CN103278528A - Device and method for measuring thermal conductivity of powder - Google Patents

Abstract

The invention relates to a device and a method for measuring the thermal conductivity of powder with different bulk densities. The method comprises the steps of: measurement of electric current of an electric heating wire and voltage at two ends of the electric heating wire; measurement of the temperature of the electric heating wire; determination of the temperature of a powder material; determination of the pressure of the powder; calculation of the bulk density of the powder; calculation of the heating power per unit length of the electric heating wire; and calculation of a heat transfer coefficient. The device for measuring the thermal conductivity of the powder with the different bulk densities comprises a workbench, a bottom plate, side plates, a material chamber, a cover plate, two pushing plates, a hydraulic propulsion device, the electric heating wire, a thermocouple wire, a voltage stabilizing direct-current power supply, a pressure sensor, and a heating plate, wherein the hydraulic propulsion device synchronously and symmetrically propels the pushing plates at the same speed to compact a powder material and change the bulk densities. By measuring the displacement of the two pushing plates, the corresponding bulk density of the powder can be calculated. The electric heating wire is installed at the central points of the two side plates to form a closed loop with the voltage stabilizing direct-current power supply. The device and the method can be used for calculating the thermal conductivity according to a time-temperature logarithmic curve, and accurately measuring the thermal conductivity of the powder material with the different bulk densities.

Description

A kind of device and method of measuring the powder coefficient of heat conductivity

Technical field

The present invention relates to the apparatus and method of thermal conductivity measurement under the different bulk densitys of powder body material, particularly the equipment design field relevant with elastic body powder coefficient of heat conductivity.

Background technology

Powder body material has bigger compressibility, corresponding different bulk density (porosity) under the different pressures.Because the coefficient of heat conductivity of the thermal conductivity ratio solid of still air is little, along with the rising (reduction of porosity) of bulk density, it is big that its coefficient of heat conductivity can become.So the change meeting of bulk density (porosity) produces tremendous influence to the coefficient of heat conductivity of powder body material.The size of coefficient of heat conductivity is directly connected to the quality of material heat transfer property, affects design or the selection of firing equipment.In the design of the extrusion equipment of processing powder body material, mixing plant, play crucial effects.

Heat-pole method is a kind of material coefficient of heat conductivity unstable state method of testing, it have easy, quick, easy operating, accurately, advantage such as experimental facilities is simple, thereby in engineering and scientific research, obtained using widely.Be applicable to that by national standard (GB/T10297-1998) heat-pole method coefficient of heat conductivity is less than the thermal Conductivity Determination of the isotropy homogeneous solid material of 2W/ (mK).

In actual production, for example, twin-screw is extruded in the process of rubber powder, and along with the variation of pitch, rubber powder bulk density (porosity) can change.Rubber powder in the different screwing elements has different coefficient of heat conductivity.Accurately measuring rubber powder coefficient of heat conductivity-bulk density relation curve can extend efficient help to the composite design of operating procedure, parameter setting and screw rod.But the device that does not have powder coefficient of heat conductivity under the different bulk densitys of special test at present.This paper is on the basis of heat-pole method proving installation, and invention has designed a kind of device that changes the powder bulk density, measures the coefficient of heat conductivity of powder sample under the different bulk densitys with this.The present invention will provide basic data to design, the production of powder industry.

Summary of the invention

The objective of the invention is to: by a kind of device of measuring the powder coefficient of heat conductivity is provided, being implemented in different bulk densitys, under the temperature and pressure to the powder body material thermal Conductivity Determination.

A kind of device of measuring the powder coefficient of heat conductivity is characterized in that: use and carry out the measurement of powder coefficient of heat conductivity under the different bulk densitys as lower device, the formation of its device as depicted in figs. 1 and 2.

A kind of powder body material heat conductivity measuring device is characterized in that:

Pushing plate on two hydraulic pushers, two side plates, cover plate and base plates constitute airtight material chambers; Setting pressure sensor on the cover plate; The heating wire two ends are fixed on the central spot of two side plates of material chamber, draw by lead, connect constant voltage dc source; The central spot of heating wire connects thermocouple wire, measures the heating wire temperature value in real time; Two heating plates are separately fixed at the outside of two side plates, to expecting indoor material heating temperature control to be measured, temperature stabilization are controlled at temperature spot to be measured; Whole device is fixed on the worktable.

Further, the length-diameter ratio of heating wire is 100～120.

Further, the ratio of thermocouple wire thermometric end diameter and heating wire diameter is 0.6～1.

Further, the heating wire diameter is 0.4～0.5mm, and effective length is 50～60mm, and thermocouple wire thermometric end diameter is 0.3～0.4mm.

Heating wire length-diameter ratio 100～120 is in order to satisfy the hypothesis requirement of endless thermal source; Heating wire thermometric end diameter and heating wire diameter ratio are 0.6～1, are the temperature that can measure heating wire for heating wire thermometric end effectively accurately.

