DE102010030075A1 - Device for detecting a temperature of a fluid medium - Google Patents

Abstract

A device (110) for detecting a temperature of a fluid medium is proposed. This comprises at least one temperature sensor (114), which is set up to be introduced into the fluid medium. The temperature sensor (114) has a sensor body (124) and a measuring head (128) projecting into the fluid medium. At least one sensor element (130) for detecting a temperature is accommodated in the measuring head (128). The sensor element (130) is received in the measuring head (128) such that it is at least largely thermally decoupled from the sensor body (124).

Description

State of the art

Temperature is an important measure in many technical applications and processes, which must be detected by means of appropriate devices. For example, the temperature plays an important role in a control and / or regulation in process engineering, component protection or similar applications. Accordingly, the prior art discloses numerous sensors for detecting a temperature of fluid media, such as gases or liquids. In this regard, reference may be made in this regard to Robert Bosch GmbH: Sensors in motor vehicles, Edition 2007, pages 96-105. The measurement principles described there for detecting the temperature can in principle also be used in the context of the present invention. In particular, an electrical temperature measurement can take place, for example by means of thermocouples, which exploit the Seebeck effect. Alternatively or additionally, resistance temperature sensors or other types of temperature sensors can also be used.

Although the temperature measurement, in particular the electrical temperature measurement, for example by means of thermocouples, has provided a suitable measuring principle for the detection of temperatures for over 100 years, the individual measurement requirement of technical applications remains in many cases a great challenge, in particular with regard to the measurement accuracy, the measurement dynamics, the upper temperature limits and / or long-term stability.

For measuring the temperature of flowing fluid media temperature sensors are often used, which are usually configured as a rod-shaped sensor and are brought into contact with the fluid medium. Through various mechanisms of heat transfer (for example, convection, heat conduction, or radiation) thermal energy is supplied to the sensor and / or dissipated therefrom, whereby the sensor assumes a temperature similar to the fluid temperature. Within the probe, a sensor is typically placed, such as a thermocouple, a negative temperature coefficient (NTC) resistor, a positive temperature coefficient (PTC) resistor, a resistor, or the like. Due to its thermophysical properties, the sensor generates an electrical signal associated with the temperature. This is further processed in a connected electronics.

Out US 2007/0195857 A1 For example, a temperature sensor and a method of manufacturing the same are known. The temperature sensor has a fixation, by means of which the sensor can be introduced vertically into a housing of a flow tube. Furthermore, the sensor has a sensor head with a multiplicity of ribs arranged rotationally symmetrically about a sensor axis for enlarging the surface of the sensor head for the purpose of improving a heat transfer between the temperature sensor and the fluid medium.

Despite the known from the prior art improvements of temperature sensors in terms of their accuracy, there is still a need for optimization of these temperature sensors, in particular with regard to their accuracy and their dynamics, for example in rapid temperature changes.

Disclosure of the invention

Accordingly, an apparatus for detecting a temperature of a fluid medium is proposed, which addresses the challenges described above and in particular provides improved accuracy in terms of temperature measurement and improved dynamics. The fluid medium can rest or flow. Hereinafter, without limitation of other possible embodiments, it is assumed that it is a flowing fluid medium.

The device is designed to detect a temperature of the fluid medium, for example a liquid or a gas, in particular an exhaust gas of an internal combustion engine. The device comprises at least one temperature sensor which is adapted to be introduced into the fluid medium. For this purpose, the temperature sensor may for example have at least one fastening device for fastening in a tube wall of a flow tube of the fluid medium. This may be, for example, one or more threads, by means of which the temperature sensor or a part of the temperature sensor can be screwed into the pipe wall. The fastening device is preferably designed such that the attachment of the temperature sensor in the pipe wall is media-tight and / or pressure-tight. The introduction can preferably take place in such a way that the temperature sensor is introduced substantially perpendicularly to the tube wall, ie with a deviation of preferably less than 20 °, in particular less than 10 ° and particularly preferably less than 5 ° to the tube wall, for example to an axis of the flow tube.

The temperature sensor may be configured, for example, as a measuring finger, which projects completely or partially into the flow of the fluid medium. The temperature sensor has a Sensor body and a projecting into the fluid medium measuring head. For example, the sensor body may be designed to be substantially cylindrical and into the measuring head ends, or the measuring head may be applied to the sensor body at the end facing the fluid medium. At least one sensor element for detecting a temperature of the fluid medium is received in the measuring head. For example, the sensor element may be one or more of the temperature sensors described above, such as an electrical sensor element, such as a temperature sensing resistor, a negative temperature coefficient resistor, a positive temperature coefficient resistor, a thermocouple (eg, a Seebeck effect based thermocouple) ) or another type of sensor element. Alternatively or additionally, a plurality of sensor elements may also be accommodated, for example a plurality of sensor elements in the measuring head and / or also at other locations within the device. In addition to the at least one sensor element for detecting the temperature, further sensor elements can be accommodated, for example one or more sensor elements for detecting a pressure of the fluid medium. Various configurations are possible.

The sensor element is received in the measuring head in such a way that it is at least largely decoupled thermally from the sensor body. This means that the heat transfer from the sensor element to the sensor body should be smaller than within a same transmission path within the sensor body itself. Furthermore, the heat transfer from the sensor element to the sensor body can be configured such that it is less than a heat transfer from the sensor element to the surrounding fluid Medium. Under a heat transfer is generally a heat transfer in one direction or in the reverse direction or bidirectional to understand. In particular, the at least extensive thermal decoupling can be designed such that a heat transfer in the axial direction, d. H. along an axis of an elongated temperature sensor, at least at the transition between the measuring head and the sensor body, is less than a heat transfer in the radial direction, that is perpendicular to the axis of the temperature sensor.

The thermal decoupling of the sensor element from the sensor body can be done in various ways. In particular, at least one insulating element arranged between the sensor element and the sensor body can be provided. This insulating element can be designed in one piece or also in several parts and is designed to suppress a heat transfer between the sensor element and the sensor body. By way of example, the suppression can be configured by at least a factor of 2, preferably by at least a factor of 10 or even by at least a factor of 100, compared with a configuration without such an insulation element. The insulation element may comprise, for example, an element with low thermal conductivity, in particular an insulation layer and / or an insulation sleeve. Alternatively or additionally, the insulation element may also comprise one or more gaps, which may be filled with a gas (gas gap), for example an air gap and / or a gap filled with an inert gas.

