Ok, so the conclusion is - as I had expected - that we do need to add corrosion inhibitor to these systems.
My next question is: what type of chemicals would be required? Would we for example need both corrosion inhibitor and oxygen scavenger, or is it enough with only one of them?
The...
The pressure downstream the pumps (and hence in the WHRUs) is determined by the expansion tank operating pressure, plus the differential head of the pumps. We could take this pump differential pressure into account when setting the expansion tank operating pressure, but the advantage of keeping...
Stainless steel is out of the question due to cost, as our client is very specific when it comes to one requirement: lowest possible CAPEX. Of course we could exclude chemical dosing to reduce CAPEX even further, but we need to engineer a system that will actually work for the intended life time...
Thank you for the replies!
Including for corrosion prevention chemicals is what I consider good engineering practice, and a very cheap "insurance" with low CAPEX impact compared to the overall cost of the plant. Since the required dosing concentrations of these chemicals are low, OPEX would be...
Hi all,
I am currently working on a FEED phase study for a large, offshore gas production plant. The current design includes three closed loop cooling and heating medium systems, briefly described below:
- Main cooling medium system, normal operating temperatures 34 to 55 °C
- Turbine inlet...
vzeos:
OK, now I see what you mean. With the circular reference method one could for example use Hagen-Pousille equation when Re is below 2000, instead of just resulting in a friction factor equal to 10 000 like my formula in a previous post.
quark:
That is a good point. It's a bit strange...
By the way, don't be concerned if this equation is unstable at Nre=0 because the Colebrook equation is not valid for flows in which the Nre < about 2000.
No, but when you use a spreadsheet there is a good chance that you will sometimes erase the input values. If this happens, the blank cell is...
eln10:
You're right, the formula I supplied in the second post is of course incorrect since cell A3 is equal to f and not 1/sqrt(f).
Thanks for pointing that out, I should have checked the results better before posting (the result is often not too far off, which is why I missed it).
prex...
Katmar,
You're right, but I just wanted to point out that no significant accuracy will be lost when using the formula for Cv in terms of SI units instead of the original US units.
OK, here is the formula:
K = D^4/(466.134*Cv^2)
where D is the inner diameter of the pipe in mm.
I don't remember the unit of the constant, so if you need them you should try and derive the formula yourself. It's not very difficult and it gives you a better understanding of how it works.
As...
I don't remember the units in the Crane formula, but I have derived the same type of equation myself using SI units and the Fisher Control Valve Handbook formula for Cv.
Basically it can be done by replacing delta-P in the formula for Cv with K*rho*V^2/2. The velocity V is of course a function...
This is the way I am used to interpret these values:
Clean coefficient: The calculated heat transfer coefficient without fouling resistances.
Dirty coefficient: Heat transfer coefficient including fouling resistances.
Service coefficient: Dirty coefficient divided by a safety factor. This...
Don't forget to set the "Maximum change" value (also under the "calculation" tab relatively low. Otherwise the accuracy will be too low to motivate the use of implicit equations. I use 1e-6 for the Colebrook-White equation.
Apparently Excel will repeat the iteration every time any cell value in...
Turns out it is actually possible to solve these equations directly by letting the equation refer to it's own cell. Guess I should have tried that first...
Colebrook-White equation can the be written as:
Enter the Reynolds number into cell A1
Enter the relative roughness e/D into cell A2
In...
Hi everyone
Just wanted to share a little tip for direct solving of implicit equations (like the Colebrook-White equation) in Excel without having to use Solver, goalseek, VB or macros.
Implicit equations will of course still have to be iterated in order to be solved, but this can easily be...
