CN103499604A - Device and method for testing heat conductivity coefficient of composite honeycomb plate - Google Patents

Abstract

The invention provides a device for testing the heat conductivity coefficient of a composite honeycomb plate. A box body is made by adopting wood plates; the upper end of the box body is open, and the lower end of the box body is isolated from the ground through sole timber; thermal insulation materials are covered on inner walls of the box body to serve as liners; sealants are filled between the liners; an electric heater is arranged in the middle of the bottom in the box; temperature sensors are respectively arranged at four corners of the box body; an average measurement value of the four temperature sensors serves as a temperature Ti in the box; a thermometer is arranged outside the box body for testing an environmental temperature To; the four sensors and wires of the electric heater are guided out of the box through an adapter plate at the bottom of the box and are respectively connected with a temperature display instrument and a power supply outside the box; during test, a sample serves as a cover to close the opening of the box body, and the opening is sealed by an adhesive tape. According to the device, the heat conductivity coefficient of the composite honeycomb plate can be measured, and the error is less than 10 percent.

Description

Honeycomb composite plate test device of thermal conductivity coefficient and method

Technical field

The invention belongs to the heat transfer property technical field of measurement and test, relate to analysis of Heat Transfer and the application of honeycomb composite plate material.

Background technology

At present, because honeycomb composite plate has good heat-proof quality and mechanical stiffness concurrently, be widely used in the insulation occasion.Yet, because there is no the concrete coefficient of heat conductivity of honeycomb composite plate, often apply on engineering and estimated by designer's experience, the Data support that there is no science, seriously hindered the use field of honeycomb composite plate, and the slip-stick artist is safe in order to design, often caused a large amount of material resources wastes, data shows, the method of researching and solving of effort of many researchists, up to now, the method of some that propose (more than 200 ℃) test honeycomb composite plate coefficient of heat conductivity under the condition of high temperature, this is nonsensical for real engineering field, the result of measuring can only be for reference.

Existing material thermal conductivity test is divided into two large classes, i.e. unstable state method and steady state method by measuring method; The unstable state method is divided into again according to principle of work: heat-pole method, laser shine three kinds of method and plane heat source method, the advantage of these three kinds of method maximums is consuming time short, only just can obtain result several seconds, and sample size is not required, and therefore is applied widely.Due to the measuring process of unstable state method need be by material density or specific heat obtains or by calculating coefficient of heat conductivity.Therefore this method is only applicable to the material of even density, and this class material of honeycomb composite plate is to be combined by gas and solid, in solid, not only contain metal but also contain nonmetal, their density and specific heat difference are huge, and therefore all unstable state methods are not suitable for this class material of honeycomb composite plate.The method of testing of steady state method is mainly guarded-plate method, principle as shown in Figure 1: certain each 30cm of the common length and width of square sample 3(by thickness, thick 10cm) be inserted in heating plate 1 and cold drawing 5, certain thermograde is set.Use corrected heat flux sensor 2,4 to measure by the hot-fluid of sample, sensor 2,4 contacts with sample between flat board and sample.But measure just calculation of thermal conductivity of thickness of sample, thermograde and the hot-fluid that passes through sample.Design feature due to honeycomb core composite board, as shown in Figure 2: because interior exterior skin is mostly metal material 6, the good conductor of instant heating, heat conductivility is good, and sandwich layer generally is comprised of heat insulation material 7, both heat conductivilitys differ tens thousand of times, the heat that causes heating plate 1 to produce almost all dissipates along covering, there is no stable hot-fluid through sample, and the sensor 4 be positioned on cold drawing 5 does not detect hot-fluid certainly yet, therefore, flat band method does not measure the coefficient of heat conductivity of honeycomb core yet.

Summary of the invention

In order to overcome the deficiencies in the prior art, the invention provides the device of test honeycomb composite plate coefficient of heat conductivity under a kind of normal temperature, good with the goodness of fit of physical model, measurement data is accurate.

