Patent Application
20170198979
1. Field
The present disclosure relates to heat exchangers, more specifically to more thermally efficient heat exchangers.
2. Description of Related Art
Conventional multi-layer sandwich cores are constructed out of flat sheet metal dividing plates, spacing bars, and two dimensional thin corrugated fins brazed together. The fabrication process is well established and relatively simple. However, the manufacturing simplicity has a negative impact on the performance and limits the ability to control thermal efficiency.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved heat exchangers. The present disclosure provides a solution for this need.
A heat exchanger includes a body made of polymer, a plurality of first flow channels defined in the body, and a plurality of second flow channels defined in the body. The second flow channels fluidly isolated from the first flow channels. The first flow channels and second flow channels are arranged in a checkerboard pattern.
The first and/or second flow channels can include a changing flow area along a length of the body. The changing flow area can increase a first flow area toward a first flow outlet of the heat exchanger. The changing flow area can decrease a second flow area toward the first flow outlet as the first flow area increases.
The first and/or second flow channels can include a changing flow area shape. The changing flow area shape can include a first polygonal flow area at a first flow inlet which transitions to a second polygonal flow area having more sides at a first flow outlet. The changing flow area shape can include a first polygonal flow area at a second flow inlet which transitions to a second polygonal flow area having more sides at a second flow outlet.
The hot and second flow channels can include a rhombus shape such that all surfaces form primary heat transfer surfaces wherein each surface includes a hot side defining a portion of a first flow channel and a cold side defining a portion of a second flow channel. In certain embodiments, the first and/or second flow channels can include at least one of a hexagonal shape or an octagonal shape. In certain embodiments, the first and/or second flow channels can include a rectilinear shape, a polygonal shape, or any other suitable shape.
In accordance with at least one aspect of this disclosure, A method for manufacturing a heat exchanger can include forming a body out of polymer to include a plurality of first flow channels and a plurality of second flow channels such that the second flow channels are fluidly isolated from the first flow channels, and such that the first flow channels and second flow channels are arranged in a checkerboard pattern. Forming the heat exchanger can include additively manufacturing the heat exchanger.
These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings.
So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a heat exchanger in accordance with the disclosure is shown in
Referring to
The cold flow channels 105 are fluidly isolated from the hot flow channels 103. At least one of the hot flow channels 103 or the cold flow channels 105 can include a changing characteristic along a length of the body 101. However, it is contemplated that the flow channels 103, 105 can have constant characteristics along the length of the body 101.
The hot flow channels 103 and the cold flow channels 105 can be utilized in a counter-flow arrangement such that cold flow and hot flow are routed through the heat exchanger 100 in opposing directions. Also, as shown, the hot flow channels 103 and the cold flow channels can be arranged such that hot and cold channels 103, 105 alternate (e.g., in a checkerboard pattern as shown).
The flow channel 103, 105 can include shapes such as one or more of rhombuses, hexagons, and octagons. However, while the flow channels 103, 105 are shown as polygons, the shapes need not be polygonal or rectilinear. As appreciated by those skilled in the art, polygonal shapes can be described using the four parameters as described below. In
Any other suitable flow area shapes for the hot flow channels 103 and/or the cold flow channels 105 are contemplated herein. For example, as shown in
As shown in
In certain embodiments, the changing characteristic of the hot and/or cold flow channels 103, 105 can include a changing flow area shape. In certain embodiments, the changing flow area shape can include a first polygonal flow area at a hot flow inlet (e.g., a rhombus as shown in
The body 101 can be made of metal and/or any other suitable material. For example, the body 101 can be made of a polymer (e.g., plastic) or other suitable insulator material. One having ordinary skill in the art would not endeavor to use polymer as most polymers are considered thermal insulators, and, thus, the use of polymer is counter-intuitive for heat exchanger material. However, due to a reduction and/or elimination of secondary surfaces (e.g., surfaces where heat must travel through more material than the thickness of the walls) as described below, polymer can be utilized, especially in thin-walled applications, because the conduction path through the polymer (e.g., plastic) is very short in certain embodiments of the disclosure.
For example, referring to
It is contemplated that the heat exchanger 100 can include any suitable header (not shown) configured to connect the hot flow channels 103 to a hot flow source (not shown) while isolating the hot flow channels 103 from the cold flow channels 105. The header may be formed monolithically with the body 101 of the heat exchanger 100 or otherwise suitably attached to cause the hot flow channels 103 to converge together and/or to cause the cold flow channels 105 to converge together.
In accordance with at least one aspect of this disclosure, a method for manufacturing a heat exchanger 100 includes forming a body 101 to include a plurality of hot flow channels 103 and a plurality of cold flow channels such that the cold flow channels 105 are fluidly isolated from the hot flow channels 103, and such that at least one of the hot flow channels 103 or the cold flow channels 105 have a changing characteristic along a length of the body 101. Forming the heat exchanger 100 can include additively manufacturing the heat exchanger 100 using any suitable method (e.g., powder bed fusion, electron beam melting, polymer deposition).
Embodiments of this disclosure can allow maximization of primary surface area for heat exchange while allowing flexibility to increase or decrease the ratio of hot side to cold side flow area. Being able to change the relative amount of flow area on each side of the heat exchanger is necessary to fully utilize the pressure drop available on each side. Embodiments as described above allow for enhanced control of flow therethrough, a reduction of pressure drop, control of thermal stresses, easier integration with a system, and reduced volume and weight. Unlike conventional multi-layer sandwich cores, embodiments as described above allow for channel size adjustment for better impedance match across the core.
Further, in additively manufactured embodiments, since the core (e.g., body 101) can be made out of a monolithic material, the material can be distributed to optimize heat exchange and minimize structural stresses, thus minimizing the weight. Bending stresses generated by high pressure difference between cold and hot side are greatly reduced by adjusting curvature of the walls and appropriately sized corner fillets. Such solution reduces weight, stress, and material usage since the material distribution can be optimized and since the material works in tension instead of bending.
As described above, the certain embodiments can be additively manufactured (e.g., printed) as one piece out of polymer. Polymer as a heat exchanger material can offer a significant weight and cost benefit, and the drawbacks of using polymer (e.g., due to low thermal conductivity) can be significantly reduced through improving the heat conduction path (e.g., via the checkerboard pattern/reduction of secondary heat transfer surfaces of flow channels 103, 105 as described above). Hence, the conductive resistance of certain embodiments, even though made out of polymer, has negligible effect on performance and allows dramatic weight and cost savings. The resistance through a primary surface made of polymer will generally be smaller than the convective resistance between the walls and fluids so that the thermal conductivity of the polymer has little impact on the overall performance of the heat exchanger.
The methods and systems of the present disclosure, as described above and shown in the drawings, provide for heat exchangers with superior properties including reduced weight and/or increased efficiency. While the apparatus and methods of the subject disclosure have been shown and described with reference to embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure.
