Heat exchanger

Abstract

The invention relates to a heat exchanger (10) for transferring heat from a first fluid to a second fluid, the heat exchanger comprising: a flow channel (20) for guiding the first fluid; a plurality of spaced-apart flow lines (30) for guiding the second fluid, the flow lines (30) extending through the flow channel (20) and forming, arranged side by side, a line bundle (40), wherein outer walls of the flow lines (30), together with channel walls (21, 22) of the flow channel (20), form a flow grid (50) for the first fluid, and wherein the line bundle (40) creates a blockage in the flow grid (50). In order to design the heat exchanger to be more efficient, according to the invention the blockage in the flow grid (50) has a spatially heterogeneous distribution.

Description

[0001] heat exchanger

[0002] The invention relates to a heat exchanger for transferring heat from a first fluid to a second fluid.

[0003] In heat exchangers, which can also be referred to as heat exchangers, flow lines, usually in the form of tubes or plate-shaped elements, run through a flow channel of a cooling medium transversely to its longitudinal extent for carrying a medium to be cooled, usually a high-temperature medium. Stacking the flow lines next to one another, in particular above and behind one another, creates a geometric blockage or reduction in the flow cross-section in the flow channel, for example in contrast to an undisturbed inflow area upstream of the heat exchanger. Due to the continuity of a flow, the flow of the fluid flowing in the flow channel between two of the flow lines inevitably has a higher velocity than the inflow velocity in the inflow cross-section of the heat exchanger. This greatly increased velocity leads to an increase in pressure losses.The typical geometric blockage for heat exchangers that use cool atmospheric air as a heat sink is in the range of 10 - 50% on the air side, depending on the application. The Mach number between the flow lines can increase by more than the degree of blockage. Furthermore, the increase factor increases with increasing inflow Mach numbers. Therefore, for example, the Mach number can experience an increase by a factor of more than 200% at an inflow Mach number of 0.3 and a blockage of 50%. In some cases, a local velocity of >50 m / s can be assumed. If a heat exchanger is arranged in the bypass flow of an aircraft engine, significantly higher flow velocities can occur, in the range of Mach 0.4 to Mach 0.5 or higher.

[0004] In order to counteract the high velocities and thus reduce the pressure losses between the flow lines, the flow in classical heat exchangers is highly decelerated upstream of the flow grid using high flow velocities.

[0005] Furthermore, the majority of today's heat exchangers consist of non-flow-optimized geometries, such as rectangular channels or round tubes. Both of these geometries lead to flow separation, which further increases losses.

[0006] Furthermore, the static temperature of the cooling air increases with decreasing Mach number, thereby reducing the available temperature potential for cooling.

[0007] EP 4 198 433 A1 discloses a heat exchanger for transferring heat from air in a bleed air system to or from the air of other cabin air-conducting systems. For this purpose, the heat exchanger comprises a plurality of flow lines with a profiled leading edge and a further, sheet-like extension in a flow channel conducting a cooling flow. The profiled leading edges of the flow lines together form a stepped inflow surface. Within the flow grid, corrugated sheets between the flow lines form smaller guide channels for guiding the cooling flow. The corrugated sheets are intended to generate turbulence and thus mixing in the flow for improved heat convection. The interlocking within this flow grid, which is formed by the channel walls of the flow channel, the corrugated sheets, and the flow lines, is evenly or homogeneously distributed within the flow grid in this heat exchanger.In other words, the heat exchanger exhibits homogeneous blocking. Due to this homogeneous blocking, high pressure drops occur, which are disadvantageous for certain flow Mach numbers, especially higher ones, and the temperature dissipation decreases.

[0008] The requirements for aviation heat exchangers with high flow Mach numbers are therefore drastically different from those of conventional heat exchangers. Therefore, a heat exchanger for an aircraft engine should exploit the advantages of high flow velocity on heat transfer, while simultaneously improving the pressure drop characteristics of current heat exchangers. Therefore, the object of the invention is to provide a heat exchanger that enables more efficient heat transfer, particularly at higher flow velocities. Furthermore, the object of the invention is to provide an aircraft engine in which heat transfer can take place more efficiently.

[0009] The object is achieved by a heat exchanger according to claim 1, by a heat exchanger according to claim 11 and by an aircraft engine according to claim 12.

[0010] A heat exchanger according to a first aspect of the invention for transferring heat from a first fluid to a second fluid has a flow channel for guiding the first fluid and a plurality of spaced-apart flow lines for guiding the second fluid, wherein the flow lines extend through the flow channel and, running alongside one another, form a line package, wherein outer walls of the flow lines together with channel walls of the flow channel form a flow grid for the first fluid, and wherein the line package forms a blockage in the flow grid.

