Air Compressor lines, cooling copper

[misterfixit]

I will be installing a new 5hp/80gal. compressor soon. This will replace my small roll around unit. My question is about cooling the air/piping immediately after the compressor. Is that something I need to worry about? If so, what is the best way to do so?

I will be using copper pipe, and my currently planned layout will only have about 35' of run from the compressor. I will be running mist coolers in my machine shop, as well as a 'sandblast' cabinet, and general air outlets for other tools. I will very occasionally use air for painting in the shop.

 

[Firebrick43]

copper is great for its emissivity and conduction.

However natural cooling while helps, once you get the air down to ambient temp more pipe is not going to help.

If you have the pipe going to the ceiling(with drip leg) and run a few feet to a drop(again with drip leg) you will have enough cooling. A water separator before the quick connect helps to

At a whatever ambient temp is determines the max amount of water air can hold. So the only way to get more water out is to use either absorption system(not practical for large quantity of air) or use a refrigerated dryer to lower the temp and therefore the dew point.

So at what point does it "MATTER" , well in hot moist environments sandblasting and painting definitely it could matter. For painting the make absorption filters to deal with it and if not painting often its better just to go this route.

 

[pancho400cid]

When I did a similar thing, I read somewhere that by the time any air traveled down the pipe 20 feet it was at room temperature. I think that's about right.

As you noted, air heats when compressed and expands when it cools. If expansion cooling drops the air temp below the dew point of the air going into the compressor (very often does), moisture condenses in the lines, etc.

So... long story short (too late!) I plumbed 3/4" copper up, then over, then once down and back up the wall putting the length at "about" 20' or so, with a drain valve at lowest point of the last up leg before the regulator. Then the pipes go to a coalescing filter regulator. I've never seen water come out of it, and only rarely need to drain the filter.

For painting I put a dessicant drier after the filter above, but only for painting. The air is dry enough for tools, blasting etc.

 

[pcmeiners]

"If you have the pipe going to the ceiling(with drip leg) and run a few feet to a drop(again with drip leg) you will have enough cooling"

"When I did a similar thing, I read somewhere that by the time any air traveled down the pipe 20 feet it was at room temperature. "

True if you use a low volume of air for a short period of time. If you using high volume, once your tank heats up your line will follow in suit in a short time. Copper is not a great radiator of heat (without fins), iron as in iron pipe actually gives off more heat. Copper conducts heat better, that does not mean it gives off heat better.
Either a spray gun, air tools or blasting will use high volumes of air, the copper runs will not cool the air down after a few minutest of use. With sand blasting you may get away with just an aftercooler and a filter, it all depends on the ambient humidity level/temperature.


If your running mist coolers, you are cooling by adding moisture into the air, you might be better off supplying compressor intake air piped from the outside. Any moisture added to the air by misting will need to be compressed 1700 times to drop out as water, that is wasted compressor power.

I live in NYC, if I did not have an aftercooler I could not paint in 3 seasons. Yes I can actually paint lacquer because the moisture mixes in, enamel forget it. I do not want moisture mixing with paint in the first place. Even with the aftercooler, the air needs more moisture removal from either a refrig drier or desiccant drier. The reason to use an aftercooler first is it removes approx.. 70% of the moisture at almost zero cost. You particularly would not want to use desiccant drier along, as they are very good driers but have a very limited amount of water they can remove per volume of desiccant . As is I have one I made up, super sized from a line dryer bigger than the one in the link in case I need to spray in a shop with no moisture removal devices.

https://www.ebay.com/itm/SPORLAN-C-...024958?hash=item2cbb5d73fe:g:OA0AAOSwnB1ZuZD7

 

[Firebrick43]

Copper conducts heat better, that does not mean it gives off heat better.

While copper(or any pipe) does indeed do better at heat transfer with fins because of increased surface area, it does release heat better than iron, nearly 4 times better dependent on the specific alloys involved. This is why many high performance radiators and air/water or water/water heat exchangers do use copper in when compactness is paramount, with or without fins.

Conductivity is a measure of how heat moves THROUGH and are input = output, no different than conductivity of electricity(which copper is good there to)

Emissivity has a lot to black body theory, and basically darker objects can absorb/emit IR heat faster than the same material that is shiny. This is irrespective of its conductivity and oxidized copper and iron has close to the same numbers. Even shiny copper is going to disapate heat better than black painted iron because it can conduct the heat from the air inside the pipe faster to the outside than iron can.

In fact one of the reasons that steam pipe is preferred to be iron pipe is it doesn't loose as much heat getting the steam from the boiler to the point of use compared to copper(there are several other reasons why iron is better in steam applications)

 

[nzjkb5]

I live in East Tennessee, and I have about 50' of 3/4" copper line between my 3HP, 30 gallon compressor (built with slopes to drip legs, like designs that I saw multiple places online) and a Norgren filter/regulator. That goes into a 50' hose reel, and I will get lots of water coming out of the exhaust of a grinder after several minutes of continuous use. I keep my drip legs and the filter/regulator drained. I started using one of the Motor Guard "toilet paper roll" filters whenever I am painting or bead blasting to filter out (most of?) the rest of the water. I guess I'll get a refrigerated drier at some point once I get moved into my new shop (we are under contract for a house with a 30x40 detached garage, much better than my current 1-3/4 car garage...)

