Heat Exchanger DIY

[PPBlimpy]

PP, You already have a broken chiller. What's wrong with it? Maybe that one could be fixed.

No idea. But don’t have the power in the room to run it without pulling another corcuit

 

[MoeStachio]

That's why he needs to discuss it with a geothermal company in that area.

The fluid needs to have enough distance.

No geothermal company is going to bother doing the math for a 200' loop of pipe in a 50' crawl space.

We can do the math here in 5 mins if needed. This is not a complicated setup or complicated math.

You'd be surprised.

And to do it properly, and optimize the system it can be complicated math

 

[bikerbutter]

My new system is having some temp issues. I really don't want to run a Chiller.
System is approx 400G. I am currently running a fan on the sump. will be installing another across the DT

my temporary fix is having my controller turning the closed loop and UV off when the tank hits 80*

I am looking at DIYing a heat exchanger, my crawl space in my house stays 20+ degrees cooler then house. Thinking about going down and digging a 18-24" deep hole and burying a 50' chilling coil of 3/8 OD 316 Stainless steel, adding a small pump to the sump to feed the buried coil and return back to the sump.

anyone done anything like this?

basic info about the system
300g DT 96x30x24 - acrylic
125G sump - acrylic

items generating heat- not including heaters - some producing a lot more heat then others.
-2 x 12000lph DC return pumps running at 90% ( probably 6k lph after head loss)
-1 x 9000 lph DC pump in DT to run a internal closed loop
-1 x 4400 GPH Submersible AC pump to run external closed loop - this pump is my biggest heat source. I didn't realize it was a submersible until long after purchased, bought 3 as a package deal so they are not being replaced anytime soon.
-1 x 57w UV sterilizer
-1 x submersible pump on Skimmer
-2 x gyro style wave makers
-1 x led refugium light ( original light from a fluval 13.5 evo)
- 4 x noopsyche K7 LED mounted 10" above tank.

Wow!! That's a really intelligent...and interesting idea. I can't see any problem with the logic of it. Please post your progress as I am very interested. Best wishes and thank you.

 

[BeanAnimal]

You'd be surprised.

And to do it properly, and optimize the system it can be complicated math

The math is not hard -- this is a very basic set of parameters. No surprises here.

They system is 300G
That means it takes 2,500 BTUs to raise or lower the tank temperature by 1 degree F
Lets say he runs at 78F and it takes 4 hours to hit 80F
that is 1250 BTU/h

That is a 1/10 hp chiller
The 1/3 is overkill. but gives you a ton of headroom.

As for a cooling loop.
68F crawlspace
Stainless tubing in air only move about 3 BTU per foot per hour if air contact is good. So 200 feet gives you around 600 BTU/hr—about half of what you need.

In 68F soil, tubing can remove 10+ BTU per foot per hour, so 200 feet buried can easily reject the full 1250 BTU/hr. The issue becomes the saturation (by heat) of the soil, and that simply depends on the crawlspace. It also assumes that this is a loop, not a coil of tube in one buried hole.

I can provide the actual math if needed, but I think the point is that the project is not A) worth the trouble unless it is a BIG crawlspace. and B) no geothermal company wants to be bothered with a project this absolutely tiny.

If he wants to buy controllers, pumps, and drill a thermal well or burry his entire property in a thermal loop... sure.

 

[PPBlimpy]

The math is not hard -- this is a very basic set of parameters. No surprises here.

They system is 300G
That means it takes 2,500 BTUs to raise or lower the tank temperature by 1 degree F
Lets say he runs at 78F and it takes 4 hours to hit 80F
that is 1250 BTU/h

That is a 1/10 hp chiller
The 1/3 is overkill. but gives you a ton of headroom.

As for a cooling loop.
68F crawlspace
Stainless tubing in air only move about 3 BTU per foot per hour if air contact is good. So 200 feet gives you around 600 BTU/hr—about half of what you need.

In 68F soil, tubing can remove 10+ BTU per foot per hour, so 200 feet buried can easily reject the full 1250 BTU/hr. The issue becomes the saturation (by heat) of the soil, and that simply depends on the crawlspace. It also assumes that this is a loop, not a coil of tube in one buried hole.