The measuring head may be at least partially surrounded by a thermally conductive protective sleeve. Under a protective sleeve is an element to understand, which is designed substantially sleeve-shaped, which, however, may also have one or more openings and which ensures a protective effect against, for example, mechanical loads and / or media influences from the outside. The protective sleeve can be made for example of a thermally conductive material. For example, this may be a plastic material and / or a metallic material. The protective sleeve can in particular be made thin-walled, for example with a wall thickness of less than 1 mm. In particular, the wall thickness may be less than a wall thickness of a jacket of the sensor body. As thermally conductive materials, for example, metals, in particular metal sheets may be used, or thermally conductive plastics, such as plastics, which are filled to improve the thermal conductivity with a thermally conductive filler such as a metallic filler and / or a ceramic filler. However unfolded plastics can also be used in principle, in particular if the wall thickness of the protective sleeve is made as small as possible.

The measuring head can in particular have a smaller diameter in comparison to the sensor body. In the case of a round configuration of the measuring head and / or of the sensor body, a diameter is to be understood as the actual diameter, for example perpendicular to an axis of the temperature sensor. If a non-round configuration is provided, a dimension which characterizes the extent in the lateral direction, for example perpendicular to the axis of the temperature sensor, takes the place of the actual diameter. For example, this may be a characteristic edge length, a diagonal or the like. For example, at the transition between the sensor body and the measuring head, a shoulder may occur in which the diameter of the temperature sensor is reduced. Other embodiments are possible. In this way, the thermal coupling between the sensor element and the surrounding fluid medium can be further increased.

In particular in the region of the sensor element in the radial direction to improve heat exchange between the sensor element and the fluid medium, that is, for example, in a direction perpendicular to an axis of the sensor element, the measuring head can be configured at least largely gap-free. This may mean, for example, that no gaps having a gap width of more than 500 μm, preferably no gaps of more than 100 μm, occur in this radial direction. This gap-free configuration can be configured for example by a positive connection and / or by a material connection in the region of the measuring head. For example, the sensor element may be incorporated in a form-fitting manner in further elements of the measuring head, for example in a form-fitting manner in the protective sleeve and / or in a form-fitting manner in a coupling element to be described in more detail below. This positive connection can be effected, for example, with the aid of a melt bead, via which the sensor element is introduced substantially without gaps into the measuring head, for example into the coupling element and / or into the protective sleeve. Various embodiments will be described in more detail below. Alternatively or additionally, a positive insertion can also take place, for example by using a press fit. Thus, for example, the coupling element and / or the sensor element can be accommodated by a positive fit in the measuring head, for example by a press fit in the protective sleeve and / or by a positive connection and / or by at least one filler material (for example, a thermal grease and / or a liquid, for example a liquid metal).

As already mentioned several times above, the sensor element can in particular be accommodated at least partially in at least one coupling element, wherein the coupling element can be designed to effect a heat exchange between the sensor element and the fluid medium (which can surround both directions of transmission) compared to a heat exchange between the sensor element Sensor element and the sensor body to favor. This can be done, for example, by using a coupling element with a particularly high thermal conductivity at least in the radial direction, that is to say in the direction of immediate exchange with the fluid medium. The coupling element may for example be designed as a sleeve or comprise a sleeve. The coupling element may in particular be configured thermally decoupled from the sensor body, wherein, for example, the at least one optional insulation element described above and / or another type of insulation element of the described embodiments may be used. For example, the coupling element can also be separated from the sensor body by at least one gas gap, for example an air gap, and / or by one or more thermally insulating material layers.

In particular, the coupling element may comprise a material having one or more of the following properties: a material having a density less than the average density of the materials of the sensor body in an area of the sensor body adjacent to the measuring head; a material having a lower specific heat capacity than the average specific heat capacity of the materials of the sensor body in a region of the sensor body adjacent to the measuring head; a material with a higher thermal conductivity than the average thermal conductivity of the materials of the sensor body in an adjacent to the measuring head region of the sensor body. Various other embodiments of the coupling element are possible or combinations of the above or other options.

The coupling element can in particular be selected from one or more of the following coupling elements: a sleeve at least partially enclosing the sensor element of a ceramic material, in particular a ceramic material with high thermal conductivity and / or with a high temperature code; a sleeve at least partially surrounding the sensor element made of a plastic material, in particular a plastic material with high thermal conductivity; a sleeve at least partially surrounding the sensor element of a metallic material, such as an iron material, an aluminum material or a copper material; a melting bead at least partially enclosing the sensor element, in particular a melt bead of a plastic material and / or a melt bead of a metallic material and / or a melt bead of a glass material (wherein the melt bead in all cases can also be part of the sensor element itself); a filling material in a space between the sensor element and the measuring head at least partially enclosing protective sleeve.

In order to improve the thermal coupling and to improve the heat transfer between the measuring head or the sensor element and the surrounding fluid medium, furthermore, the surface facing the fluid medium, for example a flow of the fluid medium, can have at least one turbulator element. Under In this case, a turbulator element is to be understood as an element which is set up in order to effect a change from a laminar flow into a turbulent flow at the surface in the case of a temperature sensor introduced into a flow of the fluid medium. By inducing turbulence, in contrast to conventional laminar flow around the temperature sensor, mixing of surfaces of near layers of the fluid medium with layers of the fluid medium removed from the surface is effected. As a result, an improved temperature exchange of the fluid medium with the measuring head and thus with the sensor element is effected, which overall significantly improves the connection and the dynamics of the measurement. From US 2007/0195857 A1 On the other hand, known ribs, which are aligned parallel to the flow of the fluid medium when the sensor described therein is introduced vertically into the flow of the fluid medium, do not cause such turbulence formation and thus no corresponding mixing and thus do not have the described advantages.

In particular, the turbulator element may comprise a microstructure which comprises a plurality of structural elements, that is, elevations or depressions in the surface. The structural depth of the structural elements, that is to say a maximum elevation or minimum depression of the structural elements, can preferably not exceed 50 μm, particularly preferably 10 μm. An average structural depth of the structural elements can be in particular 0.5 to 5 μm, preferably 1 to 2 μm.

The turbulator element may be configured in various ways to effect a turbulent flow and / or an early transition from a laminar boundary layer flow to a turbulent boundary layer flow. For example, the turbulator element may be selected from: elevations, wherein at least one of the elevations is impinged by the fluid medium in such a way that the elevation acts as a turbulator element; Wells, wherein at least one of the wells is flowed by the fluid medium in such a way that the depression acts as a turbulator element. The turbulator element can be selected, for example, from: a wire, in particular a tripwire, preferably a wire basket with a plurality of tripping wires, which can completely or partially surround the measuring head, for example; a needle, in particular a conically (blunt or pointed) or rounded tapered needle, in particular a plurality of needle-shaped or pointed elevations; a wedge-shaped elongate elevation, that is to say an elevation with a sharp edge extending into the fluid medium, which is overflowed by the fluid medium, in particular a plurality of wedge-shaped elevations aligned substantially axially parallel; an elongated recess, in particular a groove or groove with a rounded and / or angular profile; a point-shaped elevation, in particular a survey with a round or angular cross-section, in particular a plurality of punctiform elevations; a punctiform depression, in particular a depression with a round or angular cross-section, in particular a plurality of punctiform depressions or a golf ball pattern; a grid with several intersecting elevations; a grid having a plurality of intersecting recesses; a honeycomb pattern; a knurl, in particular a knurl with paraxial grooves, a right-hand knurl, a left-hand knurl, a left-right knurl or a knurled knurl; a tear-off edge, in particular a tear-off edge with an angle of at least 30 °; a diamond-shaped elevation; a diamond-shaped depression; a pyramid. In particular, the turbulator element may comprise a grid having at least two, preferably a plurality of, mutually crossing elongated structural elements. For example, a first type of structural elements may be provided, which is aligned in one direction elongated, and a second type, which is aligned in a second direction, so that the first and the second type of structural elements intersect at a plurality of crossing points.

