US20050284166A1

US20050284166A1 - Apparatus to use vapor compression refrigeration in a mobile computing device

Info

Publication number: US20050284166A1
Application number: US10/876,040
Authority: US
Inventors: Rajiv Mongia; Himanshu Pokharna; Eric Distefano
Original assignee: Intel Corp
Current assignee: Intel Corp
Priority date: 2004-06-23
Filing date: 2004-06-23
Publication date: 2005-12-29

Abstract

An apparatus to use a compressor in a mobile computing device to increase a temperature of a working fluid used to absorb heat generated by a heat generating unit of the mobile computer. In one embodiment, the apparatus includes a working fluid loop with the fluid of the loop being in thermal contact with the heat generating device, and the fluid is to pass through a heat exchanger to dissipate heat from the fluid.

Description

FIELD OF INVENTION

The field of invention relates generally to heat management and more particularly to heat management using vapor compression refrigeration in a mobile computing device.

BACKGROUND

Heat management can be critical in many applications. Excessive heat can cause damage to or degrade the performance of mechanical, chemical, electric, and other types of devices. Heat management becomes more critical as technology advances and newer devices continue to become smaller and more complex, and as a result run at higher power levels and/or power densities.
Modern electronic circuits, because of their high density and small size, often generate a substantial amount of heat. Complex integrated circuits (ICs), especially microprocessors, generate so much heat that they are often unable to operate without some sort of cooling system. Further, even if an IC is able to operate, excess heat can degrade an IC's performance and can adversely affect its reliability over time. Inadequate cooling can cause problems in central processing units (CPUs) used in personal computers (PCs), which can result in system crashes, lockups, surprise reboots, and other errors. The risk of such problems can become especially acute in the tight confines found inside mobile computers and other portable computing and electronic devices.
Prior methods for dealing with such cooling problems have included using heat sinks, fans, and combinations of heat sinks and fans attached to ICs and other circuitry in order to cool them. However, in many applications, including portable and handheld computers, computers with powerful processors, and other devices that are small or have limited space, these methods may provide inadequate cooling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a diagram of a thermal management cycle, in accordance with one embodiment.
FIG. 2 presents a diagram of a thermal management cycle, in accordance with an alternative embodiment.
FIG. 3 presents an illustration of a vapor compression refrigeration in a mobile computing device, in accordance with an one embodiment.
FIG. 4 presents an illustration of a vapor compression refrigeration in a mobile computing device, in accordance with an alternative embodiment.
FIG. 5 presents an illustration of a vapor compression refrigeration in a mobile computing device, in accordance with an alternative embodiment.
FIG. 6 presents a flow diagram describing a process of using vapor compression refrigeration in a mobile computing device for thermal management, in accordance with one embodiment.

