CN102183544B - Thermal-property transient measurement method and device - Google Patents

Abstract

The invention discloses a thermal-property transient measurement method and device, which are used for automatically measuring thermal conductivity, thermal diffusion coefficient, specific heat at constant pressure and density of a material and are also used for analysing the regular pattern of the thermal property of the material near the room temperature along the change of the temperature. The method comprises the following steps of: placing a cylindrical hot needle in a uniform and infinite medium; and continuously heating the medium by a constant thermal flow through the hot needle to form a one-dimensional cylindrical heat-transferring model in the radical direction. The measurement device comprises a direct-current stable-current power supply, the hot needle, a temperature signal collecting module, a signal processor, a memory and a display. A column body of the hot needle is made of carbon fibre and is composed of a core column and a sleeve pipe; the electric heating element is wounded on the core column through a double-head manganin lacquered wire and the double-head manganin lacquered wire is formed by doubling and winding one manganin lacquered wire along the central point; and an thermoelectric couple is formed by welding one copper wire and one konstantan wire in the thermoelectric couple grade.

Description

Hot property transient measurement method and device

Technical field

The invention belongs to field of measuring technique, be specifically related to a kind of hot property transient measurement method and device, for automatically measuring thermal conductivity, thermal diffusion coefficient, specific heat at constant pressure and the density of material; Analyze the temperature variant rule of the hot physical property of near room temperature material.

Background technology

The hot physical property of material, refers to thermal conductivity, thermal diffusion coefficient, specific heat at constant pressure and the density of material.So-called transient state is measured automatically, is in the process of heat temperature raising, completes fast the work such as automatic measurement, record, deal with data.

The 1970s and 1980s in last century, about the research of hot physical property instantaneous measurement technology, once once there is a climax at home, outward.The numerous well-known scholars in home and abroad have made extensive work, have obtained very great achievement.At that time, the measuring methods such as impulse method, constant flow method, heat-pole method had been studied.Wherein, these two kinds of transient measurement methods of impulse method and constant flow method, owing to being subject to placing restrictions on of technical merit at that time, and the impact of many conditions, home and abroad scholar fails to achieve one's goal and makes actual adaptable surveying instrument.Thereby the corresponding ministerial standard of once promulgating, also throws aside at present.In long period, in fact this problem is not resolved.Until the beginning of this century, the instantaneous measurement instrument of the impulse method based on the large heat transfer model of Semi-infinite One-dimensional, constant flow method just succeeds, and is named as the hot physical property transient state of SHT-20 automatic measuring instrument.By contrast, though heat-pole method has national standard and instrument supply market.But heat-pole method still fails to break through the category of steady state measurement, it is not also transient measurement method truly, need to be improved and enhanced.

Summary of the invention

Object of the present invention, is to provide a kind of brand-new hot physical property transient state method for automatic measurement and device (the hot property transient measurement method of pin type and device), the thermal conductivity of Quick Measurement material, thermal diffusion coefficient, specific heat at constant pressure and density; Analyze the temperature variant rule of the hot physical property of near room temperature material.

Technical scheme of the present invention is:

A property transient measurement method, based in even, Infinite medium, places a cylindric hot pin, by constant heat flux by hot pin to medium continuous heating, form one dimension face of cylinder heat transfer model radially, this heat transfer model is characterized by following formula:

(1)

In formula:

represent in detected materials, the distance of distance hot pin axis is r place, τ=t-t ₀temperature variation in time;

T ₀(s) for adding the initial time of thermal measurement.

