AIR MOVER FOR IMPROVED COOLING OF ELECTRONICS

RELATED APPLICATIONS SECTION

This application is related to United States application number of 60/591,254, filed on July 26, 2004, and claims benefit of priority to United States Application 60/669, 115 filed on April 7, 2005, the teachings of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

As electronic devices get smaller and, it becomes desirable to reduce the size of heat sinks and heat exchangers used to cool these devices. Although liquids and phase change materials may be used to transfer heat away from the sources of heat in these devices, ultimately the heat must be rejected to a larger sink, such as the atmosphere, and must therefore be transferred to the air. Consequently, it is necessary to reduce the size of heat exchangers. The problem is that, as one reduces the size of the heat exchanger, one either reduces the heat exchanger surface area, or increases the specific surface area of the heat exchanger. This, in turn, either reduces the amount of heat that can be rejected, or increases the pressure required in the air flowing past the heat exchanger. This latter approach is one that has been largely avoided due to the desire to use fans and blowers. In order to use fans and blowers the pressure drop through the heat sink must be very small, and maintaining this low pressure drop has been the dominant constraint on heat exchanger design, limiting the practical level of heat exchanger density that can be achieved. Because fans and blowers are only able to produce very small amounts of pressure, heat exchangers have been designed for a high flow-low pressure drop air regime.

In addition to the size constraint imposed on electronics cooling equipment by the continuous reduction in the size of electronic products, many of these products that require cooling have also seen their heat loads increase over time. Since the effectiveness of the heat exchanger is measured by the increase in the temperature of the air exiting the heat exchanger, heat exchangers of a given effectiveness will require larger and larger airflows to remove this additional heat.

Another approach is to increase the effectiveness of the heat exchanger, raising the relative exit temperature of the air from the heat exchanger. In this manner, it is possible to increase the amount of heat removed with the same or even less air than is required by a heat exchanger of lower effectiveness. One method of increasing the effectiveness of the heat exchanger is to increase the density of the heat exchange media, but this approach has not been explored in the electronics cooling art due to a lack of suitable air moving technology that can produce the appropriate flows of air at higher pressures than blowers and fans or higher flows than compressors. Small compressors are available that produce output pressures in the range of 105,000 to 500,000 Pascals, but these have a very low flow to weight ratio (liter s/m/kg). Fans and blowers on the other hand may have very high flow to weight ratios, but can only generate a few thousand Pascals over atmospheric pressure.

The constraint placed on air moving technology for electronics cooling are severe. Until recently the power budget available for the air mover was very small, it was expected to be cheap, and last for several years with continuous duty, dust, moisture, and varying temperature conditions. In addition, business arrangements favored by computer manufacturers have tended to favor generic designs that were largely interchangeable, and designs for air movers that could be used with multiple models of heat sinks. This combined with the fact that cooling technology was seen as an ancillary rather than a strategic, or enabling technology, has also kept research and development investment, and innovation, low.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to provide a low pressure, high air flow compressor or air blower for use in electronics and similar applications. In a preferred embodiment, the compressor is a toroidal intersecting vane machine, or compressor (TIVC; toroidal intersecting vane compressor).

DETAILED DESCRIPTION OF THE INVENTION

The compressor of the invention is a low-pressure compressor. As used herein low pressure is defined as less than 500,000 Pascals. Preferably low pressure is less than 110,000 Pascals. Air pressures provided for the purposes of cooling electronic components are typically very low, in the range from about 0.005 to about

0.01 atm. In one embodiment, the low-pressure compressor can provide pressurized air at pressure of greater than 100 mm of water (100 mm water equals 0.01 atm). In addition to raising the output pressure from the air mover, it is also important that the specific flow (1/s/kg) also remain as high as possible. Current expected air requirements for different computer applications include an air flow between about 3-6 L/min at about 0.01-0.015 atm for a mobile personal computer; between about 5-10 L/min at about 0.015-0.03 atm for a desktop personal computer; and between about 10-20 L/min at about 0.025-0.05 atm for a performance computer. The compressor of the invention is preferably a high specific flow compressor. The air flow achieved by the compressor can be up to or exceed 20 liters per minute and can be up to about 300 liters per minute, or more. It is also highly desirable to be able to vary the flow of pressurized air, as the cooling required may vary.

Preferred compressors of the invention are toroidal intersecting vane machines (TIVM) or toroidal intersecting vane compressor (TIVC). Such machines incorporating intermeshing rotors have been described. See Chomyszak United States Patent 5,233,954, issued August 10, 1993, U.S. Application No: 10/744,230, filed on December 22, 2003, and Tomcyzk, United States Patent Application Publication 2003/0111040, published June 19, 2003. The contents of the patents and applications are incorporated herein by reference in their entirety.

The compressor is configured to provide air to a heat exchanger for the purpose of cooling electronic components. In an alternative embodiment, the compressor is configured as a vacuum pump to remove air from a heat exchanger for the purposes of cooling electronic components. A system employing the compressor of the invention can therefore comprise one or more TIVCs configured to provide air, to remove air or both from a heat exchanger.

