Heat Exchanger Thermal Duty Calculator

How the heat exchanger thermal duty calculator works

Signed heat removed in kW = mass flow in kg/s × enthalpy drop in kJ/kg. In constant-specific-heat mode, drop = specific heat × (inlet − outlet temperature). In enthalpy mode, drop is the supplied inlet enthalpy minus outlet enthalpy. A negative duty means heat is added under this convention.

Constant specific heat is a sensible-only approximation without phase change. For another property change use reviewed same-datum enthalpies rather than assuming a liquid heat capacity applies to boiling or condensation. This one-stream rate does not size an exchanger, verify a second-stream energy balance or select transfer coefficients.

Quantities use the stated units and finite bounded inputs. Whole purchases round up under the documented model; cost components round half-up to cents before totals are summed. Undefined ratios stay unavailable. π and logarithms use normal numeric precision. Display rounding does not alter the entered assumptions.

Worked example

2 kg/s with an entered 4 kJ/(kg·K) specific heat cooling from 80 to 50°C removes 240 kW. Raising mass flow to 3 kg/s gives 360 kW. The separate entered-enthalpy mode uses its own reviewed property values.

Sources and assumptions

The source material explains the underlying calculation or pricing structure. Entered prices, costs, schedules and scenario choices are your assumptions; this tool does not obtain supplier quotes or predict actual results.

• Spirax Sarco Heat Transfer