A hydraulic air compressor uses falling water to carry air into a chamber where the air separates under pressure. Use this calculator to compare an entered static water head with pressure and an ideal isothermal gas-volume ratio. These values do not determine air delivery rate or pressure under flow.
Hydraulic Air Compressor Interactive Calculator
Explore a static water-head pressure scenario and ideal gas pressure/volume ratios from an entered atmospheric pressure.
Equation Used
- Entered H is net static vertical water head.
- Uniform user-entered water pressure gradient and atmospheric pressure.
- Ideal gas with constant amount and temperature for the volume-ratio tile.
- No entrainment, dissolution, slip, heat transfer, water/gas flow, friction, acceleration, separation, delivery piping, efficiency, capacity, structure or safety model.
The entered head must be the net vertical water-column difference that actually supports the pressure, not simply shaft or separator depth. Real flowing systems have losses and gas-water interactions not represented here.
Static head and an ideal gas comparison
A static liquid column of net vertical head H produces gauge pressure Pg=H/k when k is entered in feet per psi. Absolute pressure is Patm+Pg.
For a fixed amount of ideal gas compressed isothermally from Patm to Pabs, Boyle's law gives V2/V1=Patm/Pabs. The animation is qualitative and is not a trompe flow simulation.
Use as a preliminary physics check
The identities can compare static head, pressure and an ideal gas-volume ratio. They cannot choose a site, determine delivery pressure under flow, size a downcomer or separator, or estimate air output.
Pressure basis matters
Hydrostatic head produces gauge pressure, while gas compression ratios require absolute pressure. The calculator therefore adds entered atmospheric pressure before taking the ratio. The ideal volume result assumes constant temperature and gas quantity.
Worked pressure example
At H=200 ft and k=2.31 ft/psi, static gauge pressure is about 86.58 psi. With Patm=14.7 psi, absolute pressure is 101.28 psia, the ideal pressure ratio is 6.890 and ideal isothermal gas volume is 14.51% of its atmospheric-pressure volume.
Scope and limitations
Real hydraulic air compression depends on available head and water flow, intake geometry and entrainment, void fraction, bubble size and slip, dissolution, heat exchange, downcomer friction, separator level and geometry, riser and delivery losses, surge behavior, structural/geotechnical design, water rights and environmental constraints.
Questions
Is shaft depth always the pressure head?
No. Use the actual net static water-level difference after accounting for the system layout.
Is the volume ratio an actual bubble-size prediction?
No. It is an ideal isothermal gas-volume ratio.
Does the result give compressor CFM?
No. Water flow and air entrainment are absent.
Historical source and calculation basis
Hiscox, entries 634 and 636, describes the trompe and Taylor hydraulic air compressor. Falling water carries air into a separating chamber, while the water outlet arrangement supports the air pressure.
The calculator uses the static relation Pg = H/k and absolute pressure Pabs = Patm + Pg. The volume comparison applies Boyle’s law to a fixed amount of ideal gas at constant temperature. Flow rate, air entrainment and hydraulic losses require a separate model.
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