Psychrometrics.jl

Installing and Loading Psychrometrics

Psychrometrics can be installed and loaded either from the JuliaHub repository (last released version) or from the maintainer's repository.

Last Released Version

The last version of Psychrometrics can be installed from JuliaHub repository:

using Pkg
Pkg.add("Psychrometrics")
using Psychrometrics

If Psychrometrics is already installed, it can be updated:

using Pkg
Pkg.update("Psychrometrics")
using Psychrometrics

Pre-Release (Under Construction) Version

The pre-release (under construction) version of Psychrometrics can be installed from the maintainer's repository.

using Pkg
Pkg.add(path="https://github.com/aumpierre-unb/Psychrometrics.jl")
using Psychrometrics

Citation of Psychrometrics

You can cite all versions (both released and pre-released), by using 10.5281/zenodo.7493474.

This DOI represents all versions, and will always resolve to the latest one.

For citation of the last released version of Psychrometrics, please check CITATION file at the maintainer's repository.

The Psychrometrics Module for Julia

Psychrometrics provides a set of functions to compute the various variables related to water vapor humid air, providing the following functions:

• psychro
• humidity
• satPress
• enthalpy
• volume
• adiabSat
• dewTemp
• doPlot

psychro

psychro computes

• the dry bulb temperature,
• the wet bulb temperature,
• the dew point temperature,
• the adiabatic saturation temperature,
• the humidity,
• the saturation humidity,
• the saturation humidity at wet bulb temperature,
• the adiabatic saturation humidity,
• the relative humidity,
• the specific enthalpy,
• the specific volume,
• the density,
• the water vapor pressure,
• the saturation pressure and
• the saturation pressure at wet bulb temperature.

given any two of the following parameters:

• the dry bulb temperature,
• the wet bulb temperature,
• the dew point temperature,
• the humidity,
• the specific enthalpy,
• the specific volume and
• the relative humidity,

except for the combination of humidity and dew point temperature, which are not mutually independent.

If a different number of parameters is given, execution will be aborted.

If fig = true is given a schematic psychrometric chart is plotted as a graphical representation of the solution.

By default, psychro plots a schematic psychrometric chart with the solution (fig = true) with white background (back = :white). If fig = false is given, plot is omitted.

Syntax:

psychro(;
    Tdry::Number=NaN, # dry bulb temperature
    Twet::Number=NaN,  # wet bulb temperature
    Tdew::Number=NaN, # dew bulb temperature
    W::Number=NaN, # absolute humidity
    φ::Number=NaN, # relative humidity
    h::Number=NaN, # specific enthalpy
    v::Number=NaN, # specific volume
    fig::Bool=false, # show/omit chart
    back::Symbol=:white, # plot background color
    unit::Symbol=:K # units for temperature (:K or :°C)
    )::HumidAir

Examples:

Compute the dry bulb temperature, the wet bulb temperature, the dew point temperature, the adiabatic saturation temperature, the humidity, the saturation humidity, the saturation humidity at wet bulb temperature, the adiabatic saturation humidity, the relative humidity, the specific enthalpy, the specific volume, the density, the water vapor pressure, the saturation pressure, the saturation pressure at wet bulb temperature given the dew point temperature is 22 °C and the relative humidity is 29 %.

humidAir = psychro( # all results ordered in one tuple
    Tdew=22 + 273.15, # dew temperature in K
    φ=0.29, # relative humidity
    fig=true # show plot
    )
humidAir.φ # relative humidity
humidAir.Tdry # dry bulb temperature
humidAir.Twet # wet bulb temperature

Compute the dry bulb temperature, the wet bulb temperature, the dew point temperature, the adiabatic saturation temperature, the humidity, the saturation humidity, the saturation humidity at wet bulb temperature, the adiabatic saturation humidity, the relative humidity, the specific enthalpy, the specific volume, the density, the water vapor pressure, the saturation pressure, the saturation pressure at wet bulb temperature given the specific enthalpy is 79.5 kJ/kg and the relative humidity is 0.29 # and plot a graphical representation of the answer in a schematic psychrometric chart.

psychro(
    h=79.5e3, # specific enthalpy in kJ/kg of dry air
    φ=0.29, # relative humidity
    fig=true, # show plot
    back=:transparent, # plot background transparent
    unit=:°C # temperature in °C
    )

8.5 cubic meters of humid air at dry bulb temperature of 293 K and wet bulb temperature of 288 K is subjected to two cycles of heating to 323 and adiabatic saturation. Compute the energy and water vapor demands. Assume the amount of dry air is constant.

state1 = psychro( # initial condition
    Tdry=293,
    Twet=288,
    fig=true
    )
sleep(3)
state2 = psychro( # thermodynamic state after the firstheating is
    Tdry=323,
    W=state1.W,
    fig=true
    )
sleep(3)
begin # thermodynamic state the after first adiabatic saturation
    local Tdry, W = adiabSat(
        state2.h,
        fig=true
        )
    state3 = psychro(
        Tdry=Tdry,
        W=W,
        fig=true
        )
end
sleep(3)
state4 = psychro( # thermodynamic state after the second heating
    Tdry=323,
    W=state3.W,
    fig=true
    )
sleep(3)
begin # thermodynamic state the after second adiabatic saturation
    local Tdry, W = adiabSat(
        state4.h,
        fig=true
        )
    state5 = psychro(
        Tdry=Tdry,
        W=W,
        fig=true
        )
end
sleep(3)
begin # energy demand
    local V = 8.5 # initial volume of humid air is
    (state5.h - state1.h) * (V / state1.v)
end
begin # water vapor demand
    local V = 8.5 # initial volume of humid air is
    (state5.W - state1.W) * (V / state1.v)
end
try # PrettyTables is not included in Psychrometrics!
    using PrettyTables
    local table = [name for name in fieldnames(Psychrometrics.HumidAir)]
    for i in (state1, state2, state3, state4, state5)
        table = [table [getfield(i, field) for field in 1:nfields(i)]]
    end
    local header = [
        "Parameter", "State 1", "State 2", "State 3", "State 4", "State 5"
        ]
    print(
        "\nSummary of process states:\n"
    )
    pretty_table(table, header=header)
    catch
end

humidity

humidity computes the humidity W (in kg/kg of dry air) of humid air given the water vapor pressure pw (in Pa) and the total pressure p (in Pa).

