EcoRenovator - View Single Post - IBC tote tanks in series as low cost HP source

jeff5may · 10-03-14, 05:52 PM

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.

10-03-14, 05:52 PM	#16
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	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..