[O.SEUNG-MIN]

i have researching the natural convection inside vertical pipe
flows through the vertical pipe is driven by natural convection force

i am looking for inside surface heat transfer coefficient varying with diameter, length(GrL=3*10^8 - 4*10^10) and Prantdl number(0.7, 20, 2,014).
(wall condition is constant temp)

it is difficult to define reference temperature in pipe.

i made up the central line and apply the line average temperature for ref. temp.

is it make sence for develpoing region. or tell me another ways

thanks for all.

[O.SEUNG-MIN]

also i have gained very high heat transfer coefficient that i establish the high reference temp.

i think it is not make sence for thin, long pipe. it looks something was wrong.