Patent Application
20210080197
The present invention generally relates to heat exchangers, and more specifically to low-profile heat exchangers with improved heat transfer characteristics for transmitting heat from heat emitting objects requiring temperature control, such as power inverters, through a coolant or other fluid flowing therethrough the heat exchanger.
The performance of various electronic devices—such as transistors, circuit components, integrated circuits, and batteries—often directly correlates with temperature. In general, an increase in temperature causes an increase in impedance in conductors and semiconductors which, in turn, can lead to an even greater production of heat. This heat-impedance feedback loop is well known. To reduce or maintain a level of heat, devices that produce heat are commonly cooled by heat sinks, fans, or liquid cooling apparatuses. Some systems include temperature probes that monitor for overheating and, if detected, intentionally throttle down performance or shut down the device entirely to prevent permanent damage.
One type of electronic device whose operation is particularly sensitive to operating temperatures is the power inverter (e.g., a device that converts direct current (DC) to alternating current (AC)). In principle, power inverters operate by supplying a voltage to an inductor or transformer coil to drive a current through the inductor one way, reversing the voltage at that inductor or transformer coil to drive current through the inductor the opposite way, and repeating the oscillation approximately fifty to sixty times per second. The switching action is often accomplished using power transistors or solid-state relays. Modern power inverters include complex circuitry to generate approximations of sine waves, to substantially mimic the AC power supplied from the region's power grid.
The performance and product lifetime of power inverters can be affected by the operating temperatures of the power inverter—in the short term, as well as the long term. Many circuit elements present within power inverters are susceptible to heat runaway, if the temperature of the power inverter exceeds a catalyst temperature, potentially leading to permanent damage and rendering the power inverter inoperable. Even if the power inverter operates below that catalyst temperature, excessive heat may cause electrical components to wear at an increased rate, shortening the operating life of the inverter.
In addition, it is well known that power inverters do not operate at 100% efficiency, as there are inherent losses in power from circuit impedance, current switching, and from the transformer itself. While some sophisticated power inverters may operate at or near 95% maximum efficiency, the efficiency of most power inverters diminishes substantially as the temperature within the power inverter increases—sometimes going as low as 70%, or even lower, before failure occurs. Some more advanced power inverters artificially throttle the amount of power being converted based on the detected temperature, to mitigate potential damage that might otherwise occur from heat runaway. For these reasons, power inverters typically include built-in fans that serve to cool the inverter, and protection circuitry for throttling and/or emergency shutdowns.
Many electric vehicles and hybrid vehicles incorporate one or multiple power inverters to facilitate the conversion of DC power stored in batteries, to AC power for use throughout the vehicle (e.g., electric motors, regenerative braking systems, etc.). Likewise, electric and hybrid vehicles often include AC-to-DC converters, which operate in a similar fashion and whose performance also diminishes as their temperatures rise. There remains an ongoing challenge to provide electric vehicles that are robust and have comparable longevity to that of gasoline-based vehicles. It is therefore an object of the present disclosure to provide a cooling system to improve the longevity of power inverters in electric vehicles.
Because electric vehicles rely on stored battery power for propulsion (and to power the various subsystems of the vehicle), the distance across which an electric vehicle can travel on a single charge depends, in part, on the efficiency of power conversion between DC power and AC power (and vice versa). Thus, the difference in 5-10% conversion efficiency could substantially impair the performance or usefulness (e.g., range) of an electric vehicle. It is therefore another object of the present invention to provide a cooling system that maintains the temperature of a power inverter efficiently and effectively, to thereby ensure that its power conversion efficiency remains at or near its peak level.
These and other objectives and advantages of the present invention will become apparent from the following detailed written description, drawing figures, and claims.
To accomplish the aforementioned objectives, embodiments of the present invention provide for a heat exchanger with a fin insert positioned therewithin that efficiently increases the transfer of heat from a surface of the heat exchanger into a coolant flowing around the fin insert, within the sealed heat exchanger housing 101. The present invention contemplates that a sheet of metal with convolutions formed therein has arcs or “peaks” that make direct contact with a surface being heated by, for example, a power inverter. Conventional fin structures may be shaped like a bellows (e.g., like a sine wave, as shown in
An example fin insert according to the present invention improves upon conventional fin structures by providing a structure with “omega-shaped” convolutions—that is, convolutions that are wider at one end, and narrower at the opposite end. An “omega” or teardrop-shaped fin may have its wider portion flattened to some extent, thereby providing significantly more contacting surface area between the fin insert and the heated wall. With more of the fin insert being in direct contact with the heated wall, the degree of heat transfer from the heated wall to the fin insert substantially increases. Because the fin insert increases the effective surface area being cooled by coolant flowing around and through the heat exchanger, the amount of cooling (and the effectiveness of the cooling) can be substantially improved.
