Cooling system for power electronics

Abstract

A heat removal device operable to cool a heat-generating device includes a housing having a hollow interior and a base thermally couplable to the heat-generating device and arranged within the hollow interior of the enclosure. The base includes a cooling surface arranged at an incline. A plurality of fins protrude from the cooling surface and at least one first groove is formed in the cooling surface. A top cover is positioned upwardly adjacent to the plurality of fins. The top cover has one or more perforations formed therein.

Description

COOLING SYSTEM FOR POWER ELECTRONICSCROSS REFERENCE TO RELATED APPLICATIONSThis application claims the benefit of U.S. Application No. 63 / 639859, filed on April 29, 2024, which is incorporated herein by reference in its entirety.BACKGROUND

[0001] Exemplary embodiments pertain to the art of cooling devices, and more particularly to cooling device used to cool power electronics.

[0002] Power electronics devices such as motor drives generate waste heat during operation of the device. Additionally, when the power electronics devices heat up, the operational efficiency of the devices can degrade adding to the amount of heat generated. When utilized in a refrigeration system to drive, for example, a compressor of the refrigeration system, effective thermal integration of these devices can be important aspect to the system’s overall efficiency and reliability. Consequently, a goal of the system integrator is to maintain these components within a range of operating temperatures which will maximize the system efficiency. Accordingly, there remains a need in the art for a cooling device or heat sink that can closely integrate with power electronic devices which can maintain optimal temperatures for these components under a variety of load conditions.

[0003] Heat transfer performance of a heat sink can be improved via one or more of the following methods: (i) increasing the heat transfer surface area of the heat sink, (ii) promoting two phase flow such nucleate boiling on the surface of the heat sink that is in contact with the boiling fluid, (iii) promoting external natural convection at the enhanced surface of the heatsink, and (iv) promoting convection boiling or thin film boiling in the heat sink.

[0004] In the nucleate or thin film boiling process, initially, a small quantity of entrapped vapor, in the form of a bubble, in the nucleation sites grows due to the heat transferred from the heated surface. When the bubble grows, it vaporizes more liquid in contact with the solid surface and also vaporizes at the liquid- vapor interface. Heat from the solid surface and from the surrounding superheated liquid superheats the vapor in a bubble causing the bubble to grow in size. When the bubble is large enough, the surface tension of the bubble is overcome by the buoyancy force causing the bubble to detach from the surface. As the bubble leaves the surface, liquid enters the volume vacated by the bubble. This movement of the bubble results in a convection current in the liquid. Some traces of vapormay remain in the volume and become a source of additional liquid to vaporize to form another bubble. The periodic formation of bubbles at the surface, the release of the bubbles from the surface, and the rewetting of the surface together with the convective effect of the vapor bubbles rising through the liquid results in an improved heat transfer rate for the heat transfer surface.

[0005] However, some configurations of thin film boiling will dry out quickly resulting in poor heat transfer. There is therefore an need for newly configured heat transfer tubes with improved heat transfer capabilities.BRIEF DESCRIPTION

[0006] According to an embodiment, a heat removal device operable to cool a heatgenerating device includes a housing having a hollow interior and a base thermally couplable to the heat-generating device and arranged within the hollow interior of the enclosure. The base includes a cooling surface arranged at an incline. A plurality of fins protrude from the cooling surface and at least one first groove is formed in the cooling surface. A top cover is positioned upwardly adjacent to the plurality of fins. The top cover has one or more perforations formed therein.

[0007] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the base includes a contact surface and a plurality of sidewalls are arranged between the contact surface and the cooling surface. The plurality of sidewalls include a first end, a second end, a first lateral side, and a second lateral side. A height of the first end is different than the height of the second end.

[0008] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the contact surface has a horizontal orientation.

[0009] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the contact surface has a vertical orientation.

[0010] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the height of the base is constant between the first lateral side and the second lateral side.

[0011] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that at least one of the plurality of fins includes a plurality of fin members separated by one or more cuts.

[0012] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the plurality of fins extends between the first end andthe second end and the one or more cuts are arranged at an angle relative to a direction of flow across the cooling surface.

[0013] In addition to one or more of the features described herein, or as an alternative, further embodiments may include at least one continuous cut extending across the base at an angle greater than 0 degrees and less then 90 degrees relative to the plurality of fins such that the plurality of fin members of adjacent fins of the plurality of fins are staggered along a direction of flow across the cooling surface.

[0014] In addition to one or more of the features described herein, or as an alternative, further embodiments may include at least one recess formed in the cooling surface. The at least one recess extends at a non-parallel angle to the at least one first groove.

[0015] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one recess is oriented parallel to at least one of the first end and the second end.

[0016] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one recess has a bottom recess surface oriented being parallel to the contact surface of the base.

[0017] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one recess has a bottom groove surface oriented parallel to the cooling surface of the base.

[0018] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that at least one of the at least one first groove and the at least one recess is filled with a porous material.

[0019] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one recess includes a plurality of recesses and a distance between adjacent recesses is non-uniform.

[0020] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the top cover has a plurality of first perforations formed therein.

[0021] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the top cover includes at least one second perforation formed therein. The at least one second perforation has a different configuration than the plurality of first perforations.

[0022] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one second perforation is vertically aligned with the at least one recess.

