Abstract
Thermal relaxation times (TRTs) of initially warm and cool waterdrops with radii larger than 1.7mm falling at terminal velocity in air were measured under conditions of about 20°C. The temperatures of both waterdrops exponentially approach the wet bulb temperature of environmental air. The TRTs of both waterdrops linearly increase with increasing radius. The TRTs of cool waterdrops are larger than those of warm ones. The relationship between the TRTs (τ) of cool and warm waterdrops and their equlvalent radii (a) larger than 1.7mm are respectively expressed as the following formulas: τcool=3.82a-2.76, τwarm=2.37a-0.20 (a is given in mm).
