EcoRenovator  

Go Back   EcoRenovator > Improvements > Geothermal & Heat Pumps
Advanced Search
 


Blog Register 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 10-02-14, 10:17 PM   #11
SDMCF
Apprentice EcoRenovator
 
Join Date: Jul 2014
Location: Finland
Posts: 117
Thanks: 5
Thanked 32 Times in 31 Posts
Default

Quote:
Originally Posted by buffalobillpatrick View Post
3/4" pex has 1" outside diameter
3/4" pex has 0,875" outside diameter
Source: Properties of PEX tubing


Quote:
So exposed area of tank is about the same area as 255' of 3/4" pex.
So exposed area of tank is about the same area as 291' of 3/4" pex.


I think we were both wrong in our original calculations. The real answer is a little more than you thought and a lot less than I thought. I should learn to check my mental arithmetic!

SDMCF is offline   Reply With Quote
The Following User Says Thank You to SDMCF For This Useful Post:
buffalobillpatrick (10-03-14)
Old 10-03-14, 06:35 AM   #12
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

I have made this mistake years ago and you are better to go with tanks in parallel. There is no way an ElSid will pump the way you want to. You will need a positive displacement pump to do that.

Thermo Dynamics Ltd. - Solar Pumps

It is the only way to ensure the air comes out without using a high head pump like a Taco 009 and do you really want almost 300w of power consumed?

Do it in parallel with a reverse return piping OR with diverting valves to charge up each tank to temp then off to the next tank. Supply for the heating can also be done this way. That way, there is little time lag between heating start and demand from the tanks to the house.

Also, just because you have the tank surface area, does not mean you will get the best heat transfer. There is proximity issues between the warm wall of the tank and water volume inside. There could be a big time lag. And while PE has a good temp rating, it is best to use it where you can limit it's exposure to very high temps. It doesn't like repeated exposure to temps above 85C (unlike PP which is OK with repeated exposure up to 110C). You do not want to be changing your tanks after 8-9 years or less.
Mikesolar is offline   Reply With Quote
The Following User Says Thank You to Mikesolar For This Useful Post:
buffalobillpatrick (10-03-14)
Old 10-03-14, 10:24 AM   #13
buffalobillpatrick
Master EcoRenovator
 
Join Date: Mar 2014
Location: Florissant, Colorado
Posts: 599
Thanks: 814
Thanked 58 Times in 54 Posts
Default

Jeff5may, thanks for that paper.
The 2nd paragraph in Conclusions sums it up:
Slightly better storage with parallel, but very difficult to balance. (Could be specific to this test setup)

Mikes polar thx. For insight. The El-Sid pump could not be used to provide flow for HP, I was thinking of low power slow circulation 24/7/365

Hehe got to love spell correction

HDPE is good enough for any temp. That system would provide.

Last edited by buffalobillpatrick; 10-03-14 at 11:33 AM..
buffalobillpatrick is offline   Reply With Quote
Old 10-03-14, 11:01 AM   #14
buffalobillpatrick
Master EcoRenovator
 
Join Date: Mar 2014
Location: Florissant, Colorado
Posts: 599
Thanks: 814
Thanked 58 Times in 54 Posts
Default

If tank 1 is positioned higher than the other tanks & it's water level is maintained above the pipes connecting the other tanks, I think that the head & flow issue that jeff5may raised would be eliminated.
buffalobillpatrick is offline   Reply With Quote
Old 10-03-14, 11:09 AM   #15
buffalobillpatrick
Master EcoRenovator
 
Join Date: Mar 2014
Location: Florissant, Colorado
Posts: 599
Thanks: 814
Thanked 58 Times in 54 Posts
Default

jeff5may

Quote:
If you had a header for pipes leading to the tops of the tanks and a header down low (or up top running to dip tubes), so that natural convection could occur, the parallel flows would balance due to the large horizontal cross-section and stratification due to density. With under a gallon per minute flow per tank, density and gravity would overcome your pressure difference.
I don't get what U R saying?

