S&T Heat Exchanger - Rho x V2 - tubeside?

[MECHINGDK]

Hi,
is there anybody that have more detailed information to the weight of importance to the Rho x V2 (mass flow) value, when we are talking gas flow at the tube side of a AFU or BFU type cooler.
TEMA says about 8650 (SI units) for liquids, but nothing for gas.
It could be that the impact is none, but some vendors are taking this into consideration anyway.

Any valid comments, will be appriciated.

 

[vpl]

Mechingdk

I admit to being a bit confused about what you are asking.

Rho x V2 doesn't equal mass flow (Note I am making the assumption that by "rho" you mean density ([ρ]) in units of kg/m³ and by V2 you mean velocity squared in units of m²/sec².) A simple unit comparison will show you that these don't equal flow rate ([ṁ]) in units of kg/sec.

Additionally you quote a value of 8650[SI units] but don't tell me what the 8650 is measuring or what units apply. I assumed from your previous sentence that it was flow rate, but the value makes no sense to me. A common value that I have seen is3m/sec for flow of water in tubes. This value is frequently considered a maximum to limit erosion in the tubes, and, obviously, would not apply to gases or other non-corrosive materials.

A bit more information would be helpful.

Oh, and this isn't homework is it?


Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[lizking]

Only applies if you have an axial inlet nozzle.

 

[gr2vessels]

MECHINDK,
The Rho x V2 is a momentum criterion of the fluid flow, measured in Pascals. It is calculated for nozzles entry or exit, also for entry or exit in the exchanger tubes, on shell side the flow between the tubes and other similar flow restrictive application, like gas / liquid separators, etc...It applies everywhere the flow could impact on the equipment or components. That's how you determine the need for impingement plates, tubes vibration or simply a wear plate in the front of the inlet nozzle of a separator...I also believe that this momentum criterion is used a bit loosely in the TEMA, without a proper preparation of the young designer / mechanical engineer.
More from the process engineers,
cheers,
gr2vessels

 

[MECHINGDK]

Hi,

First of all -
I got to admit, that it seems that I was a bit loose in my description first time around (I will keep that in mind to the next time I need your advice), but first..

Thanks a lot for your replies… It is nice to have a positive response to a very real problem.

Just to let you know - After I had put the question forward I had the unexpected fortune to meet one of the major players in shell & tube society (He is one of the co-writers to the TEMA standard) and I had the opportunity to ask him about my problem.

It turns out that - When you talk about GAS as a media at the TUBE SIDE, then is the Rho x V2 value not the important factor.
Focus shall instead be put into the issue about the velocity and corrosion in the pipes leading to the inlet nozzle at the cooler. If the pipes calculations are showing to be ok, then can both the inlet nozzle and the inlet to the internal tubing be regarded to be ok!
It is of course a bit more complicated than described above and you will need to take other considerations into the picture, but this is the major consideration that needs to be looked at in this case.
PLEASE note - It is NOT the case, when you are talking about LIQUIDS - then see TEMA for more information.

PLEASE regard this input as the closing input for this tread. Again - Thank for your replies.

Have a nice day