CONDENSER AND COOLING DEVICE

The present invention relates to a condenser and a cooling device comprising the condenser, in particular a condenser and cooling device for cooling electronic devices, such as computers or servers, or flat screens, such as LCD, plasma or others, and the like.

There is a growing demand for cooling devices for cooling of electronic devices due to the increasing power consumption and consequently increased heat emission from such devices. Cooling devices for electronic devices are often limited in space due to e.g. cabinets and other units in the electronic device, and has to comply with strict rules of dimensions. Further, the directions of cooling air flow are limited due to the construction of the devices.

Accordingly, it is an object of the invention to provide an improved condenser and a cooling device for electronic devices, in particular for electronic devices having strict size requirements. In an aspect of the present invention, a condenser, e.g. for a cooling device, is provided, comprising a first header having a first port and extending along a first axis in a first plane, a second header having a second port and extending in the first plane, and at least one flat tube connecting the first header and the second header. The at least one flat tube comprises a first flat tube having a first side surface extending in the first plane.

Furthermore, a cooling device is provided, wherein the cooling device comprises a condenser as described herein and a first heat receiving part having a first inlet/outlet, wherein the first inlet/outlet is connected to the first port of the condenser via a first connecting channel. In an embodiment of the cooling device, the first heat receiving part may have a second inlet/outlet being connected to the second port of the condenser via a second connecting channel.

It is an important advantage of the present invention that the condenser and the cooling device provide efficient cooling of electronic devices in a limited space. The condenser and the cooling device according to the present invention are in particular useful for electronic devices comprising a member covering a surface area in a plane parallel to the first plane, where the member prevents airflow in a direction perpendicular to the first plane. Furthermore, it is desired that the electronic devices

are as flat as possible, i.e. that the devices have a small depth, which further strengthens the requirements.

It is a further advantage of the present invention that a condenser with a low resistance to airflows through the condenser in the direction of the first axis is provided, which enables low drop of pressure for a cooling air flow cooling the condenser in the direction of the first axis, i.e. along the first plane.

' BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become readily apparent to those skilled in the art by the following detailed description thereof, in particular by detailed description of exemplary embodiments thereof with reference to the accompanying drawings, in which:

Fig. 1 is a side view of an embodiment of a condenser according to the present invention,

Fig. 2 is a top view of the condenser in Fig. 1 , Fig. 3 is an enlarged view of Fig. 2,

Fig. 4 is a perspective view of the condenser in Fig. 1 ,

Fig. 5 shows a cross section of a flat tube of a condenser,

Fig. 6 is a side view of an embodiment of a condenser according to the present invention, Fig. 7 is a side view of an embodiment of a cooling device according to the present invention,

Fig. 8 is a perspective view of the cooling device of Fig. 7,

Figs. 9 -10 illustrate different ways of coupling a first tube of a cooling device to a first header of a condenser according to the present invention, Fig. 11 is a top view of an embodiment of a cooling device according to the present invention,

Fig. 12 is a side view of the cooling device of Fig. 11 ,

Fig. 13A and 13B are top views of a prior at condenser and a condenser according to the present invention, respectively, Fig. 14 is a partly top view of an embodiment of the condenser according to the present invention,

Fig. 15 is a partly top view of an embodiment of the condenser according to the present invention,

Fig. 16 is a partly top view of an embodiment of the condenser according to the present invention, Fig. 17 is a side view of an embodiment of a cooling device according to the present invention,

Fig. 18 is a perspective view of an embodiment of a cooling device according to the present invention,

Fig. 19 is a side view of the cooling device in Fig. 18, Fig. 20 is a schematical side view of an embodiment of a cooling device according to the present invention,

Fig. 21 is a partial cross section of the cooling device of Fig. 20,

Fig. 22 is a top view of an embodiment of a condenser according to the present invention Fig. 23 is a perspective view of the condenser of Fig. 22,

Fig. 24 is a perspective view of an embodiment of a cooling device according to the present invention,

Fig. 25 is a perspective view of an embodiment of a condenser according to the present invention, Fig. 26 is a perspective view of a cooling device according to the present invention,

Fig. 27 is a side view of an embodiment of a condenser according to the present invention, and

Fig. 28 is at partial cross section of the condenser in Fig. 27. DETAILED DESCRIPTION The figures are schematic and simplified for clarity, and they merely show details which are essential to the understanding of the invention, while other details have been left out. Throughout, the same reference numerals are used for identical or corresponding parts or features.

