The Application Research Of Swirl Heat Transfer On The Air Preheater Of Boiler

Technology of enhancing heat transfer, which can improve efficiency of heat exchanger and reduce equipment's weight and volume, is always attached importance to by engineers and scientists. After energy crisis in 1970s, technology of enhancing heat transfer is developed greatly. Some technologies of enhancing heat transfer have been applied widely, but there is a same problem in these technologies, namely, fluid resistance's enhancement is more than heat transfer's.Air preheater is the indispensable heating surface of utility boiler, it can reduce exhaust gas temperature, preheat air of combustion, enhance combustion, raise boiler efficiency. This paper carries out a theoretical analysis on heat transfer enhancement mechanism of spiral twisted-tape inserted in the tube, this paper uses numerical simulation to analyze the velocity distribution of smooth and twisted-tape inserted in the tube, SIMPLEC algorithm for pressure modifiability, based on second order upwind scheme for convection term differencing, simulate the velocity in three-dimensional area, compute heat transfer coefficient, resistance coefficient and pressure drop of different twist ratio and gas velocity, get heat transfer and resistance distribution map of different condition.The numerical simulation result suggests that: Technology of enhancing heat transfer by twisted-tape inserted in the tube can raise heat transfer coefficient greatly and the resistance increases at the same time. The heat transfer capability and resistance coefficient increases with the decline of twist ratio. The comparison of heat transfer capability of each state with a new standard about heat transfer and flow, and provides reference data for design and reconstruction of air preheater.For comparison of enhancing heat transfer capability of different twist ratio, a new standard about heat transfer and fluid resistance is brought forward. The new standard is simpler and more convenient and has more specific physical meaning than other known standards. Perhaps, it can be applied widely in study of heat transfer in future. It has reference value to the design of heat exchanger.