For definition of heat conductivity of metals and alloys the stationary comparative method is used. The devices used to measurement of coefficient of heat conductivity work at its basis.
Heat conductivity — one of the main indicators of properties of material, it is expressed by the amount of heat passing through a wall 1 m thick and of 1 sq.m in one hour at the difference of temperatures on opposite surfaces of a wall in 1 degree.
Measurement method
The circuitry of the instrument includes two metal massive blocks. The plate of the studied material and the heat meter contacting to it are established between two blocks with identical heat conductivity, at the same time top is heated. After switching off of the heater between blocks the heat flux close to stationary is established. It is measured by means of the heat meter.
If thermal isolation of blocks, a side sample of a surface and the heat meter is ideal, through them there passes the identical heat flux. In actual practice temperature of blocks changes because of heat overflow through a sample. The ring layer between the surfaces of blocks and a sample can be filled with air or thermal insulation, for example, polyfoam or foam rubber. The assessment of an error of measurement of heat conductivity is carried out taking into account heat exchange of a sample with Wednesday. The dispersion stream from a side surface of a sample can be defined as the algebraic sum of streams to the top, lower and face surfaces of a ring layer. At a certain ratio of the sizes of a sample and blocks the stream of dispersion is a consequence of asymmetry of heat exchange of a side surface of a sample with face parts of a ring layer. The measurement error at the same time does not depend on the thermal resistance of the studied material, it is defined only by the geometrical sizes of the used calorimeter.
Device design for measurement of heat conductivity of metal
Attach to the case of the device consisting of two cross frames the top plate and and also coverings from thin sheet steel and the folding panel. On the top plate the calorimeter opening by means of the lifting mechanism is established. In the case of the device there is a transformer to the block cold having soldered. Near a contact surface the thermocouple covered with epoxy resin is located. She is brought at first up the block, then to the block cold having soldered through a hollow bar. The heat meter consisting of a contact copper plate and a working epoxy resin layer is installed in the lower block. In the first block there is a spiral heater brought to a front block at a face. The thermocouples connected differentsialno are intended for measurement of temperature drop on the studied sample. On height they can move within several millimeters. Before measurement the contact surfaces of blocks and a sample wipe with alcohol or gasoline, and then grease with a thin butter layer.