The present study investigates the effects of duct corrugation angle and flow velocity on the convective heat/mass transfer characteristics in wavy ducts applied in a primary surface heat exchanger. Local heat/mass transfer coefficients on the corrugated duct sidewall are determined using a naphthalene sublimation technique. The flow visualization technique is used to understand the overall flow structures inside the duct. The corrugation angles of the wavy ducts are 145° and 130°, and the duct aspect ratio is fixed at 7.3. The Reynolds numbers, based on the duct hydraulic diameter, vary from 1,000 to 5,000. The results show that secondary vortex flow cells, called Taylor-Go¨rtler vortices, exist periodically in the wavy duct. Therefore, non-uniform distributions of the heat/mass transfer coefficients are obtained on the duct walls. On the pressure-side wall, high heat/mass transfer cell-shaped regions appear due to the secondary vortex flows for both corrugation angles. On the suction-side wall, the heat transfer coefficients are lower than those on the pressure-side wall. The wavy duct with the corrugation angle of 130° has the stronger strength of the secondary vortex cells resulting in higher heat/mass transfer rates on the duct wall because the sharp turn enhances the development of the secondary flow cells.

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