阅读说明：本技术 用于非侵入式测定流过导管区段的流体的温度的方法 (Method for non-invasively determining the temperature of a fluid flowing through a conduit section ) 是由 J·格布哈特 G·佐萨莱 A·德克 W·达克 J·霍斯特科特 P·乌德 P·萨斯 U· 于 2019-03-06 设计创作，主要内容包括：本发明涉及一种用于测定流过导管区段(11)的流体(12)的温度的方法,其中：-确定导管区段(11)的温度,-以与导管区段(11)的表面(14)的间距(13)检测参考温度,-根据流体(12)的状态参量的至少一个值和/或至少一个物质特性测定在导管区段(11)的内壁处流体(12)的边界层(15)的传热性能、尤其热阻,并且-根据边界层(15)的传热性能、导管区段(11)的传热性能、尤其热阻、导管区段(11)的温度和参考温度测定流体(12)的温度。(The invention relates to a method for determining the temperature of a fluid (12) flowing through a conduit section (11), wherein: -determining the temperature of the conduit section (11), -detecting a reference temperature at a distance (13) from a surface (14) of the conduit section (11), -determining a heat transfer property, in particular a thermal resistance, of a boundary layer (15) of the fluid (12) at an inner wall of the conduit section (11) depending on at least one value of a state parameter of the fluid (12) and/or at least one material property, and-determining the temperature of the fluid (12) depending on the heat transfer property of the boundary layer (15), the heat transfer property, in particular the thermal resistance, of the conduit section (11), the temperature of the conduit section (11) and the reference temperature.)

1. A method for determining the temperature of a fluid (12) flowing through a conduit section (11), wherein:

-determining a temperature of the conduit section (11),

-detecting a reference temperature at a distance (13) from a surface (14) of the conduit section (11),

it is characterized in that the preparation method is characterized in that,

-determining a heat transfer property, in particular a thermal resistance, of a boundary layer (15) of the fluid (12) at an inner wall (16) of the conduit section (11) on the basis of at least one value of a state variable of the fluid (12) and/or at least one material property, and

-determining the temperature of the fluid (12) from the heat transfer properties of the boundary layer (15), the heat transfer properties, in particular the thermal resistance, of the conduit section (11), the temperature of the conduit section (11) and the reference temperature.

2. Method according to claim 1, characterized in that the heat transfer properties of the boundary layer (15) are calculated by means of the knossel number for describing the flow state of the fluid (12).

3. Method according to claim 1 or 2, characterized in that the material property of the fluid (12) is determined by at least one measurement.

4. Method according to any of the preceding claims, characterized in that the heat transfer performance of the conduit section (11) is determined from the material properties of the conduit section (11), wherein the material properties of the conduit section (11) are detected by at least one measurement.

5. Method according to any of the preceding claims, characterized in that the material property of the fluid (12) is detected by means of a first input interface (31).

6. Method according to any one of the preceding claims, characterized in that the value of a parameter influencing the heat transfer performance of the conduit section (11) is detected by means of a first or a second input interface.

7. Method according to any one of the preceding claims, characterized in that the value of a process variable of a process in which the fluid is used as a medium is detected by means of a first, a second or a third input interface and the temperature of the fluid (12) is calculated by means of the value of the process variable.

8. The method of claim 7, wherein the process parameter is a Reynolds number of a flow formed by the fluid.

9. The method according to claim 7, wherein the process parameter is a prandtl number of a flow formed through the fluid (12).

10. The method according to claim 7, wherein the process parameter is the Knoop number of the flow formed by the fluid (12).

11. Method according to any of the preceding claims, characterized in that the slope of the conduit section (11) is detected and a warning is output to the user depending on the slope, wherein the warning contains information about the accuracy of the measured temperature of the fluid.

12. Method according to any one of the preceding claims, characterized in that a description (51) for characterizing the fluid (12) is detected and the material properties of the fluid (12) are determined with the aid of the description (51).

13. Method according to any of the preceding claims, characterized in that the material properties of the fluid (12) are determined temperature-dependently.