 

[misterfixit]

If your running mist coolers, you are cooling by adding moisture into the air, you might be better off supplying compressor intake air piped from the outside. Any moisture added to the air by misting will need to be compressed 1700 times to drop out as water, that is wasted compressor power.

By mist cooler, I am talking about a "Fogbuster" type set up for machining. Basically just using about 40psi air to mist a lubricant/coolant on metal while machining to keep the cutters cool and lubed.

 

[sberry]

Only air cooling I have is the pipe, it depends a lot on location and the air source. The air in my shop is rather dry I guess, I had water in the in floor lines and I ran a new steel system overhead and dont even have drip legs before filters, I paint, some really decent size jobs.
My ideal system is one that the comp is not modified in any real way, plug it in to the electric and connect it to the air line. I have 2,,, and a receiver, can actually isolate it all.

 

[nadogail]

My compressor cools the air by radiation from the tank, I do drain the tank almost every time I remember.

The 20 gallon tank has enough surface area that it can cool the small amount of air I need for most jobs.

 

[pcmeiners]

"it does release heat better than iron, nearly 4 times better dependent on the specific alloys involved. This is why many high performance radiators and air/water or water/water heat exchangers do use copper in when compactness is paramount, with or without fins."

You are referring to releasing heat to a liquid, as to radiating heat to air, as in the reference to an aftercooler you are incorrect. Rarely are heat exchanger air to air made from an alloy of copper deviating from a very high level of copper. Copper is a poor radiator unless it is oxidized to a very dark color (or painted to dark color); a chemically oxidized copper, basically oxidized to black is as good as black iron but no better, as any less than very dark oxidized copper it is a very poor radiator of heat. 4 times better, you would be correct if I was referring to heat conduction, copper conducts heat 5 times or more better than black pipe ( iron pipe which is actually low carbon steel)

https://www.spiraxsarco.com/learn-a...ng-principles-and-heat-transfer/heat-transfer



"emissivity has a lot to black body theory, and basically darker objects can absorb/emit IR heat faster than the same material that is shiny. This is irrespective of its conductivity and oxidized copper and iron has close to the same numbers."

Here you are confusing conductivity and the ability to radiate heat. Copper in any form bright or oxidized is great at conducting heat, with emissivity ( radiating ability) which copper is less then black pipe unless chemically treated or painted black. Copper does naturally oxidize with age but this level of oxidation still is not as good as black pipe.

"In fact one of the reasons that steam pipe is preferred to be iron pipe is it doesn't loose as much heat getting the steam from the boiler to the point of use compared to copper(there are several other reasons why iron is better in steam applications) "

In fact, you are getting your facts confused. Main reasons iron pipe was mainly used was
it was cheap, fuel was cheap, it is an excellent radiator of heat, steam pipes radiant loss feeding radiators not considered a loss due to internal use, copper was always expensive.

Lookup in the link below for the comparison of the radiant quality of copper vs steel/iron ...

iron oxidized (as in pipe), cast iron (as in cast iron radiator) and all forms of copper (note, copper pipe as in "oxidized" is copper pipe chemically darkened or oxidized over decades to be close to a very dark color)

https://docplayer.net/23945432-Infrared-thermometer-emissivity-tables.html

 

[sberry]

5 hp,,,,, I forget everyones sizes, this is 30x40,,, is this 2 stage and do you need air both sides of the building etc? There is some tendency here to try to make more rather than good and air doesnt have the same parasitic nature as electric. Tends to be used 1 at a time. In this size building I like 1/2 pipe. Less fittings, 1 size is easier to deal with and is 2x good enough for sandblast with 5, will do 7.5 and will run a 3/4 impact at these distance. 3/4 may slow the velocity a little under the heaviest load,,, impact but thats usually rather short term, not sure how much it would help a blaster but prolly not a lot on this scale.
What is well worth paying attn to here is convenience and ease of use with the modest use of fittings and outlets which are a bit different than hydrants. If a guy needs air in a garage why would he ever want to unhook a hose? Reel or plumbed in whip.

 

[sberry]

Find a best spot for a filter reg, maybe near the reel, plumb to it. Put a service valve ON the compressor followed by hose to a pipe manifold/transport to the filter. If you are really comfy copper thats great, in a simple garage I might be tempted to make most of it steel, so easy to change, seems there is always a better way when you get it done, I still got a couple of those ocd places but I got to let them go due to the fact they are totally irrelevant to the use and only one notices is me.
There are some things I dont care for in one of the recent designs in one of these threads but the major thing I like about it is the layout in that its all accessible and sufficient and on one wall, never needed to cross the place.