Thermal Conductivity Unit Conversion

[OSHMUNNIES]

The problem I have is one of geothermics, specifically...and I considered posting this in the earth science section, but I figured you physicists might be of more assistance with this:

 

I am working on converting thermal conductivity (k) values for various rocks and minerals from W/m*C (Watts meters^-1 degrees Celsius^-1) to W/m*K (Watts meters^-1 degrees Kelvin^-1).

 

Here's an example:

Source 1 gives k_granite = 2.4 W/m*C

Source 2 gives k_granite = 3.0 W/m*K

 

So, acknowledging that 1C = 274.15K, dividing 2.4/274.15, canceling C for K...the answer 0.00875 W/m*K is of course nowhere NEAR 3.0 W/m*K.

 

Am I doing something wrong? Or has one of these sources mislabeled the units (this seems plausible, since 2.4 and 3.0 are fairly similar values, especially considering the fact that many different types of granites exist)?

[swansont]

The problem I have is one of geothermics, specifically...and I considered posting this in the earth science section, but I figured you physicists might be of more assistance with this:

 

I am working on converting thermal conductivity (k) values for various rocks and minerals from W/m*C (Watts meters^-1 degrees Celsius^-1) to W/m*K (Watts meters^-1 degrees Kelvin^-1).

 

Here's an example:

Source 1 gives k_granite = 2.4 W/m*C

Source 2 gives k_granite = 3.0 W/m*K

 

So, acknowledging that 1C = 274.15K, dividing 2.4/274.15, canceling C for K...the answer 0.00875 W/m*K is of course nowhere NEAR 3.0 W/m*K.

 

Am I doing something wrong? Or has one of these sources mislabeled the units (this seems plausible, since 2.4 and 3.0 are fairly similar values, especially considering the fact that many different types of granites exist)?

 

There's no difference, since it's a term that depends on a change in temperature. ºC and Kelvins (not degrees Kelvin) are offset from each other, but for a temperature difference that doesn't matter; a temperature change of 1 ºC is a change of 1K.

 

1 W/m*C = 1 W/m*K

[alpha2cen]

The problem I have is one of geothermics, specifically...and I considered posting this in the earth science section, but I figured you physicists might be of more assistance with this:

 

I am working on converting thermal conductivity (k) values for various rocks and minerals from W/m*C (Watts meters^-1 degrees Celsius^-1) to W/m*K (Watts meters^-1 degrees Kelvin^-1).

 

Here's an example:

Source 1 gives k_granite = 2.4 W/m*C

Source 2 gives k_granite = 3.0 W/m*K

 

So, acknowledging that 1C = 274.15K, dividing 2.4/274.15, canceling C for K...the answer 0.00875 W/m*K is of course nowhere NEAR 3.0 W/m*K.

 

Am I doing something wrong? Or has one of these sources mislabeled the units (this seems plausible, since 2.4 and 3.0 are fairly similar values, especially considering the fact that many different types of granites exist)?

 

At 1^oC and 2.4W/m.^oC , the two ^oC are different each other. The front ^oC meaning is that the temperature position is 1 ^oC from the 0 ^oC, the latter ^oC meaning is that del ^oC =1^oC, i.e., the temperature difference is 1^oC.

So del1 ^oC =del1 K . We customarily do not write the two ^oCs differently each other.

Edited March 18, 2011 by alpha2cen

[OSHMUNNIES]

Interesting...none of the literature I've read so far even mentioned that the temp. terms denoted a change and not a particular value, so thanks for the replies...makes perfect sense.

[swansont]

Interesting...none of the literature I've read so far even mentioned that the temp. terms denoted a change and not a particular value, so thanks for the replies...makes perfect sense.

 

Heat transfer depends on a temperature difference, so that's what always shows up in the equation.