An experiment to confirm how the Filter Paper’s Evaporation Method (FPEM) works well as an appropriate estimation of Mass Transfer Coefficient (MTC), which has been applied by quite a few studies in urban climatology. In an experimental process of FPEM, a thick filter paper wetted enough is pasted onto an acrylic-plastic board so that is possible to measure an evaporation rate by the weight loss during an exposed minutes, which can be transformed into the MTC when you also measure the filter paper’s surface temperature and air humidity. The key issue in FPEM is whether and how long a wet filter paper can keep its saturation during the exposed minutes, which is primarily focused in the present study. In the experiment, an evaporating amount from a flat-water surface is also measured, which is requisite to compare as the reference of a perfect saturated surface with the filter paper surface. To ensure accuracy, the exposed air is kept in calm and dry condition in the experiment. The result insists that we can see a filter paper as an almost perfect saturated surface unless the accumulated evaporation surpasses over 625 g/m^2.
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