I can provide the actual math if needed, but I think the point is that the project is not A) worth the trouble unless it is a BIG crawlspace. and B) no geothermal company wants to be bothered with a project this absolutely tiny.

If he wants to buy controllers, pumps, and drill a thermal well or burry his entire property in a thermal loop... sure.

No don’t want to do anything of the sort. Just trying to think of low operating cost was to cool my tank indefinitely.

If the house wasn’t 2 stories and my tank wasn’t on an interior wall I would have done solar tubes for lighting.

 

[W31Olds]

I understand, it's a power consumption thing. If your goal is to lower the energy footprint, I would do an analysis of your Lights and consider a couple of Solar Panels to offset the cost required to run a chiller.

 

[PPBlimpy]

I understand, it's a power consumption thing. If your goal is to lower the energy footprint, I would do an analysis of your Lights and consider a couple of Solar Panels to offset the cost required to run a chiller.

It’s not even a consumption thing really. It’s getting an electrician out here to run another circuit.

I mean it is. Want to run the tank as cheap and efficiently as possible. At the same time I set up a 400g system so… kinda knew it was going to be expensive.

Anyways. Threw this out here as an idea. It brought I nice conversation along with it. This is something I have not really seen discussed.

Will I still look into it and possibly try it. Maybe. Wouldn’t be very hard to do.

If I do it I will make sure to update

 

[BeanAnimal]

It’s not even a consumption thing really. It’s getting an electrician out here to run another circuit.

I mean it is. Want to run the tank as cheap and efficiently as possible.

Let's say that 1/4 HP chiller runs for 4 hours per day.... say 600W. That is 2.4 kWH per day. So call it $0.30 or rounding up $10 per month or $120 per year.

You are going to easily spend $500 by the time you build even a basic cooling loop -- likely more, all in time and materials. Where is the savings and are they worth the effort?

Anyways. Threw this out here as an idea. It brought I nice conversation along with it. This is something I have not really seen discussed.

There are some old threads are RC. There are three systems that were notable. One of them, the poster had geothermal well drilled for the home, but had the tank on its own heat exchanger and zone.

The other was a DIY project where the person dug a several thousand foot long trench around their property and put in a loop for a large system.

Lastly, I remember a thread where somebody pulled a loop of tubing through an underground conduit loop that connected the home to an outbuilding somewhere on the property. He ran tank water through but could not keep the flow high enough to prevent the tube from clogging every few months... or something to that effect.

 

[PPBlimpy]

Let's say that 1/4 HP chiller runs for 4 hours per day.... say 600W. That is 2.4 kWH per day. So call it $0.30 or rounding up $10 per month or $120 per year.

You are going to easily spend $500 by the time you build even a basic cooling loop -- likely more, all in time and materials. Where is the savings and are they worth the effort?


There are some old threads are RC. There are three systems that were notable. One of them, the poster had geothermal well drilled for the home, but had the tank on its own heat exchanger and zone.

The other was a DIY project where the person dug a several thousand foot long trench around their property and put in a loop for a large system.

Lastly, I remember a thread where somebody pulled a loop of tubing through an underground conduit loop that connected the home to an outbuilding somewhere on the property. He ran tank water through but could not keep the flow high enough to prevent the tube from clogging every few months... or something to that effect.

Those are all crazy!

I guess for now I will pull an extension cord from another room and check out this chiller. I picked it up for my daughters axolt tank but was able to keep the temps good with a fan only

 

[BeanAnimal]

Those are all crazy!

I guess for now I will pull an extension cord from another room and check out this chiller. I picked it up for my daughters axolt tank but was able to keep the temps good with a fan only

What make you think you are that close to capacity in your existing circuits?

 

[PPBlimpy]

This room is under a single 15amp circuit.

Lights, ceiling fan, tv , tank, wife’s computer/printer for work.

I had trouble popping the circuit when I have my 45g frag tank in here with my big tank and my wife’s office.

