This disclosure relates generally to heat exchangers and, more particularly, to methods and apparatus to generate oscillating fluid flows in heat exchangers.
Heat exchange devices such as channel fin arrays are used in many known applications for convectional heat transfer. In particular, an array may be used to increase an amount of surface area in contact with fluid moving through an array, thereby more efficiently transferring heat between the fluid and the array. In some typical examples, an array of fins may be used to transfer heat between a first flowing fluid to a second flowing fluid that is moving in a different direction from the first flowing fluid (e.g., a countercurrent heat exchanger, etc.).
A fin array may have a performance tradeoff among pressure drop, heat flux, and turbulence related to mixing fluid flow moving therethrough. Because these factors may affect thermal performance significantly, parameters such as fin array patterning, pressure drop, fin geometry, and/or spacing are often determined in an ad hoc empirical manner (e.g., trial and error, experimental data and/or use of data tables) to provide a desired or required convectional heat transfer rate (e.g., above a threshold heat flux value). For example, determining parameters including, but not limited to, pressure drop, fin array geometry, and/or spacing of the fin array pattern can be used to ensure a sufficient convectional (i.e., convective) heat transfer rate. As a result, such relatively specific heat exchanger designs may require significant experimentation, adjustment, and/or design efforts to attain the desired or required convectional rate.
An example fluid flow apparatus includes a repeating pattern of fins arranged in rows, where fins of each row are separated from one another by channels, where the fins have respective sub-channels extending therethrough to facilitate oscillation of fluid moving through the channels, and where each of the sub-channels defines a sub-channel inlet and a sub-channel outlet of a respective fin of the pattern.
Another example fluid flow apparatus includes a pattern of fins that extend parallel to one another and arranged along a width of a fluid flow channel, and where each of the fins has a leading edge. The example apparatus also includes a pattern of sweep jets arranged upstream of the leading edges of the fins to generate an oscillatory fluid flow through the fins, where the sweep jets are spaced apart from one another along the width of the fluid flow channel.
Another example fluid flow apparatus includes a pattern of fins arranged in rows, where each of the fins extends along a longitudinal direction, and where each fin of the fins includes an incurvate surface on a downstream side of the fin to generate an oscillatory fluid flow that moves past the fins.
An example method for assembling a fluid flow apparatus includes coupling a tessellated pattern of fins in staggered rows, where the fins are identical in shape to one another and oriented along a same direction, where a fin of the pattern of fins with at least one incurvate surface is to generate an oscillating fluid flow relative to the fin when fluid flows across the fin.
An example method for operating a fluid flow apparatus, which includes a substrate and fins, includes directing a fluid towards the fins, where the fins include a sub-channel, and transferring heat between the fins and the fluid as the fluid flows into the sub-channel to define an oscillating fluid flow that increases surface wetting between the fins and the fluid.
An example apparatus includes means for generating a recirculating fluid flow across a tessellated pattern of fins arranged in rows, where the means for generating the recirculating flow has flow direction oscillation means.
The figures are not to scale. Instead, to clarify multiple layers and regions, the thickness of the layers may be enlarged in the drawings. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used in this patent, stating that any part is in any way positioned on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, means that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. Stating that any part is in contact with another part means that there is no intermediate part between the two parts.
Methods and apparatus to generate oscillating fluid flows are disclosed herein. The examples disclosed herein do not generally require precise determinations of these parameters because of their relatively high thermal efficiency. Further, the examples disclosed herein are greatly adjustable (e.g., adjustable heat flux) and, thus, a single design may be adaptable to a wide variety of applications without significant redesign, for example.
To improve thermal efficiency such that an increased amount of heat is transferred per unit volume of mass flowing, the examples disclosed herein generate oscillating fluid flows through a fin array (e.g., a microchannel fin array, a macro scale fin array, etc.), thereby generating an instability of the fluid flows to effectively increase an amount of convective heat transfer due to increased surface wetting. The examples disclosed herein generate the oscillations without moving parts (e.g., moving flaps, actuators, etc.). In particular, the examples disclosed herein utilize tessellation patterns and/or arcuate curves, for example, to generate oscillations in the fluid flows, thereby increasing a heat flux through the fin array.
