A Novel Configuration for Concentrated Solar Collector with None-Circulated Nanofluid
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.
Keywords - Solar collector, direct absorption, concentrated solar collector, nano-fluid.