# Thermal transmittance question

1. Feb 3, 2015

### Tuatha

I am looking Kaowool Thermal insulation for a project. It looks like the values presented are @2000 F, 1.28 BTU, .20 w/m*k

I was wondering if someone could help me to figure out what the "output" heat would be at 2000 F. For example: If I have an aluminum rod sitting over a fire burning at 2000 F, with this rod connected to a flat plate. In between this plate is the Kaowool Thermal insulation. On the other side of this insulation is another plate. So basically the insulation is sandwiched between two aluminum plates, with one side having an attached rod that is in direct contact with 2000 F. I would like to know what the temperature of the plate would be on the other side of the insulation? Any help? Thanks.

2. Feb 5, 2015

### Bystander

What temperature would you like it to be? You'll have to constrain your system further to generate any specific temperature: specify a heat flow, insulation thickness, other details.

3. Feb 5, 2015

### Tuatha

Well the heat source is around 1200-1500 degrees. Using a probe in the heat source I need to have the end of he probe no hotter than 500 degrees. I was wondering if the insulation material sandwiched in the middle of the heat probe would limit the heat flowing down the probe to less than 500 degrees.

4. Feb 6, 2015

### Bystander

"Heat flow" is measured in Watts, Joules/s, calories/s, BTU/hr, or some other energy unit per some time unit. Temperature is measured in degrees Kelvin, centigrade, Celsius, Rankine, Fahrenheit and no doubt other scales, and is independent of heat flow rates. Thermal conductivity (the quantity listed for the insulation) is measured in units of heat flow rate per units of area per units of temperature gradient (del T per thickness); area and thickness are combined to yield the usual W/(m⋅K), or BTU/(ft⋅hr).

I can engineer very small heat flows at very high temperatures, high heat flows at high temperatures, low heat flows at low temperatures, and high heat flows at low temperatures; I can't engineer
to do anything.

5. Feb 6, 2015

### Staff: Mentor

The answer to your question depends on the thicknesses of the plates, the thickness of the insulation, and the dimensions of the rod. If the insulation is a kilometer thick, for example, then the temperature rise on the plate away from the rod will not be significant.

Chet