Patent Description:
A pin as defined in the preamble of claim <NUM> is illustrated in <CIT>.

Heat exchangers are used in many fields and exist in many forms. Typically, heat exchangers involve the transfer of heat between a first and a second fluid flowing in adjacent channels or layers of the heat exchanger. Many heat exchanger designs have a flowpath defined between an inlet of the heat exchanger and an outlet of the heat exchanger, and between fluid flow layers separated by plates that extend between the inlet and outlet. Heat exchange to or from a fluid flowing in the flowpath occurs primarily through the plates. It is known to provide pins or fins that extend in the flowpath, between the plates, to improve the heat transfer and create turbulence in the fluid flow. Various pin or fin shapes are known including triangular or rectangular cross-sectional shapes.

Such conventional heat exchangers have generally been considered satisfactory for their intended purpose but there is a need in the art for improved heat exchangers.

According to a first aspect, there is provided a pin for a core layer of a heat exchanger, as defined by claim <NUM>.

Also provided is layer for a heat exchanger, the layer comprising: an inlet; an outlet; an upper sheet; a lower sheet; a fluid flowpath defined between the upper sheet and lower sheet and from the inlet to the outlet; and at least one pin disposed in the flowpath and connecting the upper sheet to the lower sheet; wherein the pin has a first pin end and a second pin end and an outer surface between the first and second pin ends, wherein the pin includes a plurality of surface features protruding from the outer surface.

Defining a fluid flowpath between upper and lower sheets where the fluid flows past pins formed with such surface indentations such as recesses or dimples (can also be defined as a `negative bubble') in its outer surface greatly increases the turbulence of the fluid flow in the flowpath. By increasing the turbulence of the fluid flow, the heat transfer of the heat exchanger layer is increased. Furthermore, the indentations on the pins result in the pins having an increased primary heat transfer area compared to conventional/smooth pins.

The layer may comprise a plurality of such pins disposed in the flowpath, each pin connecting between the upper sheet and lower sheet and having a pin height defined between the upper and lower sheet.

At least one of the upper sheet and the lower sheet may be formed from an aluminium alloy, a titanium alloy, an austenitic nickel-chromium-based superalloy, stainless steel or copper.

According to another aspect, there is provided a heat exchanger comprising a first layer and a second layer; wherein the first layer is a layer according to the preceding aspect; wherein the second layer is a layer according to the preceding aspect; and wherein the upper sheet of the second layer is also the lower sheet of the first layer.

The average distance between the upper and lower sheets of the first layer may be different from the average distance between the upper and lower sheets of the second layer. Put another way, the first layer may have a different average height from the second layer. The number of pins disposed in the flowpath of the first layer may be different from the number of pins disposed in the flowpath of the second layer.

A pin pattern of the pin(s) disposed in the flowpath of the first layer may be different from a pin pattern of the pin(s) disposed in the flowpath of the second layer.

According to another aspect, there is provided a method of manufacturing a layer for a heat exchanger, the method comprising: forming a lower sheet; additively manufacturing at least one pin on the lower sheet, the pin having a first pin end and a second pin end and an outer surface between the first and second pin end and further having surface indentations formed in the outer surface; and providing an upper sheet on top of the pin.

Using additive manufacturing allows pins to be created having the surface indentations in their outer surface. The method may comprise additively manufacturing a plurality of pins on the lower sheet.

The method may comprise providing a sidewall extending between the lower sheet and the upper sheet; and optionally additively manufacturing one or more sets of turning vanes on the lower sheet at the same time as additively manufacturing the or each pin.

Additively manufacturing the sidewall may be simpler than using traditional manufacturing techniques. Turning vanes may be desirable in layers having a non-straight flow path, e.g. a U-shaped flow path, and additively manufacturing these may be simpler than using traditional (non-additive) manufacturing techniques.

In an example, the sheets may also be manufactured using additive manufacture.

Each step of additive manufacturing may be performed using a metal powder bed SLM additive manufacturing process, or other AM methods.

