Crane paper, exchanger 5

[Lblopez]

Hi, Where can I find the Crane Technical paper Nº 410?
Thanks

 

[MintJulep]

See that google seach box near the top of this page?

Type "crane technical paper 410" in that box. Click the Web radio button and click on "search".

 

[Lblopez]

Yes, I know serach in google, but if I do it, I find many websites where the Crane paper is used by reference but I need to know what "say" the paper about K factor for exchanger calculation.

Thanks.

 

[MintJulep]

First hit from Google is

http://www.cranevalve.com/tech.htm

which provides you the opportunity to buy a copy of the paper.

 

[IRstuff]

Apparently, your issue is that you don't want to pay for it?

The second hit I got was the reference to the order form page for the paper:

http://store.vervante.com/c/v/category.html?base_cat=Crane Valve:Technical Paper 410&pard=crane

TTFN

 

[Lblopez]

You're rigth IRstuff (TTFN). I don't want to pay for.

Thanks.

 

[IRstuff]

Well, you've probably burned a couple of hours of engineering time already. At $20/hr, your investment is already more than the cost of the paper.

TTFN

 

[monkeydog]

I don't think it is in there. I just looked in my copy, and did not see any chapter on "K factor for exchanger calculation".

 

[StoneCold]

I second Monkeydogs comment. It will not help you design an exchanger. Look in Kern.


Regards
StoneCold

 

[vpl]

Lblopez

Are you really trying to ask "When I'm calculating the pressure drop in a line, what K-value do I use for a heat exchanger?"

If so, the answer is "This is not found in Crane Technical Paper 410, which looks at flow through valves, fittings, and pipe. You would obtain the pressure drop across the heat exchanger from the manuafacturer's data sheet or by doing a separate calculation for pressure drop."

By the way, I recommend spending the money for the Crane manual. It comes in either English or metric units, is reasonably cheap, and is well worth it! Some companies will even pick up the tab for it.

Patricia Lougheed

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

 

[sshep]

Lblopez,

FYI, there are some useful heat exchanger affinity laws in the GPSA Engineering Data Book under the heat exchanger tab. If you have a spec sheet (or field data) for one set of flow conditions (mass flow, density, viscosity, thermal conductivity, etc), the heat transfer performance and pressure drop can be estimated for other conditions. Relations are given for both the shell and tube side. Some geometry changes (baffle spacing, tube diameter, etc) are accomidated as well. There is even a worked out example. Obviously some judgement on applicability is required (for example if new conditions involve a phase change), but these are still very useful quick calculations.

About all Crane 410 will be useful for relative to exchanger work is as a reference for basic formulas- i.e. once the pressure drop is known at a given flow rate and density, Crane will show you how K can be calculated from your data. Of course due to the nature of heat exchangers, K may not neccessarily be a constant for other operating conditions.

best wishes and good luck,
sshep

 

[TD2K]

Patricia, good to see you back!!!

 

[IRstuff]

Welcome back, Patricia!

TTFN

 

[Lblopez]

Ok, I didn't explain good

I'm doing a cooling water system evaluation, becouse there have some troubles. We doing a Visual flow simulation, in the exchanger window, the pakage need a K value wich is assosiated with pressure drop. I dont know how I can calculate this K for make a better simulation. This K factor produce a change in the pressure drop by each change in the flow.
I can do a simulation without use this K but this would be erroneous, becouse I think, that some troubles that have the plant in study, is that the pipeline have a big pressure drop and the water in not come in to the exchanger in High vacuum distillation and Delayed Coker unit.

The Visual Flow's manual say that this K factor equation is reported in the Crane Technical paper 410.

Thanks everybody.

P.D.: Here US$ 35 is a considerable amount of money and I can't buy it.

 

[vpl]

Lblopez

I understand your difficulty. However, having in hand my Crane manual, I still don't have enough information to provide you an answer. There are different formulae and values of K, dependent upon the component. For example, a full bore gate valve has a K of 8f_T where f_T is the friction factor. However a tapered bore gate valve has an entirely different K, depending on the amount of the taper.

The pressure drop across a heat exchangers (which is how I am interpreting "exchanger" in your posts) is not discussed in Crane. It has values for straight lengths of pipe, both gradual and sudden changes in pipes, and for various types of fittings and valves.

If you are wanting the K value for piping leading up to a heat exchanger (and not across the heat exchanger itself) then you need to get the K value for each length of pipe, each change in pipe diameter, each elbow, tee, valve, etc. This is a considerable amount of work.