The condenser according to the present invention is a result of at completely new way of constructing a condenser. In the prior art, condensers for electrical devices are constructed for shortening the air flow distance in the condenser and for provision of a

flow area, i.e. the area of a cross section of the air flow path through the condenser, which flow area is as large as possible.

The condenser according to the invention does not follow this high principle. In the following, the present invention is described in relation to a conventional three dimensional Cartesian coordinate system with first axis X, second axis Y and third axis Z.

Fig. 1 shows a side view of an embodiment of a condenser according to the present invention. The condenser 2 comprises a first header 4 having a first port 5 and extending along a straight first axis X in a first plane spanned by the first axis X and a second axis Y. Further, the condenser 2 comprises a second header 6 having a second port 7 and extending in the first plane, preferably parallel to the first axis X as illustrated in Fig. 1. At least one flat tube connects the first header 4 and the second header 6, wherein the at least one flat tube comprises a first flat tube 8 having a first side surface extending in the first plane. Further, the condenser 2 comprises a second flat tube 10 and optionally a third flat tube 12, the flat tubes 8, 10, 12 connecting the first header 4 and the second header 6 in a parallel flow condenser configuration. The second flat tube 10 and the third flat tube 12 each have a first side surface extending in the first plane.

The condenser according to the present invention may comprise any suitable number of flat tubes connecting the first header and the second header, such as one, two, three, four, five, or more.

In an embodiment, the condenser may comprise one or more flat tubes having a first side surface extending in a second plane parallel to the first plane, e.g. at a distance between 5 mm and 2 cm, such as about 1 cm. One or more fins may extend between the one or more flat tubes in the first plane and the one or more flat tubes in the second plane.

In an embodiment, the condenser may comprise one or more flat tubes having a first side surface extending in a third plane parallel to the first plane, e.g. at a distance between 5 mm and 2 cm, such as about 1 cm. One or more fins may extend between the one or more flat tubes in the first plane and the one or more flat tubes in the third plane

The condenser may comprise one or more protective sheets, e.g. a first protective sheet and/or a second protective sheet, in order to e.g. increase the stability of the condenser and/or protect fragile parts of the condenser, such as cooling fins.

Fig. 2 and Fig. 3, which is an enlarged part of Fig. 2, show top views of the condenser 2 according to the invention. The condenser 2 comprises one or a plurality of first protective sheets 14 (not shown in Fig. 1), preferably extending in a plane parallel with the first plane. Further, the condenser 2 comprises one or a plurality of second protective sheets 16, preferably extending in a plane parallel with the first plane. Preferably, the first protective sheets 14 and the second protective sheets 16 are positioned on opposite sides of the at least one flat tube as illustrated in Fig. 2 and 3.

Protective sheets may be made of metal or alloys, preferably metal or alloys suited for brazing with aluminum. In an embodiment of the present invention, one or more of the protective sheets are made of plastic or other suitable materials. The cabinet of an electronic device may constitute a protective sheet. The protective sheets may be attached to the first and/or second header.

In order to increase the effective cooling surface area, the condenser according to the present invention may comprise one or more fins attached to the at least one flat tube. In an embodiment of the present invention, the fins are attached to a protective sheet. Preferably, the fins are arranged such that the flow resistance through the condenser along the first axis is as low as possible. Accordingly, the fins in a condenser according to the present invention may at least partly define or form one or more cooling air channels, preferably extending substantially parallel to the first axis. The cross section of the cooling air channels may have any suitable shape. In a preferred embodiment, the cooling air channels have a triangular cross section.

