Moving Air Through a Conduit

Good Q.
HVAC isn't my thing, but I have a suspicion that a fan may push better than it pulls.
There may be a problem insofar as you can't keep sucking air out unless there is air flowing back in somewhere else, but presumably ventilation shafts would provide this?
Conduit material, wood is cheap, quick and a reasonable insulator.
Have fun...
Del

As you suck air out from the bottom of the shaft warmer air will be drawn in from the top, the surrounding rock should cool this, it has a greater capacity than your living quarters. Watch out for air leaks or you will be cooling the outside or sucking hot air depending on the location. It should suck as well as it blows but you will need to insulate / shade the conduit so you don't pick up heat en-route and defeat the cooling process you worked so hard to get. Is there enough shade to the quarters also?

Good luck!

It's better to push air than to pull it, but it will work. Where will you get the make-up air? Never mind. See above^ posts.

Funny, the first two answers were from people who probably don't need AC more that 10 days a year.

Be careful, there's an excessive heat warning in effect till tomorrow and it's supposed to hit 113 today. Come on in to town and cool off. You can swim in my pool, if you'd like.

Thanks guys. You bring up a point I had not considered. That is the make-up air. The location to suck or push from is the tunnel entrance which is also where the air enters the mine. It travels about 2,000 feet and comes out up the mountain side.

I'm thinking it would then be necessary to extend the intake further down the shaft. I would then need to calculate the rate the air is moving into the tunnel and the rate of suction out the conduit. Correct? and if so, what kind of formula would I use?

I'm assuming I will need a 12 volt motor and blower with an inverter and solar panel. How would I calculate and/or find these components?

Thanks again

'Calculate'? Sorry I don't understand the word .
I'm an experiment with what I have to hand paw sort of cat.
I'd say one of the most importand factors may be to have a close fit between fan and duct, else it will just circulate the air around itself.
A bit of experimentation will probably be quicker and cheaper than working it all out and then finding it's wrong
Del

Use 6" aluminium foil concertina air con ducting. It will resist the radiant heat.

Use your fan to blow and it will not collapse. Normal mine shaft/drive ventilation is done in exactly the opposite way using plastic vent bag.

Keep in mind if the shaft/drive vent is up the mountain the air will convect out the vent, so warm air will always be entering the lower entrance. best to locate your air pickup a long way in.

A blower is more effective pushing air than drawing air. In suction you create negative pressure in the duct/conduit, so you will require a rigid duct otherwise it may collapse.

Generally speaking you will require more 65F air than the normally used 55F air used by AC units. Off the top of my head I guesstimate you need 1500 to 3000 cfm to get the job done at these temperatures (a lot of air for a small space). Also, as pointed out by others, you will need to place the inlet deep enough into the mine shaft to prevent short-circuiting of the hot air into your conduit, so it could be double the length - say 200 ft. Size of the duct would be about 16" diameter.

Finally let's address the power required. To run this set-up will likely require between a 1 and 2 hp motor. Will the solar panel provide this type of power during the day? How will you power it at night?

Water is far easier to move, and is has much greater heat capacity due to density. Perhaps some type of run-around water loop would work much better.

Something to consider.

Cheers.

Someone suggested aluminium concertina tubing. This will not work as it is exposed to ambient air all the way and the air inside will be turbulent = excellent heat transfer, so you will lose the cool air to some degree. Another problem is viscous drag. Unless you are pipe is 2 feet in diameter you will get drag reducing the volume pumped.

you need an insulated tube, which can be a square wooden cage with plastic inside and out and a one inch air gap open at the end. Since you can get 2" square wood cheaply in 8 foot lengths, make them 8 feet long then tape them together and run them from the open shaft to the cabins and draw from 100 feet inside. use a squirrel cage blower, a house blower, with a 2 foot port, and make sure the motor is not in the air stream. You can also seal and pressurize the high point and seal and duct from the low point.

hard to do with solar as you will need 1/2 HP, but it is doable.