[0011] The object is achieved by the heat exchanger according to the invention for transferring heat from a first fluid to a second fluid as claimed in claim 1 in that the blocking in the flow grid has a spatially heterogeneous distribution. Due to a spatially heterogeneous distribution of the blocking, the flow is guided spatially non-uniformly, so that an otherwise occurring flow blockage is advantageously eliminated, thereby improving heat transfer. Furthermore, such a heat exchanger can be operated at a higher flow velocity. Due to a higher flow velocity, the flow has higher Reynolds and thus Nusselt numbers, which is advantageous for the heat transfer coefficient and thus advantageously reduces the total surface area required for heat transport.A spatially heterogeneous distribution of blocking can be formed by flow lines that are heterogeneously distributed and / or run heterogeneously within the line package. The flow grid can in particular be heterogeneously formed within the line package. In this context, heterogeneously distributed can mean that distances between adjacent flow lines in the line package vary. In this context, heterogeneously distributed can mean that flow lines in the line package have a course with a kink or a bend. In this case, kinks or bends can be distributed in the flow grid, in particular distributed heterogeneously to one another. A spatially heterogeneous distribution of blocking can be formed by repeating, in particular identical, adjacent partial grid spaces of the flow grid, which are arranged offset from one another in at least one main spatial direction.To make conventional heat exchangers more cost-effective, repeating partial grid spaces are formed, for example, by a pipe stack with even spacing between the flow lines and / or by a repeated, identical arrangement of metal sheets. Flow blockages resulting from this can be advantageously avoided or reduced by offsetting the partial grid spaces, as bypass guides are created that prevent local pressure losses. The flow grid can have bypass guide channels. Bypass guide channels can be formed by one or more outer surfaces of the flow lines and / or by additional guide surfaces.By means of bypass guide channels, the flow can be guided around the flow lines with a change in direction. At least one bypass guide channel is provided that imposes a flow direction on its guided flow that differs from the flow direction prevailing in another bypass guide channel and / or in an adjacent flow grid area. The flow grid with the heterogeneous interlocking can be delimited by outer surfaces of external flow lines in the line package.

[0012] The heat exchanger can preferably be described by a cylindrical coordinate system or a Cartesian coordinate system. The flow grid can have a cuboid, cylindrical segment-shaped, or cylindrical shape. The channel walls of the flow channel can delimit the flow grid in a cuboid and / or cylindrical manner in the flow direction. Expressed even more generally, the heat exchanger can have a main direction along its main extent, wherein the main direction continuously follows a flow direction between an inflow surface and an outflow surface. The inflow and outflow surfaces are cross-sectional planes in the flow direction immediately upstream and downstream of the line package, respectively, wherein the cross-sectional planes have a normal in the direction of the main extent of the flow channel. An axial direction or longitudinal direction can run parallel to the main extent of the heat exchanger.

[0013] In an operating state, the first fluid in the flow channel may have an inflow Mach number of at least 0.2, preferably 0.25, particularly preferably 0.3. It may be a heat exchanger arrangement comprising the heat exchanger according to the invention and an additional diffuser arranged upstream of the flow channel and decelerating the flow in an operating state during cruising flight to no less than Mach 0.2, preferably no less than Mach 0.25, particularly preferably no less than Mach 0.3.

[0014] The flow lines can have internal lines, at least in their interior, which can be designed as tubes, preferably round tubes, triangular tubes, square tubes and / or rectangular tubes. The flow lines can preferably have a profile shape. A profile shape can be an aerodynamic profile. A profile shape can be a teardrop shape, which can in particular have a larger front cross-section which, starting from a front edge, initially has a large cross-sectional widening towards the rear and then merges into an elongated, tapered cross-sectional section up to a rear edge. It can be provided that the flow lines running alongside one another each form an angle of less than 30° to one another. Furthermore, the flow lines running alongside one another can extend from a first channel wall of the flow channel to a second channel wall of the flow channel opposite the first channel wall.Furthermore, it can be provided that the blocking is defined as the ratio of the blocked cross-sectional area to the total cross-sectional area. The part of the cross-sectional area that appears blocked can be impassable for the flow of the first fluid. The part of the cross-sectional area that appears blocked can be a geometric obstacle formed by the flow lines. The blocking can be formed by the outer walls of the flow lines.

[0015] A line package consists of several flow lines running side by side. Flow lines running side by side can intersect in a projected plane with a normal to the plane running in the axial or longitudinal direction. Flow lines running side by side in this way can be arranged one behind the other. Flow lines arranged one behind the other can form a row of flow lines, i.e. a line row. Flow lines running side by side can intersect in a projected plane with a normal to the plane running in the radial or

[0016] vertical direction intersect normals of the plane. Flow lines running side by side in this way can be arranged one above the other. Flow lines arranged one above the other can form a stack of flow lines, i.e. a line stack. A line pack can consist exclusively of flow lines that overlap in at least one of the axial direction and the radial direction or the longitudinal direction and the vertical direction, i.e. of a single line row or a single line stack. A line pack can be separated from another line pack by a radial or vertical pack spacing between two flow lines in two rows and / or an axial or longitudinally extending pack spacing between two flow lines in two columns.A package distance between two flow lines may be larger than a maximum extension of a cross section of one of the flow lines in the corresponding direction.

[0017] It can be provided that the blocking is formed by repeating, adjacent partial grid spaces of the flow grid, which are arranged offset from one another in the axial direction or longitudinal direction and at least one further spatial direction. Repeating partial grid spaces can be identical and / or similar for a flow, i.e. which differ from one another by less than 5% in terms of a deceleration of the flow in space. Furthermore, it can be provided that the blocking is formed by repeating, adjacent partial grid spaces of the flow grid, which are arranged offset from one another in the transverse direction or circumferential direction and at least one further spatial direction. Furthermore, it can be provided that the blocking in the flow channel creates a heterogeneous distribution in a space occupied by the flow grid in at least one main spatial direction (axial, radial, circumferential orlongitudinal, vertical, transverse), two main spatial directions (axial and circumferential, axial and radial, radial and circumferential or longitudinal and transverse, longitudinal and vertical, transverse and vertical) or all main spatial directions, and / or in at least one extension direction formed by a linear combination of at least two main spatial directions, and / or in the flow direction. It can be provided that repeating, in particular identical or similar for a flow, i.e. differing from one another by less than 5% with regard to a deceleration of the flow in space, adjacent sub-grid spaces of the flow grating are arranged mirrored to one another.

