R/psychrometric-graph-par-w-press.R

In jinlee86/bems_analysisr_package: EDAS System R Package

#' Partial water vapour pressure (p_w)
#'
#' Calculates partial water vapour pressure.
#' Eq. 36 - ASHRAE Fundamentals Handbook 2002, Psychrometrics.
#' @param hum.ratio Vector of humidity ratios [kg/kg].
#' @param alt Vector of altitudes [m]. Defaults to 0 m (sea level).
#' @family PsychrometricGraph
#' @return Returns a vector of partial water vapour pressure [kPa].
#' @export
#' @examples
#' par_w_press(hum.ratio = 0.010)
#'
#' hum.ratio <- rep(c(0.005, 0.010), 2)
#' alt <- rep(c(0, 500), each = 2)
#' par_w_press(hum.ratio, alt)
#' @author Christoffer Rasmussen

par_w_press <- function(hum.ratio, alt = 0) {
  
  # Partial water vapor pressure (eq. 36)
  return(bar_press(alt) * hum.ratio / (0.62198 + hum.ratio))
}