The technical solution adopted for the present invention to solve the technical problems is: a kind of honeycomb composite plate test device of thermal conductivity coefficient, comprise the casing that a plank is made, the casing upper end open, between lower end and ground, by chock, isolate, cabinet wall covers thermal insulation material as liner, and filling with sealant between liner is settled an electric heater in the middle of the case inner bottom part, four jiaos a temperature sensor is installed respectively in casing, is usingd the average measurement value of four temperature sensors as the temperature inside the box T _i, a thermometer test environment temperature T is set outside casing _o, the wire of four sensors and electric heater is derived outside case by the card extender at the bottom of case, respectively outer temperature display meter and the power supply of connecting box; During test, using sample as the closed with covers box opening, and use rubber belt sealing.

The thickness of described plank is 10～25 millimeters; Described liner thickness is greater than 200 millimeters; The inductive head of described temperature sensor is apart from 90～100 millimeters of cabinet walls; Described chock thickness is over 100 millimeters.

The present invention also provides a kind of honeycomb composite plate Determination of conductive coefficients method, comprises the following steps:

Switch on power, the temperature inside the box shown when temperature display meter continue 30 minutes constant, think inside and outside casing and reached balance, record now temperature; Calculate coefficient of heat conductivity

In formula: W is heater power, and l is sample thickness, and S is sample efficiently radiates heat face, S=a ², a is the effective length of side of sample.

The invention has the beneficial effects as follows: honeycomb composite plate test device of thermal conductivity coefficient and the method for utilizing the present invention to propose have solved the immesurable difficult problem of honeycomb core composite board coefficient of heat conductivity.

The accompanying drawing explanation

Fig. 1 is flat band method test philosophy figure;

Fig. 2 is the honeycomb core composite board structural drawing;

Fig. 3 is test fixture figure; Wherein, (a) being the test fixture cut-open view, is (b) the casing vertical view;

Fig. 4 is the test assay maps; Wherein, (a) being the honeycomb core side view, is (b) the covering vertical view;

Fig. 5 is the test process schematic diagram;

In figure, 1-heating plate, 2-sensor, the square sample of 3-, the 4-sensor, 5-cold drawing, 6-metal material, 7-heat insulation material, the 8-casing, 9-liner, 10-fluid sealant, 11-chock, the 12-temperature sensor, 13-electric heater, 14-card extender, 15-thermometer, the 16-power supply, 17-temperature display meter, 18-sample, 19-adhesive tape, the 20-honeycomb core, 21-exterior skin, 22-inside panel.

Embodiment

Below in conjunction with drawings and Examples, the present invention is further described, the present invention includes but be not limited only to following embodiment.

One, the theory of testing of coefficient of heat conductivity:

By Fourier's law, known, by the heat flow rate of a fixed point

be proportional to its section S, and in this some thermograde on vertical plane of getting

? $\frac{\mathrm{dQ}}{\mathrm{dt}}=\mathrm{\λS}\frac{\mathrm{dT}}{\mathrm{dl}}---\left(1\right)$

In formula: when Q is stable state, by the heat of the effective heat transfer area of sample, unit is J;

T is the Newtonian time, and unit is s;

λ is coefficient of heat conductivity, and unit is W/(mK);

S is area of section, and unit is m ²;

T is this some temperature on vertical plane of getting, and unit is ℃;

L is sample thickness, and unit is m;

Proportionality factors lambda is called again temperature conductivity, also claims coefficient of heat conductivity.

Plane table thermo makes to work under the condition of hot-fluid with the one way stable state transfer.Therefore, heat flow rate

be a constant, thermograde

for

now equation (1) can be expressed as

$\frac{\mathrm{dQ}}{\mathrm{dt}}=\mathrm{\λS}\frac{\mathrm{\ΔT}}{\mathrm{\Δl}}---\left(2\right)$

In formula: Δ T is this some temperature difference on vertical plane of getting, and Δ l is this some thickness difference on vertical plane of getting.

