WO2012173509A1

WO2012173509A1 - Apparatus comprising a housing and passive cooling

Info

Publication number: WO2012173509A1
Application number: PCT/RU2011/000420
Authority: WO
Inventors: Vitaly Vladimirovich Malinin
Original assignee: Siemens Aktiengesellschaft
Priority date: 2011-06-16
Filing date: 2011-06-16
Publication date: 2012-12-20

Abstract

An apparatus comprises a housing with a closable air throughlet. A first temperature switch is coupled to the closable air throughlet in order to open or close the air throughlet depending on a temperature.

Description

Apparatus comprising a housing and passive cooling

The present invention relates to an apparatus comprising a housing with a closable air throughlet according to the preamble of claim 1.

Apparatuses comprising a housing with a heat source arranged therein have to be cooled in most cases in order to avoid heat accumulation within the housing and overheating caused as a result. The heat source may e.g. be an electric device.

A cooling of the apparatus requires that the heat generated by the heat source be dissipated from the housing to the apparatus's surroundings. It is a known measure to provide the housing with air throughlets for this purpose. The heat generated by the heat source then produces a convective flow of heat through the air throughlets so that hot air from within the housing is exchanged for cooler air f om the housing' s surroundings .

In many apparatuses, components arranged within a housing of the apparatus do not only have to be kept below a maximum temperature, but also above a minimum temperature. If the ambient temperature of the apparatus is very low and a heat source arranged within the housing of the apparatus generates only a small amount of heat, air throughlets provided in the housing may result in a drop of temperature within the housing to a value below the admissible minimum.

Apparatuses exist in which heat sources arranged within a housing generate alternating thermal outputs over time. If, for example, an electric component arranged within a housing of an apparatus is periodically switched on for only short periods of time, and if the electric component produces a large thermal output during these short periods of time, large temperature fluctuations may occur within the housing over time which are detrimental to the apparatus's operating life. For this reason, it is desirable to curb the temperature fluctuations within the housing.

In order to reduce temperature fluctuations in housings, it is known to arrange active cooling devices within the housing, to couple these active cooling devices with temperature sensors and to operate the cooling devices depending on a temperature within the housing. Such cooling devices may e.g. comprise ventilators. However, such solutions depend upon external power supply and are expensive and fault-prone due to their complexity.

It is the object of the present invention to provide an improved apparatus comprising a housing with a closable air throughlet. This object is solved by an apparatus with the features of claim 1. Preferred embodiments are indicated in the dependent claims .

An apparatus according to the invention comprises a housing having a closable air throughlet. Thereby, a first temperature switch is provided and coupled to the closable air throughlet in order to open or close the air throughlet according to a temperature. In such an apparatus, the air throughlet may advantageously be opened if a temperature within the housing is too high, whereas the air throughlet may be closed if a temperature within the housing is too low.

It is preferred that the air throughlet may be closed by means of a flap. Advantageously this allow for a simple mechanical construction.

In a further embodiment of the apparatus, a baffle is arranged within the housing which may adopt a first position and a second position in order to influence a convective heat flow within the housing. Thereby, a second temperature switch is provided and coupled to the baffle in order to move the baffle to the first or to the second position depending on a temperature. Advantageously, the baffle allows for influencing a convection within the housing in order to increase or reduce the heat exchange within the housing and between the housing and the housing's surroundings.

The first temperature switch and/or the second temperature switch are preferably arranged within the housing. Advantageously, the first temperature switch and/or the second temperature switch may then manipulate the closable air through- let and/or the baffle depending on a temperature within the housing .

In a particularly preferred embodiment, the first temperature switch and/or the second temperature switch are passive me- chanical components. Advantageously, the first temperature switch and/or the second temperature switch do not require a separate power supply.

In an embodiment of the apparatus, the first temperature switch and/or the second temperature switch comprise a bimetal. Advantageously, the bimetal changes depending upon a temperature and allows for the temperature switch to operate the air throughlet or the baffle. In a particularly preferred embodiment, the flap and/or the baffle comprise a bimetal. Advantageously, the flap itself may then be formed by the bimetal. This allows for a particularly inexpensive and fail-safe solution which gets by with a minimum amount of components.

