Background of the Invention Cooling systems are used for cooling purposes in different applications, such as e.g. for cooling components such as PCB:s (Printed Circuit Boards) or chips or memory units or radio transceiver units or power amplifiers in telecom equipment etc.

A component to be cooled such as a PCB or a power amplifier may be cooled using a heat sink by placing the component to be cooled against the heat sink base in order to be able to transfer heat from the component to the heat sink. The heat sink may be arranged with cooling fins in order to improve the cooling.

If more cooling power is needed, it is possible to arrange forced cooling of the heat sink, i.e. to arrange a fan that forces a flow of air across the surfaces of the heat sink cooling fins thereby replacing the air around the cooling fins which air has been heated by the heat from the cooling fins with cooler ambient air from the outside of the heat sink.

Normally, radio units, e.g. radio transceivers, are installed on top of a tower or at a similar high mounting position. As the efficiency of e.g. power amplifiers in radio units is not 100%, they emit heat, i.e. the radio unit comprises heat generating components whereby the radio unit needs to be cooled. As mentioned above, one possibility is to cool the radio unit by arranging air cooled heat sinks with or without fans for forced cooling in the radio units. As the load in telecom systems is increasing, radio units need to be replaced with radio unit that can handle more load.

Due to the often limited base area of a heat generating component in a radio unit and the desire to place more and more functionality on a defined base area of a component, more powerful components are developed. This increase in component capacity may e.g. be accomplished by building higher integration components. This increase in component capacity leads to that more power may be fed to components per component base area than before which in turn results in that the components emit more heat per base area than before when in maximum use e.g. during peak load in telecom systems, i.e. the maximum heat load of components is increasing as they may be fed with more power per square centimetre (W/cm ² ) base area. This is also the case for components for radio units. Thus, when replacing radio units with new radio units, the new radio unit usually has a larger heat load. If a radio unit is replaced by a radio unit having more heat load, the heat sink arranged in the new radio unit has to have more cooling power which may be achieved using a heat sink with more cooling fin area, e.g. longer cooling fins, or by arranging a liquid cooling of the radio unit.

US 2006/0023423 Al shows an expandable heat sink.

Summary of the Invention The object of the present invention is to provide an improved cooling system for cooling a heat generating unit and an improved method for cooling a heat generating unit.

The object is achieved by arranging a cooling system for cooling a heat generating unit, the cooling system comprising an exchangeable heat sink unit being arranged removably connected to the heat generating unit in an assembled state of the cooling system, where the cooling system further comprises a heat dissipation structure and a heat output connector arranged in the heat generating unit, where the heat dissipation structure is arranged to dissipate heat from at least one heat generating component in the heat generating unit to the heat output connector, where further the exchangeable heat sink unit comprises a heat sink and a heat sink heat dissipation structure and a heat input connector, where the heat input connector is arranged to connect to said heat output connector to dissipate heat from said heat output connector via the heat sink heat dissipation structure to the heat sink. The object is further achieved by a method for cooling a heat generating unit with a cooling system comprising an exchangeable heat sink unit being arranged removably connected to the heat generating unit in an assembled state of the cooling system, comprising the steps of, arranging a heat dissipation structure and a heat output connector in the heat generating unit, arranging the heat dissipation structure to dissipate heat from at least one heat generating component in the heat generating unit to the heat output connector, arranging a heat sink and a heat sink heat dissipation structure and a heat input connector in the exchangeable heat sink unit, connecting the heat input connector to said heat output connector to dissipate heat from said heat output connector via the heat sink heat dissipation structure to the heat sink.

By arranging a cooling system comprising a heat dissipation structure and a heat output connector arranged in the heat generating unit, where the heat dissipation structure is arranged to dissipate heat from at least one heat generating component in the heat generating unit to the heat output connector, where further the exchangeable heat sink unit comprises a heat sink and a heat sink heat dissipation structure and a heat input connector, where the heat input connector is arranged to connect to said heat output connector to dissipate heat from said heat output connector via the heat sink heat dissipation structure to the heat sink, the cooling system may be updated by replacing the exchangeable heat sink with a heat sink having more cooling power without replacing the radio unit. This is advantageous when using radio units which comprise components that may be updated to handle more load by updating the software only, i.e. without replacing the hardware, where by updating the software the heat load of the radio unit is increased which increase in heat load may be taken care of by replacing the heat sink unit with a more powerful heat sink unit, where such a replacement may be done simply and quickly on site, e.g. in a tower where the radio unit is arranged.

