Heat Transfer in a Two-Pass Rectangular Rotating Channel With 45-deg Angled Rib Turbulators

Abstract

Experimental heat transfer results are presented in a two-pass rectangular channel (aspect ratio=2:1) with smooth and ribbed surfaces for two channel orientations (90 and 135 deg to the direction of rotational plane). The rib turbulators are placed on the leading and trailing sides at an angle 45 deg to the main stream flow. Both 45-deg parallel and cross rib orientations are studied. The results are presented for stationary and rotating cases at three different Reynolds numbers of 5000, 10,000, and 25,000, the corresponding rotation numbers are 0.21, 0.11, and 0.04. The rib height to hydraulic diameter ratio (e/D) is 0.094; the rib pitch-to-height ratio (P/e) is 10 and the inlet wall-to-coolant density ratio (Δρ/ρ) is maintained at 0.115 for all surfaces in the channel. Results show that the rotating ribbed wall heat transfer coefficients increase by a factor of 2 to 3 over the rotating smooth wall results. The heat transfer from the first pass trailing and second pass leading surfaces are enhanced by rotation. However, the first pass leading and the second pass trailing sides show a decrease in heat transfer with rotation. The result show that 45-deg parallel ribs produce a better heat transfer augmentation than 45-deg cross ribs, and a 90-deg channel orientation produces higher heat transfer effect over a 135-deg orientation.

Effect of rib spacing on heat transfer and friction in a rotating two-pass square channel with asymmetrical 90-deg rib turbulators

“…Such heat transfer trend was also observed in different types of ribs by Parsons at al. (1994) [20], Azad et al (2002) [21] and Al- Hadhrami et al (2003) [22].…”

Effect of rib height on heat transfer in a two pass rectangular channel (AR=1:4) with a sharp entrance at high rotation numbers

“…Azad et al [13] and Al-Hadhrami et al [14] performed rotating experiments in a 2:1 ribbed channel with rotation numbers ranging from 0.0 to 0.21. The results from Azad et al [13] and Al-Hadhrami et al [14] confirmed the results of Wagner et al [10,11] and Taslim et al [12]. Fu et al [15] performed experiments in ribbed channels with narrow aspect ratios.…”

Heat Transfer in Rotating Multipass Rectangular Ribbed Channel With and Without a Turning Vane

“…The effects of Coriolis and buoyancy forces were reduced comparing to the 90 deg orientation case. Azad et al [6] performed heat transfer experiments in a rotating two-pass rectangular ribbed channel with AR = 2:1 and P/e =10 at orientation angles of 90 deg and 45 deg with maximum rotation number of 0.21. Al-Hadhrami et al [7] obtained heat transfer data for the two-pass rectangular channel (AR = 2:1) with two channel orientations of 90 deg and 45 deg using 45 deg V-shaped ribs.…”

“…They impinge it on the LE and the side wall in the passage with radial inward flow (passage 2). The above flow conjectures and interpretations come from previous CFD simulations[1,6] and measurements[12][13][14].The effect of rotation is evaluated by the rotation number (Ro), defined as the ratio of the Coriolis force to the inertial force as shown belowThe combined effect of rotation and coolant temperature gradient is evaluated by the local buoyancy parameter (Bo^)rotation number Ro and channel-averaged buoyancy parameter Bo at each tested Reynolds number and rotational speed are shown inFig. 6.…”