Anyone looking for a small freelance multiphase CFD project?

ericbsb · June 28, 2016, 4:23pm

Hi guys, I’m not sure if this is the correct place for this posting. If not, please point me to where I should post instead.

There is a lot of interest in atmospheric water generation these days, and I have a specific in seeing the multi-phase CFD analysis for something simple like this: https://grabcad.com/library/sun-pumped-ground-cooled-condenser In particular, I would like to know whether such a system can even function in a purely passive fashion (as indicated in the design) or whether some major tweaks would need to be made for it to even function. In particular, I’m most concerned that the boundary layer friction in the coils would pretty much prevent it from working at all, hence I’d like to simulate it first

I’m happy to see that there is a fantastic cloud-based system like SimScale out in the market now, as it makes things much more accessible to non-experts! I have not done any form of CAD or CFD in many years, so I’m really looking for a mentor or expert who can help get me started by setting up a first-pass model and letting me tinker with it from there.

I don’t have a huge budget as this is a personal project at the moment, but I would be happy to pay someone for assistance. Is there perhaps someone in the community who might be willing to take this project on?

Thanks for your interest!

AnnaFless · June 28, 2016, 6:42pm

Hi @ericbsb,

Thanks for the post and welcome to the forum So you are looking to see whether this boundary layer friction can be overcome, interesting concept!

I’ll throw this one to the CFD guys to see if they have any thoughts/other referrals (@dheiny, @Ali_Arafat, @gholami, @pfernandez, @akosior, @oscarcorripio, @dylan, @TobiasHolzmann )

Best,
Anna

ericbsb · June 28, 2016, 8:39pm

Thanks @AnnaFless Also, I should mention to the CFD guys that I realize it may be a tall order to have the bottom tank venturi suctioned up to the top tank. If it makes the initial calculations easier (ie: system more feasible), I would be fine skipping that step and just letting the water pool in the bottom tank. I’m mostly concerned that even without the water pumping we might not be able to get over the boundary layer friction within the tubes.

Something just isn’t passing my smell test here and I’d like to figure it out before I go try to dig a hole in my backyard and test it, lol! Happy to entertain anyone else’s thoughts on the subject too!

jousefm · June 28, 2016, 9:15pm

Hi @ericbsb,

I am not an expert but did you consider the NPSH (net positive suction head) which includesthe parameter for friction losses. But since you mentioned venturi I am not sure if you are using a pump now. Interested in the discussion! Your project sounds pretty cool

ericbsb · June 28, 2016, 9:28pm

@jousefm Thank for your response and interest. Sorry for the confusion with the venturi comment. I was not referring to an actively driven pump, just merely the passive effect due to airflow. The original diagram had a small line going from the buffer tank up to the above ground tank, and my thinking is that just might be too much for the system to do passively, so I figured that I would leave that part out for now.

As for the NPSH, are you referring to the NPSH that would be available at the outlet of the upper hose once (or if) the system is in steady state?

jousefm · June 28, 2016, 9:44pm

Something like that yes. Just threw it in the discussion The first things that came into my mind were NPSH and Bernoulli Where NPSH often refers to cavitation effects. Did you do any calculations by Hand and see what Magnitude of Pressure you would need for Venturi ?

ericbsb · June 29, 2016, 3:58pm

@TobiasHolzmann Thank you for your very thoughtful comments! I think that you bring up some really good points. Being a non-expert in all of this, one thought I had is to break the design down into different components and look at those components in a more “idealized” state.

It seems to me that the driving force as to whether this water generating concept produces any meaningful results would be to see what happens inside a coil which spans two compartments of different ambient parameters and assume that the compartments themselves are insulated quite well from one another. p% of the coil would be in one compartment and (100-p%) of the coil would be in the other. So rather than analyzing the full cycle, I’m wondering if we could just put together a very “simple” model of a coil since that is where all the magic happens. What do you think?