According to one embodiment of the invention, the heat generating unit is a radio unit.

According to one embodiment of the invention, the at least one heat generating component is a Printed Circuit Board (PCB), a component on a PCB or a Power Amplifier arranged in the heat generating radio unit.

According to one embodiment of the invention, the at least one heat generating component in the heat generating unit is arranged in thermal contact with the heat dissipation structure. According to one embodiment of the invention, the heat dissipation structure is a heat pipe arranged to transfer heat from the at least one heat generating component to the heat output connector.

According to one embodiment of the invention, the heat dissipation structure is made of a material with high heat conductivity arranged to transfer heat from the at least one heat generating component to the heat output connector. According to one embodiment of the invention, the heat output connector and the heat input connector are arranged to be connected against each other in an assembled state of the cooling system thereby allowing for heat transfer by conduction from the heat output connector to the heat input connector. According to one embodiment of the invention, the heat sink heat dissipation structure is a heat pipe arranged to transfer heat from the heat input connector to the heat sink.

According to one embodiment of the invention, the heat dissipation structure is a coolant loop for coolant arranged to transfer heat from the at least one heat generating component to the heat output connector.

According to one embodiment of the invention, the heat sink heat dissipation structure is made of a material with high heat conductivity arranged to transfer heat from the heat input connector to the heat sink.

According to one embodiment of the invention, the heat output connector and the heat input connector are arranged to be connected against each other in an assembled state of the cooling system thereby allowing for heat transfer between the heat generating unit and the heat sink unit by mass transfer of coolant between the heat generating unit and the heat sink unit.

According to one embodiment of the invention, the coolant output connector and the coolant input connector are arranged to be connected against each other in an assembled state of the cooling system thereby allowing for mass transfer of coolant between the heat sink unit and the heat generating unit from the coolant output connector to the coolant input connector.

Further advantages of the invention will be apparent from the following detailed description. Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the present invention in which:

- Fig. 1 shows a schematic view of a cooling system according to a first embodiment of the invention for cooling a heat generating unit in a disassembled state,

- Fig. 2 shows another schematic view of a cooling system according to the first embodiment of the invention for cooling a heat generating unit in a disassembled state without heat sink.

- Fig. 3 shows a schematic view of a cooling system according to a second embodiment of the invention for cooling a heat generating unit in a disassembled state, and

- Fig. 4 shows another schematic view of a cooling system according to the second embodiment of the invention for cooling a heat generating unit in a disassembled state without heat sink. Detailed Description of the Invention

Fig. 1 shows a schematic view of a cooling system 2 according to a first embodiment of the invention for cooling a heat generating unit 4, where the cooling system 2 is shown in a disassembled state for clarity of description, the cooling system 2 comprising an exchangeable heat sink unit 6 being in an assembled state of the cooling system 2 arranged removably connected to the heat generating unit 4 in an assembled state of the cooling system 2, where the cooling system 2 further comprises a heat dissipation structure (not shown in the figure, see instead figure 2) and a heat output connector 8 arranged in the heat generating unit 4, where the heat dissipation structure is arranged to dissipate heat from at least one heat generating component (not shown in the figure, see instead figure 2) in the heat generating unit 4 to the heat output connector 8, where further the exchangeable heat sink unit 6 comprises a heat sink 10 and a heat sink heat dissipation structure 12 and a heat input connector 14, where the heat input connector 14 is arranged to connect to said heat output connector 8 to dissipate heat from said heat output connector 8 via the heat sink heat dissipation structure 12 to the heat sink 10.

The heat generating unit 4 is e.g. a radio unit, wherein the at least one heat generating component is e.g. a Printed Circuit Board (PCB), a component on a PCB or a Power Amplifier arranged in the heat generating radio unit.

The at least one heat generating component in the heat generating unit 4 is arranged in thermal contact with the heat dissipation structure, where heat from the at least one heat generating component is transferred to the heat dissipation structure preferably by conduction, whereby the at least one heat generating component is cooled whereas the heat dissipation structure is heated.

