I want to use a piston type compressor having 300 Ltr/Min displacement to generate vacuum of 600mm in 2-3 min. I need calculation procedure for time required to generate vaccum required.
The volumetric flow of a vacuum pump varies considerably depending on the vacuum and is not the same as would be delivered if the same device were working as a pump. If you do a Google search on "vacuum pump curves" you will find quite a few and many manufacturers represented. If you connect a typical vacuum pump to a container the curve of vacuum over time will approach an asymptotic value depending on the pump design and whether or not you also have a leak. Vacuum pumps are widely used on steam condensers to remove non-condensibles. You can find typical curves with Google.
You are trying to use a compressor as a vacuum pump. Ideally, mass entering the suction side of compressor will be equal to the mass leaving at the exit. Taking ‘volume’ instead of ‘mass’ is not so good idea. The pressure difference and resistance to the flow in the flow path decides the mass entering and leaving the compressor. One can imagine a situation where intake is completely closed (not permitting the flow to enter) yet the compressor can run. Then irrespective of the volume displacement of machine, flow will not take place. A compressor can give a constant mass flow rate however, when operating otherwise the mass flow rate will drop with time. The design/build of machine is crucial over here. The important factors are the piston speed, gap between piston and cylinder walls and performance of valves. The volume of container being evacuated will be equally important. Pl. see the attachment.
Same VOLUME but not the same MASS as the density will be decreasing progressively.
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