Last edited by buffalobillpatrick; 10-03-14 at 11:44 AM..
buffalobillpatrick is offline   Reply With Quote
Old 10-03-14, 05:52 PM   #16
jeff5may
Supreme EcoRenovator
 
Join Date: Jan 2010
Location: elizabethtown, ky, USA
Posts: 2,394
Thanks: 410
Thanked 604 Times in 506 Posts
Send a message via Yahoo to jeff5may
Default

BBP,

Before you go crazy digging up the ground, throwing a shopping list full of money full of parts and hardware, and installing who knows what, into this freshly dug hole, you REALLY should grab Dr. John's book, or better yet, go to one of his workshops in person or online:

John Siegenthaler P.E.

He really is the man with the plan in the field.

Here's a teaser of his book:

http://www.cengagebrain.com/content/..._01.01_toc.pdf

Google terms: john siegenthaler hydronic

Now, to answer your question:

In the series connected circuit, the flow is easy to understand, just like in a series electrical circuit. All the current flows through all the tanks, and with similarly sized pipes and fittings, the pressure drop is pretty much even between tanks. Your main losses in the hydraulic circuit will be in the long runs of pipe between the tanks. This loss will be huge unless you use large diameter piping.

You will need a pump that will deliver PSI's of pressure, not just inches of water. The longer your loop is, the more pump you will need to get the same flow rate. To be able to burp your tanks (if you can without bursting a container), you will need MUCH pressure. At a high flow rate, say each run of pipe between the tanks drops 2 PSI. At the first tank in the loop, you would have 18PSI of pressure built up! It would be much easier just to run bleeders to each tank with aquarium hose.

The parallel configuration is the complete opposite of what was just described. Your main loss will be on the other side of the heat store: the run to your heat pump and its outdoor-side heat exchanger. The combined flows to and from your tanks will act as a large-diameter pipe of short length compared to the series configuration. The tanks will all operate with nearly the same (low) head pressure. Therefore, you will not need a high-pressure pump to push lots of water through them.

However, with the split current flow, something must be done to ensure that the tanks all receive (close to) the same flow. That something is an endless source of debate, due to the inherent pressure drops and impeded flow mismatches vs. a "perfect" divided flow match. This topic matches well with the heat pump comparison of metering devices (cap tube vs. txv vs. eev).

What I did in a similar situation in the past (large hydroponic system with multiple parallel units) was dead easy: precision bottlenecks. I used a large header (1-1/2" pe pipe)that served as the main supply and drainback line, which carried water close to each unit. The main line was tapped with the same length (3 ft) of smaller (1/2") flex hose to feed each unit.

Each unit had an overflow that gravity fed back to the main tank, so it was easy to measure the flow rates. When measured, they were within 5% of each other. Adjusting flow rates was easy: for more flow, shorten the flex hose; for less flow, either lengthen the flex hose (tweaking) or stick a barb fitting in the end(big difference). No moving parts, works like magic. Done enough for us.

With a low-pressure supply of reasonably slow-moving water, the tanks and their natural equalization with each other due to stratification and convective currents is still a factor when initially brought out of equilibrium. Just as when the flow stops, the tanks will form thermoclines that line up with each other if they can siphon water freely with each other. The laws of nature don't care if a pump is running or not; they still work the same. The cold water will find the bottom of each tank on its own if not forced another direction.

Most professional engineers use sufficient mechanical means to obliterate these natural forces with flow control devices that drop way more pressure than what I'm talking about here. The natural tendency of the water to stratify is not changed, rather its means of escape is regulated by the engineered flow control.

Last edited by jeff5may; 10-03-14 at 08:35 PM..
jeff5may is offline   Reply With Quote
The Following 2 Users Say Thank You to jeff5may For This Useful Post:
buffalobillpatrick (10-03-14), Mobile Master Tech (03-15-16)
Old 10-03-14, 06:07 PM   #17
buffalobillpatrick
Master EcoRenovator
 
Join Date: Mar 2014
Location: Florissant, Colorado
Posts: 599
Thanks: 814
Thanked 58 Times in 54 Posts
Default

I have his book: Modern hydronic heating
&
Refer to it as required

I don't understand how low flow of hot water into bottom of parallel tanks will cause self equalization of flow?

