ADDITIVELY MANUFACTURED HEAT EXCHANGER LAYER

Abstract

A heat exchanger layer having an inlet side, IN, where a medium enters the layer and an outlet side, OUT, where the medium exits the layer, and a plurality of fins defining a plurality of flow channels for the medium from the inlet side to the outlet side. Each fin has a leading edge adjacent the inlet side and a trailing edge adjacent the outlet side, and wherein the leading edge of a subset of the fins is thicker than the rest of the fin, and the leading edge of the fins intermediate the fins of the subset of fins is recessed with respect to the inlet side compared to the leading edge of the fins of the subset of fins.

Claims

1. A heat transfer layer of a heat exchanger, the layer comprising an inlet side, IN, where a medium enters the layer; an outlet side, OUT, where the medium exits the layer; and a plurality of fins defining a plurality of flow channels for the medium from the inlet side to the outlet side, each fin having a leading edge adjacent the inlet side and a trailing edge adjacent the outlet side, and wherein the leading edge of a subset of the fins is thicker than the rest of the fin, and wherein the leading edge of the fins intermediate the fins of the subset of fins is recessed with respect to the inlet side compared to the leading edge of the fins of the subset of fins.

2. A heat transfer layer as claimed in claim 1, wherein the fluid flow channels include a relatively straight portion extending from the inlet side towards the outlet side and a relatively wavy portion between the relatively straight portion and the outlet side.

3. A heat transfer layer as claimed in claim 1, wherein the fluid flow channels define a wavy cross-section wherein the frequency of the wave increases from the inlet to the outlet.

4. A heat transfer layer as claimed in claim 1, wherein the subset of fins comprises every second fin.

5. A heat transfer layer as claimed in claim 1, wherein the leading edges of the fins of the subset of fins have a bulbous shape.

6. A heat transfer layer as claimed in claim 1, wherein the leading edges of the fins of the subset of fins have a teardrop shape.

7. A heat exchanger comprising: a plurality of cold layers through which a cold medium flows and a plurality of hot layers through which a hot medium flows, wherein the cold layers comprise a heat transfer layer as claimed in claim 1.

8. A heat exchanger as claimed in claim 7, wherein the leading edges of the fins are reinforced at the inlet side.

9. A heat exchanger as claimed in claim 7, wherein the plurality of cold layers are arranged relative to the plurality of hot layers such that the cold medium flows in a direction transverse to the direction of flow of the hot medium.

10. A heat exchanger as claimed in claim 7, wherein the plurality of cold layers are arranged relative to the plurality of hot layers such that the cold medium flows in a direction parallel to but opposite to the direction of flow of the hot medium.

11. A heat exchanger as claimed in claim 7, being a heat exchanger for a vehicle.

12. A heat exchanger as claimed in claim 11, being a heat exchanger for an aircraft.

13. A heat exchanger of claim 7, wherein the cold medium is RAM air.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Examples according to the disclosure will be described in more detail, with reference to the drawings. It should be noted that variations are possible within the scope of the invention as defined by the claims. The examples are described in the context of a heat exchanger for an aircraft or other vehicle using RAM air as the cooling fluid, but other fluids may be used and the design according to the disclosure may find other applications.

[0013] FIG. 1 is a cross section of a cooling medium (here RAM air, by way of example only) layer of a heat exchanger according to the disclosure.

[0014] FIG. 2 is a 3D view of a heat exchanger block with a cooling medium layer such as shown in FIG. 1

DETAILED DESCRIPTION

[0015] FIG. 1 shows a cross section of a layer 1 of a heat exchanger where fins 10, 11 extending across the layer from a first, inlet side IN to an opposite, outlet side OUT, define flow channels for the cooling medium. In this example, the cooling medium is RAM air, but other fluids may be used. In use, this would be one of several alternative layers of fins for the cooling air (as described further with reference to FIG. 2). Between the alternate cooling layers, a heat exchanger will have hot medium layers. This layers will form flow channels for the hot medium (e.g. bleed air). The hot medium channels may provide flow of the hot fluid parallel to, but in the opposite direction, to the cold air flow, or may provide a cross-flow of the hot fluid relative to the cold fluid flow (i.e. from left to right or right to left in FIG. 1). The present disclosure is concerned with the design of the fins of a hot fluid layer and the way in which this is incorporated into a heat exchanger block and the design of the other parts of the block can be varied as required.

[0016] The fins 10, 11 are formed by additive manufacture and a subset of the fins 10 are formed to have a thickened or widened inlet end portion (leading edge) 100. In the example shown, every second fin 10 is formed with such a thickened end 100 but this is just one example. In other examples, every third, every fourth etc. fin may have such a thickened end 100.

[0017] The fins 11 located intermediate the fins 10 of the subset with the thickened end 100 are recessed from the inlet end compared to the fins of the subset i.e. the inlet ends 111 of these intermediate fins do not extend all the way to the inlet side IN.

[0018] In one example, the thickened ends 100 have a teardrop or bulbous shape but other thickened shapes could also be used.

[0019] The thickened ends 100 provide a protective front to the layer with respect to the incoming cooling medium especially RAM air and therefore provide a thickened guard surface against hailstones and impact from other things.

[0020] In a preferred example, as shown, to optimally decrease the pressure drop of the incoming fluid (RAM air) the fluid channel define by the fins 10, 11 is relatively straight (portion 12) as seen by the inlet fluid. This straight portion provides lower heat exchange between the cold layer and the hot layer (not shown) close to the inlet side IN. This is where the RAM air is the coldest and so the thermal gradient is the largest. Providing a relatively straight inlet portion 12 should decrease thermal stress in high temperature applications.

[0021] To improve the heat exchange properties of the heat exchanger, the fins can be shaped such that as they progress from the inlet side IN to the outlet side OUT they become more wavy (portion 13) defining a more tortuous path for the fluid before it exits the layer. In one example, the frequency of the waves defined by the fins increases from the inlet side IN to the outlet side OUT. The greater turbulence in the medium at this higher frequency portion 13 provides greater heat exchange with the hot medium in the adjacent layer.

[0022] FIG. 2 shows a cold medium layer 1 as described above and as shown in FIG. 1 combined with further hot and cold layers in a heat exchanger block. The example shown is a cross-flow heat exchanger, with the hot medium flowing in channels 20 and the cold medium flowing in the channels 30 defined between adjacent fins 10, 11 of the cold medium layer 1.

[0023] In applications where protection against hail, high inlet pressure, any medium pollutants and the like is desired, additional guard properties can be achieved by also forming the leading edges 40 of the hot layers to be rounded where impact occurs at the inlet IN. This results in the inlet side IN that is presented to the incoming RAM air forming a grid of rounded bars 100, 40.

[0024] By using the possibilities provided by additive manufacturing to vary fin design, the heat exchanger layer and heat exchanger incorporating such a layer can effectively guard against hail damage using existing features of the heat exchanger and without having to add additional components or additional mass to provide such protection. Further, pressure drop can be reduced and thermal stresses reduced.

[0025] 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 present disclosure 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.