Heat exchanger for an aircraft propulsion system and its method of use

Abstract

A heat exchanger (1) for an aircraft propulsion system comprising a main circuit (3) including a main channel (4) connected to a wall (2) exposed to an airflow (F) and through which a refrigerant (H) circulates, the heat exchanger (1) including a standby circuit (10) including a standby channel (11) connected to the wall (2) and a standby valve (14) including a nominal closed position (A) prohibiting the admission of the refrigerant (H) into the standby channel (11), the heat exchanger (1) including a measuring element configured to measure the temperature (T) of the refrigerant (H), the standby valve (14) being configured to be controlled in an open position permitting the circulation of the refrigerant (H) in the standby channel (10) when the temperature (T) is above a predetermined temperature (Tref). Abstract figure: Figure 2

Description

Title of the invention: Heat exchanger for an aircraft propulsion system and its method of use. Technical field

[0001] The present invention relates to the field of aircraft propulsion system heat exchangers, in particular of the surface type, especially of the air-oil type.

[0002] As is known, an aircraft turbomachine comprises a set of rotating components, such as a fan, one or more compressors, one or more turbines, an accessory drive housing, etc. Such rotating components require cooling and lubrication by circulating a coolant, usually oil, in contact with the rotating portions.

[0003] As is known, oil heats up upon contact with the rotating parts of rotating components and must itself be cooled. French patent application FR3094753A1 describes the integration of a surface-type heat exchanger on the nacelle of an aircraft turbomachine, comprising a set of channels formed on the wall. The oil, forming the hot source, circulates in the channels and is cooled by convection with the airflow circulating in the secondary channel or outside the nacelle, forming the cold source. Once cooled, the oil is directed back to the rotating components to be cooled and lubricated, in a closed circuit.

[0004] In practice, the efficiency of the surface heat exchanger and the cooling requirements of the aircraft turbomachine vary depending on flight conditions, and in particular on the ambient air temperature. The sizing of the surface heat exchanger must, in particular, ensure increased cooling in the event of exposure to very high ambient temperatures or failure, which increases its mass and size.

[0005] Furthermore, in the event of prolonged exposure to very low ambient temperatures and / or when the refrigerant flow rate is too low, the refrigerant is likely to solidify in the channels of the surface heat exchanger. Such conditions can be encountered during an in-flight shutdown of the turbomachine or during prolonged grounding of the aircraft in very cold weather. These conditions slow down or even prevent the circulation of the refrigerant in the channels, which disrupts the cooling of the hot areas of the turbomachine after engine start-up or restart.

[0006] To remedy this, it is known from patent application FR3126444A1 to activate a safe heating device in the presence of very low temperatures, which takes the form of resistive cables or air ducts extending in such a way internal within the channels. This necessitates larger diameter channels to maintain an equivalent flow rate, which increases the mass and size of the surface heat exchanger.

[0007] The invention thus aims to reduce the cost, mass and size of an aircraft propulsion system heat exchanger, in particular of the surface type, especially of the air-oil type, while ensuring efficient cooling in all flight conditions. PRESENTATION OF THE INVENTION

[0008] The invention relates to a heat exchanger for an aircraft propulsion assembly comprising a wall exposed to an airflow, the heat exchanger comprising a main refrigerant circuit including at least one main channel connected to the wall and in which the refrigerant is configured to circulate so as to be cooled by the airflow.

[0009] The invention is remarkable in that the heat exchanger comprises: • a standby circuit comprising at least one standby channel connected to the wall and a standby valve comprising a nominal closed position prohibiting the admission of refrigerant into the standby channel, • a measuring device configured to measure the temperature of the refrigerant in the main circuit, the standby valve being configured to be controlled in an open position allowing the refrigerant to circulate in the standby channel when the temperature is above a predetermined temperature.

[0010] The heat exchanger according to the invention advantageously features a main circuit sized for nominal operating conditions, with reduced cost, mass, and size. The standby circuit advantageously allows for increased or maintained cooling performance in the event of a failure, in-flight shutdown, and / or extreme ambient temperatures. The heat exchanger according to the invention thus has a compact and economical design that ensures efficient cooling under all flight conditions.

