REAR DOOR HEAT EXCHANGER

Abstract

A rear door heat exchanger adapted to be mounted on the rear of a rack or other arrangement of heat-generating electronic equipment, and to cool air which passes therethrough when the rear door heat exchanger is in use. It comprises an upstream header and a downstream header with a multiplicity of substantially parallel microchannels extending between and in fluid communication with both the upstream header and the downstream header. Thus both headers are common to the microchannels of the said multiplicity of microchannels.

Description

Data centers are traditionally cooled by perimeter cooling, in which air to liquid heat exchangers are situated around the perimeter of the room and air is pumped from the interior of the data center to the heat exchangers, underneath the floor of the data center, and from there upwards through air vents in the flooring into aisles between rows of blade racks. Those aisles are therefore cool aisles. The cool air in these aisles passes by convection between the blades and out through to the other side of the row of racks, into a warm aisle. The warm air in the warm aisles passes by convection to the air above the racks, along the ceiling and then downwards once again to the heat exchangers of the perimeter cooling. This cycle is continuous to keep the temperature of the center at an acceptably low level for efficient operation of the blades.

With increasing operational capacity of the blades, an increasing amount of cooling of the air in the data center becomes desirable or even necessary. Simply increasing the cooling capacity of the perimeter cooling is not necessarily an option because of limitation in the amount of cooling that can be effected in this way. This problem has been solved by attaching respective air to fluid heat exchangers at the rear of the racks, where the air flow exits from the racks. Thus “rear” in this sense refers to that side of the racks (or other heat generating electronic apparatus) from which cooling air exits. Such heat exchangers are referred to as rear door heat exchangers. The temperature of the coolant supplied to existing rear door heat exchangers is usually about what would be considered normal room temperature or only slightly lower, typically in the region 18° C. to 22° C. This is still effective because the air temperature where it exits the blades is higher, perhaps in the region of from 35° C. to 45° C.

Existing rear door heat exchangers comprise adjacent generally vertically arranged upstream and downstream headers on one side of the exchanger with horizontal piping extending away from the upstream header turning through 180° at the other side of the heat exchanger and then extending horizontally to the downstream header. Such a construction involves the use of piping of a relatively wide diameter and heavy metal components which make the rear door heat exchanger cumbersome, expensive to manufacture, and difficult to manoeuvre.

The present invention seeks to obviate one or more of these drawbacks, although it will be appreciated that the invention is effective for the cooling of air which has passed by any heat generating electronic equipment whether or not that equipment may fairly be referred to as a blade rack or blade racks.

Accordingly, embodiments of the present invention are directed to a rear door heat exchanger adapted to be mounted on the rear of a rack or other arrangement of heat-generating electronic equipment, and to cool air which passes therethrough when the rear door heat exchanger is in use, comprising an upstream header and a downstream header with a multiplicity of substantially parallel microchannels extending between and in fluid communication with both the upstream header and the downstream header so that both headers are common to the microchannels of the said multiplicity of microchannels.

This facilitates the construction of a light-weight rear door heat exchanger, more especially because the use of microchannels provides a high ratio of heat exchanger surface to cross-sectional area of coolant passageway, and facilitates venting and draining of the heat exchanger.

Preferably the microchannels are upright when the rear door heat exchanger is mounted ready for use.

Insofar as the microchannels extend in a direction which has at least a component in the vertical direction, venting and draining of the heat exchanger is further facilitated.

The upstream header may be an upper header and the downstream header may be a lower header.

Each microchannel may extend from the position where it is open to the upstream header to the position where it opens into the downstream header in a single pass without meandering.

This facilitates a high heat absorption capacity and operation of the exchanger with a relatively low pressure drop across the exchanger, and also further facilitates venting and draining of the heat exchanger.

For the purposes of the present context, a microchannel will be deemed to be constituted by any passageway having an internal cross-sectional diameter or width of less than 3.5 mm. Preferably, the internal cross-sectional diameter or width of the microchannels is in the range from 0.5 mm to substantially 3.0 mm. More preferably, the internal cross-sectional diameter of width of the microchannels is substantially 1.1 mm or substantially 0.8 mm.

The interior of some or all of the microchannels may be rifled to give better heat transfer between the coolant and the microchannels.