[0023] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that at least one of the plurality of fins and the cooling surface has a roughened surface.

[0024] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that at least one of the plurality of fins and the cooling surface has a metal porous spray coating.

[0025] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the base includes a plurality of base modules arranged in series relative to a direction of flow through the hollow interior of the enclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

[0027] FIG. 1 is a schematic diagram of an example of a refrigeration system according to an embodiment;

[0028] FIG. 2 is a schematic diagram of another example of a heating, ventilation, air conditioning and refrigeration (HVAC&R) system according to an embodiment;

[0029] FIG. 3 is an illustration of an embodiment of a cooling system for cooling a heat-generating device according to an embodiment;

[0030] FIG. 4 is a schematic diagram of a heat removal device of a cooling system according to an embodiment;

[0031] FIG. 5 is a schematic diagram of a heat removal device of a cooling system according to another embodiment;

[0032] FIG. 6 is a schematic diagram of a heat removal device of a cooling system during operation according to an embodiment;

[0033] FIG. 7 is a schematic diagram of a heat removal device of a cooling system including a plurality of base modules according to an embodiment;

[0034] FIG. 8 is a detailed perspective view of a heat removal device of a cooling system according to an embodiment;

[0035] FIG. 9 is a detailed perspective view of another heat removal device according to an embodiment;

[0036] FIG. 10 is a detailed perspective view of a heat removal device according to an embodiment;

[0037] FIG. 11 is a detailed perspective view of another heat removal device according to an embodiment;

[0038] FIG. 12 is a graph representing test data associated with a horizontally oriented heat removal device; and

[0039] FIG. 13 is a graph representing test data associated with a vertically oriented heat removal device.DETAILED DESCRIPTION

[0040] A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

[0041] Referring to FIG. 1, an example of a refrigeration system, such as a heating, ventilation, air conditioning and refrigeration (HVAC) system 20 is schematically illustrated. Exemplary refrigeration systems 20 include, but are not limited to, residential, split, packaged, chiller, rooftop, supermarket, transport, and fuel cell systems, for example. In the illustrated, non-limiting embodiment, the refrigeration system 20 includes a refrigeration circuit 22 including a compressor 24, a condenser 26, an expansion device 28 and an evaporator 30 arranged in series and having a volume of refrigeration fluid, such as refrigerant for example, flowing therethrough.

[0042] Another example of a refrigeration system 20 is illustrated in FIG. 2. In addition to the compressor 24, condenser 26, expansion device 28, and evaporator 30 previously described the refrigeration circuit 22 includes an economizer heat exchanger 32. The economizer heat exchanger 32 may be positioned between the condenser 26 and the expansion device 28 relative to a flow of refrigeration fluid through the refrigeration circuit 22. Although the economizer heat exchanger 32 is illustrated as being located directly downstream from the outlet 34 of the condenser 26, it should be understood that embodiments where one or more other components of the refrigeration system 20 are located between the condenser 26 and an inlet of the economizer heat exchanger 32 are also contemplated herein.

[0043] In an embodiment, the economizer heat exchanger 32 is a brazed plated fin heat exchanger. However, other suitable types of heat exchangers are also within the scope of the disclosure. Further, the economizer heat exchanger 32 is a refrigeration fluid-refrigerationfluid heat exchanger and therefore has a plurality of distinct fluid flow paths formed therein. In the illustrated, non-limiting embodiment, the economizer heat exchanger 32 has a first flow path and a second flow path, respectively.

[0044] In the illustrated, non-limiting embodiment, the inlet 36 of the first flow path of the economizer heat exchanger 32, also referred to herein as the “main flow path,” is arranged in direct fluid communication with an outlet 34 of the condenser 26. Alternatively, or in addition, the outlet 38 of the main flow path of the economizer heat exchanger 32 may be arranged directly upstream from and in fluid communication with an inlet of the expansion device 28.

[0045] In operation, a first portion R1 of the refrigeration fluid output from the condenser 26 is provided to the main flow path of the economizer heat exchanger 32 via a main conduit 40. Although the main flow path is illustrated as a single pass through the economizer heat exchanger 32, it should be understood that in other embodiments the main flow path may include a plurality of passes through the economizer heat exchanger 32. At the outlet 38 of the main flow path of the economizer heat exchanger 32, the first portion R1 of the refrigeration fluid is configured to flow to the expansion device 28. From the expansion device 28, the refrigeration fluid is expanded within the evaporator 30. The first portion R1 of refrigeration fluid output from the evaporator 30 is provided via a first compressor inlet path to a primary suction inlet 42 of the compressor 24. Accordingly, the fluid loop of the first portion R1 of the refrigeration fluid includes the compressor 24, condenser 26, main flow path of the economizer heat exchanger 32, expansion device 28, and the evaporator 30.

[0046] An economizer expansion device 44 may be arranged within the refrigeration circuit 22 in fluid communication with the condenser 26. The economizer expansion device 44 is operable to expand and cool the refrigeration fluid provided thereto. Although the economizer expansion device 44 is illustrated as being disposed within an economizer conduit 45 fluidly coupled to an extending from the main conduit 40 at a location upstream from the first inlet 36, it should be understood that an economizer conduit 45 fluidly connected to the outlet 34 of the condenser 26 in another suitable manner is also contemplated herein.

