Numerical Simulation Of Flow And Heat Transfer In Heat Exchanger Tubes With Modular Twisted Tape

Heat transfer enhancement technology has very important significance to improve the heat transfer performance and decrease the weight of heat exchange equipment, the related basic and applied research of twist tape has caught much attention as one of heat transfer enhancement measures.Mathematical model and physical model of many insert heat exchanger tubes were established, the insert include: twisted tape of different clearance ratio and twist ratio, modular twisted tape which is made up spiral and straight. The Renormalized Group(RNG) k-εturbulence model was used to simulate the heat exchange tube. The velocity field ,temperature field ,pressure field and streamlines of heat exchanger tubes are obtained and the heat transfer and pressures drop characteristics are investigated through the software fluent. On this basis, the comprehensive performance is respectively derived through an integrated performance evaluation criteria, some important results and conclusions are as follows:①The Nu number and f number of the heat transfer tube decreased with the increasing of CR and Y. The heat transfer tube which fit with twist tape of clearance rate CR=0.1and twist ratio Y =5 has the most obvious heat transfer enhancement effect and hold the best heat transfer performance.②The heat transfer efficiency and pressure loss are increased with the increasing of spiral length for heat exchanger tubes with modular twisted tape, and heat exchanger tubes have the best heat transfer performance while the length of spiral accounts for 1/4 of the length of modular twisted tape. The width of straight have no meaning for Nu number, however f is increased with the increasing of width. For the tubes with the modular twisted tape which the straight and twisted placed intevail, the tubes have the best heat transfer performance while the straight is 1.5 or 2 times as length as spiral.③The modular twisted tapes have better heat transfer performance than common twisted tapes in the whole rang of Re number simulated. Due to the strong swirl caused by the insert in the heat exchanger, the pressure loss is huge while at high Re number, especially when Re>25000, this would impair comprehensive heat transfer performance. If the load is limited, the insert-tape heat exchanger is not suitable.