Material to be measured is filled the material chamber, and hydraulic pusher promotes pushing plate and goes up the mobile in opposite directions a certain distance of synchronous same-speed along its length, pushes material to be measured, changes the bulk density of powder; Constant voltage dc source heating heating wire, record current value and heating wire both end voltage value calculate hot line unit length heating power q;

Thermocouple wire is measured the temperature variation of heating wire, obtains temperature-time logarithmic relationship curve; Two end points of straight-line segment from this curve are chosen time corresponding and temperature, i.e. (τ _Min, θ _Min) and (τ _Max, θ _Max) the substitution formula

$\mathrm{\&lambda;}=\frac{\mathrm{<figure-callout\; id="4"\; label="q"\; filenames="HDA00003218597400022.png"\; state="\{\{state\}\}">q</figure-callout>}}{4\mathrm{\&pi;}}\frac{\ln {\mathrm{\&tau;}}_{\max }-\ln {\mathrm{\&tau;}}_{\min }}{{\mathrm{\&theta;}}_{\max }-{\mathrm{\&theta;}}_{\min }}$

Calculate coefficient of heat conductivity; Move different distances according to push pedal, obtain different bulk densitys, repeat the coefficient of heat conductivity that the said method measurement calculates powder under the different bulk densitys.

The present invention can be used for various powders or fine particle, thermal conductivity measurement under different bulk densitys, different temperatures, different moisture percentage.

Description of drawings

The synoptic diagram of Fig. 1 powder body material heat conductivity measuring device.

1 worktable, 2 base plates, 3 side plates, material chambers 4,5 cover plates, 6 push pedals, 7 hydraulic pushers, 8 thermocouple groove, 9 heating wire fairleads, 10 pressure transducers.

Fig. 2 material chamber enlarged diagram.

11 heating wire, 12 thermocouple wires, 13 heating plates, 14 materials to be measured, 15 constant voltage dc sources

Fig. 3 temperature rise-time logarithmic curve (θ-temperature rise, ° C of unit, τ-time, unit, s)

Heating wire temperature-time logarithmic curve during Fig. 4 L1=130mm

The relation curve of rubber powder bulk density and coefficient of heat conductivity under Fig. 5 normal temperature

Embodiment

Pushing plate 6 on two hydraulic pushers 7, two side plates 3, cover plate 5 and base plates 2 constitute airtight material chambers 4.Setting pressure sensor 10 on the cover plate 5.Heating wire 11 two ends are fixed on the central spot of two side plates 3 of material chamber, draw by lead, and the heating wire diameter is that 0.4～0.5mm, effective length are 50～60mm, connect constant voltage dc source 15.The central spot of heating wire 11 connects thermocouple wire 12, and thermocouple wire thermometric end diameter is 0.3～0.4mm, measures heating wire 11 temperature values in real time.Heating plate 13 to the material heating temperature control to be measured in the material chamber 4, is controlled temperature stabilization at temperature spot to be measured.Whole device is fixed on the worktable 1.

Use described device and measure the method for powder coefficient of heat conductivity, it is characterized in that:

Material 14 to be measured is filled pushing plate 6 on material chamber 4, two hydraulic pushers 7 go up synchronous same-speed along its length and advance in opposite directions, with material 14 extruding to be measured, the bulk density of change powder.By constant voltage dc source 15 heating heating wire 11, record corresponding current value I and heating wire both end voltage value U, and calculate hot line unit length heating power q by formula (1).

$q=\frac{\mathrm{UI}}{l}---\left(1\right)$

In the formula, l is the heating wire effective length, and the m of unit, q are the heating power of hot line unit length, the W/m of unit.

Temperature variation by thermocouple wire 12 measurement heating wire 11 obtains temperature-time logarithmic relationship curve, as Fig. 3.Two end points of straight-line segment from this curve are chosen time corresponding and temperature, i.e. (τ _Min, θ _Min) and (τ _Max, θ _Max) substitution formula (2) calculates coefficient of heat conductivity.Move different distances according to push pedal, obtain different bulk densitys, repeat the coefficient of heat conductivity that the said method measurement calculates powder under the different bulk densitys.

$\mathrm{\&lambda;}=\frac{\mathrm{<figure-callout\; id="4"\; label="q"\; filenames="HDA00003218597400022.png"\; state="\{\{state\}\}">q</figure-callout>}}{4\mathrm{\&pi;}}\frac{\ln {\mathrm{\&tau;}}_{\max }-\ln {\mathrm{\&tau;}}_{\min }}{{\mathrm{\&theta;}}_{\max }-{\mathrm{\&theta;}}_{\min }}---\left(2\right)$

Material the wide of chamber is W, and height is H, and initial length is L ₀, the quality of expecting indoor material is m.The length that hydraulic pusher promotes push pedal change material chamber is respectively L ₁, L ₂L _i, the density of the correspondence of powder material is ρ ₀, ρ ₁, ρ ₂ρ _i, available formula (4) and (5) calculate, and measure ρ respectively _iThe relation curve of the temperature and time of the heating wire under corresponding calculates coefficient of heat conductivity λ according to formula (1), (2) _i

