CN108872014B - Method and device for comprehensively representing heat transport properties of fluid material - Google Patents
Method and device for comprehensively representing heat transport properties of fluid material Download PDFInfo
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- CN108872014B CN108872014B CN201810573704.6A CN201810573704A CN108872014B CN 108872014 B CN108872014 B CN 108872014B CN 201810573704 A CN201810573704 A CN 201810573704A CN 108872014 B CN108872014 B CN 108872014B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/18—Investigating or analyzing materials by the use of thermal means by investigating thermal conductivity
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
Abstract
The invention discloses a method and a device for comprehensively representing the heat transport property of a fluid material, wherein the method comprises the following steps: immersing the test wire bent into an arc shape in a tested fluid material; applying a uniform magnetic field outside the measured fluid material; and introducing alternating current with continuously changed frequency to a test line so as to obtain the viscosity coefficient, the thermal conductivity or the thermal diffusivity of the measured fluid material according to the current frequency section. The method can comprehensively measure the thermal conductivity, the thermal diffusivity and the viscosity coefficient of the fluid material under the same working condition, thereby effectively improving the accuracy and the efficiency of measurement, having high integration level, effectively reducing the test cost, and being simple and easy to realize.
Description
Technical Field
The invention relates to the technical field of testing of heat transport properties of fluid materials, in particular to a method and a device for comprehensively representing the heat transport properties of the fluid materials.
Background
At present, the fields of aerospace, electronic science and technology, nuclear industry and the like have urgent needs for improving the heat transfer efficiency, and in engineering, particularly in the design of a heat exchanger, the heat exchange efficiency directly influences the engineering cost, so that the problem of great attention in the current engineering field is solved by finding a material with excellent thermophysical properties and improving the thermophysical properties of the material, and the main parameters for representing the heat transfer performance are the thermal conductivity, the thermal diffusivity and the viscosity coefficient. Thermal conductivity characterizes the ability of a material to transfer heat, thermal diffusivity characterizes the ability of a material to transfer temperature, and viscosity coefficient is an indication and measure of the friction generated by fluid flow against its interior. The fuel and cooling materials used in modern industry are mostly fluids, so accurate measurement of thermal conductivity, thermal diffusivity and viscosity coefficient of fluid materials is of great significance in the assessment of heat transfer capability of fluid materials.
In the related art, most of the methods for measuring the heat transport property of the fluid material are used for independently measuring one parameter, so that the heat transfer capacity of the fluid cannot be comprehensively characterized, and different methods for measuring different properties are adopted, so that additional variables and uncertainty are easily introduced.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art.
Therefore, one objective of the present invention is to provide a method for comprehensively characterizing the heat transport properties of a fluid material, which effectively improves the accuracy and efficiency of measurement, has high integration level, effectively reduces the cost of testing, and is simple and easy to implement.
Another object of the present invention is to provide a device for integrating the thermal transport properties of fluid materials.
In order to achieve the above object, an embodiment of an aspect of the present invention provides a method for comprehensively characterizing the heat transport properties of a fluid material, including the following steps: immersing the test wire bent into an arc shape in a tested fluid material; a uniform magnetic field is applied to the outside of the measured fluid material; and introducing alternating current with continuously changed frequency to the test line so as to obtain the viscosity coefficient, the thermal conductivity or the thermal diffusivity of the measured fluid material according to the current frequency section.
According to the method for comprehensively representing the heat transport property of the fluid material, the test line bent into the arc shape is used as the heating line and the induction line at the same time, so that different properties of the fluid material are measured in different frequency sections, the comprehensive measurement of the heat conductivity, the heat diffusivity and the viscosity coefficient of the fluid material under the same working condition is realized, and the sample transfer is avoided, so that the measurement accuracy and efficiency are effectively improved, the integration level is high, the test cost is effectively reduced, and the method is simple and easy to realize.
