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# Unit of the Thermal conductivity

Legend

Dear SE user,

I want to place the thermal conductivity of POM-C in the materials.

Problem here, the valvue is in 0,3 W/(mK). So Watt per meter Kelvin.

Solid Edge use a strange unit because it is not according SI-units, they use W/(m-C).

As far I can see the unit for the Thermal Conductivity must be in W/(mK) or W/m/K.

Why does SE not use the normal SI-units?

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Daniël Schuiling
6 REPLIES 6

# Re: Unit of the Thermal conductivity

Gears Honored Contributor

This seems both to have been left out and a bug as well.

Changing the base unit for temperature from C to K affects Coeff. of Thermal Expansion to change from /C to /K but not in case of Thermal Conductivity.

Most units with temperature in the numerator get changed for e.g. Temperature Gradient, but not those in the denominator.

For Thermal Conductivity, K seems to be simply left out.

# Re: Unit of the Thermal conductivity

Legend

What I have learned is that Kelvin is the standard unit for temparature.

I have tried to change the 0,3 W/(m*K) to W/(m*C). I think it is also 0,3 W/(m*C).

0,3 W/(m*K) is 0,003 W/(cm*C), this should result in 0,3 W/(m*C).

Is in SE the W/(m-C) the same as W/(m*C)?

But Siemens should really change the units to SI-units ASAP.

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Daniël Schuiling

Legend

# Re: Unit of the Thermal conductivity

Phenom

1 degree change in Kelvin is identical to as 1 deg Celcius i.e. they both have 100 divisions between the temperature that water freezes at (0 C) and boils at (100 C). It's just that kelvin starts 0 at absolute zero (-273 C).

Anyway, the upshot of that is that the units W/mC and W/mK are identical.  Also although Kelvin is an SI base unit, Celcius is an SI derived unit in the same way that a Watt is so I don't really see any fault on Solid Edge's part.

# Re: Unit of the Thermal conductivity

Solution Partner Pioneer
I think the unit K is only introduced to me in college...while it is technically the SI Unit, Celsius makes more sense in day to day usage

# Re: Unit of the Thermal conductivity

Legend

@Alex_H, you are wrigth. Forgot that part about a change per temperature degree is the same for Celcius and Kelvin. Thank you for the reminder

@Edward, many formulas in the energy study (do not know the exact English word for it) are based on Kelvin.

If there need to be standards than it is the best to follow the SI-units. Why else would you use the specific Heat in J/(kg*K) and for the Coefficient of Thermal Expansion a value per C?

The logic is gone if Siemens use different units for temperature.

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Daniël Schuiling