14. Method according to claim 13, characterized in that the material properties of the fluid (12) are determined as a function of an estimated temperature of the fluid (12), in particular as a function of the temperature of the conduit section (11), and in that the temperature of the fluid (12) is first determined as a function of the estimated temperature.

15. The method according to claim 14, characterized in that the temperature of the fluid (12) is determined anew, wherein the material properties of the fluid (12) are determined depending on the previously determined temperature of the fluid (12).

16. Method according to any of the preceding claims, characterized in that the value of the Reynolds number describing the flow of the fluid (12) is determined and one of at least two different models is used for calculating the Knudsen number depending on the value of the Reynolds number.

17. A system (22) for determining the temperature of a fluid (12) flowing through a conduit section (11), wherein the system (22) has an evaluation unit (19) and a first temperature sensor (17) and the evaluation unit (19) is set up for:

-detecting the temperature of the conduit section (11),

-detecting a reference temperature measured by means of the first temperature sensor at a distance from a surface (14) of the conduit section (11),

it is characterized in that the preparation method is characterized in that,

the evaluation unit (20) is designed to,

-determining a heat transfer property, in particular a thermal resistance, of a boundary layer (15) of the fluid (12) at an inner wall of the conduit section (11) on the basis of at least one value of a state variable of the fluid (12) and at least one material property,

-determining the temperature of the fluid (12) from the heat transfer properties of the boundary layer (15), the heat transfer properties, in particular the thermal resistance, of the conduit section (11), the temperature of the conduit section (11) and the reference temperature.

Technical Field

The invention relates to a method for determining the temperature of a fluid flowing through a line section (Leitungsabschnitt). Fluids are understood to mean at least, but not exclusively, liquids, gases and bulk materials (Schuettgut).

Background

One such method is known, for example, from document WO 2017/131546 a 1. The method described therein is characterized in that a shank is arranged between the point at which the ambient temperature is measured and the point at which the surface temperature of the outer surface of the conduit section is measured, from which the thermal resistance is known. By means of the known thermal resistance and the two measured temperatures, the heat flow through the shaft is calculated according to the disclosure and the temperature of the fluid is calculated from this heat flow. The described method has however the serious disadvantage that the ultimate heat transfer capacity of the fluid boundary layer is not taken into account. The method described in the disclosure accordingly provides first only an estimate of the temperature at the inner wall of the conduit.

For a large number of fluid and practice-related application scenarios, however, this estimate is significantly different from the average fluid temperature.

In many practically relevant cases, the thermal resistance of the fluid boundary layer is significantly higher than the thermal resistance of the conduit section, e.g. the pipe wall.

This disadvantage is to be overcome in particular with the present invention.

DE 102014019365 a1 describes a measuring device for determining the temperature of a medium in a container or in a line. The measuring device comprises at least one temperature sensor arranged externally at the wall of the container or conduit with an output for the temperature recorded thereby. The measuring device takes into account that the wall of the container or the conduit functions well approximately as a PT1 element in the transfer function with which the change in temperature of the medium is transmitted to the temperature registered by the temperature sensor. The measuring device can thus determine the actual temperature-time course significantly more accurately than according to the prior art. The technical teaching aims at an as accurate and fast responding estimation of the temperature outside the container or the conduit as possible.

DE 10201610949 a1 discloses a non-invasive temperature measuring device for measuring the temperature of a fluid in an at least partially insulated pipe of a plant in the process industry. Non-invasive temperature sensors are disclosed therein, with which the temperature of a fluid can be determined without compromising the thermal insulation of the pipe. For this purpose, the measuring device has sensor electronics with a temperature sensor and connection electronics with a processing unit. The sensor electronics are arranged within a thermally insulating layer surrounding the tube and the connection electronics are arranged outside this insulating layer. The measuring means is arranged to wirelessly communicate the temperature measurement to the connection electronics by the sensor electronics. The purpose of this technical teaching is also only to obtain good measurements of the temperature of the surface of the catheter.

Disclosure of Invention

Starting from this, the object of the invention is to further develop a method of this type for determining the temperature of a fluid flowing through a line section in such a way that a high degree of accuracy is achieved in the estimation of the actual average fluid temperature.

This object is achieved with a method with the features of claim 1 and with a system with the features of claim 17. Advantageous embodiments of the method are the subject matter of the dependent claims.

