Device for detecting and characterizing a fouling deposit on a wall, comprising a thermal probe and at least one thermal guard surrounding it.

Abstract

Device for detecting and characterizing soiling on a wall, comprising a thermal probe and at least one surrounding thermal guard. The invention relates to a device (100) for detecting and characterizing soiling on a support wall (3), comprising: - a thermal probe (1) configured to be fixed to the wall and comprising at least one resistor configured to generate a heat flux towards the wall when the thermal probe is fixed to the wall, and - at least one main thermal guard (10) configured to be fixed to the wall in contact with the thermal probe at least over a portion of the latter's perimeter, preferably over a portion greater than 50%, 80%, 90%, or equal to 100% of the latter's perimeter, the at least one main thermal guard comprising at least an active and / or passive portion configured to limit the diffusion of the thermal flux from the probe into the wall. Figure for the abstract: Fig. 5

Description

Title of the invention: Device for detecting and characterizing a fouling deposit on a wall, comprising a thermal probe and at least one thermal guard surrounding it. Technical field

[0001] The present invention relates to the field of detecting fouling of a wall, and more precisely to a device for detecting and characterizing fouling of a wall.

[0002] The invention also relates to an assembly comprising such a device and a detection and characterization method implementing such an assembly.

[0003] The invention can be implemented for numerous industrial applications in which walls are subject to fouling phenomena, in particular in the industrial fields of food processing, chemistry, energy, and refrigeration. The invention can particularly be used for monitoring heat exchangers and fluid transport pipes.

[0004] In the context of the invention, the term "fouling" means any phenomenon generating an undesirable deposit of material on a wall, in particular on a wall subject to heat transfer. Prior art

[0005] The fouling phenomenon has an adverse impact on functionalities, such as heat exchange, the passage of fluids or the sanitary quality, in particular of storage tanks or fluid transport conduits. Heat exchanges can be disturbed by the presence of additional thermal resistance, the circulation of fluids can be hindered by fouling deposits, causing pressure losses, and the sanitary environment can be degraded, in particular due to the development of bacteria.

[0006] Several methods can be implemented to identify and characterize a fouling problem.

[0007] Global diagnostics on the efficiency of a heat transfer or on the pressure losses in a fluid pipe or equipment can be implemented for this purpose.

[0008] Preventive maintenance operations designed to prevent the accumulation of deposits on walls are also frequently used to avoid fouling problems, in particular to ensure the hygiene of food processing processes. However, these preventive operations prove expensive to implement, in particular due to production stoppages or the consumption of products such as than detergents.

[0009] The implementation of local fouling sensors adapted to detect fouling is also known but this requires specific adaptation for each use, which is impractical and expensive.

[0010] Local heat dissipation measuring devices, called thermal probes, are implemented to acquire information on the quality of local heat exchanges, and in particular to detect fouling in heat exchangers or in pipes. These devices are suitable for measuring local temperatures and / or local heat flows and can also provide information on local exchange coefficients. All of these measurements provide information on the performance and operation of the heat exchanger.

[0011] Such devices are described in particular in the following applications or patents.

[0012] Application WO 2009 / 153323 discloses the quantification of fouling by measuring the thermal resistance due to a fouling layer.

[0013] Application WO 2007 / 099240 describes the implementation of a fouling measuring device in a plate exchanger.

[0014] Patents EP 3339828 B1 and EP 3339836 B1 and application EP 3435067 A1 relate to the deployment of one or more thermal bi-probes to determine the presence of fouling even during variations in convection resistances in stationary or non-stationary regime.

[0015] Application EP 3771879 A1 relates to a multi-gap device for determining the thickness of fouling deposits.

[0016] [Fig.l] represents a thermal probe 1 according to the state of the art.

[0017] The thermal probe 1 comprises a deposit of resistive metal, such as nickel or platinum, the resistivity of which depends on the temperature according to a known law. This deposit of metal is shaped so as to form a resistor having adequate electrical impedance and heat dissipation characteristics. For example, it has a serpentine shape.

