Patent Application
20130327511
The present invention relates generally to removal of gas interference in a liquid manifold, and more specifically to liquid cooling, and more specifically, but not exclusively, to passive air removal from a heat transferor that employs liquid coolant.
For purposes of this application, the term liquid coolant heat exchanger encompasses mechanisms that use a liquid fluid (hereafter just “liquid” identifying the liquid subset of fluid phases) to promote heat transfer from one set of components of a system to another set of components in order to maintain a desired operating temperature.
The liquid includes water, water mixtures (e.g., glycol/water formulations), oils, dielectrics, and the like. The liquid is used in cooperation with an interface for heat exchange that provides a liquid-to-air interface or a liquid-to-liquid interface. These interfaces include heat exchangers known as radiators, coolers, cold plate heat sinks, cooling jackets, and the like that move liquid relative to the interface in order to transfer heat.
Cooling effectiveness depends upon several factors including a thermal impedance of the heat exchanger at the interface. The thermal impedance is adversely affected when movement of the liquid is impaired or when the liquid does not directly contact the interface. The greater the impairment in liquid flow or decrease in surface area contact, the more that the thermal impedance increases and heat transfer efficiency declines. A common source of impairment or surface area contact decrease is air entrapment at the interface. Air may be inadvertently introduced (though in other contexts air is purposefully introduced) into the liquid and movement of the entrapped air in the liquid flow causes the liquid stream and the air flow direction to diverge, particularly when entering into chambers, manifolds and the like. The buoyancy of the air causes it to rise and accumulate, and if the rising air accumulates at a critical interface, cooling effectiveness can be degraded.
Conventional liquid heat exchangers and liquid cooling systems are typically designed with pathways in the cooling circuit that allow air to migrate out of the cooling circuit via buoyancy, in many cases by placing an outlet at the top of the component through which coolant is flowing or avoiding internal high points, cavities and pockets that make it difficult for the fluid to carry air through the component without it being trapped. In other design situations, active air scrubbers are required to remove air from highpoints in the system or components being cooled.
In some design situations there are constraints from component packaging and coolant line routing that require component coolant inlets and outlets to be both on the bottom. Such a design can result in a situation where air either rises above the liquid and creates an air pocket, or the cooling system cannot be filled without leaving a large quantity of air trapped in the upper portion of the component once the cooling system pumps are engaged.
What is needed is a system and method for passively removing accumulated gas from a manifold or thermal transfer interface that employs a moving liquid.
Disclosed is an apparatus, system and method for passively removing accumulated gas from a manifold or thermal transfer interface that employs a moving liquid.
An apparatus, including a sealed housing defining a manifold having an inlet port for receiving an input fluid stream into the manifold and an outlet port for exiting an output fluid stream from the manifold; and a bleed structure having a proximal end, a distal end, and a hollow channel communicating a first opening at the proximal end to a second opening at the distal end, the distal end disposed within the manifold and the proximal end disposed in the outlet port outside of the manifold.
An apparatus, including a sealed housing defining a manifold having an inlet port receiving an input fluid stream into the manifold, an outlet port exiting an output fluid stream from the manifold, and a heat transfer interface surface cooled by interaction with a cooling fluid moving through the manifold from the inlet port to the outlet port, wherein an interfering fluid mixed with the input fluid stream separates in the manifold and accumulates within a volume of the manifold to interfere with the interaction to decrease an efficiency of the interaction; and a bleed structure having a proximal end, a distal end, and a hollow channel communicating a first opening at the proximal end to a second opening at the distal end, the distal end disposed within a region of the volume of the manifold having a first pressure and the proximal end disposed with a region outside the sealed housing having a second pressure lower than the first pressure producing a pressure differential; wherein the interfering fluid moves through the bleed structure from the manifold to the region outside the sealed housing responsive to the pressure differential.
A heat transfer device, including a sealed housing defining a manifold having an inlet port receiving an input fluid stream into the manifold, an outlet port exiting an output fluid stream from the manifold and a heat transfer interface surface disposed within the manifold, wherein the input fluid stream has a first temperature, wherein the output fluid stream has a second temperature different than the first temperature, wherein the input fluid stream includes a first fluid mixed with a second fluid, the second fluid having a different density than the first fluid, wherein the first fluid flows into the manifold from the inlet port, substantially fills the manifold and contacts the heat transfer interface, and flows out the outlet port with said first temperature changed toward said second temperature responsive to an interaction with the heat transfer surface, and wherein the second fluid separates from the first fluid when entering into the manifold and accumulates in a portion of the manifold to interfere with the interaction; and a bleed structure having a proximal end, a distal end, and a hollow channel communicating a first opening at the proximal end to a second opening at the distal end, the distal end disposed within the manifold at the portion of the manifold where the second fluid accumulates and the proximal end disposed in the outlet port outside of the manifold; wherein a differential pressure between the proximal end and the distal end transfers the second fluid from the portion to the outlet port through the bleed structure.
