Numerical And Experimental Investigation On Flow And Heat Transfer Inside Serpentine Cooling Passages With Rib Turbulators

To reveal the effects of channel shape, rib distribution and other factors on flow and heat transfercharacteristics, many experiments and numerical researches have been made on single row and ser-pentine passages. In the present study, get changes of the flow and heat transfer characteristics insideserpentine passages with ribs through changing inlet Renalds number, according to a certain aero en-gine turbine blades.Five experimental models of serpentine passage were made. For each experimental model, thestatic pressure, wall temperature and gas flow temperature along passage flow direction under differ-ent Reynolds number were measured. The results show that the convective heat transfer coefficientreaches to maximum value after the fluid flows pass several ribs. The less flow drain out of outlet1,the convective heat transfer coefficient will be better downstream when Reynolds number is between3800and22900. According to the experimental data, the relationships for Nusselt number vs Rey-nolds number and for pressure loss coefficient vs Reynolds number.Numerical simulations were also made to analyze the flow field, temperature field and heattransfer distribution.For five different groups of ribs arranged in the range of30to90degree, the wall temperature,pressure loss coefficient, heat transfer coefficient and Nusselt number were numerically simulated.The results show that when ribs angle is smaller, augment of pressure loss coefficient is slower andthe pressure loss is smaller in the same boundary condition. The heat transfer coefficient in the sidewhere ribs intersect at obtuse angle along incoming flow side is higher than the other side, and as thereduction of rib angle, the difference becomes bigger. Because existing of outlet holes, heat transfercoefficient in the right side of passages is significantly higher than the left side. The higher convectiveheat transfer coefficients are achieved for rib angle of30°~70°. Although pressure loss is smallerwhen rib angle is smaller, unevenness of heat transfer coefficient distribution becomes serious, so thatthe smaller rib angles are not suitable to application.Eight rib pitches in the range from s/h=3to s/h=14were chosen for numerical investigation. Theresults show that if s/h is too small (s/h5), the vortex between adjacent ribs is compact and steady.The mainstream have no other contact point with wall, so vortex exchange momentum and energywith mainstream only by diffusion. On the contrary, if s/h is too big, mainstream cannot achieve newturbulence in time after detached area, so thermal boundary layer rebuild and get thick gradually. Pressure loss gets augment first and then decreases when s/h is between5and10. The best s/h shouldbe between7and10, in this region, vortex in separation zone after rib is incompact, fall off and mixwith mainstream periodically. This will enhance energy transfer between wall and flow. Mainstreamand wall retouch after separating zone, then impact next rib, it will enhance heat transfer after sepa-rating zone significantly.