T (r, t) (℃) for distance hot pin axis in medium is r distant place, t temperature constantly;

T (r, t ₀) (℃) for being r distant place apart from hot pin axis in medium, add the temperature of thermal measurement initial time;

thermal diffusion coefficient for detected materials;

density for detected materials;

M (kg) represents the quality of certain detected materials;

V(m ³) represent the volume of this certain detected materials;

C _pj/ (kgk) represents the specific heat at constant pressure of detected materials;

λ W/ (mk) represents the thermal conductivity of detected materials;

represent the thermal power that hot pin unit length is sent, or claim calorific intensity;

L (m) represents effective heated length of hot pin;

W=I ²r (W) represents the heating power of hot pin;

I (A) is by the strength of current of the heating current of hot pin;

The resistance of the hot pin heater of R (Ω);

The above-mentioned pulse cracking of surely separating problem is

When using constant heat flux continuous heating, i.e. in the time from τ=0 to τ, r place in test specimen, the temperature rise of τ in the time, an integration of available above-mentioned pulse cracking obtains.This integration, can be expressed as a straight-line equation approx

In formula: slope

Intercept

Here, C ^*=1.78115, be integration constant.

The thermal conductivity of Calculating material and thermal diffusion coefficient:

With measuring in the heat time, obtain temperature-time logarithm ordered series of numbers T (r ₀, t)～lnt, makes linear fit by young waiter in a wineshop or an inn's rule, calculates the k of the 1st sample, and D, has

Thermal conductivity

Thermal diffusion coefficient

With corresponding medial temperature

From i=1, choose j sample in succession.Repeat above-mentioned calculating, build database [λ _j, a _j, T _j].Then, by young waiter in a wineshop or an inn's rule, do conic fitting, draw the experimental formula of calculating thermal conductivity and thermal diffusion coefficient

λ(T)＝η ₀+η ₁T+η ₂T ² [T ₁，T ₂] (8)

a(T)＝ζ ₀+ζ ₁T+ζ ₂T ² [T ₁，T ₂] (9)

The thermal conductivity that digital simulation intermediate value temperature is corresponding and thermal diffusion coefficient λ, a;

Bulk density and specific heat at constant pressure

Density

Specific heat at constant pressure

Device based on above-mentioned hot property transient measurement method, comprise DC current stabilized power supply, hot pin, temperature signal collection module, signal processor, storer, display, described hot pin is cylindric, with insulating material, makes, and post contains thermocouple and electrical heating elements; Described storer prestores the computation model of thermal physical property parameter, and described DC current stabilized power supply is powered to temperature collect module.Thermocouple output temperature signal, temperature collect module converts this temperature signal to digital signal, sends into signal processor, and signal processor is processed according to the computation model of thermal physical property parameter, and result is shown by display.

The cylinder of described hot pin is made with carbon fiber, stem stem and sleeve combination, consists of, and described electrical heating elements is with double end copper-manganese enameled wire on stem stem, and this double end copper-manganese enameled wire is to form along mid point doubling coiling with a copper-manganese enameled wire.Described thermocouple is welded with copper cash and each, the constantan line of thermocouple level.

The efficient heat generation length of described hot pin is more than or equal to 40 times of hot pin overall diameters, i.e. l >=40d.

Described DC current stabilized power supply output DC current is accurate adjustable between 0.01-1.0004; Within the time of thermal measurement, the fluctuating range of heating current: Δ I≤± 0.001A.

The temperature resolution of described temperature collect module: Δ T≤0.1k; Sample frequency: adjustable continuously between 0.5-1Hz.

Technique effect of the present invention:

The one dimension face of cylinder heat transfer model that the present invention sets up, truly, accurately describes out the heat conducting objective law of medium, realized by steady state measurement to instantaneous measurement transition, and be the instantaneous measurement of real meaning; Measurement mechanism instantaneous measurement takes extremely short, less than 200 seconds, and little interference by environment, the factor that impact is measured is easily revised, and measurement accuracy is high, and relative error is in 1% left and right.And can measure thermal diffusion coefficient, thermal conductivity, specific heat at constant pressure, density.

Accompanying drawing explanation

Fig. 1 is the structured flowchart of this measurement mechanism;

Fig. 2 is the hot pin outer tube structure schematic diagram of this measurement mechanism;

Fig. 3 is the hot pin inner tube structure schematic diagram of this measurement mechanism.

Embodiment

Ultimate principle of the present invention, is based on evenly, in Infinite medium, places a hot pin, by constant heat flux by hot pin to medium continuous heating, form one dimension garden cylinder heat transfer model radially, this heat transfer model is characterized by following formula:

(1)

In formula:

represent in detected materials, the distance of distance hot pin axis is r place, τ=t-t ₀temperature variation in time;

T ₀(s) for adding the initial time of thermal measurement.