[0047] Located downstream from the economizer expansion device 44 is the inlet 46 of a second flow path of the economizer heat exchanger 32, also referred to herein as the “economizer flow path.” Further, the outlet 48 of the second flow path of the economizer heat exchanger 32 may but need not be directly connected to an economizer inlet or port 50 of the compressor 24. In the illustrated, non-limiting embodiment, the inlet 36 of the main flow pathand the inlet 46 of the economizer flow path are arranged at adjacent sides of the economizer heat exchanger 32. However, in other embodiments, it should be understood that the inlets 36, 46 of both flow paths could alternatively be arranged at the same side of the economizer heat exchanger 32 or at opposite sides thereof. Similarly, the outlets 38, 48 of both the main flow path and the economizer flow path may be arranged at opposite sides, the same side, or adjacent sides depending on the desired flow configuration of the economizer heat exchanger 32. Further, although the economizer flow path is illustrated as a single pass, it should be understood that in some embodiments, the economizer flow path may include a plurality of passes through the economizer heat exchanger 32.

[0048] Within the economizer flow path, a second portion R2 of the refrigeration fluid is configured to absorb heat from the first portion R1 of the refrigeration fluid within the main flow path, thereby cooling the first portion R1 of the refrigeration fluid. As a result of this heat transfer, the second portion R2 of the refrigeration fluid within the economizer flow path may become a vapor. From the outlet 48 of the economizer flow path, the second portion R2 of the refrigeration fluid is provided to the economizer suction inlet 50 located at an intermediate portion of the compressor 24. Accordingly, the second portion R2 of the refrigeration fluid bypasses the expansion device 28 and the evaporator 30 of the refrigeration circuit 22. Within the compressor 24 the first portion R1 and the second portion R2 of refrigeration fluid are mixed before being provided to the discharge port 52 to repeat the cycle. Accordingly, the fluid loop of the second portion R2 of the refrigeration fluid includes the compressor 24, condenser 26, economizer expansion device 44, and economizer flow path of the economizer heat exchanger 32. It should be understood that the refrigeration systems 20 illustrated and described herein are intended as an example only, and that a refrigeration system 20 having another configuration is within the scope of the disclosure.

[0049] With continued reference to both FIGS. 1 and 2 and further reference to FIG. 3, in an embodiment, the refrigeration system 20 includes a cooling system 60 including at least one heat removal device 100 for cooling one or more heat-generating devices 62. As shown, the cooling system 60 may be fluidly connected to the refrigeration system 20 and configured to receive a flow of refrigerant from a location downstream from the condenser 26 and upstream from both inlets 36, 46 or from the outlet of the economizer or after the expansion valve of the economizer heat exchanger 32. 201 could be an expansion valve if the fluid is received from upstream of the economizer or expansion valve 28. The term “heatgenerating device” as used herein can refer to any electronic component which generates heat during operation thereof. Examples of a heat-generating devices 62 include, but are notlimited to a processor, power electronic devices, or another device that can provide a controlled output power by modulating and / or converting a supplied input power (e.g., a variable frequency drive, power rectifier, power converter, and the like). Such a heatgenerating device 62 can be used to control the speed of a compressor and / or the speed of a fan associated with of a refrigeration system based on various predetermined system conditions. In the illustrated, non-limiting embodiment of FIG. 2, the at least one heatgenerating device 62 includes a variable frequency drive operably coupled to the compressor 24 of the refrigeration system 20.

[0050] As shown, the heat removal device 100 may be a heat sink mountable in overlapping arrangement with and thermally couplable to at least one heat-generating device 62, and in some embodiments a plurality of heat-generating devices 62. Several variations of a heat removal device are illustrated in FIGS. 4-11. In each of the illustrated, non-limiting embodiments, the heat removal device 100 includes a base 102 formed from any suitable material or substrate. The footprint of the base 102 may be similar or substantially identical in size and / or shape to a surface of the heat-generating device 62 associated therewith. Alternatively, the footprint of the base 102 may be larger than the surface of the heatgenerating device 62. However, it should be understood that embodiments where the footprint of the base 102 is smaller than the surface of the heat- generating device 62 are also within the scope of the disclosure. The base 102 may be positionable in direct contact with the surface of a heat-generating device 62 such that the base 102 is directly thermally coupled to the heat-generating device 62. However, in other embodiments, the base 102 may be thermally coupled to a heat- generating device 62 via an intermediate component (not shown), such as a heat spreader for example. The base 102 is more likely to be arranged in direct contact with the surface when the footprint of the base 102 is equal to or smaller than the surface. In instances where the base 102 is larger than the surface of the heat-generating device 62, the base 102 is more likely to be connected to the surface via an intermediate component.

[0051] As shown, the footprint of the base 102 may be generally rectangular in shape. However, embodiments of the base 102 having another shape are also contemplated herein. In the illustrated, non-limiting embodiments, the base 102 has a contact surface 104, a cooling surface 106, and at least one sidewall extending between and connected to the contact surface 104 and the cooling surface 106. The at least one sidewall may include a plurality of sidewalls, such as a first end 108, a second, opposite end 110, a first lateral side 112 (see FIG. 8) extending between the first end 108 and the second end 110, and a second lateral side 114(FIG. 8) extending between the first end 108 and the second end 110. In an embodiment, the contact surface 104 of the base 102 is arranged in contact with and is thermally coupled to the one or more heat-generating devices 62.

