/diy/ - Do It Yourself

[Anonymous No.1936338]

Hi
I want to bury 100m of pic related under the ground, and push air through it.
Is there an easy way to calculate the airflow I will get through it?
I was thinking something like a computer case fan at each end (one sucking one blowing) which can be powered by batteries (this is going off-grid)
Would that be enough or would the air in the pipe be too heavy for such small fans to have any effect?
I want to bury it outside my offgrid cabin, then have the two ends inside. In summer it'll suck in hot air from above and push the cooled air out the other end, and in winter when it's 0 degrees it'll reverse and push out 10-12 degree air

[Anonymous No.1936359]

>>1936338
>Is there an easy way to calculate the airflow I will get through it?
If you use two battery powered computer fans like you say then you can easily maintain the temperature of a cabin year round. I live in a zone where we have snow in the winter and 90F or higher in the summer, and I use two computer fans to maintain the temperature in a 2 bedroom house.

[Anonymous No.1936369]

>>1936338
For such a long run, you should use a pipe with a smooth interior. Corrugated tubes will cause a pressure drop due to turbulence along the way.

[Anonymous No.1936387]

>>1936338
PC case fans won't do shit for that length of run. Look at marine fans, they're designed to run off 12V DC.

[Anonymous No.1936397]

>>1936387
There are also high powered fans that run directly off of mains power.

[Anonymous No.1936398]

>>1936338
if your pushing out cold air you will make the original room colder thats how refrigerators work

[Anonymous No.1936445]

>>1936369
This, plus corrugated pipe is notoriously cheap and shitty. I’ve seen 2 year old corrugated pipe that’s already crushed in multiple spots.

[Anonymous No.1936471]

why don't you use sch 40 pipe?

[Anonymous No.1936896]

look up reynolds number calculations.

[Anonymous No.1936942]

>>1936338
>100m
How deep?

[Anonymous No.1936964]

>>1936359
I can only assume you are mocking me with this response.
I'll expand: The cabin is actually a caravan which is up on blocks, so it's not going anywhere (hence no fireplace)
>>1936369
good point, thanks, will try for something smoother
>>1936397
no mains power available
>>1936387
thanks, that's the type of info I was after! I'm a pretty light sleeper so of course looking for something quiet-ish
>>1936896
thanks
>>1936471
I can't only assume 'sch 40' means schedule 40 but from looking it up schedule 40 pipe can still be a bunch of sizes.
agi pipe is pretty cheap here in australia for 100m so was my go to option
>>1936942
probably about 1m down

[Anonymous No.1937989]

Should I use slotted or unslotted pipe?
My first instinct was unslotted, but then I realised that on a 100m run it's quite possible it's going to build up condensation & moisture inside it
then any moisture will have no way to escape except the main output, which will be into my living space

[Anonymous No.1938002]

>>1936964
in googling sch 40, how did you not absorb a definition? dont you realize we are just going to tell you to google it anyway?

[Anonymous No.1938004]

>>1938002
??

[Anonymous No.1938046]

>>1938004
>posts a table demonstrating the answer to his question

[Anonymous No.1938661]

>>1936338
if i understand your question.. what you're really wanting to do is use the earth's 60F/15C temperature for maintaining a year-round consistent temp right?

100m is crazy. that's probably either below your water table (if you're going straight down?) or it's lateral distance, in which case you aren't far enough down to get any kind of outcome.

your idea is pretty solid, but what you probably are wanting is to have a closed loop of coolant pumped through copper tubing with a radiator on each end. but it'll be expensive to build.

If you're hellbent on the tube/fan idea; remember for a given volume of air to be moved, the smaller the fan, the faster it must spin. Computer case fans are quite small, and thus spin quite fast -- they also don't move much air. they sure as hell won't move any air through a tube of that length/diameter.

[Anonymous No.1938664]

>>1938046
okay I get your cryptic original answer, we don't have 'schedule 40' pipes in australia so I thought it was a specific size, so good on you for being a dick about it
>>1938661
>what you're really wanting to do is use the earth's 60F/15C temperature for maintaining a year-round consistent temp right?
correct
My water table is minimum 6m down if not more (based on bore depths of neighbouring properties, yes it would be 100m lateral, also my property is higher than all the surrounding properties so it could be more
Thanks man you have probably given the most helpful answer, I'll consider the radiator idea though as you say it's a lot more expensive
summer it 40 degrees celcius plus the caravan is in an exposed location so it's going to be even hotter inside, though it is insulated

[Anonymous No.1938666]

>>1938664
on an aside schedule just refers to the thickness of the pipe; two most common here (in the US) are 40 and 80. schedule 80 is for much higher pressure. Schedule 40 is standard PVC irrigation pipe, usually 200psi @ 77f If i'm not mistaken. (google would give you a better answer)

i googled as well btw, you'd need to go about 3m to get 50F/10C so that might be pretty doable. There are a ton of 12v dc pumps you could use for moving the fluid if you went that route. (I just setup a solar/off grid irrigation project at my property using just such a pump).

[Anonymous No.1938672]

>>1938666
3m down might start to be a stretch as digging the trench would be a huge pain. unless I went 3m straight down
I was inspired by the greenhouse in the snow video https://www.youtube.com/watch?v=ZD_3_gsgsnk
do you have some sort of dam you pump the water out of via solar?

[Anonymous No.1938673]

also I want to grow Reed avocados but because there's frosts I want to excavate down 2m, then build a 2m above ground greenhouse, giving 4m height inside. it'll be 4m long so I can have 5 trees, which should be about 200 avocados a year
Hopefully doing this will stop any frosts killing the trees

[Anonymous No.1938674]

>>1938672
ah no, i have a spring that feeds into a storage tank; the pump then draws the water out of there.

