Heat Exchanger, Coil & Radiator Manufacturing worked example

Thermal Performance Margin with available thermal duty of 63 kW: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop available thermal duty to 63 kW, then walk the calculation through step by step. Calculate thermal performance margin by comparing available duty with required duty for a heat exchanger, coil, radiator, condenser, or evaporator.

The inputs for this scenario

  • Available thermal duty: 63 kW (the input this scenario stresses; the baseline uses 125)
  • Required thermal duty: 100 kW (held at the documented default)
  • Reference thermal duty: 100 kW (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Thermal duty margin = available thermal duty - required thermal duty.
  • Thermal performance margin works out to -37 % at these inputs, and this is the headline figure for the scenario.
  • Thermal duty margin works out to -37 value at these inputs.
  • Available thermal duty works out to 63 value at these inputs.
  • Required thermal duty works out to 100 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where available thermal duty sits at 125 kW and the headline result is 25 %, this scenario comes in 248% below the baseline at -37 %.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to available thermal duty, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It is a single-point duty comparison; it does not model how margin shrinks across the full range of flow rates, ambient temperatures and fouling states the coil will see.

Results at a glance

  • Thermal performance margin: -37 % (headline result)
  • Thermal duty margin: -37 value
  • Available thermal duty: 63 value
  • Required thermal duty: 100 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Thermal Performance Margin calculator, set available thermal duty to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.