A kind of heat conducting coefficient measurement deviceTechnical field
The present invention relates to a kind of determinator of coefficient of heat conductivity, particularly measures the determinator of the coefficient of heat conductivity of solid material.
Background technology
The coefficient of heat conductivity of material is an important parameter index of research material physical property, and in scientific research, teaching, the departments such as production all require to predict the coefficient of heat conductivity of material or survey.Coefficient of heat conductivity is the physical quantity of reflection material conducts heat performance, it is not only the foundation of the calorifics of evaluating material, and be the design considerations of material when applying, so the mensuration of the coefficient of heat conductivity of material is become to the key of exploitation new material in scientific experiment and engineering.
The coefficient of heat conductivity of current measurement material mainly contains following three kinds of methods:
One, laser shines method.What the method adopted is Transient Method, principle is that beam of laser is beaten at sample upper surface, by the temperature variation of infrared detector test lower surface, the actual data recorded are thermal diffusivities of sample, by with the density and the specific heat that obtain sample while standard model, the coefficient of heat conductivity of sample can be calculated by formula.The method advantage measures fast, adopts eyes with non-contact method, be applicable to high temperature, the sample of high heat conduction, but be not suitable for sandwich construction, coating, foam, liquid, anisotropic material etc.Reason be laser method test be thermal diffusivity, mathematic(al) mode is based upon on the basis of isotropic material.In addition, also need to record density with additive method, could convert as coefficient of heat conductivity, add the source of error.
Two, coefficient of heat conductivity method.What the method adopted is Transient Method equally, and principle utilizes thermal resistive materials---nickel makes the probe of a plane, simultaneously as thermal source and temperature sensor.The relation of the thermal resistivity of nickel and temperature and resistance is linear, and the change namely by understanding resistance can know the loss of heat, thus the heat conductivility of reflection sample.By recording the response time of temperature and probe, these characteristics of material can be calculated.Can directly obtain coefficient of heat conductivity and thermal diffusion coefficient by mathematical model, both ratio obtains volume specific heat.Advantage is quick, convenient, need not sample preparation especially, can be used for original position/one side test, be applicable to polytype samples such as solid, powder, liquid, coating, cellular material, but be subject to the restriction of detecting head surface coating, temperature range can only to 700 DEG C, and probe cost is higher, design is complicated, can not effectively promote.
Three, temperature gradient method.The method is placed between thermal source and cryogenic refrigerating unit by testing sample, when Temperature Distribution reach stable after, by measuring the parameters such as the heat flux that flows through sample and thermograde, calculate the coefficient of heat conductivity of material.Ideally, all heats of thermal source are passed to cryogenic refrigeration end by testing sample, in fact can inevitably shed from other direction by some heat, this inevitably causes there is thermograde in the xsect of same sample, thus cause measuring error, reduce the accuracy of measuring.Meanwhile, certainly exist thermal contact resistance at testing sample and between thermal source and cold junction, thus cause the inaccurate of measurement data.Therefore, the method measuring accuracy depends primarily on two aspects: on the one hand, how to reduce heat and sheds from other direction in transmittance process; On the other hand, thermal contact resistance is reduced.At present, from document both domestic and external, generally can use thermal insulation material as heat insulation layer in order to be hedged off from the outer world by thermal source, reduce the loss of heat as far as possible, but still have partial heat and outwards conduct, the precision how improving detection in this case becomes technical problem underlying.The theoretical foundation of the method is Fourier Heat Conduction law, described in (1).
Wherein, A: sample to be tested is perpendicular to the cross-sectional area on direction of heat flow;
H: sample to be tested is being parallel to the thickness on direction of heat flow;
by the heat flux of cross-sectional area A in unit interval;
T1: seaming chuck lower surface central temperature;
T2: push-down head upper surface central temperature;
λ: sample to be tested is at temperature (T1+ T2coefficient of heat conductivity during)/2;
Negative sign represents that direction of heat flow is contrary with thermograde direction.
In formula (1), λ is amount to be asked,a, H, T1and T2for unknown quantity, whereinmeasurement be the most difficult, other several amounts can directly be measured.
Under ideal conditions, namely determinator under adiabatic conditions, and the heating power of hot junction heating system issize, but can inevitably shed from other direction by some heat in practical situations both, this inevitably causes there is thermograde in the xsect of same sample.