DETAILED DESCRIPTION

A method and apparatus to use a compressor in a mobile computing device to increase a pressure and temperature of a working fluid used to absorb heat generated by a heat generating unit of the mobile computer, is described. In one embodiment, the apparatus includes a working fluid loop with the fluid of the loop being in thermal contact with the heat generating device, and the fluid is to pass through a heat exchanger to dissipate heat from the fluid.
In the following description, numerous specific details are set forth. However, it is understood that embodiments may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description.
Reference throughout this specification to “one embodiment” or “an embodiment” indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In addition, as described herein, a trusted platform, components, units, or subunits thereof, are interchangeably referenced as a protected or secured.
In one embodiment, as described herein, a refrigerator using a vapor-compression cycle (otherwise known as an inverse Rankine cycle) is used to provide thermal management of a heat generating component within a mobile computer system. FIG. 1, illustrates a cycle diagram in accordance with one embodiment. At the lower pressure 1, the refrigerant passes across/through a cold plate (in contact with a heat generating component) and absorbs heat. The absorption of the heat will take the fluid to that state shown as #2. Although state # 2 is shown to be at the saturation point, it can also be within the vapor dome 101 or superheated.
After leaving the cold plate, the vapor is compressed to a higher pressure (to achieve a higher temperature) to state #3. This higher temperature and higher pressure fluid (which can either be vapor and/or liquid) is then passed through a heat exchanger which dissipates heat from the fluid. This lowers the temperature to state # 4. Note, state # 4 is at the same pressure as state # 3, but it is also possible that P4 would be less than P3. The fluid then passes through a throttling device to go back to state # 1 and restart the cycle.
Although the cycle shown in FIG. 1 takes place primarily within the vapor dome 101, it is also possible for the cycle to be contained outside of the vapor dome 101 as illustrated in FIG. 2. It is also possible for the cycle to operate entirely above the vapor dome 101 (i.e., super critical condition.)
FIG. 3 illustrates a working fluid loop 114 within a computing device 100 used in conjunction with vapor compression refrigeration to absorb heat of the component 108, in accordance with one embodiment. As illustrated, the fluid of the loop 114 is passed across the component 108, to absorb heat from the component. In one embodiment, working fluid loop 114 passes across or through a cold plate 109 thermally attached to the component 108 to absorb and transfer heat from the cold plate, which may include channels. The heat generating component 108 may include a processor, a chipset, a graphics controller, a memory controller, and other alternative heat generating components. The working fluid may be one of several different types of fluid refrigerant, such as freon, CO₂, etc.
Thereafter, the working fluid and/or vapor are passed through a compressor 102. The compressor increases the pressure of the working fluid and thereby also increases the temperature of the working fluid. The compressor may be any one of a compressor, including a reciprocating compressor, a linear compressor, a Scroll compressor, a WANKEL compressor, a diaphragm compressor, or another type.
The working fluid, which may be vapor after passing through the compressor, is then passed through heat exchanger 116 to dissipate heat. In one embodiment, the fluid vapor passes through a thermally conductive tube of the heat exchanger 116 that may include fins attached to the tube to dissipate the heat from the working fluid and/or the vapor. A heat exchanger fan 110 may be used to blow across the fins to dissipate the heat. The working fluid of the loop 114 returns across the heat generating component 108, as described above.
In one embodiment, after passing through the heat exchanger 116, the working fluid passes through a unit to decrease the pressure of the working fluid. As illustrated in FIG. 4, in one embodiment, the working fluid passes through a throttle device 118 to decrease the pressure of the working fluid prior to the working fluid passing across or through the cold plate 109 thermally attached to the component 108 to absorb and transfer heat from the cold plate. In an alternative embodiment, as illustrated in FIG. 5, a throttle bypass valve 120 may be included along the working fluid loop 114, to bypass the throttle device in the case of the compressor operating at a lower speed, and thereby not increasing the pressure of the working fluid as much as when operating at higher speeds.
The throttle bypass valve 120 can either be actuated by some external means or signal, or it can be an automatic valve that opens and closes in response to the amount of pressure and flow through the system. Furthermore, in alternative embodiments, multiple throttle bypass valves can be used in order to further optimize the system.
In one embodiment, an operating speed of the compressor 102 can be adjusted based on a predetermined event, such as a temperature of the heat generating component 108, an internal ambient temperature of the mobile computing device 100, a level of power provided to the component 108, whether the computing device 100 is receiving power from a battery source or power from an AC outlet, or other events. The flow diagram of FIG. 6, describes an example embodiment of the compressor 102 that has varying operating points based on a temperature of the component 108.
In process 602, the compressor 102 and the heat exchanger fan 110 are off, and in an embodiment including a throttle bypass valve, the bypass valve is actuated (i.e., opened.) In process 602, the computing device is to consume a relatively low amount of power, and cooling of the heat generating component 108, may be achieved by passive means.
In process 604, in response to the temperature of component 108 reaching a predetermined level a first time, the compressor is powered on to an operating speed to act as pump for the working fluid. The heat exchanger fan 110 remains off and the bypass valve (when present) remains actuated.
In process 606, in response to the temperature of component 108 reaching a predetermined level a second time, or reaching a separate predetermined level a first time, the heat exchanger fan is powered on, and the compressor remains powered at a level to act as a pump for the working fluid.
In process 608, in response to the temperature of component 108 reaching a predetermined level a third time, or reaching a separate predetermined level a first time, the operating speed of the compressor is increased to have the compressor increase the pressure of the working fluid (and thereby increase the temperature of the working fluid) as the fluid passes through the compressor. In one embodiment, the throttle bypass valve is also closed to force the working fluid through the throttle device to decrease the pressure of the working fluid.
In alternative embodiments, the units, and the sequence of the units being powered on may vary. Also the predetermined events that trigger the units to be powered on, may vary. For example, it should be appreciated that the compressor can run at lower speeds and yet still accomplish refrigeration (i.e., compression). This would create operating points between the high cooling conditions and the medium cooling conditions.
In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. For example, the above described thermal management technique could also be applied to desktop computer device. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. An apparatus comprising:

a compressor to be placed in a mobile computing device, the compressor to increase a pressure of a fluid used to absorb heat generated by a heat generating unit of the mobile computer.

