Numerical Simulation And Entropy Generation Analysis On Tube-side Flow And Heat Transfer Of Inward Helical Corrugated Tube

Energy shortage is now one of the most urgent problems facing the world, which mainly comes from the inappropriate utility of energy resources. In order to increase the effectivity of energy utility, decrease product cost as well as reduce pollution, developing novel, high efficient and environment-friendly heat exchangers has become one of the most important research areas. This thesis aims at promoting the heat transfer enhancement for heat exchangers, and mainly focuses on the following contents:(1) The CFD numerical simulation software is used to study the influence of inlet Reynolds number Re, helical corrugated height H and helical corrugated pitch P on the tube-side flow and heat transfer characteristics. The results show that heat transfer performance is enhanced by increasing Re and H and by decreasing P, resistance performance is enhanced by increasing Re and P and by decreasing H.(2) Local fluid flow and heat transfer characteristics are investigated to reveal the mechanism of heat transfer enhancement in the tube side of inward helical corrugated tube. The results show that the helical corrugated component can increase the turbulence of fluid flow, and intense the fluid mixture and heat transfer inside the flow. As a consequence, the overall heat transfer performance is promoted.(3) The fluid flow and heat transfer characteristics of inward helical corrugated tube and inward corrugated tube are compared. And the results show that these two kinds of tubes have a resemblance in heat transfer performance. However, the helical tube has the better resistance performance and overall heat transfer performance. Besides, the helical corrugated parts can create a continuing disturbance in fluid flow, while the corrugated parts can only bring in discontinuing one, which explains the fact that the helical tube has a better fluid flow and heat transfer performances.(4) The entropy generation analysis method is applied to investigate the irreversibility of fluid flow and heat transfer in inward helical corrugated tube. The result show that the overall irreversibility, irreversibility due to heat transfer and irreversibility due to fluid friction are increased by increasing Re and H and decreasing P. And H has the strongest influence on irreversibility, followed by Re and P.(5) The irreversibility of fluid flow and heat transfer in inward helical corrugated tube and inward corrugated tube is compared. The results show that these two kinds of tubes have a resemblance in the overall irreversibility and the irreversibility due to heat transfer, while the helical tube has lower irreversibility due to fluid friction.