Numerical Research On Integrated Heat Transfer Performance Of The New Inner-ribs Tubes

Enhanced heat transfer technology has a great significance for the development of new energy technologies and energy saving. Longitudinal vortic heat transfer enhancement is one of passive methods on heat transfer enhancement, in the field of heat transfer, which shows a superb performance in heat transfer. In this paper, two new enhanced tubes——Intermittent Transverse ribs tube and Curved ribs tube, which are developed based on field synergy theory and longitudinal vortex enhanced heat transfer. The simulation work on the new kind of heat transfer tube is carried out, and effects of heat transfer theory and geometric parameters on the heat transfer performance are analyzed together with the comparative evaluation of the overall heat transfer performance. The correlations for indicating the Nu and f of the new type of heat transfer tube are fitted according to the numerical results. The results showed that:1) Intermittent Transverse ribs tube: A strong vortex in the longitudinal direction of the spiral is induced in the near-wall region due to the presence of the ribs, which in turn achieved a heat transfer enhancement. The fluid near the wall has a certain turbulence intensity which could strengthen heat transfer when Re is about 500. The value of Fc / Fcs ranges from 2.45 to 3.56 when compared with plain tube with Re of 4000, and its comprehensive evaluation coefficient can reach up to 2.5. For Re < 2300, the relative enhancement of heat transfer performance and the drag coefficient can reach 2.5 to 5.5 times and 1.5 to 3.3 times of that for plain tube respectively resulting in a high PEC of 2.2 ~ 4.1. The PEC can reach 1.24 ~ 2.25 when Re > 2300. The correlations for indicating the Nu and f are fitted using multiple linear regression method based on the results. The range of application is for Re = 500 ~ 40000, Pr = 2 ~ 200.2) Curved ribs tube: A strong longitudinal swirl can be induced effectively because of the curved ribs, resulting in an effective heat transfer enhancement; the fluid in the pipe has shown a turbulent state when Re > 500. For Re < 2300, the relative performance of enhanced heat transfer factor and drag coefficient of Curved ribs tube is 2.9 to 7.0 times and 1.4 to 3.6 times of that for plain tube respectively And its PEC can reach 2.6 to 4.6, and 1.2 to 2.3 for Re < 2300 and Re > 2300 respectively. When Re < 2300, the overall heat transfer performance for the inner tubes bent rib is greater than that of the intermittent stripes and ribbed inner tube. When Re > 2300, the heat transfer performance is better with intermittent ones. The correlations for indicating the Nu and f are fitted for range of application of Re = 500 ~ 40000, Pr = 2 ~ 200.