hot-pluggable (hot-swappable). In certain examples, the midplane50may also connect to the circuit board40in such a manner that the circuit board40is hot-pluggable (hot-swappable). There may be multiple circuit boards (including the circuit board40) in a rear portion of the chassis that are connected to the midplane50, and some or all of these circuit boards may include an air inlet channel10and TEC20in the manner described above. Such circuit boards in a rear portion of the chassis that are connected to the midplane50(including the circuit board40) are examples of the “back-end circuit board(s)” recited in several of the claims. The circuit board40in particular may be referred to as the “circuit board” of the “first circuit board” in several of the claims.

As illustrated inFIGS. 5 and 6, there may be air gaps between the midplane50and the circuit board40. The fans60may be positioned so as to cause a region below a front portion of the circuit board40to have lower pressure than a region above the front portion of the circuit board40. This pressure differential may cause air to flow in the directions indicated by the arrows inFIG. 5. In particular, this pressure difference causes a pressure gradient between the inlets15of the air inlet channels10L/10R and the air gaps, resulting in air being sucked through the air inlet channels10L/10R, over the circuit board40from rear toward the front, and then down through the air gaps. When air flows in this manner, the airflow path100is formed (among other airflow paths).

For example, the pressure difference describe above may be created by positioning the fans60such that there is an airflow path, such as the airflow path200illustrated inFIG. 6, that flows below the circuit board40in the −x direction. For example, inFIG. 6an exhaust92of the chassis90is located at a rear of the chassis90and the fans60are positioned adjacent to the exhaust92so as to blow out of the chassis90. However, this is merely one example configuration that is capable of forming the airflow path100.

When the fans60are configured as illustrated inFIG. 6, air may flow through the chassis90generally from front to back, entering the chassis90via inlet openings91in the front of the chassis90and exiting the chassis90via the exhaust92. The air may cool the additional electrical components80(i.e., the electrical components80may heat the air) before the air passes the midplane50. A main portion of the air that is heated by the electrical components80passes to the rear of the chassis through the openings51following an airflow path200. In addition, some of the air that is heated by the electrical components80may flow along side channels between a side of the chassis90and the electrical components80and become inlet air98that is drawn into the air inlet channel10along the airflow path100.

As noted above, the inlet air98may be heated by the electrical components80prior to reaching a rear part of the chassis90. The temperature of the inlet air98prior to reaching the TECs20may be too high to adequately cool the heat-sensitive components30. However, because the TECs20are provided in the air inlet channels10L/R in the manner described above, the hot inlet air98may be pre-cooled prior to reaching the heat-sensitive components30to a temperature that is low enough to adequately cool the heat-sensitive components30.

As illustrated inFIG. 6, there may be openings51in the midplane50to facilitate passage of air from the front of the chassis toward the rear—in particular, the airflow path200may start at such an opening51. (Details of the midplane50, such as the aforementioned openings51, are omitted fromFIG. 5for ease of illustration).

In certain examples, the TEC20, the heat-sensitive component30, and/or the circuit board40may include a temperature sensor that senses a temperature in the chassis90. For example, the heat-sensitive component30may include the temperature sensor and may sense the temperature of a portion of the heat-sensitive component30, and/or the temperature of air flowing over the heat-sensitive component30. As another example, the TEC20may include the temperature sensor and may sense the temperature of its cold portion21C (or hot portion21H). Furthermore, in these examples the circuit board40may include a controller41(such as a CPU, an ASIC, etc.) that is to supply power to the TEC20via the electrical connector24. The controller41may receive the sensed temperature from the temperature sensor, and may adjust an operating mode of the TEC20based on the sensed temperature. For example, the controller41may turn the TEC20off if the sensed temperature is below a threshold value and may turn the TEC20on if the sensed temperature passes the threshold value. As another example, the TEC20may have various discrete levels of operations (e.g., low, medium, high, etc.) and the controller41may associate temperature ranges with each such level of operation and may control the TEC20to operate according to which temperature range the sensed temperature falls in. As another example, the TEC20may be able to vary its operating mode continuously (e.g., by continuously varying an analog supply voltage), in which case the controller41may set the supply voltage based on the sensed temperature according to a specified functional relationship.

Herein, airflow paths (such as the airflow paths100and200) are illustrated by way of arrows and lines for ease of description. However, these representations are not intended to be exact, and they should not be interpreted to imply that the airflow paths follow a line or a curve. In fact, an airflow path is not a line or a curve, which has finite (or infinite) extension but infinitesimal width. Instead, an airflow path may fill a three-dimensional volume of space. Each airflow path is associated with an inlet opening, and indicates where air flowing through that inlet opening would go if the fans60were operative. Specifically, as used herein an airflow path is the course between a specific inlet opening and one or more outlet openings along which inlet air would tend to flow if the fans60were operative. More specifically, an airflow path may include any point through which any portion of the inlet air would flow as it flows between the correspond inlet opening and an outlet openings, together with the direction of flow at that point. In other words, the airflow path may be considered as a vector field in a three-dimensional volume, where the volume encompasses all points through which air might flow and each vector indicates a direction of the airflow at that point in the volume. An airflow path is defined by the geometry of the various solid components of the device (e.g., guide walls, circuit boards, etc.), the locations of inlet openings and exhaust openings, and the locations and orientations of fans. Specifically, the airflow path100may include all of the points though which any portion of the air inlet via the opening15may travers as it flows between the opening15and the openings between the circuit board40and the midplane50. An airflow path may include multiple sub-paths, since different portions of the inlet air may traverse different paths.

Throughout this disclosure and in the appended claims, occasionally reference may be made to “a number” of items. Such references to “a number” mean any integer greater than or equal to one. When “a number” is used in this way, the word describing the item(s) may be written in pluralized form for grammatical consistency, but this does not necessarily mean that multiple items are being referred to. Thus, for example, a phrase such as “a number of processors, wherein the processors . . . ” could encompass both one processor and multiple processors, notwithstanding the use of the pluralized form.

The fact that the phrase “a number” may be used in referring to some items should not be interpreted to mean that omission of the phrase “a number” when referring to another item means that the item is necessarily singular or necessarily plural.

In particular, when items are referred to using the articles “a”, “an”, and “the” without any explicit indication of singularity or multiplicity, this should be understood to mean that there is “at least one” of the item, unless explicitly stated otherwise. When these articles are used in this way, the word describing the item(s) may be written in singular form for grammatical consistency, but this does not necessarily mean that only one items is being referred to. Thus, for example, a phrase such as “a processor, wherein the processor . . . ” could encompass both one processor and multiple processors, notwithstanding the use of the singular form.

Occasionally the phrase “and/or” is used herein in conjunction with a list of items. This phrase means that any combination of items in the list—from a single item to all of the items and any permutation in between—may be included. Thus, for example, “A, B, and/or C” may include any one of: {A}, {B}, {C}, {A, B}, {A, C}, {C, B}, and {A, C, B}.

While the above disclosure has been shown and described with reference to the foregoing examples, it should be understood that other forms, details, and implementations may be made without departing from the spirit and scope of this disclosure.