[0018] Further advantages and features emerge from the following description of some preferred embodiments and the dependent claims.

[0019] In an advantageous embodiment of the invention, the spatially heterogeneous blocking can be distributed in the flow grid in the axial direction or longitudinal direction and / or in a main flow direction. Blocking distributed in the axial direction or longitudinal direction or in a main flow direction enables particularly efficient flow and heat transfer from the first fluid to the second fluid, or vice versa.

[0020] In particular, repeating partial grid spaces within the flow grid can be arranged offset from one another, for example, in the longitudinal direction and in the transverse direction and / or in the vertical direction, or in the axial direction and in the circumferential direction and / or in the vertical direction, or in the main flow direction and transversely and / or vertically to the main flow direction. The main flow direction can run from an inflow surface to an outflow surface of the first fluid flow and can thereby follow any kink or bend in the flow grid between the inflow surface and the outflow surface.

[0021] In a further advantageous embodiment of the invention, the spatially heterogeneous blocking in the flow grid can be heterogeneously distributed over a cross-sectional area spanned by a radial direction and a circumferential direction or by a vertical direction and a transverse direction. This advantageously resolves a flow blockage within the flow grid.

[0022] In a preferred embodiment of the invention, the flow lines in the flow grid can have a sweep. A sweep resolves the flow blockage within the flow grid in a particularly favorable, efficient, and robust manner. The sweep can be configured to span the entire length. "Span" means along the longitudinal extension of the flow lines. The longitudinal extension of the flow lines can run in a circumferential or transverse direction within the flow channel.

[0023] This allows identical or similar sub-grids to be arranged offset from one another within the flow grid. Alternatively or additionally, the sweep can be radial or vertical. The line package formed by the flow lines can be swept or have a swept pattern.

[0024] In a further preferred development of the invention, the flow lines in the flow grid can have a spanwise offset of a sweep of the flow lines. The spanwise offset can be formed by an offset of a sweep kink of a flow line relative to a sweep kink of a radially or vertically adjacent flow line in a circumferential direction or transverse direction. A spanwise offset resolves a flow blockage even more efficiently. The line package formed by the flow lines can be heterogeneously swept or have a heterogeneous sweep.In a particular development, the flow lines in the flow grid can be arranged offset from one another in the axial direction or longitudinal direction, and / or adjacent flow lines in the radial direction or vertical direction can be arranged axially offset from one another in the flow grid, and / or adjacent flow lines in the circumferential direction or transverse direction can be arranged axially offset from one another in the flow grid. By axially offsetting the adjacent flow lines, a blocking can be formed heterogeneously in an advantageously simple manner without major adjustments to the flow lines.

[0025] In a particularly preferred development, at least one flow line, preferably a plurality, particularly preferably all flow lines in the flow grid, in particular in at least one partial section of the at least one flow line, can have a non-rectilinear, in particular curved course formed by its extension between two, in particular opposite, channel walls of the flow channel, preferably a sinusoidal course and / or a polynomial course, particularly preferably with a, preferably local, foremost point and / or a, preferably local, rearmost point in the flow grid. Such a course allows the flow to be guided particularly efficiently through the flow grid in order to improve heat transfer. The partial section can extend in particular in the transverse direction or circumferential direction. The flow lines can run parallel to one another at least in sections.Furthermore, the flow lines can run parallel but offset from each other along their longitudinal extent. A local leading or trailing point represents a leading or trailing point on the leading edge or trailing edge of the curved flow line in a subsection of the longitudinal extent of the flow lines, analogous to a local extremum of a mathematical function. Accordingly, several local leading or several local trailing points of a flow line can be provided.

[0026] Furthermore, in a preferred embodiment, the flow lines of the line package can be arranged in several line stacks, and the flow lines of two adjacent line stacks can intersect in the longitudinal or axial direction, or in a main flow direction in the radial or vertical direction, or perpendicular to the main flow direction. This arrangement can achieve efficient flow guidance with an advantageously very large heat transfer surface while simultaneously achieving a heterogeneous distribution of the blocking.

[0027] Particularly preferably, at least one secondary surface, in particular a plurality of secondary surfaces, can be formed between at least two adjacent flow lines in the flow grid. This can increase heat transfer particularly effectively. Secondary surfaces can be fins, ribs, or sheets extending flatly transversely to the flow lines. Fins can be thin, plate-like structures, which can in particular be arranged in the flow direction and improve heat transfer in the heat exchanger. They increase the surface area involved in heat transfer and thus lead to more efficient heat transfer. Ribs can be protruding surface structures on one of the channel walls or one of the flow lines that protrude into the flow to increase the heat transfer area. They improve heat transfer from the surface to the surrounding fluid.Sheet metal can be used both to guide airflow and to increase stability. They can also support fins or ribs, increasing the strength and stability of the structure.

