Heat Exchanger DIY

[PPBlimpy]

This is why I was considering 10X the length of tubing in plastic; it’s far less efficient as a thermal conductor, but the increased length (likely still for less cost) compensates for that, at least somewhat…

That's a big hole I would have to dig in my crawl space

 

[PPBlimpy]

Next question. I have two chillers here. one does not work. i have not taken it apart yet but what does the heat exchanger look like in a 1/3 hp chiller? what is it made from?

 

[PPBlimpy]

Amazon does have a titanium could. $177 5/8 OD more then I want to spend but it’s why I asked the question above

 

[PPBlimpy]

Also found this one in titanium

5/8 of tubing
16.5in x 6.3in for $117. That’s a pretty big coil.

If viable I think the project could be done for under $200. Titanium coil, pex pipe and fittings small pump

 

[BeanAnimal]

It’s a fascinating idea! I’ve never gone that in-depth with the thought…


Excellent point! You could also just have a manual sump heat sink bypass for the cold winter months…

— I’m going to have to think on this one a bit more… I could see utilizing it as well!

Again, why the complexity. You turn the pump on and off as needed.

 

[BeanAnimal]

This is why I was considering 10X the length of tubing in plastic; it’s far less efficient as a thermal conductor, but the increased length (likely still for less cost) compensates for that, at least somewhat…

On a huge geo loop, yes, but in a 50' crawl space the soil area is limited so thermal conductivity of the loop and its surface area become important.

1/4 of the basement is walled off and was originally used as food storage. There is a pit that going down at least 6’ below basement floor.

These are called cold cellars - most homes had them before refrigeration. Either as part of the home or nearby set of stairs going to an underground storage room near the home. They also served as storm shelters.

 

[MoeStachio]

*puts on his HVAC guy hat*

What you're talking about is a geothermal heat pump system

Typically iirc, it's HDPE tubing in the ground, distributing heat to the ground in the summer , and picking up heat in the winter.

It could work for a tank system.

However, the depth of the hole is crucial. You have to get below the frost layer, or you'll run into issues in winter.

Heat always transfers from hot to cold, so a closed system would need a reservoir of tank water (the sump would work) and the geothermal pit.

The calculations required can be pretty complex.

Interested to see how this works

 

[PPBlimpy]

*puts on his HVAC guy hat*

What you're talking about is a geothermal heat pump system

Typically iirc, it's HDPE tubing in the ground, distributing heat to the ground in the summer , and picking up heat in the winter.

It could work for a tank system.

However, the depth of the hole is crucial. You have to get below the frost layer, or you'll run into issues in winter.

Heat always transfers from hot to cold, so a closed system would need a reservoir of tank water (the sump would work) and the geothermal pit.

The calculations required can be pretty complex.

Interested to see how this works

Frost level in my area is around 18” in the winter. Was looking to go 24” but maybe 30” would be better.

Why run it closed loop? I think that complicates things.
I was thinking of pumping from sump, thru coil assembly and back into the sump. Soil around coil cools aquarium water being pumped thru coil and returns it to the sump.

 

[MoeStachio]

*puts on his HVAC guy hat*

What you're talking about is a geothermal heat pump system

Typically iirc, it's HDPE tubing in the ground, distributing heat to the ground in the summer , and picking up heat in the winter.

It could work for a tank system.

However, the depth of the hole is crucial. You have to get below the frost layer, or you'll run into issues in winter.

Heat always transfers from hot to cold, so a closed system would need a reservoir of tank water (the sump would work) and the geothermal pit.

The calculations required can be pretty complex.

Interested to see how this works

Frost level in my area is around 18” in the winter. Was looking to go 24” but maybe 30” would be better.

Why run it closed loop? I think that complicates things.
I was thinking of pumping from sump, thru coil assembly and back into the sump. Soil around coil cools aquarium water being pumped thru coil and returns it to the sump.

You want it closed to prevent bacteria and gunk build up, and stability.

You could use salt water in the line, as it will conduct heat to and from, but I wouldn't recommend tank water.

Another consideration for this would be the temp swing affecting any copepods etc.

If you're going to go this route I highly recommend discussing the science with a geothermal company in your area as they'll know all the relevant math.


But in principle, it would work.