In some examples, sub-channels disposed in fins are used to generate the oscillating fluid flows. In such examples, the fins are provided with the sub-channels to facilitate an oscillating motion of fluid moving past rows of the fins, thereby increasing a heat transfer rate of the fluid. In some examples, a pattern (e.g., a row, an array, etc.) of sweep jets are used to enable oscillating motions on a fin array. In some examples, a pattern of fins with incurvate cuts and/or surfaces may be used to effectively generate an oscillating fluid flow.
As used herein, the terms “fin” or “fins” may refer to heat sinks, heat exchange surfaces, heat transfer surfaces, protrusions, indentations, and/or curves, etc. that may be used to increase a surface area of material in contact with a flowing fluid. While some of the examples disclosed herein are shown in microchannels and/or a microchannel scale (e.g., smaller than or on the order of a millimeter), the examples disclosed herein may be applied to any appropriate scale (e.g., on the order of several centimeters (cm), meters, several feet, etc.). As used herein, the terms “heat exchanger” or “heat exchanger fins” may refer to a heat exchanger with countercurrent and/or cross flows, or a cooling device operatively coupled to a heat generating device, for example.
While the examples disclosed herein are generally directed towards using a fluid to remove heat from a component and/or crossflowing fluid, the examples disclosed herein may be used to provide heat to the component and/or the crossflowing fluid (e.g., utilizing the fluid to provide heat via fins). While the examples shown are generally shown along two dimensions for clarity, any of the examples disclosed herein may be applied to three-dimensional structures (e.g., channels that at least partially extend along directions into the views shown).
To facilitate heat transfer between a fluid and the substrate 102 and/or a component coupled to the substrate 102, the fluid of the illustrated example flows into the inlet 108 in a direction generally indicated by an arrow 112. The fluid then flows past the fins 106, thereby removing heat from the fins 106 that has been generated by the substrate 102. As will be discussed in greater detail below in connection with
In this example, the oscillating fluid flow system 100 has a characteristic dimension 116 defined by a distance between the opening 108 and the opening 110, which is denoted by “X.” In this example, the characteristic dimension 116 is approximately 10-20 cm. However, any appropriate dimension(s) and/or relative dimensional scale(s) may be used to suit the needs of a particular application and/or desired use.
The fins 106 of the illustrated example have oblong ellipsoid shapes. In particular, each of the fins 106 includes a trailing edge (e.g., a trailing edge portion, a trailing edge side) 204 and a leading edge (e.g., a leading edge portion) 206, both of which are labeled in relation to a direction of fluid flow in this example. However, in some examples, the trailing edge 204 and the leading edge 206 may be reversed (i.e., a reverse flow) while the fins 106 still facilitate generation of an oscillating flow of a fluid flowing therethrough.
To facilitate an oscillating fluid flow, each of the fins 106 of the illustrated example includes sub-channels (e.g., scallop cuts, incurvate cuts, etc.) 208. In this example, each of the sub-channels 208 defines an arcuate portion (e.g., an incurvate portion) 210 of the fin 106. As will be shown in greater detail below in connection with
Additionally or alternatively, any of the sub-channel inlets 212, the sub-channel outlets 214 and/or the sub-channels 208, in general, may be located proximate the leading edge 206. In some examples, the sub-channels 208 have a partial depth (e.g., the sub-channels 208 do not extend to the plate 104). Additionally or alternatively, the sub-channels 208 may have a varying depth (i.e., into the view of
Turning to
Turning to
Turning to
To define an oscillating fluid flow past the fins 404, a first portion of a fluid flow 406 moves between adjacent sweep jets 402 while a second portion of the fluid flow 407 moves into the sweep jets 402. The second portion 407 that flows into the sweep jets 402 emerges from the respective sweep jets 402 as an oscillating fluid flow (up and down along the view of
In some examples, multiple rows of the sweep jets 402 are disposed relative to the leading edges of the fins 404. For example, a repeating pattern of the sweep jets 402 and the fins 404 (e.g., a repeating pattern of one row of the sweep jets 402 followed by a row of the fins 404) may extend along a direction of the fluid flow 406. In some examples, a pitch of the sweep jets 402 may vary from row to row. Additionally or alternatively, a pitch of the fins 404 may vary from row to row.