A powder of the metal powder bed may be one of an aluminium alloy, a titanium alloy, and an austenitic nickel-chromium-based superalloy.

SLM is a relatively mature additive-manufacturing technology and typically allows recovery of unused (i.e. unmelted) powder from the finished article. The unused powder may be used in future additive-manufacturing operations and thus this method may be cost effective by minimizing wastage of (potentially expensive) metal powder.

The heat exchanger constructed in accordance with this aspect may have a compact design allowing for good heat exchange between fluids flowing in their respective pluralities of layers.

Certain embodiments of the present disclosure will now be described in greater detail by way of example only and with reference to the accompanying drawings in which:.

<FIG> shows a heat exchanger <NUM> having a heat exchanger core <NUM>, a first header <NUM> for conveying a first fluid e.g. oil into and out of the core <NUM>, and a second header <NUM> for conveying a second fluid e.g. oil into and out of the core <NUM>. The heat exchanger may be primarily used to exchange heat between the first fluid and the second fluid. However, heat may also be exchanged out through the sidewall <NUM> as well as out of the top and bottom sides of the heat exchanger core <NUM>. The first and second fluids may be oil - in an oil-oil cooler (OOC), but other fluids, including water or air may also be used.

The first header <NUM> connects to a first plurality of layers <NUM> of the heat exchanger core <NUM>. The second header <NUM> connects to a second plurality of layers <NUM> of the heat exchanger core <NUM>. The first plurality of layers <NUM> is interleaved with the second plurality of layers <NUM> so that the first fluid flows through every second layer and the second fluid flows through the layers in-between the first fluid layers, providing alternate layers of first fluid flow and second fluid flow. The individual layers are typically rotated <NUM> degrees relative to each other. At least within the heat exchanger <NUM>, the first fluid flowing in the first plurality of layers <NUM> is fluidly isolated from the second fluid flowing in the second plurality of layers by the sheets separating the layers. <FIG> shows one core layer. Any layer of the first and second pluralities of layers may be a layer <NUM> as shown in <FIG>.

As shown in <FIG>, the layer <NUM> comprises an inlet <NUM> and an outlet <NUM>, a sidewall <NUM>, and (not shown in <FIG>) an upper sheet, and a lower sheet <NUM>. In use, fluid is constrained by the upper sheet, lower sheet <NUM>, and sidewall <NUM>, so as to flow from the inlet <NUM>, through the layer <NUM>, to the outlet <NUM>. That is, the upper sheet, lower sheet <NUM>, and sidewall <NUM> together define a flowpath for fluid flowing in the layer <NUM>. The layer <NUM> shown in <FIG> defines a generally U-shaped flowpath between the inlet <NUM> and outlet <NUM>, with the inward flow separated from the outward flow by a separation bar <NUM>. The upper sheet (not shown) of a given layer, may simultaneously function as the lower sheet <NUM> of layer (e.g. layer <NUM>) immediately above.

With reference to <FIG>, a first portion of the first header <NUM> connects to the inlet side <NUM> of each layer <NUM> of the first plurality of layers, and, in use, fluid is pumped into the first portion and flows into the inlet side <NUM> of every layer connected to the first header <NUM>. The fluid flows through each of the layers <NUM> and out through the outlet <NUM> of each layer of the first plurality of layers. The outlets <NUM> are all connected to a second portion of the first header <NUM>, the second portion being fluidly isolated from the first portion. Fluid flows into the second portion and then out of the first header <NUM>.

Similarly, a first portion of the second header <NUM> connects to the inlet side <NUM> of each layer <NUM> and, in use, fluid is pumped into the first portion and flows into the inlet side <NUM> of every layer connected to the second header <NUM>. The fluid flows through each of the layers 31and out through the outlet <NUM> of each layer. The outlets <NUM> are all connected to the second portion of the second header <NUM>, the second portion being fluidly isolated from the first portion. Fluid flows into the second portion and then out of the second header <NUM>.