In a different embodiment of the apparatus, the first temperature switch and/or the second temperature switch comprise a container filled with fluid, the volume of which changes depending on a temperature. Advantageously, such a container filled with a fluid forms a robust and inexpensive temperature switch. Preferably, isobutane is used as a fluid. Advantageously, isobutane is subject to a considerable change in volume in a temperature range relevant for many applications. For this reason, the container filled with isobutane is able to form a temperature switch having a large contact travel.

In an embodiment of the apparatus, the first temperature switch and the flap and/or the second temperature switch and the baffle are coupled by means of a movable plunger. Advantageously, the plunger may then transfer a change in shape of the temperature switch caused by the temperature fluctuation into a switching movement acting on the flap or baffle.

In a preferred embodiment, a heat source is arranged within the housing. Advantageously, heat produced by this heat source may then be removed from the housing.

In an embodiment of the apparatus, the heat source is an electric device. Advantageously, the apparatus may then be an electric apparatus.

In a further embodiment of the apparatus, the electric device is configured to be switched on and off periodically. Advantageously, even a non-constant operation of the electric device does not cause thermal problems inside the apparatus.

In a further embodiment of the apparatus, the heat source is configured to emit a time-variable thermal output. Advantageously, even a non-constant heat production does not cause thermal problems inside the apparatus.

The above-mentioned properties, features and advantages of this invention as well as a preferred way of achieving these, will become more clear in conjunction with the following description of preferred embodiments, which are illustrated in conjunction with figures, in which: Figure 1 is a perspective and semi-transparent depiction of an apparatus;

Figure 2 is a sectional view of the apparatus;

Figure 3 is a schematic depiction of a flap in a first position;

Figure 4 is a schematic depiction of the flap in a second po- sition;

Figure 5 is a schematic view of a baffle in a second position; Figure 6 is a schematic view of a baffle in a first position;

Figure 7 is a schematic view of a container filled with a fluid; Figure 8 is a schematic view of a bimetal;

Figure 9 is a schematic view of a natural convective heat flow in a housing; Figure 10 is a schematic view of a first convective heat flow;

Figure 11 is a schematic view of a second convective heat flow; and

Figure 12 is a schematic view of a third convective heat flow.

Figure 1 is a schematic, perspective and semi-transparent view of an apparatus 100. Figure 2 also shows a schematic sectional view of an apparatus 100. The apparatus 100 comprises an essentially closed housing 200 in which a plurality of heat sources 110 is arranged. The heat sources 110 may be any kind of electric, electronic or mechanical components. The heat sources 110 may also be chemical heat sources or any other kind of heat sources. The number of heat sources 110 may be selected as desired, depending on the intended application. It is also possible that only one heat source 110 is provided. The apparatus 100 may e.g. be a computer, an amplifier or any other type of device.

The heat sources 110 of the apparatus 100 may be operated continuously and produce heat continuously. However, it is also possible that the heat sources 110 are only activated for limited periods of time and produce heat only during these periods. The thermal output generated within the housing 200 of the apparatus 100 may in this case be subject to strong time fluctuations.

The heat sources 110 arranged within the housing 200 of the apparatus 100 may have a limited admissible temperature range for operating the heat sources 110. In this case, a temperature within the housing 200 must not fall below a previously determined minimum temperature or exceed a previously determined maximum temperature. An ambient temperature in the surroundings of the housing 200 may be below the minimum temperature or between the minimum and maximum temperature. A temperature in the surroundings of the housing 200, however, must as a rule not exceed the maximum temperature in order to avoid overheating of the heat sources 110 in the housing 200.

A heat exchange in the housing 200 of the apparatus 100 takes place according to three different physical principles. First of all, a heating of the air within the housing 200 caused by the heat sources 110 results in a convective heat flow in which warm air within the housing 200 rises and colder air within the housing 200 drops. Figure 9 shows a schematic view of the natural convective heat flows resulting therefrom. Within the housing 200, the convective heat flows 300 lead to a mixing of air portions with varying temperatures and thus to a heat transport from the heat sources 110 to the cooler areas within the housing. Cooler areas may e.g. occur at the walls of the housing 200.

Moreover, a heat exchange by heat conduction takes place within the housing 200. Thereby, heat is transferred on the molecular level by means of surges. By means of this mechanism, heat may e.g. be transferred by the warmer air within the housing 200 to the cooler walls of the housing 200.