The condenser illustrated in Figs. 1-4 comprises first fins 18 (not shown in Fig. 1) between the flat tubes 8, 10, 12 and the first protective sheet 14. Further, the condenser 2 comprises second fins 20 (not shown in Fig. 1) between the flat tubes 8, 10, 12 and the second protective sheet 16. The first fins 18 are attached to the first side surface of the flat tubes 8, 10, 12 and the second fins are attached to the second side surface of the flat tubes 8, 10, 12. The fins 18, 20 may each be formed by one or more sheets of folded or stretch shaped metal, e.g. aluminum sheet with a thickness from about 0.05 mm to about 0.5 mm, e.g. 0.13 mm. The fins may be attached to a protective sheet.

The fins may be provided with small protrusions for providing a slightly turbulent cooling air flow through the cooling air channels.

It is an important advantage of the present invention that the condenser has a large cooling airflow cross section area.

The fins may have a fin pitch from about 1 to about 12 ribs/cm, such as 4 to 10 ribs/cm. In an embodiment, the fins have a fin pitch of about 7 ribs/cm.

Fig. 4 is a perspective view of the condenser 2 according to the invention. The condenser 2 comprises three first protective sheets 14 on a first side of the condenser and three second protective sheets 16 on a second side of the condenser 2. The flat tubes 8, 10, 12 and first and second fins 18, 20 reside between the first protective sheets 14 and the second protective sheets 16.

The first fins and/or the second fins may be divided into sets of fins, e.g. such that each flat tube is connected to separate first and/or second fins. Fins attached to one or more flat tubes may each be formed by one or more sheets.

A flat tube of the condenser defines one or more channels from the first header to the second header, such as two, three, four, five, six, seven, eight, nine, ten, or more channels, e.g. fifteen, twenty or more channels. Each channel may have a suitable cross section area, such as from about 1 mm ² to about 10 mm ² . Fig. 5 shows a cross section of an embodiment of a flat tube 22, e.g. the first flat tube 8, the second flat tube 10 and/or the third flat tube 12, employed in the condenser according to the invention. The flat tube 22 has a first side wall 24 with a first side surface and a second side wall 26 with a second side surface. The flat tube 22 has a height H of 20 mm and a width W of 1.8 mm. The flat tube 22 comprises six channels; however a flat tube with eight or ten channels and the same height and width may be preferred.

Preferably, the flat tubes employed in the present invention have as small width as possible to reduce the cooling air flow resistance through the condenser. At the same time a large surface area is desired in order to increase heat exchange between a cooling fluid in the flat tubes and the surrounding cooling air, and accordingly the height of the flat tubes are chosen as large as possible given the limited space for a cooling device in an electronic device.

Accordingly, flat tubes may have a height/width ratio of more than two, preferably more than four, e.g. about ten or more. The at least one flat tube may have a height from about 1 mm to about 1000 mm, preferably in the range from about 5 mm to about 100 mm, such as about 12 mm, 16 mm, 20 mm or 25 mm.

In general, the flat tubes are desired to have as low a width as possible to reduce the air flow resistance as earlier described; however the width must be large enough to provide a sufficient cross section area for passing cooling fluid in the tube. The at least

one flat tube may have a width from about 1 mm to about 10 mm, such as from about 1.5 mm to about 3 mm, e.g. about 1.8 mm.

In an embodiment of the present invention, the condenser comprises flat tubes of different dimensions, such as a first flat tube having a first height of e.g. 16 mm and a second flat tube having a second height of e.g. 22 mm.

The flat tubes may have a length more than 2 cm, preferably between 15 cm and 150 cm, e.g. about 35 cm.