[0028] It can be provided that the secondary surfaces are arranged in a homogeneous distribution. Furthermore, it can be provided that the secondary surfaces are arranged in a heterogeneous distribution. Furthermore, it can be provided that the secondary surfaces extend between some of the flow lines or all of the flow lines transversely to the line package. Furthermore, adjacent secondary surfaces can be arranged axially offset from one another. Additionally or alternatively, adjacent secondary surfaces can be offset from one another in the transverse direction or circumferential direction. Furthermore, it can be provided that the secondary surfaces in the flow grid between two flow lines are designed as flow diversion guides. The flow diversion guides can direct the flow in a direction deviating from the axial direction or longitudinal direction. Additional flow blockages that can impede flow can be resolved by diversion guides.

[0029] It can be provided that the secondary surfaces are distributed homogeneously. Furthermore, it can be provided that the secondary surfaces are distributed heterogeneously. Furthermore, it can be provided that the secondary surfaces extend transversely to the line package between some or all of the flow lines. Furthermore, adjacent secondary surfaces can be arranged axially offset from one another. Additionally or alternatively, adjacent secondary surfaces can be arranged offset from one another in the transverse or circumferential direction.

[0030] Furthermore, it can be provided that the secondary surfaces in the flow grid between two flow lines are designed as flow diversion guides. The flow diversion guides can direct the flow in a direction deviating from the axial or longitudinal direction. By means of diversion guides, additional flow blockages that could impede flow can be eliminated.

[0031] Finally, according to an advantageous development of the invention, the flow lines can each have an integrated conduit for conducting the second fluid, and the flow lines can each have cavities adjacent to the integrated conduit, which cavities can be connected to the respective conduit via intake openings. In conjunction with a heterogeneous blocking, this achieves better heat transfer from or to the second fluid. The surface temperature of the flow lines can be influenced by intake openings to corresponding cavities, which advantageously allows an ideal temperature gradient to be established between the two fluids and thus makes heat transfer more efficient.A heat exchanger according to the invention according to yet another aspect of the invention for transferring heat from a first fluid to a second fluid has a first flow channel for guiding the first fluid and a plurality of spaced-apart flow lines for guiding the second fluid, wherein the flow lines extend through the first flow channel, running alongside one another to form a line package, wherein outer walls of the flow lines together with channel walls of the flow channel form a flow grid for the first fluid, and wherein the line package forms a blockage in the flow channel.

[0032] The object is achieved by the heat exchanger according to the invention for transferring heat from a first fluid to a second fluid of claim 11 in that the flow lines each have an integrated conduit for conducting the second fluid, and in that the flow lines each have cavities adjacent to the integrated conduit, which are connected to the respective conduit by intake openings. The surface temperature of the flow lines can be influenced by intake openings to corresponding cavities, whereby an ideal temperature gradient between the two fluids can be advantageously established and heat transfer can thus be made more efficient.

[0033] It can be provided that the intake openings are formed transversely to a flow path in the conduit. Furthermore, the intake openings can be formed at an angle to a flow path in the conduit. Furthermore, the cavities can be part of a water collection system. It can be provided that the intake openings connect the conduit to a water collection system. Furthermore, the cavities can be fluidically connected to a water collection system arranged, in particular, outside the flow grid. Furthermore, the intake openings can be arranged in front of and / or close to denser blocking sections in the flow grid, whereby a blocking effect that locally has a negative impact on heat transfer can advantageously be reduced.The density of the blocking and thus the definition of blocking sections is determined by comparing differing and non-overlapping spatial sections in the flow grid. Furthermore, the conduit pipe can have an at least partially round, in particular elliptical, in particular circular, and / or partially rectangular, in particular square, cross-section, preferably with rounded corners.

[0034] Finally, as yet another aspect of the invention, an aircraft engine is proposed which has a main flow duct for driving an engine shaft and a secondary flow duct.

[0035] The object is achieved by the aircraft engine according to the invention according to claim 12 in that a heat exchanger as described above is arranged in the bypass duct, that a part of the bypass duct is designed as the flow channel of the heat exchanger, that the bypass duct is designed to guide the first fluid, that the flow grid is formed in the bypass duct, and that housing walls of the bypass duct form the channel walls of the flow channel of the heat exchanger. By integrating a heat exchanger according to the invention in an aircraft engine, particularly good heat transfer can be achieved even at high inflow Mach numbers in the bypass duct.

[0036] It can be provided that a diffuser is arranged upstream of the heat exchanger in the bypass duct to decelerate the flow, wherein the diffuser does not decelerate the flow to below Mach 0.2, preferably 0.25, particularly preferably 0.3, in a primarily assumed operating state of the aircraft engine, in particular during cruise flight, and that an inflow Mach number at an inlet surface of the heat exchanger is at least 0.2, preferably 0.25, particularly preferably 0.3. Preferably, an upper limit of the inflow Mach number at the inlet surface of the heat exchanger can be at most 0.5.

[0037] Several heat exchangers as described above can be arranged in the bypass channel. The heat exchangers can be arranged in the bypass channel, distributed circumferentially around a core flow channel. A diffuser can be arranged upstream of each of the heat exchangers. It can also be provided that a common diffuser is formed in the bypass channel upstream of all or at least two heat exchangers.