[0052] The cooling surface 106 of the base 102 may be arranged at a non-parallel angle relative to the contact surface 104 of the base 102. In an embodiment, the height of the base 102, measured between the contact surface 104 and the cooling surface 106 thereof, varies over at least one dimension of the base 102. For example, as shown in FIGS. 4-6, the height may vary between the first end 108 (Hl) and the second end 110 (H2). However, as shown, the height is constant at any location between the first lateral side 112 and the second lateral side 114. In other embodiments, the height may vary between the first lateral side 112 and the second lateral side 114 and may be constant between the first end 108 and the second end 110. In other embodiments, the height may vary in a plurality of directions such that the height of the base between the first end 108 and the second end 110 varies from the first lateral side 112 to the second lateral side 114.

[0053] In the illustrated, non-limiting embodiments of FIG. 4-6 and 8-10, the height of the base 102 varies uniformly between the first end 108 and the second end 110. As shown, the height uniformly increases from the first end 108 to the second end 110 such that the cooling surface 106 of the base 102 has a substantially constant or continuous slope between the first end 108 and the second end 110. The height at the second end 110 may be more than double the height at the first end 108. However, embodiments where height at the second end 110 is greater than the height at the first end 108, but less than double the height of the first end 108 are also contemplated herein. For example, the height at the second end 110 may be only slightly greater than the height at the first end 108, such as 105% of the height at the first end 108.

[0054] The angle represented by the increase in the height of the base 102 between the first end 108 and the second end 110 is shown at a. In an embodiment, the angle a of the cooling surface 106 relative to the contact surface is between about 5 degrees and about 60 degrees, such as between about 10 degrees and about 55 degrees, between about 10 degrees and about 40 degrees, between about 10 degrees and about 30 degrees, between about 15 degrees and about 50 degrees, and in some embodiments, is 45 degrees.

[0055] In an embodiment, the heat sink 100 is configured to facilitate nucleate boiling. Thin film evaporation, which occurs when subsurface volumes of the heat sink mostly filled with vapor and liquid adheres to the wall as a film, contributes to the steady evaporation process. By configuring the cooling surface 106 of the heat sink 100 to haverelatively large communicating subsurface channels with relatively smaller openings to the surface, the cooling surface 106 promotes thin film evaporation, thereby enhancing heat transfer performance of the cooling surface 106. Similar to nucleate boiling, the heat transfer that occurs at the cooling surface 106 can be further enhanced by inducing both flow boiling and thin film evaporation at the cooling surface 106.

[0056] Several different configurations of the cooling surface 106 of the heat sink 100 may promote thin film evaporation and / or flow boiling thereat. In the illustrated, non-limiting embodiments, a plurality of fins 120 (best shown in FIG. 8) extend from the cooling surface 106, such as in a direction of flow of the refrigerant over the cooling surface. The fins 120 may be separate components affixed to the base 102, or alternatively, may be integrally formed with the base 102. Further, although the fins 120 are shown oriented substantially perpendicular to the cooling surface 106, embodiments where the fins 120 are arranged at another angle relative to the cooling surface 106 are also within the scope of the disclosure. Although the plurality of fins 120 is illustrated as including 8 fins spaced over the cooling surface 106 between the first and second lateral sides 112, 114 of the base 102, embodiments having any suitable number of fins within a given area are contemplated herein. In an embodiment, the cooling surface 106 includes between about 10 fins and about 60 fins per inch.

[0057] At least one of the plurality of fins 120 may extend continuously between the first end 108 and the second end 110 of the base. In the illustrated, non-limiting embodiment, the plurality of fins 120 are oriented substantially parallel to one of the first lateral side 112 and the second lateral side 114 of the base 102 and / or a direction of flow across the cooling surface 106. Further, adjacent fins 120 are laterally spaced from one another between the first and second laterals sides 112, 114. However, in other embodiments, the one or more fins 120 may be arranged at a non-parallel angle to at least one of the first lateral side 112 and the second lateral side 114 of the base 102.

[0058] The height of a fin 120 defined between the cooling surface 106 and a distal end of the fin 120 may be between about 0.2 mm and about 50 mm. While the fins 120 are generally illustrated as being rectangular in shape (in one or more of a plan view and a cross- sectional view) embodiments where a fin 120 has another configuration are also contemplated herein.

[0059] As shown, one or more cuts or grooves may be formed in at least one of the fins 120 to form a plurality of separate fin members 124 associated with a respective fin 120. Each cut formed in a fin 120 may be uniform resulting in a plurality of substantially identicalfin members 124, or alternatively, the cuts formed in a fin 120 may vary, resulting in a plurality of fin members 124 having varying configurations at the same fin 120. Further, each of the plurality of fins 120 may but need not have an identical configuration. For example, adjacent fins 120 may have the same number or a different number of fin members 124. In an embodiment, a continuous cut extends from the first lateral side 112 to the second lateral sidell4 of the base 102, and therefore through each of the plurality of fins 120 arranged at the base 102. In some embodiments, as shown in the FIGS., when the continuous cut is oriented relative to the fins 120 at an angle greater than 0 degrees and less than 90 degrees, the fin members 124 formed in adjacent fins 120 are staggered or offset relative to one another in a direction of flow. However, in other embodiments, such as where the continuous cut is substantially perpendicular to the fins 120, the fin members 124 of adjacent fins may be in rows extending between the first lateral side 112 and the second lateral side 114 of the base 102, respectively.