T (r, t) (℃) for distance hot pin axis in medium is r distant place, t temperature constantly;

T (r, t ₀) (℃) for being r distant place apart from hot pin axis in medium, add the temperature of thermal measurement initial time;

thermal diffusion coefficient for detected materials;

density for detected materials;

M (kg) represents the quality of certain detected materials;

V(m ³) represent the volume of this certain detected materials;

C _pj/ (kgk) represents the specific heat at constant pressure of detected materials;

λ W/ (mk) represents the thermal conductivity of detected materials;

represent the thermal power that hot pin unit length is sent, or claim calorific intensity;

L (m) represents effective heated length of hot pin;

W=I ²r (W) represents the heating power of hot pin;

I (A) is by the strength of current of the heating current of hot pin;

The resistance of the hot pin heater of R (Ω);

The above-mentioned pulse cracking of surely separating problem is

When using constant heat flux continuous heating, i.e. in the time from τ=0 to τ, r place in test specimen, the temperature rise of τ in the time, an integration of available above-mentioned pulse cracking obtains.This integration, can be expressed as a straight-line equation approx

In formula: slope

Intercept

Here, C ^*=1.78115, be integration constant.

The thermal conductivity of Calculating material and thermal diffusion coefficient:

With measuring in the heat time, obtain temperature-time logarithm ordered series of numbers T (r ₀, t)～lnt, makes linear fit by young waiter in a wineshop or an inn's rule, calculates the k of i sample, and D, has

Thermal conductivity

Thermal diffusion coefficient

With corresponding medial temperature

From i=1, choose j sample in succession.Repeat above-mentioned calculating, build database [λ _j, a _j, T _j].Then, by young waiter in a wineshop or an inn's rule, do conic fitting, draw the experimental formula of calculating thermal conductivity and thermal diffusion coefficient

λ(T)＝η ₀+η ₁T+η ₂T ² [T ₁，T ₂] (8)

a(T)＝ζ ₀+ζ ₁T+ζ ₂T ² [T ₁，T ₂] (9)

The thermal conductivity that digital simulation intermediate value temperature is corresponding and thermal diffusion coefficient λ, a;

Bulk density and specific heat at constant pressure

Density

Specific heat at constant pressure

Referring to Fig. 1: this device is comprised of DC current stabilized power supply A, hot pin B, temperature signal collection module C, signal processor D, storer F, display E.Wherein:

DC current stabilized power supply A: input: 220V, 50Hz civil power; Output: DC current, accurate adjustable between 0.01-1.000A; Within the time of thermal measurement, the fluctuating range of heating current: Δ I≤± 0.001A.

Temperature signal collection module C: temperature resolution: Δ T≤0.1k; Sample frequency: adjustable continuously between 0.5-1Hz.

Manufacture and design hot pin B, this hot pin B is heating element, is again temperature element.

Basic demand to hot pin B: firm; Wear-resisting wiping; Except termination, uniformity of temperature profile in the longitudinal direction; When temperature raises, the resistance variations of heater element is minimum; Material thermal conductivity is good etc.Structure can consider to use coaxial sleeve structure.In inner tube around sufficiently long heating wire, outer tube uniform temperature; Outer tube outer surface device temperature element, measures the temperature variation of hot pin and detected materials thermal interface.Control length-diameter ratio, allow the efficient heat generation length of hot pin be more than or equal to 40 times of hot pin overall diameters, l >=40d, generally can meet one dimension face of cylinder heat transfer model.If measure temperature with thermocouple, point for measuring temperature should be arranged on the mid point of hot pin efficient heat generation length; Make the tinsel that thermocouple is used, diameter is selected 0.05mm.