The heat dissipation structure may be a heat pipe arranged to transfer heat from the at least one heat generating component to the heat output connector 8. A heat pipe is a closed structure arranged to transfer heat, i.e. thermal energy, from one end to the other using a two-phase flow, employing evaporative cooling by evaporation and condensation of a coolant. The fluid inside the heat pipe is evaporated at the heated end and reduces the temperature at the hot end of the pipe whereby the temperature is increased at the other end of the pipe as the coolant condenses and releases its latent heat and heats this end of the pipe, thus transferring heat between the pipe ends, i.e. from the at least one heat generating component to the heat output connector 8.

The heat dissipation structure may optionally be made of a material with high heat conductivity such as e.g. graphite, copper or gold arranged to transfer heat from the at least one heat generating component to the heat output connector 8. The heat output connector 8 and the heat input connector 14 are arranged to be connected against each other in an assembled state of the cooling system 2 thereby allowing for heat transfer by conduction from the heat output connector 8 to the heat input connector 14. The heat output connector 8 and the heat input connector 14 may be of a plug-socket type, where the plug and the socket may be arranged as two large preferably cylindrical surfaces contacting each other over a large area for optimal heat transfer between the surfaces.

The heat output connector 8 and the heat input connector 14 are preferably quick-connectors that are connected and disconnected with ease.

The heat output connector 8 may be one end of the heat dissipation structure.

The heat input connector 14 may be one end of the heat sink heat dissipation structure 12.

The heat sink heat dissipation structure 12 may be a heat pipe arranged to transfer heat from the heat input connector 14 to the heat sink 10. The heat sink heat dissipation structure 12 may optionally be made of a material with high heat conductivity such as e.g. graphite, copper or gold arranged to transfer heat from the heat input connector 14 to the heat sink 10.

The heat sink heat dissipation structure 12 may optionally be a loop with coolant that is circulated in the exchangeable heat sink unit 6. The heat from the heat sink 10 is transferred to the environment e.g. by that heat is transferred from the heat sink 10 to ambient air 16 surrounding the heat sink 10 whereby the ambient air 16 cools the heat sink 10. A forced air flow of ambient air 16 may be arranged to cool the heat sink 10. Fig. 2 shows another schematic view of a cooling system according to the first embodiment of the invention for cooling a heat generating unit 4 in a disassembled state without heat sink for clarity of description. The cooling system 2 comprises an exchangeable heat sink unit 6 being in an assembled state of the cooling system 2 arranged removably connected to the heat generating unit 4 in an assembled state of the cooling system 2, where the cooling system 2 further comprises a heat dissipation structure 18 and a heat output connector 8 arranged in the heat generating unit 4, where the heat dissipation structure 18 is arranged to dissipate heat from at least one heat generating component 20 in the heat generating unit 4 to the heat output connector 8, where further the exchangeable heat sink unit 6 comprises a heat sink (not shown, see figure 1) and a heat sink heat dissipation structure 12 and a heat input connector 14, where the heat input connector 14 is arranged to connect to said heat output connector 8 to dissipate heat from said heat output connector 8 via the heat sink heat dissipation structure 12 to the heat sink.

The heat generating unit 4 is e.g. a radio unit, wherein the at least one heat generating component 20 is e.g. a Printed Circuit Board (PCB), a component on a PCB or a Power Amplifier arranged in the heat generating radio unit. The at least one heat generating component 20 in the heat generating unit 4 is arranged in thermal contact with the heat dissipation structure 18, where heat from the at least one heat generating component 20 is transferred to the heat dissipation structure 18 preferably by conduction, whereby the at least one heat generating component 20 is cooled whereas the heat dissipation structure 18 is heated. The heat dissipation structure 18 may be a heat pipe arranged to transfer heat from the at least one heat generating component 20 to the heat output connector 8.

The heat dissipation structure 18 may optionally be made of a material with high heat conductivity such as e.g. graphite, copper or gold arranged to transfer heat from the at least one heat generating component 20 to the heat output connector 8. The heat output connector 8 and the heat input connector 14 are arranged to be connected against each other in an assembled state of the cooling system 2 thereby allowing for heat transfer by conduction from the heat output connector 8 to the heat input connector 14.