[0011] According to one aspect of the invention, the heat exchanger is a surface heat exchanger. The heat exchanger is said to be a surface heat exchanger in that the heat exchange takes place on a heat exchange surface formed by the wall on which the main and auxiliary channels extend or are fixed. The wall typically takes the form of a portion of the external fairing of the aircraft propulsion assembly, in particular the nacelle, a portion of the external wall of the secondary duct, or a portion of the internal wall of the secondary duct. Such a surface heat exchanger is distinguished in particular by of a matrix heat exchanger, also known as a volumetric heat exchanger, where the channels extend into the internal volume of an air stream.

[0012] According to another aspect of the invention, the heat exchanger is of the matrix type. Preferably, the matrix heat exchanger comprises a plurality of main refrigerant circuits, preferably two, and a plurality of standby circuits, preferably two.

[0013] According to a preferred aspect, the wall of the heat exchanger at least partially delimits the main channel. According to a preferred aspect, the wall of the heat exchanger at least partially delimits the waiting channel. The heat exchanger thus has a small footprint and helps to preserve aerodynamics.

[0014] According to another aspect, the main channel is fixed to the wall of the heat exchanger. Similarly, the spare channel is fixed to the wall of the heat exchanger or to the main channel.

[0015] According to a preferred aspect of the invention, the standby valve is of the thermostatic type and forms the measuring element. This allows circulation in the standby circuit to be permitted in a simple and passive manner.

[0016] According to a preferred aspect, the predetermined temperature is greater than 130° and preferably less than 170°. The standby circuit advantageously provides supplementary cooling in the presence of very hot outside temperatures and / or in the event of a failure when the main circuit does not allow sufficient cooling of the refrigerant.

[0017] According to one aspect of the invention, the heat exchanger comprises a bypass circuit opening into the main circuit upstream and downstream of the main channel. The bypass circuit includes a bypass valve configured to allow the circulation of the refrigerant in the bypass circuit when the refrigerant pressure in the main circuit exceeds a predetermined pressure. The bypass circuit advantageously allows bypassing the main channels when the refrigerant flow rate is too low in the main circuit, for example, when the refrigerant freezes following exposure to very low temperatures and / or a prolonged stop in flight, leading to increased pressure drops, reduced flow rate, and increased pressure in the main channel.The bypass circuit diverts the refrigerant to ensure a minimum flow rate in the heat exchanger, while the standby circuit cools the refrigerant, either in addition to or instead of the main circuit. In case of freezing, the bypass and standby circuits work together to maintain effective cooling of the refrigerant.

[0018] According to a preferred aspect, the diversion circuit extends outside the wall. The diversion circuit is thus less exposed to very low external temperatures, which avoids The refrigerant in this circuit does not solidify, unlike in the main circuit. The standby circuit, on the other hand, is free of refrigerant to prevent it from solidifying.

[0019] According to a first aspect of the invention, the standby channel extends alongside the main channel, preferably between two adjacent main channels of the main circuit. The standby channel, like the main channel, thus ensures the cooling of the refrigerant. Advantageously, both the standby channel and the main channel are easily accessible during maintenance.

[0020] According to a second aspect of the invention, the standby channel covers the main channel. The standby channel thus ensures, like the main channel, the cooling of the refrigerant. Alternatively, the main channel covers the standby channel. When the refrigerant solidifies in the main channel, the circulation of refrigerant in the standby channel warms the solidified refrigerant in the main channel and restores fluid circulation.

[0021] According to one aspect of the invention, the heat exchanger includes a device for draining the standby circuit comprising: • An air supply line including a controllable inlet valve to allow air to be admitted into the standby circuit, • A refrigerant fluid drain line outside the circuit is in place.

[0022] After use of the standby circuit, when the turbomachine is shut down, the draining device advantageously allows air to be injected into the standby channels to expel any remaining refrigerant from the drain line. The standby circuit is thus free of refrigerant for its next use. The draining device advantageously eliminates the need for operators to perform ground-based maintenance.

[0023] The invention also relates to an aircraft propulsion assembly comprising a heat exchanger as described above.

