Heat transfer co-efficient of air
Heat transfer co-efficient of air
(OP)
All
I have been using a heat transfer co-efficient h = 5 W/m^2 K for free convections from a flat surface. Does anyone have a graph or literature which gives the h values of air relative to air velocity and temperature for a flat surface?
Thanks in advance
Chinmoy
I have been using a heat transfer co-efficient h = 5 W/m^2 K for free convections from a flat surface. Does anyone have a graph or literature which gives the h values of air relative to air velocity and temperature for a flat surface?
Thanks in advance
Chinmoy





RE: Heat transfer co-efficient of air
TTFN
RE: Heat transfer co-efficient of air
h=k/d*0.25*Re^(0.6)*Pr^(0.38)
where k is air conductivity and d is pipediameter and the velocity is the velocity of the wind. he refer to an article by J.P. Holman (1989) - maybe that a lead?
Perry has something for a flat plate (sec 10 p 16 in 6ed)- but only valid for laminar flow, Re up to 1000-100000 and Pr>0.6.
Here Nu=^0.648*Re^0.5*Pr^0.333
Best regards
Morten
RE: Heat transfer co-efficient of air
For a horizontal plate facing upward, J.P. Holman gives
values for free convection from surfaces to air, W/(m2×oC), table 7-2:
h = 1.32(ΔT/L)0.75 for laminar cases, and
h = 1.43(ΔT)1/3 for turbulent cases
where
ΔT = Twall-T∞ , oC
L = horizontal dimension, m
Turbulence is for Gr.Pr > 109
For a horizontal heated plate facing downward or cooled plate facing upward:
h = 0.61(ΔT/L2)0.2
RE: Heat transfer co-efficient of air
RE: Heat transfer co-efficient of air