Air cooled condenser

Anything cooling/condenser related.

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Re: Air cooled condenser

Post by googe »

Very cool shady :thumbup: , good.luck.mate hope it works good.
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Re: Air cooled condenser

Post by Jacksonbrown »

The fan will keep the air temp at the fins pretty close to ambient so your WAG should probably just be ambient.
If you want to do it properly then you need to do it each step, vapour to copper tube to aluminum fin to air.
Otherwise the simple answer that I put up would do it.
@ 50°F air, max knock down should be around 67% above what 100°F air max would be - assuming you're on neutral (175°) and not something hotter like straight water (210°) or something in between.
But like I said, the "hc" in your equation will change with the density of the fluid (colder air).
You'll also end up with a radial temperature gradient on the fin too so it should actually be the higher temp that gets brought down not the other way around.
Basically the delta t will be different all over the fin because the heat coming from the copper is only on one edge.
It's not that easy to work out properly but comparing one known (100°F) to another scenario (50°F) is a bit easier to guess.
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Re: Air cooled condenser

Post by MichiganCornhusker »

Hope this works out well. I'm building a new electric powered keg still and my available power supply is at a different location than my available water supply. Would be easier for me to use aircooled than run long water lines to the power location, or long power lines to the water location. I also like the idea of a heated shed in the winter, though that would take my efficiency down a bit over time as the shed warmed up.
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Re: Air cooled condenser

Post by shadylane »

I'll have some info when the water comes to boil.
Couldn't remember what the sized heater was in the boiler, so I checked it with an ohm meter and measured 12.8 ohms
So the heater is 4500w @ 240v I'll be using a fluke 77 multimeter to check the voltage and figure out how many watts are being used during the run. It won't be real accurate but close enough.
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Re: Air cooled condenser

Post by Jacksonbrown »

shadylane wrote: Couldn't remember what the sized heater was in the boiler, so I checked it with an ohm meter and measured 12.8 ohms
How did you do that? You do know the resistance of the element will be way off when it's cold?
You can measure a 60W light globe to see what I mean?
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Re: Air cooled condenser

Post by Jacksonbrown »

It might be easier to just measure the amount of water you can condense and work backwards to get the power.
Then add a few hundred watt for losses depending on your setup.
I know mine loses about 200W with an insulated keg.

I'm not doing it but basically it's doing the same thing as this but in the other direction
Joule is just work so Watts per sec.
You just need to put in your flow rate of x grams (mls) of water per second
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Re: Air cooled condenser

Post by shadylane »

At 4500w the aircooled condenser was knocking down all the vapor and the water out temp was close to 200f on #5 Condenser 1 had almost no output and was cool to the touch
Condenser 5 had the most, this is bassackwards from what I though would happen.
2, 3 and 4 were putting out almost as much as 5
Turned off the boiler and verified #1 wasn't stopped up.
Plugged up # 2, 3, 4 and 5 turned the heat back on to 4500 and #1 started blowing steam.
Turned the power down and #1 stop blowing steam and started dripping at 125v
The aircooled condenser was a success but I need to figure out why #1 isn't getting it's fair share of vapor.
Interestingly with all 5 open and running #1 seemed to have a slight vacuum ?
Installed the outlet manifold and the fins on #1 didn't heat up.
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Brutal
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Re: Air cooled condenser

Post by Brutal »

I think that vapor velocity will make a big difference in this condenser's ability to perform.

There are two different heat exchanges happening here. The ability of the vapor to transmit heat to the pipes of the condenser, and the metal's ability to transfer heat to the passing air.

When turning up the airflow over the outside of the condenser, the effect is twofold.

More overall heat is extracted from the metal of the condenser, but at the same time the amount of heat transferred to a unit of air is decreased. The air heats less per unit because of the shorter time exposed to the hot metal, but so much more air is heated that the effect is a larger volume of cooling.

Inside the condenser tubes the same principle is at work. If more vapor is pushed across a given surface area of condenser material it will eventually not transfer enough heat to condense fully due to the shortened time of exposure.

I've kinda lost my way with this thought. I think what I was trying to say was that these two factors have to work together to achieve a given amount of work. If one is deficient, then increasing the other will not be able to alleviate the problem.

