| Scenario | Space load | Water load | Process | Pressure | Loss + Safety | Steam demand |
|---|---|---|---|---|---|---|
| Concrete curing tent + hot washdown | 600 m² @ 90 W/m² | 12 L/min, 20→70°C | 25 kW | 5 bar abs | 8% + 10% | ~135 kg/h |
| Small enclosure heating only | 250 m² @ 75 W/m² | 0 | 0 | 3 bar abs | 6% + 10% | ~30 kg/h |
| Water heating skid | 0 | 25 L/min, 15→80°C | 0 | 8 bar abs | 10% + 15% | ~165 kg/h |
- Q_space = Area × HeatLoss ÷ 1000
- Q_water ≈ (Flow ÷ 60) × 4.186 × ΔT
- Q_batch = (m × Cp × ΔT) ÷ time(s)
- Q_total = Q_space + Q_water + Q_process + Q_batch
- Wet steam: h_steam = h_f + x·h_fg
- Superheated (approx.): h_steam ≈ h_g + Cp_steam·(T_sup − T_sat)
- Condensate: h_cond ≈ 4.186·T_cond
- Useful: Δh = h_steam − h_cond
Delivered demand: ṁ = ṁ_base × (1+Loss%) × (1+Safety%)
Generated (incl. blowdown): ṁ_gen = ṁ ÷ (1 − Blowdown%)
- Enter any applicable loads: space heating, water heating, process, or batch heating.
- Select steam pressure and set steam quality or superheat temperature.
- Set condensate temperature, distribution loss, safety factor, and blowdown.
- Enter boiler efficiency and condensate return to estimate water balance.
- Press Calculate Steam Demand to show results above the form.
- Use Download CSV or Download PDF for sharing.
Demand drivers on construction sites
Steam is used for concrete curing tents, temporary space heating, washdown hot water, and process skids. Typical enclosure heat-loss intensities range from 60–120 W/m², while curing setups can run 80–150 W/m² depending on insulation and weather. Curing air temperatures are often held near 50–70°C, and start-up can spike demand. Washdown systems often heat 10–40 L/min with a 30–60°C temperature rise. Single steam lances for thawing can draw 5–20 kW each.
From heat duty to steam flow
The calculator converts all selected loads to kW, then converts kW to steam mass flow using the available heat per kilogram of steam (Δh). For saturated steam, Δh commonly falls around 1,800–2,300 kJ/kg once condensate temperature is considered. Wet steam quality below 1.0 reduces enthalpy and increases kg/h for the same kW. As a quick check, kg/h ≈ kW × 1.6 when Δh is near 2250 kJ/kg.
Practical pressure selection
Many site applications operate between 3 and 10 bar absolute to balance equipment requirements and manageable piping sizes. Higher pressure increases saturation temperature, which can help heat transfer, but it also raises surface temperatures and insulation needs. If you specify superheat, the tool adds an approximate sensible component to steam enthalpy.
Losses, safety margin, and peaks
Real sites rarely deliver steam perfectly to the point of use. Distribution losses from uninsulated piping, vents, and intermittent operation are often 5–15%. A safety margin of 10–20% helps cover warm-up and short peaks. Boiler blowdown, typically 1–5%, increases generated steam versus delivered steam and should be included in capacity checks. Poor insulation, leaking traps, and frequent venting can push losses above 15%.
Boiler sizing, efficiency, and condensate return
After the delivered steam rate is found, the tool estimates boiler thermal output and converts it to boiler horsepower using 1 bhp ≈ 9.81 kW. Typical non‑condensing boiler efficiencies are about 80–90%. Condensate return is often 60–80%; heating 100 kg/h of makeup from 20°C to 90°C adds about 8.1 kW of duty, increasing fuel input.
1) How is steam quality used in the calculation?
Quality represents the dry fraction of wet steam. Lower quality means less usable enthalpy per kilogram, so the required steam flow increases. Use 1.0 for dry saturated steam, or a measured value from your separator or supplier.
2) What condensate temperature should I enter?
Use the temperature of condensate at the return header after traps. Low-pressure returns are often 70–100°C. If you are venting or cooling condensate, enter the lower value to avoid understating steam demand.
3) Does the tool account for flash steam and vent losses?
Not explicitly. If flash steam is vented or heat is lost from open receivers, increase the distribution loss percentage or reduce condensate return to reflect those losses in a simple, transparent way.
4) What steam pressure is best for curing and temporary heating?
Choose the minimum pressure that meets your equipment and heat exchanger needs. Lower pressure reduces saturation temperature and surface risk, while higher pressure can reduce pipe size. Confirm with vendor data and site safety rules.
5) How can I model intermittent loads or duty cycles?
Enter the average load for long runs, then run a second case with peak loads and a higher safety factor. Compare both to ensure the boiler can cover start-up spikes and still operate efficiently at part load.
6) Are the results suitable for final boiler procurement?
Use results for budgeting and preliminary sizing. For procurement, confirm steam properties, pressure drops, trap performance, insulation, and code requirements with a detailed heat and mass balance and a qualified engineer.