[0038] An aircraft engine with such heat exchangers is capable of separating water from a hot exhaust gas and reusing it in a water recirculation system not further described herein, for example, advantageously to increase the mass flow in a combustion chamber. Such an aircraft with such heat exchangers can also advantageously cool the coolants used in a fuel cell more efficiently, thus effectively dissipating excess reaction heat.

[0039] According to a further preferred aspect of the invention, which may be claimed independently, a heat exchanger is provided for transferring heat from a first fluid to a second fluid. This heat exchanger has a flow channel for conducting the first fluid and a plurality of spaced-apart flow lines for conducting the second fluid, wherein the flow lines extend through the flow channel and, running alongside one another, form a line package, wherein outer walls of the flow lines, together with channel walls of the flow channel, form a flow grid for the first fluid. At least one of the lines is designed such that it is undulating, i.e. that it has at least two oppositely curved sections along its longitudinal extent. In other words, the at least one line can have a meandering shape.Preferably, a plurality of lines of the line package can be wave-shaped; in particular, all lines can be wave-shaped. The wave shape can preferably form at least one wave crest and one wave trough. In other words, the at least one line can have at least one inflection point in its curved shape, preferably two inflection points, more preferably three or more inflection points. Synergistic effects arise if the outer walls of the lines also have the shape of an aerodynamic profile. Such a design of lines in a heat exchanger has the effect that the waves generate turbulence with each change in flow direction, whereby the thermal boundary layer is better mixed and higher heat transfer coefficients can be achieved on the inside of the line.

[0040] The invention is explained in more detail with reference to the following drawings using some preferred embodiments of the invention.

[0041] Fig. 1 shows an embodiment of an aircraft engine according to the invention with a heat exchanger according to the invention in a meridian section

[0042] Fig. 2 shows a first embodiment of a heat exchanger according to the invention with an arrowed line package in a perspective view

[0043] Fig. 3 shows a second embodiment of a heat exchanger according to the invention with a heterogeneously arrowed line package in a perspective view

[0044] Fig. 4 shows a third embodiment of a heat exchanger according to the invention with axially offset flow lines in a perspective view

[0045] Fig. 5 shows a fourth embodiment of a heat exchanger according to the invention with curved flow lines in a perspective view

[0046] Fig. 6 shows a fifth embodiment of a heat exchanger according to the invention with secondary surfaces in a perspective view

[0047] Fig. 7 shows an embodiment of a profile shape of a flow line for a heat exchanger according to the invention

[0048] Fig. 1 schematically illustrates an embodiment of an aircraft engine 1 according to the invention in a meridional section. The aircraft engine 1 has an engine inlet 1a, from which downstream flow flows into a bypass duct 1b and a core flow duct 1c. The bypass duct 1b serves to generate thrust, while the core flow duct 1c primarily serves to generate power for the components of the aircraft engine 1 and the cabin systems of an aircraft (not shown). The main components of the aircraft engine 1, namely a compressor 2, a combustion chamber 3 and a turbine 4, are arranged in sequence in the flow direction in the core flow channel 1c. The aircraft engine 1 has an outer engine casing 6 surrounding the engine inlet 1a and the bypass channel 1b and an intermediate casing 7 separating the bypass channel 1b and the core flow channel 1c, wherein the intermediate casing 7 can serve as the outer casing of the flow channel 1c.A fan 5 with one or more fan stages for the intake and initial compression of air can be arranged in the engine inlet 1a. The fan 5, the compressor 2, and the turbine 4 are mechanically coupled by means of at least one shaft 8 rotating about an engine axis of rotation 8a. The fan 5 and, if appropriate, also the front low-pressure compressor stages (not shown) can be decoupled from the faster-running turbine 4, in particular from a low-pressure turbine, by a transmission 9.

[0049] A heat exchanger 10 according to the invention is arranged in the bypass duct 1b, which will be described in more detail with reference to several exemplary embodiments in FIGS. 2 to 7. A diffuser 70 can be arranged upstream of the heat exchanger 10 in the bypass duct 1b, which diffuser, particularly in the present exemplary embodiment, can decelerate the flow upstream of the heat exchanger 10 to Mach 0.3 in a predominant operating state of the aircraft engine 1. A predominant operating state can be cruising flight.

[0050] A portion of the air drawn in and compressed by the fan flows into the core flow channel 1c, where it is highly compressed by the compressor 2 to be mixed with fuel and ignited in the combustion chamber 3 and finally expanded in the turbine 4 to drive at least one shaft 8. The compressor 2 provides compressed bleed air at bleed air points for a bleed air system.

[0051] Another portion of the air drawn in and compressed by fan 5 flows into bypass duct 1b, in which heat exchanger 10 is located. At least a portion of the air flowing in bypass duct 1b flows through heat exchanger 10, wherein, in the present embodiment, the inflowing air serves as a first fluid for cooling a second fluid flowing in the heat exchanger. In the present embodiment, the second fluid can be, for example, an exhaust gas from turbine 4 or a hot gas from a fuel cell.

[0052] Fig. 2 shows a first embodiment of a heat exchanger 10 according to the invention for transferring heat from a first fluid to a second fluid in a perspective view. The heat exchanger 10 comprises a flow channel 20 for guiding the first fluid serving as a cooling fluid, in particular an air flow from a bypass duct of an aircraft engine.

