7 replies to this topic

[karthick selvaraj]

Hi,
Can any one please let me know the difference between the cross flow velocity and window velocity in the heat exchangers.
And in the Heat Exchanger specification sheet or TEMA sheet generated by HTRI, the shell side velocity value shown is different from cross flow velocity and window velocity.
My point is for calculating heat transfer co-effecient(shell side) and pressure drop which velocity has to be considered.
Whether it is shell side velocity or cross flow velocity and window velocity ?

Please let me know on above.

Thanks
Karthick.S

[srfish]

Cross flow velocity is the velocity accross the bundle. Window velocity is the velocity through the baffle window. Any good process heat transfer book wik give you the equations for these two variables.

Which velocity needs to be considered depends on whose correlations are being used. Some correlations depend on only the cross flow velocity, Other correlations depend on both velocities. HTRI depends on both velocities.

[Shivshankar]

Karthick,

Hope this helps you.

Regards
Shivshankar

Attached Files

•  exchanger.pdf   241.91KB   2361 downloads
•  designshelltube.pdf   30.03KB   3603 downloads
•  shelltube.pdf   77.72KB   23026 downloads

Edited by Shivshankar, 17 July 2012 - 10:28 AM.

[Dipankarc84]

Hi Karthick,

Since you are already using HTRI, I would suggest that you please go through the help files. HTRI perhaps has the best help resources that any software can offer and everything is explained fundamentally in very simple and clear language.

If you search the HTRI software for "crossflow/ window flow" velocities, you will get all the answers to your questions.

The difference between crossflow and windowflow has already been explained in the previous posts. HTRI does not use either of the velocities in any of it's calculations for Xist module. If you check the HTRI helpfile, it is clearly mentioned that the cross flow and windowflow velocities are "nominal velocities that are reported for comparative purposes only".

Regards
Dipankar

[karthick selvaraj]

Thanks all for your reply

Thanks
Karthick.S

[sheikh]

Dear All, can anyone tell me what is the difference between crossflow & shell side velocity in HTRI. Also, can anyone tell me the velocity distribution in shell along the length of shell & tube exchanger.

 

 

Sheikh Mohammad

[shashank123]

Hi,

I also can't get clearly but if anyone can help to understand the definitions below:

 

 

file:///D:/HTRI6/XchangerSuite6/Help/Subsystems/xist06/Content/ST/input_panels/geometry/Clearances%20panel/h_ist_diagram_of_bypass_and_leakage_streams.htm

 

1. Bundle Crossflow Velocity:  Based on B-stream flow fraction and integral average flow area in tube row perpendicular to general direction of crossflow. In most cases, Center velocity is the same as Shellside velocity on Final Results. However, values at inlet and outlet are based on layout seen as flow entering the exchanger. For example, for 30-degree layout and parallel baffle cut, flow looks like 60-degree bundle and velocity is calculated appropriately. Xist uses this value to calculate Average crossflow velocity ratio in Fluidelastic Instability Check area and Crossflow amplitude in Tube Vibration Check area of output.Xist uses this value to calculate vortex-shedding frequency ratio (line 20), turbulent-buffeting frequency ratio (line 22), and crossflow amplitude (line 26).

 

2. Bundle/Shell Velocity: Flow velocity of C-stream at each location in exchanger based on physical properties. Printed for information only, it is not used in any calculations.This stream can cause flow-induced vibration in tubes near the shell if velocity is high. Printed for information only.

[srfish]

It appears that you have access to HTRI. Their manual and help file should define the terms you are interested in. Theiy have information about the vibration terms in a special section of the manual