R/PMV.R

In Iavalos/Comfort: Thermal comfort methods

PMV <-
function(clo, met, air.temp, RH, ws) {
  # Adapted from CIBSE Guide A, 1.A1.2, p. 51
  #In accordance with International Standard, ISO 7730 and ASHRAE Standard 55
  saturated.vapour.pressure <- exp(16.6536-4030.183/(air.temp+235)) # kPa
  vapour.pressure <- saturated.vapour.pressure*10*RH # Pa
  clothing.insulation <- 0.155*clo
  met.rate <- met*58.15 #w/m2
  external.work <- 0 # simplification
  int.heat.prod <- met.rate - external.work
  clo.area.fact <- ifelse(clothing.insulation<0.078,
                          1 + 1.29*clothing.insulation,
                          1.05 + 0.645*clothing.insulation)
  convective.heat <-  12.1 * sqrt(ws)
  air.temp.kel <- air.temp + 273
  mean.rad.temp <- air.temp.kel # simplification
  # compute clothing surface temperature by iteration
  clo.surf.temp <- air.temp.kel +
    (35.5 - air.temp)/(3.5*(6.45*clothing.insulation + 0.1))
  p1 <- clothing.insulation*clo.area.fact
  p2 <- p1*3.96
  p3 <- p1*100
  p4 <- p1*air.temp.kel
  p5 <- 308.7 - 0.028*int.heat.prod + p2*(mean.rad.temp/100)^4
  xn <- clo.surf.temp/100
  xf <- xn
  eps <- 0.000015
  hc <- 0
  repeat {
    xf <- (xf + xn)/2
    heat.transf.nat <- 2.38*abs(100*xf-air.temp.kel)^0.25
    hc <- ifelse(convective.heat > heat.transf.nat, convective.heat, heat.transf.nat)
    xn <- (p5 + p4*hc - p2*xf^4)/(100 + p3*hc)
    if (all(abs(xn-xf)<eps)) break
  }
  clo.surf.temp <- 100*xn - 273
  # end iteration
  heat.loss.skin <- 3.05*0.001*(5733-6.99*int.heat.prod-vapour.pressure) 
  heat.loss.sweat <- pmax(0.42*(int.heat.prod - 58.15), 0)
  heat.loss.respiration <- 1.7*0.00001*met.rate*(5867 - vapour.pressure)
  heat.loss.dry <- 0.0014*met.rate*(34 - air.temp)
  heat.loss.rad <- 3.96*clo.area.fact*(xn^4 - (mean.rad.temp/100)^4)
  heat.loss.conv <- clo.area.fact*hc*(clo.surf.temp - air.temp)
  therm.sens <- 0.303*exp(-0.036*met.rate) + 0.028
  therm.sens*(int.heat.prod - heat.loss.skin - heat.loss.sweat
              - heat.loss.respiration - heat.loss.dry
              - heat.loss.rad - heat.loss.conv)
}