Thermal energy transfer associated with a change of phase can be a valuable phenomenon for engineers designing systems for electronics cooling. Solid to liquid phase change materials were described in the May 2005 Technical Data column and the topic for this issue is liquid to vapor phase change. The energy required to change a substance from a liquid state to a vapor state is … [Read more...]
Thermal Conductivity Of Liquid Metals
This column deals with the thermal conductivity and melting points of liquid metals. Thinking about liquid metals, many people associate them with high temperatures. It is not widely known that some metallic alloys are liquid below 0�C, with the exception of course of mercury which was already known in ancient times. China's first emperor is said to have been buried in rivers … [Read more...]
Thermal Properties Of Building Materials
Previous Technical Data columns have covered thermal properties for many of the materials that are common to electronics packaging. The Technical Data for this issue is broader in scope and addresses common building materials, some of which are used in heat transfer laboratory environments, in addition to their usual construction applications. Knowledge of thermal conductivity … [Read more...]
Thermal Effusivity
The Technical Data column of the previous issue discussed the concept of thermal diffusivity. It makes sense to discuss in this issue a related topic: thermal effusivity. While thermal diffusivity, a, is defined as the ratio between the thermal conductivity, k, and the volumetric thermal capacity, ρcp, the effusivity, e, is related to their product, as follows: It is … [Read more...]
Thermal Diffusivity
Thermal diffusivity is a measure of the transient thermal response of a material to a change in temperature and the term thermal diffusivity (α) is defined asα= k/(ρ x cp) where αis the thermal diffusivity (m2/sec) k is the thermal conductivity (W/m-K) ρ is the density (kg/m3) cp is the heat capacity (J/kg-K) It should be noted that each of these quantities can … [Read more...]
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