Study On Indirect Condensation Mechanism In Seawater Utilization Combined System By Solar Chimney Technology

Aiming at eliminating the shortages of solar chimney, solar desalination and environmental requirement being considered, combined systems utilizing seawater by solar chimney technology were put forward firstly. Then theoretical analyses were done to evaluate the feasibilities of technology and economy. Finally, condenser of combined systems was designed, and the theoretical water output was proved truly.The mechanism of indirect heat exchanging and condensation was mainly studied on. An indirect experimental condenser system was set up for vertical smooth tube and fin tube in different conditions of temperatures and velocities, to obtain data on temperature distribution, the relationship of temperature with air velocity, the height of solar chimney, the heat collecting, and the effects of noncondensable gases, the condensation ability of forced fin tube. Then two theory models of smooth tube, the attenuation coefficient model and diffusion model, were made considering the influence of noncondensable gases concentration, interface shearing forces, diversities of parameters and the Reynolds number of condensate film.Performance evaluation results indicate that the combined system can produce 750.05ton/(m2·a) water, 8.35ton/(m2·a) salt, 1.11kWh/(m2·a) wind power and 0.29kWh/(m2·a) water power at the chimney height of 200m. The air flow in the saturated hot air controls the heat exchanging process and the water collecting velocity. For smooth tube, the optimum condensation occurs at the critical wind velocity, the higher collecting temperature and the wave crest of the effective condensation efficiency, and also temperature distributions, theoretical wind velocity formula was given. Good quality of the fin tube on heat exchanging was confirmed, but not for condensate water collecting. Two non-iterative theoretical models can be calculated from the experimental data directly which suitable well for the water collection and the heat exchanging of saturated hot air, and the liquid film resistance can be neglected. It is believed that experimental or theoretical results in this paper will provide basic data or act as reference for future large scale combined system. The application of this style combined system will blaze a way in realizing economical utilization of solar energy.