80A in a copper bar and Heat Transfer Coefficient calculation

[zorglub]

Hello everybody

I would like to calculate the temperature rise of a copper bar which carries a current of 80A.

I have all the relevant equations except one: the one that would give me the Heat Transfer Coefficient (h) of my bar.

Does someone know an easy way to calculate it for this case?

The only cooling medium considered is natural convection.

Thanks in advance for your answers.

FRED

 

[cuky2000]

The theorectical formula to calculate the Heat transfer Coefficient is: h = Lambda/Thickness

_{Were:
h = Individual heat transfer coefficient (W/m2·K) or (Btu/hr·ft2·°F)
Lambda = wall thermal conductivity. (W/m·K)
Thickness = laminar film of thickness (m).}


Since the thickness of the film is unknown and almost impossible to estimate this equation is usually rewritten as:
h = Q/[A.Delta(T)]

_{Were:
Q = Rate of heat flow or effective power loss.(W)
A = Bus heat-dissipating surface(m^2).
Delta(T) = Bus Temperature rise (T-Tw), (K)}

Few reference values for heat transfer coefficients are as follow:

Air:
- Natural convection………..….5.0 W/(m^2.K)
- Forced convection……………10-100 W/(m^2.K)
Switchgear:
- Lower half of cubicle……..……6 .0 W/(m^2.K)
- Entire cubicle(uniform dist)……4.5 W/(m^2.K)
- Lower half of cubicle…………..3.0 W/(m^2.K)
Insulated Conductor:
- Insulated conductor……..……9-40 W/(m^2.K)