In addition, the method for comprehensively characterizing the heat transport properties of the fluid material according to the above embodiment of the present invention may further have the following additional technical features:
further, in an embodiment of the present invention, the obtaining the viscosity coefficient, the thermal conductivity, or the thermal diffusivity of the measured fluid material according to the current frequency band further includes: when the current frequency band is smaller than a first preset frequency band, obtaining the viscosity coefficient of the measured fluid according to the change relation of the induced electromotive force of the test wire along with the frequency; and when the current frequency band is larger than a second preset frequency band, acquiring the thermal conductivity and the thermal diffusivity of the fluid to be measured according to the change relation of the temperature of the hot wire along with time.
Further, in an embodiment of the present invention, wherein the viscosity coefficient is obtained by inverse solution of the following formula:
where 2 δ is the curve half-peak width, Qvac is the quality factor of the hot-wire, ω is the frequency, ρ w is the hot-wire density, k is a function defined by m, ρsM is related to the hot wire radius, sample density and viscosity for the density of the surrounding fluid sample.
Further, in one embodiment of the present invention, the thermal conductivity is obtained by the following formula:
wherein q isvIs the electric power per unit volume of the hot wire, and A is the dimensionless temperature sum obtained after dimensionless numerical simulationThe slope of the linear relationship of the curve of the log Fourier number, a is the slope of the linear relationship of the actual temperature rise and the log time curve measured by the experiment, r0 is the radius of the test line 1, V is the voltage at two ends of the test line 1, I is the current passing through the test line 1, and l is the length of the hot wire.
Further, in one embodiment of the present invention, the thermal diffusivity is obtained by the following formula:
wherein, B is the intercept of the curve linear relation of dimensionless temperature and logarithm Fourier number obtained after dimensionless numerical simulation, and B is the intercept of the curve of the logarithmic change of the temperature rise of the actual measurement test line 1 along with time.
In order to achieve the above object, another embodiment of the present invention provides an apparatus for comprehensively characterizing the heat transport properties of a fluid material, comprising: the immersion module is used for immersing the test wire bent into an arc shape in the tested fluid material; the magnetic field applying module is used for applying a uniform magnetic field outside the measured fluid material; and the measuring module is used for introducing alternating current with continuously changed frequency to the test line so as to obtain the viscosity coefficient, the thermal conductivity or the thermal diffusivity of the measured fluid material according to the current frequency segment.
According to the device for comprehensively representing the heat transport property of the fluid material, the test wire bent into the arc shape is used as the heating wire and the induction wire at the same time, so that different properties of the fluid material are measured at different frequency sections, the comprehensive measurement of the heat conductivity, the heat diffusivity and the viscosity coefficient of the fluid material under the same working condition is realized, and the sample transfer is avoided, so that the measurement accuracy and efficiency are effectively improved, the integration level is high, the test cost is effectively reduced, and the device is simple and easy to realize.
In addition, the device for comprehensively characterizing the heat transport property of the fluid material according to the above embodiment of the invention can also have the following additional technical features:
further, in an embodiment of the present invention, the measuring module is further configured to obtain a viscosity coefficient of the measured fluid according to a change relation of an induced electromotive force of the test wire with frequency when the current frequency band is smaller than a first preset frequency band, and obtain a thermal conductivity and a thermal diffusivity of the measured fluid according to a change relation of a temperature of a hot wire with time when the current frequency band is larger than a second preset frequency band.
Further, in an embodiment of the present invention, wherein the viscosity coefficient is obtained by inverse solution of the following formula:
wherein 2 δ is a curve half-peak width, Qvac is a quality factor of the hot line, ω is a frequency, ρ w is a hot line density, k is a function defined by m, ρsM is related to the hot wire radius, sample density and viscosity for the density of the surrounding fluid sample.
Further, in one embodiment of the present invention, the thermal conductivity is obtained by the following formula:
wherein q isvThe electric power of the hot wire in unit volume is shown as A, the slope of the linear relation of the dimensionless temperature and the logarithm Fourier number obtained after dimensionless numerical simulation is used as A, the slope of the linear relation of the actual temperature rise and the logarithm time curve measured by experiments is used as a slope, r0 is the radius of the test wire 1, V is the voltage at two ends of the test wire 1, I is the current passing through the test wire 1, and l is the length of the hot wire.
