Calculators · Performance Toolkit
Heat Duty
Calculates absorbed heat duty from process fluid flow rate, temperature rise, and specific heat. Also derives fired duty based on an entered thermal efficiency, and distributes duty across passes.
Inputs
Flow Rate Units
Process Fluid Flow Rate
kg/hr
Total flow through all passes combined.
Enter a value greater than zero.
Inlet Temperature
°C
Enter a value between −50 and 800 °C
Outlet Temperature
°C
Coil outlet temperature (COT).
Must be greater than inlet temperature.
Specific Heat Cp
kJ/kg·°C
Default 2.1 — typical for light gas oil / vacuum gas oil fractions.
Enter a value between 0.5 and 10 kJ/kg·°C
Number of Passes
Duty per pass assumes equal flow and heat distribution across all passes.
Enter a whole number between 1 and 16.
Thermal Efficiency
%
Used to back-calculate fired duty. Typical range: 80–92 %.
Enter a value between 30 and 99 %.
Results
Enter inputs and press
Calculate to see results
Calculate to see results
Calculation method:
Absorbed heat duty is calculated as
Q = ṁ × Cp × ΔT, where ṁ is mass flow rate (kg/s),
Cp is mean specific heat (kJ/kg·°C), and ΔT is the temperature rise across the coil.
Fired duty is back-calculated as Qfired = Qabsorbed / η,
where η is the entered thermal efficiency fraction.
Unit conversion: 1 MW = 3.41214 MMBtu/hr; lb/hr inputs are converted to kg/hr at 0.453592 kg/lb.
Duty per pass assumes equal flow distribution and equal heat absorption across all passes.
⚠ Results are indicative only, based on simplified engineering relationships. Not suitable for use in engineering design, heat exchanger sizing, regulatory submissions, or safety-critical decisions. Verify all values with a qualified process engineer using site-specific stream data and rigorous simulation.