I would agree with Duane on this. It is far easier and more efficient to use water in this case. Think about an air cooled engine as opposed to a water cooled one.

What you have here is a geothermal source of cooling. If you a split unit air conditioner you can use the evaporator as the heat exchanger. Run 80 feet x 2 of 1" to 2" piping into the mine, coil the end that[s in there and bury it. If there is any pooling of water in there you are set, if not dig a hole and use the ground to absorb the heat. The water circulating through your evaporator should eventually stabilize somewhere below 80 degrees. Bury or insulate the piping to reduce heat absorption.

Here is a website to describe it. http://siamgpi.com/solarpower/geothermal-cooling.html

If not, why not sleep in the mine?

I'm getting quite the education here and it is appreciated. I had not considered water, but going that way has more possibles and would be more convenient.

Water is coming out of the tunnel 24\7 at a rate of 7 gallons a minute and is 64 degrees. It flows into a pond that is no more then 20 feet from the sleeping quarters. It also remains cool in the pond as it is well shaded.

As suggested, if this would do the job I just need to know how to use it; also basically described earlier. BTW, sleeping in the mine was becoming a reality if it could not be handled otherwise.

With appreciation,

AZ Miner

Hi AZ Miner,

In Australia some years ago you could buy portable domestic evaporative air coolers. Basically a box the size of a window airconditioner, fitted on 4 sides with aborbent straw material with a small pump drawing water from the base resevoir to the top of each panel and the water running down the straw walls. A fan blowing air across/through the walls provided air cooling to the surrounds. In these the water was recirculated and topped up but you could tap off the mine/pond flow. It increased the humidity but did cool. It was usually on wheels to move from room to room.

Maybe you could divert the water from the mine to quarters prior to the pond and discharge it to horizontal feeders (roof guttering) or pipes feeding to an absorbent curtain, with the excess drained to the pond, and some form of fan arrgt to push air thru the curtains. Or direct the water to a series of smaller curtained individual coolers with the drains connected to a common return to the pond. Even this added to an existing small fan may benefit.

Might need some odd plumbing and carpentry but as a method should give some relief to temperature without any great cost.

Good luck.

Good idea. Such as this?

http://ag.arizona.edu/pubs/consumer/az9145.pdf

bioramani

Consider comments of a previous relevant thread:

http://cr4.globalspec.com/thread/35857/How-to-Cool-Large-Battery-Banks

http://www.youtube.com/watch?v=R_Xx3M3I4DY

http://www.coolingzone.com/flash.php?id=6&pdf=true

Is the tunnel air fit for human consumption. AHas an analysis been done? In a continuous duct a blower of a given power will move the same quantity of air. It is easy to lay in a cable to conduct electric power to the point of use from point of generation. May be best to locate the blower in the duct at the tunnel bottom.

Assuming you have enough cold rock mass to cool the warm air entering the tunnel, check if enough surface area is available to transfer the required amount of heat. For an off the cuff estimate one can take it that 75 BTU/hr/square foot can be transferred.

For the temperature conditions given this translates to roughly 1cu.ft/hr/sqft air at 100 deg cooled to 64 deg. Knowing the rate of air flow required the required heat transfer area can be estimated.

Caution: There is no active cooling of the rock mass. You may be gradually heating up the tunnel walls and end up with diminishing returns.

Bioramani

If you can find one of these in an auction somewhere it would work quite nicely. I bought one for $25.00 four years ago. They where very popular in the high tech industry. It is a water-to-water chilling system. You would connect city water to one side and your system water on the other. Inside there are two motor & pumps and some well insulated coils that act as the heat exchanger. You could probably make this something like this yourself.