[0018] The resistor is arranged between two electrically insulating films, for example made of a polyimide such as Kapton®, to form the probe body 5. Advantageously, the body 5 is flexible.

[0019] The thermal probe 1 is preferably wired with four wires 6, 7: two wires 6 for supplying current to the resistor and two wires 7 for measuring the voltage across the resistor. The wires 7 make it possible to carry out a more precise measurement of the voltage across the probe by eliminating the wiring resistance because the current does not pass through these wires 7. However, wiring using three wires or two wires is also possible.

[0020] In the case of two-wire wiring, the current and voltage supply of the resistors are applied through a single wire and the return current and voltage also pass through a single wire. The resistance generated by the current flow can disturb the measurement.

[0021] In the case of three-wire wiring, the current and voltage supply are applied to the resistor by a single wire and the current and voltage return are made by two different wires. The measurement accuracy is improved compared to two-wire wiring.

[0022] A connector 8 provides the interface between the wires 6, 7 and a probe control device.

[0023] The probe is fixed, preferably glued, to a support on which the fouling deposit is to be detected, preferably on the surface opposite the surface on which fouling is expected.

[0024] The support may be flat or curved, in particular tubular in shape.

[0025] The thermal probe 1 can be used in a planar configuration, as illustrated in [Fig.l], or in a curved configuration, in particular annular, as illustrated in [Fig.2],

[0026] When an electric current flows through the probe resistor, it dissipates thermal power by the Joule effect. It is then possible, by measuring the current I and the potential difference U across the probe resistor, to know the dissipated thermal power P=UI and the electrical resistance R=U / I. The temperature of the probe can be deduced by the relationship between the resistivity and the temperature of the material used for the resistor.

[0027] When the probe is traversed by a current, the thermal dissipation P induces a temperature rise AT=Tp-T0 where Tp is the probe temperature with the dissipated power P and T0 the probe temperature at zero dissipated power. T0 is measured either directly by a preliminary measurement of the probe temperature with a sufficiently low thermal dissipation so that it does not significantly raise the temperature, or by increasing the thermal power in steps Pi and calculating for each of these steps the probe temperature Ti from the measured resistance. The temperature T0 at the power P=0 is deduced by linear regression of the points Ti(Pi) for P=0.

[0028] The thermal resistance of the probe environment is Rth=AT / P or dT / dP. This thermal resistance is the resultant of the series and parallel thermal resistances of the probe environment.

[0029] Among these environmental thermal resistances, two can be scalable: on the one hand, the convection thermal resistance of the well or of the heat source, typically a fluid flow whose exchange coefficient can evolve for example with the flow rate, and on the other hand an additional thermal resistance sus likely to become interposed between the support and the heat sink, typically due to a layer of fouling.

[0030] The interpretation of the information acquired by thermal probes is based on a model of heat diffusion in the probe's environment. In the simplest models, the assumption is made of unidirectional, or 1D, diffusion of the probe's heat flux.

[0031] In reality, the diffusion of the thermal flux from the probe is multidirectional, in particular due to the presence of the wall of the heat exchanger which, to ensure its function, is a good thermal conductor. The presence of a thermally resistant fouling layer increases the spread of the thermal flux.

[0032] [Fig. 3] schematically illustrates a thermal probe 1 arranged on the wall 2 of a conduit in which a fluid 3 circulates. The thermal probe 1 generates a thermal flux which is transmitted to the fluid through the wall. This thermal flux is shown schematically by an arrow in [Fig. 1]. In the absence of a fouling layer, the transmitted thermal flux diffuses little within the wall.

[0033] [Fig.4] represents for comparison the spread of the heat flow when a fouling layer 4 is present between the wall 2 and the fluid 3. The heat flow, represented by the arrow in [Fig.2], diffuses significantly in the wall.

[0034] Thus, a more precise analysis of the information collected by the thermal probe requires taking into account this thermal spreading phenomenon to reflect the increase in thermal resistance due to the development of a layer of fouling deposit.

[0035] There is therefore a need for a fouling detection and characterization device allowing more precise characterization of the fouling of a wall.

