Drawing No. EH–TH–008 // Thermal Engineering & HVAC
Cooling Coil Calculator
Reviewed August 2026
Find sensible, latent and total cooling coil duty from entering and leaving air conditions and airflow rate, and see the resulting sensible heat ratio.
What problem does this solve?
A cooling coil does two jobs at once: it lowers air temperature (sensible cooling) and, if its surface runs below the air's dew point, removes moisture (latent cooling). Coil and chiller selection both depend on knowing the split between these, since sensible and latent capacity aren't interchangeable — a coil sized only for total duty can leave a space cold but humid.
Inputs
Results
Background
Qsensible [W] = 1.2 × airflow [L/s] × (Tin − Tout) [K]. The 1.2 constant comes from standard air density (≈1.2 kg/m³) and specific heat (≈1005 J/kg·K) combined, derived the same way as the sensible-heat shortcut used throughout EngineerHub's HVAC tools.
Qlatent [W] ≈ 3000 × airflow [L/s] × Δw [kg/kg], where Δw is the drop in humidity ratio across the coil. The 3000 constant comes from air density × latent heat of vaporization of water (≈2501 kJ/kg at typical coil temperatures).
SHR = Qsensible / Qtotal. A coil with SHR around 0.7–0.8 is typical for comfort cooling; a lower SHR means more of the load is moisture removal, which usually needs a colder coil surface and more contact time (more rows, lower face velocity) to achieve.
Frequently asked questions
Practical questions about inputs, assumptions and interpretation.
Humidity ratio (mass of water vapor per unit mass of dry air) doesn't change just because temperature changes, unlike relative humidity. Since the coil is physically removing water vapor, humidity ratio is the quantity that directly tracks how much moisture is actually being removed — RH alone can't tell you that without also knowing the temperature at each point.
A low SHR (a lot of latent load relative to sensible) generally requires a colder coil surface temperature and more rows or lower face velocity to get enough contact time for moisture to condense — a coil sized only on total tons without checking SHR can end up leaving a space cold but clammy, because it removes less moisture than the space actually needs.
No — a cooling coil always lowers dry-bulb temperature (or leaves it unchanged in an edge case), so leaving temperature must be at or below entering temperature. The calculator flags this as an invalid input.