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heat flux
Posted Nov 12, 2009, 11:29 a.m. EST 1 Reply
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Hi everybody, I need to modelize a vertical upward heat flux in a rectangle subdomain. I tried to put the condition "heat flux" at the superior bounary and a fixed temperature on the bottom boundary, but I obtain as a result that the heat flux is concentrated next to the upper boundary, and there is no heat flux inside the whole subdomain. Have you an idea of how could I do??
Please help me, it's very very important!!
thank you very much,bye
Please help me, it's very very important!!
thank you very much,bye
1 Reply Last Post Nov 14, 2009, 5:36 a.m. EST
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Posted:
2 decades ago
Hi
I repated what you wrote, with [htgh], apart perhaps that I split my rectangle a couple of times to have some interiour boundaries to calculate the heat flux over, then I put a constant teperature on the top surface, default insulated symmetry on the lateral sides and a negative heat flux on the bottom side (extraction of energy). Air in the middle.
I then solve, default settings and check the heat flux "ndflux_htgh" on the internal boundaries (split lines horizontal across my rectangle and normal to he expected flux), and I get the defined heat flux value correct to some 5-6 digits.
If I change the sign of the boundary heat flux I get the same, but opposed sign heat flux on the interiour (and external) boundaries in [W/m] where meter is the 2D depth
My temperature gradient is also nicely regular and horizontal. I must admit that I have not checked the calculated temperature values, but as I used the library Air for p=1[atm] I hope the difference of temperature for the two cases of +/-1[W/m] are correct, quite a large difference, but the physical air parameters are not that linear between -30 and +30 °C.
By the way I was NOT using radiative exchanges.
So i suppose you got something else wrong, many buttons in there I agree, it's easy to get something wrong
Good luck
Ivar
I repated what you wrote, with [htgh], apart perhaps that I split my rectangle a couple of times to have some interiour boundaries to calculate the heat flux over, then I put a constant teperature on the top surface, default insulated symmetry on the lateral sides and a negative heat flux on the bottom side (extraction of energy). Air in the middle.
I then solve, default settings and check the heat flux "ndflux_htgh" on the internal boundaries (split lines horizontal across my rectangle and normal to he expected flux), and I get the defined heat flux value correct to some 5-6 digits.
If I change the sign of the boundary heat flux I get the same, but opposed sign heat flux on the interiour (and external) boundaries in [W/m] where meter is the 2D depth
My temperature gradient is also nicely regular and horizontal. I must admit that I have not checked the calculated temperature values, but as I used the library Air for p=1[atm] I hope the difference of temperature for the two cases of +/-1[W/m] are correct, quite a large difference, but the physical air parameters are not that linear between -30 and +30 °C.
By the way I was NOT using radiative exchanges.
So i suppose you got something else wrong, many buttons in there I agree, it's easy to get something wrong
Good luck
Ivar