Forced convection heat transfer in rectangular channels is enhanced by aeroelastically fluttering thin reeds extending over the channel span. The resulting small‐scale vortical motions substantially increase local heat transfer at the channel walls and mixing between the wall thermal boundary layers and the channel's core flow. Mechanisms associated with evolution of these small‐scale motions and their thermal effects are experimentally studied in a channel of width W, span 5W, and length 50W. Reed effects on heat transfer are characterized at Reynolds numbers (Re) of 2000, 7000, and 12,000 using embedded thermocouple arrays, and related to small‐scale motions by particle image velocimetry and hot‐wire anemometry. Reed‐induced small‐scale motions increase turbulent kinetic energy, increasing the global Nusselt number (by up to 145% at Re = 7000), with enhancement being sustained even when the base flow becomes fully turbulent (Re = 12,000). Enhancement is also demonstrated for fin arrays. Single‐reed computations show the effect of reed length on enhancement. Computations with two reeds, one downstream of the trailing edge of the other, predict heat transfer enhancement significantly greater than twice the single‐reed result, and point the way to use of a streamwise array of reeds in long channels. A techno‐economic analysis for an air‐cooled condenser suggests that fluttering reeds can be economically justified for a range of operating conditions.
Dry cooling, where forced air is the heat transfer medium, is a preferable cooling method in arid locations lacking readily available process water. However, such locations often experience high ambient temperatures that limit the effectiveness of air cooling. The objective of this study is to quantify the economic and energetic benefits of heat transfer intensification via the implementation of aeroelastically fluttering reeds to the air‐cooled condenser of a methanol distillation column. Condenser size and performance, regarding recovered methanol and required fan power, is evaluated across condenser operating temperatures (Tcond) from 60 to 62°C and heat transfer coefficients (U) Ubase–2Ubase for a range of inlet air temperatures based on ambient temperature data from Yuma, Arizona. Under typical design sizing, condenser capital cost was reduced by 6%–35% (1.3Ubase–2Ubase) and nominal methanol recovery was increased from 0.26% to 0.38% (Tcond = 62–60°C). At optimized condenser size, all enhanced U and Tcond pairs increase methanol recovery and reduce fan power costs compared to the optimal Ubase reference. Overall, using enhanced heat transfer to maintain condenser temperature under a wider range of inlet conditions, rather than to reduce operation temperature, produces more favorable performance. Methanol price is not a determining factor in which pairs are profitable. Analysis was repeated for a global warming scenario, revealing more valuable improvements under elevated temperatures. Energy savings from condenser improvement to a methanol production system are not significant with respect to an optimized conventional system. Unit economic and energetic incentives suggest implementation of fluttering reeds may be justified in other applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.