The measuring head may in particular have a substantially rounded shape. Alternatively or additionally, however, the measuring head may also have a cylindrical and / or stepped shape. If the measuring head is substantially rounded, then the turbulator element can be arranged, for example, in the region of the rounding off. In particular, a plurality of turbulator elements may be provided. For example, a plurality of turbulator elements may be arranged with a symmetry to an axis of the temperature sensor. For example, this may be an N-fold rotational symmetry about the axis of the temperature sensor. The turbulator element can in particular be designed as an interrupted turbulator element and comprise a plurality of structural elements. The structural elements can in particular be arranged such that the inflowing fluid medium experiences a repeated stall at the structural elements.

Brief description of the figures

Embodiments of the invention are illustrated in the figures and are explained in more detail in the following description.

In detail show:

1 different installation situations of common temperature sensors;

2A to 2C Flow conditions and thermal conditions above a surface overflowed by a fluid medium;

3 various mechanisms of heat exchange in the area of a temperature sensor;

4 Heat exchange of a sensor element of a temperature sensor with the environment;

5A to 5H various embodiments of a measuring head of a temperature sensor according to the invention;

6A to 6G various embodiments of a measuring head of a temperature sensor with a knurl;

7 a typical construction of a measuring head of a temperature sensor with a sensor element;

8A and 8B different views of an embodiment of a temperature sensor according to the invention; and

9 and 10 further embodiments of a temperature sensor according to the invention.

embodiments

In the following, various embodiments of devices 110 for detecting a temperature of a fluid medium. For example, the fluid medium may be a gas passing through a flow tube 112 according to 1 flows. For example, this may be an exhaust gas of an internal combustion engine. Here are in 1 two different installation situations of a temperature sensor 114 the device according to the invention 110 into the flow tube 112 shown. With the reference number 116 is the flow direction of the fluid medium, ie the direction of the flow and / or the direction of the main mass transport to fluid medium through the flow tube 112 , shown. It is shown in 1 once an angled designed temperature sensor 114 which is just in the flow tube 112 is installed (left temperature sensor 114 in 1 ) and a just designed temperature sensor 114 (right-hand illustration), which at a curvature of the flow tube 112 against the main flow direction 116 into the flow tube 112 can be installed.

The temperature sensors 114 are mostly, as in 1 represented, rod-shaped and are, for example, on the in 1 Illustrated manners brought into contact with the fluid medium. Through various mechanisms of heat transfer, such as convection and / or heat conduction and / or radiation, the temperature sensor 114 Energy supplied or dissipated energy from this, whereby it assumes a temperature similar to the fluid temperature. Inside the temperature sensor 114 in each case a sensor element is arranged (in 1 not detectable), which may be, for example, a thermocouple, an NTC (negative temperature coefficient resistor), a PTC (positive temperature coefficient resistor), a common thermal resistor, or a similar sensor element, the sensor element due to its thermophysical properties the temperature associated signal, such as an electrical signal can generate. This is preferably further processed in an optionally connected electronics, which in 1 not shown and which also part of the device 110 may be or which may also be configured as external electronics. In the 1 illustrated installation options of the temperature sensor 114 are used, for example, in plant construction. The plants are usually operated in quasi-stationary operating conditions, and the temperatures hardly change, and if changes should occur, they take place relatively slowly. In contrast, the measurement of the temperature of exhaust gases, for example, from thermal piston or turbomachinery, for example, for reasons of component protection usually very high demands on the measurement and thus also on the temperature sensor 114 , The two main demands of such temperature sensors 114 , For example, for use in automotive technology, usually consist in a high measurement accuracy, ie a small deviation between the actual fluid temperature and the temperature sensor 114 displayed temperature, as well as in a high dynamics. High dynamics in this context means the possibility of rapid changes in the gas temperature with the temperature sensor 114 to resolve with the least possible delay and high accuracy. In addition, in many cases a free choice of installation position or installation position is desired. From a technical point of view, directed installations such as those in 1 shown curved execution undesirable. Mostly an installation is perpendicular to a pipe wall 118 of the flow tube 112 at installation location in straight version of the temperature sensor 114 required or desired.

Inaccuracies in the temperature measurement and low dynamics lead to a high Application effort or even to exclude the measurement process for certain applications. By suitable design measures on the temperature sensor 114 can be increased according to the invention, the accuracy and dynamics. This is intended in the context of the embodiments of inventive devices shown below 110 and temperature sensor 114 be explained.

In exhaust systems, due to the high temperatures, there is usually an increased energy exchange through convection and radiation between the exhaust system and the temperature sensor installed therein 114 and the environment. The heat output of the hot temperature sensor 114 as a sensor to the colder environment or in the reverse case, the heat absorption from the hotter environment leads to a systemic deviation of the device 110 displayed temperature of the actual fluid temperature. Likewise, this heat dissipation or heat absorption leads to a delayed response of the device 110 , By deliberately influencing the energy transport, the heat emission and / or the heat absorption to the environment or from the environment can be reduced and the heat absorption or heat emission to the actual sensor element can be increased. This increases both the measurement accuracy and the dynamics of the temperature measurement.

In 3 are schematic the installation situation of a temperature sensor 114 and the occurring energy flows shown. Shown here is an embodiment of a temperature sensor 114 , which one at a execution 120 with fixation 122 , For example, a screw, preferably with sealing effect, through a pipe wall 118 a flow tube 112 performed sensor body 124 having. The sensor body 124 is in this embodiment substantially perpendicular to a tube axis 126 the flow tube and / or substantially perpendicular to the pipe wall 118 aligned. The sensor body 124 flows into a rounded measuring head 128 , which in this embodiment, seamlessly to the sensor body 124 connects and is integrally formed with this. However, other embodiments are possible, for example, embodiments in which the measuring head 128 from the sensor body 124 discontinued is designed. In the measuring head 128 is a sensor element 130 recorded to detect the temperature of the fluid. The sensor element is shown in an enlarged view in FIG 4 shown.

