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Old   March 11, 2008, 07:52
Default convective heat transfer coefficient
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Hello everybody! I want to calculate the convective heat transfer coefficient of a cylinder with Fluent. - diameter of the cylinder : d = 0,1524 m - temperature of the cylinder: Tcyl = 273,15 K - temperature of the airflow: Ta = 268,30 K - air velocity : u = 90 m/s - air pressure : p = 100 000 Pa - y+ : between 20 and 50

at "XY Plot" - "Wall Fluxes" - "surface heat coefficient" I receive a value hc=90 W/mK at the stagnation point.

In an article about NASAs LEWICE, they maintain a value of hc=170 W/mK.

In another article, there is a equation fr the coefficient for a cylinder: hc = thermal conductivity * Nusselt number/diameter with Nusselt Number = 1,14 * (Prandtl^0,4)*(Reynold^0,5); there you get a value hc = 165 W/mK

Do I have to consider something tricky with fluent because my value is pretty low?

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Old   March 11, 2008, 08:11
Default Re: convective heat transfer coefficient
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Heat transfer is very sensitive to the y+ value used. You are probably going to need to reduce your y+ down substantially to get a good value (possibly down as low as 0.1-0.2). No trickery involved, just getting good resolution of the temperature gradient.
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Old   March 14, 2008, 18:10
Default Re: convective heat transfer coefficient
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you should check the reference value for temperature!
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Old   April 15, 2008, 07:37
Default Re: convective heat transfer coefficient
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Dear sir,

I want to calculate the convective heat transfer coefficient of a cylinder casing with temperature 200 deg c, tempearature of air flow outside the casing will be 45 deg c with humidity 95%, please assist me in this regard to proceed with calculation by providing reference material or sample calculations.


p k saloni
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