I'm thinking about attepmting to construct my own vacuum pump to conduct various "experiments" and maybe some sciency stuff. i tried a vacuum cleaner pump and then 2 in series but the vacuum produced was pretty crap only dropped 10kPa i'm looking to make something that can produce a vacuum of >1kPa Whats the best method to go about this.

How hard a vacuum are you going for?

i stated it in the OP so the absolute pressure is >1kPa

Hi.

Use the inlet side of a compressor rescued from a discarded refrigerator.

It really sucks !

Miguel

would the pump be able to handle gases? also, do you have any idea of how big the pressure drop is?

What type of chamber are you using ?. Could you safely heat the air and use a pump then seal it and allow it to cool ?.

the chamber i'm using is a big-ish (20 dm^3) with a thick perspex window that i put in. heating the air inside won't achieve the low pressures i'm looking for. i've managed to get the internal pressure of the box up to around 7 bar (using a high pressure water jet with no leaks so it should be able to withstand a vacuum. (i tried using the water compressor to evacuate the box but it didn't work and damaged the compressor.

Hi.

Yes, gases as refrigerant gases, air, etc. Seen it done to evacuate chambers; and can be improved as shown here:

http://www.sas.org/E-Bulletin/2003-12-12/labNotesAS/body.html

Miguel

its just that all te fridge pumps i've seen use a liquid refrigerant and would be damaged by pumping gases. i got an idea for an initial drop to ~1kPa using chemical reactions so i'll see how it goes.

NOPE !!

The refrigeration compressors -or pumps if called that way- do NOT pump ANY liquids. They handle ONLY gas. The compressed gas becomes liquid AFTER it is cooled in the condenser stage downstrean the compressor outlet.

 

After they absorb heat in the refrigerator evaporator, the refrigerant becomes gas again and that is what enters the compressor inlet.

 

Compressors do not compress liquids. They are almost incompressible.

Miguel

hmm i'll give it a shot as soon as i fix the window on the chamber(it gave at 23 barg)

ok the window is fixed just need to find a pump now.

Ok. i'm close at an absolute pressure of ~15kPa. would putting another pump in series help reduce this or do i need to do something else.