Preferably, the flat tubes are straight. In an embodiment one or more flat tubes are slightly bent. The flat tubes and thus the fluid channels may be perpendicular to the first axis as illustrated in Figs. 1-4.

Fig. 6 illustrates an embodiment of a condenser according to the present invention. In the condenser 102 the first flat tube 8, the second flat tube 10, and the third flat tube 12, decline slightly, e.g. at an angle of about 88° with the first axis, from the first header 4 towards the second header 6 in order to assist cooling fluid flow from the first header 4 towards the second header 6.

Tests have shown that condensers with two or three flat tubes are preferred over four or more flat tubes along the first axis. For a condenser with a plurality of flat tubes, the distance between flat tubes is believed to cause slight turbulence in the cooling air flow, thereby increasing the heat transfer to the cooling air.

In the embodiment of Fig. 1 tests have shown that the first flat tube removes about

50% of the heat energy, the second flat tube removes about 35% of the heat energy, and the third flat tube removes about 15% of the heat energy.

The condenser and cooling device according to the present invention are in particular suitable for applications with limited cooling air flow due to noise requirements, e.g. applications where the cooling air flow through the condenser is smaller than 34 m ³ pr hour, such as between 7 and 20 m ³ pr hour, and the noise is less 25 dB(A), e.g. less than 15 dB(A).

During use of the condenser, the condenser may be tilted such that the first plane form an angle compared to vertical, e.g. an angle from about 0° to about 80°, such as from about 0° to about 45°, e.g. 2° to 10°. In general, the condenser may during use be oriented to facilitate cooling fluid flow in a desired direction.

In an embodiment of a cooling device, the condenser may during use be oriented such that the first plane is substantially parallel to horizontal.

The first and/or the second header may be tubular, preferably with circular or oval cross section in order to withstand high pressure of up to 110 bar, or more. In an embodiment of the condenser, the first and/or the second header may have a quadrangular cross section, e.g. along the first axis. The first header and/or the second header may have a suitable cross sectional area, such as from about 0,5 cm ² to about 10 cm ² , preferably from about 1 cm ² to about 5 cm ² , e.g. about 3 cm ² .

Figs. 7 and 8 show an embodiment of a cooling device according to the present invention. The cooling device 200 comprises a condenser 2, a first heat receiving part 202 having a first inlet/outlet 204 and a second inlet/outlet 206, wherein the first inlet/outlet is connected to the first port 5 of the condenser 2 and the second inlet/outlet is connected to the second port 7 of the condenser via a first connecting channel 208 and a second connecting channel 210, respectively. The first connecting channel 208 and the second connecting channel 210 are tubes. In an embodiment with only one heat receiving part, the second inlet/outlet 206 is connected directly to the second connecting channel 210.

The condenser 2 may be replaced by any of the condensers 2', 2", 102, 302, 502, 602 or 702 described below. The cooling device according to the invention may comprise any number of heat receiving parts connected either in series and/or in parallel with the condenser according to the invention.

For example, the cooling device may further comprise a second heat receiving part as illustrated by heat receiving part 212 in Figs. 7 and 8, the second heat receiving part 212 having a third inlet/outlet 214 and a fourth inlet/outlet 216 connected to the second inlet/outlet 206 and the second port 7, respectively.

The condenser according to the invention is particular suited for a cooling device with a closed cooling fluid loop as illustrated e.g. in Figs. 7 and 8. In the cooling device according to the invention, the first heat receiving part is adapted to receive heat from a heat generating element, e.g. a chip or other electronic circuit. The heat from the heat generating element heats cooling fluid in the cooling device causing the heated cooling fluid in liquid and/or gaseous form to flow into the first connecting channel and into the condenser via the first port. The cooling fluid is cooled in the condenser and leaves the condenser via the second port of the second header. The cooled fluid returns to the at least one heat receiving part via the second connecting channel and the process is

repeated. The cooling device may be a closed cooling device, i.e. cooling fluid in the system is not in contact with the surroundings.