Through experimental study, this hot pin employing heat conduction carbon fiber pipe good, lightweight is made host material, and manganese-copper filament is made exothermic material, and special-purpose copper constantan thermocouple, for the hot pin of measuring distance axis r distant place t temperature variation constantly.And press structural formula

Inner tube: Φ 2.5 (1) * 211 (4+180+27)+Φ 0.12 * 930[884+2 * 23] mm; This inner tube is the carbon fiber rod of available φ 25mm also; Outer tube: [Φ 4 (0.5) * 186 (180+6)+Φ cu0.05 * 135+cusn0.05 * 135] compound composition of mm.

The hot pin of making like this, absorbs heat the measuring error causing except self that can revise, and the measuring error that all the other factors cause is less than 0.2%.

The meaning of outer tube structure formula: with 4 millimeters of external diameters, wall thickness 0.5 milli, the carbon fiber pipe of long 186 millimeters is made outer tube.In the longitudinal direction, 180 length are used for covering manganese-copper filament winding, and 6 millimeters for stationary heat pin; Aft section represents 0.05 millimeter of diameter for temperature element, the thermocouple that the copper cash of long 135 millimeters and constantan line form, and mean that point for measuring temperature is positioned at the midpoint of outer tube outer surface.

The meaning of inner tube structure formula: with 2.5 millimeters of external diameters, 1 millimeter of wall thickness, the carbon fiber pipe of long 211 millimeters is made inner tube.In the longitudinal direction, 4 millimeters of front ends, for opening locating groove; Middle 180 millimeters for around manganese-copper filament; 27 millimeters of the other ends, are fixedly connected with.Aft section represents, with 0.12 millimeter of diameter, the manganese-copper filament of long 930 millimeters, wherein, 884 millimeters around the region of 180 millimeters long, and as heater element, all the other 46 millimeters of conducts pick out lead-in wire.

Specifically method for making as shown in Figure 2 and Figure 3: get 2.5 millimeters of external diameters, 1 millimeter of wall thickness, one of the carbon fiber pipe of long 211 millimeters.One end is opened wide 1 millimeter in diametric(al), the ditch of dark 4 millimeters, as the use around manganese-copper filament location.Then, 0.12 millimeter, cut-off footpath, one of the insulation enamel manganin of long 930 millimeters, doubling, puts into locating groove by mid point.By double helical form, the two-wire of 442 millimeters long is evenly curled up on the carbon pipe of 180 millimeters and fixed, make heating element B-1.Wiring is drawn in 23 millimeters of remaining conducts.Get 4 millimeters of external diameters, 0.5 millimeter of wall thickness, long 186 millimeters of carbon pipes, the inner tube that coiling is good screws in from locating groove end, until locating groove just all exposes.Now, coiling is just all covered.Then, stamen of getting aviation connector takes out, and manganese-copper filament extension line is connected on pin binding post.Learn from else's experience again and be demarcated as 0.05 millimeter of the diameter of thermocouple level; each, the copper cash of long 135 millimeters and constantan line, be longitudinally arranged in outer tube-surface, and external pipe connection is drawn on binding post in one end; other end alignment; move the mid point of outer tube heating part to, by unnecessary removing, weld; be bonded at outer tube outer surface; make thermocouple B-2, protective seam is coated on surface, dries.Like this, just, made a hot pin.

Measuring process is as follows:

According to above-mentioned heat transfer model, write data processing software.

Be equipped with transient state self-operated measuring unit, deposit data processing software in storer F; Hot pin B and temperature signal collection module C are connected.

Choose a certain amount of detected materials, measure its volume V, with physical balance, weigh quality m.If measuring object raft material, as long as insert hot pin B.If material is limited, need to prepare a bulk containers.The volume of container at least should be Φ 200 * 184mm.Container is filled, and hot pin B inserts bucket central authorities.If detected materials is massive material, on material, punch or fluting, in hot pin B patchhole or groove.The diameter of hole or groove and hot pin diameter adapt, and make hot wire surface can be attached to hole wall or cell wall.

Heating current is set for different detected materials, the varying in size of heating current.In general, density is little, and heating current should be smaller.For example, heat-insulation material, heating current can be chosen as between 0.1～0.3A; The detected materials that density is large, electric current should be large.

