WO2012069054A1

WO2012069054A1 - An energy transfer device

Info

Publication number: WO2012069054A1
Application number: PCT/DK2011/000140
Authority: WO
Inventors: Klaus Olesen; Jørgen HOLST; Bjørn VESTERGAARD; Asbjørn ROLFING
Original assignee: Danfoss Drives AS
Current assignee: Danfoss Power Electronics AS
Priority date: 2010-11-25
Filing date: 2011-11-25
Publication date: 2012-05-31
Anticipated expiration: 2013-05-25

Abstract

An assembly comprising a device for transferring energy which forms a cavity accommodating at least a part of one or more objects to be heated or cooled by means of the device for transferring energy, wherein the device for transferring energy defines one or more micro-channels. A method for fitting an object to be heated or cooled into a cavity of a device for transferring thermal energy: providing the objects to be heated or cooled and the device for transferring thermal energy, and inserting the objects to be heated or cooled into the cavity of the device for transferring thermal energy.

Description

AN ENERGY TRANSFER DEVICE FIELD OF THE INVENTION

The present invention relates to an assembly comprising a device for transferring energy which forms a jacket around an object to be heated and/or cooled (e.g. a battery). Moreover, the present invention relates to a method for inserting the object into a device for transferring energy.

BACKGROUND OF THE INVENTION

Devices, such as batteries, typically have a temperature range which is ideal for the operation of the device. In cold situations e.g. during start up of an electrical vehicle or any other device which is located in cold surroundings, the

temperature of a battery will typically be too low for the battery to operate ideally. On the other hand, many objects (such as batteries) generate heat during operation; this heat causes the batteries to be less efficient.

It is an object of one or more embodiments of the present invention to provide a means for maintaining an object (such as a battery or a power module for controlling an electrical motor) in an ideal temperature range during operation when the temperature exceeds a predetermined level.

DESCRIPTION OF THE INVENTION

In a first aspect, the present invention relates to an assembly comprising a device for transferring energy which forms a cavity accommodating at least a part of one or more objects to be heated and/or cooled by means of the device for transferring energy, wherein the device for transferring energy defines one or more micro-channels. The object to be heated and/or cooled may be a battery. By providing a device for transferring energy which is adapted to accommodate at least a part of a battery, this part of the battery may be cooled (or heated) to a desired operating temperature, whereby the efficiency of the battery may be maintained.

The cross-section of the object to be heated or cooled may define any shape such as a circle, en ellipse, a quadrangle, a square, a triangle or any other polygonal shape. Similarly the cross-sectional shape of the cavity may define circle, en ellipse, a quadrangle, a square, a triangle or any other polygonal shape.

The length of the objects to be heated and/or cooled may be identical to the length of the device for transferring energy. In one embodiment, the length of the cavity for accommodating a battery is identical to the length of the battery, i.e. the cavity of the device for transferring energy is 100 percent of the length of the battery.

In some embodiments, the device for transferring energy is adapted to accommodate only a part of a battery. As an example, the cavity of the device for transferring energy may correspond to 20 percent of the length of the battery, such as 40 percent of the length of the battery, such as 60 percent of the length of the battery, such as 80 percent of the length of the battery.

In one embodiment, the cavity of the device for transferring thermal energy defines a bottom surface which the objects to be heated or cooled abuts when inserted. In another embodiment, the device for transferring energy is tube shaped with two open ends, whereby the device may be positioned at any position along the length of the object.

The device for transferring thermal energy comprises one or more micro- channels, such as two, such as three, such as four, such as five, such as six, such as seven, such as eight, such as nine or such as ten or more. The micro- channels may extend parallel to the longitudinal direction of the object (e.g. a battery) to be heated and/or cooled (when the object is inserted into the device for transferring energy), and be equidistantly distributed relative to an inner surface defined by the cavity. As an example the micro-channels may be spaced apart such that for any two neighbouring micro-channels, the angular spacing angle between the two micro-channels is identical. The angular spacing angle being defined as, the angle between a first and a second line, the first line extending through a first of the two micro-channels and through the centreline of the battery and/or the cavity, and the second line extending through a second of the two micro-channels and through the centreline of the battery and/or the cavity. In one embodiment, the spacing angle between any two neighbouring micro-channels is 180 (~2/360) degrees, such as 120 (-3/360) degrees, such as 90 (-4/360) degrees, such as 72 (-5/360) degrees, such as 60 (-6/360) degrees, such as 51.4 (-7/360) degrees, such as 45 (-8/360) degrees, such as 40 (-9/360) degrees, such 36 (-10/360) degrees, such as 32.7 (-11/360) degrees, such as 30 (-12/360) degrees, such as 27.7 (-13/360) degrees, such as 25.7 (-14/360) degrees, such as 22.5 (-15/360) degrees.

