| Twisty flow heat exchanger is a new type of shell and tube heat exchanger,study of its heat transfer enhancement and flow resistance reduction performance is of great significance to energy conservation and emission reduction and energy efficiency improvement.In this paper,based on the research of heat transfer enhancement technology of twisty flow heat exchanger,the flow and heat transfer characteristics inside and outside the tube of twisty flow heat exchanger with drop shaped tube and twisted oval tube are analyzed by numerical simulation and theoretical analysis.The general rule of the influence of the new tube bundle on the heat transfer enhancement and flow resistance reduction performance of the twisty flow heat exchanger is summarized.The processing and assembling technology of trapezoid-like tilted baffle,twisted oval tube and drop shaped tube are discussed.The main research contents and results are as follows:The convection heat transfer coefficient of the shell side fluid in the twisty flow heat exchanger with drop shaped tube increases with the increase of ratio of the axial length.Compared with circular tube,the drop shaped tube can strengthen the shell side fluid turbulence and reduce the flow boundary layer of the tube wall.The synergistic of velocity and temperature gradient is better than circular tube,and the convection heat transfer coefficient is 32.81%-33.62%higher than circular tube.The synergistic of velocity and pressure gradient is worse than circular tube,the pressure drop increased than circular tube,but the comprehensive performance is better than circular tube,which is 18.65%?21.36%higher than circular tube.The variation of fluid performance in drop shaped tube is consistent with shell side,and the convection heat transfer coefficient is 24.35%?31.49%higher than circular tube,the comprehensive performance is 9.39%?20.37%higher than circular tube.The variation of fluid performance in the tube of twisty flow heat exchanger with twisted oval tube is consistent with drop shaped tube.The convection heat transfer coefficient is 26.32%?32.42%higher than circular tube,and the comprehensive performance is 20.98%?22.13%higher than circular tube.The twisted oval tube has good continuous spiral-oriented flow line,and the combination with the trapezoid-like tilted baffle arranged in orthogonal way has good flow diversion effect on shell side fluid.The convection heat transfer coefficient is 17.08%-20.13%higher than circular tube,the synergistic of velocity and pressure gradient is better than circular tube,the pressure drop is 15.17%-18.05%lower than circular tube,and the comprehensive performance is 31.68%-36.84%higher than circular tube.The essential mechanism of heat transfer enhancement and flow resistance reduction is revealed by combining the dimensionless factor ? of flow direction,the oblique watershed distribution,and the field synergy principle of shell side fluid.The fluid performance in tube side of twisty flow heat exchanger based on the new tube bundle is greatly affected by the single factor of tube bundle structure and the shell side fluid performance is affected by the two factors of tube bundle and baffle structure.In order to achieve the dual purposes of heat transfer enhancement and flow resistance reduction,the synergistic effect of the combination of new tube bundles and trapezoid-like tilted baffle on shell side fluid must be emphatically studied.The tube holes and outer contour of trapezoid-like tilted baffle were processed by"projection method",the circular tube and trapezoid-like tilted baffle were assembled by horizontal integral method,and the tube end joints were welded first and then expanded.Both twisted oval tube and drop shaped tube are formed by two-step that of extrusion and twisting of circular tube.The assembly of new tube bundle and trapezoid-like tilted baffle is completed by the"maximum outer circle method".The twisty flow heat exchanger shall be tested for leakage after assembly. |
PDF Full Text Request