EDIT posted while Shady did and haven't read yet. May have had a couple too many. Going to just read only for the night. Cheers folks
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Re: Air cooled condenser

Post by shadylane »

Jacksonbrown wrote:
shadylane wrote: Couldn't remember what the sized heater was in the boiler, so I checked it with an ohm meter and measured 12.8 ohms
How did you do that? You do know the resistance of the element will be way off when it's cold?
You can measure a 60W light globe to see what I mean?
"How did you do that" With a Fluke model 77 multimeter.
And your right the resistance of the heater will go up with temp. Positive temperature coefficent
Therefor the power will go down. Given a constant voltage.
The element in a light bulb would have a much bigger change in resistance compared to a water heater element due to the fact the temp changes several thousand degrees F on the light bulb
Long story short. The measurements are close enough for government work.
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Re: Air cooled condenser

Post by shadylane »

Brutal, what you said made since to me, must be drinking the same recipe :lol:
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Re: Air cooled condenser

Post by MichiganCornhusker »

Brutal wrote:I think that vapor velocity will make a big difference in this condenser's ability to perform.
Made some sense to me and I'm all hepped up on rum and Booner's.
Sounds like the vapor continued downline till it hit the end and went south. Then back as backup pressure may have required. Interesting that #1 wasn't even really needed. Very encouraging, cool post. (see what I did there, cool...?)
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Re: Air cooled condenser

Post by Jacksonbrown »

shadylane wrote: Long story short. The measurements are close enough
True. I didn't realise how small the effect was on lower temp elements.
My 2.2kW element works out out on paper to be 2.3kW, so about 5% off.

With the water measuring method you could have done each tube separately. It would give you some good figures to make scaling up or down easier once you get the header right i.e. one leangth of tube can knock down and cool x Watts of water vapour.

I vote vapour velocity too. Putting a bit more straight between the feed line and #1 would probably stop the vacumn and maybe add some sort of baffle too. To divert the feed out (like a mushroom or disk) or just a bigger header.

What are your plans now?
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Re: Air cooled condenser

Post by skow69 »

Sounds like you've found the amount of condenser necessary for the power applied. In terms of the equation, four tubes supplied sufficient A to balance q. The fifth one simply wasn't needed, and the fluid dynamics worked like MCH said. The slight vacuum you felt would have been from the Bernoulli effect at the top of number 1.Dt defaulted to the minimum. That would mean that if you reduced the power #2 would drop out, or if you increased it #1 would kick in.

I would also think that replumbing the tubes in series, then, would give the same result if you used 4 tubes. 5 tubes would give you cooler output, 6 tubes cooler yet, etc.

Good job shady. I think you have added some very valuable information.
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Re: Air cooled condenser

Post by Bagasso »

That places the knockdown power at about 1kw per section. Good to know before placing an order.
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Re: Air cooled condenser

Post by shadylane »

skow69 wrote: That would mean that if you reduced the power #2 would drop out, or if you increased it #1 would kick in.
I varied the power and #1 didn't kick in. I think there's design flaw in how the vapor enters the manifold.
I'll be making some changes tomorrow.
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Re: Air cooled condenser

Post by Danespirit »

+1 Brutal

In fact it might be the correct explanation for what's happened.
The vapor will have a velocity, entering the condenser, hence the output on 5 and the lack of it on number 1.
Vapors generated in the boiler, will simply pass by.
There will be some turbulence within the condenser.
If one thinks of a organ pipe, it could be compared to this in some degree.
Turbulence will slow the vaporflow towards the end of the condenser.
When the vapor finally reaches number 5, it would also have given off a large amount of heat.
This causes it to condense and distillate falls out...and ends in the section further away from the heatsource (boiler).
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Re: Air cooled condenser

Post by shadylane »

Here's an idea for modifying the manifold in an attempt to get even flow through all 5 condensers.
I think I made a mistake on the design of the first one.
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Re: Air cooled condenser

Post by Danespirit »

Narrowing down the pipe will result in higher vaporspeeds, due to the venturieffect.
Reynoldsnumbers will now change to turbulent flow instead of a more laminar flow.
This will further promote the output to condenserpipe number 5, making it worse than it was IMHO.
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Re: Air cooled condenser

Post by skow69 »

So whadaya thinkin there shady? That the expansion chamber before #1 will
a. reduce vapor speed,
b. cause turbulence.