[0053] The first fluid flows, as shown, in a main flow direction S in the heat exchanger 10 and the flow channel 20. The main flow direction S can result from the geometry of the flow channel 20. If the flow channel 20 were curved, the main flow direction could also change direction along its course, following a curvature of the flow channel 20. The flow channel 20 can be delimited by lateral, in particular opposing, channel walls 21, 22, as well as at the top and bottom by an upper channel wall 23 and a lower channel wall 24. The channel walls 21, 22, 23, 24 delimit a front inflow surface 25 and a rear outflow surface 26.

[0054] The heat exchanger 10 can be defined in cylindrical coordinates Ax, R, U or in Cartesian coordinates L, V, Q and can be described accordingly using the axial direction Ax, radial direction R and circumferential direction U or using the longitudinal direction L, vertical direction V and transverse direction Q. In the present case, the axial direction Ax or the longitudinal direction L is shown parallel to the main flow direction S, since the flow channel 20 also has a cuboid-shaped and thus essentially straight longitudinal extension. A more general definition of the heat exchanger 10 based on the main flow direction S is also possible. For the sake of simplicity, a coordinate system in Cartesian coordinates is used as an example below, but all possible embodiments are always meant unless an alternative in a different coordinate system is explicitly described.The heat exchanger 10 has a plurality of flow lines 30 spaced apart from one another in the vertical direction V for guiding the second fluid through the flow channel 20 between the lateral channel walls 21, 22. Only three such flow lines 30 are shown in Fig. 2 to simplify the illustration and explain the principle of the heat exchanger according to the invention. The flow lines 30 extend side by side, in particular one above the other, as a line stack 41 with three rows of lines 42, through the flow channel 20 in the transverse direction Q, transverse to its longitudinal extension in the longitudinal direction L. A single line stack 41 can form a line package 40. The flow lines 30 running side by side form, together with the channel walls 21, 22, 23, 24 of the flow channel 20, a flow grid 50 for the first fluid, wherein the line package 40 forms a heterogeneous blocking in the flow grid 50.The flow grid 50 with the heterogeneous blocking can be limited by outer surfaces of outer flow lines 30 in the line package 40.

[0055] The flow lines 30 can have a profile cross-section 31. Such a profile shape of the profile cross-section 31 is explained in more detail with reference to Fig. 7, and reference numerals relating to the profile shape are only shown in Fig. 7 due to the small representation of the profile shape in Fig. 1. The profile cross-section 31 can have, in the longitudinal direction L, behind a leading edge 32, an inflow extension 33 designed as a front rounding up to a maximum thickness 34, and taper rearward via an outflow extension 35 to a pointed trailing edge 36, wherein a longitudinal extension of the outflow extension 35 can be more than twice as large as the maximum thickness 34. The pointed trailing edge 36 advantageously prevents flow separation at the trailing edge 36. This leads to lower pressure losses in the flow grid 40, particularly in line packages 41 with more than one line stack 42.

[0056] The flow lines 30 can further have a sweep, i.e., adjacent cross-sections that are offset from one another in the longitudinal direction L, wherein a sweep kink 37 can be arranged centrally in the flow grid 40 or in the line stack 42. The sweep kink 37 of the line stack 42 simultaneously represents the foremost point in the flow grid 40. The sweep of the flow lines 30 leads to a spatially heterogeneous blocking that is distributed in the flow grid in the longitudinal direction or in the main flow direction S as well as in the transverse direction Q. Adjacent identical partial grid spaces 51, 52 of the flow grid 50 can be arranged offset from one another. In the present exemplary embodiment, the partial grid spaces 51, 52 are adjacent to one another in the transverse direction Q and offset from one another in the longitudinal direction L. This can generally result in the heterogeneous blocking.

[0057] The heterogeneous distribution of the flow and thus indirectly of the blocking by the flow grid 40 is schematically illustrated using a number of arrows of varying thickness. The blocking can be distributed over a cross-sectional area A of the flow grid. At the sweep kink 37, the blocking is greatest in the front region of the heat exchanger 10, so that the mass flow there is lower than in the region of the side walls 21, 22 of the flow channel 20. A flow velocity vector has a component running outwards in the transverse direction Q. In the region of the trailing edges 36 of the flow lines 30, this effect is reversed, since the blocking in the side region is greater in this region. In this region, the mass flow in the side region is lower than in the region behind the sweep kink 37 of the flow lines 30. These flow patterns advantageously prevent a pressure loss in the flow grid 40.

[0058] Fig. 3 shows a second exemplary embodiment of a heat exchanger 10 according to the invention with an alternative line package 40 for a flow grid 50. The flow grid 50 has a line package 40 consisting of a line stack 41 with several line rows 42. The flow lines 30 of each line row 42 can have a sweep, wherein the sweep bends 37 of adjacent flow lines 30 can be offset from one another in the transverse direction Q by an offset B. This advantageously also results in a solution to the blocking in the vertical direction V.

