Heat Transfer Coefficient of air vs Velocity

shreesha87 · May 7, 2014, 20:21

The heat transfer coefficient of air is normally 100 W/m^2K at medium velocity.
And all know that the heat transfer coefficient is a function of air velocity. How high can the heat transfer coefficient increase with the velocity?

Shree

Rami · June 10, 2014, 03:08

Hi Shree,

The HTC (heat transfer coefficient) depends on the flow configuration (e.g., flow on a horizontal or vertical flat plat, flow in a duct, etc), the flow being developed or developing, laminar or turbulent, the Reynolds and Prandtl numbers and surface roughness. There are many correlations for the HTC (e.g., Dittus-Boelter) giving explicit relations for Nu (Re, Pr) for various configurations at given ranges of Re and Pr (see, e.g., Ozisik or Holman books). If you choose an appropriate correlation for your problem, you will be able to estimate the HTC.

May 7, 2014, 20:21	Heat Transfer Coefficient of air vs Velocity	#1
shreesha87 New Member Join Date: Oct 2013 Posts: 13 Rep Power: 12	The heat transfer coefficient of air is normally 100 W/m^2K at medium velocity. And all know that the heat transfer coefficient is a function of air velocity. How high can the heat transfer coefficient increase with the velocity? Shree

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June 10, 2014, 03:08		#2
Rami Senior Member Rami Ben-Zvi Join Date: Mar 2009 Posts: 155 Rep Power: 17	Hi Shree, The HTC (heat transfer coefficient) depends on the flow configuration (e.g., flow on a horizontal or vertical flat plat, flow in a duct, etc), the flow being developed or developing, laminar or turbulent, the Reynolds and Prandtl numbers and surface roughness. There are many correlations for the HTC (e.g., Dittus-Boelter) giving explicit relations for Nu (Re, Pr) for various configurations at given ranges of Re and Pr (see, e.g., Ozisik or Holman books). If you choose an appropriate correlation for your problem, you will be able to estimate the HTC.