4. Conclusion

3.3 The impact of rib roughness parameters

Boundary Layer Flows - Theory, Applications and Numerical Methods

Figure 6.

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The roughness parameters of corrugated channels involve relative rib height (e/b), relative rib pitch (p/b), and relative rib width (w/b) as illustrated later in Figure 6a. The impact of roughness parameters on the thermal-flow behavior of corrugated channels is presented in Figure 5. The computed Nu, f, and PEC are tested for different relative roughness heights which are presented in Figure 5a1, 5a2, and 5a3, respectively, with constant values of p/b and w/b. Generally,

corrugated channels have higher Nu than a smooth channel. It is observed that the Nusselt number increases monotonically with both rib height and Re. But there is a relatively small effect of rib height on the Nu at lower values of Re. At the same time, the friction factor varies positively with the relative rib height. While, there is an insignificant effect of Re on f, the variation of PEC (Figure 5a3) confirms that the diverse effect of friction factor exceeds the enhancement in transferred heat especially with an increase of Re. The influence of rib pitch of corrugation on Nu, f, and PEC of corrugated channels is illustrated in Figure 5b1, 5b2, and 5b3, respectively, for constant corrugation height and width. Decreasing the pitch results in an increase in the number of ribs for unit length and excites the secondary flow. Therefore, the thickness of boundary layer is decreased, and the rate of heat transfer is augmented. However, the flow impedance is increased due to the increase in the number of roughness elements which add extra friction to the flow stream. It appears that the influence of corrugation pitch is insignificant on the PEC as

(a) Different rib shapes of IOCC channels and the influence of rib shapes on the Nu, f, and PEC as presented in

(b), (c), and (d), respectively, for the different values of the Re.

The computational investigation of thermal-flow performance of turbulent flow in corrugated channels is carried out for the Reynolds number from 5000 to 60,000. The effects of rib arrangements, rib configurations, rib roughness parameters, and rib shapes are investigated. All layouts of corrugated channels showed a superior ability of exchange heat than that experienced by smooth channel. However, the pressure loss associated with corrugated channels is higher than that of the smooth ones. Furthermore, it is inferred that the arrangement of rib distribution, rib configuration, and rib roughness parameters has a pronounced effect on the thermal-flow performance of corrugated channels, while the influence of rib shapes seems to be small.
