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 Fluu March 11, 2008 08:52

convective heat transfer coefficient

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/m²K at the stagnation point.

In an article about NASAs LEWICE, they maintain a value of hc=170 W/m²K.

In another article, there is a equation für 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/m²K

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

 ag March 11, 2008 09:11

Re: convective heat transfer coefficient

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.

 andromeda_sirius March 14, 2008 19:10

Re: convective heat transfer coefficient

you should check the reference value for temperature!

 P K SALONI April 15, 2008 07:37

Re: convective heat transfer coefficient

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.

regards,

p k saloni

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