Analysis of a salt gradient solar pond a with an internal heat exchanger

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Solar ponds are bodies of water in which heat convection resulting from the absorption of solar radiation is suppressed by an artificially established salt concentration gradient. In this thesis a new method of heat extraction from the pond was investigated, both theoretically and experimentally. the method consisted of extracting heat from the whole body of the pond by means of a helical coil heat exchanger. because of the existence of a temperature gradient through the depth, the overall efficiency of such a solar collector was expected to increase. the developed theory of this system based on the steady state heat transfer theory predicts the effect of operating parameters such as insolation, flow rate and design parameters (such as length of the heat exchanger) on the pond and outlet fluid temperature and the efficiency. for the variation with time of the concentration of salt, the mass diffusion differential equation was solved. this shows how the gradient changes with time. the experimental investigation was carried out in the laboratory on small scale ponds which were heated artificially. instrumentation was developed for density and temperature measurements and data comparison between theoretical and experimental results were made and conclusions drawn concerning the performance of ponds with this configuration. the experimental results are in agreement with the theoretical e:lictions and there is an increase in efficiency with the new heat extraction system.