Material chamber initial volume:

V ₀=WHL ₀ (3)

ρ ₀=m/V ₀ （4）

ρ _i=ρ ₀(L ₀/L _i) （5）

Embodiment 1: under normal temperature, the rubber powder to be measured of quality m=288.12g is filled the material chamber, covers cover plate.The initial size in material chamber: wide W=70mm, high H=70mm, long L ₀=150mm.The effective length l=60mm of heating wire.Push pedal on two hydraulic pushers is gone up synchronous same-speed along its length and is advanced in opposite directions, and mobile different distance with rubber powder extruding to be measured, calculates corresponding rubber powder bulk density respectively by formula (3) and (4) respectively.When push pedal moves to L ₁After the distance of=130mm, obtain rubber powder bulk density ρ according to formula (3) and (4) ₁=0.452g/cm ³Begin to heat heating wire by constant voltage dc source, and read current value I ₁=0.110A and magnitude of voltage U ₁=24.01V is according to the heating power q on formula (1) the unit of account length ₁=2.634W/m.Thermocouple wire is measured the temperature variation of heating wire, obtains the temperature-time logarithmic relationship curve of heating wire, as shown in Figure 4.Two end points of straight-line segment from this curve are chosen time corresponding and temperature is respectively (21.8,5.3) and (21.8,5.7) substitution formula (2) and calculates coefficient of heat conductivity λ ₁=0.0327W/ (mK).Repeat the coefficient of heat conductivity that the said method measurement calculates powder under the different bulk densitys.Concrete measurement is calculated and be the results are shown in Table 1.

The measurement result of calculation of rubber powder bulk density and coefficient of heat conductivity under table 1 normal temperature

Measure temperature: 20 ° of C

According to data and the result calculated of experiment measuring, draw out the relation curve of rubber powder bulk density and coefficient of heat conductivity under the normal temperature, as shown in Figure 5.

Above embodiment is described, only in order to an example of the present invention to be described, and and unrestricted technical scheme described in the invention; Therefore, although with reference to the above embodiments the present invention is had been described in detail,, those of ordinary skill in the art should be appreciated that still and can make amendment or be equal to replacement the present invention; And all do not break away from technical scheme and the improvement thereof of the protection domain of the present invention's proposition, and it all should be encompassed in the middle of the claim scope of the present invention.

Claims (5)

1. powder body material heat conductivity measuring device is characterized in that:

Pushing plate on two hydraulic pushers, two side plates, cover plate and base plates constitute airtight material chambers; Setting pressure sensor on the cover plate; The heating wire two ends are fixed on the central spot of two side plates of material chamber, draw by lead, connect constant voltage dc source; The central spot of heating wire connects thermocouple wire, measures the heating wire temperature value in real time; Two heating plates are separately fixed at the outside of two side plates, to expecting indoor material heating temperature control to be measured, temperature stabilization are controlled at temperature spot to be measured; Whole device is fixed on the worktable.

2. powder body material heat conductivity measuring device according to claim 1, it is characterized in that: the length-diameter ratio of heating wire is 100～120.

3. powder body material heat conductivity measuring device according to claim 1, it is characterized in that: the ratio of thermocouple wire thermometric end diameter and heating wire diameter is 0.6～1.

4. according to any described powder body material heat conductivity measuring device of claim 1-3, it is characterized in that: the heating wire diameter is 0.4～0.5mm, and effective length is 50～60mm, and thermocouple wire thermometric end diameter is 0.3～0.4mm.

5. use the measuring method that device according to claim 1 carries out the powder body material coefficient of heat conductivity, it is characterized in that: material to be measured is filled the material chamber, hydraulic pusher promotes pushing plate and goes up the mobile in opposite directions a certain distance of synchronous same-speed along its length, pushes material to be measured, changes the bulk density of powder; Constant voltage dc source heating heating wire, record current value and heating wire both end voltage value calculate hot line unit length heating power q;

Thermocouple wire is measured the temperature variation of heating wire, obtains temperature-time logarithmic relationship curve; Two end points of straight-line segment from this curve are chosen time corresponding and temperature, i.e. (τ _Min, θ _Min) and (τ _Max, θ _Max) the substitution formula

$\mathrm{\&lambda;}=\frac{q}{4\mathrm{\&pi;}}\frac{\ln {\mathrm{\&tau;}}_{\max }-\ln {\mathrm{\&tau;}}_{\min }}{{\mathrm{\&theta;}}_{\max }-{\mathrm{\&theta;}}_{\min }}$

Calculate coefficient of heat conductivity; Move different distances according to push pedal, obtain different bulk densitys, repeat the coefficient of heat conductivity that the said method measurement calculates powder under the different bulk densitys.

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