Psychrometric Chart Excel ^new^ May 2026

| Cell | Value | |------|-------| | A1 | 30 (T_db °C) | | A2 | 50 (RH %) | | A3 | =610.78*EXP(17.27*A1/(A1+237.3)) → 4245 Pa | | A4 | =A2/100 * A3 → 2122.5 Pa | | A5 | =0.62198*A4/(101325-A4) → 0.0131 kg/kg | | A6 | =1.006*A1 + A5*(2501+1.86*A1) → 63.1 kJ/kg |

In Excel (for °C):

=610.78*EXP(17.27*T_db/(T_db+237.3)) where T_db is in °C. (Less accurate but fine for HVAC basics.) =0.62198 * P_w / (P_atm - P_w) Where P_w = vapor pressure (Pa) = RH * P_sat / 100. 3. Relative Humidity (RH) from P_w =P_w / P_sat * 100 4. Enthalpy (kJ/kg da) = 1.006 * T_db + W * (2501 + 1.86 * T_db) 5. Wet-Bulb Temperature (iterative in Excel) No direct formula – use iterative calculation or a lookup table. A common workaround: use the psychrometric function from an add-in (see Part 4). Part 3: Plotting a Basic Psychrometric Chart in Excel You can create a constant relative humidity curve for a chart. Step 1: Set up data table | T_db (°C) | RH 10% | RH 30% | RH 50% | RH 70% | RH 100% | |-----------|--------|--------|--------|--------|---------| Step 2: Calculate P_sat for each dry-bulb temp Column A: T_db (0 to 50°C, step 2°C) Column B: =610.78*EXP(17.27*A2/(A2+237.3)) (P_sat in Pa) Step 3: Calculate W for each RH For RH=10%: =0.62198*(0.1*B2)/(101325 - 0.1*B2) psychrometric chart excel

In Excel using Magnus formula:

Assume pressure = 101.325 kPa (sea level). Hyland-Wexler equation (simplified): | Cell | Value | |------|-------| | A1