In one embodiment, one or more of the micro-channels extend in a longitudinal direction of the device for transferring energy. Alternatively, or as a supplement, the micro-channels may extend in a direction which comprises a component which is transverse to the longitudinal direction of the device for transferring energy. As an example, the micro-channels may form spiral/helical lines around a battery, when the battery is inserted into the device for transferring energy. In one embodiment, an end portion of the device (which end portion defines the bottom of the cavity) may form micro-channels which extend in a direction which comprises a component which is transverse to a longitudinal direction of the battery. The micro-channels may form spiral lines in the end portion of the device. Alternatively, the micro-channels in the end of the device may be linear and extend in a direction which is parallel to a line extending through a center line of the battery when the battery is inserted into the device for transferring energy. In one embodiment, these spaced apart micro-channels are linear and parallel to the longitudinal direction of the battery and/or the cavity. In another embodiment, these spaced apart micro-channels form a helical shape.

In another embodiment, at least one of the micro-channels defines a first and a second end at which the channel is sealed, whereby said micro-channel defines an enclosed compartment inside the device for transferring energy. In the latter embodiment, a heat pipe may be defined by each of the micro- channels which is sealed in its ends. In the context of the present invention, the term 'heat pipe' shall be understood as a heat transfer mechanism that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces. The heat pipe of the present invention defines an enclosed compartment (in the micro- channels) in which a refrigerant is provided, whereby it is utilized that a relatively large amount of energy is needed to change the refrigerant from a liquid phase into vapor and that a relatively large amount of energy is released when the vapor is condensed on the inner surfaces of the micro-channel.

Accordingly, heat may be transported away from the hot battery by the liquid refrigerant vaporizing in the micro-channels in the proximity of to the battery and condensing in the micro-channel distally relatively to the battery. An example of such refrigerant is R-134a. In yet another embodiment, at least one of the micro-channels defines a first and a second end which are adapted to be fluidly connected to a system for circulating a cooling medium. When the micro-channels are connected to the system for circulating a cooling medium, a cooling medium may be provided inside the micro-channels, such that this cooling medium is circulated through the micro-channels. The micro-channels may be fluidly connected to a means for removing the thermal energy from the cooling medium. In one embodiment, this is a radiator which when the cooling medium flows therethrough causes thermal energy to be radiated to the surroundings or to surrounding air or into a passenger cabin of a vehicle. In one embodiment, the cooling medium is circulated through a means for elevating the temperature of an electrical component e.g. such that a predetermined desired operational temperature is achieved.

The cooling medium may be either of a single-phase medium or a two-phase medium. An example of a single-phase medium is water to which an anti freezing agent may be added. An example of a two-phase medium is R-134a. Thus in one embodiment, the micro-channels are fluidly connected to an air conditioning system and a two-phase medium is circulated in the micro- channels. The air conditioning system may define a closed circuit which accommodates the cooling medium and which comprises a compressor, a condenser, an evaporator and a pump. It will be appreciated that the micro- channels may define at least a part of the evaporator.

The device for transferring energy may be formed by extrusion. Alternatively, the device for transferring energy may be cast in a metal such as aluminum or iron. The micro-channels may be formed during the extrusion process by designing the extrusion tool correspondingly. In one embodiment, the micro- channels are formed by drilling the micro-channels in a separate step of the manufacturing process. In cases where the micro-channels form heat pipes, the heat pipe may be formed by drilling or extruding the holes and subsequently, closing the micro-channels once the cooling medium is provided inside the micro-channels. In one embodiment, the one or more objects comprise a battery and/or an electrical device such as a power module for controlling an electrical motor.

In yet another embodiment, the longest distance between any two points on an inner surface of the micro-channel in a plane extending transverse to the longitudinal direction of a battery assembly is below 100 mm, such as below 50 mm, such as below 25 mm, such as below 10 mm, such as below 8 mm, such as below 4 mm, such as below 2 mm, such as below 1 mm.