2. The apparatus of claim 1, further including a working fluid loop with the fluid of the loop being in thermal contact with the heat generating device, the fluid to pass through a heat exchanger to dissipate heat from the fluid.

3. The apparatus of claim 2, wherein the fluid is to be at a first temperature after absorbing heat from the heat generating device, and the fluid is to be at a second temperature after passing through the compressor, the second temperature being higher than the first temperature.

4. The apparatus of claim 3, wherein the fluid is to drop to a third temperature after passing through the heat exchanger, the third temperature being lower than the second temperature.

5. The apparatus of claim 4, further including a throttle device, the fluid to pass through the throttle device after passing through the heat exchanger, the throttle to lower a pressure of the fluid.

6. The apparatus of claim 5, wherein the throttle device is to lower a pressure of the fluid to a fourth temperature, the fourth temperature being lower than the third temperature.

7. The apparatus of claim 6, further including a throttle bypass valve to have the working fluid bypass the throttle device when the compressor is operating at a first of two speeds, the first speed being slower than a second speed.

8. A mobile computing device comprising:

a processor;

a working fluid loop to include working fluid to be in thermal contact with the processor to absorb heat generated by the processor; and

a compressor, coupled to the working fluid loop, the compressor to operate a multiple speeds, including at least a first speed to pump working fluid, and a second speed to further increase a pressure and temperature of the working fluid.

9. The mobile computing device of claim 8, further including a heat exchanger having a fan, coupled to the working fluid loop, in response to a predetermined event.

10. The mobile computing device of claim 8, further including a throttle device, the fluid to pass through the throttle device after passing through the heat exchanger, the throttle to lower a pressure of the fluid; and

a throttle bypass valve to have the working fluid bypass the throttle device when the compressor is operating at the first speed.

11. An apparatus comprising.

a working fluid loop to be placed in a mobile computing device, to provide a working fluid of the loop in thermal contact with a heat generating device to absorb heat from the heat generating device;

a compressor, coupled to the working fluid loop, to increase a pressure of the fluid, and

a heat exchanger to dissipate heat from the fluid.

12. The apparatus of claim 11, wherein the compressor, in response to a first predetermined event, is to operate at a speed to pump the working fluid through the working fluid loop.

13. The apparatus of claim 12, wherein the heat exchanger includes a fan, and in response to a second predetermined event, following the first predetermined event, the fan is to be powered on.

14. The apparatus of claim 11 further including a throttle device, the fluid to pass through the throttle device after passing through the heat exchanger, the throttle to lower a pressure of the fluid; and

a throttle bypass valve to have the working fluid bypass the throttle device when the compressor is operating at a speed to pump the working fluid.

15. The apparatus of claim 14, wherein the compressor, in response to a third predetermined event, following the second predetermined event, is to operate at a speed to further increase pressure and temperature of the working fluid.

16. The apparatus of claim 15, wherein the throttle bypass valve, in response to a third predetermined event, is to close to force the working fluid through the throttle device.

17. A mobile computer device comprising:

a processor;

a heat exchanger to dissipate heat from the fluid; and

a wireless antenna.

18. The mobile computing device of claim 17, wherein the compressor, in response to a first predetermined event, is to operate at a speed to pump the working fluid through the working fluid loop.

19. The mobile computing device of claim 18, wherein the heat exchanger includes a fan, and in response to a second predetermined event, following the first predetermined event, the fan is to be powered on.

20. The mobile computing device of claim 19 further including a throttle device, the fluid to pass through the throttle device after passing through the heat exchanger, the throttle to lower the fluid; and

21. The mobile computing device of claim 20, wherein the compressor, in response to a third predetermined event, following the second predetermined event, is to operate at a speed to increase a pressure and temperature of the working fluid.

22. The mobile computing device of claim 21, wherein the throttle bypass valve, in response to a third predetermined event, is to have the working fluid bypass the throttle device.