9 replies to this topic

[binzee]

HELLO!

I want to flow 200GPM of Kersosene through a line, i want to lay a line for this pupose.i dont have the pressure drop as well as the velocity.

How will i proceed.

thanx

[Adriaan]

Piping internal diameter depends on flow velocity and volume, the velocity depends on the medium.

Pipe wall thickness depends on the (maximum expected) pressure (plus a safety margin), the internal diameter and the pipe material used.

Pipe material depends on the medium to be transported, mainly.

Normally one would calculate the pipe size (internal diameter) needed and then find the closest larger standard pipe size available (of the required type / material). The pressure drop isn't an important factor as the maximum absolute pressure forms the basis for the descision.

[Art Montemayor]

binzee:

First and foremost, buy or obtain a copy of Crane Technical Paper No. 410. This is world-wide accepted as the “book” on practical fluid mechanics applications.

The way a professional process engineer calculates the diameter of a pipe or of a piping system in major process plant design or in hydrocarbon applications such as refineries, natural gas, and liquid fluids (such as Kerosene) is the following manner:

1. You select the relationship you are going to use. This can be the classical workhorse, the Darcy-Weisbach equation, or an empirical relationship such as the Hazan-Williams or the Panhandle equation for compressible fluids. The latter empirical equations are more traditional than accurate and are very inaccurate because of their generalities and assumptions. The Darcy relationship has proven to be the standard of the industry and you can’t go wrong with using it in the application of liquid fluids.

2. In the process industry a process engineer is not so concerned with average fluid velocities as he is with the pressure drops resulting from the required process flow rate. Velocity is a transient value – it hardly ever is a factor in achieving the basic, required values identified for a fluid at the end of its trajectory: the pressure and the temperature. These two values are usually what the process engineer is called upon to control – not the velocity of the fluid. If you look at a Process Flow Diagram you will discover the factors and values that a Process Engineer is called upon to produce: the pressure, temperature, flow rate, and composition. Fluid velocity is never even mentioned because it doesn’t matter. What really matters is the resultant pressure at the end of the pipe run.

3. Looking at the Darcy-Weisbach equation, we see:

Delta P = (density) (Friction Factor) (velocity)^2 / (144) (Pipe Diameter) (2) (g)
where,
Delta P = pressure drop, psi;
density = weight density of the fluid, lb/ft³
Friction Factor = the Darcy friction factor as described by the Colebrook-White equation;
velocity = the average (mean) fluid velocity in the pipe, ft/sec
Pipe Diameter = the inside pipe diameter, feet
g = acceleration of gravity, 32.2. ft/sec^2

The first thing to do is to assume a general, recommended velocity for the fluid and calculate the corresponding pipe diameter and Reynolds Number. Since you know the fluid properties you know the viscosity and knowing the absolute roughness of the pipe material and the Reynolds Number, you calculate the Friction Factor.

You then calculate the expected pressure drop and if that is OK, then you have the appropriate pipe diameter for the flow rate and expected pressure drop. Sometimes you are given the expected pressure drop and then you calculate the corresponding pipe diameter at an assumed and accepted velocity. There are various forms of the Darcy equation – all given in Crane’s Technical Paper #410.

4. Velocities only become an issue when such fluids as solids and slurries are involved. These are special applications because erosion and internal wear is a concern. Other special applications are where sensitive and hazardous fluids are involved – such as acetylene, which can decompose with catastrophic results. In general practice. The rules are to deliver the fluid in a specified pressure and temperature condition. The velocity at which it arrives is usually irrelevant as long as it is within accepted, recommended levels. You will find that this is the rule under which design manuals for world-class engineering firms (Bechtel, Fluor, etc.) are written.

If you don’t have knowledge of recommended fluid velocities, then you can refer to texts, the internet or simply inquire in this Forum. The information is general and varies between individuals and applications.

If you are a serious ChE student, then I strongly recommend you start building your own fluid flow spreadsheets for resolving these type of problems. If other students reading this thread show an interest, I may Post some of my personal Fluid Flow Workbooks for downloads that show how we resolve these type of problems out here in industry and what you have to learn and work with in order to attack fluid flow problems.

[binzee]

Respected Art!

Thanx a lot for enlightening me on this subject.I am very much interested in your fluid flow work books.

reagrds

[dylant]

Art:

Is there a way you can post your fluid workbook problem?
I'd love to have that. Thank you so much.

Regards,
Dylan

[Art Montemayor]

Dylan:

I don't have a "fluid workbook problem" at this moment.

I have various Fluid Flow Excel Workbooks that I have prepared for the quick, accurate, and convenient calculation of flow rates, velocities, and pressure drops within pipes and pipelines.

I don't think you'd "love" to have a problem. Is that what you really mean?

Art Montemayor

[dylant]

I thought the word "problem" is part of the book's title.
I would not expect a problem. I bet nobody would.

Could you upload the file? Thank you.

Dylan

[Art Montemayor]

No problema Dylan. I'll upload the Excel Workbook into this post on Monday morning.

I hope you study it carefully and note how the calculations are carried out. I've used these spreadsheet calculation forms for many years now - mostly in multi-million $ projects. And the equations have worked well, giving the correct and acceptable answers. I hope the workbook serves you well in saving you time but not in preventing you from studying it and showing how to organize your own in the future. Just because the calculations are done automatically doesn't mean that you don't have to study or understand the logic and the algorithm. That is a prerequisite. If you don't master the algorithm, you'll get the right answer but you won't know what to do with it or how.

My purpose is not to make you a lazy engineer. It's to make you a more efficient and knowledgeable engineer.

March 12, 2007:
Christmas arrived early this year - on my 70th Birthday. I just hope you and all the other ChE Students who download these workbooks realize the years of experience it represents and what you can do with it in the future if you study, re-study, challenge, and learn what it can teach you. Do not rely on these workbooks doing your work for you. Although it is still "Work in Progress", that is not its purpose. My fondest hope is that all ChE students will absorb these learnings and go on to create their own Engineering Tools improving always on this simple spreadsheet method with more knowledge and techniques. Enjoy, and give me any feedback that you and others think can improve on exchanging this valuable information for the benefit of all ChEs - students or recent grads.

March 14, 2007:
The Workbook is 1.5 Megabytes, so I had to divide it up into two (2) workbooks in order to post. Also, the site went down yesterday and these files were lost, so I'm re-posting:

 Art__s_Fluid_Flow_1.zip   101.29KB   654 downloads

 Art__s_Fluid_Flow_2.zip   440.75KB   526 downloads

[chimoanhvu]

Dear Mr. Art Montemayor
Happy birthday to you.
Thank you very much for your gold knowledge sharing. I have seen your files uploaded. Unfortunately, I couldn't download it.

Yesterday, I couldn't open this thread. Maybe, there was an error on the site. Please, send the files to my mail box
tvtdb@yahoo.co.uk
Your regards,
chimoanhvu.

[dylant]

Art:

Thanks for sharing although I got lost in your spreadsheet. It is way too advanced for me. Anyway, I will take this weekend to sit down and study your spreadsheet carefully.

By the way, happy birthday to you and I appreciate you "daddy"-ing me through this forum. Your knowledge and critics motivate me to become a better engineer each and every day.

Regards,
Dylan