Psychrometric Chart Calculator Excel File

While printed charts are useful for quick look‑ups, they suffer from low precision, interpolation errors, and inconvenience in iterative calculations. An solves these problems by embedding the governing equations directly into a spreadsheet, allowing rapid, accurate, and repeatable analysis.

| Known 1 | Known 2 | Solve for → | Method | |---------|---------|-------------|--------| | T_db, RH | All others | Direct | | T_db, W | RH | Inverse via ( p_w = (W \cdot P)/(0.62198+W) ) then RH = 100*p_w/p_ws | | T_db, T_wb | W, RH, h, v | Iterative (solve Carrier equation) | | T_db, h | W, RH, T_wb | Quadratic from enthalpy equation | | T_dp, T_db | RH, W | RH = p_ws(T_dp)/p_ws(T_db) *100 |

=0.62198 * B6 / (B2 - B6) Cell B8:

Introduction Psychrometrics—the study of the thermodynamic properties of moist air—is fundamental to HVAC design, building science, agricultural storage, and industrial drying processes. The standard tool for visualizing these relationships is the psychrometric chart, a complex graph with dry-bulb temperature on the x‑axis and humidity ratio on the y‑axis, overlaid with curves for relative humidity, wet‑bulb temperature, specific volume, and enthalpy.

For (pressure in kPa, temperature in K): psychrometric chart calculator excel

[ \ln(p_ws) = \fracC_8T + C_9 + C_10 T + C_11 T^2 + C_12 T^3 + C_13 \ln(T) ]

| Property | Symbol | Typical Units | Description | |----------|--------|---------------|-------------| | Dry‑bulb temperature | T | °C or °F | Ordinary air temperature measured by a standard thermometer | | Wet‑bulb temperature | T w | °C or °F | Temperature recorded by a thermometer with a wet wick; indicates cooling by evaporation | | Dew‑point temperature | T dp | °C or °F | Temperature at which condensation begins for a given moisture content | | Relative humidity | RH | % | Ratio of actual water vapor pressure to saturation pressure at same dry‑bulb | | Humidity ratio (mixing ratio) | W | kg water /kg dry air | Mass of water vapor per mass of dry air | | Enthalpy | h | kJ/kg dry air or Btu/lb dry air | Total heat content (sensible + latent) | | Specific volume | v | m³/kg dry air | Volume per unit mass of dry air | | Vapor pressure | p w | kPa or psi | Partial pressure exerted by water vapor in the mixture | Excel does not have built‑in psychrometric functions. Instead, we must implement empirical correlations from ASHRAE Handbook—Fundamentals. The most important is the saturation vapor pressure over liquid water (Hyland‑Wexler formulation, valid 0–200°C): While printed charts are useful for quick look‑ups,

=1.006*B3 + B7*(2501 + 1.86*B3) Cell B9: