ISO 8302 Thermal Insulation - Determination of Steady State Thermal Resistance and Related Properties - Shielded Hot Plate Apparatus

The standard "ISO 8302 Thermal insulation - Determination of steady-state thermal resistance and related properties - Shielded hot plate apparatus" published by the International Organization for Standardization (ISO) describes a test method that describes the use of the shielded hot plate method to measure steady-state heat transfer through flat plate specimens and to calculate heat transfer properties. This method is an absolute or primary method of measuring heat transfer properties, as only measurements of length, temperature and electrical power are required.

If the samples meet only the requirements specified in clause 1.8.1 of this standard, the resulting properties are defined as the thermal conductivity and thermal resistance or transfer factor of the sample.

If the samples meet the requirements specified in clause 1.8.2 of this standard, the resulting property is defined as the measurable average thermal conductivity of the evaluated sample.

If the samples meet the conditions specified in clause 1.8.3 of this standard, the resulting property is defined as the thermal conductivity or permeability of the material under evaluation.

For the purposes of this standard, the following terms and definitions apply:

Thermally homogeneous medium: Thermal conductivity is not a function of position in the medium but can be a function of direction, time and temperature.
Thermally isotropic media: A situation in which thermal conductivity is not a function of direction, but may depend on the location of the medium, time, and temperature.
Thermally stable medium: A condition in which thermal conductivity is not a function of time, but can be a function of coordinates, temperature, and direction when applicable.
Average thermal conductivity of a sample: It is the property defined under steady-state conditions in a body in the form of a plate bounded by two parallel, flat isothermal surfaces and adiabatic edges perpendicular to the surfaces.
Transfer factor of a sample: Depends on the experimental conditions and characterizes the sample in relation to combined conduction and radiation heat transfer. Elsewhere it is often referred to as the measured, equivalent, apparent or effective thermal conductivity of a sample.
Thermal conductivity of a material: Defined by the case where thickness is independent. It is independent of experimental conditions and characterizes an insulating material in terms of combined conductivity and radiation. Thermal conductivity can be viewed as the limit to which the transfer factor reaches in thick layers where conduction and radiation heat transfer occur together. Elsewhere it is often referred to as the equivalent, apparent or effective thermal conductivity of a material.
Steady-state heat transfer property: General term used to describe one of the following properties: thermal resistance, transfer factor, thermal conductivity, thermal resistivity, thermal transmittance, thermal conductivity, average thermal conductivity.

Heat transfer properties of a material sample,

May vary due to variation in composition of the material or its samples.
May be affected by humidity or other factors
Changes over time
May vary depending on average temperature
Depends on thermal history

It should therefore be recognised that the selection of a material's typical heat transfer property value for a particular application must be based on consideration of these factors and will not necessarily apply without modification to all service conditions.

For example, this method assumes that heat transfer properties will be obtained on dried samples, but such conditions may not be met during use. More fundamental is the dependence of heat transfer properties on variables such as mean temperature and temperature difference. These dependencies must be measured or tests must be performed under conditions specific to the use.

A sufficient amount of test information is required to be considered representative of the heat transfer properties of a material. The heat transfer properties of a material can only be determined by a single measurement if the sample is material specific and the samples are sample specific. The procedure for selecting a sample should normally be specified in the material specification. Selection of a sample from a sample may be partially specified in the material specification. Since sampling is outside the scope of this test method, if the problem is not covered by a material specification, appropriate documentation is taken into account.

Assessing the accuracy of the method is complex and is a function of the instrument design, the instrumentation involved, and the type of sample being tested. However, instruments constructed and operated according to this method can measure heat transfer characteristics with an accuracy of plus or minus 2 percent when the average temperature of the test is near room temperature.

Our organization, which has been trying to support businesses from every sector with its testing, measurement, analysis and evaluation studies carried out in a wide range for years, has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. In this context, testing services in accordance with the "ISO 8302 Thermal insulation - Determination of steady state thermal resistance and related properties - Protected hot plate apparatus" standard are also provided to businesses.