[0024] The invention also relates to a method of using the heat exchanger, the standby valve being initially in the nominal closed position and the standby channel being initially free of refrigerant, the method of use comprising, when the temperature of the refrigerant in the main circuit is higher than the predetermined temperature, a step of controlling the open position of the standby valve, so as to allow the circulation of the refrigerant in the standby channel.

[0025] According to a first aspect of the invention, the refrigerant circulates in the main channel and in the standby channel so as to promote the cooling of the refrigerant. This makes it possible to increase the heat exchange between the refrigerant and the airflow, for example in the event of exposure to high outside temperatures and / or in the event of a breakdown.

[0026] According to a second aspect of the invention, the refrigerant circulating in the standby channel allows the refrigerant in a frozen state in the main channel to be warmed so as to restore the circulation of the refrigerant in the main channel. The standby circuit thus makes it possible to cool the refrigerant in addition to, or even instead of, the main circuit in the presence of very low outside temperatures which have frozen the refrigerant in the main channels and slowed or even prevented its circulation.

[0027] The invention also relates to a method of draining the standby circuit of the heat exchanger as described above, the standby valve being initially in the open position, the inlet valve being initially closed and the refrigerant initially circulating in the standby channel, the maintenance method comprising a step of controlling the nominal closed position of the standby valve and a step of controlling the opening of the inlet valve allowing the admission of air into the standby circuit, so as to drain the refrigerant from the standby circuit. PRESENTATION OF THE FIGURES

[0028] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0029] Fig. 1 is a schematic representation in longitudinal half-section of an aircraft propulsion assembly comprising a surface heat exchanger according to one embodiment of the invention.

[0030] Fig. 2 is a schematic representation of a surface heat exchanger whose standby circuit is in the nominal closed position according to a first embodiment of the invention.

[0031] Fig. 3 is a schematic representation of the surface heat exchanger of Fig. 2 whose standby circuit is in the open position when the refrigerant exceeds a predetermined threshold, in the presence of high outside temperatures or high heat dissipation by the propulsion assembly.

[0032] Fig. 4 is a schematic representation of the surface heat exchanger of Fig. 2 whose standby circuit is in the open position when exposed to low external temperatures.

[0033] The [Fig.5] is a schematic perspective representation of the circuit awaiting the surface heat exchanger according to one embodiment of the invention.

[0034] Fig. 6 is a schematic cross-sectional representation of the circuit awaiting Fig. 5.

[0035] The [Fig.7] is a schematic perspective representation of the circuit awaiting the surface heat exchanger according to a second embodiment of the invention.

[0036] Fig. 8 is a schematic cross-sectional representation of the circuit awaiting Fig. 7.

[0037] Fig. 9 is a schematic representation of a surface heat exchanger comprising a device for draining the standby circuit according to another embodiment of the invention.

[0038] Fig. 10 is a schematic representation of the draining device of Fig. 9.

[0039] It should be noted that the figures set out the invention in detail to illustrate implementing the invention, said figures can of course be used to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0040] With reference to [Fig. 1], an aircraft comprises one or more propulsion assemblies 30 including a turbomachine 31 and a nacelle 32. The aircraft turbomachine 31 extends along a longitudinal axis X oriented from upstream to downstream and is configured to enable the propulsion of the aircraft from the acceleration of an airflow F circulating from upstream to downstream in the turbomachine 31. The nacelle 32 extends around the turbomachine 31 and guides the airflow F in the turbomachine 31.

[0041] As illustrated in [Fig. 1], the aircraft turbomachine 31 comprises a set of rotating components, including a fan 33, one or more compressors 34, 35, one or more turbines 36, 37, an accessory drive housing (not shown), and one or more accessory power generators (not shown), which are cooled and lubricated by the circulation of a coolant, usually oil, in contact with the rotating portions of the rotating components. The coolant circuit transfers the heat generated by the friction of the rotating portions to the coolant, thereby cooling the rotating components of the aircraft turbomachine.

[0042] With reference to Figures 1 and 2, the invention relates to a heat exchanger 1 for an aircraft propulsion assembly 30 comprising a wall 2 exposed to an airflow F, the heat exchanger 1 comprising a main circuit 3 of refrigerant fluid H comprising one or more main channels 4 connected to the wall 2 and in which the refrigerant fluid H is configured to flow upstream to downstream so as to be cooled by the airflow F.

