木材中导热系数检测方案(导热仪)

智能文字提取功能测试中

京都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD.APTM-0135en APTM-0135en Wood Thermal Conductivity Measurement Industry Ceramic Instrument Quick Thermal Conductivity Meter Measurement method Hot wire comparative method Standard 1. Scope Wood is made up of tissues consisting of countless cells which have air in the voids in the cells，so density is low and thermal conductivity is only about 1/10 of that of concrete. Also wood hasdense annual growth ring structures， and it is not a homogeneous material. For such an uneven structure， the thermal conductivity is expected to be different between thematerial along the direction of the grain and that of perpendicular to the grain. In this study， we measured with the probe oriented in the direction of the wood grain and in thedirection perpendicular to the wood grain. We examined whether the thermal conductivity differsaccording to the direction to which the probe is mounted. 2.Precautions Avoid trapping air between the sample and the probe when setting. If pockets of air exist， they will affect the thermal conductivity measurement result. · Prepare a flat specimen with no irregularities or undulations on the sample surface. · If there is dust on the sample surface or probe， wipe it off. For the amount of heat applied to the sample， determine the heater current value so that thetemperature rise during measurement is 5 to 20 °℃. Set the heater current value from [HEATER] on the main unit and select the heater current valueto be used according to the sample. Excessive heating may cause breakage of samples andreferences. Refer to the instruction manual for current value guidelines. Measure the sample by allowing it to fully conform to the measurement environmentaltemperature. 3. Apparatus Main unit Quick Thermal Conductivity Meter (Normal Measurement)Probe PD-11N(Box type probe) 4. Procedure 1) Place the probe on the sample. 2) Apply constant power (calories) to the heater and at the same time record the change intemperature rise to obtain the thermal conductivity. NOTE： Refer to the instruction manual for details. 上海市徐汇区宜山路333号1201室网址： http：//www.kem-china. com 5. Example -Measurement principle- Our Quick Thermal Conductivity Meter is a thermal conductivity meter that can performsimple and quick measurement with excellent operability. Measurement begins when the probeis pressed (Fig. 1) against a sample surface of uniform temperature， and the operation can becompleted in just 60 seconds. The probe consists of a linear heating element and a thermocouple， and as the constant power(calories) is continuously applied to the heaterx71r， the temperature of the heater rises exponentially.When the time axis uses a logarithmic scale， the temperature rise curve becomes a straight line(Fig.2). The slope of this straight line increases with lower sample thermal conductivity， and if thesample has high thermal conductivity， the slope decreases. In other words， the thermalconductivity of the sample can be obtained from the slope of the temperature rise graph inwhich the horizontal time axis has a logarithmic scale. Low thermal conductivity High thermal conductivity Fig1.Probe Fig 2.log(t)vsTemp. graph -Measurement conditions- ：oAmbient condition 23℃ oHeater current value 1.0A oMeasurement time 60 seconds -Measurement results- Shown are the measurement results for the thermal conductivity of wood. For the measurements， we attached the probe to the sample and then removed the probe on eacliteration. Measurement was performed three times. Table 1 shows average value， standard deviation and relative standard deviation. Table 1. List of wood measurement results Wood Measurement Measurement point B Measurementpoint C Measurement point D point A Thermal conductivity 2 (W/(mK)) 0.1106 0.1112 0.1084 0.1628 0.1419 0.2987 0.3135 0.2959 0.1649 0.1628 0.1434 0.1421 Mean value 0.1101 0.1635 0.1425 0.3027 Standard deviation 0.00147 0.00121 0.00081 0.00946 RSD (%) 1.3 0.7 0.6 3.1 Measurement point A Measurement point B Measurement point C Measurement point D NOTE： Measurement point A：The probe was placed parallel to the wood grain(the heat flow was perpendicular to the grain)Measurement point B：The probe was placed perpendicular to the wood grain(the heat flow was parallel to the grain)Measurement point C：The probe was placed at 45C to the wood grain(the heat flow was 45 ℃ against the grain)Measurement point D：The probe was placed on a knot in the wood grain. 6. Summary Good accuracy was confirmed in which the relative standard deviation of wood wasapproximately 0.5 to 3.0%. It was also confirmed that the thermal conductivity is different according to the grain direction，as the thermal conductivity was 0.11 W / m K for the case parallel to grain direction，and 0.16 W/mK for the perpendicular orientation. It was demonstrated that， for a sample whose thermal conductivity differs in one direction toanother perpendicular direction， such as wood， changing the set position of the probe with theQuick Thermal Conductivity Meter enables confirmation of the differences in in-plane thermalconductivity. For other samples， verification is separately required； in such cases please consult us asnecessary. 7.References None. 上海市徐徐区宜山路333号1201室网址： http：//www.kem-china.com 电邮： kemu-kem@com/ 都電子工業株式会社KYOTO ELECTRONICSMANUFACTURING CO.，LTD. 木材导热系数的测定 木材是由数不清细胞组成的组织，在细胞的空隙中有空气，所以密度很低，导热系数只有混凝土的1/10左右。此外，木材具有密集的生长年轮结构，而且它不是一种均匀的材料。对于这种不均匀的结构，材料平行方向的导热系数与垂直方向的导热系数是不同的。在本研究中，我们用平行于木纹方向和垂直于木纹方向的传感器进行测量。根据传感器的方向，我们检查热传导率是否不同。 其中木材的相对标准偏差约0.5-3.0%为良好的准确度。还证实，根据方向不同，热传导率是不同，因为对于平行于方向的情况而言，导热系数为0.11W/mK，而垂直方向的导热系数为0.16 W/mK。