Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank

摘要

A comparative study of simultaneous heat and gas exchange measurements wasperformed in the large annular Heidelberg Air–Sea Interaction Facility, theAeolotron, under homogeneous water surface conditions. The use of two gastracers, N₂O and C₂HF₅, resulted not only in gas transfervelocities, but also in the measurement of the Schmidt number exponent nwith a precision of ±0.025. The original controlled flux, or activethermographic, technique proposed by J?hne et al. (1989) was applied byheating a large patch at the water surface to measure heat transfervelocities. Heating a large patch, the active thermography technique islaterally homogeneous, and problems of lateral transport effects are avoided.Using the measured Schmidt number exponents, the ratio of the scaled heattransfer velocities to the measured gas transfer velocities is 1.046 ±0.040, a good agreement within the limits of experimental uncertainties.This indicates the possibility to scale heat transfer velocities measured byactive thermography to gas transfer velocities, provided that the Schmidt numberexponent is known and that the heated patch is large enough to reach thethermal equilibrium.