Meanwhile, certainly exist thermal contact resistance at testing sample and between thermal source and cold junction, thus cause the inaccurate of measurement data.
Summary of the invention
For the deficiencies in the prior art, in order to improve the accuracy of test device of thermal conductivity coefficient, the present invention designs a kind of new solid material heat conductivity determinator, overcomes that the error that exists in prior art is large, complicated operation, accuracy is low and cost is high shortcoming.
Technical scheme of the present invention is: a kind of heat conducting coefficient measurement device, and this device comprises: test chamber 9, hot junction heating system 10, cold junction cooling system 14, pumped vacuum systems 12, temperature acquisition system 13, control pressurer system 11; Arrange a test board 15 in test chamber, test board entirety is up-down structure, is followed successively by heat block 8, push-down head 7, sample to be tested 5, seaming chuck 2, cooling block 1 from bottom to top; Arrange temperature probe group 3 on described upper and lower pressure head surface, temperature probe connects described temperature acquisition and disposal system 13; Described heat block 8 is connected with hot junction heating system 10, and described cooling block 1 is connected with cold junction cooling system 14, and temperature acquisition and disposal system 13 in good time data acquisition, online process and test result export; Described temperature probe group 3 is the first group of temperature probe, second group of sensor and the 3rd group of sensor that vertically pressure head cross-sectional direction are arranged respectively, wherein, first group of temperature probe is three the first point for measuring temperature 3-A, the second point for measuring temperature 3-B and the 3rd point for measuring temperature 3-C radially uniform in same plane, and second group identical with first group of temperature probe with the 3rd group of temperature probe set-up mode.
The temperature value that each for upper push-down head three groups of temperature probes are surveyed processes by described temperature acquisition and disposal system 13, calculates coefficient of heat conductivity after matching.
According to fourier law, described in (2).
Qloose=λ0× Δ T (2)
Wherein, Qloose: the heat that upper push-down head is given out by surrounding;
λ0: the coefficient of heat conductivity of the material that upper push-down head uses;
Δ T: the thermograde measured by temperature probe.
In formula (2), λ0for determining parameter, Δ T is detectable thermograde.Function thus, can obtain Qloosea manifold, carry out data fitting by gained manifold, a Q can be obtainedloosefitting function.
Compared with prior art, use the material of known coefficient of heat conductivity to make upper push-down head as long as the invention has the beneficial effects as follows, just can obtain Q accuratelyloosenumerical value, thus record more accuratelymeasure the coefficient of heat conductivity of sample further more accurately.
Arrange a spacing ring 4 between push-down head on described, the material of described spacing ring is the stupalith of high insulating effect, and shape is annular, has an inward flange.One high thermal conductivity flexible thin slice 16 is set respectively between described sample to be tested and upper push-down head.Described high thermal conductivity flexible thin slice is made up of material with carbon element and binding material, and the thickness of thin slice is 10 μm of-1mm.Described material with carbon element is one or more in carbon nano-tube, carbon fiber, Graphene, and described binding material is high-termal conductivity organic high molecular polymer.Described material with carbon element is regularly arranged in thin slice, and a-b direction of principal axis is substantially identical with heat transfer direction.Described test chamber 9 is connected with pumped vacuum systems, can bear the vacuum tightness reaching 10Pa under air-tight state.In described test board 15 periphery, heat-insulation material layer 6 is set.
The present invention arranges the Transverse Temperature Gradient of simulating sample to be tested by the horizontal multiple spot of point for measuring temperature, is objectively responded the heat transfer characteristic of sample to be tested by the test of multi-point temp, by drawing more objectively coefficient of heat conductivity numerical value after data processing.Meanwhile, the present invention arranges high thermal conductivity flexible thin slice between sample to be tested and pressure head, reduces thermal contact resistance, improves the accuracy of test number.In addition, the present invention arranges spacing ring between pressure head, with ensure test flexible sample time test operability and degree of accuracy.The present invention substantially increases accuracy and the objectivity of Determination of conductive coefficients.
