boundary layer degradation
boundary layer degradation
(OP)
Hello.
I have a liquid flowing through a pipe, which produces laminar flowrate properties. The boundary layer produced by this is considered to be a thin film. The pipe is exposed to high temperatures which degrade the flowing liquid.
If the flowrate is reduced, does the boundary layer increase in size?
will the fuel degrade more rapidly with a larger boundary layer?
Does heat alter the boundary layer of a flowing liquid ?
I have a liquid flowing through a pipe, which produces laminar flowrate properties. The boundary layer produced by this is considered to be a thin film. The pipe is exposed to high temperatures which degrade the flowing liquid.
If the flowrate is reduced, does the boundary layer increase in size?
will the fuel degrade more rapidly with a larger boundary layer?
Does heat alter the boundary layer of a flowing liquid ?





RE: boundary layer degradation
What do you mean boundary layer?
If I am understood correctly the meaning the boundary layer you mentioned,as per theory any fluid flowing over a solid object will develop a boundary layer, which is an imaginary region from the solid surface extends a certain depth into the flow. Within the boundary layer viscos effect are very significant and velocity gradient is more.
Now let us come to your question, for pipe flow the boundary layer thickness will goes on increasing along the flow direction and after a certain length from the entrance of the pipe the boundary layer will reach a condition called fully developed flow. In that situation the boundary layer thickness is equal to the radius of the pipe.
For laminar flow the following equation can be used for calculate the entrance region (before the fully developed condition)
x/D = 0.05 Re
where, x-is the entrance length
D-pipe inner diameter
Re-Reynolds number based on the pipe inner dia
Regards,
KMPillai
RE: boundary layer degradation
m777182
RE: boundary layer degradation
Thanks for the help!
Much appreciated!
RE: boundary layer degradation
Eventually the fuel oil will "crack", or the oil in the film will deteriorate as the light factions pass out of the film and the residual carbon will remain in the film and coke up the piping.
I am not sure of teh overall configuration of your process, but if you need to heat the fule oil you may wish to use a temperature limited heating medium ( such as condensing steam or dowtherm) to avoid such deterioration. If the heat flux is the define boundary condition ( eg radiant heat transfer from hot gases) then you will likely need to improve the inside heat transfer by using internal ribs or fins or reduce the outside flux by coating the outside of teh tube with ceramic .