Further, in one embodiment of the present invention, the thermal diffusivity is obtained by the following formula:
wherein, B is the intercept of the curve linear relation of dimensionless temperature and logarithm Fourier number obtained after dimensionless numerical simulation, and B is the intercept of the curve of the logarithmic change of the temperature rise of the actual measurement test line 1 along with time.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a flow chart of a method for integrating the characterization of thermal transport properties of a fluid material in accordance with one embodiment of the present invention;
FIG. 2 is a diagram of a physical model for a method of comprehensively characterizing thermal transport properties of a fluid material, in accordance with one embodiment of the present invention;
FIG. 3 is a schematic diagram of a measurement circuit for a method for integrating properties characterizing the thermal transport of a fluid material, in accordance with one embodiment of the present invention;
fig. 4 is a schematic structural diagram of an apparatus for integrating the thermal transport properties of a fluid material in accordance with one embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
The method and apparatus for comprehensively characterizing the heat transport properties of a fluid material according to embodiments of the present invention will be described with reference to the accompanying drawings, and first, the method for comprehensively characterizing the heat transport properties of a fluid material according to embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a flow chart of a method for integrating the characterization of thermal transport properties of a fluid material in accordance with one embodiment of the present invention.
As shown in FIG. 1, the method for comprehensively characterizing the heat transport properties of a fluid material comprises the following steps:
in step S101, the test line bent in an arc shape is immersed in the fluid material to be tested.
It will be appreciated that embodiments of the present invention employ a test wire bent into an arc as both the heater wire and the sense wire, and that the test wire is completely immersed in the fluid material being tested.
In step S102, a uniform magnetic field is applied to the outside of the measured fluid material.
It is understood that the embodiment of the present invention applies a uniform magnetic field to the outside to perform the next action.
In step S103, an alternating current with continuously changing frequency is applied to the test line to obtain the viscosity coefficient, thermal conductivity, or thermal diffusivity of the measured fluid material according to the current frequency segment.
It can be understood that the embodiment of the invention obtains different properties of the fluid material by measuring at different frequency sections by passing an alternating current with continuously changing frequency to the hot wire.
Further, in an embodiment of the present invention, obtaining the viscosity coefficient, the thermal conductivity, or the thermal diffusivity of the measured fluid material according to the current frequency band further includes: when the current frequency band is smaller than a first preset frequency band, obtaining the viscosity coefficient of the measured fluid according to the change relation of the induced electromotive force of the test wire along with the frequency; and when the current frequency band is larger than a second preset frequency band, acquiring the thermal conductivity and the thermal diffusivity of the measured fluid according to the change relation of the temperature of the hot wire along with time.
It can be understood that, in a low frequency band, because the hot wire is in a magnetic field, the alternating current applies a force with a periodically changed direction to the hot wire, so that the hot wire generates vibration, the vibration amplitude is related to the viscosity of the medium, and the viscosity coefficient of the measured fluid can be deduced from the relation that the induced electromotive force of the test wire changes along with the frequency. In a high-frequency range, the vibration effect is ignored, the main phenomenon of the hot wire is that the resistance thermal effect is generated so that the temperature is raised, after the temperature difference exists between the hot wire and the surrounding medium, the medium takes away heat from the hot wire through heat conduction, and therefore the heat conduction capability of the surrounding medium, namely the heat conductivity and the heat diffusivity of the fluid material can be obtained by measuring the change relation of the temperature of the hot wire along with time after the power is on.
Specifically, as shown in fig. 2, the embodiment of the present invention aims to comprehensively measure the heat transport property of a sample 3 to be measured, and obtains the viscosity coefficient by measuring the induced electromotive force generated by cutting the magnetic induction wire by vibration of the test wire 1 in the low frequency band, and obtains the thermal conductivity and thermal diffusivity of the medium by measuring the change relationship of the temperature rise of the test wire 1 generated by the resistance thermal effect with time in the high frequency band, and the division of the low frequency band and the high frequency band is determined by the parameters of the overlapping hot wire. For example, a platinum wire with a length of 20mm and a diameter of 50 μm is used as the test wire 1, the resonance frequency is 300Hz, the low-frequency span is set to be 0.01Hz to three times of the resonance frequency, the purpose is to completely measure the half-peak width of the frequency-induced electromotive force relationship curve of the test wire 1, the high-frequency parameter is set to be greater than 5000Hz, and the temperature rise-time curve of the test wire 1 is judged to have no obvious fluctuation according to the measurement.
