RhoV2 criteria for Line Sizing
RhoV2 criteria for Line Sizing
(OP)
Dear members,
Has anyone heard of or use the criteria RhoV2 (fluid density multiplied by fluid velocity squared- has SI unit of kg/m2s ) for line sizing of gas or two/multiphase lines. I understand the criteria is to limit vibration in pipes. Does anyone know any internationally recognised code or standards that address this criteria?
cheers
Has anyone heard of or use the criteria RhoV2 (fluid density multiplied by fluid velocity squared- has SI unit of kg/m2s ) for line sizing of gas or two/multiphase lines. I understand the criteria is to limit vibration in pipes. Does anyone know any internationally recognised code or standards that address this criteria?
cheers





RE: RhoV2 criteria for Line Sizing
The general approach for pipelines I was aware of was that the optimum economic diameter is the one at which the sum of operating costs, interest and depreciation is a minimum.
ΔPf ≈ L/50 Dh ρV2/2 for gases with Re in the range 100,000 to 500,000.
BTW, your units aren't OK, they should be: kg/ms2, which means units of force per unit area, Pa or N/m2.
RE: RhoV2 criteria for Line Sizing
As far as standards go, I know that HEI uses mass flux sizing criteria for nozzles operating at saturation conditions.
I2I
RE: RhoV2 criteria for Line Sizing
Also, this is an established practice for control valve selection and could be used for line sizing as well.
I2I
RE: RhoV2 criteria for Line Sizing
I2I
RE: RhoV2 criteria for Line Sizing
For incompressible liquids you could use 0.5 rho V^2, sometimes called "velocity head", but again that relates to overall pressure loss of the pipig system, if you know the total (fL/d ) and allowable pressure drop. Velocity limits are checked to ensure erosion is not an issue; 20 fps max for water in carbon steel pipe. Since liquid piping DP is a trade off with pump sizing and pump power, there is often an economic analysis done to see if there is an optimum pipe size/ pump size for minimum present value of pump power + investment cost. Traditional "economic pipe size" for water was 10 fps, based on this economic critieria but using 1950 cost for electric power.
2 phase flow has other issues, such as flow regime, erosion-corrosion, flow stability , etc.
RE: RhoV2 criteria for Line Sizing
And rho v^2 has no consideration for length of line, which usually becomes one of the most important variables ...eventually.
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: RhoV2 criteria for Line Sizing
In the May 2008 issue of Hydrocarbon Processing is an article titled The effect of kinetic energy change on flow in gas pipelines by F.A. Demneh that can find your interest.
RE: RhoV2 criteria for Line Sizing
A typical maximum velocity (ft/s) = 100 to 150 / sqrt(density lb/ft3)
I consider this the maximum velocity for which a new pipe (in non-corrosive service) should be designed.
RE: RhoV2 criteria for Line Sizing
http://virtualpipeline.spaces.msn.com
"What gets us into trouble is not what we don't know, its what we know for sure" - Mark Twain
RE: RhoV2 criteria for Line Sizing
RE: RhoV2 criteria for Line Sizing
If you play around with it, it works out to the same as the API 14E erosional velocity limit with a fairly high C coefficient. Let me know if you want me to dig into my files and find out what C I backcalculated it was equal to.
RE: RhoV2 criteria for Line Sizing
http://www.mms.gov/tarprojects/131.htm
Be sure to check out the other interesting resources at the MMS website which is mostly related to offshore oil and gas industry.