Relative Humidity from Wet-Bulb Calculator

Wet/dry psychrometer vapor-pressure balance with independently matched liquid/pressure coefficient and saturation pressures; no saturation equation invented. Caller independently establishes units, regime, calibration and applicability; this does not establish design-code compliance, authenticity, operational safety, treatment efficacy or a validated forecast.

Description

A wet-bulb humidity model uses supplied saturation pressures and a psychrometric coefficient.

A wet-bulb humidity model uses supplied saturation pressures and a psychrometric coefficient.^[1]

Temperature observations alone are insufficient unless those reference values match pressure and phase conditions. Use this tool to calculate relative Humidity from Wet-Bulb from the supplied measurements and assumptions.

When to use Relative Humidity from Wet-Bulb Calculator

Use this tool to calculate relative Humidity from Wet-Bulb from the supplied measurements and assumptions. Establish the SI units or caller unit basis, load signs, measurement interval, model conditions and independently chosen coefficients or references.

How to use Relative Humidity from Wet-Bulb Calculator and understand its results

Establish the SI units or caller unit basis, load signs, measurement interval, model conditions and independently chosen coefficients or references.
Enter dryBulbC, wetBulbC, totalPressurePa, callerWetBulbSaturationPa, callerDryBulbSaturationPa, callerPsychrometerPerC, using the field meanings and rules below, then run the tool.
Read psychrometricRelativeHumidityFraction. Interpret the fields using their units, signs and evidence conventions below.
If input validation fails, correct the reported field and run again. Before applying the result, check reference scope, model assumptions and any missing evidence or placeholder values.

Input field	Meaning	Value type	Requirement
dryBulbC	Dry bulb c	number	Required
wetBulbC	Wet bulb c	number	Required
totalPressurePa	Total pressure pa	number	Required
callerWetBulbSaturationPa	Caller wet bulb saturation pa	number	Required
callerDryBulbSaturationPa	Caller dry bulb saturation pa	number	Required
callerPsychrometerPerC	Caller psychrometer per c	number	Required

Enter finite dry/wet temperatures with wet≤dry and positive total pressure, matched wet/dry saturation pressures and psychrometric coefficient, using consistent pressure units. Vapor pressure is wet saturation minus coefficient×totalPressure×(dry−wet). Divide by dry saturation and require RH in [0,1]; otherwise fail. No saturation-pressure table or phase correction is generated.

vaporPressure=esWet−A×P×(Tdry−Twet); RHfraction=vaporPressure/esDry

Use the exact units, boundary rules, ordering and missing-evidence conventions above.

Output field	Meaning	Value type
psychrometricRelativeHumidityFraction	Psychrometric Relative Humidity Fraction; follow the units, sign, ordering and evidence convention stated above	number

json

{
  "input": {
    "dryBulbC": 20,
    "wetBulbC": 15,
    "totalPressurePa": 100000,
    "callerWetBulbSaturationPa": 2000,
    "callerDryBulbSaturationPa": 3000,
    "callerPsychrometerPerC": 0.001
  },
  "output": {
    "psychrometricRelativeHumidityFraction": 0.5
  }
}

Limitations and assumptions

Temperature observations alone are insufficient unless those reference values match pressure and phase conditions. Interpretation depends on the units, sampling scope and exact model described above.

All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse evidence arrays fail validation; the specific bounds and alignment requirements are stated above. Extremely large inputs or outputs can also be rejected. An input error is distinct from a successful result reporting false, no matches or missing evidence.

Alternative or Complementary methods

Use Heat Recovery Effectiveness Calculator for this related task: Heat-recovery effectiveness compares recovered heat with a capacity-limited inlet driving potential.

Use Steam Specific Enthalpy Approx Calculator when its separate inputs and assumptions fit the question: Steam enthalpy depends on state and the adopted thermodynamic relation.

References

Relative Humidity from Wet-Bulb Calculator — tool.io

Similar or alternative tools

Heat Recovery Effectiveness Calculator
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Steam Specific Enthalpy Approx Calculator
Steam enthalpy depends on state and the adopted thermodynamic relation.