Open-Cycle OTEC Flash Evaporator (2D)

Ocean Water Temperature

Warm surface intake T_warm 28 °C

Cold deep-water intake T_cold 6 °C

Flash Chamber Pressure

Absolute pressure P_chamber 2.32 kPa

Warm-water flow rate ṁ_w 200 kg/s

The engine never lets you pick T_sat directly — you pull a pressure, and T_sat is derived from it by inverting the Antoine vapor-pressure equation, exactly like a real vacuum gauge on a flash vessel.

Antoine inversion self-check pending…

Live Output

Saturation T_sat—

Flash fraction x—

Net power P_net—

Fresh water yield—

How it works

A real flash chamber is not told its own saturation temperature — an operator sets a pressure with a vacuum pump, and the water finds its own boiling point at that pressure. This engine reproduces that: it computes the saturation vapor pressure of water from temperature with the Antoine equation, then numerically inverts it to recover T_sat from the pressure you dial in.

Antoine (1-100 °C, P in mmHg):
  log10(P) = A - B / (C + T),  A=8.07131, B=1730.63, C=233.426
  T_sat = B / (A - log10(P_mmHg)) - C

Flash fraction:  x = c_p(T_warm - T_sat) / h_fg(T_sat)
Turbine work:    w_t = eta_t . h_fg(T_sat) . (T_sat - T_cond) / T_sat[K]
Turbine power:   P_turbine = x . m_w . w_t
Net power:       P_net = P_turbine - P_pump(m_w, T_warm - T_sat)

The chart below sweeps the full pressure range at the current T_warm, drawing the T_sat(P) curve the closed-form inversion produces — the same curve the flash fraction is read off. On load the engine also runs an independent bisection solver against the forward Antoine formula and checks it agrees with the closed-form inversion to within 10⁻⁶ °C (see the green badge above).

x is small on purpose — with only a ~20 °C surface-to-deep gradient, real OTEC flash fractions sit around 0.5–1.5%; bubble/steam density in the animation is scaled up for visibility, but the flash-fraction readout is the exact computed value.
Pressure, not T_sat, is the real control knob — a deeper vacuum (lower pressure) yields a lower T_sat, flashing more water, but it also shrinks (T_sat − T_cond), the turbine's driving temperature drop, while pump power keeps climbing — net power peaks at an intermediate vacuum.
Turbine efficiency is fixed at η_t = 0.75 and the condenser approach at T_cold + 2 °C, matching the 3D open-cycle OTEC companion simulation's engineering assumptions.

Warm intake water Flashed steam Condensed fresh water