[0043] Still with reference to [Fig.2] and according to the invention, the heat exchanger 1 comprises: • a standby circuit 10 comprising one or more standby channels 11 connected to the wall 2 and a standby valve 14 comprising a nominal closed position A prohibiting the admission of refrigerant H into the standby channels 11, • a measuring device configured to measure the temperature T of the refrigerant H in the main circuit 3, the standby valve 14 being configured to be controlled in an open position B (see figures 3 and 4) allowing the circulation of the refrigerant H in the standby channels 11 when the temperature T is above a predetermined temperature Tref.

[0044] The heat exchanger 1 cools the refrigerant H, typically oil, after it has passed through contact with the areas to be cooled in the aircraft turbomachine 31, in particular the rotating parts of the rotating components. The refrigerant H is cooled by thermal convection with the airflow F circulating along the wall 2 of the heat exchanger 1. Under nominal operating conditions (see [Fig. 2]), i.e., in the absence of failure and / or extreme temperature conditions, the airflow F circulates only in the main circuit 3, the standby channel 10 being free of refrigerant H.

[0045] In the event of exposure to very high external temperatures, typically above 40°C or 25°C above the standard temperature corresponding to the flight altitude, and / or in the event of a failure (see [Fig.3]), the temperature T of the refrigerant R exceeds the predetermined temperature Tref, which triggers the circulation of the refrigerant R in the standby circuit 10. The refrigerant R circulates both in the main circuit 3 and in the standby circuit 10, which increases the cooling performance and allows the temperature T of the refrigerant R to be brought back below the predetermined temperature Tref.

[0046] Furthermore, in the event of freezing of the refrigerant H in the main circuit 3, for example in the event of prolonged exposure to very low outside temperatures, typically below -40°C (see [Fig.4]) or after a prolonged shutdown, the circulation of the refrigerant H in the standby circuit 10, which until then was free of refrigerant R and therefore protected from the risk of freezing, makes it possible to replace the circulation of the refrigerant H in the main circuit 3 as well as to warm the frozen refrigerant H in the main circuit 3.

[0047] The heat exchanger 1 according to the invention thus has a main circuit 3 sized for nominal operating conditions, offering reduced cost, mass, and size. The standby circuit 10 advantageously allows for increasing or maintaining cooling performance in the event of a failure and / or extreme outside temperatures. The heat exchanger 1 thus presents a compact and economical architecture enabling efficient cooling in all flight conditions.

[0048] With reference to [Fig.2], the heat exchanger 1 is typically supplied with refrigerant H by a pump 25, in particular a high-pressure type, drawing the refrigerant H from a reservoir 24. At the outlet of the heat exchanger 1, the refrigerant H is guided to the areas to be cooled 22 of the aircraft turbomachine 31, typically the rotating parts of the rotating components, and then is discharged back to the reservoir 24. The circulation of the refrigerant H is thus in a closed circuit.

[0049] According to a preferred aspect illustrated in [Fig. 1], the heat exchanger 1 is of the surface type 1. In this example, the heat exchanger 1 is formed on the fan casing of the aircraft turbomachine 31, the wall 2 externally delimiting the secondary duct 38 of the aircraft turbomachine 31. The surface heat exchanger 1 could also be positioned at other locations on the turbomachine 31 or the nacelle 32, preferably in contact with the airflow F circulating in the secondary duct 38 or outside the nacelle 32. The invention also applies to a matrix heat exchanger.

[0050] According to a preferred aspect illustrated in [Fig.2], the heat exchanger 1 also includes a bypass circuit 20 opening into the main circuit 3 upstream and downstream of the main channels 4. The bypass circuit 20 includes a bypass valve 21, typically a pressure relief valve, configured to allow circulation of the refrigerant H in the bypass circuit 20 when the pressure P of the refrigerant H in the main circuit 3 is greater than a predetermined pressure Pref.