The temperature of the fluid determined in this way can be regarded as the temperature of the fluid averaged over the cross section of the conduit section (see [4 ]). Here, the defined cross-sectional form relating to the average temperature ends at the inside of the duct wall.

T_mDefined by convective heat flow in the conduit, while the local flow of heat capacity is used as a weighting function for forming an average:

。

where A is the cross-sectional area of the fluid in the conduit section,vis the flow velocity that depends on the location.c _P Representing the possible location-dependent specific heat capacity per mass of fluid, and p represents the location-dependent density.

In incompressible flow (ρ = const) and constant heat capacityc _P In the case of (2), the average temperature is very simple in combination with the convective heat flow

Mass flow ofAnd volume flowAnd (3) associating:

。

the boundary layer can be present in the form of a laminated boundary layer, a turbulent boundary layer or a transition layer having the properties of a laminated and/or turbulent boundary layer. Possibly, the boundary layer has a sticky under layer. The advantage of the proposed method is that the heat transfer properties of the boundary layer (waermeuertragungsverhalten), in particular the thermal resistance of the boundary layer, are taken together into the calculation of the temperature of the fluid and the temperature of the fluid can thus be determined more precisely.

The temperature of the conduit section is preferably a surface temperature, which may be measured at an outer or inner surface of the conduit section. The conduit section may be a section of pipe with insulation (e.g. in the form of mineral wool or polyethylene foam insulation). Furthermore, the inner wall of the conduit section may be coated. It is advantageous if the temperature of the conduit section is measured not at the outer surface of the conduit section but in the interior, for example in the interior of the insulation, but nevertheless at the outer wall of the actual fluid conduit. Most simply, the measurement of the temperature of the conduit section is at the outer surface, as the outer surface is easily accessible.

The reference temperature is measured at a distance from the point at which the temperature of the line section is detected, so that a thermal resistance R of the surroundings is formed between this point and another point at which the reference temperature is measured_F. The thermal resistance of the surroundings can be formed, for example, by air and/or by a solid body, such as a partial layer of an insulating layer of a rod or a pipe section.

The material property (Stoffeingenschaft) of the fluid may be density ρ and dynamic viscosity η of the fluid_fλ, heat conductivity_fSpecific heat capacity c_pPrandtl number Pr and/or phase state. The state variable (Zustandsgroosse) of the fluid may be the pressure p or the velocity v.

The heat transfer performance of the boundary layer is preferably calculated via calculation of a heat transfer coefficient a depending on the velocity of the fluid in the conduit section and the thermal conductivity of the fluid.

Possible variants for calculating the temperature of the fluid are described next. The physical principles are basically known, for example from the references [1-5 ]]And typically from the thermodynamics of heat exchange, for example. In a first step, the thermal resistance R of the boundary layer is calculated in the form of the quotient of the internal hydraulic diameter of the line section as dividend and the product as divisor according to the formula_bl. The product is derived from the nussel number used to describe the flow state of the fluid in the conduit section multiplied by the thermal conductivity of the fluid.

,。

In a second step, the thermal resistance R of the section of the conduit, e.g. the wall of the conduit, is calculated according to the above formula_w. The thermal resistance of the conduit section relates to the wall section of the conduit section between the inner and outer surfaces of the conduit section. Instead of the inner radius r shown above, which depends on the duct section₁And an outer radius r₂The heat transfer performance of the conduit section may be performed by means of a linear approximation in the form of the difference between the outer and inner radius of the conduit section. If the thermal resistance of the conduit section is nevertheless determined by means of a logarithmic function from the outer diameter r₂And inner diameter r₁The resulting quotient is calculated as an independent variable (Argument), which allows a more precise approximation of the heat distribution in the pipe section, for example in [4]]As described in (1).

