Heat transfer enhancement in quasi-two-dimensional magnetohydrodynamic duct flows using repeated flow-facing wedge-shaped protrusions

Repeated flow-facing wedge-shaped protrusions are explored as a means to enhance the heat transfer behaviour in a quasi-two-dimensional magnetohydrodynamic duct flow. Quasi-two-dimensionality is achieved under a strong magnetic field which are prevalent in the cooling blankets of fusion reactors. Ranges of Hartmann friction parameters (50 ≤ H ≤ 500) and Reynolds numbers (1300 ≤ R e ≤ 3000) are investigated. The effect of blockage β (wedge height to duct height), pitch γ (distance between wedges) and wedge angle ϕ on heat transfer ratio HR and efficiency η are considered. A monotonic increase in HR with β is observed in the range of β investigated. It is possible to further improve HR by changing the geometric parameter to an optimal pitch and optimal wedge angle. Corresponding to each H there exists an optimal β , γ and ϕ where maximum η could be achieved. In contrast to the optimal β which showed a monotonic increase with H , optimal γ and ϕ showed a reversal in the trend after a critical H . Effectiveness of surface modification on the heated wall is also established through a net power analysis.