Patent Publication Number: US-2022236021-A1

Title: Self-regulating heat exchanger

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. patent application Ser. No. 16/786,704, filed Feb. 10, 2020, which is a divisional application of U.S. patent application Ser. No. 14/598,607 filed on Jan. 16, 2015, the entire contents of these applications being incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to heat exchangers, more specifically to plate fin heat exchangers. 
     2. Description of Related Art 
     Plate fin heat exchangers include plates that define flow channels for a first fluid to flow therethrough. A fin layer can be disposed in thermal communication with each plate and allow a second fluid to flow through the fin layer to thereby draw heat from the fins, ultimately cooling the first fluid in the plate. Traditional plate fin heat exchangers require the designer to balance pressure drop with thermal efficiency, the calculus of which changes with changing operational temperatures. However, traditional heat exchangers have no means by which to adjust pressure drop or thermal efficiency responsive to changing operational temperatures. 
     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 exchanger systems. The present disclosure provides a solution for this need. 
     SUMMARY 
     A heat exchanger includes a flow channel operatively connecting a channel inlet to a channel outlet to channel fluid to flow therethrough. The flow channel is defined at least partially by a shape change material. The shape change material changes the shape of the flow channel based on the temperature of the shape change material. The shape change material can include a shape-memory alloy, for example. The shape-memory alloy can include at least one of a nickel-titanium alloy (NiTi), Cu—Al—(X), Cu—Sn, Cu—Zn—(X), In—Ti, Ni—Al, Fe—Pt, Mn—Cu, or Fe—Mn—Si. 
     The heat exchanger can further include a plate defining a second flow channel operatively connecting a second channel inlet to a second channel outlet to channel a second fluid to flow therethrough, wherein the flow channel is mounted in thermal communication with the plate. The flow channel can be sandwiched between two plates. 
     The flow channel can be configured to have a first shape at a first temperature and a second shape at a second temperature higher than the first temperature, wherein the second shape provides increased thermal efficiency compared to the first shape. 
     The flow channel can include an aligned fin shape in the first shape and the second shape can be defined by a step-wise shift of the aligned fin shape at segmented portions of the flow channel to provide increased thermal efficiency to regulate temperature of the heat exchanger. In certain embodiments, the first shape can be a tubular shape and the second shape can be a swirl shape. 
     The flow channel can be defined by a plurality of wires, at least one of which including the shape change material. In certain embodiments, the flow channel can be defined by a mesh of shape change wires. 
     In certain embodiments, the flow channel can be additively manufactured. For example, the flow channel can be formed using laser powder-bed fusion. 
     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 in detail herein below with reference to certain figures, wherein: 
         FIG. 1A  is a perspective view of an embodiment of a flow channel of a heat exchanger in accordance with this disclosure, showing the flow channel in a first shape; 
         FIG. 1B  is a perspective view of the flow channel of  FIG. 1A , showing the flow channel in a second shape; 
         FIG. 1C  is a perspective view of an embodiment of a plate fin heat exchanger in accordance with this disclosure, showing the flow channel of  FIG. 1A  disposed thereon in the second shape; 
         FIG. 2A  is a schematic cross-sectional view of an embodiment of a flow channel of a heat exchanger in accordance with this disclosure, showing the flow channel in a first shape; 
         FIG. 2B  is a cross-sectional view of the flow channel of  FIG. 2A , showing the flow channel in a second shape; 
         FIG. 3A  is a perspective view of an embodiment of a cylindrical flow channel of a heat exchanger in accordance with this disclosure, showing the flow channel in a first shape; 
         FIG. 3B  is a cross-sectional view of the flow channel of  FIG. 3A , showing the flow channel in a second shape; 
         FIG. 4A  is a cross-sectional view of an embodiment of a flow channel of a heat exchanger in accordance with this disclosure, showing the flow channel in a first shape defined by a plurality of wires; 
         FIG. 4B  is a cross-sectional view of a wire of the flow channel of  FIG. 4A , showing the wire in a first shape; and 
         FIG. 4C  is a cross-sectional view of  FIG. 4B , showing the wire in a second shape. 
     
