2 replies to this topic

[firefox23]

Hi, I am currently working on a project where I have to design a tube and shell heat exchanger. I have just reached the stage where I need to calculate nozzle pressure drops, however I am unsure how to do this. I am using chemical Engineering design chapter 12 by Sinnott and Towler, and there is a short section about how these can be calculated. For the tube side I need to use velocity heads based on inlet and outlet velocities but am unsure how to calculate these, are they just the velocities inside the tubes? For the shell side I need to use velocity heads based on nozzle area or free area between the tubes in the row immediately adjacent to the nozzle. I am also unsure how I calculate these areas and the corresponding velocity heads. Any help would be much appreciated.

[MTumack]

I am not familiar with your book or the methods they use, but I assume you are looking for a measure of the energy in the fluid from its velocity based in ft or meters? This is what you would require if you were using something such as Darcy's work on energy loss from a fluid.

 

KE = 1/2 M v²  =  W v² / 2 g

 

 

Where:

KE = Kinetic Energy (kgM²/s²)

m = Mass (kg)

W = Weight (Newtons, or KgM/s²)

v = Velocity (m/s)

g = gravitational constant (9.81 m/s²)

 

Thus we can say our velocity head in Meters is:

 

KE/W = v² / 2 g

 

Should be noted that this would only be valid for Liquid flow as gas flow will not have a constant weight / velocity.

 

That being said, I would have thought by the time they had you designing such equipment you'd have a good idea of the fundamentals of fluid mechanics and heat transfer? You should be able to derive this from scratch based on memory, in my opinion.

Edited by MTumack, 05 April 2017 - 01:08 PM.

[srfish]

TEMA has some requirements for maximum shell inlet velocity. On my website of  www,gulleyassociates.com , click on "Engineering tips. Then look in the calculation section. There are equations to calculate the minimum flow area for this TEMA maximum velocity.