Add after thermal measurement current settings, connect heating current, measure.Temperature signal collection module C sends temperature signal into signal processor D, and signal processor D is according to the computation model treatment temperature signal that is pre-stored in the thermal physical property parameter in storer F, and result is shown by display E.

Observe the demonstration of temperature time curve, the numeration of measurement data list.After adding thermal measurement and starting, while having 70 groups of numerations at least, can stop measuring.

It is more than the method for measuring containing the hot physical property of wet stock.The variation of moisture percentage is larger on the impact of measuring.The same material of different moisture percentages, measured value does not at the same temperature have the property of comparison.The hot physical property of only having over dry material, the measured value under same temperature, is only consistent.

Measure the hot physical property of over dry material, before measuring, need to use electrically heated drying cabinet, detected materials is baked to constant weight repeatedly, be stored in exsiccator.Until cool but after, then measure.Only, under over dry condition, the hot physical property measuring, just has the property compared comparatively accurately.

In order to try to achieve the temperature variant rule of the hot physical property of material, can get j=1,2,3, Λ Λ N, calculates [λ (the T of N sample in succession _j), T _j] and [a (T _j), T _j].By young waiter in a wineshop or an inn's rule, make fitting of a polynomial, the experimental formula that can change with temperature in the hope of the hot physical property of material in temperature range in plan.

Like this, with this device, realize one-shot measurement, obtained a plurality of hot physics coefficient of material simultaneously; And can also study near room temperature the rule of material thermophysical property temperature variation.

The measuring error of this device:

The category-A uncertainty of measuring, by the uncertainty of theory of errors estimation end product.Under equal state, the reproduction error of duplicate measurements is better than 2.0%.

The category-B uncertainty of measuring, according to theoretical analysis: hot pin self heat absorption can not be omitted the impact of measuring, and should be revised.The impact of other factors, amounts to and is not more than 0.2%, can be not significant.

Claims (5)

1. a hot property transient measurement method, based in even, Infinite medium, places a cylindric hot pin, by constant heat flux by hot pin to medium continuous heating, form one dimension face of cylinder heat transfer model radially, this heat transfer model is characterized by following formula:

$\frac{\∂\mathrm{\θ}(r,\mathrm{\τ})}{\∂\mathrm{\τ}}=a[\frac{{\∂}^2\mathrm{\θ}(r,\mathrm{\τ})}{{\∂r}^2}+\frac{1}{r}\·\frac{\∂\mathrm{\θ}(r,\mathrm{\τ})}{\∂r}]$

1，τ=t ₀，θ(r，τ)=0 (1)

$2,\mathrm{\τ}>0,r=r_0,q=-\frac{\mathrm{\λ}}{2\mathrm{\π}}\·\frac{\∂\mathrm{\θ}(r,\mathrm{\τ})}{\∂r}$

3，τ>0，r→∞，θ(∞，τ)=0

In formula:

θ (r, τ)=T (r, t)-T (r, t ₀) (k), represent in detected materials, the distance of distance hot pin axis is r place,

τ=t-t ₀temperature variation in time;

T ₀(s) for adding the initial time of thermal measurement;

T (r, t) (℃) for distance hot pin axis in medium is r distant place, t temperature constantly;

T (r, t ₀) (℃) for being r distant place apart from hot pin axis in medium, add the temperature of thermal measurement initial time;

thermal diffusion coefficient for detected materials;

$\mathrm{\ρ}=\frac{m}{V}(\mathrm{kg}/m^3)$ Density for detected materials;

M (kg) represents the quality of certain detected materials;

V(m ³) represent the volume of this certain detected materials;

C _pj/ (kgk) represents the specific heat at constant pressure of detected materials;

λ W/ (mk) represents the thermal conductivity of detected materials;

represent the thermal power that hot pin unit length is sent, or claim calorific intensity;

L (m) represents effective heated length of hot pin;

W=I ²r (W) represents the heating power of hot pin;

I (A) is by the strength of current of the heating current of hot pin;

The resistance of the hot pin heater of R (Ω);