Anytime my wife went to print something or my lights on the big tank came on in the morning it would pop the circuit. I moved the frag tank out and haven’t had the issue. I also replaced the breaker with a fresh 15amp.

I need to get a watt meter to measure the tank.
Once I get my controller up and running I will be able to figure out what the tank is drawing

I need to get an electrician out anyways and run two dedicated circuits to the tank for piece of mind. I have other equipment I will be installing eventually including more lighting.

 

[PapiJuan56]

On my aquaculture farm I have made my own DIY heat exchangers that have worked pretty well. In Hawaii everything corrodes fast. Plastic, metal, everything. I have used funny pipe/swing pipe (most commonly black) and it has lasted many years and more efficient than pex in my experience and environment. I use my heat exchangers to supply my saltwater tanks and pbrs with constant deep seawater. I am right next to the ocean and our saltwater comes directly from 3000 ft depth so it's pretty darn close to freezing so I have to acclimate it.

 

[Harpo]

I would not use SS tubing as some SS can corrode and Titanium would be cost prohibitive.

That is why I used PEX

 

[BeanAnimal]

On my aquaculture farm I have made my own DIY heat exchangers that have worked pretty well. In Hawaii everything corrodes fast. Plastic, metal, everything. I have used funny pipe/swing pipe (most commonly black) and it has lasted many years and more efficient than pex in my experience and environment. I use my heat exchangers to supply my saltwater tanks and pbrs with constant deep seawater. I am right next to the ocean and our saltwater comes directly from 3000 ft depth so it's pretty darn close to freezing so I have to acclimate it.

Thin wall swing pipe is certainly a better choice than pex for thermal transfer. I would love to see your tanks! Are you in the technology park with the Natural Energy Lab? Reading about it now.

 

[MoeStachio]

You'd be surprised.

And to do it properly, and optimize the system it can be complicated math

The math is not hard -- this is a very basic set of parameters. No surprises here.

They system is 300G
That means it takes 2,500 BTUs to raise or lower the tank temperature by 1 degree F
Lets say he runs at 78F and it takes 4 hours to hit 80F
that is 1250 BTU/h

That is a 1/10 hp chiller
The 1/3 is overkill. but gives you a ton of headroom.

As for a cooling loop.
68F crawlspace
Stainless tubing in air only move about 3 BTU per foot per hour if air contact is good. So 200 feet gives you around 600 BTU/hr—about half of what you need.

In 68F soil, tubing can remove 10+ BTU per foot per hour, so 200 feet buried can easily reject the full 1250 BTU/hr. The issue becomes the saturation (by heat) of the soil, and that simply depends on the crawlspace. It also assumes that this is a loop, not a coil of tube in one buried hole.

I can provide the actual math if needed, but I think the point is that the project is not A) worth the trouble unless it is a BIG crawlspace. and B) no geothermal company wants to be bothered with a project this absolutely tiny.

If he wants to buy controllers, pumps, and drill a thermal well or burry his entire property in a thermal loop... sure.

That's the very basic math yes.


The math I'm referring to is far more complex and requires referencing several region specific charts and adjusting accordingly.

Between ambient ground temperature, elevation, the heat gain and heat loss calculations for the crawlspace, pump specs, offsetting for any heat provided by the pump itself, and of course the variables provided by the choice of material, and depth of the hole:


I suspect to do what he needs done, it will cost far more than it will provide in value over the life of the tank...

This is of course assuming we're building this thing properly, and not just chucking 200ft of tube into a hole in the ground.

 

[BeanAnimal]

That's the very basic math yes.


The math I'm referring to is far more complex and requires referencing several region specific charts and adjusting accordingly.

HI - I don't think that you understand the scope here, or are inflating it for some odd reason.

The OP isn't (wasn't?) entertaining a full-scale geothermal system, or even a small scale one. He asked about a simple passive loop to reject ~1250 BTU/hr, from his aquarium. Which is the load of a few 100W light bulbs.