The energy flows that occur in the heat transfer are in the 3 and 4 each characterized by arrows. The reference numerals denote 132 Heat transfers by convection, the reference numbers 134 Heat transfer by conduction, and the reference numerals 136 Heat transfer by radiation. Furthermore, in 3 denotes different temperatures, namely with T _U the temperature of the environment, with T _{W, a} the temperature of the pipe wall 118 on the outside, ie the side facing away from the fluid medium, with T _{W, i} the temperature on the inside of the pipe wall 118 , So on the side facing the fluid medium, with T _A, the temperature of the exhaust gas or the fluid medium, with T _K, the temperature of the temperature sensor 114 in the area of a cable outlet and with T _S the temperature of the temperature sensor 114 at its tip, in the area of the measuring head 128 ,

If the exhaust gas temperature is higher than the sensor temperature or T _S , then heat transfer usually takes place by convection of the exhaust gas in the temperature sensor 114 over the entire outer surface of the temperature sensor protruding into the exhaust gas 114 instead of. In the area of fixing the temperature sensor 114 in the pipe wall 118 this has a good thermal contact with the pipe wall 118 , Due to heat conduction there is a heat flow into the pipe wall 118 instead of. Since the wall temperature is usually lower than the exhaust gas temperature, heat is generated by conduction in the axial direction of the temperature sensor 114 transported. There is also at most a radiation heat exchange between the hotter lateral surface of the temperature sensor and the colder inner wall of the flow tube 112 instead of (see a) in 3 ). The part of the temperature sensor protruding into the environment 114 usually experiences a convective cooling by the lower ambient temperature and a supply of heat by radiation exchange with the hotter outer wall of the flow tube 112 (see b) in 3 ). Additional external radiation sources (eg hot surfaces of an exhaust gas turbocharger, a catalytic converter or the like) may additionally carry energy (see c) in FIG 3 ). By heat conduction continues to find an energy transport in the direction of an axis 138 of the temperature sensor 114 towards the cable outlet instead.

In the case of a quick change to cold exhaust gas, heat transfer occurs by convection of temperature sensor 114 to the fluid medium or the exhaust gas instead, usually over the entire outer surface of the projecting into the exhaust temperature sensor 114 , In the field of attachment or fixation 122 of the temperature sensor 114 in the pipe wall 118 heat flows from the still hot pipe wall 118 into the sensor body 124 of the temperature sensor 114 , which may also be designed as a shaft, in the direction of the position of the sensor element 130 to. It also finds radiation heat exchange between the colder surface of the temperature sensor and the now hotter inner wall of the Exhaust pipe instead. The part of the temperature sensor protruding into the environment 114 further experiences convective cooling by the lower ambient temperature and a supply of heat by radiation exchange with the hotter outer wall of the flow tube 112 , Additional external radiation sources (for example, hot surfaces of exhaust gas turbochargers, catalysts or the like) may additionally carry energy. Through the heat conduction continues to find an energy transport in the direction of the axis 138 of the temperature sensor 114 towards the cable outlet instead.

In 4 are schematically the energy flows in the area of the sensitive tip of the temperature sensor 114 shown. The actual sensor element 130 experiences a supply and / or dissipation of heat due to the environmental conditions and the constructive connection of the sensor element 130 to the temperature sensor 114 to be influenced. Once a stationary state is reached, the incoming and outgoing energy flows are in equilibrium, and the sensor element 130 keeps a constant temperature. This usually corresponds to that by an evaluation of the device 110 determined temperature. However, it is not identical to the gas temperature, which causes a system-related measurement error.

To increase the measuring accuracy and the dynamics of the device 110 In general, the principle that applies the energy supply to the sensor element 130 or the energy dissipation from the sensor element 130 in the radial direction, that is perpendicular to the axis 138 , must be as fast as possible, whereas the energy supply to the sensor element 130 or the energy dissipation from the sensor element 130 in the axial direction, ie parallel to the axis 138 of the temperature sensor 114 , must be stopped as possible. This ensures that the sensor element 130 a change in temperature reproduces as quickly as possible and the temperature of the sensor element 130 deviates as little as possible from the temperature of the fluid medium. The minimization of the energy flows in the axial direction can be achieved, for example, by a thermal decoupling of the sensor element 130 or the measuring head 128 from the sensor body 124 For example, from the shaft of the temperature sensor 114 be technically realized via an air gap or a use of a material with low thermal conductivity. This will be explained in more detail below. In the radial direction, however, is a good thermal connection of the sensor element 130 to the fluid medium and, for example, a wall of the temperature sensor 114 or to realize a minimization of air gaps. To increase the radial energy transport of the ideal thermally from the sensor body 124 decoupled tip or the measuring head 128 of the temperature sensor 114 contributes among other things to a minimization of the mass and the specific heat capacity of the system, in particular of the measuring head 128 , and maximizing the heat transfer coefficient and the area available for heat transfer.

• A) Thermische Entkopplung des Sensorelements 130 vom Fühlerkörper 128, beispielsweise durch – Luftspaltisolierung und/oder – ein Isolierelement, beispielsweise eine Materialschicht mit geringer Wärmeleitfähigkeit und/oder – eine geringe Wandstärke der das Sensorelement 130 umgebenden Schutzhülse 140; und/oder
• B) Minimierung der Masse und/oder spezifischen Wärmekapazität des Temperaturfühlers 114, insbesondere des Messkopfs 128, und/oder eine Verbesserung des Energietransports im Feststoff des Temperaturfühlers 114, insbesondere des Messkopfs 128, beispielsweise durch: – Verringerung der Abmessungen des Sensorelements 130 und/oder des Temperaturfühlers 114 im Bereich des Einbauorts des Sensorelements 130 und/oder – Einsatz von Werkstoffen im Nahbereich des Sensorelements mit geringer Dichte und/oder geringer spezifischer Wärmekapazität, jedoch mit hoher Wärmeleitfähigkeit; und/oder
• C) Maximierung des Wärmeübergangs zwischen dem Sensorelement 130 und dem fluiden Medium, beispielsweise durch Verbesserung der thermischen Ankopplung an das fluide Medium, durch Erhöhung des Wärmeübergangskoeffizienten und/oder durch Erhöhung einer Oberfläche 142 des Temperaturfühlers 114 im Bereich des Messkopfs 128, beispielsweise durch: C1) Vergrößerung der zur Wärmeübertragung zur Verfügung stehenden Oberfläche 132, wie beispielsweise in US 2007/0195857 A1 beschrieben, und/oder C2) Vergrößerung des Wärmeübergangskoeffizienten durch Störung des Aufbaus einer laminaren hydrodynamischen und thermischen Grenzschicht durch Verwendung eines oder mehrerer Turbulatorelemente auf dem Temperaturfühler 114, insbesondere dem Messkopf 128.