The heat output connector 8 may be one end of the heat dissipation structure 18.

The heat input connector 14 may be one end of the heat sink heat dissipation structure 12. The heat sink heat dissipation structure 12 may be a heat pipe arranged to transfer heat from the heat input connector 14 to the heat sink. The heat sink heat dissipation structure 12 may optionally be made of a material with high heat conductivity such as e.g. graphite, copper or gold arranged to transfer heat from the heat input connector 14 to the heat sink.

The heat sink heat dissipation structure 12 may optionally be a loop with coolant that is circulated in the exchangeable heat sink unit 6.

Fig. 3 shows a schematic view of a cooling system 2 according to a second embodiment of the invention for cooling a heat generating unit 4, where the cooling system 2 is shown in a disassembled state for clarity of description, the cooling system 2 comprising an exchangeable heat sink unit 6 being in an assembled state of the cooling system 2 arranged removably connected to the heat generating unit 4 in an assembled state of the cooling system 2, where the cooling system 2 further comprises a heat dissipation structure (not shown in the figure, see instead figure 4) and a heat output connector 8 arranged in the heat generating unit 4, where the heat dissipation structure is arranged to dissipate heat from at least one heat generating component (not shown in the figure, see instead figure 4) in the heat generating unit 4 to the heat output connector 8, where further the exchangeable heat sink unit 6 comprises a heat sink 10 and a heat sink heat dissipation structure 12 and a heat input connector 14, where the heat input connector 14 is arranged to connect to said heat output connector 8 to dissipate heat from said heat output connector 8 via the heat sink heat dissipation structure 12 to the heat sink 10.

The heat generating unit 4 is e.g. a radio unit, wherein the at least one heat generating component is e.g. a Printed Circuit Board (PCB), a component on a PCB or a Power Amplifier arranged in the heat generating radio unit. The at least one heat generating component in the heat generating unit 4 is arranged in thermal contact with the heat dissipation structure, where heat from the at least one heat generating component is transferred to the heat dissipation structure preferably by conduction, whereby the at least one heat generating component is cooled whereas the heat dissipation structure is heated. According to this embodiment, the heat dissipation structure is a coolant loop for coolant 22 arranged to transfer heat from the at least one heat generating component to the heat output connector 8.

The heat output connector 8 and the heat input connector 14 are arranged to be connected against each other in an assembled state of the cooling system 2 thereby allowing for heat transfer between the heat generating unit 4 and the heat sink unit 6 by mass transfer of coolant 22, i.e. fluid flow, between the heat generating unit 4 and the heat sink unit 6 from the heat output connector 8 to the heat input connector 14.

The heat output connector 8 and the heat input connector 14 may be of a plug-socket type. The heat output connector 8 and the heat input connector 14 are preferably quick-connectors that are connected and disconnected with ease.

The heat output connector 8 may be one end of the heat dissipation structure.

The heat input connector 14 may be one end of the heat sink heat dissipation structure 12.

According to this embodiment, the heat sink heat dissipation structure 12 is a coolant loop for coolant 22 arranged to transfer heat from the heat input connector 14 to the heat sink 10.

According to this embodiment, the heat sink heat dissipation structure 12 comprises a coolant output connector 24 and the heat dissipation structure comprises a coolant input connector 26.

The coolant output connector 24 is further connected to the heat sink heat dissipation structure 12 which is a coolant loop for coolant 22. The coolant input connector 26 is further connected to the heat dissipation structure which is a coolant loop for coolant 22.

Further, the coolant output connector 24 and the coolant input connector 26 are arranged to be connected against each other in an assembled state of the cooling system 2 thereby allowing for mass transfer of coolant 22 between the heat sink unit 6 and the heat generating unit 4 from the coolant output connector 24 to the coolant input connector 26. The heat dissipation structure and the heat sink heat dissipation structure 12 are thus arranged as mass transfer structures.

The heat from the heat sink 10 is transferred to the environment e.g. by that heat is transferred from the heat sink 10 to ambient air 16 surrounding the heat sink 10 whereby the ambient air 16 cools the heat sink 10. A forced air flow of ambient air 16 may be arranged to cool the heat sink 10.

