Numerical Investigation of Heat Transfer Characteristics of Ribs with Trenches in Gas Turbine Internal Cooling Channel

In this work, several trenches are placed in the ribs to reduce disadvantages of square ribs. These configurations open up some small extra passages for the coolant to remove the local vortices. Furthermore, the remained square pillars of the ribs act like pin-fins which promote horseshoe vortices. These vortices significantly enhance the heat transfer capability in the junction of pillars and endwall. To investigate the effect of trenches number and shape on the heat transfer capacity of the channel and flow characteristics, a parametric study of ribs with trenches is performed using RANS equations with the SST turbulence model. Furthermore, the staggered and in-line arrangements of ditches are studied. It is concluded that the staggered trenches show a higher Nusselt number than the in-line arrangement, but it comes with a higher friction factor. The parametric study resulted in a higher heat transfer efficiency index (HTEI) of the new designs than the square ribs. At Re = 26,500, the Nusselt number of 3 trenches with staggered arrangement increases by 41.9%. Moreover, a slight increase in friction factor combines with that to form a 31.9% increase in the overall Heat transfer efficiency index. The designs of 3 trenches with in-line arrangement come with a slight increase of 13.7% in Nusselt number; a decrease in friction factor of this design forms a 16.4% increase in Heat transfer efficiency index compared to the case of the original ribs.