I think you will get both, but in small portions. They will both favor #1 pipe, and not a difficult modification so you gotta do it to find out. More volume would help too. Give it a go. We're all dying to find out!

It will cool the vapor a bit, also , but prolly not enough to consider.
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Re: Air cooled condenser

Post by skow69 »

on your next test You might end by turning the power down slowly and watch how the tubes respond to diminishing heat. You can calculate watts from your meter right?
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Re: Air cooled condenser

Post by skow69 »

Just spitballin' here.

If you're determined to even out the pipes you could for sure do it by stepping the manifold down 4 times between pipes. ... which is exactly what you are doing now. Nevermind.

What I was thinking is it might take a lot of experimenting to find the perfect amount of restriction between pipes.

Damn arthritis medicine!
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Re: Air cooled condenser

Post by googe »

Awesome stuff shady, glad it worked.ok.for.you, your breaking new ground here :thumbup: . Id say the vapor speed when entering the manifold is blasting past #1 and causing air to be suck out of #1, is that what butal was saying?. I could see a expansion area for the vapor to slow and swirl around being beneficial?.
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Re: Air cooled condenser

Post by shadylane »

Thanks for the ideas, I can use all the help I can get :lol:
Here's the latest modification. I'll now if it works as soon as the water starts boiling.
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Re: Air cooled condenser

Post by Hound Dog »

See how it works and let us know. I think Jacksonbrown may have been right early on. Just a large header, not a tapered one would allow the vapor to collect and build up evenly to distribute more evenly for this design. I have to believe in the end it would have been more efficient to make one continuous zigzag set up. But the fun is in the experimentation! :thumbup:
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Re: Air cooled condenser

Post by shadylane »

This did the trick. :D
The numbers aren't exact due to the sawtooth wave shape produced by the phase angle controller and my volt meter being calibrated for a sine wave but there close enough.
100 volts = 780w all the condensers were dripping very slowly with #1 dripping slightly more than the rest.
150 volts = 1750w equal output on all 5 condensers.
200 volts = 3125w equal output all 5
240 volts = 4500w all 5 condensers pissing like a race horse with #1 the least, #5 the most.
Now I can finish the outlet manifold.
When I'm done everything but the five finned tubes and the fan will be loaned to a friend and I'll start over.
This time the finned tubes will be in series and in a zig zag pattern.
Don't know if there's enough room for all five of them, but I damn sure find out.
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Re: Air cooled condenser

Post by MichiganCornhusker »

Sexy! :thumbup: :clap:
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Re: Air cooled condenser

Post by shadylane »

If I had to do it again I'd recommend using 4 finned tubes and making the manifold out of 3 tee's and 6 elbow's.
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Re: Air cooled condenser

Post by Sungy »

your on the right track. Think 1960 muscle cars with those flowing header pipes. They are all the same length pipes just twisted differently so they all end up at the same place. The path of least resistance is where the vapor is going to flow until you add enough pressure to force the flow out where ever it can find an outlet. Your design enters at the left on the top and if you create an identical second header exiting on the bottom left the resistance should be the same causing equal pressure drops on each run. I think you will get better air flow if you space the fins 3-4 inches away from the face of the fan and box around the edges to create a space for the air to fill between the motor of the fan and the fins. There is not much air flow in the center of that style of fan. Air conditioners have at least 4-6 inches air space between fan motor and coils for this reason.
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Re: Air cooled condenser

Post by Brutal »

Some of the flow from #1 will be from condensed liquid entering and passing through it because it's the lowest point. That being said I am impressed that you got it evened out as mush as you did. Wet flow manifold design is a tricky subject, and dry manifolds aren't anything to sneeze at either. That's why I would have just built a snake (flat worm) and said fuck it. Would have drove me mad.
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Re: Air cooled condenser

Post by shadylane »

Think your right Sungy, the last manifold design does look like a tri Y header.
And moving the condensers farther from the fan would have helped.
But I wanted to keep the condensers close to the fan so the weight wouldn't make the contraption fall over.
I'm happy that the basic idea of an aircooled condenser works and 5 tubes were overkill.
I think using four tubes and a simple manifold would have been the best option.
Since this experiment worked. I'm now going to find a different way to make some more mistakes :lol:
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