The nussel number Nu can be calculated in an approximation for the case of a fluid flowing in a conduit section with turbulent flow, for example as follows:

,

where Re is the Reynolds number and Pr is the Plantet number, where the Plantet number Pr and Reynolds number Re are calculated as follows:

,,

wherein the dynamic viscosity eta_fSpecific heat capacity c_pHeat transfer capacity lambda of the fluid_fVelocity U of fluid in conduit section_fDensity of fluid ρ_fAnd a characteristic length l. The length l can advantageously be the diameter of the fluid cross section, for example the hydraulic diameter d = 4A/U. Here, A is the fluid cross-sectional area and U is the catheter wetted by the fluidThe length of the perimeter. In the literature, further approximation formulas can also be found for the functional relationship Nu (Re, Pr, L) in the range of turbulent flows, where L denotes the hydraulic conduit diameter and L denotes the approximate length of the straight entry section before the measurement point.

In the case of laminar flow, i.e. when the approximation applies:Re<2300, can be described in terms of a nussel number: nu ≈ 3.66 as long as a uniform temperature can be approximately assumed at the housing of the conductor (leitersttech) as a boundary condition (Dirichlet boundary condition). If the boundary conditions in the case of laminar flow are more precisely constant heat flows (von-Neumann boundary conditions), Nu ≈ 4.364 applies.

For a signal in transition range 2300<Re<10⁴In the case of flows in (ii), it is advantageous, for example, to use linear Interpolation (Interpolation) between the values set in the above-described manner for the stacked knossel numbers and the knossel numbers derived from the formula set for the turbulent flow region, at Re =10⁴In the case of (1):

Nu_trans≈ (1-x) ⋅ Nu_lam+ x ⋅ Nu_turb(10⁴) , x≔(Re-2300)/(10⁴-2300)。

in a third step, the temperature of the fluidT _M Can be calculated according to the following formula:

，

wherein, T_waIs the temperature of the section of conduit, T_eIs a reference temperature and R_FIs the thermal resistance of the surrounding environment. The ambient environment extends between another point where the reference temperature is measured and a point where the temperature of the conduit section is measured. Depending on where the temperature of the conduit section is measured, the thermal resistance R of the surrounding environment_FMay be calculated differently. If the temperature of the conduit section is measured, for example, between the surface of the conduit section and the outer surface of the insulation of the conduit section, the thermal resistance of the insulation together introduces a thermal resistance R_FIn the calculation of (2).

In a further variant, the heat flow I from the surface of the conduit section to the point at which the reference temperature is measured can also be determined. The heat flow I can be calculated as follows:

。

the heat flow I may be used as an intermediate result for calculating the temperature of the fluid. Alternatively, the heat flow can also be determined by estimation, as described in DE 102017122422.4.

The advantage of calculating the heat transfer properties of the boundary layer by means of the Knoop number is that the Knoop number is dependent on the velocity u of the fluid_fDensity and dynamic viscosity eta of fluid_fThe correlation with prandtl number was studied by a number of scientific experiments over the past decades and indirectly traced back to the results of these experiments by using the knoop number. Thus, when the knossel number is introduced together into the calculation of the temperature of the fluid, the temperature of the fluid can be determined more accurately.

In order to determine the optimum nussel number for the stack region, it can advantageously be estimated whether the application corresponds to more precisely Dirichlet boundary conditions or more precisely Neumann boundary conditions or special impedance boundary conditions or Robin boundary conditions. Depending on this, the knoop number of the stack is advantageously set for the measured value correction.

A preferred embodiment of the method provides that the material property of the fluid is determined by at least one measurement. The thermal conductivity of the fluid upstream of the conduit section can thus be determined, for example, by measurement. This has the advantage that it is not necessary to manually introduce the material properties into the system for calculating the temperature of the fluid. Furthermore, the material properties can be determined more accurately by means of this measurement, since the fluid has material properties that vary with temperature. Advantageously, the material property is measured upstream of the conduit section by means of a measuring instrument in the apparatus in which the conduit section is installed. With the measuring instrument, for example, the reynolds number or the pressure of the fluid can be detected, from which the material properties can be approximated indirectly.

According to a further embodiment, the heat transfer performance of the conduit section is dependent on the conduit sectionMaterial properties (materialigenschaft), wherein the material properties of the conduit section, for example the heat conductivity λ of the conduit section_wIs determined by at least one measurement.

