A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1986

Even though some improvements in performance of the conventional flat - plate collector for water heating have been achieved by adding expensive selective coating, the possibility of simple alternative approach has been overlooked. In this study, a new approach of solar water heating, the phenomenon of total internal reflection, is investigated. A prototype solar thermal collector, named "Prismatic Solar Thermal Collector" is designed and fabricated for experimental investigations. The collector of this type is simple and cheap compare to conventional flat - plate collectors, and h as high fluid storage capacity per unit aperture area as such additional storage is not essential. The experimental results s how a high optical efficiency of 0. 87 a nd 0 . 78 with an additional glass cover. The h eat loss coefficient of the collector decreased from 22 W/m2 °C to 13 W/m2 °C by fixing the additional glass cover. The flow pattern of the working fluid in the collector is not too critical for the performance as solar radiation is mostly absorbed directly by the working fluid. A model used to determine the instantaneous performance parameters of this collector is developed to predict mean fluid temperature of the collector. The predicted and the experimental values are close to each other, which confirms the validity of the model used. The preliminary economic analysis shows that the cost of solar energy is about 0. 83 6 per kWh which is 55% less than the cost of average domestic electricity at 1 . 85 6per kWh.