The “omega-shaped” fin inserts of the present invention may be constructed, for example, by inserting shims or other objects into the fins to present portions of the fins from being compressed—and by subsequently applying an inward lateral force or series of forces (transverse to the direction of fluid flow through the fin insert) to deform the fins arounds the shims. In some embodiments, the mostly-formed fin inserts may then be pressed or sandwiched between two plates or other planar structures to flatten the tops and bottoms of the omega-shaped fins. In this manner, the amount of contacting surface area between the fin insert and the heated wall or plate substantially increases. The flattened regions contacting one or more surfaces of the heat exchanger may, in some implementations, be welded, brazed, or otherwise affixed to the inner surfaces of the heat exchanger housing elements—which can serve to further increase the contacting surface area between the fin insert and the heated wall.
In addition, some fin inserts according to the present invention may include lateral undulations, or “waves,” formed therein that extend longitudinally along the length of the fins. The undulations may serve to increase turbulence of coolant flowing through the heat exchanger, which increases the transfer of heat into the coolant flowing through and around the fin inserts. These undulations may likewise be formed by like-shaped shims and/or variations in transverse pressures applied collectively to the sides of the fins during the formation process.
According to a first aspect of the present invention, there is provided a heat exchanger for regulating the temperature objects using a coolant. The heat exchanger includes a bottom plate having a first end, a second end opposite the first end, an outer surface, and an inner surface opposite the outer surface. The bottom plate includes a first coolant port proximate the first end and a second coolant port proximate the second end. The heat exchanger also includes a top plate having a first end, a second end opposite the first end, an outer surface, and an inner surface opposite the outer surface. The top plate is sealedly engaged with the bottom plate for circulation of the coolant therethrough between the first and second coolant ports. The inner surface of the bottom plate and the inner surface of the top plate collectively defines a coolant chamber. The heat exchanger further includes a substantially planar fin insert operably situated between the top and bottom plates within the coolant chamber. The fin insert includes a first end positioned proximate the first coolant port and a second end positioned proximate the second coolant port. The fin insert also includes a plurality of fins that extend longitudinally between its first and second ends. Each fin of the fin insert may include (i) a pair of angled sidewalls that converge at one end and diverge at an opposite end and (ii) a substantially flat outer wall that extends across the pair of angled sidewalls at the end where the angled sidewalls diverge. The substantially flat outer wall includes a contacting portion that is in immediate contact with the inner surface of the top or bottom plate.
In some embodiments according to the first aspect, the plurality of fins laterally, collectively undulate between the first and second end of the fin insert.
In some embodiments according to the first aspect, the pair of angled sidewalls includes a first sidewall having a first angle, and a second sidewall having a second angle, where the first and second angles are equivalent (e.g., at the same but opposite angles relative to the vertical axis, “leaning” with approximately equal and opposite slopes).
In some embodiments according to the first aspect, the contacting portion has a first length. A distance between adjacent contacting portions may be of a second length. In these embodiments, the first length may be substantially equal to the second length. In other embodiments, the first length may be greater than the second length.
In some embodiments according to the first aspect, the pair of angled sidewalls at the converging end have a first gap extending therebetween of a first width. Similarly, the pair of angled sidewalls at the diverging end have a second gap extending therebetween of a second width. The second width may be larger than the first width.
In some embodiments according to the first aspect the pair of angled sidewalls at the converging end have a first gap extending therebetween of a first width that is greater than or equal to 1 millimeter, to enable passage of debris within a coolant therebetween.