For example, the embodiment of the present invention may be tested by using the experimental apparatus shown in fig. 2, where the test line 1 is overlapped in a semicircular shape, two ends of the test line are respectively connected to the heat sink 21 and the heat sink 22, the test line is placed in the liquid 3 to be tested, and the magnetic poles 41 and 42 provide uniformly distributed magnetic fields parallel to the plane where the test line is located. The details of the test lines at different frequencies are described below.
Further, in one embodiment of the present invention, wherein the viscosity coefficient is obtained by inverse solution of the following formula:
where 2 δ is the curve half-peak width, Qvac is the quality factor of the hot-wire, ω is the frequency, ρ w is the hot-wire density, k is a function defined by m, ρsM is related to the hot wire radius, sample density and viscosity for the density of the surrounding fluid sample.
It can be understood that, as shown in fig. 2, alternating current with continuously changing frequency is supplied to the test wire 1 from the alternating current power supply, and the applied direction in the test wire 1 is continuously changed under the action of the magnetic field in the low frequency bandChanging the force so that the test wire 1 vibrates in the direction perpendicular to the magnetic field, the test wire 1 vibrates to cut the magnetic induction wire to generate induced electromotive force, the differential preamplifier and the oscilloscope measure the induced electromotive force generated by the test wire 1 under different frequencies to obtain a frequency-induced electromotive force curve, and the half-peak width formula of the curve
The viscosity coefficient of the fluid material is solved back. Wherein QvacIs the quality factor of the hot line, 2 δ is the curve half-peak width, ω0Is the resonant frequency, p, of the test line 1wIs the density of test line 1, r0Is the radius of the test line 1, and D and c' are functions of the viscosity coefficient.
Specifically, as shown in fig. 2, the Pt line is used as a test line 1, bent into a semicircular lap joint, and both ends of the Pt line are lapped on a heat sink and immersed in a sample 3 to be tested, and the magnetic field is uniformly distributed in a local space parallel to the Pt line.
The power lets in alternating current signal, measures the viscosity coefficient of the sample 3 that awaits measuring at the low frequency stage, after reaching the steady state, carries out the atress analysis to test wire 1, by newton's second law:
wherein, the atress is magnetic field force, viscous drag, internal friction and restoring force respectively:
Fmagnetic＝[Io(x)×B]sin(ωt)，
namely, it is
Wherein, I0Current amplitude, B magnetic field strength, Y Young's modulus, r0Is the hot wire radius, ρwFor the density of the hot wire D, C' is a function derived from the Stokes flow equation for the density and viscosity of the liquid to be measured, QvacIs a quality factor.
The above formula is resolved into:
wherein the content of the first and second substances,
D＝πr0 2ωρsk'，
C'＝πr0 2ρsk，
the induced electromotive force is thus solved by the following analytical formula:
the remaining chord components are such that,
the above equation gives a resonance curve with a half-wave width equal to 2 δ, and viscosity η can be inversely solved by applying the following equation:
further, in one embodiment of the present invention, the thermal conductivity is obtained by the following formula:
wherein q isvThe electric power of a unit volume of the hot wire is shown as A, the slope of the linear relation of the dimensionless temperature and the logarithm Fourier number obtained after dimensionless numerical simulation is used as A, the slope of the linear relation of the actual temperature rise and the logarithm time curve measured by experiments is used as a slope, r0 is the radius of the test wire 1, V is the voltage at two ends of the test wire 1, I is the current passing through the test wire 1, and l is the length of the hot wire.
Further, in one embodiment of the present invention, the thermal diffusivity is obtained by the following formula:
wherein, B is the intercept of the curve linear relation of dimensionless temperature and logarithm Fourier number obtained after dimensionless numerical simulation, and B is the intercept of the curve of the logarithmic change of the temperature rise of the actual measurement test line 1 along with time.
