[CellZone]

Hi,

I a have read a sentence which says about two nearly the same simulations:

If the fluid flow around a body is nearly the same in simulation a) and in simulation b) , one can say, that the heat transfer coefficient is nearly equal.

According to my understanding, the heat transfer coefficient also depens on the surrounding temperature of the body. If also the temperatures in a) and b) are nearly the same, this statement is correct. But without this information, you can not clearly say.


Yes it is true that the transfered heat depens on the velocity and turbulence intensity of the flow , but also on the temperature which surrounds the body in case a) and case b)


Am I right?

Thank you for your comments CFD Online :-)

CellZone

[LuckyTran]

The heat transfer coefficient is a flow property. So to say that if the flow is nearly the same, the heat transfer coefficient is also nearly the same is the idea behind the heat transfer coefficient.

Originally Posted by CellZone

Yes it is true that the transfered heat depens on the velocity and turbulence intensity of the flow , but also on the temperature which surrounds the body in case a) and case b)

You are confusing heat transfer rate with heat transfer coefficient (the proportionality constant). The point of the heat transfer coefficient is to separate the driving temperature and that's the implicit meaning behind Newton's law of cooling. Otherwise, we could just say heat flows from high to low temperature and never mention anything about a heat transfer coefficient.


As an example we know temperature difference drives heat. That is, a body at 310 K in surroundings at 300 K would lose heat at nearly the same rate as a body of 305 K in surroundings at 295 K. Yes there is some differences due to the value of temperature, but these are non-linear effects. I guess you are picking at the point that the statement is only 99% correct and not 100% correct (but it clearly says nearly equal). Well that is quite pedantic because the heat transfer coefficient also depends upon religion you subscribe to. Be pragmatic!

[FMDenaro]

Not sure if I understand correctly this issue...
if the flow problem is solved under the incompressible assumption, the heat equations is decoupled from the velocity field. Therefore, the same velocity field is introduced in both cases. The difference can be if different boundary conditions are introduced over the body or different inlet temperature is prescribed.


In case of compressible flows all the field variables are coupled and I think that if the flow properties are the same that implies also similarity in the temperature field.