Cabinet cooling

• US 7,061,763 B2
• Filed: 01/29/2002
• Issued: 06/13/2006
• Est. Priority Date: 01/29/2002
• Status: Expired due to Fees

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Tsoi, Vadim
• Primary Examiner(s): DATSKOVSKIY, MICHAIL V
• Application Number:
  US10/502,385
• Publication Number:
  US 20050083654A1
• Time in Patent Office: 1,596 Days
• Field of Search: 361/687, 361/698, 361/699, 361/700, 361/701, 361/724, 622/592, 622/594, 165/104.33, 165/104.34, 257/714, 312/236, 312/223.2, 312/223.3
• US Class Current: 361/699
• CPC Class Codes: F25B 1/06 with compressor of jet type, e.g. using liquid under pressure F25B1/005, F25B1/10 take precedence
• CPC Class Codes: F25B 23/006 boiling cooling systems
• CPC Class Codes: F25B 2700/2106 of fresh outdoor air
• CPC Class Codes: F25B 2700/2116 of a condenser
• CPC Class Codes: F25B 2700/2117 of an evaporator
• CPC Class Codes: G05D 23/1931 to control the temperature of one space
• CPC Class Codes: H05K 7/20381 Thermal management, e.g. evaporation control

Abstract

A novel electronics cooling method and system is disclosed. A very flexible and efficient operation of an electronics cooling system (10) is achieved by controlling circulation of a cooling medium in a closed system (40) containing an evaporator (13), a condenser (14), an ejector (11) and control valves (15–18). Specifically, the system is continuously allowed to operate in the most appropriate mode by controlling the valves (15–18) of the system (10) based on detected heat load and/or detected heat transfer conditions. By automatically adapting the mode of operation of the system based on the actual prevailing conditions, a unique flexibility is obtained with regard to the cooling mode in which the system will be operated. This means that the cooling capacity will be constantly optimized and that the investment cost as well as the cost for operating the system will be reduced compared to known systems having equal maximum cooling capacity.

Claims

1. A method of cooling a cabinet containing heat dissipating electronic components (PBA), comprising the steps of:

circulating cooling medium in a closed fluid system to absorb heat in an evaporator in the cabinet and to transfer the absorbed heat from the cabinet and to emit said heat outside the cabinet in a condenser/heat exchanger,

detecting the evaporator temperature (T₁) inside the cabinet to determine the heat load on the system;

detecting the ambient temperature (T₃) and the temperature (T₂) in the condenser to determine the conditions of the heat transfer from the cooling medium;

controlling a forced circulation of the cooling medium based on the detected heat load and conditions of heat transfer;

controlling the flow of the cooling medium back to the evaporator in the cabinet based on the detected heat load and conditions of heat transfer; and

controlling the activation/deactivation of a vapor compression cycle based on the detected heat load and conditions of heat transfer;

thereby allowing a controlled shifting between cooling of the cabinet in different cooling modes optimized for different heat load and heat transfer conditions.

2. The method according to claim 1, wherein when the detected heat load inside the cabinet is lower than a predetermined first level and/or the detected ambient temperature (T₃) is lower than a predetermined level,

a fluid pump is deactivated for interrupting forced circulation of the cooling medium;

the full flow of cooling medium from the condenser is returned to the evaporator where cooling medium is vaporized; and

the full flow of vaporized cooling medium from the evaporator is conducted to a secondary side of an ejector through the ejector and from an outlet from the ejector back to the condenser;

whereby the cooling of the cabinet is performed in a thermosyphon cooling mode.

3. The method according to claim 2, wherein the level of the ambient temperature (T₃) is approximately 30°

C., in that cooling medium is vaporized at approximately 50°

C. in the evaporator, and in that the cooling medium vapor condenses at substantially the same temperature in the condenser and emits heat, whereby the temperature gradient between the surroundings and the condenser is in the range of 15–

30°

C.

4. The method according to claim 3, wherein the cooling medium vapor from the evaporator is drained freely through the ejector and is condensed in the condenser.

5. The method according to claim 4 when the detected heat load inside the cabinet is higher than a predetermined first level but lower than a pre-determined second level and the detected ambient temperature (T₃) is lower than a pre-determined level,

a fluid pump is activated for performing forced circulation of the cooling medium;

the full flow of cooling medium from the condenser is returned to the evaporator; and

cooling medium from the evaporator is pumped to a primary side of an ejector, through the ejector and to the condenser;

whereby the cooling of the cabinet is performed in a liquid cooling mode.