[0060] The orientation of the fin members 124 formed in adjacent fins 120 is determined by the angle of the cut or grooves formed in each of the fins 120. The cuts formed in one or more of the fins 120 may be oriented substantially perpendicular to the direction of flow over the cooling surface 106, or alternatively, may be arranged at another non-parallel angle relative to the direction of flow. Further, in some embodiments as shown, a cut may have a continuous orientation over its length extending between the first and second lateral sides 112, 114.

[0061] In an embodiment, the cuts are arranged at an angle greater than 0° and less than 90° relative to the direction of flow across the cooling surface 106. Accordingly, each fin member 124 may be generally diamond in shape and may have a constant rectangular cross-section over its height. However, embodiments where a fin member 124 has another shape, such as where one or more fin members 124 are cylindrical and have a circular cross- sectional shape for example, are also within the scope of the disclosure. In some embodiments, a size and / or shape of the cross-section of the fin members 124 may vary over its height resulting in a non-uniformly shaped fin member 124. For example, a cross-sectional area of a fin member 124 may be lowest at a near a middle of the fin member 124, resulting in a mushroom-like shape. Further, although the plurality of fin members 124 are illustrated and described herein as being uniform, embodiments where the plurality of fin member 124 at the same fin 120 or at different fins 120 have different shapes are also contemplated herein.

[0062] The cuts may extend through only a portion of the height of a fin 120. Accordingly, in an embodiment, the height of the fin member 124 may be between about10% and about 90% of the height of a fin, and in some embodiments between about 30% and about 70% of the height of a fin 120. Further, the distance between the center of two adjacent fin members 124 formed in the same fin 120, represented by Cl in Figure 8, and also referred to herein as the notch pitch, may be between about 0.5 mm and about 10 mm. Alternatively, or in addition, the distance between the center of a fin members 124 formed in a first fin 120 and the distance of a fin member 124 formed in an adjacent second fin 120 spaced laterally from the first fin, represented by C2 and also referred to herein as a lateral pitch, may be between about 0.2mm and about 50 mm. In an embodiment, the notch pitch Cl of adjacent fin members 124 formed in the same fin 120 may be equal to the lateral pitch C2 between fin members 124 formed in adjacent fins. However, embodiments where the pitch Cl is different, for example bigger or smaller than the lateral pitch C2 are also within the scope of the disclosure.

[0063] A first groove 130 may be formed in the base 102, such as in the cooling surface 106 between adjacent fins 120. In embodiments including a plurality of fins 120, a plurality of first grooves 130 may be formed in the cooling surface 106. In such embodiments, the plurality of first grooves 130 may be substantially identical or alternatively, may vary. In an embodiment, at least one first groove 130 extends over a substantial length of the base 102, such as from the first end 108 to the second end 110 thereof. However, embodiments where a first groove 130 extends over only a portion of the length of the base 102 is within the scope of the disclosure. For example, the first groove 130 may extend until reaching a recess 132, as will be described in more detail below, and may extend after the recess 132.

[0064] In embodiments including one or more first grooves 130, the first grooves 130 may have an inclined or sloped configuration. The incline may be the result of the varying height of the base 102, or alternatively or in addition, may be due to a variable height of the first groove 130 itself. The incline in combination with the first grooves 130 will cause a fluid, such as single-phase or two-phase mixture for example, to flow over the length of the first grooves 130 in a direction of flow. This inclined configuration can help vapor bubbles slide along the groove 130 due to buoyancy effect which can activate thin film evaporation.

[0065] Alternatively, or in addition to the at least one first groove 130, the base 102 may have one or more second grooves or recesses 132 formed therein. With reference to FIG. 11, the one or more recesses 132 may be arranged at a non-parallel angle relative to the first grooves 130. In an embodiment, the one or more recesses 132 are oriented substantially perpendicular to the first grooves 130. Recesses 132 are provided to vent the vapor in nearhorizontal orientation or horizontal orientation i.e., when a is close to 0-20 deg. This venting helps in directing vapor flow from end 108 to 110 also avoids vapor blanketing. As shown, the one or more recesses 132 may generally extend across the width of the base 102, such as from the first lateral side 112 of the base 102 to the second lateral side 114 of the base 102, or alternatively, may extend over only a portion of the width of the base 102. Although only a single recess 132 is illustrated in FIG. 11, it should be appreciated that embodiments including more than one recess 132 are also within the scope of the disclosure. In embodiments including a plurality of recesses 132, the recesses 132 may be spaced non- uniformly over the length of the base 102, between the first and second ends 108, 110. Varying the distance between adjacent recesses 132 may prevent the occurrence of liquid flooding.