The cooling fluid in the cooling device consists of a single fluid or comprises two or more fluids. The fluids in the cooling fluid may be soluble within each other. The cooling fluid may comprise one or more of water, ethanol, methanol, CO ₂ , propane, ammonia, fluorine compounds, such as 3M® FC72 and 3M® FC82, or other fluids having suitable thermal and physical properties.

Examples of cooling fluids include but are not limited to HydroFluoroEther (HFE) cooling fluids, such as 3M® HFE-7000, HFE-7100, HFE-72DA, or other cooling fluids, e.g. 1 ,1 ,1 ,2-Tetrafluoroethane (also known as R134A), 1,1 ,1,3-tetrafluoro-2-propene (also known as HFO 1234 ZE) and the like.

Figs. 9 and Fig. 10 illustrate different ways of coupling the first header of a condenser according to the present invention to a first heat receiving part of a cooling device according to the invention. In Fig. 9, a first tube, e.g. first tube 208, extends through the first port 5 of the condenser and into the condenser in order to prevent condensed cooling fluid to flow back into the first tube and into the first heat receiving part 202 thereby ensuring a one way cooling fluid flow in the cooling device. In Fig. 10, an end of the first tube 208 is attached to the first port 5. The embodiment of Fig. 9 is in particular suitable when cooling fluid in liquid form is to be circulated in the cooling device.

Fig. 11 is a top view of an embodiment of a cooling device 300 according to the invention. The condenser 302 comprises a first header 4 and a second header 6. Fig. 12 is a side view of the cooling device in Fig. 11. In the cooling device 300, a first tube 304 constitutes the first header 4 and the first connecting channel 208, and a second tube 306 constitutes the second header 6 and the second connecting channel 210 further reducing the number of parts and thereby a reduction in production costs.

Preferably, the cooling device is substantially evacuated before entrance of the cooling fluid into the cooling device to avoid presence of air or any other undesired gases in the cooling device. Air or undesired gases may react with the selected cooling fluids, and presence of undesired gases may decrease the efficiency of the cooling device by occupying volume in the cooling device. Upon evacuation, the cooling fluid is entered into the cooling device and the device is hermetically sealed.

The cooling device may be closed with a closure e.g. in the form of a mechanical valve and/or a welded or brazed closure. The closure may reside in any suitable part of the

cooling device, preferably at/in the end or at the top of a header. In other embodiments, the closure may be positioned in a connecting tube or in a heat receiving part.

The condenser according to the invention may have any suitable dimensions in order to fulfill size requirements. The condenser may have a first side length, e.g. length along the first axis, from about 2 cm to about 100 cm, such as from about 5 cm to about 20 cm, preferably about 7 cm. Further, the condenser may have a second side length, e.g. length along the second axis, from about 4 cm to about 150 cm, such as about 35 cm.

The condenser according to the present invention is in particular suitable for applications imposing strict requirements on the thickness of the condenser.

Accordingly, the condenser may have a third side length, e.g. length along the third axis, from about 5 mm to about 3 cm, preferably about 2 cm.

The cooling device is able to remove high power at low pressure drop over the condenser at a low noise level. A cooling device with at condenser measuring 70 mm X 350 mm X 20 mm has proven to remove 160W with a pressure drop less than 1 Pa, cooling air flow about 8 m ³ pr. hour and a noise level less than 25 dB(A).

It is an important advantage of the present invention that the condenser and the cooling device may be built from a small number of standard components leading to a further reduction in production costs. The condenser may in use operate partly or fully as a radiator.

