Simulation Of Flow Field And The Reinforcement Of Heat Intensification In Coil-wound Tube Heat Exchanger

Coil-wound tube heat exchanger is a kind of high efficiency shell-and-tube exchanger,which has compact size,low impurities deposition,high operating pressure in tubes and high heat exchanging efficiency.This paper use SolidWorks to set up the physic model of coil-wound tube heat exchanger and use Fluent to simulate the flow field in the heat exchanger.And we study the influence on the inner flow and heat exchanging characteristics caused by different structures of coil-wound tube heat exchanger.Aiming at the higher pressure drop at the shell side of coil-wound tube heat exchanger,this paper put forward a new coil-wound tube heat exchanger which equips drop shape coil-wound tubes and conduct the simulation.This can provide some advice to the design and exploitation of coil-wound tube heat exchanger.(1)Studied the flow characteristics of shell side flow caused by the changed cross sections and inlet velocities.The results indicates that,in the pipeline,the inner tube is 11.7% higher than the PEC index of the outer tube due to the small winding radius,and has better heat transfer effect.At the shell side,radial flow helps to promote the heat exchange between the outer cold fluid and the heat transfer tube wall because there is a radial flow between the winding tube and the tube moving from the outer high speed region to the inner layer winding tube and the radial flow rate increases with the inlet flow rate of 0.7m/s,and the radial flow rate is 1.2m/s.With the increase of the inlet flow rate,the turbulence intensity of the shell side is higher,the inlet flow velocity is 0.5m/s,the turbulent kinetic energy is 0.03m2/s2,and the heat transfer effect of the shell side is improved.(2)This paper set up three different models of parallel,crossing banding and derangement ways of winding pipes,studied the performance of shell side flow and heat exchanging procession caused by the changed arrangements of tubes and inlet velocity.The results indicates that cross-arrangement with a higher resistance coefficient,about 10% higher than the other two arrangements.Compared with the parallel tubes,because of the channeling effect of cross banded tubes,there is higher radial velocity among the tubes which leads to the fluid outside and beside the coil-wound tubes mix more intensively,smaller area of low velocity zone after tubes,stronger heat delivery,a 25% higher PEC number,and more uniform distribution of temperature.(3)Heat exchanger for new type of droplet-shaped heat transfer tubes.The results shows that,compared with the heat exchanger of the ordinary tube,the fluid distribution in the tube of the water droplet-shaped heat transfer tube is more uniform;High-speed fluid and high-temperature fluid distribution more uniform,is conducive to the heat transfer;At the shell side,although the Nuosail number Nu of the heat exchanger of the drop tube has a certain decrease,the resistance coefficient f and the pressure drop are greatly reduced.When the inlet flow rate is 0.4m / s,the Nusselt number Nu of the drop tube is 94.2% of the pipe,and its resistance coefficient f is only 75% of the tube,PEC index increased by 5%,greatly reduced due to Shell pressure loss caused by resistance.