Electronic systems incorporating the invention include a variety of computer systems (such as servers, personal computers, notebooks, and the like) other than the embodiment illustrated herein, and moreover to electronic, microelectronic and electrical devices other than computer systems, including, but not limited to, power supply, plasma TV, automotive electronics, airborne electronics, office business machines, switches, routers, and other electronic devices used in networking and

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communications, power tools, handheld personal display devices, PDAs, wearable computers, portable electronics including those having military applications, global positioning devices including those useful for tracking and triagulation of persons or vehicles, video games, cellphones, medical devices or equipment, laboratory equipment, fuel cells , lasers used in computers, lasers for telecommunications applications and the like. The devices and systems may be battery operated or electric, or have alternate power sources. It is also contemplated that the compressors of the present invention may be used alone or in combination with other available cooling technology. As such the system of the present invention may be used as a primary or auxilliary cooling system. The electronic components that can be cooled according to the invention include heat generating components, including but not limited to, processors, microprocessors, memory, microcontrollers, high speed video cards, disk drives, semi-conductor devices and the like. In one embodiment, the housing itself is the component to be cooled. The compressor of the invention is sized optimally for the desired application. In one embodiment, the compressor is sized to permit insertion into the electronic system housing. Insertion of the compressors into the housing may be horizontal or perpendicular to the housed components and multiple compressors may be configured to operation in series or in parallel to one another. Alternatively, the compressor may be operably connected to the electronic system or component to be cooled and not be contained within the same housing as the system or component to be cooled.

In one embodiment, the compressors of the present invention are optionally removably attached, bolted or clipped to the system, device or component to be cooled to allow for ease of replacement or maintenance. In addition, the compressors of the present invention may be configured as replacements and are sized to fit or be accommodated by a conventional bay or port for a cooling device, such as a fan. As such, the compressors are housed such to allow interchangeability with conventional fan and cooling systems. Thus, the compressor can be miniaturized to a range of sizes from about a liter for larger electronic systems such as. a rack of servers to less than about 8 cm ³ , in the case of a notebook. Other applications of the compressor of the invention contemplate sizes smaller than 8 cm ³ , such as those applications for

handheld and medical devices. In the case of a notebook, the compressor should be constructed from light weight materials. It is understood, however, that upon reduction in size, the weight of the compressor will become negligible as compared to the system or device housing it and therefore even mini- and micro- applications will no longer require the utilization of light weight materials. Lightweight materials include but are not limited to injection molded plastics, stamped sheet metal, etc.

The compressor preferably is equipped with a screen or filter over the inlet to provide filtration of the air. The screen should have a mesh size suitable for eliminating or decreasing dust from the plenum of the system. Filter and screen materials can be selected for the desired application and can include those that prevent or minimize harmful ingress of natural dust, dirt, or other solid airborne contaminants. For certain applications, the screen, or particulary the filter, will capture airborne pathogens such as mold, spores and bacteria. The filter or screen may capture over 90% of the particulates while minimizing the drop in air pressure .The compressor preferably is configured to permit reverse flow to clean or purge the screen. The flow reversal can preferably be automated (e.g., upon booting the system or at regular intervals) or selectively triggered by the user.

The compressor is configured to provide a gas, such as air, to an electronic system or its components for cooling purposes. Thus, the compressor can provide air by blowing air (e.g., a blower) into the system or by drawing air (e.g., a vacuum pump) from the system. The gas can be any gas or coolant. However, one advantage, and therefore one embodiment, of the present compressors avoids the need to employ special coolants and can use air, e.g., ambient air. While in some instances, the gas is the only coolant or material used for cooling. However, it can often be desirable or advantageous to employ a heat exchanger, regenerator and/or heat sink to further dissipate and control manage the heat in the system. Indeed, the present invention is advantageously employed in such systems as described in US Provisional Application Serial No. 60/560,382, filed on April 7, 2004, which describes a novel thermal management system for computers and is incorporated herein by reference.

In one embodiment, the compressor is operated in conjunction with an expander and heat exchanger. In this embodiment, the expander may comprise a

TIVM expander also known as a toroidal intersecting vane expander (TIVE). Use of TIVMs as expanders is described in U.S. Application No: 10/744,230, filed on December 22, 2003, herein incorporated by reference. In this embodiment, the heat of compression is rejected, and expansion allows an air of the temperature lower than ambient to be directed at the components to be cooled.

In one embodiment a TIVC and a TIVE can be connected with a second heat exhanger in between them. In this embodiment the air is compressed by the TIVC, raising its pressure and temperature, the air is then cooled by exchanging its heat with the atmosphere or with another cooling method, and then the cooled, pressurized air is partially or completely expanded through the TIVE. As the air expands its temperature drops and this cooled air is directed toward the components that require cooling.

In one embodiment, if it is desired to keep the components to be cooled at a temperature below ambient (the temperature of the air entering the TIVC), then the pressure ratio of the compressor and expander and/or air flow can be increased to further reduce the temperature of the air leaving the expander. Although it is not necessary to use an expander, for example, an expansion or pressure reducing valve may be used instead, the use of an expander connected to the compressor allows the power generated during the expansion offset some of the power required by the compressor, improving the energy efficiency of the system.

In yet another embodiment, the heat exchanger itself is the expansion device, operating either where the compressor and a means of heat rejection providing pressurized air to the expansion device/heat exchanger, or where the compressor is operating as a pump, and the pressure drop is occurring upstream of the pump in the heat exchanger expansion device.

The compressor can be configured to include one or more of the other thermal management components. For example, the TIVM can include a compressor and an expander, as described in U.S. Application No: 10/744,230, filed on December 22, 2003. Further, the TIVM can include a compressor and an integrated heat sink.

The system can further be operated with a spray of water or other coolant to reduce the work of compression by lowering incoming air temperature. A thermally

driven absorber utilizing heat from one or more sources within the system to be cooled can also be employed.

The above low pressure high flow compressors can be used in other applications as well. Indeed, it is well suited where size constraints are an issue. It should further be apparent to those skilled in the art that various changes in form and details of the invention as shown and described may be made. It is intended that such changes be included within the spirit and scope of the claims appended hereto.