The condenser according to the invention has a large cooling air cross section area compared to known cooling devices for electronic devices as illustrated in Fig. 13 showing a top view of a prior art tube condenser 400 with tube 402 and fins 404 (Fig. 13A) and a condenser according to the present invention (Fig. 13B). Fig. 14 illustrates a partly top view of an embodiment of the condenser according to the present invention. The condenser 502 comprises a first flat tube (not shown) and a second flat tube 10 having a first side surface extending in a first plane, and a fourth flat tube (not shown) and a fifth flat tube 30 having a first side surface extending in a second plane parallel to the first plane. In the illustrated embodiment, second fins 20 are placed between the tubes in the first and second plane. Furthermore, the condenser 502 comprises third fins 32 between the flat tubes extending in the second plane and the second protective sheet 16. The condenser 502 may comprise a third flat tube extending in the first plane and/or a sixth flat tube extending in the second plane. The distance between the tubes in the first plane and the tubes in the second plane

may range from about 5 mm to about 2 cm, such as about 8 mm as illustrated in Fig. 14.

Rg. 15 illustrates a partly top view of an embodiment of the condenser according to the present invention. The condenser 602 comprises a first flat tube (not shown) and a second flat tube 10 having a first side surface extending in a first plane, and a fourth flat tube (not shown) and a fifth flat tube 30 having a first side surface extending in a second plane parallel to the first plane. Further, the condenser 602 comprises a seventh flat tube (not shown) and an eighth flat tube 34 having a first side surface extending in a third plane parallel to the first plane. In the embodiment in Fig. 15, second fins 20 are positioned between the tubes in the first and second plane, and first fins 18 are positioned between the tubes in the first and third plane. In the embodiment in Fig. 15, the tubes in the second and third plane function as protective sheets.

Fig. 16 illustrates a partly top view of an embodiment of the condenser according to the present invention. The condenser 702 comprises a second flat tube 10 in a first plane and a fifth flat tube 30 in a second plane. First fins 18 are positioned between the first flat tube and the second flat tube forming cooling air channels parallel to the first axis X.

The cooling device according to the invention may form a closed loop. Fig. 17 schematically illustrates an embodiment of a cooling device according to the present invention. In the cooling device 800, a condenser 802 according to the present invention, e.g. as illustrated in Figs. 1-4, Fig. 6 and/or Figs. 14-16, is connected to a first heat receiving part 804 by a first tube 806 in a thermo siphon configuration. The second port 808 of the condenser 802 is sealed. During use of the cooling device 800, cooling fluid evaporates and moves from the first heat receiving part 804 via the first tube 806 into the condenser at the first port 810 in the first header 812. Subsequently, cooling fluid condenses in the condenser 802 and flows back into the first heat receiving part 804 via the first tube 806 due to gravity. During use, the condenser 802 may be slightly tilted such that flow of condensed cooling fluid towards the first port 810 is facilitated.

Figs. 18 and 19 schematically illustrate an embodiment of a cooling device according to the invention. The cooling device 900 is in particular adapted for use in electronic devices that are to be mounted in a rack, e.g. a XU rack, such as a 1 U rack. During use, the first plane is horizontally oriented or slightly tilted relative to a horizontal plane. The condenser may be slightly tilted for gravity-assisted flow of cooling fluid. In the

illustrated embodiment, the cooling device is mounted in such a way that the first plane is substantially parallel or forms a small angle, e.g. less than 5°, with a horizontal plane. The first port 204 and the second port 206 are positioned in the first heat receiving part 202 in such a way that the first port is positioned above the second port during use. Thereby a one way cooling fluid flow is facilitated. The arrows indicate the flow direction of the cooling fluid during use.

Figs. 20 and 21 schematically illustrate an embodiment of a cooling device according to the present invention. In the cooling device 1000, a condenser 1002 according to the present invention is connected to a first heat receiving part 1004 by a first tube 1006 from a first port 1008 in the first header 1010 to a first inlet/outlet 1012 in the first heat receiving part 1004. Further, a second tube 1014 connects a second port 1016 in the first header 1010 to a second inlet/outlet 1018 in the first heat receiving part 1004.

