A NOVEL CONFIGURATION FOR CONCENTRATED SOLAR COLLECTOR WITH NONE-CIRCULATED NANOFLUID

Abstract

Novel configuration for direct absorption solar collector has been developed. In the new configuration nonecirculated nano-fluid absorbs solar radiation through glass wall. The absorbed heat directly transfers to circulated water flowing inside copper tube submerged into the nano-fluid. Numerical model has been developed for flowing water, nanofluid annular region and the copper tube which separates the two different fluids. Heat absorption of concentrated solar arrays reflected by parabolic trough is simulated as a heat source in the energy equation solved in nano-fluid region. Three size ratios of copper-to-glass tube diameters have been examined under same solar radiation. The efficiency of one meter of solar receiver unit with glass-to-copper tube size ratio of (1/2) increases significantly with flow rate up to 65%.Since, water flow rate changes increasingly affect the efficiency, heat convection at water side plays very important role. The size ratio of (1/4) shows slightly lower efficiency for all flow rates, while (3/4) size ratio shows very poor efficiency due to insufficient depth of absorption and reduced Reynolds number of water flow. Circulating water restricts the raising of nano-fluid temperature and in turn reduces thermal losses. At the side of nano-fluid,both optimal depth of absorption and characterized length of natural convection seem to be at size ratio of (1/2) or slightly less. Temperature rising per one meter decreases with flow rate despite of performance enhancing.