Specific gravity and diameters of floating balls affect high efficiency of evaporation suppression from free water surface

Abstract

Using floating materials such as plastic floating balls to control evaporation suppression is more popular for evaporation loss reduction from free water surface of a pond and reservoir.  The objectives of this study is to conduct a small scale field experiments to identify appropriate submerged depth or specific gravity and diameter of the floating balls that provides the highest efficiency of evaporation suppression.  The field experiment is carried out at Water Supply Unit, Building and Ground Division, Suranaree University of Technology (SUT).  Four small open plastic tanks are used consist of 1 control tank and 3 experimental tanks.  These tanks are located in the same place and controlled by the same climatic condition.  The first experiment uses equal ball diameter 7.5 cm. the highest efficiency is 67 % occurring at submerged depth 30% (compared between 15 30 and 50%) of ball diameter and specific gravity is 0.0203. The second experiment use equal ball diameter 7.5 cm., the highest efficiency is 67 % occurring at submerged depth 35% (compared between 25 35 and 40%) of ball diameter and specific gravity is 0.0260.  Combined results from both experiment show that submerged depth 35% provides the highest efficiency.  The third experiment use equal submerged depth at 35 % compare between diameters 7.5 12.5 and 17.5 cm.  The floating ball with diameter 7.5 cm provide the highest efficiency 55 %. This field experiment results can be applied to product floating balls with appropriate diameter and weight to provide high efficient of evaporation suppression in a real large reservoir.