It will be appreciated that the vibration of the high band test wire 1 is negligible and that the test wire 1 acts as a heater wire to generate a high temperature end, and that heat is transferred by the fluid material 3 to be measured in a radial direction by thermal conduction to a portion of the medium 3 that is further from the hot wire. Meanwhile, the test wire 1 is also used as an induction wire, the change relation of the resistance of the test wire along with time is measured by the differential preamplifier matched with an oscilloscope, and the formula R is usedT＝R0[1+βT(T-T0)]The temperature of the test line 1 can be derived from the time curve
Determining the thermal conductivity of the measured fluid material according to the formula
To determine the thermal diffusivity of the measured fluid material. Wherein V is the voltage at two ends of the test line 1, I is the current passing through the test line 1, A is the slope of the temperature rise logarithmic change curve with time obtained by carrying out dimensionless numerical simulation on the parameters of the test line 1, a is the slope of the temperature rise logarithmic change curve with time actually measured for the test line 1, r0The radius of the test line 1, B is the intercept of the temperature rise logarithmic change curve with time obtained by carrying out dimensionless numerical simulation on the parameters of the test line 1, B is the intercept of the temperature rise logarithmic change curve with time actually measured on the test line 1, R is the intercept of the temperature rise logarithmic change curve with time actually measured on the test line 10To test the resistance of line 1 at a temperature of 0 deg.C (273.15K), RTTo test the resistance of line 1 at temperature T deg.C, βTThe temperature coefficient of resistance of line 1 was measured.
Specifically, when the frequency of the ac power supply is high frequency, the measurement result is used to obtain the thermal conductivity and thermal diffusivity of the sample 3 to be measured. The process of measuring thermal conductivity and thermal diffusivity belongs to transient measurement, and the physical model of the test line 1 at this time is as follows:
wherein r is0Is the radius of the platinum wire, rho, c and lambda are the physical parameters of the platinum wire, namely the density, the specific heat capacity and the thermal conductivity, q is the electric power per unit length, r isxIs the width of the container holding the sample.
The heat source of the unit volume of the platinum wire is constant, the thermal conductivity and the thermal diffusivity of the parameters to be measured are reflected in the relative change relation of the temperature rise of the hot wire along with time, and the resistance and the temperature of the platinum wire have a linear relation:
RT＝R0[1+βT(T-T0)]，
wherein, βTThe resistance temperature coefficient is obtained by fitting a plurality of groups of resistance values measured by changing the ambient temperature when the temperature is T; r0Is the resistance, T, of the test line at a temperature of 0 deg.C (273.15K)0And 273.15K.
And carrying out numerical simulation after the equation is subjected to dimensionless operation to obtain the relative relation between dimensionless temperature and Fourier number, and comparing the relative relation between the absolute temperature rise and the time of the experiment to obtain the thermal conductivity and the thermal diffusivity of the sample 3 to be measured.
The linear relation of the curves of the dimensionless temperature and the logarithm Fourier number obtained after the dimensionless numerical simulation is as follows:
θv＝AlnFo+B，
the linear relation between the actual temperature rise and the logarithmic time curve measured by the experiment is as follows:
ΔT＝alnt+b，
contrast development gives:
wherein A is the slope of the linear relationship between dimensionless temperature and logarithmic Fourier number, B is the intercept of the linear relationship between dimensionless temperature and logarithmic Fourier number, a is the slope of the linear relationship between actual temperature rise and logarithmic time, and r is the intercept of the linear relationship between actual temperature rise and logarithmic time, and0the radius of the test line 1, V the voltage across the test line 1, I the current through the test line 1, and l the hot wire length.
The experimental procedures of the method for comprehensively characterizing the heat transport properties of the fluid material will be described in detail below.