[0036] One aim of the invention is to at least partially meet this need. Statement of the invention

[0037] To this end, the invention relates to a device for detecting and characterizing fouling of a support wall, comprising:

[0038] - a thermal probe, configured to be fixed to the wall and comprising at least a resistor configured to generate a thermal flux towards the wall when the thermal probe is attached to the wall, and - at least one main thermal guard, configured to be fixed to the wall in contact with the thermal probe at least over a part of the perimeter of the latter, preferably over a part greater than 50%, 80%, 90% or equal to 100% of the perimeter of the latter, the at least one main thermal guard comprising at least one active and / or passive part configured to limit the diffusion of the flow thermal sensor in the wall.

[0039] The perimeter of the thermal probe corresponds to the side edges of the probe when it is fixed to the wall.

[0040] The invention therefore consists of implementing one or more main thermal guards surrounding with contact the thermal probe in its configuration fixed to a wall of a support, in order to compensate or at the very least limit, actively or passively, the diffusion of the thermal flux of the probe in the wall.

[0041] This advantageously makes it possible to make the heat flow between the thermal probe and the fluid essentially unidirectional, which makes the interpretation of the information delivered by the probe more reliable. This can also make it possible to obtain information on the nature of the heat exchanges in the environment of the probe.

[0042] Thus, the device according to the invention improves the capabilities of detecting the appearance of fouling and characterizing its development.

[0043] According to a first advantageous embodiment, the at least one main thermal guard comprises, as an active part, a resistor configured to generate a thermal flux towards the wall in the fixed configuration of the at least one main thermal guard.

[0044] According to a second advantageous embodiment, the at least one main thermal guard comprises, as a passive part, a thermally insulating material with a thermal conductivity less than or equal to 0.25 Wm *.K ', preferably being entirely constituted by the thermally insulating material.

[0045] A device according to the invention may comprise one or more of the following optional characteristics:

[0046] - the device is configured to be fixed to a tubular support and comprises two main thermal guards, the thermal probe and the main thermal guards being annular in shape in their fixed configuration;

[0047] - the thermal probe and the at least one main thermal guard are fixed to each other the other;

[0048] - the device further comprises at least one secondary thermal guard configured to be fixed to the wall in contact with the perimeter of the at least one main thermal guard, the at least one main thermal guard being arranged between the thermal probe and the at least one secondary thermal guard;

[0049] - the at least one secondary thermal guard comprises a resistor configured to generate a heat flow towards the wall when the at least one secondary thermal guard is attached to the wall.

[0050] a control device.

[0051] The invention also relates to an assembly for detecting and characterizing fouling of a support wall, comprising:

[0052] - a device according to the invention,

[0053] - an active control device electrically connected to the thermal probe and to the at least one active part of the at least one main thermal guard, and where appropriate secondary, the active control device being configured to supply current and to measure, and where appropriate regulate, the voltages and / or currents at the terminals of the thermal probe and where appropriate the active part of the at least one thermal guard.

[0054] The invention finally relates to a method for detecting and characterizing fouling of a support wall by means of an assembly according to the invention, comprising the steps consisting of: a. fix the detection and characterization device to the wall, preferably by gluing; b. supply current to the at least one resistor of the thermal probe and the active part of the at least one main thermal guard; c. measure the current and voltage across the thermal probe.

[0055] The method according to the invention may comprise one or more of the following optional characteristics:

[0056] - the power supply of the at least one main thermal guard is adapted so that the temperature of the main thermal guard is substantially equal to the temperature of the thermal probe;

[0057] - the method comprises after step c) a step d) consisting of measuring the current and the voltage across the at least one main thermal guard;

[0058] - measuring the current and voltage of the at least one main thermal guard is carried out at the terminals of a section of the main thermal guard, adjacent to the thermal probe, said section comprising less than 50%, less than 30% or less than 10% of the total surface area of ​​the thermal guard. Brief description of the drawings

[0059] [Fig-1] [Fig.l] is a perspective view of a thermal probe according to the state of art.

[0060] [Fig.2] [Fig.2] is a perspective view of a second thermal probe according to the state of the art.