[0051] The bypass valve 21 is typically open when the refrigerant H solidifies in the main channel 4, namely in the presence of very low ambient temperatures. This reduces or even prevents the circulation of the refrigerant H in the main channel 4, which increases the pressure P above the predetermined pressure Pref. The bypass circuit 20 advantageously bypasses the main channel 4 to maintain the circulation of the refrigerant H. Unlike the standby circuit 10, the bypass circuit 20 is not defined on the wall 2 but typically extends internally within the aircraft propulsion assembly 30 to be protected from very low ambient temperatures. Unlike the standby circuit 10, the bypass circuit 20 is designed to maintain a flow of refrigerant H but does not cool the refrigerant H or heat the main channel 3.

[0052] With reference to [Fig. 2], the main circuit 3 typically comprises several main channels 4, an upstream distributor 5, and a downstream manifold 6. The distributor 5 is configured to distribute the refrigerant H into the main channels 4. The manifold 6 is configured to collect the refrigerant H into Main channel outlet 4. The main channels 4 extend side by side, in this example transversely to the longitudinal axis X. The main channels 4 are connected to the wall 2, and are preferably partially delimited by the wall 2. The main channels 4 typically have a U-shaped wall fixed to the wall 2, preferably by welding, preferably by friction stir.

[0053] With further reference to [Fig. 2], the waiting circuit 10 typically comprises several waiting channels 11, an upstream distributor 12, and a downstream manifold 13. The distributor 12 is configured to distribute the refrigerant H into the waiting channels 11. The manifold 13 is configured to collect the refrigerant H at the outlet of the waiting channels 11. The waiting channels 11 extend side by side, in this example transversely with respect to the longitudinal axis X. The waiting channels 11 are connected to the wall 2 and are preferably partially delimited by the wall 2. The waiting channels 11 typically have a U-shaped wall fixed to the wall 2, preferably by welding, preferably by friction stir welding.

[0054] With further reference to [Fig. 2], the standby valve 14 of the standby circuit 10 is typically of the thermostatic type and allows the circulation of the refrigerant H in the standby channels 11 when the temperature T of the refrigerant H exceeds the predetermined temperature Tref. The predetermined temperature Tref is preferably greater than 130°C and preferably less than 170°C.

[0055] In the example of Figures 5 and 6, each waiting channel 11 extends between two adjacent main channels 4. The waiting channels 11 and the main channels 4 thus extend side by side to minimize bulk. The waiting channels 11 and the main channels are typically partially delimited by the wall 2. In the event of freezing in the main channels 4, the waiting channels 11 allow the main channels 4 located on either side to be heated. Advantageously, the main channels 4 and the waiting channels 11 are easily accessible during maintenance, particularly for detecting any leaks.

[0056] In the example shown in Figures 7 and 8, each waiting channel 11 covers a main channel 4. In this example, the waiting channels 11 are fixed to the wall 2 so as to completely cover the main channels 4. In other words, the main channel 4 extends internally into a waiting channel 11. Alternatively, the waiting channels 11 are fixed to the main channels 4 so as to partially cover them. This promotes heat exchange between the waiting channels 11 and the main channels 4 in the event of the refrigerant R freezing. Alternatively, the main channels 4 could cover the waiting channels 11.

[0057] Preferably, as illustrated in Figures 2 to 4, the supply of refrigerant H to the main circuit 3 and the standby circuit 10, and preferably to the bypass circuit 20, is common. Similarly, and preferably also for the discharge of refrigerant H.

[0058] According to a preferred aspect, a pressure or temperature sensor is mounted in the standby circuit 1. This makes it possible to detect the use of the standby circuit 10 above a predetermined threshold and to warn of a need for ground maintenance in order to drain the refrigerant H remaining in the standby channels 11 before the next use.

[0059] According to another preferred aspect illustrated in Figures 9 and 10, the heat exchanger 1 also includes a drain device 27 configured to drain the refrigerant H present in the standby channels 11 after their use (standby valve 14 in the open position A) when the aircraft propulsion assembly 30 is shut down. This ensures that the standby channels 11 are free of refrigerant H at the next use and are thus protected from the risk of refrigerant H freezing.

[0060] As illustrated in Figures 9 and 10, the drainage device 27 comprises: • An air supply line 15 G including an controllable inlet valve 16 to allow the admission of air flow G into the standby circuit 10, • A drain line 17 configured to drain the air-driven refrigerant H out of the standby circuit 10.

