Numerical investigation of flow and heat transfer in rectangular channel with teardrop dimple/protrusion

The flow and heat transfer characteristics of teardrop dimple and protrusion with different eccentricities were firstly investigated and compared with hemispherical dimple/protrusion in the present study. The realizable κ-ε turbulent model coupled with enhanced wall function was adopted and the grid independence validation was performed. The results of flat cases were certified by the empirical data which confirmed that the numerical method introduced is acceptable. The result shows that the flow covers the teardrop surface easily and impinges onto the rear section with more energy in the teardrop dimple/protrusion with PE compared with hemispherical dimple/protrusion. Nu/Nu0 decreases monotonously as Re increases and it increases when e/Dh increases from −0.4 to 0.4 for teardrop protrusion. While Nu/Nu0 decreases slightly when e/Dh varies from 0 to 0.1 and it increases when e/Dh is larger than 0.1 for teardrop dimple. f/f0 decreases as Re and e/Dh increases in the teardrop protrusion cases. But for teardrop dimple cases, it increases with Reynolds number when e/Dh < 0.2 while it has not changed much when e/Dh = 0.2 and it decreases when e/Dh > 0.2. The value of f/f0 increases slightly when Reynolds number varies from 7000 to 9000 for e/Dh = 0.3. TP increases gradually as the center moves downwards for the teardrop protrusion. However, the value of TP shows the minimum when e/Dh = 0.1 and it increases as e/Dh > 0.1 for teardrop dimple. TP shows the maximum for teardrop dimple and protrusion when e/Dh = 0.4. From the view of heat transfer enhancement and energy savings, the teardrop dimple/protrusion shows good performance for lower Reynolds number.