A particularly advantageous embodiment provides that the material properties of the fluid and/or of the material properties of the line section are detected by means of the first input interface of the system. The advantage of this embodiment is that the user can carry out the proposed method for determining the temperature of a fluid at different devices and with different fluids. The method or the system for carrying out the method is thus very flexibly designed. The material property may be the above-mentioned material property of the fluid, such as density, dynamic viscosity, thermal conductivity, specific heat capacity, and the like.

A further development of the method can provide that the value of the variable influencing the heat transfer performance of the line section is detected by means of the first or second input interface.

The parameters can be the diameter, in particular the hydraulic diameter, of the pipe section (which is obtained by means of data on the cross-sectional geometry of the pipe section if it is not round), the thickness of the wall of the pipe section, the heat conductivity λ of the pipe section_wSpecific heat capacity of the material of the conduit section, thickness of the coating of the conduit section, heat conductivity and/or specific heat capacity of the coating, thickness of the insulation layer, heat conductivity and/or specific heat capacity of the insulation layer, coefficient of friction, in particular Darcy-Moody-Weisbach coefficient of friction (which may be in accordance with [3, 4] or]Calculated) or the roughness factor of the inner wall of the conduit section (which is calculated according to Nikuradse-Sand [5 ]])。

Furthermore, it can be provided that a value of a process variable of a process using the fluid as a medium is detected by means of the first, second or third input interface and a temperature of the fluid is calculated by means of the value of the process variable. The process variable can be the reynolds number, prandtl number or knoop number of the flow formed by the fluid.

An advantage in the case of the use of process variables is that, for example, the model for calculating the heat transfer behavior of the boundary layer can have the value of the process variable as an input variable. In this case, the value of the process variable can replace a plurality of values of the variable influencing the heat transfer performance of the conduit section and/or of the material properties of the fluid. The number of input values of the model to be detected can thereby be reduced, thereby reducing the size of the parameter space formed by parameters such as the material properties of the fluid and variables influencing the heat transfer performance of the line section. The smaller scale of the parameter space simplifies generating the model and performing an approximation of the heat transfer performance of the boundary layer using the model.

An advantageous development provides that the inclination of the line section is detected and a warning is output to the user as a function of the inclination. The warning contains information about the accuracy of the measured temperature of the fluid. This enables a decision basis to be provided to the user whether the measured temperature of the fluid is not accurately determined.

In a further variant, provision can be made for instructions (Angabe) for characterizing the fluid to be detected and for the material properties of the fluid to be determined with the aid of the instructions. The description may be of the type of fluid, for example. In this way, the word "oil", for example, can be read in by means of the input interface or the fourth input interface, which can be used for exemplary purposes. In this case, it is advantageous to read all the material properties of the oil from the database, so that information for determining the material properties of the fluid can be provided in a simple manner.

Particularly advantageously, the material properties of the fluid are determined as a function of the temperature, whereby a high degree of accuracy can be achieved.

According to a refinement of the method, the material properties of the fluid can be determined as a function of an estimated temperature of the fluid, in particular as a function of the temperature of the line section, and the temperature of the fluid is first determined as a function of the estimated temperature. The estimated temperature is preferably determined as a function of an estimation function (schaetzfanction), which has the temperature of the conduit section and/or a reference temperature as arguments.

The temperature of the fluid is determined according to the above-mentioned variant using the material properties of the fluid determined from the estimated temperature. The temperature of the fluid thus determined can then be used to recalculate the material property based on the calculated temperature of the fluid. With such newly determined material properties of the fluid, the temperature of the fluid can be determined anew. Advantageously, the difference between the newly determined temperature of the fluid and the previously determined temperature of the fluid is output by means of an output unit.

Preferably, the determination of the temperature of the fluid is effected via a previous determination of the heat flow through the boundary layer and the wall of the conduit section.

A particularly precise variant of the method provides for the value of the reynolds number which describes the flow of the fluid to be determined and for one of the at least two different models to be used for calculating the knoop number depending on the value of the reynolds number. The reynolds number may be calculated here as described above.

