Thermal transmittance question

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In summary, the conversation discusses the use of Kaowool Thermal insulation for a project and its values at 2000 F, 1.28 BTU, and .20 w/m*k. The person is asking for help to determine the temperature of a plate on the other side of the insulation when one side is in direct contact with a heat source at 2000 F. There are several factors that need to be considered, such as heat flow, insulation thickness, and dimensions of the rod.
  • #1
Tuatha
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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.
 
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  • #2
Tuatha said:
temperature of the plate would be on the other side of the insulation?
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
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
"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
Tuatha said:
insulation material sandwiched in the middle of the heat probe
to do anything.
 
  • #5
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
 

1. What is thermal transmittance?

Thermal transmittance, also known as U-value, is a measure of the rate of heat transfer through a material or assembly. It is expressed in watts per square meter per degree Celsius (W/m²K) and is used to quantify the thermal insulation properties of a building component.

2. How is thermal transmittance calculated?

Thermal transmittance is calculated by dividing the heat flow rate through a material or assembly by the temperature difference across it. It takes into account the thermal conductivity, thickness, and surface area of the material or assembly.

3. What factors affect thermal transmittance?

The factors that affect thermal transmittance include the material's thermal conductivity, thickness, surface area, and the presence of gaps or air pockets. The type of insulation, installation method, and environmental conditions can also impact thermal transmittance.

4. Why is thermal transmittance important?

Thermal transmittance is important because it determines the energy efficiency of a building or structure. A low thermal transmittance value indicates good insulation and reduces the amount of energy needed for heating and cooling, leading to cost savings and a smaller carbon footprint.

5. How can thermal transmittance be improved?

Thermal transmittance can be improved by using materials with higher thermal resistance, such as insulation, or by reducing air leakage through proper sealing and insulation installation. The design and construction of a building can also be optimized to minimize thermal bridging, which can significantly impact thermal transmittance.

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