SI units for Heat transfer equation

In summary, the conversation is about trying to match up units on both sides of an equation concerning thermal diffusivity. The thermal resistivity, represented as "k", has units of Kelvin per watt. However, after research and discussion, it is determined that there is a missing factor of meters in the equation. There is also confusion about the units of seconds, but it is suggested to check the literature for clarification.
  • #1
jeff1evesque
312
0

Homework Statement


I am trying to get the units to match up on both sides. [tex]\frac{\partial T}{\partial t} = \frac{\nabla ^{2} T}{k} = \frac{1}{K}(\frac{\partial ^2 T}{\partial x^2} + \frac{\partial ^2 T}{\partial y^2} + \frac{\partial ^2 T}{\partial z^2}})[/tex], where k is the thermal resistivity.

The Attempt at a Solution


By searching all over the web, I've found that thermal resistivity "k" has units of [tex]\frac{Kelvins}{W}[/tex].

Therefore,

[tex]\frac{\partial T}{\partial t} = \frac{Kelvins}{s} \neq (\frac{W}{Kelvins})*(\frac{Kelvins}{m^2})[/tex]. Could someone help me correct the units.Thanks,JL
 
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  • #3
LowlyPion said:
This may be useful:
http://en.wikipedia.org/wiki/Thermal_resistivity

I think there needs to be a factor of m added to your statement.

Oh I see it now, but what about the unit for seconds "s"?
 
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  • #4
k is not the thermal resistivity, it's the inverse http://en.wikipedia.org/wiki/Thermal_diffusivity" .
 
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  • #5
Mapes said:
k is not the thermal resistivity, it's the inverse http://en.wikipedia.org/wiki/Thermal_diffusivity" .

Are you sure? I mean the units do infact check out if you are correct- but according to my class notes they've referred it to thermal resistivity.

Thanks a lot.

JL
 
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  • #6
It doesn't matter if I'm sure. :smile: Check the literature; ask your teacher for a reference.
 

FAQ: SI units for Heat transfer equation

1. What are SI units for heat transfer equation?

The SI units for heat transfer equation are joules per second (J/s) or watts (W) for the rate of heat transfer, kelvin (K) for temperature difference, and square meters (m^2) for surface area.

2. How do you convert from non-SI units to SI units for heat transfer equation?

To convert from non-SI units to SI units for heat transfer equation, we use conversion factors. For example, to convert from Fahrenheit (°F) to Kelvin (K), we use the formula K = (°F + 459.67) x (5/9).

3. Can you use different SI units for heat transfer equation?

Yes, you can use different SI units for heat transfer equation as long as they are consistent. For example, you can use joules (J) instead of watts (W) for the rate of heat transfer, but you cannot mix different units within the same equation.

4. Why are SI units important in heat transfer equations?

SI units are important in heat transfer equations because they provide a standard and consistent way to measure and calculate heat transfer. This allows for easier communication and comparison of results among scientists and engineers.

5. Can you use non-SI units in heat transfer equations?

Yes, you can use non-SI units in heat transfer equations, but it is recommended to convert them to SI units for consistency and easier comparison with other results. Some common non-SI units used in heat transfer equations are BTU (British thermal unit) and cal (calorie).

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