Advantageously, a first model is applied for values of reynolds numbers smaller than about 2300 for calculating the knoop number in the case of laminar flow, a second model is applied for values of reynolds numbers approximately between 2300 and 10000 for calculating the knoop number for flow in the transition range and a third model is applied for values of reynolds numbers greater than about 10000 for calculating the knoop number for turbulent flow. In order to select the adapted model of the at least two different models for different applications, it is advantageously provided that a test calibration of the different models, that is to say the first, second and third models, is carried out. By means of the Fuzzy logic, the results of at least two of the different models can also be introduced together into the calculation of the knossel number.

The temperature of the conduit section is advantageously measured with a temperature sensor. Here, a feed temperature sensor device (annegertertemperature) described in DE 102014012086 a1 may be used, in which a reduction of the heat exchange of the extraction area (annepfflaeche) of the temperature sensor abutting against the duct section is achieved. Furthermore, the dual sensor described in DE 102017122442.4 can be used for the precise measurement of the temperature of the conduit section.

A further variant can provide for the temperature of the conduit section to be modeled by means of a temperature model. The database can advantageously be accessed here. The database preferably specifies the temperature of the conduit section depending on the different operating points of the device in which the conduit section is arranged. The reference temperature is preferably the ambient temperature measured by means of a sensor arranged in the housing of the evaluation unit or in the free ambient.

In order to achieve this object, a system for determining the temperature of a fluid flowing through a line section is also proposed. The system has an evaluation unit and a first temperature sensor, wherein the evaluation unit is designed to detect the temperature of the conduit section, to detect a reference temperature measured at a distance from the surface of the conduit section by means of the first temperature sensor, to determine the heat transfer behavior, in particular the thermal resistance, of the boundary layer of the fluid at the inner wall of the conduit section as a function of at least one value of a state variable of the fluid and at least one material property, and to determine the temperature of the fluid as a function of the heat transfer behavior of the boundary layer, the heat transfer behavior, in particular the thermal resistance, of the conduit section, the temperature of the conduit section and the reference temperature.

Drawings

Further advantages, features and details of the invention emerge from the following description and from the figures. Reference characters used herein multiple times denote the same components. The figures show schematically:

figure 1 shows the steps of a method for determining the temperature of a fluid flowing through a conduit section,

figure 2 shows a conduit section with a fluid of a boundary layer at an inner wall of the conduit section,

figure 3 shows a thermal network with the thermal resistance of the boundary layer according to figure 2,

figure 4 shows an evaluation unit for determining the temperature of a fluid according to figure 2,

figure 5 shows a model for determining at least one material property of the fluid according to figure 2 in dependence on the estimated temperature,

fig. 6 shows a model for determining at least one material property of the fluid according to fig. 5 as a function of the temperature of the fluid according to fig. 2.

Detailed Description

FIG. 1 shows a method for determining the temperature T of a fluid 12 flowing through a line section 11 shown in FIG. 2_MThe steps of (1). In a first step 1, the temperature T of the conduit section 11 is determined_wa. In a second step 2, the reference temperature T is detected at a distance from the surface 14 of the pipe section 11_e. In a third step 3The heat transfer properties, in particular the thermal resistance, of the boundary layer 15 of the fluid 12 at the inner wall 16 of the conduit section 11 are determined on the basis of at least one value of the state variable of the fluid 12 and at least one material property.

In a fourth step 4, the temperature T of the conduit section is determined as a function of the heat transfer properties of the boundary layer 15, the heat transfer properties, in particular the thermal resistance, of the conduit section 11_waAnd a reference temperature T_eDetermining the temperature T of the fluid 12_M. Reference temperature T_eThe temperature T of the conduit section 11, preferably by means of a first temperature sensor 17_waMeasured by means of the second temperature sensor 18. The first temperature sensor 17 is arranged at a distance 13 from the second temperature sensor 18. The temperature values measured by means of the first temperature sensor 17 and the second temperature sensor 18 are transmitted to an evaluation unit 19. The evaluation unit 18, the first temperature sensor 17 and the second temperature sensor 18 form a system 22 for determining the temperature of the fluid 12.