The constructive design of the temperature sensor can afford the following contributions.

• A) Thermal decoupling of the sensor element 130 from the sensor body 128 , For example by - air gap insulation and / or - an insulating element, for example, a material layer with low thermal conductivity and / or - a small wall thickness of the sensor element 130 surrounding protective sleeve 140 ; and or
• B) Minimization of the mass and / or specific heat capacity of the temperature sensor 114 , in particular the measuring head 128 , and / or an improvement of the energy transport in the solid of the temperature sensor 114 , in particular the measuring head 128 by, for example: - reducing the dimensions of the sensor element 130 and / or the temperature sensor 114 in the region of the installation location of the sensor element 130 and / or - use of materials in the vicinity of the sensor element with low density and / or low specific heat capacity, but with high thermal conductivity; and or
• C) maximizing the heat transfer between the sensor element 130 and the fluid medium, for example by improving the thermal coupling to the fluid medium, by increasing the heat transfer coefficient and / or by increasing a surface 142 of the temperature sensor 114 in the area of the measuring head 128 , for example by: C1) enlargement of the surface available for heat transfer 132 , such as in US 2007/0195857 A1 described, and / or C2) increase the heat transfer coefficient by disrupting the structure of a laminar hydrodynamic and thermal boundary layer by using one or more turbulator elements on the temperature sensor 114 , in particular the measuring head 128 ,

The measures to influence the boundary layer according to C2) usually aim at two effects. On the one hand, the transfer to a turbulent boundary layer should take place as early as possible, ie after a short run. Serve turbulator elements, which are exemplified in the 5A to 5H and 6A to 6G are shown and there with the reference number 144 are designated. These turbulator elements 144 are each on the surface 142 of the measuring head 128 applied or incorporated into and include various types of structural elements 146 So elevations from the surface 142 and / or depressions in the surface 142 , For example, shows 5A a turbulator element 144 in the form of a wire basket with tripping wires, 5B an embodiment of a turbulator element 144 in the form of protruding ribs with an additional wire basket over the rounding of the measuring head 128 . 5C an embodiment with a plurality of needle-shaped structural elements 146 . 5D an embodiment with elevations, in the form of sharp edges parallel to the axis 138 of the temperature sensor 114 run and act as "stumbling blocks", 5E an embodiment with demolition edges by angular shape of the measuring head 128 . 5F an embodiment with grooves with a round cross-section or polygonal cross-section in an otherwise rounded measuring head 128 . 5G an embodiment with punctiform, circular depressions (golf ball pattern) in an otherwise rounded measuring head 128 , and 5H an embodiment with a grid of crossed grooves, which, for example, as "negative" of the wire basket according to 5A can be designed. Alternatively or additionally, the structural elements 146 of the turbulator element 144 also include, for example, diamonds, needles, pyramids, other types of tear-off edges or generally angular shapes.

The measures with the at least one turbulator element 144 For example, in the devices 110 according to the 1 . 3 and 4 to get integrated. The measures to influence the boundary layer usually aim at two effects. On the one hand, the transfer to a turbulent boundary layer should take place as early as possible, ie after a short run. The turbulator elements serve this purpose 144 which may include, for example, small obstacles, depressions, surface roughness or the like. On the other hand, the boundary layer structure should be repeated as constantly as possible, since the heat transfer here is particularly high. This is achieved, for example, by correspondingly interrupted ribs, needles or other forms, each representing a new flow of a separate body with a corresponding boundary layer structure.

The principle of the boundary layer influencing is in the 2A to 2C explained. 2A shows the formation of a fluid-dynamic boundary layer at overflow of a surface 142 in the form of a flat plate. The fluid adheres to the solid wall. With increasing run length, starting at a plate leading edge 148 , the flow rate increases continuously up to the value in the free flow. It forms a laminar boundary layer 150 out, which increases with increasing run length. Within this laminar boundary layer 150 a layer flow prevails, ie it finds - in contrast to the mostly turbulent outside flow - no cross-exchange of momentum and energy with direction perpendicular to the surface 142 instead of. Upon reaching a critical run length N _crit , an envelope of the boundary layer state takes place. It forms a turbulent boundary layer 152 out, which continues to grow. Within this is an exchange of momentum, mass and energy transverse to the main flow direction 116 due to the turbulent fluctuation speeds possible. In the vicinity of the surface 142 a laminar lower layer forms 154 , which, however, is much thinner than the previous laminar boundary layer.

Analogous to the fluid dynamic boundary layer forms, as in 2C represented and in 2 B The fluid dynamic boundary layer faced, a thermal boundary layer. For these the same laws apply as for in 2 B illustrated fluid dynamic boundary layer. Within the laminar boundary layer heat transfer takes place only by heat conduction through the layers in the direction of the wall. The fluid dynamic boundary layer thickness is in 2 B denoted by δ, whereas the thermal boundary layer thickness in 2C denoted by δ _T. The core flow is indicated by the reference numeral 156 designated. The thicker the boundary layer grows, the smaller the transferable heat flow. With the transition into a turbulent boundary layer, an increase in the transferred heat flux sets in, since the laminar underlayer is thinner than the laminar boundary layer and because the turbulent fluctuation rates constantly move fluid medium at a higher temperature into the vicinity of the wall.

The in the 5A to 5H illustrated embodiments of turbulator elements 144 on the surface 142 of the temperature sensor 114 , in particular in the region of the measuring head 128 , thus causing an earlier transition into a turbulent boundary layer and a constantly new structure of the boundary layer. As a result, the heat transfer is designed to be particularly high. The temperature sensors 114 are preferably used such that the flow direction 116 the fluid medium across at least one edge of a turbulator element 144 runs. This is in all of the in the 5A to 5H given embodiments shown. Furthermore, the turbulator elements cause 144 , like out US 2007/0195857 A1 in addition, an enlargement of the surface available for the heat transfer, in addition to increasing the heat transfer coefficient by influencing the boundary layer structure according to the 2A to 2C , The options presented here for shaping the surface 142 correspond in part to the patterns used on an industrial scale to increase the Heat transfer in stationarily operated heat exchangers, for example in plant construction, air conditioning or the like. However, these have hitherto been used only to increase the efficiency of heat exchangers, but not to increase the dynamics and / or the measurement accuracy of temperature sensors. An overview of further shaping possibilities of the turbulator elements 144 can be found, for example Ralph L. Webb: Principles of Enhanced Heat Transfer, John Wiley & Sons, Inc., 1992, pp. 231, 241 and 248 ,

