Numerical Simulation On Heat Transfer And Flow Resistance Performance And Fouling Characteristics Of Spiral Grooved Tube

With the rapid development of process industry including chemical engineering, petroleum, light industry, etc, environment, ecology and social problems are increasingly aggravating, centered on power sources. As the energy shortage aggravating day by day, countries all over the world are concentrate on searching new energy and ways of saving energy to ease the situation of energy shortage. Heat exchanger was widely used in regions such as metallurgy, motion, nuclear energy, refrigeration, chemical engineering, petroleum, aviation, rocket, and astronavigation and so on. All kinds of Enhanced heat transfer technologies were widely used in heat-exchange equipment, especially the extensively implementation of enhanced tube. Spiral grooved tube, a kind of enhanced tubes, caused great attention and widely study all over the world because of its good double-sided heat transfer and machining property, which was superior to other heat transfer components. Although many scholars had studied lots of spiral grooved tubes, enhanced heat transfer mechanism and fouling characteristics of spiral grooved tube was not lucidity yet.So 3D numerical simulation on single-phase convective heat transfer performance and turbulent flow characteristics in tube-side was researched based on the Fluent for spiral grooved tubes and a smooth tube. The pipe flow and heat transfer of spiral grooved tube was described exactly. The enhanced heat transfer mechanism of spiral grooved tube was revealed in microscopic point of view. Influence laws of heat transfer and flow resistance performance created by groove depth e, pitch p, groove width b, number of thread n, Re and properties of the working medium were analyzed systematically. Through regress of numerical simulation data, the correlative expression of Nu and f was obtained. At the same time, numerical simulation on fouling performance in tube-side was also researched based on the Fluent for spiral grooved tubes and a smooth tube. Influence laws of fouling performance created by groove depth e, pitch p, groove width b, Re and particle diameter were analyzed systematically. The main conclusions of the paper are as follows:1,Heat Transfer and Flow Resistance Performance (1) Numerical simulation results of heat exchange tube fit empirical formulary ones well, which means numerical simulation on heat transfer and flow resistance performance in tube-side based on the Fluent for heat exchange tubes is feasible and could meet the engineering requirements.(2) Single-phase convective heat transfer performance and turbulent flow characteristics in tube-side was well simulated based on the Fluent for spiral grooved tubes, and the enhanced heat transfer mechanism of spiral grooved tube was revealed in microscopic point of view. Conclusions obtained by numerical simulation are consistent with the ones obtained by scholars'experimental research, which lay the foundation for numerical simulation of spiral grooved heat exchanger.(3) Under the same condition, heat transfer coefficient K, nusselt numble Nu, pressure drop AP and resistance coefficient f increased along with the increasing of groove depth e, decreased along with the increasing of pitch p, number of thread n and groove width b. Nu increased but f decreased along with the increasing of Re.(4) Under the same condition, Nu relates to properties of the working medium, but f doesn't. Enhanced heat transfer efficiency of spiral grooved tube is higher with lower viscosity working medium.(5) The nusselt numble of all spiral grooved tubes is greater than smooth tube one, and enhanced heat transfer efficiency of spiral grooved tube varies with its structure parameter. The nusselt numble of spiral grooved tubes, with deeper groove depth and smaller pitch and width, could be up to twice as the smooth tube, but the resistance coefficient might be 10 times as the smooth one at the same time. Enhanced heat transfer in tube-side is at the cost of resistance.(6) Through regress of numerical simulation results, the nusselt number and resistance coefficient of single-phase convective heat transfer in spiral grooved tubes was obtained.2,Fouling Performance(1) Local pipe scale is serious in smooth tube, while relatively better in spiral grooved tube.(2) In the main region, the situation of pipe scale in smooth tube has little difference with in spiral grooved tube. While in the near wall region, the situation of pipe scale in the former is obviously serious than in the later, and back flow region is more serious than incoming flow region.(3) Gravity has big effect on pipe scale in smooth tube, but little effect in spiral grooved tube because of the role of spiral groove.(4) Under the same condition, the spiral grooved tubes, with smaller groove depth and pitch and larger width, at lower Reynold number flow, could have better anti-fouling performance.(5) Fouling performance of spiral grooved tube relates to the particle diameter. The smaller the particle diameter is, the better the fouling performance could be.