A third heat exchange mechanism occurring in the apparatus 100 is thermal radiation. In this connection, large surfaces emit heat in the form of infrared radiation. The amount of thermal radiation thereby depends upon the temperature difference between the hot surface and the surroundings of the hot surface as well as on the surface properties of the hot surface. By means of thermal radiation, the heat sources 110 may e.g. transfer heat to the air within the housing 200 as well as to the walls of the housing 200. Moreover, the walls of the housing 200 may give off heat to the surroundings of the housing 200 by means of thermal radiation.

Among the aforementioned heat exchange mechanisms, convection is most effective. However, in the case of a housing 200 completely sealed off against the surroundings, no air exchange may occur between the inside of the housing 200 and the surroundings of the housing 200. For this reason, the housing 200 of the apparatus 100 comprises a plurality of the air throughlets 210. In detail, the housing 200 exemplified in Figure 1 comprises a first air throughlet 211, a second air throughlet 212, a third air throughlet 213, a fourth air throughlet 214 and a fifth air throughlet 215. However, more or less than five air throughlets 210 may be provided. The first air throughlet 211 and the second air throughlet 212 are arranged in a lower area of the housing 200. The third air throughlet 213 and the fourth air throughlet 214 are arranged in a central area of the housing 200. The fifth air throughlet 215 is arranged in an upper area of the housing 200. The air throughlets 210 may, however, be arranged in other locations within the housing 200, as well.

By means of convection, an air exchange may take place be- tween the inside of the housing 200 and the surroundings of the housing 200 via the air throughlets 210 in the walls of the housing 200. This results in an effective heat exchange between the inside of the housing 200 and the surroundings of the housing 200.

If, however, the ambient temperature surrounding the housing 200 of the apparatus 100 is below the admissible minimum temperature for operating the heat sources 110, an excessive heat exchange between the inside of the housing 200 and the surroundings of the housing 200 may lead to a cooling within the housing 200 to a temperature below the admissible minimum. This is particularly the case if the heat sources 100 temporarily generate only a small amount of heat or none at all. For this reason, it is necessary to be able to adjust the air exchange caused by the convective heat flow between the inside of the housing 200 and the surroundings of the housing 200.

For this purpose, the air throughlets 210 of the housing 200 are configured in a closable manner. The closable air throughlets 210 may e.g. be provided with flaps or slides in order to open and to close the air throughlets 210. In a strongly diagrammed view, Figures 3 and 4 show a possibility of configuring air throughlets 210 which may be closed by means of flaps. The Figures each depict the housing 200 of the apparatus 100 comprising an air throughlet 210 arranged at a flap 230. The flap 230 may adopt a first position 231 as depicted in Figure 3, in which the air throughlet 210 is closed by the flap 230. Moreover, the flap 230 may assume a second position 232 as depicted in Figure 4, in which the air throughlet 210 is not closed by the flap 230, but open. In the embodiment example shown in Figures 3 and 4, the flap 230 is arranged at the outer face of the housing 200. Of course, it is also possible to arrange the flap 230 at an inner face of the housing 200.

If an ambient temperature surrounding the housing 200 is very low and the heat sources 110 only produce a low amount of thermal output, an excessively strong cooling within the housing 200 may occur between the housing 200 and the sur- roundings of the housing 200 even in the case of closed air throughlets 210 due to the convective heat flow within the housing 200 and due to the heat exchange caused by heat conduction between the air within the housing 200 and the walls of the housing 200.

In order to avoid this, the housing 200 of the apparatus 100 comprises a plurality of baffles 220 depicted in Figure 2 which serve to suppress the convection within the housing 200. In detail, in the schematic view of Figure 2, the hous- ing 200 comprises a first baffle 221, a second baffle 222, a third baffle 223 and a fourth baffle 224. The baffles 220 are each arranged at the inner faces of the housing 200. In the depicted embodiment, the first baffle 221 and the second baffle 222 are arranged in a central area of the housing 200 and the third baffle 223 and the fourth baffle 224 are arranged in an upper area of the housing 200. The housing 200, however, may comprise more or less baffles 220, which may also be arranged at different locations within the housing 200. As shown in a strongly diagrammed view in Figures 5 and 6, each of the baffles 220 may adopt two different positions. Figures 5 and 6 each show a section through the housing 200 of the apparatus 100 and a baffle 220 arranged therein at a wall of the housing 200. In a second position 226 depicted in Figure 5, the baffle 220 is essentially in parallel to a wall of the housing 200 at said wall of the housing 200. In a first position 225 depicted in Figure 6, the baffle 220 sticks out from the wall of the housing 200 in an essentially vertical manner and extends into the interior of the housing 200.