Thus, the dissipation structure and the heat sink dissipation structure 12 form two sub-loops that are connected to form a coolant system loop 28 wherein coolant 22 is circulated between the heat generating unit 4 and the heat sink unit 6, the coolant transferring heat from the heat generating unit 4 to the heat sink unit 6 where heat is transferred to the environment thus cooling the at least one heat generating component.

The flow of coolant 22 may be enabled by arranging an active part 30 in the heat sink unit 6 arranged to circulate coolant 22 in the coolant system loop 28. The active part may be a pump or a compressor. The coolant may optionally be circulated in the system coolant loop 28 by gravity or capillary force. Thus, the coolant 22 may be circulated in the system coolant loop 28 by using a driving force or without using a driving force.

The coolant 22 may be a cooling medium such as e.g liquid or air or a 2-phase liquid-gas combination, or liquid metal.

The heat sink 10 may comprise fins, which fins may be arranged with channels for the circulating coolant 22.

Fig. 4 shows another schematic view of a cooling system 2 according to the second embodiment of the invention for cooling a heat generating unit 4 in a disassembled state without heat sink for clarity of description. The cooling system 2 comprises an exchangeable heat sink unit 6 being in an assembled state of the cooling system 2 arranged removably connected to the heat generating unit 4 in an assembled state of the cooling system 2, where the cooling system 2 further comprises a heat dissipation structure 18 and a heat output connector 8 arranged in the heat generating unit 4, where the heat dissipation structure 18 is arranged to dissipate heat from at least one heat generating component 20 in the heat generating unit 4 to the heat output connector 8, where further the exchangeable heat sink unit 6 comprises a heat sink and a heat sink heat dissipation structure 12 and a heat input connector 14, where the heat input connector 14 is arranged to connect to said heat output connector 8 to dissipate heat from said heat output connector 8 via the heat sink heat dissipation structure 12 to the heat sink.

The heat generating unit 4 is e.g. a radio unit, wherein the at least one heat generating component is e.g. a Printed Circuit Board (PCB), a component on a PCB or a Power Amplifier arranged in the heat generating radio unit.

The at least one heat generating component 20 in the heat generating unit 4 is arranged in thermal contact with the heat dissipation structure 18, where heat from the at least one heat generating component 20 is transferred to the heat dissipation structure 18 preferably by conduction, whereby the at least one heat generating component 20 is cooled whereas the heat dissipation structure 18 is heated.

According to this embodiment, the heat dissipation structure 18 is a coolant loop for coolant 22 arranged to transfer heat from the at least one heat generating component 20 to the heat output connector 8.

The heat output connector 8 and the heat input connector 14 are arranged to be connected against each other in an assembled state of the cooling system 2 thereby allowing for heat transfer between the heat generating unit 4 and the heat sink unit 6 by mass transfer of coolant 22 between the heat generating unit 4 and the heat sink unit 6 from the heat output connector 8 to the heat input connector 14.

The heat output connector 8 and the heat input connector 14 may be of a plug-socket type. The heat output connector 8 and the heat input connector 14 are preferably quick-connectors that are connected and disconnected with ease.

The heat output connector 8 may be one end of the heat dissipation structure 18.

The heat input connector 14 may be one end of the heat sink heat dissipation structure 12. According to this embodiment, the heat sink heat dissipation structure 12 is a coolant loop for coolant 22 arranged to transfer heat from the heat input connector 14 to the heat sink.

According to this embodiment, the heat sink heat dissipation structure 12 comprises a coolant output connector 24 and the heat dissipation structure 18 comprises a coolant input connector 26.

The coolant output connector 24 is further connected to the heat sink heat dissipation structure 12 which is a coolant loop for coolant 22.

The coolant input connector 26 is further connected to the heat dissipation structure 18 which is a coolant loop for coolant 22. Further, the coolant output connector 24 and the coolant input connector 26 are arranged to be connected against each other in an assembled state of the cooling system 2 thereby allowing for mass transfer of coolant 22 between the heat sink unit 6 and the heat generating unit 4 from the coolant output connector 24 to the coolant input connector 26. The heat dissipation structure 18 and the heat sink heat dissipation structure 12 are thus arranged as mass transfer structures.