[0059] Fig. 4 shows a third exemplary embodiment of a heat exchanger 10 according to the invention with a line stack 41 which has an axial offset of the line rows 42 or flow lines 30. Due to the axial offset, in particular in combination with a profile cross-section 31 as described in Fig. 7, the blocking can be designed heterogeneously and thus a pressure loss between the flow lines can be advantageously reduced. In particular, a leading edge of a flow line 30 which is offset to the rear, i.e. a flow line 30 which is at the rear in the longitudinal direction L, can be arranged behind an adjacent front flow line 30. As a result, a cross-sectional widening in a front region of the rear flow line is advantageously compensated by a cross-sectional tapering of the front flow line. The blocking can thus be designed to be distributed in the longitudinal direction.

[0060] Fig. 5 shows a fourth embodiment of a heat exchanger 10 according to the invention, comprising a line stack 40, each comprising a plurality of line stacks 41 and a plurality of line rows 42. A frontmost line stack and a rearmost line stack each have five flow lines. The inner line stacks 41 located therebetween each have ten flow lines 30, forming ten line rows 42 in the line stack 40.

[0061] The individual flow lines 30 in the line stack 40 have curved paths, with the flow lines 30 in the inner line stacks 41 being formed alternatingly forward and backward between the side walls 21, 22 of the flow channel 20. The curved paths of the frontmost line stack 41 are all curved backward. The curved paths of the rearmost line stack 41 are all curved forward. The curvature of the flow lines 30 is approximately sinusoidal. Central regions of the flow lines 30 of two adjacent line stacks 41 can overlap in the longitudinal direction L of the flow channel 20.

[0062] Leading-most points on the leading edges 32 of forward-curved flow lines 30 can be arranged in the longitudinal direction L at a level with lateral connections between the channel walls 21, 22 and the leading edges 32 of the flow lines 30 of the front adjacent line stack 41. Leading-most points on the leading edges 32 of forward-curved flow lines 30 can be arranged inside the flow grid 50 in the longitudinal direction L at a level with the leading edges 36 of rearward-curved flow lines 30 of the front adjacent line stack 41.

[0063] This interwoven arrangement of flow lines of several adjacent line stacks results in a particularly efficient distribution of the blockage in the flow channel.

[0064] A further advantage of a wave-shaped pipe, as shown in Fig. 5, is that the heat transfer coefficient on the inside of the lancet is just as high as on the outside. The waves generate turbulence with every change in flow direction, which improves mixing of the thermal boundary layer and thus achieves higher heat transfer coefficients.

[0065] The principle of wavy channels can also be used in plate heat exchangers, where in some applications, wavy fins are used instead of the offset strip fins mentioned above. In these channel geometries, the waviness increases the heat transfer coefficient by up to a factor of four, depending on the precise wave parameters. Initial CFD studies by the inventors confirm this effect.

[0066] Fig. 6 shows a further development of the exemplary embodiment described in Fig. 4. Secondary surfaces 60 in the form of connecting plates are formed perpendicular to the course of the flow lines 30 and, together with the flow lines 30, deflect the flow. This makes it possible to achieve particularly efficient flow guidance. The secondary surfaces can in particular be combined with the embodiments described in Figs. 2 to 6, whereby local flow channels are created which, arranged offset from one another, have an offset blocking. The secondary surfaces can also have shapes other than the one shown. In particular, the secondary surfaces can project from the flow lines as ribs. Furthermore, the secondary surfaces can each connect one part, in particular two, of the flow lines to one another. Such secondary surfaces can be arranged offset from one another in the transverse direction Q or circumferential direction U.

[0067] Fig. 7 shows the profile cross-section 31 of a flow line 30, also described in Fig. 2. The profile cross-section 31 can have on its surface, both on the upper side and on the lower side in the longitudinal direction L behind a leading edge 32, an inflow extension 33 designed as a front rounding up to a maximum thickness 34, and taper rearward via an outflow extension 35 to a pointed trailing edge 36, wherein a longitudinal extension of the outflow extension 35 can be more than twice as large as the maximum thickness 34. The pointed trailing edge 36 advantageously prevents flow separation at the trailing edge 36. It can be provided that the surfaces on the upper side and the lower side are designed differently and / or have different curvatures. The front rounding 33 and the outflow extension 35 form outer surfaces of the flow lines 30.The extension of the outflow extension 35 is more than twice as large as the extension of the front rounding 33.

[0068] In the profile cross-section shown, an integrated conduit 38, designed as a round tube, is arranged to conduct the second fluid. Further cavities 39 are formed outside the integrated conduit 38 for draining condensate, in particular water, from the integrated conduit 38. To allow the condensate to be extracted, the cavities 39 are connected to the integrated conduit 38 via extraction openings 39a in channel walls 38a of the integrated conduit 38. Furthermore, a cross-section of the maximum thickness intersects the integrated conduit 38, in particular at its greatest vertical extent.