It would be possible to operate the baffles 220 and the flaps 230 by means of actuators which are in turn coupled to thermal sensors, in order to adjust the baffles 220 and the flaps 230 in accordance with a temperature measured within the housing 200. Such actuators and sensors, however, require a power supply, they are expensive and fault-prone. According to the invention, it is therefore provided to adjust the baffles 220 and the flaps 230 by means of passive mechanical temperature switches. Suitable for this is any element which sufficiently changes its shape depending on a temperature in order to effect an adjustment of the baffles 220 and the flaps 230.

Figure 7 is a schematic view of a potential configuration of a temperature switch. The Figure depicts a baffle 220 or a flap 230 which may be moved around a joint 243. The baf- fle/flap 220, 230 is coupled to a container 240 via a plunger 242, the container being filled with fluid 241. The fluid 241 is a liquid or a gas, the volume of which changes depending on the temperature of the fluid 241. It is particularly favorable if the temperature of the fluid 241 is within a range relevant for the operation of the apparatus 100 which approximates the phase transition threshold between the liquid and the gaseous phase. The fluid 241 may e.g. be isobutane.

A change in fluid density 241 caused by a temperature modifi- cation results in a change in volume of the container 240 which in turn leads to a displacement of the plunger 242, which moves the flap/baffle 220, 230 between its first position 225, 231 and its second position 226 232. By choosing the suitable fluid 241 as well as the geometrical dimensions of the container 240, the plunger 242 and the flap/baffle

220, 230, the system depicted in Figure 7 may be adjusted in such a way that the flap 220, 230 is moved to the first position 225, 231 when dropping below a predetermined minimum temperature and to the second position 226, 232 when exceeding a predetermined maximum temperature.

Of course, the container 240 holding the fluid 241 may be coupled to the flap/baffle 220, 230 in a different manner than by means of the plunger 242. For this purpose, a variety of possibilities comprised by the tenor of the present invention is obvious to the person skilled in the art. Figure 8 depicts a strongly diagrammed view of a second possibility of configuring the temperature switch. The Figure shows a flap/baffle 220, 230 which may be moved around a joint 253. The flap/baffle 220, 230 is coupled to a bimetal 250 via a plunger 252. The bimetal 250 is in the shape of a bimetallic strip comprising two layers of different metals having differing thermal expansion coefficients provided in a sandwich arrangement.

Due to the different thermal expansion of the two metals of the bimetal 250, a temperature change of the bimetal 250 results in a reversible deformation of the bimetal 250. The deformation of the bimetal 250 is transferred to the

flap/baffle 220, 230 by means of the plunger 252 in order to move the flap/baffle 220, 230 between the first position 225, 231 and the second position 226, 232. By suitably choosing the bimetal 250 and the geometrical dimensions of the bimetal 250, the plunger 252 and the flap/baffle 220, 230, the system depicted in Figure 8 may be adjusted in such a way that the bimetal 250 moves the flap 220, 230 into the first position 225, 231 when dropping below a predetermined minimum temperature and into the second position 226, 232 when exceeding a predetermined maximum temperature.

Figures 10 to 12 show schematic views of convective heat flows occurring within the housing 200 of the apparatus 100 in different operational states of the apparatus 100. Figure 10 shows a situation in which an admissible temperature is present within the housing 200, which ranges between the minimum temperature and the maximum temperature for operating the heat sources 110. Thereby, the flaps 230 are in their respective first position 231, thus closing the closable air throughlets 210. Moreover, the baffles 220 are in their re- spective second position 226, thus not obstructing a convec- tive heat flow within the housing 200. As a result, a first convective hat flow 310 is generated which essentially flows through the entire housing 200 and results in a medium- strength heat exchange between the housing and the ambient surroundings of the housing 200.

