#' Calculate the convective heat transfer coefficient for a long cylinder in cross flow.
#'
#' Calculate the convective heat transfer coefficient for a long cylinder in cross flow.
#'
#' @param Tk value of air temperature in Kelvin.
#' @param Pair value of air pressure in hPa.
#' @param speed value of wind speed in m/s.
#' @param min.speed value of minimum wind speed in m/s.
#' @param diam.wick diameter of the cylinder in m.
#'
#' @return Convective heat transfer coefficient for a long cylinder, W/(m2 K).
#'
#' @author Ana Casanueva (05.01.2017).
#' @details Reference: Bedingfield and Drew, eqn 32.
h_cylinder_in_air <- function(Tk, Pair, speed, min.speed, diam.wick){
# Constants
m.air <- 28.97
r.gas <- 8314.34
r.air <- r.gas / m.air
cp <- 1003.5 # heat capaticy at constant pressure of dry air
Pr <- cp / (cp + (1.25 * r.air))
# Calculate the thermal conductivity of air, W/(m K)
therm.con <- thermal_cond(Tk)
# Density of the air
density <- Pair * 100 / (r.air * Tk)
if(speed < min.speed) speed <- min.speed
# Reynolds number
Re <- speed * density * diam.wick / viscosity(Tk)
# Nusselt number
Nu <- 0.281 * Re ^ 0.6 * Pr ^ 0.44
# Convective heat transfer coefficient in W/(m2 K) for a long cylinder in cross flow
h_cylinder_in_air <- Nu * therm.con / diam.wick
return(h_cylinder_in_air)
}
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