Psychrometrics

Saturation Vapor Pressure (p_sat)

Source code

Calculates vapour pressure of water at different temperatures

p_sat(tdb: number): number
Parameters
  • tdb (number) air temperature, [°C]
Returns
number : vapour pressure of water, [Pa]

Saturation Vapor Pressure in Torr

Source code

Estimates the saturation vapour pressure in [torr].

p_sat_torr(tdb: number): number
Parameters
  • tdb (number) dry bulb air temperature [C]
Returns
number : saturation vapour pressure [torr]

Operative Temperature (t_o)

Source code

Calculates operative temperature in accordance with ISO 7726:1998 [5].

t_o(tdb: number, tr: number, v: number, standard: ("ISO" | "ASHRAE")): number
Parameters
  • tdb (number) air temperature [C]
  • tr (number) mean radiant temperature [C]
  • v (number) air speed [m/s]
  • standard (("ISO" | "ASHRAE") = "ISO") the standard to use
Returns
number : operative temperature [C]

Operative Temperature — Array

Source code

Calculates operative temperature in accordance with ISO 7726:1998 [5].

t_o_array(tdb: Array<number>, tr: Array<number>, v: Array<number>, standard: ("ISO" | "ASHRAE")): Array<number>
Parameters
  • tdb (Array<number>) air temperature [C]
  • tr (Array<number>) mean radiant temperature [C]
  • v (Array<number>) air speed [m/s]
  • standard (("ISO" | "ASHRAE") = "ISO") the standard to use
Returns
Array<number> : operative temperature [C]

Enthalpy

Source code

Calculates air enthalpy

enthalpy(tdb: number, hr: number): number
Parameters
  • tdb (number) air temperature [C]
  • hr (number) humidity ratio [kg water/kg dry air]
Returns
number : enthalpy [J/kg dry air]

Wet Bulb Temperature (t_wb)

Source code

Calculates the wet-bulb temperature using the Stull equation [6].

t_wb(tdb: number, rh: number): number
Parameters
  • tdb (number) air temperature, [°C]
  • rh (number) relative humidity, [%]
Returns
number : wet-bulb temperature, [°C]

Mean Radiant Temperature (t_mrt)

Source code

Converts globe temperature reading into mean radiant temperature in accordance with either the Mixed Convection developed by Teitelbaum E. et al. (2022) or the ISO 7726:1998 Standard [5].

t_mrt(tg: number, tdb: number, v: number, d: number, emissivity: number, standard: ("Mixed Convection" | "ISO")): number
Parameters
  • tg (number) globe temperature, [°C]
  • tdb (number) air temperature, [°C]
  • v (number) air speed, [m/s]
  • d (number = 0.15) diameter of the globe, [m] default 0.15 m
  • emissivity (number = 0.95) emissivity of the globe temperature sensor, default 0.95
  • standard (("Mixed Convection" | "ISO") = "Mixed Convection") either choose between the Mixed Convection and ISO formulations. The Mixed Convection formulation has been proposed by Teitelbaum E. et al. (2022) to better determine the free and forced convection coefficient used in the calculation of the mean radiant temperature. They also showed that mean radiant temperature measured with ping-pong ball-sized globe thermometers is not reliable due to a stochastic convective bias [22] . The Mixed Convection model has only been validated for globe sensors with a diameter between 0.04 and 0.15 m.
Returns
number :

Psychrometric Properties (psy_ta_rh)

Source code

Calculates psychrometric values of air based on dry bulb air temperature and relative humidity.

psy_ta_rh(tdb: number, rh: number, p_atm: number): PsyTaRhReturnType
Parameters
  • tdb (number) air temperature, [°C]
  • rh (number) relative humidity, [%]
  • p_atm (number = 101325) atmospheric pressure, [Pa]
Returns
PsyTaRhReturnType : object with calculated psychrometrics values
Example
import { psy_ta_rh } from "jsthermalcomfort";
const results = psy_ta_rh(21, 56);
console.log(results); // { p_sat: 2487.7, p_vap: 1393.112, hr: -2.2041754048718936, t_wb: 15.4, t_dp: 11.9, h: -5575107.96 }