[0061] [Fig.3] [Fig.3] is a diagram illustrating a heat transfer between a state-of-the-art thermal probe and a fluid through a wall.

[0062] [Fig.4] [Fig.4] is a diagram illustrating heat transfer between a state-of-the-art thermal probe and a fluid through a wall and a fouling layer.

[0063] [Fig.5] [Fig.5] is a perspective view of a detection and characterization device removal of fouling according to the invention.

[0064] [Fig.6] [Fig.6] represents a part of the device of [Fig.5].

[0065] [Fig.7] [Fig.7] represents an assembly comprising the device of [Fig.5].

[0066] [Fig.8] [Fig.8] schematically represents a heat transfer between a state-of-the-art thermal probe and a fluid through a wall.

[0067] [Fig.9] [Fig.9] schematically represents a heat transfer between a thermal probe according to the state of the art and a fluid through a wall and a fouling layer.

[0068] [Fig. 10] [Fig. 10] schematically represents a heat transfer between a device for detecting and characterizing fouling according to the invention and a fluid through a wall.

[0069] [Fig. 11] [Fig. 11] schematically represents a heat transfer between a device for detecting and characterizing fouling according to the invention and a fluid through a wall and a fouling layer. Detailed description

[0070] Throughout the present application, the terms "axial" and "radial" are to be understood with reference to a tubular support extending along a longitudinal central axis.

[0071] Figures 1 to 4 have already been described in the preamble and will not be commented on below. The same numerical references have been retained in the following to designate identical or similar elements.

[0072] A device 100 for detecting and characterizing fouling according to the invention, called a thermal guard probe, is shown in [Fig.5].

[0073] The device 100 comprises a thermal probe 1, which may be a thermal probe as described with reference to FIGS. 1 and 2.

[0074] In the illustrated embodiment, the thermal probe 1 is annular in shape and can be fixed to the circumference of a tube, preferably by gluing.

[0075] Two thermal guards 10, also each annular in shape, are arranged on either side of the thermal probe 1, preferably in contact with the lateral edges of the thermal probe. These lateral edges constitute the perimeter of the thermal probe.

[0076] Advantageously, the thermal guards are heating components and comprise a resistor comprising a resistive metal which may be identical to or different from that of the thermal probe 1. As for the thermal probe 1, the resistor of the thermal guards is arranged between two electrically insulating films. The thermal guards 10 may each comprise two wires 6 for supplying current to the resistor and two wires 7 for measuring the voltage across the resistor. However, either of the thermal guards 10 may also have a total of two or three wires, as shown in [Fig.6].

[0077] For each thermal guard 10, a connector 8 provides the interface between the wires 6, 7 and an active control device 20.

[0078] In the illustrated embodiment, the thermal guards 10 are active and allow thermal power to be dissipated by the Joule effect and their temperature to be measured. According to an alternative embodiment, the thermal guards are passive and do not include a resistor. They are then made of an insulating material having very low thermal conductivity. It is also possible for one thermal guard to be active and the other passive, or for each thermal guard to have an active part and a passive part, the active part being arranged between the passive part and the probe.

[0079] The surface area of ​​the thermal guards in contact with the support may be identical to that of the thermal probe 1 or different, in particular larger, for example greater than or equal to twice that of the thermal probe.

[0080] The thermal guards 10 can be fixed to the thermal probe 1 so as to form a solid assembly. Alternatively, the thermal probe 1 and the thermal guards 10 can be fixed to a support independently.

[0081] Preferably, the thermal guards 10 and the thermal probe 1 are fixed to the support by gluing, in particular by means of a glue or an adhesive film placed between the support and an inner face of the guards and the probe.

[0082] As shown in [Fig.7], each of the thermal guards 10 and the thermal probe 1 is connected to the active control device 20. The active control device 20 supplies the detection and characterization device 100 with direct electric current and allows the measurement of the voltage across the probe and the guards. The active control device 20 may comprise one, two, three or more current sources, each allowing or not the measurement of the intensity and the regulation of current or power of the components of the detection and characterization device 100. It may also comprise one, two, three or more voltage measurement means.

