calcolo dissipazione

Salve a tutti,

sapreste indicarmi un software online o free per il calcolo della resistenza termica di semplici dissipatori (es barre di alluminio)?

Grazie a tutti

0 Former Member over 15 years ago

Something like http://www.novelconceptsinc.com/calculators-cylinder-thermal-resistance.cgi ?
(or possibly something else from http://www.novelconceptsinc.com/calculators.htm?)
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0 Former Member over 15 years ago in reply to Former Member

Dear friend,
the link that you gave me is a web page that I know well, but I think that calculation of that program is completely wrong! For example from link http://www.novelconceptsinc.com/calculators.htm if you choose the chapter "Slab Thermal Resistance", with an alluminia dissipator (thermal conductivity 236 W/mK), with dimensions 360mmX200mmX4mm) the result is a thermal resistance of 2.35405e-04 C/W!
It' s absolutely impossible that the thermal resistance of this structure is so low
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0 Former Member over 15 years ago in reply to Former Member

Using R=I/k and Windows Calculator:

R = 0.004/236 = 1.6949152542372881355932203389831e-5 (4mm / 236w/m.K)

R/(0.36*0.2) = 0.0002354048964218455743879472693032 approximately 2.354x10^-4

(Both the website and myself may be wrong, though. Maths is not one of my stronger subjects!)
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0 lpetacchi over 14 years ago in reply to Former Member

Your calculation is correct. Thermal resistance in this case is between two planes of the object. "Dissipazione" refers to the capability to transfer heat (heat sinking) to the ambient, mainly by convection; this number is usually quite higher.
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0 Former Member over 14 years ago

Senza tante complicazioni io uso un metodo approssimativo ma efficace per superfici fino a circa 10x10 cm (200 cm²):
Rt = 1 / S x K
dove Rt = resistenza termica del dissipatore, in °C/W
S = superficie (totale, quindi entrambi i lati) della lamiera, in cm²
K = 0.003 per alluminio 3 mm superficie anodizzata; 0.0025 alluminio 3 mm naturale; 0.002 alluminio 2 mm naturale;
Se il dissipatore è un profilato alettato K = 0.0075 in aria ferma, K = 0.015 con flusso d'aria di 25 l/min
es. dissipatore piano 5x5 cm sp 3mm in aria ferma: S=50 cm², K= 0.0025, Rt = 8 °C/W
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