[0061] Preferably, as illustrated in Figures 9 and 10, the drain line 17 includes an air-oil separation system 26, typically a deaerator, configured to separate the air G from the refrigerant H. The drain line 17 allows the refrigerant H to be reinjected into the closed refrigerant H circuit.

[0062] According to a first aspect illustrated in [Fig. 9], the supply line 15 draws air G from the open air, typically from the secondary channel 38 or outside the aircraft turbomachine 31. The inlet valve 16 is typically in the form of a check valve adapted to allow the admission of air G into the standby channels 11 when the pressure in the supply line 15 becomes greater than the pressure in the standby channels 11 when the aircraft turbomachine 31 is stopped. Such a passively controlled draining device 27, without intervention from an operator or a computer, advantageously ensures automatic draining of the standby channels 11 after their use.

[0063] According to a second aspect illustrated in [Fig. 10], the air G from the supply line 15 is taken from the aircraft turbomachine 31, preferably at the fan 33 or the low-pressure compressor 34, at a temperature below 150°C. The air G from the supply line 15 is typically stored in a tank 19.

[0064] Preferably, as illustrated in [Fig. 10], the draining device 27 comprises a filling valve 18 mounted upstream of the reservoir 19, with the inlet valve 16 mounted downstream. The filling valve 18 and the inlet valve 16, typically check valves, passively allow the reservoir 19 to be filled with air G and admitted into the waiting channels 11, respectively, as described later in the maintenance procedure.

[0065] According to a preferred aspect, the aircraft propulsion assembly 30 comprises a cowling mounted on a pivot axis and on which the heat exchanger 1 extends vertically between a high upstream position located on the pivot axis and a low downstream position relative to gravity in nominal operation of the aircraft propulsion assembly 30. Preferably, the cowling includes a removable fluid connection mounted at the low downstream position through which the drain line extends. This facilitates draining because it is no longer necessary for the drain line 17 to return to the high upstream position where the pivot axis is located in order to reach the air-oil separation system 26 of the aircraft propulsion assembly 30.

[0066] One method of using the heat exchanger 1 is as follows:

[0067] With reference to [Fig. 2], initially, the refrigerant H circulates only in the main circuit 3. The standby valve 14 is in the nominal closed position A, the standby channels 11 being free of refrigerant H. The bypass valve 21 is closed.

[0068] With reference to [Fig.3], during exposure to very high external temperatures and / or in the event of a failure, the temperature T of the refrigerant H in the main circuit 3 becomes greater than the predetermined temperature Tref, which controls the open position B of the standby valve 14. The refrigerant H circulates both in the main channels 4 and in the standby channels 11, which increases the cooling of the refrigerant H.

[0069] With reference to [Fig. 4], when exposed to very low temperatures and / or after a prolonged shutdown, the refrigerant H becomes viscous or even solidifies in the main channels 3, which reduces or even prevents its circulation. The pressure P of the refrigerant H increases and exceeds the predetermined pressure Pref, which triggers the opening of the bypass valve 21. The refrigerant H circulates in the bypass circuit 20, which reduces cooling performance and increases the temperature T of the refrigerant H. When the temperature T of the refrigerant H becomes higher than the predetermined temperature Tref, the open position B of the standby valve 14 is triggered. The refrigerant H then circulates in the standby channels 11, which ensures its cooling. Furthermore, the refrigerant H in the waiting channels 11 allows the refrigerant fluid H frozen in the main channels 4 to be warmed and allows circulation to be restored.

[0070] With reference to [Fig. 10], a method for draining the standby circuit 10 of the heat exchanger 1 after use is as follows: • Initially, the standby valve 14 is in the open position B and the refrigerant H flows in the standby channels 11 as illustrated in Figures 3 and 4. The inlet valve 16 is closed. • After the aircraft turbomachine 31 has stopped, the standby valve 14 is commanded to the nominal closed position A. The inlet valve 16 is opened to allow the admission of air G from the supply line 15 into the standby circuit 10.

[0071] Preferably, as illustrated in [Fig. 10], during takeoff and climb of the aircraft, the air pressure G at the sampling point increases and exceeds the air pressure G in the tank 19, which opens the filling valve 18. The inlet valve 16 is closed. This fills the tank 19 with air G. Preferably, a pressure relief valve is positioned upstream of the filling valve 18 to prevent overpressure.