[0083] The active control device 20 must make it possible to carry out a sequence of measurements from which the fouling of the support wall can be deduced through the quantification of the AT / P value, i.e. the temperature variation of the thermal probe divided by the dissipated thermal power. This can be carried out with different levels of precision depending on the configuration of the active control device.

[0084] Thus, the configuration of the device 20 is advantageously chosen as a function of the number of heating elements, the measurement precision constraints and the cost of the electronic means used.

[0085] For optimal measurement quality, the control device 20 comprises as many current generators as there are heating components in the detection and characterization device 100 and it comprises the means necessary for measuring the currents and voltages of each of the heating components.

[0086] In the case of the illustrated embodiment comprising three heating components, according to a first configuration producing the most accurate measurements for the highest cost, the device 20 comprises three current generators each supplying power to the probe and the two thermal guards. It also comprises the means necessary for measuring the currents and voltages of each of the three components. The current of the probe is controlled so as to reproduce a power setpoint and the currents of the thermal guards are determined so that the temperatures of the thermal guards are equal to the temperature of the probe. Thus, the current applied to the probe is determined as a function of the power that it is desired to apply to the probe.

[0087] According to a second configuration producing less precise measurements at a lower cost compared to the first configuration, the device 20 comprises three current generators each supplying power to the probe and the two thermal guards. It also comprises the means necessary for measuring the currents and voltages of each of the three components. The current of the probe is controlled so as to reproduce a current setpoint and the currents of the thermal guards are determined so that the temperatures of the thermal guards are equal to the temperature of the probe. Thus, the current applied to the probe is directly chosen.

[0088] According to a third configuration producing less precise measurements for a lower cost compared to the second configuration, the device 20 comprises two current generators, one supplying the probe and the other supplying the two thermal guards in series. It also comprises the means necessary for measuring the two currents and two or three voltages, depending on whether the voltage of the thermal guards is measured at the terminals of the series connection of the two thermal guards or of each of the thermal guards. The current of the probe is controlled so as to reproduce a current setpoint and the current of the thermal guards is determined so that the temperatures of the thermal guards are equal to that of the probe.

[0089] According to a fourth configuration producing less precise measurements at a lower cost compared to the third configuration, the device 20 comprises a single current generator supplying the probe and the two thermal guards in series. It also comprises the means necessary for measuring the current and the voltage of the probe. The current of the probe is controlled so as to reproduce a current setpoint. The behavior of the thermal guards is dependent on the current applied to the series connection of the three components.

[0090] Preferably, the surface resistance of the thermal guards and that of the probe are identical so that the thermal fluxes are identical for the same current value applied to the guards and to the probe. However, slightly different surface resistances may be advantageous depending on the conditions of implementation of the invention, in particular to compensate for a particular physical behavior or an experimental bias. In this case, a calibration can advantageously be carried out to determine the optimal surface resistances.

[0091] Figures 8 and 9 are sectional views illustrating a thermal probe 1 arranged on a wall 2 of a tubular support in which a fluid 3 circulates. Figures 10 and 11 are sectional views illustrating a detection and characterization device 100 according to the invention arranged on the wall 2. In Figures 8 to 11, the arrows represent the thermal flows from the heating elements, i.e. the thermal probe 1 and the thermal guards 10. A fouling layer 4 is present in Figures 9 and 11.

[0092] In each of Figures 8 to 11, an isothermal line 11 represents a line along which the temperature is constant.

[0093] As can be seen in Figures 8 and 9, in the absence of a thermal guard, the isotherms 11 are not parallel to the thermal probe 1 over the entire width of the latter, measured in the axial direction. Heat transfers take place in the thickness of the wall of the tube 2 from the edges of the thermal probe: there is therefore an axial component of the heat transfers, that is to say a component parallel to the axial direction Z. These lateral heat transfers are greater in the presence of a fouling layer 4.

[0094] The isotherms are locally perpendicular to the heat transfer flow. When the isotherms are parallel to the thermal probe 1, the heat flow is radial and goes directly towards the fluid 3. When the isotherms have a non-zero radial component, the heat flow has an axial component in the wall of the tube 2, as is the case at the edges of the thermal probe 1.

