oce (version 0.9-18)

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], defined on the ITS-90 scale; see Temperature units in the documentation for swRho.

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) detailed formulation is used. To be specific, his equation 6 to calculate K, and his two sentences above that equation are used to infer this to be K(0,T,S) in his notation of equation 7. Then, application of his equations 7 and 8 is straightforward. He states an accuracy for this method of 0.3 percent. (See the check against his Table 1 in the Examples.)

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.

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
# Caldwell Table 1 gives 1478e-6 cal/(cm*sec*degC) at 31.5 o/oo, 10degC, 1kbar
joulePerCalorie <- 4.18400
cmPerM <- 100
swThermalConductivity(31.5,10,1000) / joulePerCalorie / cmPerM