Heat transfer analysis of heat exchanger with complicated shape and irregular fins

Mahesh Patil · September 28, 2016, 07:28

Hi all,

I am working on a project in which I have to discuss the heat transfer characteristics of complicated heat exchanger which has varying diameter with irregular fins outside and inside. (I have three fluids and one solid heat exchanger). I tried earlier discussions and other books/documentation. But it seems very confusing.

I have couple of doubts.
1) how to calculate the Reynolds number for this case?

I know,
Velocity scale = areaAve(Velocity)@inlet
Length scale = the diameter of the cylinder or chord length
density scale = areaAve(Density)@inlet
Viscosity scale = areaAve(Viscosity)@inlet

But, how to calculate characteristic length in this case.

2) How to calculate Nusselt number, heat transfer coefficient and heat transfer rate with varying Reynolds number? (This seems complicated due to complexity of geometry)

Thanks,
Mahesh

evcelica · September 29, 2016, 12:07

See the FAQ for some general info on HTC and Nusselt calcs if you have not already:
http://www.cfd-online.com/Wiki/Ansys...ficient_in_CFX

You can pic any length scale you want, it is somewhat arbitrary for complex geometry. Diameter of tubes is appropriate for internal flows.

September 28, 2016, 07:28	Heat transfer analysis of heat exchanger with complicated shape and irregular fins	#1
Mahesh Patil New Member Join Date: Sep 2015 Location: South Korea Posts: 4 Rep Power: 10	Hi all, I am working on a project in which I have to discuss the heat transfer characteristics of complicated heat exchanger which has varying diameter with irregular fins outside and inside. (I have three fluids and one solid heat exchanger). I tried earlier discussions and other books/documentation. But it seems very confusing. I have couple of doubts. 1) how to calculate the Reynolds number for this case? I know, Velocity scale = areaAve(Velocity)@inlet Length scale = the diameter of the cylinder or chord length density scale = areaAve(Density)@inlet Viscosity scale = areaAve(Viscosity)@inlet But, how to calculate characteristic length in this case. 2) How to calculate Nusselt number, heat transfer coefficient and heat transfer rate with varying Reynolds number? (This seems complicated due to complexity of geometry) Thanks, Mahesh Last edited by Mahesh Patil; September 28, 2016 at 07:30. Reason: missed one important factor

September 29, 2016, 12:07		#2
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,167 Rep Power: 23	See the FAQ for some general info on HTC and Nusselt calcs if you have not already: http://www.cfd-online.com/Wiki/Ansys...ficient_in_CFX You can pic any length scale you want, it is somewhat arbitrary for complex geometry. Diameter of tubes is appropriate for internal flows.