6. The method according to claim 5, the level of the ambient temperature (T₃) is approximately 30°

C. in that a portion of the cooling medium vaporizes at approximately 50°

C. in the evaporator and in that cooling medium vapor condenses at substantially the same temperature in the condenser and emits heat, whereby a temperature gradient between the surroundings and the condenser is in the range of 15–

30°

C.

7. The method according to claim 6, wherein entrance to a secondary side of the ejector is blocked and in that the full flow of cooling medium in a liquid and a vapor phase is pumped through the ejector primary side to the condenser.

8. The method according to claim 7 wherein when the detected heat load inside the cabinet exceeds a predetermined second level and/or the detected ambient temperature (T₃) is higher than a predetermined level,

a fluid pump is activated for performing forced circulation of the cooling medium;

a restricted flow of cooling medium is conducted from the condenser to the evaporator where the cooling medium is vaporized, the restricted flow being controlled based on the detected evaporator temperature (T₁) and/or on the detected ambient temperature (T₃);

the remainder of the flow of cooling medium from the condenser is circulated to a primary side of an ejector by the fluid pump, creating a negative pressure at a secondary side of the ejector; and

the vaporized cooling medium is pumped out from the evaporator to the secondary side of the ejector by the created negative pressure and is returned to the condenser;

whereby the cooling of the cabinet is performed in an ejector cooling mode.

9. The method according to claim 8, wherein the pressure delivered by the fluid pump is controlled based on the detected evaporator temperature (T₁) and/or on the detected ambient temperature (T₃).

10. The method according to claim 9, wherein the vaporized cooling medium is compressed and partly condensed in the ejector by the pumped primary cooling medium, and is then conducted to the condenser for further condensation.

11. The method according to claim 10 wherein a pressure difference (P₁−

P₂) and a temperature gradient (T₁−

T₂), respectively, between evaporator and condenser is regulated by controlling a restrictor valve to provide optimal cycle conditions in relation to the detected heat load and ambient temperature (T₃).

12. A cooling system for cooling a cabinet containing heat dissipating electronic components (PBA), comprising:

means for circulating a cooling medium in a closed fluid system from a condenser/heat exchanger to an evaporator inside the cabinet and back to the condenser/heat exchanger;

at least one valve for controlling the flow of cooling medium between the condenser and the evaporator;

an ejector having a primary and a secondary side;

a fluid line system connecting the condenser to the evaporator and to a fluid pump, respectively, through first and second controlled valves and connecting the evaporator to the fluid pump and the ejector secondary side, respectively, through third and fourth controlled valves;

temperature sensors for detecting the evaporator temperature (T₁), for detecting the condenser temperature (T₂) and for detecting the ambient temperature (T₃), respectively; and

a control unit for controlling the positions of the valves in dependence on the detected temperatures.

13. The cooling system according to claim 12, wherein the first valve is a one-way restrictor valve blocking backflow from the evaporator to the condenser and controlled by the control unit to regulate cooling medium flow from the condenser to the evaporator.

14. The cooling system according to claim 13, wherein the ejector is a low pressure ejector operating at low primary side positive pressure and having a primary side distribution chamber for receiving the primary cooling medium and a multi-channel nozzle in the form of a spherical segment provided with radial nozzle holes leading into a mixing chamber that is surrounded by a secondary cooling medium supply chamber communicating with the mixing chamber through a plurality of supply holes and that is connected to a diffuser through a neck.

15. The cooling system according to claim 14, wherein the cooling medium conducting inner cross-section area of the neck is substantially equal to the total cross-section area of the nozzle holes and in that the geometrical centre (C) of the spherical segment of the nozzle lies on a mixing chamber center axis (CA), immediately downstream of the neck.

16. The cooling system according to claim 14, wherein the evaporator consists of several evaporator heat sinks each directly contacting one or more of the electronic components (PBA).

17. The cooling system according to claim 16, wherein the evaporator consists of thin metal plates with built-in water channels directly transferring heat from the electronic components (PBA).

18. The cooling system according to claim 15 wherein the evaporator comprises a cold wall containing cooling medium and contacting one edge of several electronic components (PBA) and in that heat transfer from the electronic components to the cold wall cooling medium is performed through heat lines, heat pipes or aluminum plates.

19. The cooling system according to claim 15 wherein the evaporator has an evaporator chamber, and in that the ejector is integrated as a unit with the evaporator chamber.

20. The cooling system according to claim 19, wherein the diffuser of the ejector is physically connected to the condenser.

21. The cooling system according to claim 20, wherein ejector, condenser and evaporator chamber are one integrated unit.