[0069] By extracting condensate, the heat transfer from the second fluid in the integrated conduit 38 is advantageously improved. List of reference symbols

[0070] 1 aircraft engine

[0071] 1a enema

[0072] 1 b bypass channel

[0073] 1c core flow channel

[0074] 2 compressors

[0075] 3 combustion chamber

[0076] 4 turbines

[0077] 5 fans

[0078] 6 Engine outer casing

[0079] 7 Intermediate housing

[0080] 8 Engine shaft

[0081] 8a Engine axis

[0082] 9 gearboxes

[0083] 10 heat exchangers

[0084] 20 flow channel

[0085] 21 (lateral) channel wall

[0086] 22 (side) channel wall

[0087] 23 (upper) canal wall

[0088] 24 (lower) canal wall

[0089] 25 Inflow area

[0090] 26 outflow area

[0091] 30 Flow line

[0092] 31 Profile cross-section

[0093] 32 leading edge

[0094] 33 front rounding

[0095] 34 maximum thickness

[0096] 35 Outflow extension 36 Trailing edge

[0097] 37 Sweep kink

[0098] 38 integrated conduit

[0099] 38a Canal wall

[0100] 39 cavity

[0101] 39a Suction opening

[0102] 40 cable packages

[0103] 41 line stacks

[0104] 42 cable row

[0105] 50 flow grids

[0106] 51 sublattice space

[0107] 52 sublattice space

[0108] 60 secondary surfaces

[0109] 70 Diffuser

[0110] Ax axial direction

[0111] R Radial direction

[0112] U circumferential direction

[0113] L longitudinal direction

[0114] V Vertical direction

[0115] Q transverse direction

[0116] S Main flow direction

[0117] A cross-sectional area

[0118] B Offset

Claims

Patent claims 1. Heat exchanger (10) for transferring heat from a first fluid to a second fluid, with a flow channel (20) for guiding the first fluid, a plurality of spaced-apart flow lines (30) for guiding the second fluid, wherein the flow lines (30) extend through the flow channel (20) and, running alongside one another, form a line package (40), wherein outer walls (33, 35) of the flow lines (30) together with channel walls (21, 22) of the flow channel (20) form a flow grid (50) for the first fluid, and wherein the line package (40) forms a blocking in the flow grid (50), characterized in that the blocking in the flow grid (50) has a spatially heterogeneous distribution.

2. Heat exchanger according to claim 1, characterized in that the spatially heterogeneous blocking is formed distributed in the flow grid (50) in the axial direction (Ax) or longitudinal direction (L) and / or in a main flow direction (S).

3. Heat exchanger according to one of the preceding claims, characterized in that the spatially heterogeneous blocking in the flow grid (50) is heterogeneously distributed in a cross-sectional area (A) spanned by a radial direction (R) and a circumferential direction (U) or a cross-sectional area (A) spanned by a vertical direction (V) and a transverse direction (Q).

4. Heat exchanger according to one of the preceding claims, characterized in that the flow lines (30) in the flow grid (50) have a sweep.

5. Heat exchanger according to one of the preceding claims, characterized in that the flow lines (30) in the flow grid (50) have a spanwise offset (B) of a sweep of the flow lines (30).

6. Heat exchanger according to one of the preceding claims, characterized in that the flow lines (30) in the flow grid (50) are arranged offset from one another in the axial direction (Ax) or longitudinal direction (L), and / or that flow lines (30) adjacent to one another in the radial direction (R) or vertical direction (V) in the flow grid (50) are arranged axially offset from one another, and / or that flow lines (30) extending adjacent to one another in the circumferential direction (U) or transverse direction (Q) in the flow grid (50) are arranged axially offset from one another.

7. Heat exchanger according to one of the preceding claims, characterized in that at least one flow line (30), preferably a plurality, particularly preferably all flow lines (30) in the flow grid (50), in particular in at least one partial section of the at least one flow line (30), have a non-rectilinear course formed by their extension between two channel walls (21, 22) of the flow channel (30).

8. Heat exchanger according to one of the preceding claims, characterized in that the flow lines (30) of the line package (40) are arranged in several line stacks (41) and flow lines (30) two adjacent line stacks (41) intersect in the longitudinal extension (L) or axial extension (Ax) or in a main flow direction (S) in the radial direction (R) or vertical direction (V) or perpendicular to the main flow direction (S).

9. Heat exchanger according to one of the preceding claims, characterized in that at least one secondary surface (60) is formed between at least two adjacent flow lines (30) in the flow grid (50), in particular a plurality of secondary surfaces (60) are formed.

10. Heat exchanger according to one of the preceding claims, characterized in that the flow lines (30) each have an integrated conduit (38) for guiding the second fluid, and in that the flow lines (30) each have cavities (39) adjacent to the integrated conduit (38) which are connected to the respective integrated conduit (38) by suction openings (39a).

11. Heat exchanger (10) for transferring heat from a first fluid to a second fluid, comprising a flow channel (20) for conducting the first fluid, a plurality of spaced-apart flow lines (30) for conducting the second fluid, wherein the flow lines (30) extend through the flow channel (20) and, running alongside one another, form a line package (40), wherein outer walls (33, 35) of the flow lines (30) together with channel walls (21, 22) of the flow channel (20) form a flow grid (50), and wherein the line package (40) forms a blocking in the flow grid (50), characterized in that the flow lines (30) each have an integrated line pipe (38) for conducting the second fluid, and that the flow lines (30) each have cavities (39) adjacent to the integrated line pipe (38), which are connected to the respective integrated line pipe (38) by intake openings (39a).

12. An aircraft engine (1), comprising a main flow duct (1c) for driving an engine shaft, a bypass duct (1b), characterized in that a heat exchanger (10) according to one of the preceding claims is arranged in the bypass duct (1b), that a part of the bypass duct (1b) is designed as the flow duct (20) of the heat exchanger (10), that the bypass duct (1b) is designed to guide the first fluid, that housing walls of the bypass duct (1b) form the duct walls (21, 22) of the flow duct (20) of the heat exchanger (10).

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