    
    
     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 flow channel 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-4C . The systems and methods described herein can be used to optimize thermal efficiency of a heat exchanger. 
     Referring generally to  FIGS. 1A-1C , a heat exchanger (e.g., plate fin heat exchanger  150  shown in  FIG. 1C ) includes a flow channel  100  for a fluid to flow therethrough and defined at least partially by a shape change material. The shape change material changes a shape of the flow channel  100  based on a temperature of the shape change material. The shape change material can include a shape-memory alloy. The shape-memory alloy can include at least one of a nickel-titanium alloy (NiTi), Cu—Al—(X), Cu—Sn, Cu—Zn—(X), In—Ti, Ni—Al, Fe—Pt, Mn—Cu, Fe—Mn—Si, or any other suitable shape-memory material. 
     The heat exchanger  150  can further include one or more plates  151  defining a second flow channel for a second fluid to flow therethrough. As shown in  FIG. 1C , the flow channel  100  can be mounted in thermal communication with plates  151  and/or sandwiched between two plates  151 . Any other suitable number of plates and/or channels can be used. 
     The flow channel  100  can include a first shape at a first temperature and a second shape at a second temperature higher than the first temperature. It is contemplated that the second shape provides increased thermal efficiency compared to the first shape, e.g., by increasing the effective surface area in the flow channel  100 . However, those skilled in the art will readily appreciate that this can also be used in reverse, e.g., using a more thermally efficient shape for lower temperatures if needed for a given application. 
     As shown in  FIG. 1A  the first shape can include an aligned fin shape  103  in a flow-wise direction (e.g., forming step-like rectangular passages). Referring to  FIG. 1B , the second shape can be defined by a step-wise shift of the aligned fin shape at segmented portions  101  thereof to provide increased thermal efficiency to regulate temperature of the heat exchanger  150 . It is contemplated that the reverse order of shapes can be utilized. 
     As shown, in the first shape, the segmented portions  101  are aligned, forming smooth rectangular channels. In the second shape, the segmented portions  101  are misaligned in the flow-wise direction, which increases the pressure drop across the flow channels  100  but increases thermal efficiency. 
     Referring to  FIGS. 2A and 2B , a flow channel  200  can include fins  201  configured to change in cross-sectional shape made at least partially of a shape change material as described above. For example, one or more of the segmented portions  101  of flow channel  100  can include a cross-sectionally shape changing fins  201 . It is also contemplated that fins  201  can be continuous flow channels without segmented portions  101 . 
     As shown in  FIG. 2A , the fins  201  of flow channel  200  can include a first cross-sectional shape with bent sides. Referring to  FIG. 2B , when temperature increases, the sides of fins  201  can straighten, increasing cross-sectional area within the sides. It is also contemplated that the first cross-sectional shape can include straight sides of fins  201  and the second cross-sectional shape can include bent sides of fins  201 . 
     Referring to  FIG. 3A , in certain embodiments, a flow channel  300  is made at least partially of a shape change material as described above and can include a first cross-sectional shape defining a tubular shape. Referring to  FIG. 3B , the second cross-sectional shape of flow channel  300  can include a swirl shape (e.g., a helical shape) at the second temperature. The swirl shape can create flow turbulence and increase the total surface area for a more efficient heat transfer coefficient without significant increase in pressure drop. 
     Referring to  FIG. 4A , a flow channel  400  can be defined by a plurality of wires  401 , at least one of which including the shape change material as described above. In certain embodiments, the flow channel  400  can be defined by a mesh of shape change wires  401 . As shown in  FIG. 4B , one or more of the wires  401  can have a first shape (e.g., a step-like rectangular shape) and can change to as second shape (e.g., a partially bent portion) at the second temperature. 
     It is envisioned that the shape change material can be selected to allow for the process of changing shape to be reversible when the heat exchanger is cooled. It is also contemplated that the shape change material can be selected to make the process of changing shape can be irreversible. 
     In certain embodiments, the flow channels  100 ,  200 ,  300 ,  400  as described herein can be additively manufactured. For example, the flow channel  100 ,  200 ,  200 ,  400  can be formed using laser powder-bed fusion. Any other suitable method of manufacturing is contemplated herein. 
     The above described systems and methods allow for a self-adjusting heat exchanger with an optimized Nusselt number. The Nusselt number characterizes the ratio of convective to conductive heat transfer across a surface. A high Nusselt number is indicative of efficient transfer of heat from a core structure to a coolant. Also, the above described systems and methods allow for the pumping power needed to drive the coolant through the structure to be modified with shape change. 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for heat exchangers with superior properties including self-regulating flow channels. 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.