As shown in figure 3, the measuring circuit of the viscosity coefficient, the thermal conductivity and the thermal diffusivity is composed of an alternating current power supply 5, a test wire 1 and a standard resistor 6 to form a closed loop. In a low frequency range, the test wire 1 is vibrated by introducing alternating current into a magnetic field, so that a magnetic induction wire is cut to generate induced electromotive force, the amplitude and the phase of the voltage at two ends of the test wire 1 and the standard resistor 6 are acquired by a dual-channel oscilloscope 9 after the voltage is acquired by the high-precision digital differential preamplifier 8, and the induced electromotive force generated on the test wire 1 can be obtained after vector difference is carried out on the resistance value of the standard resistor 6 because the resistance value of the standard resistor 6 does not change, so that induced electromotive force curves under different frequencies can be obtained, and the viscosity coefficient can be further obtained. In a high-frequency section, the test wire 1 generates heat through electric heating, voltage effective values at two ends of the test wire 1 and the standard resistor 6 are acquired through a double channel of the oscilloscope 9 after voltage is acquired through the high-precision digital differential preamplifier 8, and therefore a relation curve of the resistance of the test wire 1 changing along with time is obtained. The method is named as a harmonic hot wire method because harmonic waves are used as a current source and short hot wires are used as a detector for measurement.
Measurement circuit as shown in fig. 3, the whole experiment proceeds as follows:
(1) estimating the viscosity coefficient of a sample to be tested, determining the output power and the magnetic field intensity of an alternating current power supply, determining the geometric dimension matching of a test line 1 and a material to be tested, and overlapping the test line 1;
(2) placing the experimental device in a normal temperature and normal pressure environment, and applying a uniformly distributed magnetic field;
(3) after the ambient temperature is stable, entering a measuring link;
the method comprises the following steps: the circuits are connected as per fig. 2.
Step two: and configuring the output frequency and amplitude of the alternating current power supply 5, and configuring a differential preamplifier 8 and an oscilloscope 9 to acquire parameters.
Step three: and (3) turning on an alternating current power supply 5 to introduce alternating current into the test line 1, and acquiring the voltage amplitude and the phase at two ends of the test line 1 and the standard resistor 6 under the current frequency through a high-precision digital differential preamplifier 8 and an oscilloscope 9.
Step four: and after the current frequency acquisition is finished, changing the frequency and repeating the measurement process again.
Step five: when the frequency of the alternating current power supply 5 is increased to high frequency, the output amplitude of the alternating current power supply 5 is reconfigured, and a differential preamplifier 8 and an oscilloscope 9 are configured to acquire parameters.
Step six: and (3) turning on an alternating current power supply 5 to introduce alternating current into the test line 1, and acquiring voltage effective values at two ends of the test line 1 and the standard resistor 6 under the current frequency through a high-precision digital differential preamplifier 8 and an oscilloscope 9.
Step seven: and after the experiment is finished, exporting the acquired data for post-processing, and turning off the power supply and the acquisition instrument.
In summary, the embodiment of the invention can comprehensively measure the thermal conductivity, thermal diffusivity and viscosity coefficient of the fluid material under the same working condition, avoid sample transfer, improve efficiency and accuracy, innovate the method for measuring the viscosity coefficient and the method for measuring the thermal conductivity and the thermal diffusivity, avoid using too many measuring instruments, have very high integration characteristic, and have the advantages of high measuring precision, easy realization, low testing cost and the like.
According to the method for comprehensively representing the heat transport property of the fluid material, provided by the embodiment of the invention, the test lines bent into the arc shape are simultaneously used as the heating lines and the induction lines to measure different properties of the fluid material at different frequency sections, so that the comprehensive measurement of the heat conductivity, the heat diffusivity and the viscosity coefficient of the fluid material under the same working condition is realized, and the sample transfer is avoided, thereby effectively improving the measurement accuracy and efficiency, having high integration level, effectively reducing the test cost, and being simple and easy to realize.
Next, an apparatus for comprehensively characterizing the heat transport properties of a fluid material according to an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 4 is a schematic diagram of the structure of an apparatus for integrating the thermal transport properties of a fluid material, in accordance with one embodiment of the present invention.
As shown in fig. 4, the apparatus 10 for comprehensively characterizing the heat transport properties of a fluid material comprises: an immersion module 100, a magnetic field application module 200, and a measurement module 300.
