Process Manufacturing worked example

Heat Exchanger Duty with process fluid mass flow rate of 9,000 lb / hr: a worked example

This worked example runs the heat exchanger duty numbers for a tougher week than the baseline: process fluid mass flow rate of 9,000 lb / hr instead of the typical 18,000 lb / hr. Estimate heat exchanger duty from flow, heat capacity factor, temperature change, and service factor.

The inputs for this scenario

  • Process fluid mass flow rate: 9,000 lb / hr (the input this scenario stresses; the baseline uses 18,000)
  • Fluid specific heat capacity: 0.92 Btu / lb F (held at the documented default)
  • Inlet-to-outlet temperature change: 45 F (held at the documented default)
  • Fouling and design margin: 1.15 x (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Heat exchanger duty = flow rate × heat capacity factor × temperature change × margin.
  • required heat exchanger duty works out to 428,490 Btu / hr at these inputs, and this is the headline figure for the scenario.
  • clean calculated duty works out to 372,600 value at these inputs.
  • fouling and design margin works out to 1.15 x at these inputs.
  • flow heat capacity product works out to 8,280 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where process fluid mass flow rate sits at 18,000 lb / hr and the headline result is 856,980 Btu / hr, this scenario comes in 50% below the baseline at 428,490 Btu / hr.
  • Use it when sizing or rating a heat exchanger, specifying utility loads, or checking an existing unit against a new service. A result at this level usually justifies acting on the stressed input before touching anything else, because every other figure in the table is downstream of it.

Results at a glance

  • required heat exchanger duty: 428,490 Btu / hr (headline result)
  • clean calculated duty: 372,600 value
  • fouling and design margin: 1.15 x
  • flow heat capacity product: 8,280 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Heat Exchanger Duty calculator, set process fluid mass flow rate to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.