Accompanying drawing explanation
Fig. 1 is heat conducting coefficient measurement device System's composition figure
Fig. 2 is test surfaces temperature sensor distribution plan
Fig. 3 is spacing ring structure figure
Fig. 4 is thermal sheet cut-away view
Wherein, Reference numeral, 1 cooling block, 2 seaming chucks, 3 temperature probe groups, 3-A first point for measuring temperature, 3-B second point for measuring temperature, 3-C the 3rd point for measuring temperature, 4 spacing rings, 5 samples to be tested, 6 heat-insulation material layers, 7 push-down heads, 8 heat blocks, 9 test chambers, 10 hot junction heating systems, 11 control pressurer systems, 12 pumped vacuum systems, 13 temperature acquisitions and disposal system, 14 cold junction cooling systems, 15 test boards, 16 high thermal conductivity flexible thin slices
Embodiment one
Rigid material heat conducting coefficient measurement device, is characterized in that: this device comprises: test chamber 9, hot junction heating system 10, cold junction cooling system 14, pumped vacuum systems 12, temperature acquisition system 13, control pressurer system 11; Arrange a test board 15 in test chamber, test board entirety is up-down structure, is followed successively by heat block 8, push-down head 7, sample to be tested 5, seaming chuck 2, cooling block 1 from bottom to top; Arrange temperature probe group 3 on described upper and lower pressure head surface, temperature probe connects described temperature acquisition and disposal system 13; Described heat block 8 is connected with hot junction heating system 10, and described cooling block 1 is connected with cold junction cooling system 14, and temperature acquisition and disposal system 13 in good time data acquisition, online process and test result export; The set-up mode of described point for measuring temperature for arrange three along radial direction is equidistant in xsect; Described test chamber 9 is connected with pumped vacuum systems, can bear the vacuum tightness reaching 10pa under air-tight state.In described test board 15 periphery, heat-insulation material layer 6 is set.
For rigid material, minimum in upper push-down head pressurization time variation amount, the surfaceness of sample to be tested is different, when upper push-down head and sample contacts to be tested, contact area is not quite similar, certain thermal contact resistance is there is between surface of contact, the existence of thermal contact resistance causes test result to there is error, in order to the test result of coefficient of heat conductivity can be obtained more accurately, the present invention first novelty a high thermal conductivity flexible thin slice 16 is set respectively between described sample to be tested and upper push-down head, described high thermal conductivity flexible thin slice is made up of material with carbon element and binding material, the thickness of thin slice is 1mm.Described graphene material, binding material is high-termal conductivity organic siliconresin, and described material with carbon element is regularly arranged in thin slice, and a-b direction of principal axis is substantially identical with heat transfer direction.
The thermal conductivity of high thermal conductivity flexible material own is high on the one hand, instantaneously heat can be delivered to adjacent medium, high thermal conductivity flexible material has certain flexibility and toughness on the other hand, when upper push-down head applies certain pressure, flexible material generation deformation, can contact with pressure head with sample to be tested more closely, thus eliminate the thermal contact resistance because surfaceness causes.
In addition, inventor finds owing to cannot reach desirable adiabatic condition, thermograde is there is in sample cross to be tested, this causes the temperature of diverse location in xsect incomplete same, traditional means of testing only longitudinally lays point for measuring temperature in center, the real heat flux by testing sample cannot be recorded, this causes the accuracy of testing to decline, the real thermal conductivity value of reaction that cannot be objective and accurate, in order to solve this technical matters, the employing xsect multiple spot of the invention arranges the mode of point for measuring temperature, in xsect, center arranges the first point for measuring temperature (3-A), at radius point midway, the second point for measuring temperature (3-B) is set, in outer rim, the 3rd point for measuring temperature (3-C) is set, three points for measuring temperature are conveniently set and dispersible setting, also can as required concentrated setting in a radius.The each three groups of points for measuring temperature of push-down head are in like manner set.The Temperature numerical that often group three points for measuring temperature collect objectively can react the thermograde of xsect.
According to fourier law, described in (2).
Qloose=λ0× Δ T (2)
Wherein, Qloose: the heat that upper push-down head is given out by surrounding;
λ0: the coefficient of heat conductivity of the material that upper push-down head uses;
Δ T: the thermograde measured by temperature probe.
In formula (2), λ0for determining parameter, Δ T is detectable thermograde.Function thus, can obtain Qloosea manifold, carry out data fitting by gained manifold, a Q can be obtainedloosefitting function.
Compared with prior art, use the material of known coefficient of heat conductivity to make upper push-down head as long as the invention has the beneficial effects as follows, just can obtain Q accuratelyloosenumerical value, thus record more accuratelymeasure the coefficient of heat conductivity of sample further more accurately.