One convenient construction for such a rear door heat exchanger is provided by having the channels provided by tubes.

The rear door heat exchanger may be rendered more efficient by means of strips of material extending transversely of and in thermal contact with the microchannels.

A good efficiency of the exchanger can be obtained if it comprises a metal or metal alloy. For example, the rear door heat exchanger may comprise aluminium. Advantageously, for the improvement of venting and draining of the channels, the upper header is the upstream header, although depending on site arrangement and performance requirements, the upstream header may be the lower header.

An example of a rear door heat exchanger embodying the present invention will now be described in greater detail with reference to the accompanying drawings, in which:

FIG. 1 shows a perspective view from one side and from above of a data centre incorporating rear door heat exchangers, each of which embodies the present invention;

FIG. 2 shows an underneath plan view of parts of the apparatus shown in FIG. 1;

FIG. 3 shows a perspective view from the rear, from one side and above of a part of the apparatus shown in FIGS. 1 and 2, with parts thereof drawn transparent to reveal other parts;

FIG. 4 shows a front elevational view of a part of the apparatus shown in FIG. 3 with parts thereof removed for clarity;

FIG. 5 shows a side elevational view of the part of the apparatus shown in FIG. 4, with a side thereof being removed to reveal further parts;

FIGS. 6a to 6c show cross-sectional views of three different embodiments of a part of apparatus shown in FIGS. 4 and 5; and

FIG. 7 shows an elevational front view of a part of the apparatus shown in FIGS. 4 and 5, on a larger scale;

FIG. 1 shows a data centre 100 provided with a chiller unit 110 connected to supply cooling water to perimeter cooling 120. The data centre 100 is provided with rows of blade racks 140, the blade racks 140 being provided with respective rear door heat exchangers 142. Chilled water from the chiller 110 is pumped through feed piping 143 to the perimeter cooling 120 and warm water returns from the perimeter cooling 120 to the chiller 110 through further piping 144.

The perimeter cooling 120, and the blade racks 140 with their rear door heat exchangers 142 rest on a raised floor 145. The blade racks 140 are arranged in rows 146. Air vents 148 are provided in the raised floor 145 in one or more aisles 150 between rows 146, with adjacent aisles 152 being without vents, so that aisles with vents alternate with those without. When the data center 100 is in use, warm air in a warm aisle 152 rises upwardly and draws with it through the racks 140 cool air from the adjacent cool aisles 150. This creates a continual draft of cool air through the racks 140. The warm air rises towards the ceiling of the data center and outwardly towards the perimeter cooling 120 where it is cooled and therefore falls downwardly to exit the perimeter cooling 120 underneath the raised flooring 145. This convection current continues with the cool air rising upwardly through the vents 148 to continue the air cooling cycle.

The rear door heat exchangers 142 provide additional cooling of the air flowing through the data center 100.

A coolant distribution unit 200 distributes coolant to the rear door heat exchangers 142. The manner in which it does this is more readily seen from FIG. 2. Thus, the coolant distribution unit 200 is connected to a primary coolant circuit 210 thermally coupled to a heat exchanger 212 of the coolant distribution unit 200, and a secondary coolant circuit 214 also coupled to the heat exchanger 212 of the coolant distribution unit 200 such that heat is transferred from the coolant in the secondary circuit 214 to the coolant in the primary circuit 210 when the apparatus is in operation. To this end coolant in the primary circuit 210 is pumped through the coolant distribution unit 200 as is coolant in the secondary coolant circuit 214.

Each rear door heat exchanger 142 is connected to receive coolant from the upstream side 216 of the secondary coolant circuit 214 by way of an upstream connector passageway 218 and to return coolant to the downstream side 220 of the secondary coolant circuit 214 by way of downstream connectors 222.

FIG. 2 also shows internal fans 224 of the blade racks 140 which urge air through the racks towards the rear door heat exchangers 142.

FIG. 3 shows outer panelling of a combination of a blade rack 140 and a rear door heat exchanger 142 mounted on the rear thereof. The latter is hinged to the rack 140 on the left-hand side thereof as viewed in FIG. 3. The rear panel 226 of the door 142 is perforated by a multiplicity of perforations 228 to enable air to pass through the rear door heat exchanger 142. Because the latter is hinged to the rack 140 it is openable to provide access both to the rear door heat exchanger 142 itself and to the rear of the rack 140.