The heat transfer coefficient in a body flowing around, therefore, as explained above, depends both on the geometry and surface structure of the body as well as the Umströmungsbedingungen. The turbulator elements 144 in the illustrated embodiments are preferably constructed as a microstructure and preferably have a tread depth, ie a maximum depth or height of the structural elements 146 , of at most 10 μm, in particular 1 to 2 μm. In this respect, an artificial surface roughness by the turbulator elements 144 with the structural elements 146 be provided in the form of a microstructure, which ensures a permanent disturbance of the hydrodynamic and thermal boundary layers. This leads to an increase in the heat transfer coefficient due to the thus increased pulse and energy exchange. The artificial surface roughness in the form of turbulator elements 144 are characterized by the fact that their characteristic height is small compared to the remaining dimensions of the temperature sensor 114 , in particular the measuring head 128 , So can the typical widths of the structural elements 146 and / or their heights, for example, by at least a factor of 10, preferably by at least a factor of 100 and even by at least a factor of 1000 be smaller than the diameter of the measuring head 128 perpendicular to the axis 138 of the temperature sensor 114 , In addition, the roughness by a suitable design of the structural elements 146 both from the surface 142 to the outside (eg in the form of the trip wires or needles according to the embodiments in FIGS 5A to 5D ) as well as inwardly (eg in the form of grooves, dents, grooves or the like, for example according to the embodiments in the 5F to 5H ).

A further embodiment of a turbulator element according to the invention 144 in the area of a measuring head 128 a temperature sensor 114 is in 6A shown. Hereby, the turbulator element comprises 144 a knurl 158 , Under a knurl is to understand a profile structure having a plurality of parallel grooves. At least one group of grooves should have a transverse component perpendicular to the main flow direction 116 having the fluid medium. Embodiments of these knurls are in the 6B to 6F shown. So shows 6B a knurl with axially parallel grooves, which preferably completely perpendicular to the flow direction 116 be aligned of the fluid medium. A cross section through the grooves is in 6G shown. The letter t denotes standardized divisions, which may be, for example, 0.5, 0.6, 0.8, 1.0, 1.2 or 1.6 mm. d ₁ denotes a nominal diameter, and d ₂ an initial diameter. In the knurl according to 6B For example, d ₂ = d ₁ - 0.5 · t.

6C shows a so-called right knurl. The angle α between the axis 138 and the grooves may for example be from 10 to 50 °, preferably from 20 to 40 ° and in particular 30 °, and it may be: d ₂ = d ₁ - 0.5 · t. The same applies to a in 6D represented so-called left-hand knurl. In 6E is a so-called left-right knurl shown, for which the angle α may also be from 10 to 50 °, in particular from 20 to 40 and particularly preferably 30 °. For an increased left-right knurl, for example: d ₂ = d ₁ - 0.67 · t, and for a recessed left-right knurl d ₂ = d ₁ - 0.33 · t.

In 6F Finally, a so-called Kreuzrändel is shown, with a plurality of to the axis 138 parallel grooves and a plurality of perpendicular to the axis 138 running grooves. For an increased cross knurl, for example, d ₂ = d ₁ - 0.67 · t and for a recessed cross knurl d ₂ = d ₁ - 0.33 · t. The grooves may have, for example, a groove angle β, which is also in 6G is shown. This groove angle can be, for example, 70 ° to 110 °, in particular 80 ° to 100 ° and particularly preferably 90 °. However, other embodiments are possible in principle. In any case, in the 6B to 6F illustrated turbulator elements 144 in the form of the knurl 158 are each components perpendicular to the flow direction 116 of the fluid medium. Especially in the case of a left-right knurl according to 6E or in the case of a cross knurl according to 6F the roughness are also directed perpendicular or at an angle to the flow.

As shown above, the concepts A), B) and C) are independent of each other or in any combination AB, AC, BC or ABC feasible. Thus, in the 5A to 6G illustrated embodiments with turbulator elements 144 , which represent realization possibilities of the concept C), can also be combined with the concepts B) and / or C) which, incidentally, can also be implemented independently of A). Embodiments of the concepts B) and / or C) will be briefly described below. For this purpose, based on a schematic representation in 7 one typical structure of a temperature sensor 114 will be briefly explained according to the prior art. The temperature sensor 114 again has a sensor body 124 on, which in this case seamlessly into a measuring head 128 with a sensor element 130 passes. The sensor element 130 is designed in this case, for example, as a thermocouple and is created by the connection of two metallic conductors 160 from different materials, which at a measuring point 162 that is the actual sensor element 130 forms, be joined together. The connected conductors 160 (Thermal conductor) are also referred to as a thermocouple. The connection of the metallic conductors acting as thermoelectric cables 160 is generated for example by welding and / or soldering. The metal combinations of metallic conductors 160 for thermal lines are usually standardized, so that different types of thermocouples from the prior art are known. The size of the diameter of the thermowires 160 correlates with the cost and usually with the life of the thermocouple.

The in 7 illustrated typical temperature sensor 114 is a so-called coat thermocouple. The thermoelectric cables 160 are usually in a ceramic insulating package 164 embedded, for example from MgO and / or Al ₂ O ₃ . To the outside is the electrically insulated thermocouple through a jacket 166 with a jacket material, such as stainless steel and / or ceramic, protected from the environment. Sheath thermocouples like the one in 7 exemplary temperature sensors 114 with metallic sheath are usually made of a so-called mineral insulated line (MIL), which in almost any material combinations with regard to the thermoelectric cables 160 , the insulating material of the insulating package 164 and the jacket material of the jacket 166 as well as in different defined dimensions, in particular with regard to diameter, jacket thickness, thickness of the thermoelectric lines 160 or similar dimensions, can be obtained as an endless product. As a rule, it should be noted that the maximum operating temperature of the jacket thermocouple depends on the jacket and cable diameter as well as the insulation resistance of the mineral insulator. When assembling the MIL is cut to length and removed at one end mineral insulating material to the actual thermoelectric lines 160 expose. The exposed wires are welded to the measuring point, and the missing insulating material is refilled and compacted. Subsequently, the jacket tube of the jacket 166 closed at the same end, for example by welding. At the other end, ie at the measuring head 128 opposite end of the temperature sensor 114 , a piece of the jacket tube is removed to the thermal lines 160 expose as connecting wires, for example, for a plug, crimps or the like.

The above-described concepts A) to C) for improving the thermal design of the temperature sensor 114 can be individually, in any pair combination or in total, also on temperature sensor 114 with thermocouples analogous to the embodiment according to 7 transferred, in which the actual sensor element 130 by a junction between at least two metallic conductors 160 and / or thermoelectric lines is formed. Thus, for example, the designs of the surface 142 in the area of the measuring head 128 by using one or more turbulator elements 144 transferred to this embodiment. Alternatively or additionally, concepts A) and / or B) can also be based on this concept of temperature sensors 114 transfer. This will be shown below by way of example.