The immersion module 100 is used for immersing the test line bent into an arc shape in the tested fluid material. The magnetic field applying module 200 is used for applying a uniform magnetic field outside the measured fluid material. The measuring module 300 is configured to apply an alternating current with continuously changing frequency to a test line, so as to obtain a viscosity coefficient, a thermal conductivity, or a thermal diffusivity of the measured fluid material according to the current frequency segment. The device 10 of the embodiment of the invention can comprehensively measure the thermal conductivity, the thermal diffusivity and the viscosity coefficient of the fluid material under the same working condition, thereby effectively improving the accuracy and the efficiency of measurement, having high integration level, effectively reducing the test cost and being simple and easy to realize.
Further, in an embodiment of the present invention, the measuring module 300 is further configured to obtain a viscosity coefficient of the measured fluid according to a change relation of induced electromotive force of the test wire with frequency when the current frequency band is smaller than a first preset frequency band, and obtain thermal conductivity and thermal diffusivity of the measured fluid according to a change relation of temperature of the hot wire with time when the current frequency band is larger than a second preset frequency band.
Further, in one embodiment of the present invention, wherein the viscosity coefficient is obtained by inverse solution of the following formula:
wherein 2 δ is a curve half-peak width, Qvac is a quality factor of the hot line, ω is a frequency, ρ w is a hot line density, k is a function defined by m, ρsM is related to the hot wire radius, sample density and viscosity for the density of the surrounding fluid sample.
Further, in one embodiment of the present invention, the thermal conductivity is obtained by the following formula:
wherein q isvThe electric power of a unit volume of the hot wire is shown as A, the slope of the linear relation of the dimensionless temperature and the logarithm Fourier number obtained after dimensionless numerical simulation is used as A, the slope of the linear relation of the actual temperature rise and the logarithm time curve measured by experiments is used as a slope, r0 is the radius of the test wire 1, V is the voltage at two ends of the test wire 1, I is the current passing through the test wire 1, and l is the length of the hot wire.
Further, in one embodiment of the present invention, the thermal diffusivity is obtained by the following formula:
wherein, B is the intercept of the curve linear relation of dimensionless temperature and logarithm Fourier number obtained after dimensionless numerical simulation, and B is the intercept of the curve of the logarithmic change of the temperature rise of the actual measurement test line 1 along with time.
It should be noted that the foregoing explanation of the embodiment of the method for comprehensively characterizing the heat transport properties of a fluid material also applies to the apparatus for comprehensively characterizing the heat transport properties of a fluid material of this embodiment, and will not be described herein again.
According to the device for comprehensively representing the heat transport property of the fluid material, provided by the embodiment of the invention, the test wires bent into the arc shape are simultaneously used as the heating wires and the induction wires to measure different properties of the fluid material at different frequency sections, so that the comprehensive measurement of the heat conductivity, the heat diffusivity and the viscosity coefficient of the fluid material under the same working condition is realized, and the sample transfer is avoided, thereby effectively improving the measurement accuracy and efficiency, having high integration level, effectively reducing the test cost, and being simple and easy to realize.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (8)
1. A method for comprehensively characterizing the heat transport properties of a fluid material, comprising the steps of:
immersing the test wire bent into an arc shape in a tested fluid material;
applying a uniform magnetic field outside the measured fluid material; and
introducing alternating current with continuously changed frequency to the test line so as to obtain the viscosity coefficient, the thermal conductivity or the thermal diffusivity of the measured fluid material according to the current frequency segment, wherein the obtaining of the viscosity coefficient, the thermal conductivity or the thermal diffusivity of the measured fluid material according to the current frequency segment further comprises: when the current frequency band is smaller than a first preset frequency band, obtaining the viscosity coefficient of the fluid material to be measured according to the change relation of the induced electromotive force of the test wire along with the frequency; and when the current frequency band is larger than a second preset frequency band, acquiring the thermal conductivity and the thermal diffusivity of the measured fluid material according to the change relation of the temperature of the test line along with time.