Further features of each rear door heat exchanger 142 are evidence from FIGS. 4 and 5. Thus, it has a hinge 400 on its right-hand side as viewed in FIG. 4 and, in front of its rear panel 226 when viewed as in FIG. 4, an upstream header 402 to which is connected a vertically arranged part of the upstream connector 218, a lower downstream header 414 connected to a vertical part of the downstream connector 222 and a multiplicity of hollow bars or elongate extrusions 406 each providing a multiplicity of microchannels. They are substantially parallel to one another and are arranged vertically, having upper ends in fluid communication with the interior of the upper upstream header 402 and extending downwardly from there to their lower ends, without bends or meandering, which lower ends are in fluid communication with the interior of the lower downstream header 404. For the sake of clarity, not all of the microchannel extrusions 406 are shown, but only those to the left and to the right-hand sides of the rear door heat exchanger 142, the blank space between those illustrated being filled with such microchannel bars.

A bleeder valve 408 is provided in the top of the upper upstream header 402 and drain valve 410 is provided in the bottom of the lower downstream header 414.

Cooling U-shaped fins 412, only a few lines of which are shown diagrammatically in FIG. 4, each extend transversely of and are in thermal contact with the multiplicity of microchannel extrusions 406 at the base of the ‘U’ of the fins 412. Such fins 412 are present all the way from the tops of the microchannel extrusions 406 to the lower ends thereof.

FIG. 6a shows a cross-section of each microchannel extrusion 406. Thus each extrusion is an aluminium extrusion and is elongate in cross-section, being about 20 mm long and about 2 mm wide, with a multiplicity of microchannels 440 of generally rectangular cross section, the width of each of which is about 1.4 mm, the thickness of the walls 442 of the bar 406 being about 0.3 mm. The outer shape of each end channel in section is rounded, to follow the rounded ends 444 of the bar cross-section.

Each extrusion 406 is oriented so that its straight sides are generally parallel to the direction of flow of air through the heat exchanger 142.

FIG. 7 shows the fins 412 more clearly, this Figure showing a front view of an upper part of each heat exchanger 142. Fins of adjacent microchannel extrusions 406 interdigitate.

The vertical parts of the connectors 218 and 222, the headers 402 and 414, the microchannel extrusions 406 and the fins 412 are all made of aluminium. It will be appreciated therefore that because of the light weight aluminium used, the rear door heat exchanger 142 as a whole is relatively light. It is furthermore cheaper to construct and easier to install. Furthermore, the use of microchannels increases the outer surface area to internal volume ratio of the coolant passageways of the rear door heat exchanger 142. Furthermore, the use of vertically extending microchannels facilitates easy bleeding of air or other gases from the rear door heat exchanger by way of the valve 408 and easy drainage of liquid coolant from the rear door heat exchanger 142 via the valve 410. It will be appreciated that both the upper upstream header 402 and the lower downstream header 404 are common to all the microchannels 440.

When the apparatus is in use with air being circulated through the data center as described with reference to FIG. 1, and coolant being pumped through the primary circuit 210 and the secondary circuit 214, coolant from the upstream side of the secondary circuit 214 passes into the vertical part of the upstream connector 218 of each rear door heat exchanger 142 to its upstream header 142, from whence it descends through the microchannels of the microchannel bars 406 into the lower downstream header 404 and out through the vertical section of the downstream connector 222 into the downstream side 220 of the secondary circuit 214. Such passage of coolant through the rear door heat exchanger cools the air passing through the associated blade rack 140 as it passes through the rear door heat exchanger 142 and out through the perforated panel 326 into the warm aisle 152.

The coolant which may be used in each rear door heat exchanger 142 may comprise water, or R134a refrigerant (1,1,1,2-tetrafluoroethane). The latter may be present in biphase condition (both in liquid and gaseous phase) in the microchannels of the microchannel extrusions 406.

