Quote:
Originally Posted by Acuario
Ok, in the case of the Daikin they provide a pre-built external box, presumably with the typical heat matrix, fan etc. but it's the idea of being able to effectively use the ground source principle of 2 'water' circuits + the closed loop refrigerent circuit that has me interested..
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OK, I understand where you're going here...
Too bad about the soil (rock) conditions there. It would be truly useful to have an earth reservoir, not only for heat harvesting, but also for heat storage. But if the rock conditions are as bad as you say, then that's not an option. (However, you might want to monitor what Geo NR Gee is doing, on the 'manifesto' thread, with regard to drilling through rock. He has acquired a tricone bit and is about to do some rock drilling, himself)
So, you're considering using multiple ASHP heads, each feeding into a brine circuit, and an evaporator HX for extracting the heat from the brine circuit. Correct me if I got that part wrong.
Since you're making your own HXs, you may not have any performance data, so this is gonna have to be a pretty intuitive endeavor. Either that, or you can build slowly, do performance testing as you go, and adjust as measurements dictate.
Some thoughts I have about this project:
- Brine is corrosive. you won't be able to use inexpensive iron pumps or valving.
- You'll want to insulate the brine loop to keep the heat in.
- You'll want to size your brine loop flow rate to accommodate your maximum load situation. There will be times when you won't need to run the maximum number of ASHP heads.
- Controlling the various heads, pumps and fans will be a creative challenge in itself.
- You'll want to size the brine loop, so as to reduce friction, so that you don't need a large circulation pump. This involves factors such as: fluid viscosity, fluid flow rate, pipe diameter, heat exchanger head loss, check-valve head losses, and pipe length.
- Since you'll likely have a varying number of ASHP heads coming on and off, you'll probably want a 'smart' circulation pump like the Grundfos Alpha or similar.
- I would think that having your ASHP heads in parallel, with a check valve on each parallel branch would be the best approach.
- There is an 'inefficiency penalty' of about 10% per heat exchanger, so you'd pay the penalty at the ASHP/brine heat exchanger, and also at the brine/inside heat exchanger.
- If you had some kind of heat storage tank, like a big water tank that was well-insulated, it would open up other possibilities, such as solar heat storage, when available, bio-mass heat storage, propane or oil or gas heat storage, if there were favorable market fluctuations, storage of 'waste heat' from refrigerators, generators, etc.
As a source of helpful information,
here is a link to some information that could prove useful to designing and implementing this project. For starters, I would reccomend issue 9, from 2011, titled: "Geo-Hydronic Systems". I recommend this one for it's treatment of heat transport and fluid mechanics. Others may be equally valuable, and since you are a clever maker, you can probably fabricate many of the items they are trying to sell you.
All in all, I think this would be a great project. No one else on EcoRenovator has seriously proposed a project that has so much potential. From what I have seen of your clever and persistent approach to solving problems, I think you will surely succeed.
If I or anyone else on this forum can be of help, please ask. Let us know about on-going ideas, problems, progress.
Good of luck on this project. Don't forget,
lots of pictures!
Best Regards,
-AC_Hacker