Orifice Sizing

Gas Properties

Relative density SG (air = 1)

CO2 mole fraction

%

N2 mole fraction

%

Gas input mode

Compressibility factor Z

Isentropic exponent κ

Dynamic viscosity μ

Pa·s

Pressure tapping

Operating Conditions

Temperature

°C

Gauge pressure Pg

MPa

Atmospheric pressure Patm

MPa

Standard temperature

°C

Standard pressure

kPa

Pipe inner diameter D

mm

Required Flow

Minimum flow Qmin

standard conditions, m³/h

Maximum flow Qmax

standard conditions, m³/h

Differential Pressure Range

ΔP at Qmin (typically 10 % of range)

kPa

ΔP at Qmax (typically 90 % of range)

kPa

Straight Pipe Lengths

Minimum straight lengths per ISO 5167-2:2003, Table 3 (upstream) and Table 4 (downstream).

Upstream fitting

Actual upstream straight length

×D

Actual downstream straight length

×D

Measurement Uncertainty

Combined relative uncertainty per ISO 5167-1:2003 §8.3.

Discharge coefficient C

%

Pipe diameter D

%

Orifice diameter d

%

Differential pressure ΔP

%

Density at operating conditions

%

Results

Standard practice: choose d so that ΔP(Qmax) ≈ ΔPmax and ΔP(Qmin) ≥ ΔPmin, keeping β = 0.10…0.75.

Orifice Characteristic (at ΔPmax)

Standard-condition flow against orifice diameter at the maximum differential pressure.

Orifice Sizing

Gas Properties

Operating Conditions

Required Flow

Differential Pressure Range

Straight Pipe Lengths

Measurement Uncertainty

Results

Permanent Pressure Loss

Measurement Uncertainty

Orifice Characteristic (at ΔPmax)