Comparison between EVM and RSM turbulence models in predicting flow and heat transfer in rib-roughened channels

Experimental validation of large eddy simulations of flow and heat transfer in a stationary ribbed duct

“…The accurate prediction of these two curves is difficult to achieve because of the recirculation of flow near the ribs and the localized secondary flow effect. Many computational studies have attempted to correctly predict this smooth wall heat transfer effect using different turbulence models with little success (Ooi et al, 2002;Arts et al, 1997;Saidi and Sundén, 2001;Sleiti and Kapat, 2004). In the 180°bend region, a mass transfer experiment by showed results for a channel with geometry similar to that of the present study (e/D h = 0.094, P/ e = 10) with a Reynolds number of 30,000.…”

“…A comparison between effective viscosity models and differential second-moment closure (DSM) models in two dimensions by Iacovides and Raisee (2001) showed that, even though the DSM model could account for the anisotropic turbulence, it could not completely reproduce the heat transfer in all cases. A study comparing several k-e models and k-x models with a Reynolds Stress Model (RSM) with enhanced wall treatment showed good agreement between the RSM results and experiments in predicting mean flow and smooth side wall heat transfer with some differences in predicting ribbed wall heat transfer (Sleiti and Kapat, 2004).…”

Optimum design of a channel roughened by dimples to improve cooling performance

“…Modifications of source terms in streamwise momentum and energy equations have been done to adopt the periodic boundary conditions to calibrate the gradual changes of temperature and pressure, respectively, as described by Kim and Choi [13]. Although the different turbulence closure models have different capabilities to predict the flow field [16], the present study uses shear stress transport (SST) turbulence model which has also been reported in Refs. [13,14].…”

Conjugate Heat Transfer in Ribbed Cylindrical Channels

“…Figure 18. Cracks in the central cooling channels [16] In this way, the effect generated by increasing the internal cooling zone produces an increment in the useful life of the blade, since the useful life of gas turbine blades is reduced to half with every 10-15 °C rise in metal temperature [2]. On the other hand, the use of ribs increases the heat transfer, generating an increase in thermal gradients at internal surface of cooling channels.…”

“…However, in order to achieve this, it is necessary that the gas turbine operates at high compression pressure ratios as well as high turbine inlet temperatures (TIT), but these operating conditions generate thermal consequences or degradations in the gas turbine components that are exposed to the high temperatures, like blades and vanes of the first stage. For this reason, it is necessary to have an internal cooling system in gas turbines to avoid the reduction of the useful life of their hot components, since the useful life of turbine blades is reduced to half with every 10 -15 ºC rise in metal temperature [2]. Nowadays basic methods exist, which improve the gas turbines operating conditions, having as a result improvements of the external cooling [3], where the use of micro-jets with smaller diameters enhanced the overall heat transfer coefficient, or internal cooling where square ribbed channels are employed to study the thermal behaviour of the flow inside the channel [4], turbulence promoters with different geometries to study the temperature distribution in the gas turbine blades [5].…”