Hydrogen compression to storage vessel

[simple70]

Hello all,
I want to ask if there is any rule of thumb for selecting discharge pressure of hydrogen gas compressor used to fill a hydrogen storage vessel, in relation with the storage vessel maximum pressure.

The compressor is reciprocating (piston), although the quantity compressed is constant, when the vessel is empty the compressor works against lower pressure, as the vessel fills the pressure difference between the compressor discharge and the vessel decreases.

Will the rate of filling decrease in this case ? and should we always keep a specific difference between the comressor pressure and the vessel pressure to keep good filling rate ?

Any comments ?

 

[zdas04]

A reciprocating compressor is a positive displacement machine. Assuming that the suction valve opens every stroke at about the same place, every stroke will compress the same amount of gas. Internal pressure will always build to discharge galley pressure plus cracking pressure of the discharge valve. [If you get into a situation where suction pressure is higher than discharge pressure then the gas will blow through the cylinder, but I don't think that this is what you're talking about].

Recips are not hurt by increasing discharge pressure up to the point where the ratios get too high and the machine goes into rod load or high temperature shut down. A multi-stage recip can get into trouble early since blow through in the first stage can result in rod load in the second stage.

David