They come with 2 positive displacement pumps. Search for auctions on the Coolflow System I, II, III & IV, you might find one for cheap. I got this one from a Nortel Networks auction, now they are bankrupt or "Nowhere Networks". I didn't realize it's potential when I bought it. At the time, I just couldn't see the logic in connecting up to the city supply and having the water running all the time, the I realized it was for systems that already had a chilled water supply. The positive displacement pumps made it a great buy.

http://www.thermo.com/eThermo/CMA/PDFs/Various/File_26289.pdf

You could also try using a thermolator (water temperature controller) they are used primarily in the plastics industry. There are lots of used ones on the market. They are primarily used for heating the water, but you could just disconnect the heaters and connect to the cooling valve.

http://www.advantageengineering.com/temperatureControllers/SKVE/skveGeneral.php

An inexpensive alternative is to utilize a car radiator. My friend used this setup but with wood-fired hot water instead to heat his 1200 sq. ft. home during Georgia winters.

Place the radiator just inside the return air duct of the trailer A/C system and plumb it with 3/4" garden hose (inflow and outflow reducing adapters needed of course). A small water fountain, large aquarium, or swimming pool pump would be the source of constant, low-flow water movement from the 64 degree pond through the radiator.

It is clear that water is the way to go. I will digest as much as I can, the information and resources everyone has offered.

I would like to keep it as simple as possible. I just realized the trailer and quarters I'm trying to cool sits between the tunnel entrance and the pond. The water could easily pass through the trailer on it's way to the pond. There is no more then a 12' lift to the trailer and then down and into the pond.

It seems with a 12 volt (battery recharged by solar) system of water pump, some type of fan and device to run it through it could continue to cool the sleeping & living quarters 24/7.

I really do appreciate all the input and will post the resulting ?system?.

AZ Miner

A water powered pump may function well in this situation.

Seek 'ram pump info'

http://www.veoh.com/browse/videos/category/technology/watch/v208702Ampf7EeN#

http://www.google.com/search?q=ram+pumps&rls=com.microsoft:en-us&ie=UTF-8&oe=UTF-8&startIndex=&startPage=1&rlz=1I7ADFA_en

http://www.google.com/search?q=ram+pump+design&rls=com.microsoft:en-us&ie=UTF-8&oe=UTF-8&startIndex=&startPage=1&rlz=1I7ADFA_en

I have read most of the replys, and honestly to not claim to be an expert in moving air... However, I am an expert when it comes to many phases of practical Lighting.

And seeing as how we have our lighting fixtures in thousands of Chicken Houses, worldwide, I just wanted to pass this on:

Every single Chicken House in the USA, uses negative air.

They Do NOT push air, they pull it..

Wonder why???

Donald

They're hen houses

It's a lot easier to collect and treat the airborne chicken dust, feathers and odours at the exhaust of the ventilation fan than the multitude of openings in the chicken houses. On fan startup in a pressurised application you could coat the neighbourhood with all sorts of chicken bits.

It's a lot easier to collect and treat the airborne chicken dust, feathers and odours at the exhaust of the ventilation fan than the multitude of openings in the chicken hen houses. On fan startup in a pressurised application you could coat the neighbourhood with all sorts of chicken chook bits.

Negative air is commonly used in exhaust systems. Exhaust systems come in various configurations from panel fans mounted on walls, to ducted with branch lines sized accordingly.

Exhaust systems are used usually to remove odours and heat from point sources. In a chicken house I am sure that it is for odour removal. Bear in mind that the building will also require some make up air to balance the exhaust air.

For the OP's system, negative air would be problematic. Any air leakage (likely considerable in this case) in the built ducting would introduce hot air into the cold air stream which would be unacceptable.

Also, under negative pressure, the duct walls will cave inwards reducing air flow as the cross-sectional area of any built duct would be reduced and increase resistance to airflow thus requiring additional power to overcome the additional resistance caused by negative pressure. When we design ducted exhaust systems we take these factors into consideration.

Everything is contextual given the circumstances. Your experience in chicken farming does not translate well to this application. As a mechanical engineer I would not try to design the lighting for a chicken farm.

Cheers