A method including a) receiving an input fluid stream at an inlet port of a sealed housing including a manifold, the input fluid stream including a first fluid mixed with the second fluid wherein the second fluid separates from the first fluid when entering into the manifold to accumulate at a first portion of the manifold, the accumulation of the second fluid at the first portion interfering with a process within the sealed housing; b) exiting an output fluid stream from an outlet port of the sealed housing, the output fluid stream including the first fluid; and c) moving passively the second fluid from the first portion of the manifold to outside the sealed housing through a channel of a bleed structure responsive to a pressure differential between a first end of the bleed structure disposed at the first portion and a second end of the bleed structure disposed a region having a lower pressure than the first portion.
The following summary of the invention is provided to facilitate an understanding of some of the technical features related to remediation of gas-induced heat transfer impairment, and is not intended to be a full description of the present invention. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole. The present invention is applicable to other devices having a liquid flow and some gas-induced process impairment, and it is applicable to other arrangements besides those having a gas disposed in a liquid with the density of the gas being less than the liquid so that gas bubbles rise. Some embodiments may be adapted to other situations in which fluids separate in a chamber and a flowing liquid selectively entrains one of the separated fluids due to a pressure differential.
Other features, benefits, and advantages of the present invention will be apparent upon a review of the present disclosure, including the specification, drawings, and claims.
The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention.
Embodiments of the present invention provide a system and method for passively removing accumulated gas from a manifold or thermal transfer interface that employs a moving liquid. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements.
Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.
Manifold 100 preferably includes one or more rigid walls forming the enclosed space and may be virtually any shape. Inlet 105 and outlet 110 (collectively “ports”) are cannulated structures including a channel, with circular, square, or other cross-sections for an outer wall and a perimeter of the channel. (Typically the ports and channels both have circular cross-sections and are integrated or joined to a wall of manifold 100.
Input stream 115 includes a mixture of a first fluid with a second fluid that separate when entering chamber 120. The separation is due to differences in densities, with one (e.g., the second fluid) more “buoyant” than the other (i.e., the first fluid). The first fluid is often the desired manifold fluid and the second fluid is inadvertently mixed into the manifold fluid from pumping, cooling, and the like. The second fluid accumulates in chamber 120 (e.g., at a portion 130) and interferes with the manifold fluid interaction. In this context, either of the fluids may one or more liquids, one or more gasses, or combinations thereof.
The accumulation of a fluid (e.g., a gas) at an undesired location in a chamber may occur in other contexts besides separation of an incoming fluid mixture into constituent parts. In some contexts, nucleate boiling may occur on an inner surface, such boiling producing bubbles that release and accumulate within chamber 120. Bubbles may also be created in a bio-reactor resulting from a chemical, biological, or other process, particularly when enhanced through addition of heat. In other contexts, a pump for circulation of the fluid may cause cavitation that introduces bubbles.
In some situations, micro bubbles may be created in a circulating fluid stream that are too small to have sufficient buoyancy to separate in conventional deaeration systems. One reason is that the micro bubbles are readily entrained in the moving fluid and do not accumulate as long as the fluid is moving. However, when circulation stops, the bubbles are able to rise and accumulate in local high spots, such as in a radiator or a motor cooling jacket.
The manifold arrangements and functions, fluid types, fluid separation modalities, and manifold fluid interactions (and interferences) can vary widely within the spirit of the present invention. As an aid to understanding the present invention, a specific embodiment is described and is not to be taken as limiting the scope of the present invention. The following explanation details a specific example for a liquid-cooled heat transfer device used in an electric vehicle (EV).
Manifold 100 as a heat transfer device may thus represent a heat exchanger (e.g., a radiator, a transmission/gear cooler, a cold plate heat sink, a cooling jacket, and the like). A heat transfer device includes a heat transfer interface surface (e.g., a back wall 135 of manifold 100) disposed within chamber 120 that is in thermal communication with an object (e.g., a material, component, device, structure, or the like) that is to be cooled. A liquid coolant (e.g., a water/glycol mixture) enters chamber 120 from inlet 105 and then contacts and moves relative to back wall 135 to transfer heat from the object to the coolant. The transfer of heat causes the coolant within chamber 120 to become heated. The heated coolant exits from chamber 120 via outlet 110 and is replaced with cooler fluid entering from inlet 105. The exiting coolant is cooled and recirculated back to inlet 105 to maintain the object within a desired temperature range. The heat exchanger has a cooling efficiency that depends upon several factors including an efficiency of the heat transfer interaction of the coolant at the heat transfer interface surface (back wall 135 in this case).
It is the case that input stream 115 does not include coolant only, but includes a coolant mixed with a second fluid. In this example, the coolant is mixed with air (the second fluid in this example). As this coolant/air mixture enters into chamber 120, the air separates from the coolant and accumulates at portion 130. The accumulated air in portion 130 displaces coolant and limits/interferes with the cooling interaction of the coolant over a portion of a surface area of back wall 135. This interference degrades the cooling efficiency and can cause a hot spot, an undesired temperature rise of the object or portion thereof, or other undesired condition.
