Heat Exchanger, Coil & Radiator Manufacturing worked example

Heat Transfer Area at 61% area yield factor: a worked example

Suppose area yield factor falls to 61%. This page works the full calculation at that level so you can see exactly which result moves and by how much. Estimate total heat transfer surface area for a coil, radiator, condenser, evaporator, oil cooler, or tube bundle using tube count, theoretical area per tube, and an area allowance factor.

The inputs for this scenario

  • Active tubes or passages in the core: 500 count (held at the documented default)
  • Theoretical heat transfer area per tube: 0.8 sq ft / tube (held at the documented default)
  • Area yield factor (good area after fouling/derating): 61 % (the input this scenario stresses; the baseline uses 85)

Working through the calculation

  • The calculation starts from the formula this tool documents: Required gross heat transfer area = active tubes or passages × theoretical area per tube ÷ area yield factor.
  • Required gross heat transfer area works out to 656 sq ft at these inputs, and this is the headline figure for the scenario.
  • Theoretical tube area works out to 400 sq ft at these inputs.
  • Area allowance works out to 256 sq ft at these inputs.
  • Area yield factor works out to 61 % at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where area yield factor sits at 85% and the headline result is 471 sq ft, this scenario comes in 39.34% above the baseline at 656 sq ft.
  • It computes the gross heat transfer area you must build into a core so that, after the area yield factor, the usable surface still meets the theoretical requirement. When the numbers land here, the stressed input is the lever to work; the walkthrough above shows exactly how much each output recovers as it climbs back toward the baseline.

Results at a glance

  • Required gross heat transfer area: 656 sq ft (headline result)
  • Theoretical tube area: 400 sq ft
  • Area allowance: 256 sq ft
  • Area yield factor: 61 %

Run it with your numbers

  • To rerun this with your own numbers, open the live Heat Transfer Area calculator, set area yield factor to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.