The Investigation On Press Drop And Heat Transfer Characteristics Of Serrated Spiral Finned Tubes

Spiral finned tube is very important in the combined cycle Heat Recover Steam Generator(HRSG).The research on enhancing heat transfer of spiral finned tube has always been hotspots.It is very significant for research and practical application to investigate press drop and heat transfer characteristics of spiral finned tube.In this paper,the resistance and heat transfer characteristics of serrated spiral finned tubes in combined cycle HRSG are studied through numerical simulation and verified by experiment methods.The heat transfer and resistance characteristics of serrated spiral finned tube bundles are obtained through experiments under different conditions,namely various flue gas flow rates,flue gas temperature,flue gas moisture content and water flow rates in the high temperature vent in this paper.The results show that the heat transfer is enhanced with the increase of the flow velocity on both air and water side.The moisture content in the flue gas shows remarkable influence on the heat transfer characteristics,but little effect on the resistance characteristics.Compared with the 5%wt water condition,Nusselt number(Nu)in the 7%wt and 9%wt water condition increases by approximately 1%-2%and 7%-9%respectively.The heat transfer is enhanced and the resistance is reduced through increasing flue gas temperature,however,greater investment cost is induced accordingly and the life of equipment is shortened.To study the effects of fin pitch and fin profile on the performance of finned tubes,the performance of three serrated spiral finned tube bundles with diffirent fin pitches,serrated spiral finned tube and twisted serrated spiral finned tube with the same fin pitch are analyzed by numerical simulation under two different flue gas temperatures including 250℃ and 350 ℃.The results show that increasing fin pitch is beneficial to the enhancement of heat transfer and the reduction of flow resistance in the experimental range.In addition,the effect of fin pitch on the flow resistance and heat transfer characteristics of the finned tube is quite significant.Compared with serrated spiral finned tube,heat transfer and resistance characteristics of twisted serrated spiral finned tube are both enhanced,and the comprehensive heat transfer performance is better.