Typical values: 2257 (0 bar g), 2100 (~5 bar g), 2000 (~15 bar g)
Temperature Rise (ΔT):0 °C
Total Heat Duty (Q):0 kW
Steam Condensation Rate:0 kg/h
How to Calculate Steam Condensation Rate
Calculating the steam condensation rate is a fundamental task in process engineering, essential for sizing control valves, steam traps, and boiler plants. This calculation determines exactly how much steam is required to achieve a specific heat transfer duty.
When steam releases its energy to heat a process fluid, it undergoes a phase change from vapor to liquid (condensate). The energy released during this phase change is known as the Latent Heat of Evaporation (Enthalpy of Evaporation).
The Core Formulas
The calculation is performed in two steps. First, we determine the total heat energy required by the process fluid, and second, we calculate the mass of steam required to provide that energy.
Step 1: Calculate Heat Duty (Q) Q = ṁ × Cp × ΔT
Where:
ṁ = Mass flow rate of the product being heated (kg/h)
Cp = Specific heat capacity of the fluid (kJ/kg·°C)
ΔT = Temperature rise (Target Temp – Initial Temp) in °C
Q = Total Heat Duty calculated in Step 1 (in kJ/h)
hfg = Specific Enthalpy of Evaporation (Latent Heat) of steam at the operating pressure (kJ/kg)
Why Latent Heat Varies
The latent heat of steam (hfg) changes based on pressure. As steam pressure increases, the amount of latent heat energy per kilogram decreases. This is a critical factor in steam system design: lower pressure steam actually contains more usable heat energy per kg for condensation processes than higher pressure steam, although high pressure is needed for temperature gradients.
Example Calculation
Suppose you need to heat 10,000 kg/h of water from 20°C to 80°C using steam supplied at 5 bar g.
You would therefore need a steam source capable of supplying at least 1,205 kg/h to this heat exchanger.
Common Specific Heat Capacities (Cp)
Substance
Approx Cp (kJ/kg·°C)
Water
4.186
Fuel Oil / Thermal Oil
1.8 – 2.1
Air
1.005
Ethanol
2.44
function calculateSteam() {
// 1. Get input values
var massFlow = document.getElementById('productMassFlow').value;
var specificHeat = document.getElementById('specificHeat').value;
var tempIn = document.getElementById('tempIn').value;
var tempOut = document.getElementById('tempOut').value;
var latentHeat = document.getElementById('latentHeat').value;
var resultsDiv = document.getElementById('results');
// 2. Validate inputs
// We need numbers. If empty, we can't calculate properly, but we'll try to handle gracefully.
// Using parseFloat to ensure we work with numbers
var m = parseFloat(massFlow);
var cp = parseFloat(specificHeat);
var t1 = parseFloat(tempIn);
var t2 = parseFloat(tempOut);
var hfg = parseFloat(latentHeat);
// Check validity
if (isNaN(m) || isNaN(cp) || isNaN(t1) || isNaN(t2) || isNaN(hfg) || hfg === 0) {
// Hide results if data is missing or invalid to avoid NaN display
resultsDiv.style.display = 'none';
return;
}
// 3. Calculation Logic
// Calculate Delta T
var deltaT = t2 – t1;
// If cooling (tempOut < tempIn), deltaT is negative.
// Steam calc usually implies heating. If negative, show 0 or handle logic.
// We will assume absolute load for simplicity, or 0 if heating is not needed.
if (deltaT < 0) {
deltaT = 0;
}
// Calculate Heat Duty Q in kJ/hr
// Q (kJ/h) = m (kg/h) * Cp (kJ/kgC) * dT (C)
var q_kJ_h = m * cp * deltaT;
// Convert Heat Duty to kW for display (1 kW = 3600 kJ/h)
var q_kW = q_kJ_h / 3600;
// Calculate Steam Rate
// Steam (kg/h) = Q (kJ/h) / Latent Heat (kJ/kg)
var steamRate = q_kJ_h / hfg;
// 4. Update Output
document.getElementById('resDeltaT').innerHTML = deltaT.toFixed(1) + ' °C';
// Format numbers with commas for readability
document.getElementById('resHeatDuty').innerHTML = q_kW.toLocaleString('en-US', {maximumFractionDigits: 2}) + ' kW';
document.getElementById('resSteamRate').innerHTML = steamRate.toLocaleString('en-US', {maximumFractionDigits: 1}) + ' kg/h';
// Show results
resultsDiv.style.display = 'block';
}