Thermal Desalination Calculators

4 Calculators MED & MSF Metric Primary Client-Side — No Data Sent
Calculator 1 of 4

Gained Output Ratio (GOR)

GOR is the primary thermal efficiency metric for MED and MSF desalination systems — the kg of distillate produced per kg of steam consumed. Higher GOR means greater efficiency.

Distillate input unit:
m³/day — will convert to kg/hr automatically
kg/hr
bar — used for latent heat lookup (default 1.0 bar = 100°C)
Results
Unit conversion (if m³/day input): ṁ_distillate (kg/hr) = Q_distillate (m³/day) × 1000 / 24 GOR: GOR = ṁ_distillate (kg/hr) / ṁ_steam (kg/hr) Latent heat interpolation (saturation): 0.5 bar → 2305 kJ/kg | 1.0 bar → 2257 kJ/kg | 1.5 bar → 2226 kJ/kg 2.0 bar → 2201 kJ/kg | 3.0 bar → 2163 kJ/kg | 5.0 bar → 2108 kJ/kg | 10.0 bar → 2015 kJ/kg Steam per m³ distillate: Steam per m³ = 1000 / GOR (kg/m³) Thermal energy consumption: E_th (kJ/kg) = h_fg / GOR E_th (kWh/m³) = E_th (kJ/kg) / 3.6
Calculator 2 of 4

Performance Ratio (PR)

PR is the IDA-standard thermal efficiency metric, normalized to the latent heat at 100°C / 1 atm (2326 kJ/kg). PR equals GOR when steam is at 100°C; they diverge when steam conditions differ.

Distillate input unit:
m³/day
kg/hr
bar (affects latent heat and PR vs GOR difference)
Results
IDA reference latent heat: h_ref = 2326 kJ/kg (latent heat at 100°C, 1 atm) Performance Ratio: PR = GOR × (h_fg_operating / h_ref) PR = GOR × (h_fg_operating / 2326) When steam is at 1 atm (1.013 bar), h_fg ≈ 2257 kJ/kg, so PR ≈ GOR × 0.97 Thermal energy input: Q_steam (kW) = ṁ_steam (kg/hr) × h_fg (kJ/kg) / 3600 IDA benchmarks: PR < 6: Below industry average PR 8–12: Typical modern plant PR > 12: High-performance
Calculator 3 of 4

Brine Concentration Factor

Calculate reject brine TDS and water recovery from thermal desalination. Enter feed conditions plus either distillate or brine discharge flow — the third stream is calculated from the mass balance.

Specify:
Feed TDS unit:
mg/L — typical seawater ≈ 35,000 mg/L
m³/day
m³/day
Results
Mass balance: Q_feed = Q_distillate + Q_brine Recovery: R (%) = Q_distillate / Q_feed × 100 Concentration Factor: CF = Q_feed / Q_brine = 1 / (1 − R/100) Brine TDS: TDS_brine = TDS_feed × CF Density flag: ρ_brine > 1.04 g/cm³ when TDS > ~60 g/L — check pump sizing Reference case: Seawater: 35 ppt feed, 40% recovery → brine ~58 ppt, CF ≈ 1.67
Calculator 4 of 4

Top Brine Temperature (TBT) Scaling Risk

Assess CaCO₃ (carbonate) and CaSO₄ (anhydrite) scaling risk at the specified Top Brine Temperature, based on concentrated ion activities and temperature-dependent solubility products.

°C (typical MSF: 90–120°C; MED: 60–75°C)
mg/L — typical seawater ≈ 408 mg/L
mg/L as HCO₃⁻ — typical seawater ≈ 141 mg/L
mg/L — typical seawater ≈ 2,700 mg/L
× (typical last effect CF: 1.4–2.0)
Results
CaCO₃ solubility product (inverse solubility): Ksp_CaCO₃(T) = 3.36×10⁻⁹ × exp(−0.0115 × (T − 25)) [mol²/L²] Ion product (CaCO₃): Ca_c = Ca_feed × CF; Alk_c = HCO₃_feed × CF Ca_mol = Ca_c / 40,080; HCO₃_mol = Alk_c / 61,020 CO₃_mol = HCO₃_mol × 10^(pH − pK₂) where pH=8.0, pK₂=10.0 IP_CaCO₃ = Ca_mol × CO₃_mol SI_CaCO₃ = log₁₀(IP / Ksp_CaCO₃) CaSO₄ (anhydrite) solubility product: Ksp_anhydrite(T) = 4.93×10⁻⁵ × exp(−0.02 × (T − 25)) [mol²/L²] SO₄_mol = SO₄_feed × CF / 96,060 IP_CaSO₄ = Ca_mol × SO₄_mol SI_CaSO₄ = log₁₀(IP / Ksp_anhydrite) Industry thresholds (no antiscalant): MSF: safe to ≤90°C | MED: safe to ≤65°C With antiscalant: MSF: safe to ≤120°C | MED: safe to ≤90°C