According to a second aspect of the present invention, there is provided a method of forming a heat exchanger for regulating the temperature of objects using a coolant. The method involves providing a bottom plate having a first end, a second end opposite the first end, an outer surface, and an inner surface opposite the outer surface, the bottom plate comprising a first coolant port proximate the first end and a second coolant port proximate the second end. The method also involves providing a top plate having a first end, a second end opposite the first end, an outer surface, and an inner surface opposite the outer surface. The method further involves forming, in a sheet of metal, a plurality of convolutions that each extend longitudinally between a first end and a second end of the sheet of metal. Each convolution includes vertical sidewalls and arcs connecting the vertical sidewalls. Additionally, the method involves compressing the sheet of metal in an inward lateral direction to deform the plurality of convolutions. The inward lateral compression causes the vertical sidewalls of each convolution to be angled in the lateral direction. Further, the method involves compressing the deformed sheet of metal in an inward vertical direction to substantially flatten the arcs of each convolution and form a fin insert. The method also involves positioning the fin insert in between the top and bottom plates. The method additionally involves sealedly engaging the top and bottom plates to form a coolant chamber within the inner surface of the bottom plate and the inner surface of the top plate.
In some embodiments according to the second aspect, the method further involves forming, in the sheet of metal, a series of lateral, nested undulations that each extend longitudinally between the first and second ends of the sheet of metal.
In some embodiments according to the second aspect, compressing the sheet metal in the inward lateral direction may involve (i) positioning one or more objects between the plurality of convolutions that substantially prevents the deformation of the arcs during the step of compression, (ii) applying an inward lateral force to deform the plurality of convolutions about the one or more objects, and (iii) removing the one or more objects after said application of said inward lateral force.
In some embodiments according to the second aspect, compressing the sheet metal in the inward lateral direction may involve applying one or more inward lateral forces at respective longitudinal locations along the plurality of convolutions to, in turn, cause the vertical sidewalls of each convolution to be angled in the lateral direction.
In some embodiments according to the second aspect, sealedly engaging the top and bottom plates may involve (i) applying a brazing material at an interface between the top and bottom plates and (ii) heating at least the top and bottom plates to cause the brazing material to flow between and around the interface to sealedly engage the top and bottom plates.
In some embodiments according to the second aspect, the method also involves applying a brazing material between the substantially flattened arcs of the fin insert and the inner surfaces of the top and bottom plates. The method may further involve heating at least the top and bottom plates to cause the brazing material to flow between and around the substantially flattened arcs of the fin insert and the inner surfaces of the top and bottom plates, to restrainably attach said fin insert therebetween said top and bottom plates.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments and features will become apparent by reference to the drawing figures, the following detailed description, and the claims.
For a better understanding of the invention, and to show how the same may be implemented, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:
There will now be described by way of example, several specific modes of the invention as contemplated by the inventor. In the following description, numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description of the invention.
As described above, embodiments of the present invention provide for a substantially flat, planar (low-profile) heat exchanger with a fin insert positioned therewithin that provides for improved heat transfer from the heated component, with the surface of the heat exchanger, and, in turn, heated into the fin insert itself, positions within the flow of a fluid coolant. The improved geometric shape and construction of the fin inserts beneficially increases the surface area of contact, between the fins themselves and the heated surface of the heat exchanger, relative to conventional fin structures. In addition, the omega-fin shape as shown and described herein is believed to advantageously enable an increased number of fins or convolutions within the same volume, further increasing the total surface area to which heat can be transferred and drawn away, using the coolant fluid. The particular aspects of the fin shapes shown, described, and contemplated in the present disclosure are described in more detail with respect to
The shape of the fins in the fin insert may be constructed to prevent or reduce the potential for possible adverse issues that may arise due to the narrowing of the coolant passageways. For example, the omega-shaped fin may have central gap between adjacent sidewalls whose distance does not fall below a threshold minimum distance (e.g., 1 millimeter, among other possible distances), which may be determined based on the size of expected particle debris to pollute or constrict the flow of the recirculated coolant during operation. In this manner, the risk of failure or diminished performance due to blockages may be significantly reduced.