I realize that US$ 35 might be a lot of money; however, I question what was spent on the Visual Flow software and how important the results are. If you are wanting more accuracy than just ignoring the K factor completely, then you need to have some basis for the values used. At least try and convince your management that this information is necessary to run the program.

Patricia Lougheed

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

 

[Latexman]

Lblopez,

Hey, you, with the "asno barato" company!

If you would describe this heat exchanger in detail, and describe the fluid and flow through the side of the heat exchanger you want pressure drop estimates for, we MIGHT be able to help you!

What kind of heat exchanger is it?
Shell and tube? Plate and frame? Other?
Are you interested in the pressure drop in tube side or the shell side?
Is it 1 pass, 2 pass, 4 pass?
Describe the baffles? 20% cut? 25% cut?
Baffle pitch?
How many tubes per pass?
What size O.D. tubes? Wall thickness? I.D.?
Tube length?
What's the fluid? Water?
What's the flow rate?
Inlet T?
Outlet T?
Etc., etc., etc.?



Good luck,
Latexman

 

[MortenA]

I think I speak for most people here when i say that this site does not endorse distrubtion of illegal copies of software or books e.g.

However i think that many publishing companies have special prices for 3. world countries and sometime the opertunity to buy issues printed with slightly lower quality at significantly reduced prices. This will however require that you investigate this locally.

Best regards

Morten

 

[monkeydog]

MortenA,
Interesting ethics question. If the Lblopez were to ask for someone to post or e-mail a page of the Crane paper, that would be illegal (easy ethic answer). But if he asks for the K factor for a particular fitting, I don't think that is illegal or unethical.
It is not clear what Lblopez needs yet.
If your collegue across town called on the phone, and asked for the K factor, wouldn't you give it to him? Or would you tell him to go buy his own paper?

 

[vzeos]

Lblopez

K = f_t*L/D, where f_t is the fully turbulent flow friction factor, L is the equivalent length of pipe and D is the pipe diameter (in L units.) If you can approximate the equivalent length and the friction factor and if you know the pipe diameter, you can approximate the K value.

It seems you are looking for an overall K value for the heat exchanger. Perhaps the Wolverine Engineering Data Book II might help, it gives a compressive look at heat exchanger calculations, including pressure drop calculations.

http://www.wlv.com/products/databook/databook.pdf

MortenA,

You raise a good point regarding the distribution of illegal copies of software or books, but I think copyright law (in the US) allows for information shearing within reason:

A very important exception to the rule of copyright infringement is the concept known as fair use. Under this principle, the law permits the use of portions of copyrighted works for such purposes as criticism, comment, teaching, and research, even without permission of the copyright owner. In deciding whether a use is a fair use, courts consider such factors as the purpose of the use, the nature of the work, the amount of the work taken, and the effect it will have on the value of the original work. Some examples of fair use include quoting excerpts from a book in a review, scholarly article, or term paper; copying and distributing a newspaper article to illustrate an educational lesson; and using portions of a work in a parody of that work, such as a spoof version of a song. The Supreme Court of the United States has held that it is also fair use to use a home videocassette recorder to make copies of television programs and movies for later viewing.

http://encarta.msn.com/encyclopedia_761570404_2/Copyright.html#S17

 

[EGT01]

Here's an approach I've used before that basically summarizes the suggestions from a number of the previous posts.

For a single phase, incompressible fluid, the head loss through a fitting is directly proportional to the flow squared assuming the friction factor does not change appreciably...
dP = f(Q^2)

From Crane's TP410 or any other of your favorite fluid flow references

dP = 0.00001799 * K * rho * Q^2 / d^4
dP = head loss, psi
K = resistance coefficient
rho = density, lb/ft3
Q = flow, gpm
d = inside diameter, inches

Rearranging...

K = dP * d^4 / (0.00001799 * rho * Q^2)

Now you still need to have some data to start with such as the manufacturers's calculation results indicating the pressure drop for the designed flow rate or you will have to perform those calculations yourself unless you can actually measure the pressure drop and flow in the plant.

The only part that remains is the diameter but I would just pick that equal to the piping run where the exchanger is located which allows you to sum the resistance coefficient of the exchanger directly with the piping. Otherwise, the resistance coefficient for a given component in terms of other diameters is related by...
Ka = Kb * (da/db)^4