Do U have any reference that I could read on this?
buffalobillpatrick is offline   Reply With Quote
Old 10-03-14, 08:37 PM   #18
jeff5may
Supreme EcoRenovator
 
Join Date: Jan 2010
Location: elizabethtown, ky, USA
Posts: 2,394
Thanks: 410
Thanked 604 Times in 506 Posts
Send a message via Yahoo to jeff5may
Default

Hot goes in and out the top
cold goes in and out the bottom
when in doubt, check your flow
even in tank not in the loop
don't fight mother nature
if you do, you better bring it

Last edited by jeff5may; 10-03-14 at 09:43 PM..
jeff5may is offline   Reply With Quote
Old 10-03-14, 11:35 PM   #19
jeff5may
Supreme EcoRenovator
 
Join Date: Jan 2010
Location: elizabethtown, ky, USA
Posts: 2,394
Thanks: 410
Thanked 604 Times in 506 Posts
Send a message via Yahoo to jeff5may
Default

The path to the most efficient and effective solution leads to utilizing passive and natural effects to your advantage. This goes up against modern methods of stringent artificial control of everything. Solar and ground heat transfer are not going to change by leaps and bounds over the long-term. You can aid mother nature by optimizing flows and rates and ratios, but it is inherently a game of diminishing returns. The key here is to follow the laws and rules of the system you are building.

The questions you are presenting lead in a direction that not many people understand. The answers you seek involve calculus, physics, engineering, and a wizard who knows how to make sense of them. These wizards typically make large sums of money answering these questions and making the magic into a working design. Things like enthalpy, entropy, gradients, and fluid dynamics are rather fuzzy. Making comparisons and decisions is all about trade-offs. Controlled mayhem, so to speak. Finding specific answers that pertain to your specific set of conditions, configuration and expectations of performance is going to be difficult.

That being said, here you go:

Richardson number - Wikipedia, the free encyclopedia

On the critical Richardson number in stably stratified turbulence - Galperin - 2007 - Atmospheric Science Letters - Wiley Online Library

http://en.wikipedia.org/wiki/Boussin...tion_(buoyancy)

Combined forced and natural convection - Wikipedia, the free encyclopedia
jeff5may is offline   Reply With Quote
The Following User Says Thank You to jeff5may For This Useful Post:
buffalobillpatrick (10-04-14)
Old 03-15-16, 09:19 AM   #20
Mobile Master Tech
Apprentice EcoRenovator
 
Mobile Master Tech's Avatar
 
Join Date: May 2012
Location: Atlanta, Ga
Posts: 142
Thanks: 38
Thanked 40 Times in 33 Posts
Default

BBP,

I agree with others on crushing problems. I've studied underground bunkers for prepping. Nearly all instances of using a square box (Intermodal transport containers), the container has crushed from the backfill. Anything underground needs to have purposely strong walls (like a concrete septic tank) or be spherical, round, or arched (like corrugated drain culvert).

If the purpose is seasonal energy storage, could you instead use the dirt under the house? As long as groundwater is low enough to not steal your heat away, you can store an awful lot of BTU's in the tons of soil beneath your home just by bringing it closer to your house's ambient temperature through a perimeter of shallow boreholes, then retrieve it as needed with a heatpump working extremely efficiently due to the low temperature differential. I touched on this in my "don't waste that heat" thread, and a number of others have worked on annual heat storage systems.

Most other methods of storage for more than a few days involve massive amounts of water in expensive vessels with a high enough temperature differential that much heat is lost to the soil anyway.

__________________
"Id put my money on the sun and solar energy. What a source of power! I hope we dont have to
wait until oil and coal run out before we tackle that." Thomas Edison, 1847 1931
Mobile Master Tech is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 09:09 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design