As best seen in Fig. 21 illustrating a partial cross section of the cooling device 1000, the first tube 1006 extends into the first header such that the end 1020 of the first tube is positioned above the end 1022 of the second tube 1014. Hereby, a cooling fluid flow as illustrated by the arrows in Fig. 20 is facilitated, since condensed, i.e. liquid, cooling fluid is forced towards the second port 1016 by gravity. The condenser 1002 may be tilted to facilitate liquid cooling fluid flow towards the second port. The first tube 1006 may have a diameter different from the diameter of the second tube 1014. In an embodiment, the one or more protective sheets may extend along a curved surface, e.g. in order to fit with an inner surface of a cabinet of an electronic device. This may have the advantage of allowing a larger fin area thus utilizing a higher percentage of the free space in the cabinet. Curved protective sheets may provide that the fin area can be increased for a given geometry of a cabinet, consequently leading to improved cooling capability of the condenser.

Fig. 22 is a top view of a condenser 2' similar to the condenser 2 of Figs. 1-4. The condenser 2' comprises a first protective sheet 14' extending along a first curved surface. In an embodiment of the condenser 2', e.g. as illustrated, cross-sections of the first protective sheet 14' taken along the first axis X are substantially identical. The condenser 2' comprises a plane second protective sheet 16. In an embodiment of the condenser, the condenser may comprise second protective sheet(s) extending along a second curved surface. The first protective sheet(s) 14' and the second protective sheet(s) 16 are positioned on opposite sides of the at least one flat tube.

The protective sheet(s) may have one or more openings or holes. A mesh or net may constitute a protective sheet.

Fig. 23 is a perspective view of the condenser 2', and Fig. 24 is a perspective view of a cooling device 200' comprising the condenser 2'.

Fig. 25 is a perspective view of an embodiment of the condenser according to the present invention. The condenser 2" comprises a first flat tube 8 extending in a first plane and a second flat tube 10 extending in a second plane parallel to the first plane. Further, the condenser 2" comprises a first protective sheet 14 and a second protective sheet 16. First fins 18 are positioned between the first protective sheet 14 and the first flat tube 8, second fins 20 are positioned between the first flat tube 8 and the second flat tube 10, and third fins 32 are positioned between second flat tube 10 and the second protective sheet 16. The first flat tube 10 has a first height of 16 mm and the second flat tube 10 has a second height of 22 mm. The first header 4 and the second header 6 have a substantially quadrangular cross section along the first axis.

Fig. 26 is a perspective view of a cooling device 200" comprising the condenser 2".

The system pressure varies during use of the cooling device. The system pressure may in resting condition (25 ⁰ C) be above or below atmospheric pressure. In an embodiment, the cooling device may in resting condition (25 ⁰ C) have a system pressure larger than atmospheric pressure, e.g. larger than 5 bar, such as about 8 bar. Larger system pressures in resting condition may be contemplated.

The system pressure may in resting condition (25 ⁰ C) be less than 1 bar, e.g. less than 0.5 bar, such as about 0.25 bar.

During manufacturing, the filling of the cooling device with cooling fluid may be difficult to control in a precise and effective manner. In order to facilitate filling the cooling device to obtain a desired cooling fluid liquid level, a cooling fluid reservoir may be formed or comprised in the cooling device, e.g. in the second header of the condenser or along the second connecting channel. Accordingly, the second header may extend below the first header in the condenser. The second header may have a larger cross- sectional area than the tube forming the first connecting channel to the first header. Thus, filling of cooling fluid in the condenser device to a cooling fluid level falling within a desired range in the first connecting channel is facilitated by the second header extending below the first header.

The first and second header may have different sizes and geometry. The second header may have a length larger than the length of the first header.

Figs. 27 and 28 illustrate an embodiment of the condenser. The second header 6 extends below the first header 4 providing a cooling fluid reservoir having a larger cross

sectional area than the first connecting channel 208 at the same level along the first axis. The larger total cross section area of the cooling device at desired cooling fluid level (dotted lines in the condenser and connecting channel) enables better control of the cooling fluid level during manufacture. In an embodiment, the cooling fluid reservoir may be positioned along the second connecting channel at a desired cooling fluid level.

