Design and simulation of a heating system for water purification structures in cold rural areas

The settlement process and the biological treatment process of raw water purification can often not be completed efficiently under low ambient temperature in cold rural areas. Thus, a supplementary heating system is essential for water purification structures under these conditions. This paper proposes a novel hybrid heating system with a combination of solar heating and straw-boiler heating, in which the solar collectors and the straw boiler run in parallel as the heating source. The heat transfer model of the coagulation-sedimentation tank, the main heating position in a purification structure, has been established. Employing FLUENT software, the heat transfer conditions of different heating modes are simulated and analyzed to determine the optimal heating location. Then, the effect of the insulation thickness on heat loss is simulated, and, thus, the optimal thickness of the insulation layer is determined. Finally, for the novel heating system, the solar fraction and the duty ratio of the straw boiler in different months are calculated. Results show that the proposed heating system can perfectly meet the temperature demands of a water treatment plant in cold rural areas, and provide theoretical guidance and technical support for water purification structure heating in cold rural areas.