thermal conductivity - is one of the main indicators of material properties, it is expressed by the amount of heat passing through the wall thickness of 1 m and an area of ​​1 m2 per hour with a temperature difference on the opposite surfaces of the wall 1 degree.

Measurement method



Driving device includes two massive metal block.The plate of the material and the contacting calorimeter placed between two blocks of the same thermal conductivity, the upper heated.After turning off the heater unit is installed between the heat flux close to stationary.It is measured using a heat flow meter.

If thermal insulation blocks, the side surface of the sample and the heat meter is ideal, which passes through the same heat flux.In actual conditions, the temperature unit is changed due to the heat flow through the sample.An annular layer
between the surface of the block and the sample can be filled with air or insulation, for example, foam or foam.

estimating uncertainty of measurement of thermal conductivity is carried out taking into account the sample heat exchange with the environment.Leakage flux from the side surface of the sample can be determined as the algebraic sum of the flows to the upper and lower end surfaces of the annular spacer.

At a certain ratio of the sample size and power leakage flux is a consequence of the asymmetry of the lateral heat exchange surface of the sample with the end portions of the annular layer.Deviation is not dependent on the thermal resistance of the material, is determined only by the geometrical dimensions of the calorimeter used.

design of the device for measuring the thermal conductivity of the metal



to the body of the device, consisting of two transverse frames, attach the top plate, as well as the skin of a thin steel sheet and flip.The top plate is installed calorimeter is opened by the lifting mechanism.Inside the enclosure is a transformer with the unit cold junctions.

near the contact surface is a thermocouple coated with an epoxy resin.It appears, first up the unit, and then to block the cold junctions across the hollow rod.The lower block mounted calorimeter consisting of a copper contact plate and a working layer of an epoxy resin.The first block is coiled heater routed to the front connector on the end.

United differential thermocouple designed to measure temperature changes in the sample.In height, they can move to within a few millimeters.Before measuring the contact surfaces of the blocks and the sample wiped with alcohol or gasoline, and then smeared with a thin layer of oil.