**Acknowledgements**

breakthroughs in span at decreased Reynolds numbers, and they also noticed that the

Abu-Mulawah et al. [80] have also reported on the effect of step height on turbulent mixed convection flows over a backward-facing step. Abu-Mulawah [81] noticed that the highest local Nusselt number at the reattachment region for the backward-facing and forward-facing

The turbulent fluid flow and heat transfer of a mixed convection boundary-layer of air flowing over an isothermal two-dimensional, vertical forward step was experimentally investigated by Abu-Mulaweh [82]. He studied the effect of forward–facing step heights on local Nusselt number distribution, as shown in Fig. 7. The results indicate that the Nusselt number increases with the increase of step height, and the highest value is obtained at the reattachment region. The present results indicate that the increase of step height leads to an increase in the intensity of temperature fluctuations, the reattachment length transverse velocity fluctuations and the

Heat transfer and nanofluid flow through annular pipe over a backward-forward facing step has been presented in this chapter. The effect shape of geometry on thermal performance is clearly seen in experimentally and numerically studies in the literature. The results show that

transverse direction of separation was slow compared with a short time scale.

**Figure 7.** Local Nusselt number variation downstream of the step.

turbulence intensity of the stream.

306 Heat Transfer Studies and Applications

**7. Conclusion**

steps in turbulent natural convection flow along a vertical flat plate.

The authors gratefully acknowledge High Impact Research Grant UM.C/625/1/HIR/ MOHE/ENG/45 and UMRG Grant RP012D-13AET, Faculty of Engineering, University of Malaya, Malaysia for support to conduct this research work.