In an example implementation, the heat exchanger structure shown and described herein may be placed within an electronic device assembly. For example, one or more heat exchangers may be positioned above and/or below a circuit board that performs power inversion, power conversion, and/or serves any other function. In some cases, a heat exchanger may have electronic components positioned both above and below it, such that both the upper surfaces (in the positive z-direction) and the lower surfaces (in the negative z-direction) of the heat exchanger is in contact with an electronic device or circuit for temperature regulation. The entire assembly of heat exchangers and electronics may be enclosed within a collective housing, for example, which itself may be secured within an electric vehicle. The heat exchangers shown and described herein may therefore have no particular designated “cooling” or “heating” surface, and any such designation made herein is provided for explanatory purposes only.
Various aspects of the present heat exchangers and their constituent components—including the sizes, shapes, and arrangement of plates, apertures, fins, and channels through which coolant flows—may be specifically tuned, modified, or otherwise adjusted based on the particular requirements and/or constraints of a specific application. For example, the severity of the undulations may depend on the flow rate of coolant preferably pumped through the heat exchanger. As another example, the angles of the sidewalls of the fin structure may be increased or decreased for various reasons (e.g., to increase or decrease the number of convolutions that can fit within a particular volume, to increase or decrease the total contacting surface area between the fins and the inner walls of the heat exchanger, etc.). One of ordinary skill will appreciate that such variations may be undertaken to apply the principles of the present invention to a variety of implementations, without departing from the scope of the invention.
As described herein, “coolant” may refer to any fluid—including gas, liquid, or some combination thereof—serving as a medium that draws heat from cooling blocks to cool or otherwise thermally modulate an object or objects. Although a “coolant” may be described herein as a liquid, the present application is not limited to liquid coolants. Any recitation of “liquid coolant” should be understood to encompass coolants that may not necessarily be in a liquid state, but are nonetheless fluids.
As described herein, a “cooling surface” or “heating surface” may generally refer to any surface of a heat exchanger that is configured to transfer heat between a source and a destination. For example, the flat upper surface of the heat exchanger may be in direct contact with a battery, power inverter, or other circuitry in order to regulate the temperature of that object. In that example, the flat upper surface may serve as a “cooling surface” or a “heating surface.” Similarly, the lower surface underneath the heat exchanger (in the negative z-direction) may serve as a cooling or heating surface, if an object whose temperature is to be regulated is positioned proximate to the lower surface of the heat exchanger housing.
As described herein, a “fin” may refer to a single convolution, or a portion of a convolution, that forms a part of the multiple convolutions or fins of a fin insert. Each “fin” may include at least one arced or substantially flattened wall that is in direct contact with a surface of bottom plate 110 or top plate 150 of housing 101 (see
Although various examples of the present disclosure may refer to the transfer of heat in order to “cool” an object, it should be understood that an object may have a temperature that is below a desired operating temperature, and whose temperature could therefore be increased using fluid flowing through a heat exchanger that is comparatively warmer (e.g., to warm up a battery in the winter). Any description herein that describes a heat exchanger “cooling” an object also encompasses circumstances in which the heat exchanger can be used to “warm” an object. The scope of the present disclosure's heat exchangers is not limited only to cooling, but rather to temperature regulation generally.
The following description of
Referring now to
The top and outer surface of heat exchanger 100, and particularly heat exchanger housing 101—the surface in the positive z-direction shown in
In an example implementation, coolant may be pumped or otherwise drawn through inlet 112 and into a coolant chamber defined by inner surface 114 and inner surface 154 (e.g., the space formed between lower plate 110 and upper plate 150). That coolant may flow through and around fin insert 130 the coolant chamber and toward outlet 118, through which the coolant exits heat exchanger 100. The direction of coolant flow, may also be reversed, depending upon the particular implementation.
As shown in
Additionally, as shown in
As shown in
Fully-formed fin insert 130 of
Similar to
Referring now to
Referring again to
As shown in
As shown in
In addition,
Although certain example methods and apparatus have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatuses, and articles of manufacture fairly falling within the scope of the appended claims, either literally or under the doctrine of equivalents.
It should be understood that arrangements described herein are for purposes of example only. As such, those skilled in the art will appreciate that other arrangements and other elements (e.g. machines, interfaces, operations, orders, and groupings of operations, etc.) can be used instead, and some elements may be omitted altogether according to the desired results. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location, or as other structural elements described as independent structures may be combined.
While various aspects and implementations have been disclosed herein, other aspects and implementations will be apparent to those skilled in the art. The various aspects and implementations disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular implementations only, and is not intended to be limiting.