To generate an oscillatory motion of a fluid flow moving past the fins 502, the fins 502 include first arcuate surfaces (e.g., an incurvate surface, a scallop cut, an indentation, etc.) 504 as well as second arcuate surfaces 508 in a generally opposing relationship to the arcuate surfaces 504. In particular, the combination of the first and second arcuate surfaces 504, 508 as well as the aforementioned row offset defines a recirculating fluid flow path that produces a fluid flow oscillation. The second arcuate surfaces 508 of the illustrated example define a converging tip 509 at a leading edge of the respective fin 502. Further, the first arcuate surfaces 504 define generally converging (i.e., converging along a general direction of fluid flow) opposing surfaces 511.
As can be seen in the illustrated example of
The oscillator pattern 600 of the illustrated example may be implemented proximate the inlet 108 of the fluid flow apparatus 100 to mix fluid flow prior to the fluid moving past the fins 106, for example. In other words, the oscillator pattern 600 may be utilized after the inlet 108, but prior to the fins 106. Additionally or alternatively, the oscillator pattern 600 is implemented within (e.g., embedded within) an array of fins (e.g., the fins 106 of the fluid flow apparatus 100) to mix fluid, thereby increasing an amount of surface interaction between the fluid and heat transfer surfaces.
In this example, a tessellated pattern of fins, such as the fins 106 (shown in
According to the illustrated example, next or simultaneously (e.g., contemporaneously) with block 802, an arcuate cutout, such as the arcuate surfaces 504, 508 of
In some examples, an arrangement of flow sweepers, such as the flow sweepers 402 of
In some examples, the fins 106 and/or the fin pattern array 111 are assembled to a component and/or a heat exchanger, such as the fluid flow apparatus 100 that may be operating as a heat exchanger (block 806). For example, the aforementioned fins 106 may be coupled via a bonding and/or welding process after the arcuate cutout and/or channel has been defined in/provided to the fins 106.
It is then determined whether the process is to be repeated (block 808). For example, this determination may include determining whether additional fin pattern arrays (e.g., the fin pattern array 111) are to be produced. If the process is to be repeated (block 808), control of the process returns to block 802. Otherwise, the process ends (block 810).
A fluid is directed towards a tessellated pattern of fins such as the fin pattern array 111 (block 902). In this example, the fins 106 of the fin pattern array 111 are generally oblong and extend along a direction of fluid flow. In this example, the fins 106 include the sub-channels 208, as described above in connection with
According to the illustrated example, heat is transferred between the fins and the fluid as the fluid flows into the sub-channels 208 to define an oscillating flow that increases surfaces wetting between the fins 106 and the fluid (block 904)
In some examples, the sweep jets 402 are operated upstream of the fins (block 906). In particular, the sweep jets 402 are arranged/positioned along a row that is upstream of leading edges of the fins 106 when the fins 106 are placed into a fluid flow. In particular, an array (e.g., row(s)) of the sweep jets 402 is placed in front of the leading edges to generate an oscillatory fluid flow past the fins 106 while a portion of the fluid flows around and past the sweep jets 402.
The process then ends (block 908).
From the foregoing, it will be appreciated that the above disclosed methods, apparatus and articles of manufacture enable oscillating fluid flows to increase heat transfer effectiveness and/or efficiency of fins (e.g., watts transferred per volume of material used in cooling) without moving parts. For example, heat transfer through fins is enhanced due to increased local mixing and/or surface wetting.
Although certain example methods, apparatus and articles of manufacture have been disclosed herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent. While the examples disclosed herein are shown as having microchannel scales, any appropriate cooling/heating application on any appropriate scale may implement the examples disclosed herein.