Fig. 3 shows a simplified schematic representation of a heat supply network, which is at a temperature T at which a fluid is present_MAnd the measured reference temperature T_eExtend between the positions of (a). From the temperature T at which the fluid 12 is present_MStarting from the position(s) in which the heat flow flows through the boundary layer 15, through the wall 20 of the conduit section 11, preferably through the insulating layer 21, and through the temperature T in the measuring conduit section 11_waAnd the measured reference temperature T_eTowards the detection reference temperature T_eThe position of (a). Here, the boundary layer 15 constitutes the thermal resistance R of the boundary layer 15, accordingly_blThe wall 20 and the insulation 21 constitute the thermal resistance R of the duct section 11_wAnd the reference temperature T is detected between the isolation layer 21 and the detection reference temperature T_eThe medium extending between the locations of (a) constitutes the thermal resistance R of the surrounding environment_F。

The heat flow I may be calculated according to the formula described above. It is possible that, unlike the variant shown in fig. 2, the temperature T of the line section 11_waEither within the wall 20 or within the insulating layer 21. In this case, the thermal resistance R of the conduit section_wAnd the surrounding environment (which is detecting the temperature T of the conduit section 11_waAnd the detection reference temperature T_eExtending between the locations of) a thermal resistance R_FAccordingly, it is withHe calculates it. Temperature T of fluid 12_MPreferably according to one of the above formulae.

FIG. 4 shows an embodiment of the evaluation unit 19, which is at least dependent on the detected temperature T_eAnd T_waDetermining the temperature T of the fluid 12_M. Preferably, the evaluation unit 19 has an interface 41, which reads in at least one value of at least one input variable. Advantageously, the interface 41 reads in a plurality of values of a corresponding plurality of input variables.

The input variable may comprise the hydraulic diameter D of the pipe section 11_HThickness s of wall 20_wWall 20 thermal conductivity lambda_wWall 20 specific heat capacity C_pwThe thickness s of the coating, not shown in fig. 2, on the inner wall 16_bThermal conductivity lambda of the coating_bSpecific heat capacity of coating layer C_pbThickness s of the insulating layer 21_iInsulating layer 21, heat conductivity lambda_iSpecific heat capacity C of insulating layer 21_piThe roughness coefficient of the surface of the inner wall 16Density ρ of fluid 12_fThe velocity v of the fluid 12_fThe dynamic viscosity eta of the fluid 12_fThe thermal conductivity lambda of the fluid 12_fSpecific heat capacity C of fluid 12_pfPressure p of fluid 12_fThe prandtl number Pr of the fluid 12_fAt the temperature T of the measuring tube section 11_waThe distance I between the location of (a) and the location of the fluid entering the pipe with the conduit section 11, the velocity v of the air flowing around the conduit section 11_LReference temperature T_eAnd/or the temperature T of the conduit section 11_wa。

The evaluation unit 19 preferably has a device for calculating the thermal resistance R_blFirst model 42 for calculating the thermal resistance R_wAnd a second model 43 for calculating the thermal resistance R_FThe third model 44.

The interface 41 provides the first, second and third models 42,43,44 with input variables for calculating the respective thermal resistances. Thus, for example, the first model 42 depends on the hydraulic diameter D_HCoefficient of roughness

Density of fluid ρ_fVelocity v of the fluid_fDynamic viscosity eta_fλ, heat conductivity_fSpecific heat capacity C_pfPrandtl number Pr_fDistance I and preferably pressure p_fCalculating the thermal resistance R of the boundary layer 15_bl。

The second model 43 preferably depends on the thickness s of the wall_wλ, heat conductivity_wSpecific heat capacity C_pwThickness of the coating s_bThermal conductivity lambda of the coating_bSpecific heat capacity of coating layer C_pbThickness s of the insulating layer_iInsulating layer heat conductivity lambda_iAnd the specific heat capacity C of the insulating layer 21_piCalculation of thermal resistance R_w. The third model 44 preferably depends on the distance 13, the velocity v of the air_LReference temperature T_eCalculation of thermal resistance R_F. Dependent on the thermal resistance R_bl,R_w,R_FAnd the detected temperature T_waAnd T_eThe calculation module 45 of the evaluation unit 19 calculates the temperature T of the fluid 12, preferably according to the above formula_M。

To calculate the thermal resistance R of the boundary layer 15_blThe first model 42 can advantageously have as input variables the knoop number 47 calculated using the fourth model 46. The knoop number 47 can be calculated with the aid of the fourth model 46, depending also in a particularly preferred variant on the reynolds number 48 calculated with the fifth model 49. The fourth model 46 is preferably differentiated depending on the value setting of the calculated reynolds number 48. Depending on the value of the reynolds number 48, the fourth model 46 can use the above-mentioned calculations of the first, second and/or third model for calculating the knowler number.