Numerous variations and modifications to the illustrated apparatus may occur to the reader without taking the resulting construction outside the scope of the present invention. For example, each of the microchannel extrusions may be provided with respective meandering strips instead of fins 412. Whilst the illustrated configuration calls for a relatively small pressure differential between upper header 402 and the lower header 404, the connections of the connectors 218 and 222 can be reversed, so that the former is connected to the downstream side 220 of the secondary circuit 214 and the connector 222 is connected to the upstream side 216 of the secondary circuit 214, so that coolant flows upwardly through the microchannels of the microchannel bars 406 instead of downwardly therethrough.

A preferred modified cross-section for the microchannel extrusion 406 is shown in FIG. 6b and is 16 mm long, 1.8 mm wide, with eight square-sectional microchannels each of 1.12 mm width, with slightly rounded corners, and two end microchannel sections being rounded on their outermost sides, the thickness of the walls of the bar being 0.34 mm.

Another preferred modified cross-section for the microchannel extrusion 406 is shown in FIG. 6c and is 25.4 mm long, and 1.3 mm wide. It also has ten microchannels, the middle eight of which are rectangular in section, with slightly rounded corners, and are 1.88 mm long and 0.76 mm wide. The two end microchannels are also rounded at their outermost ends. Thus the wall thickness of the bar along the longer sides of the rectangle is 0.27 mm, and the wall thickness of the bar between adjacent microchannels is 0.6 mm.

The rear door heat exchanger 142 could clearly be reconfigured to be hinged on the opposite side to that illustrated in the drawings.

Typically the temperature of the coolant in the upstream side 216 of the secondary coolant circuit 214 when the apparatus is in use will be substantially in the range from 10° C. to 25° C., preferably 15° C. to 20° C., more preferably 18° C. The temperature of the coolant in the downstream side 220 of the secondary coolant circuit 214 when the apparatus is in use will be substantially in the range from 20° C. to 35° C., preferably 25° C. to 30° C., more preferably 28° C.

The cooling duty for bars as shown in FIG. 6b in the apparatus of FIGS. 4 and 5 is substantially in the range from 10 to 30 litres per minute (l/m), preferably 15 to 25 l/m, more preferably 20 l/m. That for extrusions as shown in FIG. 6c is substantially in the range from 30 to 50 litres per minute (l/m), preferably 35 to 45 l/m, more preferably 40 l/m.

Claims

1. A rear door heat exchanger adapted to be mounted on a rear of a rack or other arrangement of heat-generating electronic equipment, and to cool air which passes therethrough when the rear door heat exchanger is in use, the exchanger comprising:

an upstream header;

a downstream header; and

a multiplicity of substantially parallel microchannels extending between and in fluid communication with both of the upstream header and the downstream header so such that both of the upstream and downstream headers are common to the microchannels of the multiplicity of microchannels.

2. A rear door heat exchanger according to claim 1, in which the microchannels extend in a direction which has at least a component in the vertical direction when the rear door heat exchanger is mounted ready for use.

3. A rear door heat exchanger according to claim 2, in which the microchannels are upright when the rear door heat exchanger is mounted ready for use.

4. A rear door heat exchanger according claim 1, wherein the upstream header is an upper header and the downstream header is a lower header.

5. A rear door heat exchanger according to claim 1, wherein each microchannel extends from the position where it is open to the upstream header to the position where it opens into the downstream header in a single pass without meandering.

6. A rear door heat exchanger according to claim 1, wherein each microchannel has an internal cross-sectional diameter or width of less than 3.5 mm.

7. A rear door heat exchanger according to claim 6, wherein the internal cross-sectional diameter or width of each microchannel is in the range from substantially 0.5 mm to substantially 3.0 mm.

8. A rear door heat exchanger according to claim 7, wherein the internal cross-sectional diameter or width of each microchannel is substantially 1.1 mm.

9. A rear door heat exchanger according to claim 7, wherein the internal cross-sectional diameter or width of each microchannel is substantially 0.8 mm.

10. A rear door heat exchanger according to claim 1, wherein the interior of at least one of the microchannels is rifled to give better heat transfer between the coolant and the microchannels.

11. A rear door heat exchanger according to claim 1, wherein the microchannels are provided by tubes.

12. A rear door heat exchanger according to claim 1, further comprising strips of material extending transversely of and in thermal contact with the microchannels.

13. (canceled)

14. (canceled)