[0066] In embodiments where the height of the base 102 varies, the height or depth of a recess 132 relative to the cooling surface 106 of the base 102 may similarly vary to form a recess 132 having a substantially horizontal bottom recess surface 134. In such embodiments, the plane including the bottom recess surface 134 of the recess 132 is arranged at a nonparallel angle to the plane defined by the cooling surface 106 of the base 102. However, in other embodiments, such as where the recess 132 has a uniform depth for example, the recess 132 may having a bottom recess surface 134 that is substantially parallel to the cooling surface 106 of the base 102. In the illustrated non-limiting embodiment, a depth of the at least one recess 132 (measured between the cooling surface 106 to the bottom groove surface 134) is larger than a corresponding depth of the one or more first grooves 130. It should be understood that embodiments where a depth of one or more first grooves 130 is equal to or greater than the depth of one or more recesses 132 are also within the scope of the disclosure.

[0067] The one or more recesses 132 may intersect and therefore be arranged in fluid communication with one or more first grooves 130 formed in the base 102. In embodiments where at least one recessl32 is fluidly coupled to a plurality of first grooves 130, the plurality of first grooves 130 are fluidly interconnected to one another by the recess 132. Inclusion of one or more recesses 132 in the cooling surface 106 of the base 102 may assist in venting vapor from the heat removal device 100 and the formation of shorter length vapor bubbles.

[0068] In some embodiments, the heat removal device 100 includes a top cover or plate 140 positioned upwardly adjacent to a distal end of one or more of the fins 120 and / or fin members 124. The top cover 140 may be formed from any suitable material. Examples of such materials include metal, such as aluminum or steel, composite, or plastic. The top cover 140 may be permanently affixed to the plurality of fins 120 and / or fin members 124, oralternatively may be movably arranged thereon. In embodiments where in the top cover 140 is permanently affixed to the fins 120 and / or fin members 124, it should be appreciated that the top cover 140 may be integrally formed with the fins 120 and / or fin members 124. The top cover 140 may be substantially identical in size and shape to the cooling surface 106 of the base 102. However, embodiments where the top cover 140 is a different shape than the cooling surface 106 of the base 102 and embodiments where the top cover 140 differs in size from the cooling surface 106 of the base 102 are also contemplated herein.

[0069] Further, as shown in FIGS. 9-11, the top cover 140 may have a plurality of through holes or perforations formed therein. In an embodiment, the top cover 140 includes a plurality of substantially identical first perforations 142. Although the first perforations 142 are illustrated as being circular in shape, it should be understood that embodiments including first perforations having another configuration are also within the scope of the disclosure. Further, the plurality of first perforations 142 may but need not be generally uniformly spaced over the top cover 140.

[0070] In the illustrated, non-limiting embodiment of FIG. 9, the top cover 140 has only a plurality of first perforations 142. However, in other embodiments, such as shown in FIGS. 10 and 11, the top cover 140 may alternatively or additionally include at least one second perforation 144. The second perforations 144 may have a different configuration, for example size and / or shape, than that of the first perforations 142. The second perforations 144 may be intended to provide a passageway through which a vaporized cooling fluid can vent from the heat removal device 100. In the illustrated, non-limiting embodiment, each second perforation 144 has an elongated shape and is oriented substantially parallel to the one or more recesses 132 formed in the base 102. In some embodiments, a second perforation 144 is located at a position of the top cover 140 in substantially vertical overlapping arrangement or alignment with a recess 132. In such embodiments, at least one dimension of the second perforation 144 may be larger than the corresponding recess 132 associated therewith. Other embodiments where a second perforation 144 is not arranged adjacent to a recess 132, such as shown in FIGS. 10 and 11, are also contemplated herein.

[0071] The top cover 140 in combination with the base 102 having a plurality of fins 120 and / or fin members 124 may create a cavity structure. As a cooling fluid, such as refrigerant or dielectric fluid for example, contacts the cooling surface 106 of the heat removal device 100, at least a portion of the cooling fluid will vaporize. A channel or flow path may be defined between the cooling surface 106 of the base 102, such as a first groove 130 formed therein, the sides of the fins 120 and / or fin members 124 closest to the firstgroove 130, and the solid portion of the top cover 140 arranged above the first groove 130. In an embodiment, some of the vapor cooling fluid may be configured to move through the at least one flow path resulting in the formation of a vapor bubble. For example, vapor formed near the first end 108 of the base 102 may travel upwardly through the at least one flow path toward the second end 110 of the base 102. The presence of a recess 132 at a location along the at least one flow path will interrupt the formation of a vapor bubble, thereby limiting the length of the vapor bubbles that are formed.

[0072] The top cover 140 may be operable to control the boiling of the cooling fluid that occurs at the heat removal device 100. A portion of the vapor cooling fluid arranged within a flow path may be able to vent or escape through the plurality of perforations 142, 144 formed in the top cover 140 over the length of the flow path. In an embodiment, the vapor that escapes from the heat removal device 100 via the perforations 142, 144 in the top cover 140 develops a thin film of liquid cooling fluid on the surface on the top cover 140. Any excess liquid may fall from the surface of the top cover 140 back to the base 102 or the fins 120 via a perforation 142, 144 in the top cover 140.

