1. Summary

The thermal conductivity is a significant parameter for researching physical properties of a material. In aviation area, atomic energy area, and industry department of building material or non-metallic material, an actual measurement or a forecast is required for the related material. There are steady testing method and dynamic testing method. The equipment adopts modified guarded hot plate method which is in line with the national standard. The whole testing process is finished either automatic or manual which satisfied the requirement of a high precision test. Reference standard: GB/T 10294-2008.

1. Technical features

Applications: The equipment applies to test the thermal conductivity of clintheriform homogeneous material under dry or different moisture conditions. Thermal conductivity range: 0.015-2 W/M*K

1. Can complete the test of plate method. The experiment temperature of equipment can be controlled. Temperature range: room temperature - 80℃.
2. Digitizing: Instrument temperature degree better than 0.2, room temperature compensation automatic electronic. May also adopt external freezing temperature compensation.
3. Power supply：220V/50HZ; Adopt high precision regulated power supply.
4. The result accuracy：  ±3%

repeatability：  ±2%

1. Metering heating power is adjustable, constant current output 0-3A，150v; accuracy: ±1%.
2. Have connected PC, can accomplish computer automatic testing. Under the steady state conditions, it only 3 minutes to test one set of data.
3. Can display the experiment parameters and curves.
4. Can be done through a variety of test methods; make a reference and help to further comparative study on the properties of material thermal conductivity.
5. The working conditions:

①Environment temperature: 10°～35℃

②Relative humidity: ≤80%RH

③Require to operate in the condition of a stable room temperature. The average daily temperature fluctuations ≤±1.5℃

1. Sample size and the effective area requirements：  300×300×(10-40) mm
2. Required the surface between the sample and the plate is flat and level. (Which can be connected by thermal conductive paste)

1. Instrument composition

Instrument consist of the built-in high precision regulated power supply, thermometer, hot plate heater, the main protection of hot plate, temperature measuring thermocouple, cold plate constant temperature water bath, computer testing system.

a. Specimen part: including constant temperature device, through room temperature to 80℃

b. Heating system: heater of guarded hot plate temperature and heater of measuring power.

c. Temperature measurement system: adopting the high precision digital display instrument to ensure the accuracy and stability, and realize zero internal compensation.

d. measuring power adopting constant heating and digital display, the accuracy is better than 1%.

e. computer test parts including touch screen, communications components, and software.

f. instrument panels and the various parts see figure 1:

（Figure 1）

1、Power switch     2、Work stop     3、Work start     4、Power light    5、Power regulation

6、Touch screen    7、Samples room     8、Cold plate lifting knob      9、Base seat   

10、Rolling wheel

1. Operating steps

1. Specimen preparation

Preparing samples according to the following requirements:

①Sampling should be homogeneous parts from the sample material.

②Sampling size is not greater than 300 x 300 x (10 ~ 40) mm

③Smooth the sample’s surface after sampling.

④Two surfaces of the specimen should be parallel, and uniformity of thickness. When testing，the surface of sample should be in contact with the plate flat and tight. If contact is not good, can coat the sample surface with a layer of powdery materials of the same material or high temperature heat conduction glue (cannot contain impurities and dust).

⑤Before the test, sample thickness must be measured with a vernier caliper and accurate to 0.01 mm. Or use other ways to measure the sample thickness, detect four points on the sample and calculate for average thickness (unit mm), and record it for use during the test.

⑥When the sample is foam or cotton of easily compressed material, please prepare four cylindrical solid pillars according to the thickness of the sample, used for testing.

1. Sample test method
   • Sample loading:

Turning cold plate lifting handle and lower cold plate down, then place the sample on the center of the cold plate. If the sample is foam or cotton (easily compressed material), placing the four cylindrical solid pillars which has be prepared before in the corners of the sample, in order to prevent compression tight sample when rising cold plate.

② Set the thermostatic water bath temperature

Open the power switch, cycle switch,, heat switch, cooling switch of the thermostatic water bath  (see figure 2).

a、power 

b、cycle

c、cooling

d、set

e、up

f、down

Press “set" button on the thermostatic water bath plate, enter temperature setting mode (digital section indicates “PV", “SV" section displays the setting temperature), now press “up" or “down" to change the setting temperature. After done with setting, press “set" to finish (usually set as 20C).

1. experiment mode

Rotate the power knob on the equipment to power on. Now the touch screen is on and enters the start interface. Click “enter" to enter the experiment interface. At the same time, press “start" button on the equipment. Touch the “start experiment" button on the screen. Wait until the temperature display section shows data, click and set the experimental temperature (usually 40?C) for the hot plate. Fill out the thickness of the sample, system will enter the experiment mode.

1. Adjust voltage

When equipment starts “experiment mode", the temperatures of the major hot plate, guarded hot plate, and cold plate will display on the surface. Wait and observe the temperature change. When the temperature is stable (change amount ≤±0.3?C), observe the temperature differences between the major hot plate and the guarded hot plate (usually ≥0.2?C). Rotate “adjust voltage" knob clockwise. Observe the data displaying on the surface. Stop rotating when it shows about 3V and observe the temperature change. When the temperature is stable, observe if the displaying data close to the temperature of guarded hot plate (error less than ±0.2?C). If is, adjust voltage is accomplished. If not, rotate “adjust voltage" again and add more appropriate amount of voltage (adjustment according to the temperature difference between major and guarded hot plate, if the difference is large, adjust 3-5V more; if small, adjust 1-3V more) judge whether the two temperature are balance after the data is stable. When they are overheated, reduce the voltage immediay. Adjustment of voltage does not have to be integer.

1. testing

When the temperatures of major and guarded hot plates are balanced, system would prompt a dialog box suggesting the temperatures are balanced. Click “ok" and click “start testing" to enter the testing mode. Wait about 3 min, the system will calculate one data. When obtained 4 data, the system will automatically calculate an average value.

When the average value comes out, users should wait 10-30min to click the “finish testing" and finish the test. After done with the testing, users could back to the initial surface. Rotate the “adjust voltage" to minimum (zero), press “stop" button on equipment, and turn off the power.

1. tips

1. When the thermostatic water bath sink is not filled with medium, do not turn it so it will not burn down the heating component.
2. Interior parameters are set correctly before leaving factory, do not adjust freely.
3. Turn off the power for all components, rotate the “adjust voltage" knob to zero, take the sample out, and clean the place where sample was. Do not scrub with hard objects.
4. Check the connection of all lines once in a while. If the system is testing but all temperature data is zero, it might be because the connection is failed.

1. data process and output

1.  The testing system bases on the guarded hot plate apparatus and made some improvements on the mathematic model; adopts PC to test with the mathematic model.
2. The method is on the basis of the measurements of heat transfer for two sides of the sample under the stable temperature condition to calculate the thermal conductivity coefficient.
3.  Formula

入== =  (unit: W/m.k)

I: heating current (A)

U: heating voltage (V)

d: sample thickness (m)

S: sample valid heating area (m2)

?Z: measure time interval (h)

?T: average temperature difference between two sides of the sample (? C)

Results should be accurate to three significant digits after the decimal point.

1. The test requires accurate sample preparation to make sure the accuracy of the final result.
2. When connecting external power source, ensure the reliability and grounding performance is good.

1. Product list

1. Testing host machine                        1
2. High accurate thermostatic water bath           1
3. Testing software (built-in in system)            1
4. Operating manual                           1
5. Certification of quality                       1