Embodiment two
Flexible material heat conducting coefficient measurement device, is characterized in that: this device comprises: test chamber 9, hot junction heating system 10, cold junction cooling system 14, pumped vacuum systems 12, temperature acquisition system 13, control pressurer system 11; Arrange a test board 15 in test chamber, test board entirety is up-down structure, is followed successively by heat block 8, push-down head 7, sample to be tested 5, seaming chuck 2, cooling block 1 from bottom to top; Arrange temperature probe group 3 on described upper and lower pressure head surface, temperature probe connects described temperature acquisition and disposal system 13; Described heat block 8 is connected with hot junction heating system 10, and described cooling block 1 is connected with cold junction cooling system 14, and temperature acquisition and disposal system 13 in good time data acquisition, online process and test result export; The set-up mode of described point for measuring temperature for arrange three along radial direction is equidistant in xsect; Described test chamber 9 is connected with pumped vacuum systems, can bear the vacuum tightness reaching 10Pa under air-tight state.In described test board 15 periphery, heat-insulation material layer 6 is set.
The present inventor finds to there is thermograde in sample cross to be tested, this causes the temperature of diverse location in xsect incomplete same, traditional means of testing only longitudinally lays point for measuring temperature in center, this causes the accuracy of testing to decline, the real thermal conductivity value of reaction that cannot be objective and accurate, in order to solve this technical matters, the employing xsect multiple spot of the invention arranges the mode of point for measuring temperature, in xsect, center arranges the first point for measuring temperature (3-A), at radius point midway, the second point for measuring temperature (3-B) is set, in outer rim, the 3rd point for measuring temperature (3-C) is set, three points for measuring temperature are conveniently set and dispersible setting, also can as required concentrated setting in a radius.After the setting of three points for measuring temperature, the Temperature numerical collected objectively can react the situation in temperature field in xsect, more accurate by the thermal conductivity value of adding up three Temperature numerical and draw after matching.
When testing flexible material coefficient of heat conductivity, because flexible material, when upper push-down head applies suitable pressure, larger distortion can occur, can cause pressure head cannot align center sample to be tested in extreme circumstances, even can occur when sample deformations amount is large sample to be tested by from push-down head extrude, cause fixing.In order to address this problem, the present invention arranges a spacing ring 4 between push-down head on described, and the material of described spacing ring is the stupalith of high insulating effect, and shape is annular, has an inward flange.The diameter of the inward flange of this spacing ring is slightly less than the diameter of pressure head, the external diameter of spacing ring is slightly larger than the diameter of pressure head, the inward flange height of spacing ring is slightly less than the height of standard sample to be tested, this spacing ring is first placed in push-down head, put into sample to be tested again, the pressurization of operation seaming chuck, contacts with spacing ring inward flange according to pressure controller FEEDBACK CONTROL pressure head, starts afterwards to carry out subsequent detection flow process.
TP215 heat conductive silica gel pad is made 16 samples that thickness is 1mm, take coefficient of heat conductivity as measurement index, under identical reaction conditions, test respectively, result is as shown in table 1.Experiment condition: heating power 70W, cold junction temperature 20 DEG C, environment temperature 30 DEG C.
Table 1 experimental result
| Sample number into spectrum | Coefficient of heat conductivity (W/mK) | Sample number into spectrum | Coefficient of heat conductivity (W/mK) |
| O1 | 1.598 | 09 | 1.595 |
| 02 | 1.537 | 10 | 1.638 |
| 03 | 1.495 | 11 | 1.695 |
| 04 | 1.612 | 12 | 1.538 |
| 05 | 1.545 | 13 | 1.462 |
| 06 | 1.482 | 14 | 1.486 |
| 07 | 1.563 | 15 | 1.612 |
| 08 | 1.489 | 16 | 1.583 |
Experimental precision is calculated as follows:
Measure frequency n=16 as shown in Table 1, and coefficient of heat conductivity theoretical value λ=1.5 of TP215 heat conductive silica gel pad, can obtain thus:
Square error
Square error coefficient
From calculating above, the precision that the coefficient of heat conductivity of this instrument surveys most result is higher.
Only carried out brief description for Fig. 1-Fig. 4 in the present invention, but the invention is not restricted to these embodiments, without departing from the scope of the subject in the invention, can carry out various distortion, this it will be apparent to those skilled in the art that.