By default, total pressure is assumed to be the atmospheric pressure at sea level, p = 101325.

Syntax:

humidity( # humidity in kg/kg of dry air
    pw::Number, # water vapor pressure in Pa
    p::Number=101325 # total pressure in Pa
    )

Examples:

Compute the humidity of humid air at atmospheric pressure given water vapor pressure is 1 kPa at 1 atm total pressure.

humidity( # humidity in kg/kg of dry air
    1e3 # water vapor pressure in Pa
    )

Compute the humidity of humid air at atmospheric pressure given water vapor pressure is 1 kPa at 10 atm total pressure.

humidity( # humidity in kg/kg of dry air
    1e3, # water vapor pressure in Pa
    101325e1 # total pressure in Pa
    )

satPress

satPress computes the saturation pressure psat (in pa) of humid air given the dry bulb temperature Tdry (in K).

Syntax:

satPress( # saturation pressure in Pa
    Tdry::Number # dry bulb temperature in K
    )

Examples:

Compute the saturation pressure given the dry bulb temperature is 25 °C.

satPress( # saturation pressure in Pa
    25 + 273.15; # dry bulb temperature in K
    )

enthalpy

enthalpy computes the specific enthalpy h (in J/kg of dry air) of humid air given the dry bulb temperature Tdry (in K) and the humidity W (in kg/kg of dry air).

Syntax:

enthalpy( # specific enthalpy in kJ/kg of dry air
    Tdry::Number, # dry bulb temperature in K
    W::Number # humidity in kg/kg of dry air
    )

Examples:

Compute the specific enthalpy given the dry bulb temperature is 25 °C and the humidity is 7 g/kg of dry air.

enthalpy( # specific enthalpy in J/kg of dry air
    25 + 273.15, # dry bulb temperature in K
    7e-3 # humidity in kg/kg of dry air
    )

volume

volume computes the specific volume v (in cu. m/kg of dry air) of humid air given the dry bulb temperature Tdry (in K), the humidity W (in kg/kg of dry air) and the total pressure p (in Pa).

By default, total pressure is assumed to be the atmospheric pressure at sea level, p = 101325.

Syntax:

volume( # specific enthalpy in J/kg of dry air
    Tdry::Number, # dry bulb temperature in K
    W::Number, # humidity in kg/kg of dry air
    p::Number=101325 # total pressure in Pa
    )

Examples:

Compute the specific volume given the dry bulb temperature is 25 °C and the humidity is 7 g/kg of dry air at 1 atm total pressure.

volume( # specific volume in cu. m/kg of dry air
    25 + 273.15, # dry bulb temperature in K 
    7e-3 # humidity in kg/kg of dry air
    )

adiabSat

adiabSat computes the adiabatic saturation temperature Tadiab (in K) and the adiabatic saturation humidity Wadiab (in Kg/kg of dry air) given the specific enthalpy h (in J/kg of dry air).

If fig = true is given, a schematic psychrometric chart is plotted as a graphical representation of the solution.

Syntax:

adiabSat( # adiabatic saturation temperature in K
    h::Number; # specific enthalpy in J/kg of dry air
    fig::Bool=false, # show/omit chart
    back::Symbol=:white, # plot background color
    unit::Symbol=:K # units for temperature (:K or :°C)
    )

Examples:

Compute the adiabatic saturation temperature given the specific enthalpy is 82.4 kJ/kg of dry air and plot a graphical representation of the answer in a schematic psychrometric chart.

adiabSat(
    82.4e3, # specific enthalpy in J/kg of dry air
    fig=true # show plot
    )

dewTemp

dewTemp computes the dew point temperature Tdew (in K) of humid air given the water vapor pressure pw (in Pa).

Syntax:

dewTemp( # dew point temperature in K
    pw::Number # water vapor pressure in Pa
    )

Examples:

Compute the dew temperature of humid air given the water vapor pressure is 1 kPa.

dewTemp( # dew temperature in K
    1e3 # water vapor pressure in Pa
    )

doPlot

doPlot plots a schematic psychrometric chart.

Syntax:

doPlot(;
    back::Symbol=:white,
    unit::Symbol=:°C
    )

Examples:

Build a schematic psychrometric chart with temperature in °C with transparent background and save figure as psychrometricChart_transparent.svg.

doPlot(
    back=:transparent, # plot background transparent
    unit=:°C # temperature in °C
    )
using Plots
savefig("psychrometricChart_transparent.svg")

Reference

The theory and the adjusted equations used in this package were taken from the first chapter of the 2017 ASHRAE Handbook Fundamentals Systems - International Metric System, published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers.

Acknowledgements

The author of Psychrometrics package acknowledges Professor Brent Stephens, Ph.D. from the Illinois Institute of Technology for kindly suggesting the source reference for equations used in this package.

See Also

McCabeThiele.jl, PonchonSavarit.jl, InternalFluidFlow.jl.

Copyright © 2022 2023 2024 Alexandre Umpierre

email: [email protected]