Construction and Evaluation of a Galvanized Steel Flat-Plate Collector for Water Heating Application

Recently, solar energy has grown to be an important source of energy with many applications - thermal and electrical. The solar flat plate collector, used in water heating systems, is one of the numerous thermal applications. The flat plate collector could be of parallel or serpentine tube designs. Considering the physical and optical properties of materials commonly used in collectors availability and costs of these materials, a cost-effective serpentine flat-plate collector was constructed. Galvanized steel pipes painted black served as the fluid tube and the absorber. The container/box was made of material with good insulating property (wood) and the interior of the box was insulated with a thin foam to reduce heat loss from bottom and the edges. The top was covered with a transparent glass to trap heat inside the box when exposed to solar radiation. Aluminum foil paper, due to its reflecting surface, was used as reflector to increase the amount of heat that could be absorbed by black galvanized steel pipes. Heat losses through convection were minimized by blocking all openings in the box. The solar collector was evaluated and the highest efficiency was estimated to be 63.1 % with an ambient temperature of about 26oC at 1230 L T during the mid of the June Solstice. The heat loss coefficient of the collector was obtained as 5.076 Wm-2 °C-1. Increasing the overall length of the black galvanized pipe (number of turns of the serpentine tube) could allow for more absorption of the incident and trapped heat, thereby reducing the heat loss coefficient and improving the efficiency of the collector