Patent Application
20050284166
The field of invention relates generally to heat management and more particularly to heat management using vapor compression refrigeration in a mobile computing device.
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.
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.
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
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
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
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.
