Radiation Induced Thermal Stratification in Surface Layers of Stagnant Water

Abstract

Analysis is developed for the time dependent thermal stratification in surface layers of stagnant water by solar radiation. The transient temperature distribution is obtained by solving the one-dimensional energy equation for combined conduction and radiation energy transfer using a finite difference method. Experimentally, solar heating of water is simulated using tungsten filament lamps in parabolic reflectors of known spectral characteristics. The transient temperature distribution resulting from radiant heating of pure water in a glass-walled test cell is measured with a Mach-Zehnder interferometer. Measured and predicted temperature profiles show good agreement, thus verifying the radiation and total energy transfer models in stagnant water. It is found that the boundary condition at the air-water interface and internal radiant heating rate must be correctly specified in order to properly model stratification of water by radiation.