The sample that is l by known thickness is placed in test unit, makes between its hot side and huyashi-chuuka (cold chinese-style noodles) to keep a constant temperature difference, hot-fluid from hot side by sample stream to huyashi-chuuka (cold chinese-style noodles), by the chilled water in calorimeter, siphoned away.Can calculate according to temperature rise and the discharge of the water of the center calorimeter of flowing through the heat that chilled water absorbs within the unit interval.

By formula (2), can be obtained:

$\mathrm{\λ}=\frac{\mathrm{Ql}}{S(T_1-T_2)}---\left(3\right)$

In formula: T ₁for the temperature of sample hot side, T ₂temperature for the sample huyashi-chuuka (cold chinese-style noodles).

Two, content of the present invention is:

At first use 5 planks of 10～25 millimeters thick, make the casing 8 of a uncovered, as shown in Figure 3, the inwall liner 9 use thermal insulation materials of casing are made as the polyurethane foamed material that adds fire retardant, liner thickness is greater than 200 millimeters, fluid sealant 10 sealings for the gap formed between 5 liners, box house bulk is a * a * c millimeter, settle an electric heater 13 in the middle of the case inner bottom part, electric heater 13 power W fix, separately at each side plate center of box house, one temperature sensor 12 is set, inductive head, apart from 90～100 millimeters of sidewalls, is measured the temperature inside the box T _i, the temperature T in case _imean value by the measured value of four temperature sensors 12 replaces, and simultaneously, at test environment, one thermometer 15 test environment temperature T also is set _o, the wire of four sensors and electric heater is derived outside casees by the card extender 14 at the bottom of case, and the power supply 16 outer with case is connected with temperature display meter 17 respectively.

Sample requirement: Fig. 4 is the shape and size of test test sample 18, is about to need the sample of test coefficient of heat conductivity to press Fig. 3 making.During test, at first, with chock 11, the casing pad is overhead surpassed to 100 millimeters, using sample 18 as casing, 8 lid covers on casing 8, then with adhesive tape 19 sealings, as Fig. 5.

Test process: switch on power, after general half an hour, temperature will balance, and the condition of judgement balance is: the temperature shown when instrument 17, and after balance, while continuing still to remain unchanged in 30 minutes, just think inside and outside casing and reached balance, record now temperature.And calculate coefficient of heat conductivity λ by following formula (4).Formula (4) is the distortion of formula (3), and the power W with electric heater 13 in formula (4) replaces the Q in formula (3), the hygrometric formula T of sample hot side ₁use the temperature inside the box T _ireplace the temperature T of sample huyashi-chuuka (cold chinese-style noodles) ₂use the test environment temperature T _oreplace:

$\mathrm{\λ}=\frac{\mathrm{wl}}{S(T_i-T_o)}---\left(4\right)$

In formula: the W heater power is less than 500 watts.

L honeycomb core sample thickness, be less than 0.02 meter.

S honeycomb core sample efficiently radiates heat face, square metre.

S=a ²(5)

In formula: the effective length of side of a honeycomb core sample.

T _itest the temperature inside the box, degree.

T _i=（t ₁+t ₂+t ₃+t ₄）/4（6）

T in formula ₁, t ₂, t ₃, t ₄: be respectively four temperature that temperature sensor is measured in case, degree.T _othe test environment temperature, degree.

In the present invention, owing to using heater power W, replace the heat dissipation capacity Q of sample, ignored the heat radiation Q of frock _g, W=Q+Q in fact _g, below theoretical analysis once, neglect Q _g, on the impact of test result, in this case, the thickness l of frock _g=220, the thickness of exemplar only 20, the area of dissipation S of frock _g=2.2 square meters, exemplar is 1 square meter, chooses the coefficient of heat conductivity λ of frock material _gbe greater than 2 times of honeycomb composite plate material.From formula (2), know: heat dissipation capacity and thickness are inversely proportional to, and to area of dissipation and coefficient of heat conductivity, are directly proportional.Therefore, Qg:

the coefficient of heat conductivity that this invention is tested, error is less than 10%.