If the temperature of the surroundings of the housing 200 is very low or if the heat sources 110 only produce a low thermal output so that an excessively strong cooling of the inte- rior of the housing 200 is imminent due to an excessive heat exchange between the interior of the housing 200 and the ambient surroundings of the housing 200, the temperature switches 240, 250 cause the baffles 220 to turn over into their respective first position 225, as shown schematically in Figure 11. The baffles 220 in their respective first position 225 limit the convective heat flow within the housing 200 so that a second convective heat flow 320 is generated which is reduced compared to the first convective heat flow 310 and which results in a smaller heat exchange between the interior of the housing 200 and the surroundings of the housing 200. Thereby it may be avoided that the temperature within the housing 200 drops below a predetermined minimum value . If the heat sources 110 arranged within the housing 200 produce a large thermal output so that an overheating is imminent within the housing 200, the temperature switches 240, 250, starting from the situation depicted in Figure 10, cause a turning-over of the flaps 230 from their respective first position 231 into their respective second position 232, thus opening the closable air throughlets 210 of the housing 200. As a result, a third convective heat flow 330 is generated within the housing 200, causing an air exchange between the interior of the housing 200 and the surroundings of th housing 200 via the air throughlets 210, which results in an increased heat exchange between the interior of the housing 200 and the surroundings of the housing 200. As a result, stronger cooling takes place within the housing 200, thus avoiding an overheating of the interior of the housing 200.

In a simplified embodiment, the housing 200 may only comprise air throughlets 210 and flaps 230, or only baffles 220 for adjusting the convective heat flow within the housing 200.

In summary, the housing 200 of the apparatus 100 provides a cooling option, the cooling output of which may be modified depending upon the temperature within the housing 200. The cooling output may thus be adjusted without active components, thus not requiring a separate power supply while being very robust and fail-safe.

Even though the invention has been described and illustrated in detail by the preferred embodiments, the invention is not limited to said embodiments. A person of skill in the art can deduct further variations without departing from the scope of the invention.

Claims

Apparatus (100)

comprising a housing (200) ,

the housing (200) comprising a closable air throughlet (210) ,

characterized in that

a first temperature switch (240, 250) is provided and coupled to the closable air throughlet (210) for opening and closing the air throughlet depending on a temperature .

Apparatus (100) according to claim 1,

the air throughlet (210) being closable by means of a flap (230) .

Apparatus (100) according to any one of the preceding claims ,

a baffle (220) being arranged in the housing (200) , whereby the baffle (220) may adopt a first position (225) and a second position (226) in order to influence a convection (300, 310, 320, 330) within the housing (200) ,

a second temperature switch (240, 250) being provided and coupled to the baffle (220) in order to move the baffle (220) into the first position (225) or the second position (226) depending on a temperature.

Apparatus (100) according to any one of the preceding claims,

the first temperature switch (240, 250) and/or the second temperature switch (240, 250) being arranged within the housing (200) . Apparatus (100) according to any one of the preceding claims ,

the first temperature switch (240, 250) and/or the sec- ond temperature switch (240, 250) being passive mechanical components.

6. Apparatus (100) according to claim 5,

the first temperature switch and/or the second temperature switch comprising a bimetal.

7. Apparatus (100) according to any one of claims 2 to 6, the flap (230) and/or the baffle (220) comprising a bi- metal (250) .

8. Apparatus (100) according to claim 5,

the first temperature switch and/or the second temperature switch comprising a container (240) filled with a fluid (241),

a volume of the container (240) changing according to a temperature .

9. Apparatus (100) according to claim 8, the fluid (241) being isobutane.

10. Apparatus (100) according to any one of the preceding claims ,

the first temperature switch (240, 250) and the flap (230) and/or the second temperature switch (240, 250) and the baffle (220) being coupled by means of a movable plunger (242, 252) .

11. Apparatus (100) according to any one of the preceding claims,

a heat source (110) being arranged in the housing (200) .

12. Apparatus (100) according to claim 11,

the heat source (110) being an electric device (110)

13. Apparatus (100) according to claim 12,

the electric device (110) being provided to be switched on and off periodically.

14. Apparatus (100) according to any one of claims 11 to 13,

the heat source (110) being provided to emit a time- variable thermal output.