For this arrangement of air mixed into coolant, the air is less dense and its buoyancy causes the air to rise which locates portion 130 at the top of chamber 120. Manifold 100 includes a lateral wall 140 of chamber 120 that defines an aperture 145. An opening of outlet 110 is connected to aperture 145 and is part of the route that fluid exiting from manifold 100 takes when flowing to, and through, outlet 110. In some cases, it may be possible to locate aperture 145 at the top of chamber 120 in portion 130 in order to limit accumulation of air within chamber 120. However, in cases where a location for outlet 110 is constrained and must be located further towards a bottom of chamber 120, the more risk there is that air will accumulate in portion 130 and degrade the desired cooling interaction, with portion 130 expanding in volume as more air accumulates
In the context of the present application, up (including terms such as top/upper) and down (including terms such as bottom/lower) are determined by gravitational potential. It is gravitational potential that cause density and buoyancy differences between the first fluid and mixed second fluid to be important considerations for fluid separation and accumulation within chamber 120.
Internal passive air bleed device 205 is a cannulated structure including a channel 210 provided within an outer wall 215, with circular, square, or other cross-sections for channel 210 and outer wall 215. (Typically the wall and channel both have a circular cross-section.) In
In
External passive air bleed device 305 is a cannulated structure including a channel 310 provided within an outer wall 315, with circular, square, or other cross-sections for channel 310 and outer wall 315. (Typically the wall and channel both have a circular cross-section.) In
In
Coolant enters into the main coolant inlet and enters into a cooling chamber of cooling jacket 720. The coolant cools the electric motor as it flows through the cooling chamber towards outlet 725. External passive air bleed device 705 removes accumulated air from cooling jacket 720 by entraining it into coolant exiting from outlet 725 as described herein.
While the above description has focused principally on use of local passive air bleed devices for cooling embodiments in the context of re-entraining separated fluids from coolant mixtures, there are a wide variety of potential applications and embodiments of the present invention, some of which have been suggested herein. In the context of a bio-reactor or other sealed manifold, some applications may desirably have a defined gas volume above a liquid volume. This may be for chemical or bio-reactions or the like. Use of a passive air bleed device responsive to a fluid stream into and out of the sealed manifold would allow for continuous introduction of a gas into the sealed manifold while maintaining a specific concentration of gas species in the defined gas volume. The gas volume is set by placement and operation of the passive air bleed device and fluid flow rates as discussed herein along with a height and shape of the sealed manifold.
The system and methods above has been described in general terms as an aid to understanding details of preferred embodiments of the present invention. In the description herein, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of embodiments of the present invention. In some embodiments, it is most convenient and reliable to dispose the distal end of a passive bleed device in an outlet coupled to the same chamber that includes the proximal end. Other embodiments need not be so configured, with the distal end disposed in any lower pressure region (as compared to a static pressure at the proximal end).
The alternative location for the distal end may be another outlet or other system passively producing a reliable low static pressure region, preferably a local region. This is not to be construed as, and is different from, a traditional bleed system where a bleed port is placed at a top of a radiator and routed to a reservoir, from which any air stays in the reservoir while circulating coolant passing through the bleed system is drawn back into the bottom of the main coolant stream from an outlet at a bottom of the reservoir. A benefit of the present embodiment is that the passive air bleed device is located in proximity or inside of the chamber which is being de-aerated, and does not require a bleed line to a reservoir. In some vehicles, the chamber (e.g., a motor jacket) is at an opposite end of the vehicle from the reservoir which, for a conventional system, would require a dedicated bleed line running from one end to the other.
For reliability and dependability, particularly in critical applications, embodiments for the passive bleed device will be rigidly mounted, rigid tubes disposed and operating as disclosed herein. In some applications, it may be advantageous to employ flexible and/or moveable passive air bleed devices. For example, a passive air bleed device having a flexible outer wall and a proximal end fitted with a float would allow the first opening to move towards shifting fluid accumulation portions within the improved manifolds (this is easier to implement for internally disposed passive air bleed devices). This is advantageous for applications in which an orientation of the improved manifold twists and rotates so that the ‘up’ direction varies significantly and/or constantly.
Some features and benefits of the present invention are realized in such modes and are not required in every case. One skilled in the relevant art will recognize, however, that an embodiment of the invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of embodiments of the present invention.
Reference throughout this specification to “one embodiment”, “an embodiment”, or “a specific embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention and not necessarily in all embodiments. Thus, respective appearances of the phrases “in one embodiment”, “in an embodiment”, or “in a specific embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present invention may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments of the present invention described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the present invention.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.
Additionally, any signal arrows in the drawings/Figures should be considered only as exemplary, and not limiting, unless otherwise specifically noted. Furthermore, the term “or” as used herein is generally intended to mean “and/or” unless otherwise indicated. Combinations of components or steps will also be considered as being noted, where terminology is foreseen as rendering the ability to separate or combine is unclear.
As used in the description herein and throughout the claims that follow, “a”, “an”, and “the” includes plural references unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes only, various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention.
Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of embodiments of the invention will be employed without a corresponding use of other features without departing from the scope and spirit of the invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include any and all embodiments and equivalents falling within the scope of the appended claims. Thus, the scope of the invention is to be determined solely by the appended claims.