[0073] The purpose of the heat sink 100 disclosed herein is to facilitate thin film boiling. As the base 102 of the heat sink 100 is in contact with heat generating device 62, heat will transfer to the cooling fluid present at the finned side of the heat sink 100. This heat causes the cooling fluid at the heat sink 100 to boil due to bubble nucleation. As the bubbles merge, the bubbles form a larger bubble. If the heat sink was in a horizontal orientation, and the base of the heat sink had a constant height, the resulting vapor bubble would tend to grow horizontally in response to resistance provided by a top cover. This would lead to local dry out of the finned structure resulting poor heat transfer. To overcome this dry out, the cooling surface 106 of the heat sink 100 has a differential height such that a first groove 130 formed in the cooling surface 106 is arranged at an incline. This incline promotes a sliding movement of the bubbles formed within the first grooves 130. In addition, there will be flow along the first groove 130 as cooling fluid travels between an inlet and an outlet of the heat sink 100. These two flow inducing factors and the resistance provided by top cover 140 promote movement of a bubble of cooling fluid along the inclined first groove 130. As a bubble travels, it will sweep over other nucleating bubbles arranged along its flow path to create a thin film of liquid along the walls of the at least one flow path. This thin film evaporates due to heat coming from heat generating device 62 and is an ultra-efficient heat transfer mechanism.

[0074] The high heat transfer and evaporation rates result in generation of a large volume of vapor. If the incline of the first grooves 130 is insufficient, the vapor will note move efficiently, resulting in local dry out than can significantly reduce the heat transfer. Space constraints of an application may limit an incline of a heat sink 100. In such embodiments, larger second perforations 144, such as shown in FIGS. 10 and 11, may be formed in the top cover 140 at specific locations to facilitate vapor venting. Alternatively, or in addition, inclusion of a recess 132 may facilitate vapor venting from the cooling surface 106 of the heat sink 100. As previously noted, a recess 132 may but need not be aligned with a larger second perforation 144 formed in the top cover 140 to release the vapor from a given section of the heat sink 100.

[0075] It may be desirable that liquid or liquid film always wets the heat transfer surface (formed by 106, 124, 120, 140) of a flow path of the heat removal device 100. In an embodiment, the wetting of the fins 120 and / or fin members 124 may be enhanced by texturizing or roughening a surface of one or more of the plurality of fins 120 and / or fin members 124. This roughened surface may be achieved via any suitable mechanism. For example, a mechanical process, such as knurling, may be performed on the surface of the fins 120 and / or fin members 124 to increase the roughness thereof. Alternatively, or in addition, a coating, such as a metal porous spray coating for example, may be applied about an exterior surface of one or more of the fins 120 and / or fin members 124. In an embodiment, one or more of the first grooves 130 and / or one or more recesses 132 may be partially filled with a porous material to enhance the liquid wicking near the cooling surface 106 of the base 102. For example, a flow path or channel defined between the cooling surface 106 of the base 102, the sides of the adjacent fins 120 and / or fin members 124 and the top cover 140 may have a porous material therein. The porous material may be metal foam; however other porous materials are also within the scope of the disclosure.

[0076] In an embodiment, as shown in FIG. 7, vapor venting can be achieved via a modular heat sink 100. As shown, the heat sink 100 includes a plurality of base modules, represented at lOla-lOld, each including a base 102, an inclined cooling surface 106, one or more fins 120 and / or fin members 124, and one or more first grooves 130 as previously described herein. Further, one or more of the base modules may optionally include at least one recess 132 and a top cover 140 as previously described herein. The base modules may be arranged in series along the flow path between the inlet and the outlet such that the second end 110 of one base module is aligned with and directly upstream from the first end 108 of another base module. Inclusion of a plurality of base modules within a heat sink 100 may beused to provide a greater inclined surface in applications having a constrained space. It should be appreciated that plurality of base modules associated with a heat sink 100 may have the same configuration, or alternatively may have different configurations.

[0077] The heat removal device 100, and in some embodiments the one or more adjacent heat-generating device 62, may be part of a closed loop system. In an embodiment, the cooling surface 106 is completely enclosed within the interior 152 of a housing or top cover 150 of the heat sink 100. As shown in FIGS. 4-6, the housing 150 includes and inlet 154 and an outlet 156 defining a flow path of the cooling fluid through the interior 152 of the heat sink 100. In such embodiments, the at least one heat-generating device 62 may not be arranged within the interior 152 of the housing 150. Inclusion of a housing 150 may facilitate the use of the heat removal device in a plurality of configurations, such as a horizontal configuration, as shown in FIGS. 4 and 6, and a vertical configuration, as shown in FIG. 5. However, it should be appreciated that embodiments where the heat removal device 100 is arranged at another configuration are also within the scope of the disclosure.

[0078] Within the housing 150 at least a portion of the heat removal device 100, such as the first end 108 of the base 102 for example, is submerged in a cooling fluid during normal operation. Accordingly, the mass and / or flow rate of the cooling fluid that vaporizes via interaction with the heat removal device 100 and is provided to the outlet associated therewith may be equal to the mass and / or flow rate of the liquid or two-phase cooling fluid provided to the heat removal device 100 via the inlet.

[0079] A heat removal device 100 as disclosed herein can achieve a very high heat removal rate, thereby maintaining a corresponding heat-generating electronic device at or below a temperature threshold. In addition, a heat removal device 100 as described herein will properly function to remove heat when the heat removal device 100 is in both a horizontal and a vertical installation. It should be appreciated that although the heat removal device 100 is illustrated and described herein with respect to electronics of an HVAC system, such a heat removal device may be suitable to cool any heat-generating component.

