Malte
12th April 2010, 02:20 AM
Dear Forum,
I have a serious understanding problem with the bulk method for estimating evaporative heat flux.
From my understanding the following holds (using a measured average evap rate):
QE = Lv * dens_air * Evap_rate
Lv = 2,462,735 [J/kg]
dens_air = 1.22 [Kg/m3]
Evap_rate = 4 [mm/day] = 4/(86,400*1,000) [m/s]
This yields QE = 0.14 [J/(m2s)] = 0.14 [W/m2]
However, this value is 3 magnitudes too small. I assume that the density of water might be missing (1000 kg/m3), but all the formulas in the lit. I found use the density of air.
Thank you very much in advance for your help.
I have a serious understanding problem with the bulk method for estimating evaporative heat flux.
From my understanding the following holds (using a measured average evap rate):
QE = Lv * dens_air * Evap_rate
Lv = 2,462,735 [J/kg]
dens_air = 1.22 [Kg/m3]
Evap_rate = 4 [mm/day] = 4/(86,400*1,000) [m/s]
This yields QE = 0.14 [J/(m2s)] = 0.14 [W/m2]
However, this value is 3 magnitudes too small. I assume that the density of water might be missing (1000 kg/m3), but all the formulas in the lit. I found use the density of air.
Thank you very much in advance for your help.