Flat plate convection heat transfer enhancement via a square rib. (January 2017)

• Record Type: Journal Article
• Authors: Fouladi, F.; Henshaw, P.; Ting, D.S.-K.; Ray, Steve
• Is Part Of: International journal of heat and mass transfer. Volume 104(2017:Jan.)
• Page Start: 1202
• Page End: 1216
• Publication Date: 2017-01
• Subjects: Square rib -- Hot-wire -- Heat transfer -- Turbulent stress -- Energy spectra; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2016.09.023
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: A leading edge rib attached to a heated flat plate with parallel airflow was investigated. Heat transfer was measured using a novel, integrated heat transfer device. Rectifying the raw velocity data improved the accuracy of X-probe measurements. The flow reattachment point after the rib was located based on heat transfer and velocity. Enhanced turbulence is responsible for heat transfer enhancement due to the rib. Abstract: Flow and convection heat transfer downstream of a square rib on a flat plate were experimentally investigated inside a closed loop wind tunnel. Heat transfer augmentation for the ribbed plate compared to the smooth plate ( Nu / Nu 0 ) was studied at Reynolds numbers, based on the rib's height ( H = 1 cm), of Re H = 1.3 × 10 3, 2.6 × 10 3, 5 × 10 3 and 6.3 × 10 3 . The ribbed plate presented an enhancement in heat transfer ( Nu / Nu 0 > 1) at all studied Reynolds numbers. A trend of decreasing enhancement with increasing Re H was observed, with the largest decrease in Nu / Nu 0 occurring when Re H increased from 1.3 × 10 3 to 2.6 × 10 3 . The remarkable enhancement in Nu at the lowest Reynolds number (Re H = 1.3 × 10 3 ), compared to higher Re H, was presumably due to the transition of the boundary layer regime from laminar to turbulent. To investigate the effect of the rib on the flow over the surface, flow and turbulence structures were measured using an X-probe hot-wire anemometer. It appears that the turbulence generated by the rib ( u rms, v rms, uv ‾ ) is the most influential factor on enhancing the heat transfer from the surface. Also, the normal velocity ( V ) created downstream of the rib seems to be somewhat effective in extracting heat from the surface, while the streamwise velocity ( U ) was blocked by the rib. The energy spectra of normal velocity fluctuations showed traces of vortex shedding from the rib's edge at Re H = 1.3 × 10 3 .