A cap tube design program for RE members by RE members.

[Chef]

It seems USIceman has nailed this thing down with whats going on inside the tube and its great we are both looking at the same phenomena - gives one more confidence to proceed.

Both of you, USIceman and Peter_1, are professional refrigeration engineers. For me its just a hobby and an intermittent one at that, when the real job kicks in it takes up weeks or months of non stop effort so with some time at hand at the moment its nice to get back to some fundamental research.

I see Refprop is $200 and this may be excessive until we can prove it works. They also want $2,000 up front for distribution! I have Fluidprop but this has a library for refrigerants by Refprop so the license is also needed. No way out there, shame as its nice to use in Excel.

Having to enter the data just detracts from the fundamental part - the actual code - the solution.

Peter_1 - I am still working on the Stoecker stuff and will let you know what it's status is soon.

Chef

[Chef]

Peter
I can retrieve and print all except P269 and 271. Could I be so obtuse and ask for those pages again - Sorry about that.

They have a nice momentum analysis part which could be interesting and want to see how it pans out

Thanks

Chef

[US Iceman]

I forgot about the distribution fees for RefProp. They have apparently chnaged them frmo when I last looked. There is another avenue though. The professional version of EES can create license free slef contained executable programs. It is just like compiling a program from Visual C++. You develop the Input screen you want, write the code/equations, and then compile it into an executable file.

You can place limits on the time use, etc. Something to thing about.

Or, you could just download the trial standard version, which is fully functional except you cannot save a file I think. Maybe it's print a file. I don't remember now.

It will be interesting to see how this develops and the comparison to other sources.

I was think about the iteration part. If you iterate the calcs' on pressure loss per inch of captube and know the initial and final pressures, the final result would be the required inches of captube needed for that operating condition. The captube bore would be one of the inputs, besides the refrigerant conditions.

[Chef]

I downloaded the demo of EES and it is brilliant, just hack the equations in - in any order - and solve presto. Well impressed and would be a useful way to go BUT.....

It does not allow copy, print, save, paste or edit so the code has to entered each time. whew and only 50 equations - not nearly enough.

The idea of EES is good though as Peter gave me a method that uses Fanno line (adiabatic) calculations directly and EES would be able to resolve these equations. It seems a better method than I have been working with. I was using an isenthalpic style and then iterating to an adiabatic solution but it takes 2 or 3 iterations and is messy and sometimes it does not converge.

The Stoecker method solves the change in enthalpy and velocity head as the quality changes in one iteration so that has big advantages. First it will be easier to write and second it will be possible to change the parameters calculated.

The first thing is to calculate L the cap length.

But now we have a way to calculate the pressure for a known L or the flowrate for a known L and a set of pressures. Now would'nt that help with diagnosis work and give a way to see what happens with pressure and subcooling as we change the load.

I had thought about using Octave - an open source language but it is not as good as EES. I will do some more work on this.

Chef