D_x: Calculate diffusion coefficient for a given temperature and pressure

.get_Dx(D_0, Temp, eT, P, unitless)

Arguments

D_0: Diffusion coefficient at 273.15 K (0 °C) and 101.3246 kPa
Temp: Temperature in Kelvin
eT: Exponent for temperature dependence of diffusion
P: Atmospheric pressure in kPa
unitless: Logical. Should function use parameters with units? The function is faster when FALSE, but input must be in correct units or else results will be incorrect without any warning.

Value

Value in m$^2$/s of class units

Details

$$D = D_\mathrm{0} (T / 273.15) ^ {eT} (101.3246 / P)$$
According to Montieth & Unger (2013), eT is generally between 1.5 and 2. Their data in Appendix 3 indicate $eT = 1.75$ is reasonable for environmental physics.

References

Monteith JL, Unsworth MH. 2013. Principles of Environmental Physics. 4th edition. Academic Press, London.

Examples


tealeaves:::.get_Dx(
  D_0 = set_units(2.12e-05, m^2/s),
  Temp = set_units(298.15, K),
  eT = set_units(1.75),
  P = set_units(101.3246, kPa),
  unitless = FALSE
)
#> 2.471125e-05 [m^2/s]