Scaling heat transfer

[dbecker]

Hello all,

Does anyone know of a way to scale a heat transfer coefficient with respect to fluid density?

Although Reynolds is dependant on density, allow that to fall out.

Say I have an HTC = 5, I now change the density of the fluid by 16%, what will be my new HTC assuming the Reynolds number changed and Prandtl and so on... I am looking for a basic correlation.

Thank you,

- D

 

[IRstuff]

I think that it will depend...

The density does not directly appear in any of the standard equations for calculating transfer coefficients. Density may indirectly affect thermal conductivity, which does appear in the equations, so the real question is whether your thermal conductivity changed.

TTFN

FAQ731-376

 

[vpl]

Why did your density change? Did your temperatures also change?

Patricia Lougheed

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[IRstuff]

The linked document may be of use

http://files.engineering.com/getfil...ma203_Forced_Air_Cooling_at_High_Altitude.pdf

TTFN

FAQ731-376

 

[dbecker]

vpl, hello.

My temperature did not change, that is the beauty of this problem. It is not PV=nRT.

The environment is not 'sealed' so to speak. Imagine a chamber that got moved from sea level to 2000 m above sea level. Imagine it is winter, and this chamber has vents to let air in. The air at 2000 m will be less dense but assumed to be the same temperature as sea level (for my problem). I just need to know if the heat transfer coefficients I am producing can be scaled by any means after density has changed, although Temperature and all other properties remained the same.

Thank you again.

-D

 

[Yonathan]

heat transfer coefficient is not depend on density only, the geometry has a crucial part. please mention the geometry type.also you need to mention whether it is an internal or external flow, parallel or cross flow, ....

 

[speco]

dbecker,

If the other properties did not change, the heat transfer should stay the same. The only realy change would be the velocity of the fluid in question, and therefor the pressure drop. The Reynolds number is the same and the Prandtl number is the same. Right?

Speco