Ammonia (NH3) Properties Calculator

Two-Phase Lever Rule (state from quality)

v = v_f + x · (v_g − v_f) | h = h_f + x · h_fg | s = s_f + x · s_fg | u = u_f + x · u_fg

Variables: x = quality, mass fraction of saturated vapour (dimensionless, 0 to 1); v = mixture specific volume (m³/kg); v_f, v_g = saturated-liquid and saturated-vapour specific volume (m³/kg); h = specific enthalpy (kJ/kg); h_f = saturated-liquid enthalpy (kJ/kg); h_fg = enthalpy of vaporisation (kJ/kg); s = specific entropy (kJ/(kg·K)); s_f = saturated-liquid entropy (kJ/(kg·K)); s_fg = entropy of vaporisation (kJ/(kg·K)); u = specific internal energy (kJ/kg); u_f = saturated-liquid internal energy (kJ/kg); u_fg = internal energy of vaporisation (kJ/kg). All f, g and fg values are read from this calculator's built-in saturation table, whose enthalpy datum places h_f = 0 near −44.4 °C, so only differences in h, u and s are meaningful. Source: Cengel & Boles, Thermodynamics: An Engineering Approach, 8th ed., Ch. 3 (saturated liquid–vapour mixture, quality). Property values are this calculator's built-in table; verify against NIST REFPROP or the NIST Chemistry WebBook before design use.

Quality Back-Calculated from a Measured Property

x = (v − v_f) / (v_g − v_f) = (h − h_f) / h_fg = (s − s_f) / s_fg = (u − u_f) / u_fg

Variables: x = quality (dimensionless, 0 to 1); v = measured specific volume (m³/kg); v_f, v_g = saturated-liquid and saturated-vapour specific volume (m³/kg); h = measured specific enthalpy (kJ/kg); h_f = saturated-liquid enthalpy (kJ/kg); h_fg = enthalpy of vaporisation (kJ/kg); s = measured specific entropy (kJ/(kg·K)); s_f, s_fg = saturated-liquid and vaporisation entropy (kJ/(kg·K)); u = measured specific internal energy (kJ/kg); u_f, u_fg = saturated-liquid and vaporisation internal energy (kJ/kg). The tool uses the tabulated fg columns as the denominator for h, s and u, and (v_g − v_f) for specific volume. Caution: the four routes give the same x only when the underlying table obeys s_fg = h_fg / T_sat (T_sat in K); this calculator's tabulated s_fg departs from h_fg / T_sat by roughly 5 % near −33 °C, 7 % at 0 °C and over 10 % above 40 °C, so entropy results should be cross-checked against a reference table before being used for compressor or turbine work. Source: Moran, Shapiro, Boettner & Bailey, Fundamentals of Engineering Thermodynamics, 8th ed., Ch. 3 (fixing a two-phase state; quality from an intensive property). Consistency requirement s_fg = h_fg / T_sat: Cengel & Boles, 8th ed., Ch. 12 (Clapeyron equation, property relations).

Linear Saturation-Table Interpolation and Inverse Saturation Temperature

Y(T) = Y_i + [(T − T_i) / (T_(i+1) − T_i)] · (Y_(i+1) − Y_i) | T_sat(P) = T_i + [(P − P_i) / (P_(i+1) − P_i)] · (T_(i+1) − T_i)

Variables: T = queried saturation temperature (°C; table spans −60 to 132.25 °C in 5 °C steps to 100 °C, then rows at 110 and 132.25 °C); T_i, T_(i+1) = bracketing tabulated temperatures (°C); P = queried saturation pressure (kPa; table spans 21.9 to 11333 kPa); P_i, P_(i+1) = tabulated saturation pressures (kPa); Y = any saturation column — P_sat (kPa), v_f, v_g (m³/kg), h_f, h_fg, h_g, u_f, u_fg, u_g (kJ/kg), s_f, s_fg, s_g (kJ/(kg·K)); Y_i, Y_(i+1) = tabulated values (same units as Y); T_sat = saturation temperature (°C). Two behaviours to note: a queried T outside −60 to 132.25 °C returns no state, but a queried P outside 21.9 to 11333 kPa is silently clamped to the nearest endpoint rather than rejected, so an out-of-range pressure returns an endpoint state without warning; and because P_sat is exponential in T, linear interpolation is only accurate across the 5 °C rows — the 100 to 110 to 132.25 °C intervals are coarse and the critical row (v_f = v_g = 0.004255 m³/kg, h_fg = 0) makes the last interval unreliable. Source: Cengel & Boles, Thermodynamics: An Engineering Approach, 8th ed., Ch. 3 (linear interpolation in property tables; saturation temperature–pressure correspondence).

Bilinear (T then P) Interpolation in the Superheated Ammonia Tables

φ(P, T) = φ_lo(T) + [(P − P_lo) / (P_hi − P_lo)] · [φ_hi(T) − φ_lo(T)]

Variables: φ = interpolated superheated property — v (m³/kg), h (kJ/kg), s (kJ/(kg·K)) or u (kJ/kg); P = queried pressure (kPa); P_lo, P_hi = bracketing tabulated isobars (kPa; the set is 50, 100, 200, 400, 600, 800, 1000, 1500, 2000 kPa); T = queried temperature (°C); φ_lo(T), φ_hi(T) = the property linearly interpolated in T within the P_lo and P_hi isobar tables (same units as φ). Each isobar is tabulated over its own temperature range, all ending at 200 °C but beginning at −20 °C (50 and 100 kPa), −15 °C (200 kPa), 0 °C (400 kPa), 15 °C (600 kPa), 20 °C (800 kPa), 25 °C (1000 kPa), 40 °C (1500 kPa) and 50 °C (2000 kPa). Queries outside these bounds, or pressures above 2000 kPa or below 50 kPa, are clamped to the nearest tabulated endpoint rather than extrapolated, so out-of-range inputs return an endpoint value with no warning. Source: Cengel & Boles, Thermodynamics: An Engineering Approach, 8th ed., Ch. 3 (double interpolation in superheated-vapour tables).