In a second aspect the present invention relates to a method for fitting an object to be heated or cooled into a cavity of a device for transferring thermal energy (e.g. a device for transferring thermal energy as set out above), the method comprising the steps of:

- providing the objects to be heated or cooled and the device for transferring thermal energy, and

- inserting the objects to be heated or cooled into the cavity of the device for transferring thermal energy. The device to be heated or cooled may be inserted into the cavity of the device for transferring energy by means of the method according to the second aspect. Accordingly, the invention according to the first aspect may comprise any combination of features and/or elements of the invention according to the second aspect.

In one embodiment, the method comprises, prior to the step of inserting, the step of:

- heating the device for transferring thermal energy and/or the objects to be heated or cooled to a predetermined higher temperature, and, subsequent to the step of inserting, the step of

- cooling the device for transferring thermal energy and the objects to be

heated or cooled to a predetermined lower temperature.

It will be appreciated that the higher temperature will preferably be higher than the lower temperature. In one embodiment, the temperature is elevated to a temperature above 100 degrees Celsius, such as a temperature above 200 degrees Celsius, such as a temperature above 300 degrees Celsius, such as a temperature above 400 degrees Celsius, or such as a temperature above 500 degrees Celsius.

- heating the device for transferring thermal energy and at the same time

cooling the objects to be heated or cooled, and, subsequent to the step of inserting, the step of

- cooling the device for transferring thermal energy to a predetermined lower temperature and heating the objects to be heated or cooled to a

predetermined higher temperature. In one embodiment, the predetermined lower temperature and the

predetermined higher temperature are substantially identical.

It will be appreciated that by heating the device for transferring energy, the inner dimensions of the cavity are increased. As an example the inner diameter of a cavity with a circular cross-section is increased. Moreover, it will be appreciated that by cooling the objects to be heated or cooled, the outer dimensions of these objects decrease. Thus it is easier to insert to objects into the cavity. Moreover, when the temperatures are again normalized i.e. when the objects to be heated or cooled have the same temperature as the device for transferring thermal energy, the fit between the objects and the device is even tighter. E.g. an interference fit may be achieved this way.

In one embodiment, the device for transferring energy, prior to the battery being inserted into the cavity, is heated to a temperature above 100 degrees Celsius, such as a temperature above 150 degrees Celsius, such as a temperature above 200 degrees Celsius, such as a temperature above 300 degrees Celsius, such as a temperature above 400 degrees Celsius.

In one embodiment, the objects to be heated or cooled is, prior to being inserted into the cavity of the device for transferring energy, cooled to a temperature below 0 degrees Celsius, such as a temperature below minus 25 degrees Celsius, such as a temperature below minus 50 degrees Celsius, such as a temperature below minus 75 degrees Celsius, such as a temperature below minus 100 degrees Celsius.

In one embodiment, the method also comprises the step of:

- applying a thermal paste to an outer surface of the objects to be heated or cooled and/or an inner surface of the cavity.

In yet another embodiment, the step of inserting comprises the step of:

- applying a predetermined force to the objects to be heated or cooled during insertion thereof into the cavity. In one other embodiment, the force is above 20 Newton, such as above 50 Newton, such as above 100 Newton, such as above 200 Newton, such as above 300 Newton, such as above 500 Newton.

The force may be applied in a direction which is parallel to a longitudinal direction of the battery and/or the cavity.

It will be appreciated the invention according to the second aspect may comprise any combination of features and/or elements of the invention according to the second aspect.

BRIEF DESCRIPTION OF THE INVENTION Exemplary embodiments of the invention will now be described in further detail, by way of example only, with reference to the figures in which:

Fig. 1 discloses a cross-sectional view of a first embodiment of the invention,

Fig. 2 discloses a cross-sectional view and a side view of a second embodiment of the invention, Fig. 3 discloses a device for transferring energy according to a third

embodiment of the invention, and

Fig. 4 discloses an assembly according to the third embodiment of the invention DETAILED DESCRIPTION OF THE INVENTION

Figs 1 and 2 discloses an assembly 100 comprising a device for transferring energy 102 which defines a cylindrical cavity 104, which is adapted to

accommodate a cylindrical battery 106. In one embodiment, the cylindrical battery 106 and cylindrical cavity 104 are shaped such that an outer surface 108 of the cylindrical battery 106 abuts an inner surface 110 of the cavity 104. The devices for transferring thermal energy 102 define one or more micro- channels 112 in which a cooling medium is provided. In one embodiment, the micro-channels 112 forms part of an air conditioning system which may be used to cool the battery 106. In another embodiment, the micro-channels 112 are sealed in two ends and contain a cooling medium whereby a heat pipe is defined.