So can the sensor element 130 especially in such a way in the measuring head 128 be included, that this at least largely from the sensor body 124 thermally decoupled. This means that a heat transfer between the sensor element 130 and the surrounding fluid medium by structural design of the measuring head 128 is favored, especially in comparison to a heat transfer to the sensor body 124 , which is preferably suppressed. This can be done, for example, by a constructive design adaptation at the measuring point 162 respectively. An energy exchange by convection and radiation and thus the heat transfer between one in the device 110 installed sensor element 130 and its surroundings and the height of the occurring temperatures (in particular due to an influence of the radiation from temperatures above 500 ° C) lead to a systemic deviation of the measured temperature and the actual prevailing temperature in the medium. In addition, the heat transfer or the heat exchange cause a delayed response of the temperature sensor 130 at the measuring point 162 , By means of the concepts A) to C) described above or at least the concepts A) and / or B), the accuracy and the dynamics can be increased. So the energy supply to the measuring point 162 or the energy dissipation from this measuring point 162 in the radial direction, that is perpendicular to the axis 138 to be designed very fast. As a result, the temperature change in the entire medium with minimal delay to the measuring point 162 transfer. Alternatively or additionally, the energy supply to the measuring point 162 or the sensor element 130 (which should be synonymous) and / or the energy dissipation from the measuring point 162 in the axial direction, ie parallel to the axis 138 , prevented or at least reduced become. The temperature difference between the measuring point 162 and the fluid medium remains as small as possible. These basic principles and aspects derived therefrom can be realized, for example, in the exemplary embodiments presented below. Such is an embodiment of a temperature sensor according to the invention 114 or a part of a device according to the invention 110 in the 8A (Partial section of the page) and 8B (partially opened perspective view) shown. Again, this is an example of a jacket thermocouple with the above based on the 7 described MIL structure, with a sensor body 124 and a measuring head 128 , The thermocouples are again with the reference numeral 160 designated. The actual sensor element 130 is in turn by connecting the ladder 160 at a measuring point 130 , which may also be a broader measuring range, is formed.

The sensor element 130 is in this embodiment of a coupling element 168 in the form of a ceramic sleeve 170 or surrounded by a ceramic tube. The coupling element 168 is in turn by a thin-walled, thermally conductive as possible protective sleeve 172 Protective cap surrounded, which provides a mechanical protection for the sensor element 130 provides and the measuring head on the sensor body 124 fixed. The protective cap can be attached to the end face of the temperature sensor 114 closed or at least partially open configured. The protective cap may for example be made of a plastic material with high thermal conductivity and / or a metallic material. Optionally, on the outer surface 142 the protective sleeve 172 one or more turbulator elements 144 be arranged, for example according to the embodiments described above, which in the 8A and 8B are not shown.

The completion of the in the 8A and 8B represented temperature sensor 114 is different from that based on the in 7 described prior art as follows. After cutting to length the MIL becomes a piece of the jacket tube 166 removed, and the thermoelectric cables 160 are exposed. The thus exposed metallic conductors 160 are preferably compacted and / or compressed, for example, a flat contact between the conductors 160 to create. Subsequently, the MIL with compact measuring point 162 and the protective sleeve 172 with pressed ceramic tube or pressed ceramic sleeve 170 as in the 8A and 8B shown, joined. MIL towards the protective sleeve 172 with the coat 166 the MIL connected, for example by welding.

As shown above, an end face 174 of the measuring head 128 be open or closed designed. At an open end 174 can, as in 9 shown as an optional embodiment, using, for example, a suitable welding method such. B. a laser welding, a melted pearl 176 are generated, which also part of the coupling element 168 can be. In this way it can be achieved, for example, that between the sensor element 130 or the measuring point 162 and the ceramic tube of the ceramic sleeve 170 a substantially gap-free transition, for example in the form of a positive connection 178 , arises. It can thus be a gap-free transition between the sensor element 130 and the coupling element 168 and preferably also the protective sleeve 172 be generated. Furthermore, in order to reduce a thermal conductivity in the axial direction, between the sensor element 130 and the sensor body 124 at least one isolation element 180 be arranged. In the illustrated embodiments according to the 8A to 9 this may be, for example, an air gap 182 act. Alternatively or additionally, other types of isolation elements may be used 180 used, for example, one or more layers of a thermally insulating material, one or more insulating sleeves or the like. In this way, a heat transfer in the axial direction can be reduced. The front side 174 of the temperature sensor 114 according to the 8A to 9 can be closed. For this purpose, for example, after the process steps described above, the protective sleeve 172 on the front side 174 be welded with a lid, or the protective sleeve 172 Can be configured from the outset as a closed protective sleeve.

For example, by the in the 8A to 9 described manufacturing method, but also by means of other embodiments of the present invention, the basic principles A) and / or B) described above can be implemented constructively well. Thus, a good heat conduction in the radial direction, ie perpendicular to the axis 138 of the temperature sensor 114 , A good thermal connection of the sensor element 130 or the measuring point 162 to the fluid medium is achieved by reducing, for example, the air gaps in the radial direction to a minimum. This is for example in the embodiments described above by means of a positive connection and / or an interference fit between the protective sleeve 172 and the coupling element 168 and / or the sensor element 130 achieved, optionally in combination with the optional positive connection between the coupling element described above 168 and the sensor element 130 about, for example, a melted pearl or another type of positive locking. In addition, optional Mass and / or the specific heat capacity of the material of the measuring head 128 at the measuring point 162 reduced or even minimized by suitable miniaturization and / or material selection. At the same time, alternatively or additionally, by a suitable structuring of the surface 142 by means of the optional at least one turbulator element 144 according to strategy C) of the above options, both the area available for heat transfer and the heat transfer coefficient can be maximized. Alternatively or additionally, as described above, a thermal decoupling in the axial direction, ie parallel to the axis 138 , allowing a heat transfer between the measuring head 128 and sensor body 124 at least compared to a continuous sensor body 124 in a one-piece embodiment according to 7 is reduced. This can, for example, as in 9 represented by means of an air gap insulation can be achieved. In addition, the wall thickness of the protective sleeve 172 , For example, the protective cap can be reduced, in particular in the radial direction, for example, to wall thicknesses below 1 mm, preferably below 0.5 mm.

