Compressed air dryer question
 

"Ignoramus25888" wrote in message
...
I bought a used compressed air dryer for $10 last weekend. Tried it
and found that it was working, since the outgoing air was cold and the
release valve was functioning. My question is about capacity. This
dryer uses about 264 watts of power, according to my wattmeter
(kill-a-watt). Is that enough for a 3 honest HP compressor. Thanks.

i

1 HP/hour == 745.7 watt/hour

But, um... how many watts does it take to dry air?? I dunno.

LLoyd

True air drying reqs an air-conditioning type compressor, I believe.
246 watts seems kind of low, but is possible. Might not use a compressor.
Cold outgoing air may not be a sure-fire test, what with the joule effect of
expanding gases'n'****....

Proly the unit should be rated ito cfm at some psi..

The real test is if any condensate is produced.
----------------------------
Mr. P.V.'d
formerly Droll Troll
"Lloyd E. Sponenburgh" wrote in message
. ..

"Ignoramus25888" wrote in message
...
I bought a used compressed air dryer for $10 last weekend. Tried it
and found that it was working, since the outgoing air was cold and the
release valve was functioning. My question is about capacity. This
dryer uses about 264 watts of power, according to my wattmeter
(kill-a-watt). Is that enough for a 3 honest HP compressor. Thanks.

i

1 HP/hour == 745.7 watt/hour

But, um... how many watts does it take to dry air?? I dunno.

LLoyd

Ignoramus25888 writes:

I bought a used compressed air dryer for $10 last weekend. Tried it
and found that it was working, since the outgoing air was cold and the
release valve was functioning. My question is about capacity. This
dryer uses about 264 watts of power, according to my wattmeter
(kill-a-watt). Is that enough for a 3 honest HP compressor.

Could be. The smallest sizes are designed for 6 or 10 cfm, and 3 HP
would be about 10 or 12 cfm. My little Hankison unit runs at about 200
watts and is rated for 10 cfm. I've measured the relative humidity of
the output air at 10 percent, with hot 100 percent moist air input.

Cold outgoing air is not a good performance indicator. Many designs
efficiently reheat the air with the hot side of the heat pump.

To properly test performance, you must measure the relative humidity of
the output air. Get a wet-bulb/dry-bulb psychrometer and measure the
relative humidity of the output air by directing a stream of exhausted
compressed air over the bulbs of the thermometers. Or improvise your
own wet-bulb and dry-bulb thermometers and use my psychrometric chart:

http://www.truetex.com/psychrometric_chart.htm

Lloyd E. Sponenburgh writes:

1 HP/hour == 745.7 watt/hour

What's per-hours got to do with it?

But, um... how many watts does it take to dry air?? I dunno.

This is a thermodynamic problem with various factors involved.

Practical small units require about 20 watts per cfm.

Richard J Kinch wrote:
Lloyd E. Sponenburgh writes:


1 HP/hour == 745.7 watt/hour


What's per-hours got to do with it?


But, um... how many watts does it take to dry air?? I dunno.


It depends on how humid the air is going into the compressor.
Around here (St. Louis) it can get pretty wet at times, and the
compressor tank drain can really dump a lot of water from a short
run of the compressor. I have a small unit that doesn't have a
CFM rating, but I think it is good for maybe up to 5 CFM or so.
It has a 1/8 Hp refrigerator compressor on it, and a Freon codenser
coil identical to what would be on a small dehumidifier.
It does an excellent job with a 3-5 CFM continuous load on
the compressor.

Jon

Jon Elson writes:

It depends on how humid the air is going into the compressor.

No, not if it reaches the dewpoint, which is almost always the case. The
compressed air is at 100 pct RH. That's why you have liquid accumulating
in the tank.

Air dryers refrigerate the air, knock out the moisture, then heat exchange
the outgoing air with the incoming air to precool it and minimise the energy
needed to run it. Outgoing air should be cooler than incoming air but not
COLD as this would indicate that the heat exchanger was probably fouled with
old oil from a previous compressor. It might be able to clean it with hot
water and detergent if this is a problem..


Tom
"Proctologically Violated©®" wrote in message
...
True air drying reqs an air-conditioning type compressor, I believe.
246 watts seems kind of low, but is possible. Might not use a compressor.
Cold outgoing air may not be a sure-fire test, what with the joule effect
of
expanding gases'n'****....

Proly the unit should be rated ito cfm at some psi..

The real test is if any condensate is produced.
----------------------------
Mr. P.V.'d
formerly Droll Troll
"Lloyd E. Sponenburgh" wrote in
message
. ..

"Ignoramus25888" wrote in message
...
I bought a used compressed air dryer for $10 last weekend. Tried it
and found that it was working, since the outgoing air was cold and the
release valve was functioning. My question is about capacity. This
dryer uses about 264 watts of power, according to my wattmeter
(kill-a-watt). Is that enough for a 3 honest HP compressor. Thanks.

i

1 HP/hour == 745.7 watt/hour

But, um... how many watts does it take to dry air?? I dunno.

LLoyd