Numerical Study On Flow And Heat Transfer Characteristics For Inside And Outside Of The Direct Air Cooler Tube Bundle

As cold-end system of air cooling unit，the Heat transfer efficiency of Direct AirCooled Condenser has a significant impact on the efficiency of the unit. The efficiency ofair-cooled condenser is directly affected by the air-cooled inside and outside flow andheat exchanger conditions of tube bundle, so In order to improve the efficiency ofair-cooling units, it is necessary to have a research on the characteristics of directair-cooled inside and outside flow and heat exchanger.It provides an overview of the basic principles of the power plant direct air-cooledcondenser and related theories of tubes heat transfer in this article. Building athree-dimensional mathematical model of physics for the different turbulence forms heatexchanger components including oval tube straight fin, oval tube opening rear fins andoval tube delta wing type vortex generator fins.Using FLUENT Numerical computingplatform gives the simulation of flow and heat transfer characteristics of cooled air tubesoutside，and reaches the distribution of velocity, pressure and temperature of air betweendifferent spoiler forms fin, then compared analyzes them, conclusions are as follows: theair-side heat transfer strength and flow resistance of oval tube straight fin, oval tubeopenings oval tube rear fin and oval tube post vortex generators fin increases in turn, theeffect of finned post vortex generator on weakening the oval tube outside wake zone issignificant.Research the variation of air side flow resistance and heat transfer performance overface velocity, fin spacing of three forms spoiler fin tube bundles, discuss the influence ofchanges in attacking angle on flow and heat transfer of rear vortex generator finned tubes,give a field synergy analysis on heat exchanger unit of entire fin and reach that: With theincreasing of face velocity, outside air heat transfer coefficient and flow resistance ofthree different spoiler forms fin tube are increasing; With the increasing of fin spacing,outside air heat transfer coefficient first increases and then decreases, the air flowresistance decreases, considering the convective heat transfer performance, optimal finspacing is around in3.5mm;the field synergy of Post vortex generator finned tubes,finned tube openings and straight field finned tube turn worse.Based on two-phase flow theory, pipe flow has been studied; through the application of two-phase mixture model and user-defined functions (UDF), the flow tube steamcondensation heat transfer process of air-cooled condenser tubes, considering the affectof different inlet steam flow, tube bundles for the tilt angle and other parameters, wasnumerically simulated, the results show that: along the inner tube the heat exchangerintensity decreases, pressure drop increases; the same angle of inclination, the influenceof heat transfer coefficient with inlet steam flow is related to the size of tube dip, the flowpressure drop becomes larger as inlet steam traffic increasing; With the increase of pipeinclination, tube heat transfer coefficient increases first, then levels off, the flowingpressure drop first decreases, then levels off, The most suitable tube bundle angle isaround60°.Therefore, through the study of inside and outside flow heat transfer characteristicsof the air-cooled condenser tube bundle, the conclusions can provide a theoretical basisfor the efficiency operation of air-cooled condenser and optimizing the parametersdesign.