A Brave New World
I am going to leave this historical Document Here
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I’ll update my original post to say we’ve pretty much debunked the benefits
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I agree I must say I gained some interesting information from this thread.
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The cycle times are longer, but you’re putting MORE air into the tank (PV=nRT), since the charge air at the tank is far cooler than it would be (200+°F) straight from the compressor, and you’re dropping a lot of mass in terms of water vapor out of the charge as well. So, while it might seem like the compressor is doing more work, it’s filling your tank with MORE (and cooler) air mass.
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How are you mitigating water condensing and collecting in the bottom turns of that cooler?
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That is correct but my tank output temp isn’t that much higher. I have a after cooler post tank that takes care of that. Even on long runs my refrigerated air dryer very sees inlet temp above the mid 70s.
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I used values posted by @Phillipw related to his experiment with and without the aftercooler pre-tank.
Given/Assumed
P = 145psi (assumed)
V = 140 gal (see above)
n = mols of compressed air
R = 8.314 (kgm^2)/(s^2K*mol)
T1 = 265 deg (compressor head temp see above)
T2 = 90 deg (aftercooler discharge temp - assumed didn’t see if he posted it)
No Aftercooler:
n = 158 mol / 2 min = 79 mol per min
Aftercooler pre tank:
n = 209 mol / 4 min = 52 mol per min
As you point out you can store more air in a cool tank. But when you consider the longer cycle times the increased gas storage does not overcome the longer cycle times.
This is an overly simplified calculation as the tank temperature would not be equal to the compressor head output temperature.
Also, I did not consider the air volume lost from the cooler each compressor cycle.
I believe if these variables were included it would show even more benefit to eliminating the aftercooler pre-tank.
I also used the True Gas Law and the change in results were negligible.
Values were entered in MATHCAD which allows the use of mixed units and converts the units internally for calculation.
Edit: I mixed up the results in my original post… its correct now. 
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I will add this as a rule of thumb my compressor has a 80 % duty cycle . I would always let it catch up when blasting… since I removed the aftercooler I can blast between 80 and 100 psi and I don’t have to stop the compressor will stay ahead of me. I do still give it a break from time to time.
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totally. also we should use the tank output temp considering the tank is a heat exchanger rejecting heat while its filling.
The tank is not at 200f , The mix air temperature of the tank will never be 200f . so you cant use 200f for the temperature of the air in the tank.
Also when using the ideal gas law to calculate air its is only a approximation because air is a mixture of gases and water vapour.
I firmly believe that short comings of the pre tank after cooler ( on a standard house hold compressor ) far exceeds any benefits.
I ve done it in the past but let us make a pro con list and see what it really ends up looking like .
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the RH of the air being compressed is one of the main wild cards when using the ideal gas law
" the density of air decreases with increasing humidity."
More water vapour = less dense air
So winter vs summer numbers will be very different
@72Pony thanks for posting. I was writing a very long winded ( pun intend ) response now, i dont need to .
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I am only concerned with the system operating in flow over time of use. So, that is not relevant.
I can’t speak to the science of it, but I deal with extremely large and long pneumatic systems in a steel mill. After cooling is critical and it is Amazing how many miles of pipe moisture will travel and build up to the point air valves are pouring water out when cycling and when it gets to freezing temps the nightmares that develop. We dealt with this for two years after our air dryer broke and it took a few months for the new one to show up and have it not be a broken unit.
In my home shop, I run a Eastwood scroll compressor, to 6 vertical runs of 3/4” steel pipe( so 3 upside down u runs) and have a drain valve at the bottom of each, to a standard filte, then a harbor freight air dryer. The pipes get a vast majority of the moisture and any blow by oil. I have nearly 0 moisture to be found after the air dryer. I say this because I have multiple automatic condensate drains as a precaution and I’ve never heard one go off. Only the one on the tank and the ac dryer but it’s not often on the dryer.
My shop is climate controlled though so humidity stays between 40-50% usually. Occasionally 55-60 during long rain stretches
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I’m not very smart and I will not argue the science that folks have worked out on cycle times etc. I will say that I catch a metric s**tload of water after the cooler and before the tank. I have a fraction of water in the tank that I used to. My Motorguard stays bone dry and the desiccant beads stay blue for a very long time, ( as opposed to a day in Oklahoma). If this is causing problems with my bought used compressor, I haven’t noticed. So for my usage, the after cooler brings enough benefit, I will accept the loss of efficiency.
But y’all are truly some smart folks! 
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One thing to think about if you put the after cooler post tank it will do the exact same thing without the extra load on your compressor.
I say that because you are not getting all the moisture out before it goes into your tank. It doesn’t matter in you have a tablespoon or a gallon of moisture the inside of your tank is still wet.
Then if you can’t tell a difference in cycle times you are probably getting a massive amount of blow by before installing a after cooler.
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First off, please understand that I am coming from a position of ignorance. Not arguing, just trying to squeeze all this into my brain, ( it’s rather clogged with hops, barley and bong resin). But if my objective is dry air and my air is SIGNIFICANTLY drier, with hardly any water making it to the tank, it would seem that I have met the objective, unnecessary wear and stress on the compressor aside. Also, if the aftercooler works by virtue of dropping the air temp from 300 to 90 to get the water to condense out, it would seem that, placing the aftercooler after the tank would not be dropping the temp at all, (ambient being 90 degrees. So, again, break out the crayons and tell me what I am missing.
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If you go back through the thread you will find I did have one pre tank then after some significant tests I did remove mine. If you like it there leave it. Not trying to sound rude. I am just saying it will catch massive amounts of water post tank with no harm to your compressor.
With all that said I ran my table hard this weekend 4 hours non stop except for sliding material forward. At the end of the day my air temp going into the refrigerated air dryer was only 80 degrees.
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Stop chewing on them and explain with the crayons. 
Also, truthfully, the ambient temp is 93 but, yeah.
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When I get around to the refrigerated dryer, I can definitely see losing the aftercooler.
Thanks Phillip
Keep it just move it they are very valuable.