dear Gonski,

I had a look at the article (I did not check it word by word).

It is about a plug in a pipe line, which is forced through that pipe line by a pressure difference over that plug.

The sum of pressure differences over n plugs is the line pressure.

The plug is considered stable.

Moving the plug through the pipeline is mechanical. (Equilibrium of forces).

Internally in the plug, soil mechanics play a role.

The stress transmission coefficient is important in creating the pipe wall pressure, which results in the wall friction force, which in its turn has to be overcome by the pressure difference over the plug.

The stress transmission coefficient (main stress/lateral stress) is related to the internal friction coefficient (or internal friction angle)

In the appendix of the article it is easy to recognize the definitions of the various friction angles and their meaning.

In table 1 the last column should be the static internal friction (phi-s), which normally equals the angle of repose.

In equation 14), a regression formula is given from the values presented in table 1

The Mohr circle is also important in flow characteristics of material when stores in a stockyard and in silos. (mass flow, funnel flow, arching)

don’t give up

teus ■

You're just starting at PhD level & you're already puzzled by the vagaries of pneumatic conveying. That is to be expected.

Hint? Get out of the frame while you're still young enough!

Numerical simulation translates into English as the numbers game. Interparticle behaviour is one of those topics that makes pneumatic conveying such a suck it & see operation. Basic thermodynamics apart, of course. ■

Pneumatic conveying simulations are over 30 years old now. Earliest published work dates back to late seventies people like Prof Tusji did a lot of work in this field. There are still a number of research groups working on it. Do your literature survey first it will help a lot.

Are you simulating dense or lean phase flow? If it is lean phase then you are holding the wrong end of the stick you should not be looking at the particle-particle friction as the particles will not slide on each other in fully suspended flow, they will collide and move in different direction. You should be interested in Particle-particle collisions and it will be more dependent on particle shape and size. Your simulation should take this into account.

Internal friction is always calculate at certain compaction /normal load which is not present in fully suspended flow but then it is debatable!!!. If you really want to use internal friction then Tan inverse of internal friction angle will be the friction coefficient. ■

dear Gonski,

I understand that you already have a working numerical simulation of pneumatic conveying.

Then it is easy to iterate the particle-particle-wall-friction-collision coefficient back from field data of existing installations.

Then you can differentiate the factor to SLR and Reynolds number (turbulence).

The value of this coefficient is depending on the used formulas and units. (factor value is different in SI-units than in English units)

Furthermore it is a misconception that the internal friction of a product is related to a pneumatic conveying loss factor.

Internal friction is about forces

Pneumatic conveying product loss factor is about energy

If you browse the pneumatic conveying section of this forum, you will find a lot of usefull starting information.

(The purpose of this forum)

Mr Mantoo: Indeed, I started building my numerical simulation program in 1982.

25 years ago (almost 30 years)

Success

Teus ■

Dear Teus Tuinenburg

hi sir hou r u

well here is my quistion , if i remember few days back of your thread regarding temperature gradient of mixture( air+ash) after particular distance you have enlighten some mathmatical formula to know the temp of mixture after particular diastance

Would you provide the complete version of formula to calculate the temp reduction of mixture

Reason why iam emphasizing to know because i was informed from one of my clent that temp of ash is 250Deg in ESP ECO AND APH and is identical at all these three points which may practicaaly not be possible

waiting for your valuable reply

rahul ■

dear Rahul,

You are referring to another thread. (fly ash temp)

see that thread

teus ■

In dense phase flow there are three options discrete plug flow dune flow and mixture of both. All conditions have to be simulated differently.

For discrete plug flow the material will form plugs and the length of the plug will be very important as every material has a natural plug length. The force driving the plug will be the conveying pressure minus the porosity or air flow through the plug. While the plug is sliding on the pipe; wall friction coefficient will be major contributor to the pressure loss. There will be very little movement in the particles within the plug so particle-particle friction is not very important. The lower coefficient used in the publication is more likly to be close to wall friction or it could come from experimental work.

I as far as I can remember few years back a PhD student at Glasgow Caledonia University was working on a very similar project, try contacting them it might be very useful.

I fully agree wit Mr Teus comments on misconception on PC friction factor. ■

Internal friction and internal angle of friction are connected through the normal force

Internal friction force = tan(internal angle of friction) * Normal force.

That is all

have a nice day ■

As a 'fly on the wall' I remember back in 1988 when I worked on the same site (different project) that was having a toilet disinfectant block making plant installed. Ingredients were manhandled from cardboard drums into shrouded hoppers & pneumaticaly conveyed to the mixers & thence to the extruders. Everything was well sealed because of the toxins used. Laboratory tests later revealed that the most lethal ingredient was sadly lacking in the final product. This discrepancy was eventually traced to localised heating of the crystals during the conveying operations: causing that particular toxin to vapourise & thus escape beyond the confines of the filter baghouse.

Before the days of CFD it was assumed that the vagrant toxin had settled over the adjacent residential area. I later heard that the entire plant had been very quickly shut down & relocated to Hull.

Friction or collision heating apart: could such behaviour be predicted nowadays? ■

Apparently anything can be predicted these days on you will have to put in an equation / constants which govern these changes. This is the area where I find the grey area of simulations; one does still need to do actual tests to either find the constants or to validate the results. ■

Dear Friend,

As I can see in the many responses you have had it gets very confusing, right? An many of the answers are not addressed in your question.

You did mention that you are simulating dense fase low velocity pneumatic conveying.

It is a very interesting topic that has been addressed in the past by Pittsburgh University under the direction of Prof. George Klinzing. I believe he can be of help to your endeavour.

If you are interested in contacting him, I will be glad to give you his e-mail.

Send me an e-mail and I will forward it to him.

Regards,

Marco A. Flores ■

Originally Posted by Marco A. Flores

Dear Friend,

As I can see in the many responses you have had it gets very confusing, right? An many of the answers are not addressed in your question.

You did mention that you are simulating dense fase low velocity pneumatic conveying.

It is a very interesting topic that has been addressed in the past by Pittsburgh University under the direction of Prof. George Klinzing. I believe he can be of help to your endeavour.

If you are interested in contacting him, I will be glad to give you his e-mail.

Send me an e-mail and I will forward it to him.

Regards,

Marco A. Flores

Dear TECMAN

May i have your email ID fpr ertain clarificatio in context of s\plug flow low velocity dense phase conveying system ■