I want to add a heat exchange between two surfaces in my heat transfer analysis. Im using ECHANGE_PAROI and I must give three data, two meshes that correspond to the thermal contact surface and a heat exchange coefficient (COEF_H).

The value of COEF_H can be obtained with the formula:

H = W/A,

where W is the thermal contact conductance (watt/ kelvin) and A is the thermal contact surface (m^2).

The question is, for code_aster the area is implicit?, that is, only give to aster the value of W (thermal contact conductance w/k) and aster automatically recognize the area of heat exchange given the two meshes (case 1 ) or give the value of H calculated with the above formula (case 2)?

example:

if Area = 3.97e-3 m^2 and W = 0.0017 (w/k)

case 1

H = W = 0.0017 (w/k)

case 2

H = W / A =(0.0017/3.97e-3) = 0.434 (w/m^2 k)

the reason of this question is because code aster defines the radiation by rad = sigma*epsilon*(Text^4 - T∞^4)

and not by rad = sigma*epsilon*Area*(Text^4 - T∞^4)

what is the correct way to apply heat exchange between two surfaces?

best regards,

Max