EP3193124A1

EP3193124A1 - Heat exchangers

Info

Publication number: EP3193124A1
Application number: EP17150118.2A
Authority: EP
Inventors: Brian St. Rock; Andrzej E. Kuczek; Joseph Turney
Original assignee: Hamilton Sundstrand Corp
Current assignee: Hamilton Sundstrand Corp
Priority date: 2016-01-13
Filing date: 2017-01-03
Publication date: 2017-07-19
Also published as: US20170198979A1

Abstract

A heat exchanger (100) includes a body (101) made of polymer, a plurality of first flow channels (103) defined in the body (101), and a plurality of second flow channels (105) defined in the body (101). The second flow channels (105) fluidly isolated from the first flow channels (103). The first flow channels (103) and second flow channels (105) are arranged in a checkerboard pattern.

Description

BACKGROUND

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.

SUMMARY

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.

BRIEF DESCRIPTION OF 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 by way of example only in detail herein below with reference to certain figures, wherein:

Fig. 1A is a perspective view of an embodiment of a heat exchanger in accordance with this disclosure, showing a hot flow inlet/cold flow outlet of the heat exchanger;
Fig. 1B is a perspective cross-sectional view of the heat exchanger of Fig. 1A, showing a middle portion of the heat exchanger;
Fig. 1C is a perspective cross-sectional view of the heat exchanger of Fig. 1A, showing a hot flow outlet/cold flow inlet of the heat exchanger;
Fig. 1D is a scaled up view of a portion of the heat exchanger of Fig. 1A;
Fig. 2 is a cross-sectional view of an embodiment of a heat exchanger in accordance with this disclosure;
Fig. 3 is a cross-sectional view of an embodiment of a heat exchanger, illustrating a primary surface heat conduction and secondary surface heat conduction in a non-checkerboard pattern embodiment; and
Fig. 4 is a cross-sectional view of an embodiment of a heat exchanger in accordance with this disclosure, illustrating only primary surface heat conduction as there are no secondary surfaces.

DETAILED DESCRIPTION

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 Fig. 1A and is designated generally by reference character 100. Other embodiments and/or aspects of this disclosure are shown in Figs. 1B-4. The systems and methods described herein can be used to reduce weight and/or increase performance of heat transfer systems.
Referring to Fig. 1A, a heat exchanger 100 includes a body 101, a plurality of first flow channels, e.g., hot flow channels 103 as described herein, defined in the body 101, and a plurality of second flow channels, e.g., cold flow channels 105 defined in the body 101. While hot flow channels 103 and the cold flow channels 105 are described with respect to a relative temperature of flow therein, it is contemplated that the hot flow channels 103 can be used for cold flow and vice versa, or any other suitable arrangement.
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 counterflow 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 Fig. 1D, the four parameters are shown. As shown, the full width A and height B are always greater than zero. The secondary width C and height D can be zero up to the full width and height. If C>0 and D>0, the shape is an octagon, if C>0 and D=0 (or C=0 and D>0), the shape is a hexagon, and if C=0 and D=0, the shape is a rhombus.
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 Fig. 2, a heat exchanger 200 can include elliptical flow channels 203 and/or non-elliptical flow channels 205 (e.g., rounded cross shaped) defined in body 201.
As shown in Figs. 1A, 1B, and 1C, one or more flow channels 103, 105 can include changing characteristics. The changing characteristics can include a changing flow area. For example, the changing flow area can increase a hot flow area toward a hot flow outlet of the heat exchanger 100 (e.g., as shown in transitioning from Fig. 1A, through Fig. 1B, to Fig. 1C). Similarly, the changing flow area can decrease a cold flow area toward the hot flow outlet as the hot flow area increases (which may be a function of the increasing hot flow area in order to maintain total area of the body 101). It is contemplated that one or more of the hot flow channels 103 or the cold flow channels 105 may maintain a constant flow area or change in any other suitable manner.
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 Figs. 1A and 1B) which transitions to a second polygonal flow area having more sides at a hot flow outlet (e.g., a hexagon as shown in Fig. 3). Also as shown, the changing flow area shape can include a first polygonal flow area at a cold flow inlet (e.g., a rhombus as shown in Figs. 1C and 1B) which transitions to a second polygonal flow area having more sides at a cold flow outlet (e.g., a hexagon as shown in Fig. 1A). Any other suitable changing shape along a length of the body 101 is contemplated herein (e.g., any desired change of A, B, C, and/or D as shown in Fig. 1D).
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 Fig. 3, an embodiment of a body 301 is shown having a non-checkered scheme (e.g., a planar alignment scheme as is typical in plate-fin heat exchangers). As can be seen, primary heat conduction path (a) flows across the thickness of only two walls from hot channels 303 to cold channels 305. Secondary heat conduction path (b) travels a much longer path through the material of body 301, which causes an efficiency loss. However, referring to Fig. 4, the hot and cold flow channels 103, 105 can include a suitable shape (e.g., a rhombus shape as shown) such that all surfaces form primary heat transfer surfaces wherein each surface includes a hot side defining a portion of a hot flow channel 103 and a cold side defining a portion of a cold flow channel 105. It is contemplated that other shapes (e.g., as described above) can be used with a polymer body 101, however, the minimizing secondary heat transfer surfaces can improve the thermal efficiency.
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 scope of the subject disclosure.

Claims

A heat exchanger (100), comprising:
a body (101) made of polymer;

a plurality of first flow channels (103) defined in the body (101); and

a plurality of second flow channels (105) defined in the body (101), the second flow channels (105) fluidly isolated from the first flow channels (103), wherein the first flow channels (103) and second flow channels (105) are arranged in a checkerboard pattern.
The heat exchanger of claim 1, wherein the first and/or second flow channels can include a changing flow area along a length of the body.
The heat exchanger of claim 2, wherein the changing flow area increases a first flow area toward a first flow outlet of the heat exchanger.
The heat exchanger of claim 3, wherein the changing flow area decreases a second flow area toward the first flow outlet as the first flow area increases.
The heat exchanger of claim 2, wherein the first and/or second flow channels include a changing flow area shape.
The heat exchanger of claim 5, wherein the changing flow area shape includes 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 heat exchanger of claim 5, wherein the changing flow area shape includes 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 heat exchanger of claim 1, wherein the hot and second flow channels 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.
The heat exchanger of claim 1, wherein the first and/or second flow channels include at least one of a hexagonal shape or an octagonal shape.
The heat exchanger of claim 1, wherein the first and/or second flow channels include a rectilinear shape.
The heat exchanger of claim 1, wherein the first and/or second flow channels include a polygonal shape.
A method for manufacturing a heat exchanger, comprising;
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.
The method of claim 12, wherein forming the heat exchanger includes additively manufacturing the heat exchanger.