mini air compressor 1

[bwilson6561]

For an application, a very small air compressor is needed. The compressor need to supply 80 to 100 psi of air at a flow rate of only 0.1 scfm. The correspond to about 1/10 horsepower.

Lightweight and compactness is important. Are there air compressors on the market with that small of an output?

Thanks

 

[btrueblood]

Yes. And, Google is a powerful tool.

 

[btrueblood]

Oh, and you can try searching on Thomas Register Online, and on Globalspec.

 

[dcasto]

put in the smallest one you can find then add a bottle and switch. Heck put in a big compressor and use bottle air at 1000 psi.

 

[crjones]

Look at Thomas

 

[sreid]

Medo has a nice line of small compressors but not at the pressures you have asked for.

http://www.medousa.com/en/

 

[ClicketyClack]

Try Home Depot or Lowes (assuming you are in the US) or maybe an automotive tire compressor that plugs into a cigarette lighter.

 

[drywall]

Although this may not be precisely what you are asking for you can get small volume high pressure air flows from Haskel Air Driven Gas Boosters. USA phone 818-843-4000.

 

[bwilson6561]

one thing I forgot to mention is the temperature of the output air. Are there compressors out there that doesn't increase the temperature of the air by much?

Thanks

 

[zdas04]

Sure there are, but they also don't compress the gas much. Temperature rise is a function of compression ratios raised to a factor determined by the gas analysis. More compression ratios means more heat and higher temperatures.

David

 

[bwilson6561]

Thanks, what is the mathematical relationship between the temperature rise of air when compressed and other variables such as: final pressure of compressed air, amount of air compressed to that pressure in a given time, etc...

I understand when compressing air, work is done to it which increase the temperature. But most of this work is done to compress the air, just like compressing a spring, which adds to the potential energy of air. But how much is converted into heat?

For the application, I just need a source of 80 psi air with a flow rate of 0.2 scfm. As you see, the flow rate needed is not much. But temperature is important. It cannot be too much higher than ambient.

For the given pressure and flow rate required, is there an easy way to calculate the temperature rise of the output air?

Is the output air hot right from the start or does it get hot only after some time of use...?

Thanks

 

[GregLocock]

I think Mr Clapeyron would like to have a word with you.

http://en.wikipedia.org/wiki/Ideal_gas_law

And bloody Hell, so does Mr Carnot.

http://en.wikipedia.org/wiki/Carnot_cycle

Well, you do have a lot of important people to see, and things to learn.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[bwilson6561]

Since compression heat up the air, expansion will cool it.

Since diving tanks are filled to 3000 psi, doesn't the air gets really cold when it get released? Shouldn't it cause frostbite to diver?

Or does the temperature of the released air actually depend on the rate at which it is released?

In another word, if a gas at a higher pressure is released through an orifice to a lower pressure, is the temperature drop fixed or does it depend on the rate at which it is released (which I'm assuming which depend on the size of the orifice)? Thanks

 

[eliebl]

bwilson6561,

It has been many years since my process courses in university but I will try and remember some of the details. In compression of a gas the reduction in volume results in and increase in pressure and temperature to maintain the same entropy(I believe). This increase in temperature is quickly dissipated when the compressor is cold as the quantity of heat contained in a gas is small. As the compressor heats up (heat capacity of cylinder and piston) more of the heat will remain in the compressed gas.

Upon reduction in pressure (expansion) the gas does indeed cool down. To remain at ambient temperature the gas absorbs heat from the surroundings. In the case of your diving example the quantity of heat in the water easily provides the heat to keep the gas breathed by the diver at the temperature of the surrounding environment. The theoretical temperature drop would be related the the inlet and outlet temperature. From the practical perspective it depends upon the rate at which it is released as the transfer of heat is time dependant so the slower the release the less noticible the pressure drop.

 

[bwilson6561]

eliebl,
you said, "In compression of a gas the reduction in volume results in and increase in pressure and temperature to maintain the same entropy(I believe). This increase in temperature is quickly dissipated when the compressor is cold as the quantity of heat contained in a gas is small. As the compressor heats up (heat capacity of cylinder and piston) more of the heat will remain in the compressed gas.
"

I guess this is what I'm trying to get all along. I'm trying to get a mini air compressor to give me a small flow rate of compressed air. But I want the temperature of the compressed air to be not much higher than ambient.

I wonder if it's possible to design some kind of aftercooler (maybe with coils and a fan) that can quickly cool down any heating due to compression virtually instantaneously.

 

[automatic2]

How about the small CO2 cartridges?

 

[dcasto]

the temperature will be hot like over 500 degrees F. Little units have fan blades on the drive wheels or shieves and the cylinders are finned to help reject the heat energy away from the cylinder and the compressed air. And they normally put a short piece of the discharge line with aluminum fins on it to cool it even more. With all this, the air will come out at say 125 F on an 100 degree F day. If you want the air at nearly ambient, you'll need more cooling or residence time. Thats why all the little compressors have tanks!

 

[ClicketyClack]

Just what the heck is the application? I am curious now.

 

[bwilson6561]

I need a small flow rate of very cold air. Flow rate required is around 0.1 scfm. Temperature of air need to be 80 F below ambient.

The thing need to be portable (by a normal human) and not too heavy. It needs to output cold air for at least 5 minute. It has to be air and not any dangerous gas.

I want to use a vortex tube. I can either power it with a small compressor that will give me the pressure I need (90psi) and flow rate (0.3 scfm), or use a high pressure accumulator tank.

I prefer the small compressor method. But if I need an instaneously source of cold air, I'm not sure how fast it takes the hot compressed air to cool to a point where it will be close to ambient so that the vortex tube can lower it 80 to 100 F more.

Or I can use a small compressor not to power the device directly but simply fill the air accumulator tank so it can be used later. But to get the amount of air I need, the tank need to be filled to I'm thinking at least 500 psi. Are there any cheap and compact compressors out there that can do 500 psi?

Thanks

 

[btrueblood]

And a thermoelectric chip with a small fan to blow air over it won't work?