Chemical & Process Calculators
Pumps, pipes, and process fundamentals.
- 4–20 mA Loop ScalingConvert loop current to process value and back — with the burden check.PV = PVlo + (I − 4 mA)/16 mA · span
- Thin-Wall Pressure Vessel StressHoop and longitudinal stress σ = Pr/t, with the r/t > 10 validity gate.σ_hoop = P·r/t σ_long = P·r/2t
- Reynolds NumberRe = ρVL/µ with one-click air or water properties, or your own fluid.Re = ρ·V·L / µ = V·L / ν
- Pipe Pressure Drop (Darcy-Weisbach)Friction loss in a round pipe — Swamee-Jain friction factor, automatic laminar branch.ΔP = f·(L/D)·½ρV², f = 0.25/[log₁₀(ε/3.7D + 5.74/Re^0.9)]² (laminar: f = 64/Re)
- Pipe Flow VelocityMean velocity in a round pipe from volumetric flow and diameter.V = Q / A, A = πD²/4
- Bernoulli Pressure ChangeDownstream pressure from an upstream state, two velocities, and an elevation change.p₁ + ½ρv₁² + ρgz₁ = p₂ + ½ρv₂² + ρgz₂
- Orifice FlowFlow through a sharp-edged orifice from a pressure differential — Q = C_d·A·√(2ΔP/ρ).Q = C_d · A · √(2·ΔP/ρ)
- Manning Open-Channel FlowDischarge in a rectangular channel from geometry, slope, and roughness n.Q = (1/n) · A · R^(2/3) · S^(1/2) (SI units; R = A/P)
- Pump Hydraulic & Shaft PowerWater power from flow and head, and the shaft power once efficiency takes its cut.P_hyd = ρ·g·Q·H P_shaft = P_hyd / η
- NPSH AvailableNet positive suction head at the pump inlet — the cavitation margin.NPSHa = (P_surface − P_vapor)/(ρ·g) + z_static − h_friction
- SCFM ⇄ ACFMStandard-to-actual airflow via the ideal-gas temperature and pressure correction.ACFM = SCFM · (P_std / P_act) · (T_act / T_std) (T absolute)
- Water Hammer (Joukowsky)Pressure surge from a sudden velocity change: ΔP = ρ·a·Δv.ΔP = ρ · a · Δv (valid when closure time < 2L/a)
- Pressure ConverterPa, kPa, bar, psi, atm, mmHg, inH₂O, and Torr — one value, every dialect.1 atm = 101,325 Pa 1 psi = 6,894.757 Pa 1 bar = 10⁵ Pa
- Volumetric Flow ConverterL/s, L/min, m³/h, US GPM, and CFM — pump curves to duct specs.1 GPM(US) = 3.785412 L/min 1 CFM = 1.699011 m³/h
- Horizontal Tank VolumePartial-fill volume of a horizontal cylindrical tank from the dip level.A = r²·cos⁻¹((r−h)/r) − (r−h)·√(2rh−h²) V = A·L
- Vertical Tank VolumeFill volume of a vertical cylindrical tank from the level.V = (π/4)·D²·h
- Ideal Gas Law (PV = nRT)Leave any one of P, V, n, T blank — the card solves for it.PV = nRT (R = 8.3145 kPa·L·mol⁻¹·K⁻¹)
- Gas DensityDensity of a gas from pressure and temperature — ρ = PM/RT.ρ = P·M / (R·T)
- Log-Mean Temperature DifferenceLMTD for counterflow or parallel-flow heat exchangers from the four terminal temperatures.LMTD = (ΔT₁ − ΔT₂) / ln(ΔT₁/ΔT₂)
- Heat Exchanger DutyQ = ṁ·cp·ΔT for one stream — the first number of every exchanger problem.Q = ṁ · cp · ΔT
- Heat Conduction (Fourier)Steady heat flow through a flat layer — Q = k·A·ΔT/L.Q = k · A · ΔT / L
- Dilution (C₁V₁ = C₂V₂)Leave any one of the four blank — stock, dose, or final volume solved.C₁ · V₁ = C₂ · V₂