The above-mentioned pulse cracking of surely separating problem is

$\frac{\mathrm{d\θ}(r,\mathrm{\τ})}{\mathrm{d\τ}}=\frac{q}{4\mathrm{\π\λ\τ}}{e}^{-\frac{r^2}{4\mathrm{a\τ}}}---\left(2\right)$

When using constant heat flux continuous heating, i.e. in the time from τ=0 to τ, r place in test specimen, the temperature rise of τ in the time, an integration of available above-mentioned pulse cracking obtains; This integration, can be expressed as a straight-line equation approx

θ(r，τ)=klnτ+D

In formula: slope $k=\frac{q}{4\mathrm{\π\λ}}---\left(3\right)$

Intercept $D=k\ln \frac{4a}{C^{*}{r}^2}---\left(4\right)$

Here, C ^*=1.78115, be integration constant;

The thermal conductivity of Calculating material and thermal diffusion coefficient:

With measuring in the heat time, temperature-time logarithm ordered series of numbers T (r of acquisition ₀, t)～lnt, makes linear fit by young waiter in a wineshop or an inn's rule, calculates the k of the 1st sample, and D, has

Thermal conductivity ${\mathrm{\λ}}_1=\frac{I^{2}R}{4\mathrm{\πkl}}---\left(5\right)$

Thermal diffusion coefficient $a_1=\frac{C^{*}{r_0}^2}{4}{e}^{\frac{D}{k}}---\left(6\right)$

With corresponding medial temperature $T_1=\frac{T_{i=1}+T_{i=n}}{2}---\left(7\right)$

From i=1, choose j sample in succession; Repeat above-mentioned calculating, build database [λ _j, a _j, T _j]; Then, by young waiter in a wineshop or an inn's rule, do conic fitting, draw the experimental formula of calculating thermal conductivity and thermal diffusion coefficient

λ(T)=η ₀+η ₁T+η ₂T ² [T ₁，T ₂] (8)

a(T)=ζ ₀+ζ ₁T+ζ ₂T ² [T ₁，T ₂] (9)

The thermal conductivity that digital simulation intermediate value temperature is corresponding and thermal diffusion coefficient λ, a;

Bulk density and specific heat at constant pressure

Density $\mathrm{\ρ}=\frac{m}{V}---\left(10\right)$

Specific heat at constant pressure $c_p=\frac{\mathrm{\λ}}{\mathrm{a\ρ}}---\left(11\right).$

2. the device based on method described in claim 1, comprise DC current stabilized power supply, hot pin, temperature signal collection module, signal processor, storer, display, described hot pin is cylindric, with insulating material, makes, and post contains thermocouple and electrical heating elements; Described storer prestores the computation model of thermal physical property parameter, and described DC current stabilized power supply is powered to heating element; Thermocouple output temperature signal, temperature signal collection module converts this temperature signal to digital signal, send into signal processor, signal processor is processed according to the computation model of thermal physical property parameter, result is shown by display, it is characterized in that: the computation model of described thermal physical property parameter is

$\frac{\∂\mathrm{\θ}(r,\mathrm{\τ})}{\∂\mathrm{\τ}}=a[\frac{{\∂}^2\mathrm{\θ}(r,\mathrm{\τ})}{{\∂r}^2}+\frac{1}{r}\·\frac{\∂\mathrm{\θ}(r,\mathrm{\τ})}{\∂r}]$

1，τ=t ₀,θ(r，τ)=0 (1)

$2,\mathrm{\τ}>0,r=r_0,q=-\frac{\mathrm{\λ}}{2\mathrm{\π}}\·\frac{\∂\mathrm{\θ}(r,\mathrm{\τ})}{\∂r}$

3，τ>0，r→∞，θ(∞，τ)=0

In formula:

θ (r, τ)=T (r, t)-T (r, t ₀) (k), represent in detected materials, the distance of distance hot pin axis is r place, τ=t-t ₀temperature variation in time;

T ₀(s) for adding the initial time of thermal measurement;

T (r, t) (℃) for distance hot pin axis in medium is r distant place, t temperature constantly;