[0095] The axial component of the heat flux impacts the quality of the measurements of the thermal probe 1. As this axial component depends on the thermal resistance between the probe and the fluid and therefore on the presence or absence of the fouling layer 4, the thermal resistance from the point of view of the thermal probe is complex to determine. In particular, the thermal path and its temporal variation are not known.

[0096] To compensate for the heat transfer in the wall 2 of the tubular support and to maintain the isotherms parallel to the thermal probe over the entire width of the probe between the probe and the fluid, thermal guards 10 are arranged on either side of the thermal probe 1 to form the device 100, as illustrated in Figures 10 and 11.

[0097] The thermal guards 10 are configured to dissipate thermal power by Joule effect and thus produce a thermal flux. The thermal guards 10 dissipate thermal power such that the axial component of the thermal flux is zero over the entire width of the thermal probe 1.

[0098] Thus, the thermal guards 10 have the effect of making the thermal flow between the probe 1 and the fluid 3 solely radial, by shifting the radial deformation of the isotherms 11 upstream and downstream of the probe 1 to the edges of the thermal guards 10, as visible in figures 10 and 11.

[0099] Since the heat flow between the thermal probe and the fluid is only radial, the thermal resistance measured between the probe and the fluid is then easily interpretable. This makes it possible to make the interpretation of the information delivered by the probe more reliable.

[0100] Preferably, the thermal power dissipated in the thermal guards 10 is controlled. To maintain the isotherms parallel to the thermal probe 1 between the latter and the fluid, the outer surface of the tubular support must constitute an isothermal line. Consequently, the probe 1 and the thermal guards 10 must be maintained substantially at the same temperature. However, possible differences in properties due to the structure of the probe and the guards or their attachment to the tubular support may play an important role. If these parameters are not negligible, their thermal characterization must be carried out to achieve an adequate correction, and the temperature of the thermal guards 10 to maintain the isotherms parallel under the probe may possibly be different from the temperature of the probe.

[0101] Preferably, the thermal probe 1 and the thermal guards 10 have an annular shape and cover the entire outer perimeter of the tubular support. If the device 100 does not cover the entire perimeter of the support, the heat flow between the probe and the fluid may not be purely radial even in the presence of the thermal guards.

[0102] As can be seen in Figures 10 and 11, the heat flow between the thermal guards 10 and the fluid 3 has an axial component at the edges of the thermal guards opposite the edges adjacent to the thermal probe 1. As a result, the thermal resistance from the point of view of the guards is lower than for the probe and, for a given density of heat flow under the resistor of the thermal guards, the temperature of the thermal guards tends to be lower towards their outer lateral edge compared to their temperature towards their lateral edge which is adjacent to the probe.

[0103] The temperature calculated with the total resistance of the resistor of the thermal guards is an average temperature over the entire surface of the thermal guards. The temperature of a thermal guard only in its part adjacent to the probe thermal is therefore not known precisely.

[0104] Thus, the thermal resistance of the resistor of the thermal guards is preferably measured only in a section of the resistor adjacent to the thermal probe. This makes it possible to know the temperature of the guards in the immediate vicinity of the thermal probe and, using this information, to better control the thermal power dissipated by the thermal guards so as to maintain the isotherms under the probe parallel to the latter.

[0105] To carry out the resistance measurement near the thermal probe, the voltage across a section of the thermal guard resistor is measured over only a portion of the width of the thermal guard starting from the edge of the guard adjacent to the probe. Preferably, this portion represents less than 50%, less than 30% or less than 10% of the total width of the thermal guard.

[0106] To carry out this resistance measurement, the thermal guard preferably comprises at least three wires, one wire being used for the current and voltage supply, one wire being used for the current measurement and one wire for the voltage measurement.

[0107] Although the invention is described in the context of measuring the fouling of a tubular support by means of an annular detection and characterization device, the same thermal guard principle is applicable for supports of flat or curved shape with thermal probes of flat shape, in particular rectangular or circular, or curved. Whatever the shape of the thermal probe, the thermal guard(s) are configured to be arranged around the thermal probe on the support to be characterized. The detection and characterization device according to the invention may comprise one, two, three, four or more thermal guards arranged around the peripheral edge of the thermal probe.