[0080] Figures 12 and 13 show the results from the testing of two of the embodiments. Figure 12 shows the test data for an embodiment of the heat removal device 100, also referred to herein as Design- 1, when the heat removal surface 106 is oriented horizontally with two different refrigerants. Refrigerant- 1 is a low-pressure refrigerant and Refrigerant-2 is a medium pressure refrigerant. Enhancement in heat transfer coefficient is close to 10 times for both refrigerants at low heat fluxes. This is due to thin film evaporation. At high heat fluxes there is some improvement, but it is lower compared to low heat flux.This is due to vapor blanketing as more vapor is generated at high heat flux. Test data shows that for a plain surface, heat transfer coefficient is lower for low pressure, however present embodiments show that the heat transfer coefficient is higher for low pressure refrigerant in the present embodiments. The lower vapor density of the low-pressure refrigerant is utilized to create thin film to activate thin film evaporation. Similarly, Design- 1 is suitable for high heat flux. The sudden drop in heat transfer coefficient at low heat flux in Design- 1 is due to liquid flooding the grooves 130. These test data show that presented embodiments can be optimized for a given application for certain heat flux.

[0081] Figure 13 shows the test data for embodiments when the heat removal surface 106 is oriented vertically, as shown in Figure 5, and further referred to herein as Design-2. Enhancement in heat transfer coefficient in Design-2 is as high as 10 times at a certain heat flux compared to a plain surface. The enhancement is due to thin film evaporation. Design-2 is suitable for an application with a heat flux of around 20000 W / m2. Beyond that heat flux, the heat transfer coefficient reduces as the vapor venting is not efficient.

[0082] Comparing Figure 12 and 13 it can be seen the enhanced heat transfer in horizontal orientation is lower than vertical orientation due to vapor blanketing. This can be overcome by making the incline grooves that would facilitate vapor flow due to buoyancy and hence activating thin film evaporation.

[0083] The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.

[0084] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and / or groups thereof.

[0085] While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.

Claims

What is claimed is:

1. A heat removal device operable to cool a heat-generating device, the heat removal device comprising: a housing having a hollow interior; a base thermally couplable to the heat-generating device and arranged within the hollow interior of the enclosure, the base including a cooling surface and the cooling surface being arranged at an incline; a plurality of fins protruding from the cooling surface; at least one first groove formed in the cooling surface; and a top cover positioned upwardly adjacent to the plurality of fins, the top cover having one or more perforations formed therein.

2. The heat removal device of claim 1 , wherein the base further comprises a contact surface, and a plurality of sidewalls arranged between the contact surface and the cooling surface, the plurality of sidewalls including a first end, a second end, a first lateral side, and a second lateral side, wherein a height of the first end is different than the height of the second end.

3. The heat removal device of claim 2, wherein the contact surface has a horizontal orientation.

4. The heat removal device of claim 2, wherein the contact surface has a vertical orientation.

5. The heat removal device of claims 1- 3, wherein the height of the base is constant between the first lateral side and the second lateral side.

6. The heat removal device of any of claims 2-5, wherein at least one of the plurality of fins includes a plurality of fin members separated by one or more cuts.

7. The heat removal device of claim 2-6, wherein the plurality of fins extends between the first end and the second end and the one or more cuts are arranged at an angle relative to a direction of flow across the cooling surface.

8. The heat removal device of claim 6 or claim 7, wherein at least one continuous cut extends across the base at an angle greater than 0 degrees and less then 90 degrees relative to the plurality of fins such that the plurality of fin members of adjacent fins of the plurality of fins are staggered along a direction of flow across the cooling surface.

9. The heat removal device of any of claims 5-7, further comprising at least one recess formed in the cooling surface, the at least one recess extending at a non-parallel angle to the at least one first groove.

10. The heat removal device of claim 9, wherein the at least one recess is oriented parallel to at least one of the first end and the second end.

11. The heat removal device of any of claims 9-10, wherein the at least one recess has a bottom recess surface, the bottom recess surface being parallel to the contact surface of the base.

12. The heat removal device of any of claims 9-11, wherein the at least one recess has a bottom groove surface, the bottom groove surface being parallel to the cooling surface of the base.

13. The heat removal device of any of claims 9-12, wherein at least one of the at least one first groove and the at least one recess is filled with a porous material.

14. The heat removal device of any of claims 9-13, wherein the at least one recess includes a plurality of recesses and a distance between adjacent recesses is non-uniform.

15. The heat removal device of any of claims 9-14, wherein the top cover further comprises a plurality of first perforations formed therein.

16. The heat removal device of claim 15, wherein the top cover further comprises at least one second perforation formed therein, the at least one second perforation having a different configuration than the plurality of first perforations.

17. The heat removal device of claim 16, wherein the at least one second perforation is vertically aligned with the at least one recess.

18. The heat removal device of any of the preceding claims, wherein at least one of the plurality of fins and the cooling surface has a roughened surface.

19. The heat removal device of any of the preceding claims, wherein at least one of the plurality of fins and the cooling surface has a metal porous spray coating.

20. The heat removal device of any of the preceding claims, wherein the base further comprises a plurality of base modules arranged in series relative to a direction of flow through the hollow interior of the enclosure.

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