CFD Analysis Of The Enhanced Heat Transfer Mechanism Of Heat Exchange Tubes Based On Field Synergy And (enburn) Dissipation

Energy conservation has attracted many attentions of the contemporary society with the growing global energy crisis.They have become a new task to improve the efficiency of heat exchanger and research the new technology of heat transfer enhancement,because the heat exchange equipment is widely used in industrial production.The passive heat transfer enhancement technology is widely applied in industry,because additional power consumption is not required for it.The passive heat transfer enhancement method usually achieves the effect of heat transfer enhancement by changing the surface geometry of the tube or inserting the material inside the tube.The round tube,oval straight tube,twisted oval tube,the tube inserted with twisted tape and the tube inserted with grating twisted tape have been simulated by using CFD(Computational Fluid Dynamics)with water as flow medium in this paper.Every tube was carried on the analysis of thermodynamics.The synergy principle and entransy dissipation theory are applied to the optimum design of heat exchange tubes,explore the mechanism of heat transfer enhancement and provide theoretical basis for industrial application.Numerical simulation results show that:(1)The number of Nu and f increase with the decrease of the number of b/a in oval straight tube and twisted oval tube,so it is beneficial to heat transfer enhancement,but also increases the flow resistance loss.At the same time,the average synergy angle between velocity and temperature gradient gradually reduces,the average synergy angle between velocity and pressure drop gradient gradually increases.The number of entransy dissipation decreases with the tube more flat,it means that the heat transfer efficiency gradually increases with the tube more flat.(2)The number of Nu and f increase with the increase of twisted angle of the tube when the length of twisted oval tube is constant value,the synergy degree between velocity and temperature gradient gradually optimizes,and the synergy degree between velocity and pressure drop gradient gradually deteriorates.The number of entransy dissipation decreases with the increase of twisted angle of the tube.It means that the heat transfer effect gradually optimizes with the increase of twisted angle of the tube.(3)The number of Nu and f increase with the increase of the number?(the ratio between the width of twisted tape and the equivalent diameter of tube)in the tube inserted with twisted tape.The average synergy angle between velocity and temperaturegradient gradually decreases with the increase of the number ?,but the average synergy angle between velocity and pressure drop gradient gradually increases.The number of entransy dissipation decreases with the increase of the number ?.The heat transfer effect will be strengthened with the increase of number ?.(4)The number of Nu and f gradually increase,the average synergy angle between velocity and temperature gradient gradually reduces,the average synergy angle between velocity and pressure drop gradient gradually increases and the number of entransy dissipation reduces with twisted angle of twisted tape gradually increases in the tube inserted with twisted tape.(5)The aperture ratio of twisted tape directly affects the comprehensive effect of heat transfer enhancement.The number of Nu increases first and decreases later,and the number of f gradually decreases with the increase of aperture ratio.The synergy degree between velocity and temperature gradient optimizes first and deteriorates later,and the synergy degree between velocity and pressure drop gradient gradually optimizes.At the same time,the number of entransy dissipation decreases first and increases later.Therefore,the tube with an appropriate aperture ratio of twisted tape owns the optimal heat transfer enhancement effect.