PIT> Geothermal system> sump (closed coil)


The heat will warm the solution in the system and transport it to the pit, heating or cooling as needed, and return it where the sump will pick up or deposit the heat.

 

[PPBlimpy]

I am not questioning the bacteria argument being bad but curious on how it would be introduced into the lines?

i may look into a geothermal company like you suggest

 

[W31Olds]

PP, please enlighten me. Why do want to avoid running a chiller. Noise, initial expense, power consumption? Designing and building a Geothermal cooling system sounds intriguing but with unknown reliability and inadequate design, would be an unacceptable risk to my tanks inhabitants. You may not need a very large chiller if your Tank is for the most part maintaining Temp with Fans.

 

[BeanAnimal]

*puts on his HVAC guy hat*

What you're talking about is a geothermal heat pump system

Typically iirc, it's HDPE tubing in the ground, distributing heat to the ground in the summer , and picking up heat in the winter.

It could work for a tank system.

Those loops are far larger than the scale of what the OP is looking to do. He is simply trying to use the cooler earth of a sheltered crawl space.

 

[BeanAnimal]

PP, please enlighten me. Why do want to avoid running a chiller. Noise, initial expense, power consumption? Designing and building a Geothermal cooling system sounds intriguing but with unknown reliability and inadequate design, would be an unacceptable risk to my tanks inhabitants. You may not need a very large chiller if your Tank is for the most part maintaining Temp with Fans.

If simply turning off the UV keeps temps in check then a 1/10th HP chiller would likely be more than enough.

I would imagine the simple closed loop running through the crawl space would work as well - but materials and time? The chiller is going to be cheaper and easier to implement.

 

[MoeStachio]

*puts on his HVAC guy hat*

What you're talking about is a geothermal heat pump system

Typically iirc, it's HDPE tubing in the ground, distributing heat to the ground in the summer , and picking up heat in the winter.

It could work for a tank system.

Those loops are far larger than the scale of what the OP is looking to do. He is simply trying to use the cooler earth of a sheltered crawl space.

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

The fluid needs to have enough distance.

Where I live, geothermal is a 5 minute discussion and one test question in school.

It's too cold here, and too expensive to do, and you're required to have a back up for your house heating if you do.

So the math required here isn't my forte.

In theory in works. In practice it's probably too expensive to do and likely the depth requires a permit from the local government

 

[redfishbluefish]

Very interesting concept.

First off, no stainless.....it won't last.

I know I'm not going to find it, but someone way smarter than me did the calculation of using a minifrig with a coil of plastic tubing (I think in a buck of water within the frig) and it wouldn't work. Would require a long coil and slow movement of water within the tubing.

Anyway, do what I did....this assumes your tank is with a reasonable size room....put in a small window air conditioner. A 5000 BTU unit is less than $200 and this way I don't need to run my entire house when the temp isn't that bad.

 

[UncommonSense]

On a semi-related note; here’s the “sump” for my 200g-ish outdoor deep water culture aquaponic system…

It’s uglier than sin/well overdue to be completely redone; I did it back as a teenager… But, it’s been reliable for many years! — I attribute a lot of the system’s stability in such a primitive format to the 55g drum being buried partially!

I would be curious to do some research on integrating a basement sump into a concrete slab for a temperate system…

 

[BeanAnimal]

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.

 

[BeanAnimal]

I know I'm not going to find it, but someone way smarter than me did the calculation of using a minifrig with a coil of plastic tubing (I think in a buck of water within the frig) and it wouldn't work. Would require a long coil and slow movement of water within the tubing.

I wrote an article about the limitations of dorm fridge chillers almost 2 decades ago

https://beananimal.com/articles/dorm-fridge-aquarium-chiller/
-- as they were all the rage back in the RC days. "But if you just add a bucket of water" or "Ohh it will work better if you add more tubing". The issue is not the tubing, it is the capacity if the dorm fridge :)

 

[W31Olds]

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

 

[BeanAnimal]

Next question. I have two chillers here. one does not work. i have not taken it apart yet but what does the heat exchanger look like in a 1/3 hp chiller? what is it made from?

It is a titanium coil in a plastic shell. Refrigerant runs through the coil and tank water around it.

What is normal tank temp?
How fast does it go from normal to 80F, worst case.