I dug out a hole by hand roughly 5' in diameter and 5' deep to put the tank in; took a few days but wasn't toooo rough.

[Anonymous No.1938854]

Bernoulli's equation

[Anonymous No.1938862]

>>1938672
My pastor helped a guy in Kentucky do this. Buried corrugated pipe below the frost line in a circle, going into his trailer which was half-way underground. He just used box fans at either end. The geothermal temps maintained like 65 degF year round.

[Anonymous No.1938984]

[Anonymous No.1939153]

>>1936338
pipe is expensive as it gets bigger because the machines used to make it are bigger and it costs more to ship around. thats why OP is cheap because it collapses down and is small to ship.
air is a terrible conductor of heat which is why most people who do this pump some kind of water around instead of a fan.
i haven't done the research but i'm willing to bet you can get a big roll of shitty pex or whatever plumbing pipe like 15mm/1/2" ish and bury that in the ground with a liquid pump for about the same or cheaper than big pipe and pc case fans which will do quite frankly absolutely fuck all.
run the liquid through a radiator if you like.

[Anonymous No.1939587]

>>1938862
true I will see if I can manage larger fans, maybe run off a car battery or something. 65F would be sweet
>>1939153
a few people now have said go liquid, I'll investigate liquid pumps, it might be a better option

[Anonymous No.1940213]

>>1936338
>>1936369
You will want to optimize turbulence where you transfer heat as it will vastly increase convection coefficients.

You need to look at the pressure-flow curve for the drive element and necessary heat transfer rates.

[Anonymous No.1940375]

>>1940213
>mfw trying to understand this post

[Anonymous No.1941982]

>>1938661
>>1939153
I'm warming to this idea as I especially don't want mold issues from an air pipe.
Do you have suggestions of a type of radiator? Or is it a case of I could even use one I made myself?

[Anonymous No.1943321]

..h-hello?

[Anonymous No.1943764]

>>1940375
create turbulence in the pipe so that the flowing air spends moar time touching the wall of the pipe to exchange moar heat

[Anonymous No.1943788]

>>1943764
thanks.
that makes sense actually. I was thinking it makes sense to make the air flow less turbulant however you are correct
I've been warming to the idea from another anon above to use liquid instead. I'm not sure how well liquid would function when it's 45 degrees Celcius in the caravan though
My concern for using air would be any potential mould which grows in the system underground and is ultimately the air I would be breathing in
I guess the only potential downside for liquid would be any condensation that builds up on the above ground pipes

[Anonymous No.1945041]

>>1936338
>I was thinking something like a computer case fan at each end
I chuckled

[Anonymous No.1945067]

>>1936338
you're going to need more than a computer case fan bro, you need high static pressure. Look for fans that are long/depth and have fewer longer deeper fins.

[Anonymous No.1945068]

>>1936338
also you don't need 100m in one run. Normal houses have like 20-30 foot runs. You're better off having more runs.

[Anonymous No.1945098]

>>1936338
>100m
youre going to need a fan the size of your cabin to push anything through all that bro

[Anonymous No.1945167]

Dude like why dont you just run a solar powered water cooler

[Anonymous No.1945207]

>>1945167
>>1945098
>>1945068
>>1945067
>no one read to the end of the thread where OP is now interested in using a fluid filled system

[Anonymous No.1946833]

>>1943788
Not sure you'd get mold buildup in the pipe if it's constantly exchanging air with the living space. Maybe if there's water intrusion from underground or a low spot in the run that lets water condense and pool when the underground temp is higher than the environment temp.

Liquid sounds like a giant pain the ass. Harder to push than air and you have to run some kind of exchanger to get the heat out as it passes by.

[Anonymous No.1946841]

>>1936964
>>1936338
>>1939587
what are you trying to heat and from were also were do you live does it snow a lot is it hot what are the climates

[Anonymous No.1946857]

>>1941982
you can use even bigger car or truck radiator with fans

[Anonymous No.1948460]

>>1941982
>>1938672
Just an idea, but how about going straight down, but instead of digging a trench, hire a drill and sink one of these fuckers down vertically. Place a radiator of any type in your caravan and circulate.

[Anonymous No.1950165]

>>1946841
I am trying to heat a caravan. The caravan is on blocks so it's not moving anywhere
In winter it gets to 0 degrees C (no snow) and summer is 40-45 C. The caravan is in an exposed location so it will likely be like a hot box in the middle of summer
>>1948460
that's pretty nice, I'm not sure where I would find one of those as scrap here in australia.

[Anonymous No.1950222]

>>1938661
You can circulate air like 20' down and end up with nominally the same effect

It's how they make cheap greenhouses stay consistent temperature

If you're north of highway thirty, I would recommend a supplemental vented propane heater in the winter tho

[Anonymous No.1950223]

>>1950165
Dude, then you don't have to go that deep then. My only concern with your original idea was heat in the winter

Get smooth piping and put it as deep as you can

[Anonymous No.1950227]

Geothermal heating uses 100m long 1/2" soft copper tubing drilled straight down, carrying water. I saw one place use about 3 acres to bury larger pipe only 8' down flat. Air does not hold heat to transfer. It's not free heat either because you are running pumps and fans.

[Anonymous No.1950425]

>>1936338
Don't do air exchangers for geothermal. Do water and then put a fan coil and water pump.

[Anonymous No.1950961]

>>1950165
plant trees around caravan

[Anonymous No.1951673]

>>1936338
These are usually used for water but just experiment with heating and pressure you should be able to figure it out on you're own you don't need to do any math

[Anonymous No.1952908]

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