Within each layer <NUM>, as shown in <FIG>, one or more pins <NUM> are disposed in the fluid flowpath. Each pin <NUM> extends between the lower sheet <NUM> and the upper sheet (not shown in <FIG>).

Additionally, there may be provided within each layer <NUM> a first set of turning vanes 200a that may turn the flow through <NUM> degrees, and a second set of turning vanes 200b that may turn the flow through a further <NUM> degrees, to create the overall U-shaped flow path. A plurality of pins 100b may be disposed between the first and second sets of turning vanes 200a, b. The pins <NUM> shown in <FIG> are all arranged within the layer <NUM> such that each pin <NUM> faces directly into a local flow direction.

<FIG> shows the shape of the pins <NUM>, 100b in more detail. In the direction from the lower sheet to the upper sheet or vice versa, the pins have pin body <NUM> extending between a first end <NUM> and a second end <NUM>. The cross section of the pin <NUM>, in the plane across the ends <NUM>, <NUM> may take a variety of shapes e.g. triangular, rectangular, teardrop shaped. , oval, circular, etc. The ability to manufacture the pins using additive manufacturing means that there is much more flexibility in the shapes that can be produced. The cross-section in the example shown is a teardrop or rounded triangle shape such that the width of the pin tapers in the direction of fluid flow.

<FIG> shows the shape of a pin <NUM> of a pin according to the disclosure. The pin has a leading edge <NUM> facing the fluid flow towards the pin, and a trailing edge <NUM>, a first end <NUM> and a second end <NUM>. The cross-sectional shape of the pin of this example is shown as a teardrop or rounded triangle shape such that the width of the pin tapers from the leading edge <NUM> to the trailing edge <NUM>. This is just one example, and the pin can have other cross-sections.

The body of the pin has an outer surface <NUM> between the first and second ends. A plurality of surface indentations or depressions <NUM> such as dimples or 'negative bubbles' are provided on the outer surface <NUM> extending into the outer surface. These indentations create turbulence in the fluid flow thus leading to improved thermal exchange. The fluid is directed towards the pin <NUM> in a first direction. As it meets the pin at the leading edge <NUM> it is deflected as it flows around the pin in different directions due to the indentations. The indentations disturb the flow of the fluid causing a permanent disturbance of the velocity field, which results in intensive mixing of the fluid particles making the fluid more turbulent. This turbulence is magnified due to the plurality of pins in the layer. The increased turbulence increases the heat transfer coefficient and, thereby, the efficiency of the heat exchanger. Further, the indentations increase the surface area, and hence the heat transfer area, of the pin compared to conventional pins which have a smooth outer surface. By using indentations to create a non-smooth surface, rather than adding features, there is a saving in pin material and, therefore, associated cost, size and weight savings. This allows for a more compact heat exchanger.

In a heat exchanger core, as described above, several such layers will be provided, separated by the sheets. <FIG> shows just one such layer but the principle will be the same for each layer.

It is possible that the number of pins and/or the pattern in which the pins are arranged is the same for each layer, but it is also feasible that different layers have different numbers of pins and/or patterns of pins. The layers may also be the same height (defined between the sheets) or different layers may have different heights depending on the application.

Any or all parts of the heat exchanger <NUM> other than the pins may be made from metal. In some embodiments, some or all parts are made from an austenitic nickel-chromium-based superalloy, such as the Inconel family of metals manufactured by the Special Metals Corporation of New York state, USA. In other embodiments, some or all parts may be made from an aluminium alloy, a titanium alloy, stainless steel or copper.

Claim 1:
A pin for a core layer of a heat exchanger past which fluid flowing through the layer passes, the pin (<NUM>) having a first and a second end and an outer surface between the first and second ends, the pin being characterised by having a rounded triangular shape cross-section that tapers from an inlet side of the pin to an outlet side of the pin, and wherein a plurality of dimples are formed in the outer surface.