You don’t need region-specific thermal modeling or licensed engineering for that. Burying 200 feet of stainless tubing in stable 68°F soil in with good contact is absolutely sufficient for this scale. It's a crawl space. If it stays below tank ambient and above freezing, that is all that matters. He is not going to be thermally limited by the surrounding soil conditions or eclipse his efficiency by driving this with a 50 W loop pump.

There is no need for pump spec sheets, soil conductivity surveys, charts, etc. It is just bare bones basic thermodynamics. If he were heating or cooling a house, sure, call in the experts. But removing removing a few watts of heat from the sump to the crawlspace soil is not complicated.

Very basic math, yes. But, we can go as far beyond basic as you wish. It would be a pointless exercise in this case. Even at the small scale he had wished for. The limiter here is less about thermal capacity and more about net return in investment (or savings) vs other simpler means of removing the the heat.

 

[PPBlimpy]

So just for reference on my system. 300G DT with 125G sump. Sump holds approx 80G when tank is running.

At 5pm last night tank was sitting steady at 79* - Closed loop and UV sterilizer had been turned off all day. House was sitting at 75*

My lights turn off at 9pm.

At 5pm I plugged in just the closed loop as I wanted to see how much it is effecting the tank.
Fast forward to 5:30 am, so running closed loop for 12.5 hrs, tank is sitting at 79.9

The Closed loop pump is a 155W AC / 4400gph submersible, wish it was an external but it came in a package deal and using what I have available.

At 5:30 AM I shut down the closed loop and turned on the 57w UV Sterilizer. I am wanting to see what the load of the UV does compared to the CL.

 

[BeanAnimal]

The 155mW pumps puts 155 W of energy into the water. Minus a tiny amount escaping via sound, and tiny amount being stored by coral growth or other mechanisms, most of that is heat.

The same is going to be true of the UV.

Your added heat load is ~200 watts, wich is 628 BTU/h
A 1/10th horsepower chiller has a capacity of over 1200 BTU/h

You have 300 gallons of water -- 2500 pounds.
It takes 1 BTU to raise 1 pound of water 1 degree F.

If your tank were fully insulated, it would take your loop and uv 4 hours to raise the tank 1F
Your tank is not insulated, so the higher the temperature, the faster heat moves from it to the lower ambient temperature of the room. The math is not worth the hassle, but 6-8 hours is reasonable.

 

[PPBlimpy]

The 155mW pumps puts 155 W of energy into the water. Minus a tiny amount escaping via sound, and tiny amount being stored by coral growth or other mechanisms, most of that is heat.

The same is going to be true of the UV.

Your added heat load is ~200 watts, wich is 628 BTU/h
A 1/10th horsepower chiller has a capacity of over 1200 BTU/h

You have 300 gallons of water -- 2500 pounds.
It takes 1 BTU to raise 1 pound of water 1 degree F.

If your tank were fully insulated, it would take your loop and uv 4 hours to raise the tank 1F
Your tank is not insulated, so the higher the temperature, the faster heat moves from it to the lower ambient temperature of the room. The math is not worth the hassle, but 6-8 hours is reasonable.

I appreciate you man, the wisdom, sharing and always enjoy your responses and conversations.

Your estimate here sounds spot on.

Thank you.

 

[BeanAnimal]

I appreciate you man, the wisdom, sharing and always enjoy your responses and conversations.

Your estimate here sounds spot on.

Thank you.

Math doesn't lie as long as we make reasonable assumptions in its application :)

Thanks for the kind words. I try to help where I can.

As you have already come to realize -- the fans can be very effective. They don't blow heat away by convection, what they are doing is driving evaporation. The fast you move wet air away from the water surface, the faster the new dry air can absorb some of that moisture. You get over 8700 BTUs of cooling per gallon evaporated. The drawback us that you are adding that moisture to the house. In your case, as long as your AC runs a decent cycle the moisture will be removed by condensation on the coil.

As somebody else indicated, a cheap mini spit could also do wonders in the fish room. Lowering ambient temperature and humidity. This both increases the delta T between tank and room (faster energy loss from tank) and increases the rate of evaporation.