In specific embodiments, the present invention relates to the following items: 1. A condenser for a cooling device, comprising

- a first header having a first port and extending along a first axis in a first plane,

- a second header having a second port and extending in the first plane, and

- at least one flat tube connecting the first header and the second header, wherein the at least one flat tube comprises a first flat tube having a first side surface extending in the first plane. 2. A condenser according to item 1 , wherein the at least one flat tube connecting the first header and the second header comprises a second flat tube having a first side surface extending in the first plane.

3. A condenser according to any of the preceding items, wherein the at least one flat tube connecting the first header and the second header comprises a third flat tube having a first side surface extending in a second plane parallel to the first plane.

4. A condenser according to any of the preceding items, wherein the at least one flat tube connecting the first header and the second header comprises a fourth flat tube having a first side surface extending in a second plane parallel to the first plane.

5. A condenser according to any of the preceding items, wherein the first header and the second header are tubular.

6. A condenser according to any of the preceding items, wherein the at least one flat tube each comprises a number of fluid channels.

7. A condenser according to any of the preceding items, wherein the at least one flat tube is straight. 8. A condenser according to any of the preceding items, further comprising a first protective sheet.

9. A condenser according to item 8, wherein the first protective sheet extends in a plane parallel with the first plane.

10. A condenser according to item 8, wherein the first protective sheet extends along a curved first surface. 11. A condenser according to any of the items 8-10, further comprising a second protective sheet.

12. A condenser according to item 11, wherein the second protective sheet extends in a plane parallel with the first plane.

13. A condenser according to any of the items 11-12, wherein the first protective sheet and the second protective sheet are positioned on opposite sides of the at least one flat tube.

14. A condenser according to any of the preceding items, further comprising one or more fins attached to the at least one flat tube.

15. A condenser according to item 14, wherein the one or more fins define one or more cooling air channels that extend substantially parallel to the first axis. The fins may have a fin pitch from about 1 to about 12 ribs/cm, e.g. about 7 ribs/cm.

16. A condenser according to any of the preceding items, the condenser having a first side length from about 2 cm to about 100 cm, preferably about 7 cm.

17. A condenser according to any of the preceding items, the condenser having a second side length from about 4 cm to about 150 cm, such as about 35 cm.

18. A condenser according to any of the preceding items, the condenser having a third side length from about 5 mm to about 3 cm, preferably about 2 cm.

19. A condenser according to any of the preceding items, wherein the at least one flat tube has a height from about 1 mm to about 1000 mm, preferably in the range from about 5 mm to about 100 mm, such as about 12 mm, 16 mm, 20 mm or 25 mm.

20. A condenser according to item 19, wherein the at least one flat tube comprises a first flat tube having a first height and a second flat tube having a second height different from the first height.

21. A condenser according to any of the preceding items, the condenser having a ratio between the first side length and the third side length of more than two, preferably more than four.

22. A condenser according to any of the preceding items, the condenser comprising a cooling fluid reservoir in the second header.

23. A cooling device comprising a condenser according to any of the preceding items and a first heat receiving part having a first inlet/outlet, wherein the first inlet/outlet is connected to the first port of the condenser via a first connecting channel.

24. A cooling device according to item 23, wherein the first heat receiving part has a second inlet/outlet connected to the second port of the condenser via a second connecting channel.

25. A cooling device according to any of items 23-24, wherein the first inlet/outlet is connected to the first port by a first tube forming the first connecting channel.

26. A cooling device according to any of items 24-25, wherein a second tube is connected to the second port forming at least a part of the second connecting channel.

27. A cooling device according to any of items 23-26, wherein the cooling device further comprises a second heat receiving part having a third inlet/outlet and a fourth inlet/outlet connected to the first port and the second port, respectively.