- Pump Head ⇄ PressureConvert a pressure to metres of head for a fluid, plus static lift.H = P / (ρ·g) + z (ρ = SG × 1000 kg/m³)
- Arrhenius Rate RatioHow much faster a reaction runs at a new temperature, from the activation energy.k₂/k₁ = exp[ (Ea/R) · (1/T₁ − 1/T₂) ]
- Half-Life DecayFraction remaining after any elapsed time, from the half-life.N/N₀ = 2^(−t/t½) = e^(−λt), λ = ln 2 / t½
- Dew Point & Absolute HumidityDew point from temperature and relative humidity — Magnus formula, plus g/m³ of water.Td = b·γ / (a − γ), γ = ln(RH/100) + a·T/(b+T) (a = 17.625, b = 243.04)
- Rankine Cycle Efficiency (Ideal)First-cut thermal efficiency, work, and heat for an ideal Rankine steam power cycle from your four state enthalpies.η = wₙₑₜ / qᵢₙ = [(h₁−h₂) − (h₄−h₃)] / (h₁−h₄) , BWR = wₚ / wₜ
- Carnot Efficiency LimitUpper bound on thermal efficiency and refrigeration COP between two reservoir temperatures.η = 1 − T_C / T_H , COP_ref = T_C / (T_H − T_C) , COP_hp = T_H / (T_H − T_C)
- Entropy Change (Ideal Gas)Molar entropy change of an ideal gas between two T–P states using constant specific heat.ΔS = Cp · ln(T₂/T₁) − R · ln(P₂/P₁)
- Moody Friction Factor (Colebrook)Solve the Colebrook-White equation exactly by iteration — the friction factor behind the Moody chart, without squinting at log-log axes.1/√f = −2 · log₁₀( ε/(3.7·D) + 2.51/(Re·√f) ) (laminar: f = 64/Re)
- Cipoletti Weir FlowOpen-channel flow over a trapezoidal (Cipoletti) weir from crest length and head.Q = 1.859 · L · H^(3/2) (SI: Q in m³/s, L and H in m)
- Choked Nozzle (Mach 1 Throat)Choked mass flow, throat conditions, and critical pressure ratio for a converging nozzle running sonic at the throat.ṁ = A*·P₀·√(γ/(R·T₀))·(2/(γ+1))^((γ+1)/(2(γ−1))), P*/P₀ = (2/(γ+1))^(γ/(γ−1)), T*/T₀ = 2/(γ+1)
- Cavitation Number (σ)Dimensionless margin against cavitation for a pump, valve, or hydrofoil operating point.σ = (p − pᵥ) / (½·ρ·V²)
- Two-Phase Pressure Drop (Lockhart-Martinelli)Estimate two-phase frictional ΔP from the single-phase liquid and gas drops using the Martinelli parameter and Chisholm two-phase multiplier.X² = (ΔP_L)/(ΔP_G) , φ_L² = 1 + C/X + 1/X² , ΔP_TP = φ_L²·ΔP_L
- Compressor Polytropic WorkSpecific work, discharge temperature, and gas power for a polytropic compression — ideal-gas basis, any n you specify.w = (n/(n−1)) · (R·T₁/M) · [(P₂/P₁)^((n−1)/n) − 1] T₂ = T₁ · (P₂/P₁)^((n−1)/n)
- Flow-Meter Turndown RatioTurndown (rangeability) from max/min accurate flow, plus a quick accuracy-band check at the low end.Turndown = Q_max / Q_min (both at rated accuracy)
- Valve Sizing (Cv) — LiquidSize a control valve for liquid service: get required Cv from flow, pressure drop, and specific gravity.Cv = Q · √(SG / ΔP) , Kv ≈ 0.865 · Cv (Q in gpm, ΔP in psi)
- Orifice β-Ratio Sizing (ISO 5167)Size a concentric square-edged orifice plate for a target flow — solves bore diameter, β, and differential pressure.qₘ = C·E·ε·(π/4)·d²·√(2·ρ·ΔP) , E = 1/√(1−β⁴) , β = d/D , C = Reader–Harris/Gallagher(β, Re_D)