Three, embodiment:

The structure that Fig. 3 is test unit in embodiment and size, the structure that Fig. 4 is the honeycomb core sample and size, as we know from the figure: sample thickness l is 0.02 meter, section S is 1 square metre.Heater power W=100 watt in this case, by above data substitution (4) formula, obtain in present case, and the computing formula of coefficient of heat conductivity λ is:

$\mathrm{\λ}=\frac{2}{T_i-T_o}W/(m\·K)---\left(7\right)$

Embodiment 1: the thermal conductivity measurement of aluminium foil honeycomb core composite board

The material of honeycomb composite plate forms: the cellular board that sandwich layer is made by aluminium foil, two side skins are respectively rustproof aluminium sheet and reinforced plastic glass fibre plate.It is made to sample by Fig. 4 size, be arranged on the frock shown in Fig. 3, after switching on power 30 minutes, 4 temperature sensor senses temperature that are placed in fully sheathed case keep stable, respectively:

t ₁=34.876℃,t ₂=34.878℃,t ₃=34.877℃,t ₄=34.878℃。

Environment temperature now:

T _o=22℃

By formula (6), obtained:

T _i=（34.876+34.878+34.877+34.878）/4=34.877℃

By formula (7), calculate to such an extent that coefficient of heat conductivity is:

Conclusion: the coefficient of heat conductivity of aluminium foil honeycomb core composite board be 0.1553 watt/(rice open), error is no more than 10%.

Embodiment 2: the thermal conductivity measurement that spins the synthetic fibre honeycomb core composite board

The material that spins the synthetic fibre paper composite board forms: sandwich layer is by the cellular board that spins synthetic fibre paper and make, and two side skins are rustproof aluminium sheet.It is made to sample by Fig. 4 size, be arranged on the frock shown in Fig. 3, after switching on power 50 minutes, 4 temperature sensor senses temperature that are placed in fully sheathed case keep stable, respectively:

t ₁=86.455℃,t ₂=86.455℃,t ₃=86.453℃,t ₄=86.455℃。

Environment temperature now:

T _o=20℃

By formula (6), obtained:

T _i=（86.455+86.455+86.453+86.455）/4=86.454℃

By formula (7), calculate to such an extent that coefficient of heat conductivity is:

Conclusion: the coefficient of heat conductivity of aluminium foil honeycomb core composite board be 0.0301 watt/(rice open), error is no more than 10%.

Claims (3)

1. a honeycomb composite plate test device of thermal conductivity coefficient, comprise the casing that a plank is made, it is characterized in that: the casing upper end open, between lower end and ground, by chock, isolate, cabinet wall covers thermal insulation material as liner, and filling with sealant between liner is settled an electric heater in the middle of the case inner bottom part, four jiaos a temperature sensor is installed respectively in casing, is usingd the average measurement value of four temperature sensors as the temperature inside the box T _i, a thermometer test environment temperature T is set outside casing _o, the wire of four sensors and electric heater is derived outside case by the card extender at the bottom of case, respectively outer temperature display meter and the power supply of connecting box; During test, using sample as the closed with covers box opening, and use rubber belt sealing.

2. honeycomb composite plate test device of thermal conductivity coefficient according to claim 1, it is characterized in that: the thickness of described plank is 10～25 millimeters; Described liner thickness is greater than 200 millimeters; The inductive head of described temperature sensor is apart from 90～100 millimeters of cabinet walls; Described chock thickness is over 100 millimeters.

3. a honeycomb composite plate Determination of conductive coefficients method of utilizing the described device of claim 1, it is characterized in that comprising the steps: to switch on power, the temperature inside the box shown when temperature display meter continue 30 minutes constant, think inside and outside casing and reached balance, record now temperature; Calculate coefficient of heat conductivity

in formula: W is heater power, and l is sample thickness, and S is sample efficiently radiates heat face, S=a ², a is the effective length of side of sample.

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