Study On The Hydrodynamic Characteristics Of Small Type Water-fire Tube Hot Water Boilers

Water-fire tube boilers, which have always been more than a half of the total amounts of the industrial boilers in China, have been developing and renewing very quickly in the nearest 20 years, particularly to small and large types water-fire tube hot water boilers which have been applied extensively in northern district heat supply systems in our country and also welcome by all customers. But being limited by the structure characteristics of boilers and affected by the poor quality water of industrial boilers in our nation, the questions of hydrodynamic credibilities for the boilers have been put forward rigorously, especially to small type water-fire tube hot water boilers.In this paper, the hydrodynamics is studied for the typical 5 types of 0.7MW～7.0MW small type water-fire tube hot water boilers and through natural circulation hydrodynamic calculation for the boilers, the circulation velocities in the water-cooled walls are far below the lowest safety circulation velocities only depending on the available head of natural circulation ,and the boilers can't operate safely. In order to raise the circulation velocities in the water-cooled walls, sprayers may be installed in the downcomers inlet– supply water injectors.Through cold hydrodynamic experiments and calculations, the circulation velocities in the water-cooled walls have been largely raised by installing supply water injectors. Moreover, the last average error between the datas of experiments and calculations is only 3.11%, and which is a reliable basis for combined circulation hydrodynamic calculations. That the circulation velocities in the water-cooled walls are far above the lowest safety circulation velocities has been certified by combined circulation hydrodynamic calculations, and that the boilers may operate safely is assured. Therefore, that also lay the foundations of perfection and development with the small type water-fire tube hot water boilers.