Study On The Heat Transfer Enhancement Of Atmospheric Cast Iron Gas Boiler

Fossil fuel is the power source of human civilization progress. In China's energy consumption structure, coal maintains at a high level of around 70% for a long time. As the energy shortage and environment pollution especially atmospheric pollution is becoming more and more serious, nature gas is receiving an increasing amount of attention as clean energy, and becoming one of the fastest growth clean energy in consumption. Nature gas boiler is important natural gas application equipment; it will be spread and used widely in our country's energy structure adjustment progress. In this paper, the structure and characteristics of the atmospheric cast iron gas boiler were studied, and feasible improvement design scheme was put forward to reduce the production cost of the boiler and improve the thermal efficiency.Through the test and analysis of thermal efficiency of existing atmospheric cast iron gas boiler, combine with the existing furnace and the rib wall heat transfer theory, and the exploration of various factors influencing the thermal efficiency of boiler, the boiler body was redesigned from furnace and the rib wall in order to design a high efficiency atmospheric cast iron gas boiler. The main improvement design includes: changing the half-surrounding type furnace to all around to improve the radiation angle coefficient; improving the structure of pin-fin to enhance the fin efficiency; altering the boiler section dimensions to improve the flue gas flow rate; decreasing the boiler section wall thickness to lighten up the boiler body weight; redesigning the atmospheric gas burner to decreased excess air coefficient; and redesigning the water side flow channel to enhance the heat transfer efficiency and avoid the scale settlement points. The existing boiler heat transfer calculation method were studied and compared, and the boiler heat transfer process was theoretical checked calculation by using the similar theory and ribbed wall heat transfer calculation. The designing scheme of improved boiler was obtained. Furthermore, a prototype boiler with 700 kW heat was manufactured according to the design drawings and thermal efficiency test was carried out. The test results met the design requirements basically. Compared with the existing boiler, the excess air ratio of the improved boiler declined from 1.7 to 1.4, the exhaust gas temperature reduced from 270°C to 150°C below, the theoretical combustion temperature increased from 1293.0°C to 1524.5°C, and the cast iron consumption of producing the boiler with equal heat production decreased by 17% so that the production cost of the boiler was reduced. In addition, through the economic and technical analysis, it was found that the type of atmospheric cast iron gas boiler was suitable for the gas boiler with1.4MW heat below.The improved design in this paper has improved the indexes of the original boiler greatly, and provided an important reference for atmospheric cast iron gas boiler innovation design.