The heat from the heat sink 10 is transferred to the environment e.g. by that heat is transferred from the heat sink 10 to ambient air 16 surrounding the heat sink whereby the ambient air 16 cools the heat sink. A forced air flow of ambient air 16 may be arranged to cool the heat sink 10. Thus, the dissipation structure 18 and the heat sink dissipation structure 12 form two sub- loops that are connected to form a coolant system loop 28 wherein coolant 22 is circulated between the heat generating unit 4 and the heat sink unit 6, the coolant transferring heat from the heat generating unit 4 to the heat sink unit 6 where heat is transferred to the environment thus cooling the at least one heat generating component 20. The flow of coolant 22 may be enabled by arranging an active part 30 in the heat sink unit 6 arranged to circulate coolant 22 in the coolant system loop 28. The active part may be a pump or a compressor. The coolant may optionally be circulated in the system coolant loop 28 by gravity or capillary force. Thus, the coolant 22 may be circulated in the system coolant loop 28 by using a driving force or without using a driving force.

The coolant 22 may be a cooling medium such as e.g liquid or air or a 2-phase liquid-gas combination, or liquid metal.

The heat sink may comprise fins, which fins may be arranged with channels for the circulating coolant 22.

The invention also relates to a method for cooling a heat generating unit 4 with a cooling system 2 comprising an exchangeable heat sink unit 6 being arranged removably connected to the heat generating unit 4 in an assembled state of the cooling system 2, comprising the steps of, arranging a heat dissipation structure 18 and a heat output connector 8 in the heat generating unit 4, arranging the heat dissipation structure 18 to dissipate heat from at least one heat generating component 20 in the heat generating unit 4 to the heat output connector 8, arranging a heat sink 10 and a heat sink heat dissipation structure 12 and a heat input connector 14 in the exchangeable heat sink unit 6, connecting the heat input connector 14 to said heat output connector 8 to dissipate heat from said heat output connector 8 via the heat sink heat dissipation structure 12 to the heat sink 10. The step of arranging a heat dissipation structure 18 in the heat generating unit 4 may comprise the step of arranging a heat pipe as a heat dissipation structure 18 in the heat generating unit 4.

The step of arranging a heat dissipation structure 18 in the heat generating unit 4 may comprise the step of arranging a material with high heat conductivity as a heat dissipation structure 18 in the heat generating unit 4.

The step of arranging a heat sink heat dissipation structure 12 in the exchangeable heat sink unit 6 may comprise the step of arranging a heat pipe as a heat sink heat dissipation structure 12 in the exchangeable heat sink unit 6.

The step of arranging a heat sink heat dissipation structure 12 in the exchangeable heat sink unit 6 may comprise the step of arranging a material with high heat conductivity as a heat sink heat dissipation structure 12 in the exchangeable heat sink unit 6.

The step of arranging a heat dissipation structure 18 in the heat generating unit 4 may comprise the step of arranging coolant loop for coolant 22 arranged to transfer heat from the at least one heat generating component 20 to the heat output connector 8 as a heat dissipation structure 18 in the heat generating unit 4, where further the step of arranging a heat sink heat dissipation structure 12 in the heat sink unit 6 may comprise the step of arranging a coolant loop for coolant 22 arranged to transfer heat from the heat input connector 14 to the heat sink 10 as a heat sink heat dissipation structure 12 in the heat sink unit 4, where further the step of dissipating heat from said heat output connector 8 via the heat sink heat dissipation structure 12 to the heat sink 10 may comprise the step of transferring heat between the heat generating unit 4 and the heat sink unit 6 by mass transfer of coolant 22 between the heat dissipation structure 18 and the heat sink heat dissipation structure 12, the method further may comprise the steps of arranging the heat sink heat dissipation structure 12 with a coolant output connector 24 and arranging the heat dissipation structure 18 with a coolant input connector 26, and connecting the coolant output connector 24 and the coolant input connector 26 against each other in an assembled state of the cooling system 2 thereby allowing for return mass transfer of coolant 22 from the heat sink unit 6 to the heat generating unit 4. The present invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claim. Thus, it is possible to combine features from the embodiments described above as long as the combinations are possible.