In 10 is another embodiment of a device according to the invention 110 and a temperature sensor according to the invention 114 which shows a modification of the embodiment in FIG 9 represents. Accordingly, reference may largely be made to the above description. Again, the temperature sensor points 114 a sensor body 124 and a measuring head 128 on. As in the embodiments described above, the measuring head 128 also in this embodiment with a compared to the sensor body 124 be designed reduced diameter. For example, a diameter reduction to two thirds of the diameter of the sensor body 124 or less. The measuring head 128 can turn from a protective sleeve 173 be surrounded, which in principle is integral with the coat 166 of the sensor body 124 may be formed, which, however, only with this coat 166 may be connected or otherwise with the sensor body 124 may be connected, for example, analogous to the embodiments in the 8A to 9 , Optionally, the surface 142 this protective sleeve 172 , in particular the peripheral surface 142 and / or the frontal surface 142 , in turn, be structured by means of one or more turbulator elements 144 , In this as well as in other embodiments, between the protective sleeve 172 and the sensor body 124 For example, the coat 166 , Also be arranged one or more additional insulator elements. Again, the temperature sensor points 114 at least one sensor element 130 at a measuring point 162 on, for example, according to the embodiment in the 8A to 9 or according to other embodiments. For example, again NTCs, PCTs, resistors, thermocouples or other types of sensor elements 130 be used.

In order to achieve a high dynamic of the temperature measurement, the sensor element must 130 heated as quickly as possible or cooled as quickly as possible. The amount of energy to be transported is proportional to the product of mass and specific heat capacity of the area to be cooled or heated. To keep this area as small as possible, its dimensions must be reduced. For rapid heating or cooling, this area of the measuring head should be 128 , as in the previous embodiments, thermally from the sensor body 124 , For example, the shaft of the temperature sensor 114 to be decoupled. This will prevent energy from heating up in the sensor body 124 flows away and is not available for heating, or, in the opposite case, energy from the sensor body 124 flows in and the cooling of the area of the measuring head 128 delayed. The thermal decoupling can also be found in the in 10 illustrated embodiment in turn via one or more isolation elements 180 take place, for example via one or more air gaps. To achieve the best possible thermal coupling between the sensor element 130 and the surrounding fluid medium, a gap may exist between the sensor element 130 and the protective sleeve 172 completely or partially with a filling material 184 fill out. For this filling material 184 it may be, for example, a metallic and / or ceramic filler material and / or a plastic filler material. The filling material 184 For example, it may be introduced into the space in the form of a powdery filling material and / or otherwise, for example in the form of a liquid or viscous filling material 184 , Subsequently, optional hardening can take place. Also thermally conductive plastics, such as thermally conductive thermosets, elastomers or thermoplastics can be used.

The basis of the 8A to 10 illustrated embodiments of an implementation of the concepts A) and / or B) according to the above description can also be combined with the embodiments of the concept C) according to the above description. Thus, the embodiments can be individually or in combination, for example, with the examples of turbulator elements 144 according to the 5A to 6G combine so that these turbulator elements 144 optionally also, for example, on the diameter-reduced measuring head 128 according to the embodiments according to the 8A to 10 can be applied. Alternatively or additionally for example, the insulation element 180 and / or the coupling element 168 in the embodiments according to the 5A to 6G or in other embodiments of the concept C). Various combinations are conceivable.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2007/0195857 A1 [0004, 0017, 0042, 0047]

Cited non-patent literature

• Ralph L. Webb: "Principles of Enhanced Heat Transfer," John Wiley & Sons, Inc., 1992, p. 231, 241, and 248 [0047]

Claims (10)

Contraption ( 110 ) for detecting a temperature of a fluid medium, comprising at least one temperature sensor ( 114 ), whereby the temperature sensor ( 114 ) is adapted to be introduced into the fluid medium, wherein the temperature sensor ( 114 ) a sensor body ( 124 ) and a projecting into the fluid medium measuring head ( 128 ), wherein in the measuring head ( 128 ) at least one sensor element ( 130 ) is recorded for detecting a temperature, wherein the sensor element ( 130 ) in the measuring head ( 128 ) that this at least largely thermally from the sensor body ( 124 ) is decoupled. Contraption ( 110 ) according to one of the preceding claims, wherein the thermal decoupling of the sensor element ( 130 ) from the sensor body ( 124 ) via at least one between the sensor element ( 130 ) and the sensor body ( 124 ) arranged isolation element ( 180 ), wherein the insulation element ( 180 ) is arranged to prevent heat transfer between the sensor element ( 130 ) and the sensor body ( 124 ) to suppress. Contraption ( 110 ) according to the preceding claim, wherein the insulating element ( 180 ) is selected from: an element with low thermal conductivity, in particular an insulating layer and / or an insulating sleeve; a gas gap ( 182 ). Contraption ( 110 ) according to one of the preceding claims, wherein the measuring head ( 128 ) at least partially by a thermally conductive protective sleeve ( 172 ) is surrounded. Contraption ( 110 ) according to one of the preceding claims, wherein the measuring head ( 128 ) compared to the sensor body ( 124 ) has a smaller diameter. Contraption ( 110 ) according to one of the preceding claims, wherein the measuring head ( 128 ) in the region of the sensor element ( 130 ) is configured in the radial direction at least substantially free of gaps. Contraption ( 110 ) according to one of the preceding claims, wherein the sensor element ( 130 ) at least partially in at least one coupling element ( 168 ), wherein the coupling element ( 168 ) is configured to heat exchange between the sensor element ( 130 ) and the fluid medium compared to a heat exchange between the sensor element ( 130 ) and the sensor body ( 124 ) to favor. Contraption ( 110 ) according to the preceding claim, wherein the coupling element ( 168 ) from the sensor body ( 124 ) is thermally decoupled. Contraption ( 110 ) according to one of the two preceding claims, wherein the coupling element ( 168 ) comprises at least one material having one or more of the following properties: a material of lower density than the average density of the materials of the sensor body ( 124 ) in one to the measuring head ( 128 ) adjacent area; a material with a lower specific heat capacity than the average specific heat capacity of the materials of the sensor body ( 124 ) in one to the measuring head ( 128 ) adjacent area; a material with a higher thermal conductivity than the average thermal conductivity of the materials of the sensor body ( 124 ) in one to the measuring head ( 128 ) adjacent area. Contraption ( 110 ) according to one of the three preceding claims, wherein the coupling element ( 168 ) is selected from: one the sensor element ( 130 ) at least partially enclosing sleeve of a ceramic material, in particular a ceramic material with high thermal conductivity; one the sensor element ( 130 ) at least partially enclosing sleeve made of a plastic material, in particular a plastic material with high thermal conductivity; one the sensor element ( 130 ) at least partially enclosing sleeve of a metallic material; one the sensor element ( 130 ) at least partially enclosing melted pearl ( 176 ), in particular a melted pearl ( 176 ) made of a plastic material and / or a melted pearl ( 176 ) of a metallic material and / or a melted pearl ( 176 ) made of a glass material; a filling material ( 184 ) in a space between the sensor element ( 130 ) and a measuring head ( 128 ) at least partially enclosing protective sleeve ( 172 ).

Images