In the embodiment of Fig. 1 , the device for transferring thermal energy 102 defines a plurality of fins 114 which are used for cooling the battery by convection. It will be appreciated that the devices for transferring thermal energy 104 may advantageously be extruded.

In the embodiment of Fig. 2, the cylindrical device for transferring thermal energy 102 comprises an inlet manifold 116 and an outlet manifold 118.

In the embodiment of Figs. 3 and 4 the devices for transferring thermal energy 102 defines a helical spring-like structure. One advantage of such a structure is that the inner diameter of the devices for transferring thermal energy 102 may be widened by rotating the ends 120 relative to each other (clockwise in the embodiment of Figs. 3 and 4). This makes it easier to insert the cylindrical battery 106. Once the cylindrical battery 106 is inserted, the ends 120 may be rotated in the opposite direction relative to each other (i.e. in the counter clockwise direction of in the figures) whereby a tight fit between the inner surfaces 110 of the devices for transferring thermal energy 102 and the outer surfaces 108 of the cylindrical battery 106 may be ensured.

In the embodiment of the Figs. 3 and 4, the spring-like structure defines a plurality of spaces 22 between the windings of the helical spring. However it will be appreciated that in other embodiments, the helical spring may be designed such that the sides of the windings abut each other whereby no or substantially no spaces 122 are defined.

It will be appreciated that the cooling medium in the channels may be any kind of coolant. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor promoting corrosion of the system. The cooling medium may be a single phase coolant which does not change phase during use or a two phase coolant which changes phase during use. An example of such refrigerant would be R-134a. In order to utilise the electrical current of the battery 106, the battery 106 comprises a positive power line 124 and a negative power line 126.

The embodiments of the invention described above are provided by way of example only. The skilled person will be aware of many modifications, changes and substitutions that could be made without departing from the scope of the present invention. For example, the principles of the invention could be used for heating objects (in addition to, or instead of, cooling objects as described above). Furthermore, the principles of the invention could be used for heating and/or cooling objects other than batteries; for example, a power module for controlling an electrical motor could be heated and/or cooled in accordance with the principles of the present invention. The claims of the present invention are intended to cover all such modifications, changes and substitutions as fall within the spirit and scope of the invention.

Claims

1. An assembly comprising a device for transferring energy which forms an cavity accommodating at least a part of one or more objects to be heated and/or cooled by means of the device for transferring energy, wherein the device for transferring energy defines one or more micro-channels.

2. An assembly according to claim 1 , wherein one or more of the micro- channels extend in a longitudinal direction of the device for transferring energy.

3. An assembly according to claim 2, wherein at least one of the micro-channels defines a first and a second end at which the channel is sealed, whereby said micro-channel defines an enclosed compartment inside the device for transferring energy.

4. An assembly according to claim 2, wherein at least one of the micro-channels defines a first and a second end which are adapted to be fluidly connected to a system for circulating a cooling medium.

5. An assembly according to any of claims 2-4, wherein the longest distance between any two points on an inner surface of the micro-channel in a plane extending transverse to the longitudinal direction of the battery assembly is below 2 mm.

6. An assembly according to any of the preceding claims, wherein a cooling medium is provided inside the micro-channels.

7. An assembly according to claim 6, wherein the cooling medium is either of a single-phase medium or a two-phase medium.

8. An assembly according to any of the preceding claims, wherein the device for transferring energy is formed by extrusion.

9. An assembly according to any of the preceding claims, wherein the one or more objects comprises a battery and/or a power module for controlling an electrical motor.

10. A method for fitting an object to be heated or cooled into a cavity of a device for transferring thermal energy, the method comprising:

- providing the objects to be heated or cooled and the device for transferring thermal energy, and - inserting the objects to be heated or cooled into the cavity of the device for transferring thermal energy.

11. A method according to claim 10, comprising, prior to the step of inserting, the step of:

- heating the device for transferring thermal energy and the objects to be

heated or cooled to a predetermined higher temperature, and, subsequent to the step of inserting, the step of

- cooling the device for transferring thermal energy and the objects to be

heated or cooled to a predetermined lower temperature.

12. A method according to any of claims 0-1 , further comprising the step of: - applying a thermal paste to an outer surface of the objects to be heated or cooled and/or the an inner surface of the cavity

13. A method according to any of claims 10-12, wherein the step of inserting comprises the step of:

- applying a predetermined force to the objects to be heated or cooled during insertion thereof into the cavity.

14. A method according to any of claims 10-13, wherein the force is above 20 Newton.