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ExCoil

Chilled water and glycol cooling coils

Chilled water coil selection and rating software

Select cooling coils for air handling units and fan coils. ExCoil marches row by row in counter-cross flow, separates dry and wet surface and reports capacity, sensible heat ratio, leaving air, water temperature rise and pressure drop.

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Calculator included in the free plan · The calculator interface is available in English and Portuguese.

3D model of a chilled water coil with supply and return headers generated by ExCoil

Real application screenshot

What it calculates

  • Row-by-row counter-cross-flow model with water entering at the air-leaving row
  • Dry and wet surface by enthalpy potential, latent load and condensate
  • Water or ethylene glycol mixtures
  • Physical tube count, circuits and passes with water velocity checks
  • Header and connection sizing with commercial pipe diameters
  • Maldistribution and fouling as area derating, not as a change of flow

Results and deliverables

  • Total and sensible capacity, SHR, leaving dry-bulb and wet-bulb
  • Water outlet temperature, velocity and pressure drop
  • Air pressure drop and face velocity
  • PDF report, 2D drawing and DXF (Professional)
  • 3D model with headers, STL and STEP, circuitry and header tabs (Enterprise)

How the chilled water model works

The water-side coefficient uses VDI/Gnielinski with a continuous transition, the air side uses Wang–Chi–Chang with the actual fin thickness, and the energy balance between air and water closes to numerical precision. Header diameters follow the actual flow, so a 40 TR coil does not receive a 19 mm connection.

  • Row-by-row counter-cross-flow marching
  • Wang–Chi–Chang (2000) air side, Schmidt fin efficiency
  • VDI / Gnielinski water side
  • Water pressure drop without double counting passes
  • ASHRAE psychrometric equations

Know the limits

  • Glycol is modelled as ethylene glycol by mass fraction.
  • Drain pan, casing and fan are not part of the calculation.
  • Use the results as engineering estimates; validate before catalogue publication.

Frequently asked questions

Can I select a chilled water coil for an air handling unit?

Yes. Enter airflow, entering air and water conditions, and ExCoil returns capacity, SHR, leaving air and water pressure drop for the selected geometry.

Are glycol mixtures supported?

Yes, ethylene glycol by mass percentage in the chilled and hot water coil modules; the dry cooler module also supports propylene glycol.

How are the headers sized?

From the real water flow and velocity targets, using commercial pipe diameters. The same headers appear in the 2D drawing, the 3D model and the report.

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