The input variables of the interface 41 shown in fig. 4 can be entered manually in a first variant by means of the input interface 31. In a second variant, a large part of the input variables of the interface 41 can be calculated from the database 32 connected to the evaluation unit 19. A special variant of the proposed method provides for detecting, by means of the input interface 31, the description 51 for characterizing the fluid 12 and the material properties of the fluid 12Is determined by means of the description 51. In an advantageous manner, the material properties of the fluid are furthermore dependent on the estimated temperature T of the fluid 12_gTo be measured. Here, the estimated temperature T_gMay be equal to the measured temperature T of the conduit section 11_wa。

Fig. 5 shows a variant in which the sixth model 52 of the evaluation unit 19 depends on the estimated temperature T_gAnd description 51 calculating the density ρ of the fluid 12_fDynamic viscosity eta_fSpecific heat capacity C_pfAnd heat conductivity lambda_f. Tables known in the art can be used for this calculation. A particularly precise form of the proposed method provides that, firstly, at least one substance property is dependent on the estimated temperature T_gTo calculate and to be proximate to the temperature T of the fluid 12_MDepending on the substance properties, are determined according to the method described above. Following this, the improved method is arranged to be based on the measured temperature T of the fluid 12_MAt least one material property of the fluid 12 is recalculated. Calculating the material properties of the fluid 12 based on temperature may be based on [1 ]]And (5) realizing.

FIG. 6 shows that the sixth model 52 depends on the calculated temperature T of the fluid 12_MHow to recalculate the density ρ of the fluid_fDynamic viscosity eta_fSpecific heat capacity C_pfAnd heat conductivity lambda_f. Depending on this recalculated material property of the fluid 12, the temperature T of the fluid 12 can be recalculated by means of the method described above_M. Temperature T of fluid 12_MMay be iteratively performed until the temperature T of the fluid 12 is reached_MIs below a specified threshold. The instructions 51 for the representativeness can be configured, for example, in the form of strings (String), for example "oil". The input interface 31 evaluates the specifications 51 in such a way that the corresponding formula is used to calculate the material properties of the fluid refined by means of the specifications 51, and to calculate the material properties of the fluid 12 that are read out of the material database and used for the calculation.

Reference to the literature

[1]Volker Gnielinski. New equations for heat and mass transfer inturbulent pipe and channel flow. International chemical engineering, AIAAJournal, 16(2):359–368, April 1976.

[2]Volker Gnielinski. Ein neues Berechnungsverfahren für die Wärmeübertragung im Übergangsbereich zwischen laminarer und turbulenter Strömung.Forschung im Ingenieurwesen-Engineering Research, 61(9):240–248, 1995.

[3]VDI-Wärmeatlas. Druckverlust in durchströmten Rohren (section Lab1).Springer-Verlag, Berlin-Heidelberg, 2006

[4]Theodore L. Bergman, Adrienne S. Lavine, and Frank P. Incropera.Fundamentals of Heat and Mass Transfer. John Wiley&Sons, 7th edition, 2011.

[5]Strömungsgesetze in rauhen Rohren, Nikuradse, Forschung auf demGebiet des Ingenieurwesens, 1933, NACA Technical Memorandum 1292.

REFERENCE SIGNS LIST

1 first step

2 second step

3 the third step

4 fourth step

11 duct section

12 fluid

13 pitch

14 surface of

15 boundary layer

16 inner wall of the duct section

17 first temperature sensor

18 second temperature sensor

19 evaluation unit

20 wall

21 insulating layer

22 system

31 input interface

32 database

41 interface

42 first model

43 second model

44 third model

45 computing module

46 fourth model

47 Nussel number

48 Reynolds number

49 fifth model

Description of 51

52 sixth model.