How is flash steam fraction calculated?

x = (h1 − hf2) / hfg2, where h1 is condensate enthalpy at upstream conditions (saturated or subcooled), hf2 is saturated liquid enthalpy at downstream pressure, and hfg2 is latent heat at downstream pressure.

What if the condensate is subcooled?

We correct h1 using h1 ≈ hf(P1) − Cp·(Tsat(P1) − Tcond), with Cp ≈ 4.19 kJ/kg·K. If that makes x ≤ 0, no flash steam is predicted.

Condensate Flow & Flash Steam Calculator

Condensate Flow & Flash Steam Calculator | GrowMechanical

Compute flash steam fraction, flash steam rate, and remaining condensate after a pressure drop.

Inputs

Condensate Flow

kg/h

Pressure Mode

Plant gauges are usually in bar g. Absolute = gauge + 1.013.

Upstream Pressure P₁

bar g

Downstream Pressure P₂ (flash tank / atmosphere)

bar g

Condensate Condition

Formula: x = (h₁ − h_f2)/h_fg2, limited to 0–1. Then ṁ_flash = x·ṁ₁ and ṁ_cond,out = (1−x)·ṁ₁.

Results

Results will appear here…

Tip: Ensure P₁ > P₂ so flashing can occur. If subcooled, a small ΔT can eliminate flashing.

Method & Assumptions

Saturation properties via built-in mini steam table (0.5–20 bar(a)) with linear interpolation.
Subcooled h₁ ≈ h_f(P₁) − C_p·(T_sat,P1 − T_cond), with C_p=4.19 kJ/kg·K.
If (h₁ − h_f2) ≤ 0 ⇒ no flash steam (x = 0). If P₁≤P₂, flashing is not possible.

Engineering judgement required. For contractual work, validate with full steam tables or your plant standard.

Inputs

Results

Method & Assumptions

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