The rate of cooling of a material in air, or with no barrier between materials

[andythecc]

I'm unsure how to approach this, as solid blocks of materials next to each other (e.g. steel and air) with no barrier inbetween as shown on
http://en.wikipedia.org/wiki/Thermal_conductivity
"x" would equal zero, this can't be correct. Is there another equation relating temperature difference, area and conductivity of two adjacent materials? Possibly also mass, volume or density? All I really want is a rate of heat loss via conduction in Watts or Watts/m². I know how to calculate Black Body ratiation via the Stefan-Boltzmann constant.

 

[mgb_phys]

The thermal conduction of a junction is a little different
Assuming both surfaces are clean and smooth it largely depends on pressure.

see http://en.wikipedia.org/wiki/Thermal...ct_conductance

 

[charng]

I would approach this question by first clarifying the concept of thermal conductivity and how it relates to the rate of cooling of a material. Thermal conductivity is a measure of a material's ability to conduct heat, or in other words, how easily heat can flow through the material. The higher the thermal conductivity, the faster heat can be transferred through the material.

In the scenario described, where there is no barrier between materials, the rate of cooling would depend on the thermal conductivity of the two materials in contact with each other. The rate of heat loss via conduction would be determined by the temperature difference between the two materials, the surface area of contact, and the thermal conductivity of the materials.

To calculate the rate of heat loss via conduction, we can use the equation Q/t = kA(T1-T2)/d, where Q/t is the rate of heat transfer, k is the thermal conductivity, A is the surface area, T1-T2 is the temperature difference, and d is the distance between the two materials.

In this equation, the thermal conductivity and the temperature difference play a crucial role in determining the rate of heat loss. The larger the temperature difference, the faster heat will flow from the higher temperature material to the lower temperature material. Similarly, a higher thermal conductivity will result in a faster rate of heat transfer.

It is important to note that the value of x in the Wikipedia example is not zero, but rather the thickness of the material. This value is taken into account in the equation by the variable d.

In summary, the rate of cooling of a material in air, or with no barrier between materials, can be calculated by considering the thermal conductivity, temperature difference, and surface area of contact between the materials. Other factors such as mass, volume, and density may also impact the rate of cooling, but they are not directly included in the equation for heat transfer via conduction.