[0072] Still with reference to [Fig. 10], during the descent, landing and taxiing of the aircraft, the air pressure G at the sampling point becomes lower than that in the tank 19, which closes the filling valve 18. The inlet valve 16 is closed.

[0073] Still with reference to [Fig.10], after the aircraft turbomachine 31 has stopped, with the standby valve 14 in the nominal closed position A, the pressure of the refrigerant H in the standby circuit 10 falls below the pressure in the tank 19, which ensures the passive opening of the inlet valve 16. The air G admitted into the standby channels 11 allows the refrigerant H to be pushed out of the standby circuit 10 into the drain line 17.

[0074] The operating and emptying processes are advantageously passive, requiring no action from an operator or a control device.

Claims

Demands

1. Heat exchanger (1) for an aircraft propulsion assembly (30) comprising a wall (2) exposed to an airflow (F), the heat exchanger (1) comprising a main circuit (3) of refrigerant (H) comprising at least one main channel (4) connected to the wall (2) and in which the refrigerant (H) is configured to circulate so as to be cooled by the airflow (F), the heat exchanger (1) being characterized in that it comprises: • a standby circuit (10) comprising at least one standby channel (11) connected to the wall (2) and a standby valve (14) comprising a nominal closed position (A) prohibiting the admission of refrigerant (H) into the standby channel (11), • a measuring element configured to measure the temperature (T) of the refrigerant (H) in the main circuit (3),the standby valve (14) being configured to be controlled in an open position (B) allowing the circulation of the refrigerant (H) in the standby channel (11) when the temperature (T) is above a predetermined temperature (Tref).

2. Heat exchanger (1) according to claim 1, of the surface type.

3. Heat exchanger (1) according to any one of claims 1 and 2, comprising a bypass circuit (20) opening into the main circuit (3) upstream and downstream of the main channel (4), the bypass circuit (20) comprising a bypass valve (21) configured to permit the circulation of the refrigerant (H) in the bypass circuit (20) when the pressure (P) of the refrigerant (H) in the main circuit (3) is greater than a predetermined pressure (Pref).

4. Heat exchanger (1) according to any one of claims 1 to 3, wherein the standby channel (11) extends juxtaposed to the main channel (4), preferably between two adjacent main channels (4) of the standby circuit (3).

5. Heat exchanger (1) according to any one of claims 1 to 3, wherein the waiting channel (11) covers the main channel (4).

6. Heat exchanger (1) according to any one of claims 1 to 5, comprising a draining device (27) for the standby circuit (10) comprising: • An air supply line (15) (G) comprising an inlet valve (16) controllable to permit the admission of air (G) into the standby circuit (10), and • A refrigerant (H) drain line (17) out of the standby circuit (10).

7. Method of using the heat exchanger (1) according to any one of claims 1 to 6, the standby valve (14) being initially in the nominal closed position (A) and the standby channel (11) being initially free of refrigerant (H), the method of use comprising, when the temperature (T) of the refrigerant (H) in the main circuit (3) is greater than the predetermined temperature (Tref), a step of controlling the open position (B) of the standby valve (14), so as to allow the circulation of the refrigerant (H) in the standby channel (11).

8. Method of use according to claim 7, wherein the refrigerant (H) circulates in the main channel (4) and in the waiting channel (11) so as to promote the cooling of the refrigerant (H).

9. A method of use according to claim 7, wherein the refrigerant (H) circulating in the waiting channel (11) allows the refrigerant (H) in a frozen state in the main channel (4) to be warmed so as to restore the circulation of the refrigerant (H) in the main channel (4).

10. Method of draining the standby circuit (10) of the heat exchanger (1) according to claim 6, the standby valve (14) being initially in the open position (B), the inlet valve (16) being initially closed and the refrigerant (H) initially circulating in the standby channel (11), the maintenance method comprising a step of controlling the nominal closed position (A) of the standby valve (14) and a step of controlling the opening of the inlet valve (16) permitting the admission of air (G) into the standby circuit (10), so as to drain the refrigerant (H) from the standby circuit (10).