[0108] The device according to the invention may also comprise secondary thermal guards configured to be arranged around the peripheral edges of the main thermal guards surrounding the thermal probe, i.e. in contact with the perimeter of the main thermal guards. Other thermal guards may also be provided to be arranged around the peripheral edges of secondary thermal guards to form additional thermal guards. The addition of secondary thermal guards advantageously makes it possible to improve the quality of the compensation of the thermal flux of the thermal probe.

[0109] The invention as described comprises the implementation of active thermal guards, controlled by the control device to improve the heat flow compensation. It is also possible to implement passive thermal guards. The passive guards are configured to be arranged all around the thermal probe, like the active thermal guards, and comprise a thermally insulating material having a very low thermal conductivity to limit the diffusion of the heat flux in the axial direction, for example polytetrafluoroethylene (PTFE). Preferably this thermal conductivity is less than 0.25 Wm '.K ', 0.1 Wm '.K ', 0.05 Wm >.K 1 or 0.01 W.mhK1.

[0110] Other variants and improvements may be envisaged without departing from the scope of the invention.

Claims

Claims

1. Device (100) for detecting and characterizing fouling of a support wall (3), comprising: - a thermal probe (1) configured to be fixed to the wall and comprising at least one resistor configured to generate a thermal flux towards the wall when the thermal probe is fixed to the wall, and - at least one main thermal guard (10) configured to be fixed to the wall in contact with the thermal probe at least over a portion of the perimeter of the latter, preferably over a portion greater than or equal to 50%, 80%, 90% or equal to 100% of the perimeter of the latter, the at least one main thermal guard comprising at least one active and / or passive portion configured to limit the diffusion of the thermal flux of the probe in the wall, the device being configured to be fixed to a tubular support and comprising two main thermal guards,the thermal probe and the main thermal guards being annular in shape in their fixed configuration.,

2. Device according to claim 1, the at least one main thermal guard comprising, as an active part, a resistor configured to generate a thermal flux towards the wall in the fixed configuration of the at least one main thermal guard.

3. Device according to claim 1, the at least one main thermal guard comprising, as passive part, a thermally insulating material with thermal conductivity less than or equal to 0.25 W.m'.K1.

4. Device according to one of the preceding claims, the thermal probe and the at least one main thermal guard being fixed to each other.

5. Device according to one of the preceding claims, further comprising at least one secondary thermal guard configured to be fixed to the wall in contact with the perimeter of the at least one main thermal guard, the at least one main thermal guard being arranged between the thermal probe and the at least one secondary thermal guard.

6. Assembly for detecting and characterizing fouling of a support wall, comprising: - a device according to one of the preceding claims, - an active control device (20) electrically connected to the thermal probe and to the at least one active part of the at least one main thermal guard, and where appropriate secondary, the active control device being configured to supply current and to measure, and where appropriate regulate, the voltages and / or currents at the terminals of the thermal probe and where appropriate the active part of the at least one thermal guard.

7. Method for detecting and characterizing fouling of a support wall by means of an assembly according to claim 6, comprising the steps of: a. fixing the detection and characterization device on the wall, preferably by gluing; b. supplying current to the at least one resistor of the thermal probe and the active part of the at least one main thermal guard; c. measuring the current and the voltage across the terminals of the thermal probe.

8. Method according to the preceding claim, according to which the power supply to the at least one main thermal guard is adapted so that the temperature of the main thermal guard is substantially equal to the temperature of the thermal probe.

9. Method according to one of claims 7 or 8, comprising after step c), a step d) consisting of measuring the current and the voltage at the terminals of the at least one main thermal guard.

10. Method according to one of claims 7 to 9, according to which the measurement of the current and the voltage of the at least one main thermal guard is carried out at the terminals of a section of the main thermal guard, adjacent to the thermal probe, said section comprising less than 50%, less than 30% or less than 10% of the total surface area of ​​the thermal guard.

Images