## Calculating hydrogen gas discharge flow from a pipe opening

## Calculating hydrogen gas discharge flow from a pipe opening

(OP)

I trying to find a quick way to calculate the actual flow rate of hydrogen gas at the discharge point of a 1/8" (0.3175cm) pipe, if the pressure drop is from 74.7psi (515Pa) to 14.7psi (101.4Pa ambient air pressure). The compressed hydrogen gas is at normal room temperature.

## RE: Calculating hydrogen gas discharge flow from a pipe opening

Matt

## RE: Calculating hydrogen gas discharge flow from a pipe opening

The pipe is 10cm long. I am not sure what you mean with converting all the pressure to velocity.

## RE: Calculating hydrogen gas discharge flow from a pipe opening

Base on critical velocity (which you don't want to pass)

The max flow is ~3lb/hr

BTW most of the pressure drop is probably at your valve.

## RE: Calculating hydrogen gas discharge flow from a pipe opening

Doesn't temperature AND pressure play a role if you go from a compresed gas @ 60 psi (gauge) to atmospheric pressure?

## RE: Calculating hydrogen gas discharge flow from a pipe opening

## RE: Calculating hydrogen gas discharge flow from a pipe opening

## RE: Calculating hydrogen gas discharge flow from a pipe opening

M=C*A*{k*ρ*P(2/k+1)^[(k+1)/(k-1)]}^0.5

K(H2)=1.410

Minimum P/Pd required for H2 choked flow = 1.899

M= mass flow rate, kg/s

C = discharge coefficient, dimensionless (~0.62)

A = discharge hole cross-sectional area, m²

k = cp/cv of the gas

cp = specific heat of the gas at constant pressure

cv = specific heat of the gas at constant volume

ρ = real gas density at P and T, kg/m³

P = absolute upstream pressure of the gas, Pa

Pd = absolute downstream gas pressure

good luck