Are there any ways to induce small amount of shear stress on the heat exchanger walls ?
It can be done by increasing the velocity of the fluid and by increasing the surface roughness of the wall. May I know if any other chemical/mechanical techniques available for this process ?
By mechanical means for inducing shear on the wall surface, u can move the wall with with a finite velocity in the direction opposite to the flow. This will increase the relative velocity between 2 points and increases the shear stress.
R u asking for simulation?
If you use FLUENT (or even CFX-code) there is an option in wall boundary for setting a value for shear stress.
Using pulsatile (for exemple sinusoidal) flowrate could help in increasing wall shear stress.
I am not asking in terms of CFD, i need some practical ways (experimental) to induce shear.
@Vigneshwaran, thanks for your answer. may i know if u can suggest any thing other than increasing the velocity of the fluid and by increasing the surface roughness of the wall ?
@Dr Vincent, thanks for your answer. Will read on that and please let me know if any other techniques are available as well.
shear on the wall is directly related to pressure drop and is one of the required measurement s in any such systems (or modelling).
What kind of heat exchanger are you talking about? Is it a shell and tube heat exchanger or what? Remember a heat exchanger is a pressure vessel and could be stressed by performing a static pressure test which is the standard way of testing heat exchangers. Static pressures tests are usually performed per the provisions of the ASME Boiler and Pressure vessel code. Section VIII is for the design and testing of unfired pressure vessels. Fill the heat exchanger with water and pressurize it to a pressure of at least 1.5 times the operating pressure and wait for about 1hour. Read the pressure gages and record the readings. Estimate your stresses, hoop stress, radial stress and longitudinal stress using the thin cylinder theory in the case of the shell. Use the thick cylinder theory to determine the stresses on the tube since it is subjected to both external and internal pressure. To estimate the shear stress use the morh circle.
- Badges
- Science topic
- Similar topics
- Engineering
- Mechanical Engineering