oce (version 0.9-17)

swThermalConductivity: Seawater thermal conductivity

Description

Compute seawater thermal conductivity, in $W m^{-1\circ}C^{-1}$

Usage

swThermalConductivity(salinity, temperature=NULL, pressure=NULL)

Arguments

salinity

salinity [PSU], or a ctd object, in which case temperature and pressure will be ignored.

temperature

in-situ temperature [$^\circ$C]

pressure

pressure [dbar]

Value

• Conductivity of seawater in $W m^{-1\,\circ}C^{-1}$.

  To calculate thermal diffusivity in $m^2/s$, divide by the product of density and specific heat, as in the example.

Details

Caldwell's (1974 equation 9) formulation is used. If the first argument is an appropriate oce object, then the salinity, temperature and pressure values are extracted from it and then used in the calculation, ignoring the values of the other arguments.

Table 1 of Caldwell 1974 gives 1478e-6 cal/(cm*s*degC) at S=31.5, T=10, and p=1kbar=1e4dbar, based on another scheme that is somewhat difficult to understand. Thus, the "table 1" value in the examples is not a check value, but rather a demonstration that Caldwell's two methods agree to about 0.1 percent, well within the 0.5 percent that he states as the accuracty for his equation.

References

Caldwell, Douglas R., 1974. Thermal conductivity of seawater, Deep-sea Research, 21, 131-137.

Examples

library(oce)
# Values in m^2/s, a unit that is often used instead of W/(m*degC).
swThermalConductivity(35, 10, 100) / (swRho(35,10,100) * swSpecificHeat(35,10,100)) # ocean
swThermalConductivity(0, 20, 0) / (swRho(0, 20, 0) * swSpecificHeat(0, 20, 0)) # lab
# Comparison with Caldwell Table 1.
swThermalConductivity(31.5,10,1.0e4) / 418.4 * 1e6 # cf Caldwell table 1