2 replies to this topic

[Sarvesh_79_CHEMEO]

Hello ,

   I have got a problem with an ejector system. I have an ejector whose capacity is to produce 720 mmHg vacuum in 20 mins. But, I require only 50 mmHg vacuum.  Therefore, I am adding a nitrogen line to the vacuum line. What I want to know is how much Nitrogen flow rate I do require in the nitrogen line. 

I have the following data.

Diameter of vacuum line: 100 mm

Diameter of nitrogen line: 25 mm

Pressure of nitrogen in the nitrogen line: 2kg/cm2

 

I tired to use bernoullli's equation. But I am not getting good numbers.

Please help.

 

Sarvesh Chitodkar

[katmar]

Without having the full specification of the ejector this is an impossible question to answer.  Is it necessary to use nitrogen rather than air?  Because you are working below atmospheric pressure you do not need a pressurised gas - you can simply draw atmopheric air into the system through a control valve.

 

When using liquid ring pumps this method of controlling the vacuum by drawing air (or other gas) into the pump to provide the rated capacity is the right way to go.  If you simply throttle the suction line to the liquid ring pump you can cause cavitation and mechanical damage.  But with an ejector you can limit the vacuum by throttling the suction line quite safely.  You could consider this rather than bleeding in nitrogen if air is not a viable alternative.

[Bobby Strain]

Your pressure terminology is strange and confusing to me. We usually describe subatmospheric pressure in absolute terms. Not relative to atmospheric pressure.

 

Bobby