Hydrogen Flow Rate Calculator

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Hydrogen Flow Rate Calculator (Electrolysis)

Calculate H₂ production rate based on Faraday's Law

Mass Flow Rate (kg/hr): 0.00
Volumetric Flow Rate (Nm³/hr): 0.00
Standard Flow Rate (SCFH): 0.00
Daily Production (kg/day): 0.00

Understanding Hydrogen Flow Rate Calculation

In the field of hydrogen production, specifically water electrolysis, calculating the flow rate is essential for sizing storage tanks, compressors, and downstream piping. The production of hydrogen is directly proportional to the electrical current passing through the electrolytic cells.

The Formula: Faraday's First Law

The theoretical production of hydrogen is determined by Faraday's Law of Electrolysis. The formula used in this calculator is:

ṁ = (I × N × η × M) / (z × F)

  • I: Current in Amperes (A)
  • N: Number of cells in the electrolyzer stack
  • η: Faraday Efficiency (typically 90-98%)
  • M: Molar mass of H₂ (approx. 2.016 g/mol)
  • z: Valency of H₂ (2 electrons per molecule)
  • F: Faraday Constant (96,485.33 C/mol)

Common Hydrogen Units Explained

Unit Description
kg/hr Mass flow rate of hydrogen per hour. Most common for industrial sizing.
Nm³/hr Normal cubic meters per hour (measured at 0°C and 1.01325 bar).
SCFH Standard Cubic Feet per Hour (measured at 60°F and 14.7 psia).

Example Calculation

Suppose you have an electrolyzer stack with 120 cells operating at 600 Amperes with a 95% Faraday efficiency.

First, we calculate the molar flow: (600 A × 120 cells × 0.95) / (2 × 96485) = 0.3544 mol/s of H₂.

Converting this to mass: 0.3544 mol/s × 2.016 g/mol = 0.7145 g/s, which equals 2.57 kg/hr.

function calculateH2Flow() { var I = parseFloat(document.getElementById('stackCurrent').value); var N = parseFloat(document.getElementById('cellCount').value); var efficiency = parseFloat(document.getElementById('faradayEfficiency').value) / 100; var hours = parseFloat(document.getElementById('operatingHours').value); if (isNaN(I) || isNaN(N) || isNaN(efficiency) || isNaN(hours)) { alert("Please enter valid numerical values."); return; } // Constants var F = 96485.33; // Faraday Constant C/mol var z = 2; // Electrons for H2 var molarMassH2 = 2.01588; // g/mol var densityNm3 = 0.08988; // kg/Nm3 at 0C, 1.013 bar var nm3ToScf = 37.324; // Conversion factor Nm3 to SCF (Standard Cubic Feet) // Calculation logic // Molar flow rate in mol/s var molarFlowRate = (I * N * efficiency) / (z * F); // Mass flow rate in g/s then kg/hr var massFlowGramPerSec = molarFlowRate * molarMassH2; var massFlowKgHr = (massFlowGramPerSec * 3600) / 1000; // Volumetric flow rate Nm3/hr var volFlowNm3Hr = massFlowKgHr / densityNm3; // Volumetric flow rate SCFH var volFlowSCFH = volFlowNm3Hr * nm3ToScf; // Daily production var dailyProduction = massFlowKgHr * hours; // Display results document.getElementById('kgHrResult').innerText = massFlowKgHr.toFixed(4); document.getElementById('nm3HrResult').innerText = volFlowNm3Hr.toFixed(3); document.getElementById('scfhResult').innerText = volFlowSCFH.toFixed(2); document.getElementById('kgDayResult').innerText = dailyProduction.toFixed(2); document.getElementById('resultsArea').style.display = 'block'; }

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