Thermal conductivity tester experimental steps

definition

Thermal conductivity: The amount of heat transferred per unit area of ​​the material along the direction of heat flow per unit temperature gradient per unit time. The unit is watt per meter Kelvin [W/(m·K)].

Local heating is carried out with a linear electrical conductor () embedded in the sample along the length of the sample, carrying a current of known constant power, i.e., the power is constant over time and in the length direction of the sample. The thermal conductivity is calculated from the power and the on-current heating after two temperatures are known. The temperature rise is a function of the thermal conductivity of the sample being tested.

Suitable for all kinds of industrial materials, rubber tires, building materials, refractory materials, process materials, ceramic materials, food and so on.

1, sample preparation

The length of the sample is × 300 mm x 300 mm and the thickness of the sample is 25 mm. The sample is placed in the center sample cell.

2, the setting of instrument parameters

Make the appropriate settings for the controller as required.

3, data calculation

There are three forms of heat transfer for any object: heat transfer, heat radiation, and heat convection. Between each part of the fluid of different temperature fluids, heat transfer due to relative motion is called thermal convection. The movement of the microscopic particles of matter radiates energy in the form of light, called radiation.

Under the condition of temperature imbalance, there is temperature difference in the object, the heat energy distribution is not uniform, and the heat is transferred from the high temperature to the low temperature part without the macroscopic displacement inside the object. When the objects of different temperature are in contact with each other, there is also no material transfer. The heat transfer phenomenon, which is caused by the disordered motion of the microscopic particles of matter, is called heat conduction, also known as thermal diffusion.

According to the heat transfer theory, the heat flux perpendicular to the infinite plate direction is proportional to the temperature difference between the thickness d direction and the flat surface side, and the plate area is inversely proportional to the thickness of the plate.

T1 – t2

Q = λS --------------------- (1)

d

Where, Q—the heat transferred perpendicular to the plate direction is called the heat flow rate; t1-t2 is the temperature difference between the two sides of the plate; d—the plate thickness; S is the plate area. Λ—is a proportional coefficient called thermal conductivity. So the equation for thermal conductivity is as follows:

d

λ = Q ----------------- (2)

T1 - t2

The above formula is the equation of operation of the thermal conductivity. If the power P is used, P = kQ, k is a coefficient. If the P unit is W (Watt), the length unit is m, and the temperature unit is K (°C), the thermal conductivity unit is W/(mK). The thermal conductivity equation becomes:

W* d

λ = ------------------- (3)

S*( t1 – t2)

Equation (3) is the absolute measured thermal conductivity equation.