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Journal of Enhanced Heat Transfer

Impact factor: 0.400

ISSN Print: 1065-5131
ISSN Online: 1563-5074

Journal of Enhanced Heat Transfer

DOI: 10.1615/JEnhHeatTransf.v10.i4.20
pages 363-378

Pressure Drop Characteristics in a Rib Roughened Rotating Square Duct with a Sharp 180° Bend

Santosh V. Prabhu
Department of Mechanical Engineering, Indian Institute of Technology, Bombay Powai, Mumbai – 400 076, India
R. P. Vedula
Department of Mechanical Engineering, Indian Institute of Technology, Bombay Powai, Mumbai – 400 076, India

ABSTRACT

An experimental investigation was carried out to study the local pressure drop distribution in a square cross-sectioned channel with a sharp 180° bend rotating about an axis normal to the free-stream direction in the presence of rib turbulators. The sharp 180° turn was obtained by dividing a rectangular passage into two channels using a divider wall with a rounded tip where the flow negotiates the turn. The study was conducted for three ratios of divider wall thickness to hydraulic diameter (W/D), 0.24, 0.37, and 0.73. The rib height-to-hydraulic diameter ratio (e/D) was maintained constant at 0.1 with a constant pitch-to-rib height ratio (P/e) of 10. The ribs are configured in a staggered arrangement with angles of 60° and 90° to the main-stream flow, with ribbed surfaces forming the leading and trailing surface during rotation. The Reynolds number was varied from 10,000 to 17,000, with the rotation number varying from 0–0.38. The pressure drop distribution normalized with the mainstream pressure head being presented for the leading surface, trailing surface, and outer surface. The friction factor is less sensitive to the variations in the W/D ratio for a given rib angle, both in the stationary and rotating conditions. The pressure drop distribution for the 90° ribs remains practically unchanged under conditions of rotation. However, the pressure drops for the 60° ribs are smaller than without rotation. At the highest rotation number, the pressure drop obtained by both 60° and 90° ribs are comparable.