T (r, t ₀) (℃) for being r distant place apart from hot pin axis in medium, add the temperature of thermal measurement initial time;

thermal diffusion coefficient for detected materials;

$\mathrm{\ρ}=\frac{m}{V}(\mathrm{kg}/m^3)$ Density for detected materials;

M (kg) represents the quality of certain detected materials;

V(m ³) represent the volume of this certain detected materials;

C _pj/ (kgk) represents the specific heat at constant pressure of detected materials;

λ W/ (mk) represents the thermal conductivity of detected materials;

represent the thermal power that hot pin unit length is sent, or claim calorific intensity;

L (m) represents effective heated length of hot pin;

W=I ²r (W) represents the heating power of hot pin;

I (A) is by the strength of current of the heating current of hot pin;

The resistance of the hot pin heater of R (Ω);

The above-mentioned pulse cracking of surely separating problem is

$\frac{\mathrm{d\θ}(r,\mathrm{\τ})}{\mathrm{d\τ}}=\frac{q}{4\mathrm{\π\λ\τ}}{e}^{-\frac{r^2}{4\mathrm{a\τ}}}---\left(2\right)$

When using constant heat flux continuous heating, i.e. in the time from τ=0 to τ, r place in test specimen, the temperature rise of τ in the time, an integration of available above-mentioned pulse cracking obtains; This integration, can be expressed as a straight-line equation approx

θ(r，τ)=klnτ+D

In formula: slope $k=\frac{q}{4\mathrm{\π\λ}}---\left(3\right)$

Intercept $D=k\ln \frac{4a}{C^{*}{r}^2}---\left(4\right)$

Here, C ^*=1.78115, be integration constant;

The thermal conductivity of Calculating material and thermal diffusion coefficient:

With measuring in the heat time, temperature-time logarithm ordered series of numbers T (r of acquisition ₀, t)～lnt, makes linear fit by young waiter in a wineshop or an inn's rule, calculates the k of the 1st sample, and D, has

Thermal conductivity ${\mathrm{\λ}}_1=\frac{I^{2}R}{4\mathrm{\πkl}}---\left(5\right)$

Thermal diffusion coefficient $a_1=\frac{C^{*}{r_0}^2}{4}{e}^{\frac{D}{k}}---\left(6\right)$

With corresponding medial temperature $T_1=\frac{T_{i=1}+T_{i=n}}{2}---\left(7\right)$

From i=1, choose j sample in succession; Repeat above-mentioned calculating, build database [λ _j, a _j, T _j]; Then, by young waiter in a wineshop or an inn's rule, do conic fitting, draw the experimental formula of calculating thermal conductivity and thermal diffusion coefficient

λ(T)=η ₀+η ₁T+η ₂T ² [T ₁，T ₂] (8)

a(T)=ζ ₀+ζ ₁T+ζ ₂T ² [T ₁，T ₂] (9)

The thermal conductivity that digital simulation intermediate value temperature is corresponding and thermal diffusion coefficient λ, a;

Bulk density and specific heat at constant pressure

Density $\mathrm{\ρ}=\frac{m}{V}---\left(10\right)$

Specific heat at constant pressure $c_p=\frac{\mathrm{\λ}}{\mathrm{a\ρ}}---\left(11\right).$

3. device according to claim 2, it is characterized in that: the cylinder of described hot pin is made with carbon fiber, by stem stem and sleeve combination, formed, described electrical heating elements is with double end copper-manganese enameled wire on stem stem, and this double end copper-manganese enameled wire is to form along mid point doubling coiling with a copper-manganese enameled wire; Described thermocouple is welded with copper cash and each, the constantan line of thermocouple level.

4. device according to claim 2, is characterized in that: described DC current stabilized power supply output DC current is accurate adjustable between 0.01-1.000A; Within the time of thermal measurement, the fluctuating range of heating current: Δ I≤± 0.001A.

5. device according to claim 2, is characterized in that: the temperature resolution of described temperature collect module: Δ T≤0.1k; Sample frequency: adjustable continuously between 0.5-1Hz.

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