2. The method for comprehensively characterizing thermal transport properties of a fluid material according to claim 1, wherein the viscosity coefficient is obtained by solving inversely the following equation:
where 2 δ is the curve half-peak width, Qvac is the quality factor of the test line, ω is the frequency, ρwFor testing the linear density, k is a function defined by m, psM is the density of the surrounding fluid sample and is related to the test line radius, sample density and viscosity.
3. The method for comprehensively characterizing the heat transport properties of a fluid material according to claim 1 or 2, characterized in that the thermal conductivity is obtained by the following formula:
wherein q isvFor testing electric power in unit volume of line, A is dimensionless temperature and logarithmic Fourier number obtained by numerical simulationA is the slope of the linear relationship between the actual temperature rise and the logarithmic time curve measured by the experiment, r0 is the radius of the test line 1, V is the voltage at two ends of the test line 1, I is the current passing through the test line 1, and l is the length of the test line.
4. The method for comprehensively characterizing thermal transport properties of a fluid material according to claim 3, wherein said thermal diffusivity is obtained by the following formula:
wherein, B is the intercept of the curve linear relation of dimensionless temperature and logarithm Fourier number obtained after dimensionless numerical simulation, and B is the intercept of the curve of the logarithmic change of the temperature rise of the actual measurement test line 1 along with time.
5. An apparatus for integrating the thermal transport properties of a fluid material, comprising:
the immersion module is used for immersing the test wire bent into an arc shape in the tested fluid material;
the magnetic field applying module is used for applying a uniform magnetic field outside the measured fluid material; and
the measuring module is used for introducing alternating current with continuously changed frequency to the test line so as to obtain the viscosity coefficient, the thermal conductivity or the thermal diffusivity of the measured fluid material according to the current frequency segment, wherein the measuring module is further used for obtaining the viscosity coefficient of the measured fluid material according to the change relation of the induced electromotive force of the test line along with the frequency when the current frequency segment is smaller than a first preset frequency segment, and obtaining the thermal conductivity and the thermal diffusivity of the measured fluid material according to the change relation of the temperature of the test line along with the time when the current frequency segment is larger than a second preset frequency segment.
6. The apparatus for comprehensively characterizing thermal transport properties of fluid materials of claim 5, wherein the viscosity coefficient is obtained by solving the following formula inversely:
where 2 δ is the curve half-peak width, Qvac is the quality factor of the test line, ω is the frequency, ρ w is the test line density, k is a function defined by m, ρsM is the density of the surrounding fluid sample and is related to the test line radius, sample density and viscosity.
7. The apparatus for comprehensively characterizing the heat transport properties of a fluid material according to claim 5 or 6, wherein the thermal conductivity is obtained by the following formula:
wherein q isvThe method is characterized in that the method is used for testing electric power of a test line in unit volume, A is the slope of the linear relation of a dimensionless temperature curve and a logarithmic Fourier number obtained after dimensionless numerical simulation, a is the slope of the linear relation of an actual temperature rise curve and a logarithmic time curve measured by experiments, r0 is the radius of the test line 1, V is the voltage at two ends of the test line 1, I is the current passing through the test line 1, and l is the length of the test line.
8. The apparatus for comprehensively characterizing the heat transport properties of a fluid material according to claim 7, wherein said thermal diffusivity is obtained by the following formula:
wherein, B is the intercept of the curve linear relation of dimensionless temperature and logarithm Fourier number obtained after dimensionless numerical simulation, and B is the intercept of the curve of the logarithmic change of the temperature rise of the actual measurement test line 1 along with time.
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| A switched vibrating-hot-wire method for measuring the viscosity and thermal conductivity of liquids;Fengyi Li 等;《Review of Scientific Instruments》;20190710;第90卷(第7期);第075105（1-7）页 * |
| Viscosity measurements of hydrogen at high temperatures up to 573K by a curved vibrating wire method;N.Sakoda 等;《The Journal of Chemical Thermodynamics》;20150502;第89卷;第22-26页 * |
| 微纳米尺度材料热物性表征与热输运机理研究;王照亮;《中国博士学位论文全文数据库工程科I辑》;20071015(第4期);第19-24、52-71页 * |
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