Internally enhanced surfaces such as micro-fins are an important class of heat transfer enhancement in commercial applications such as air conditioners and refrigerators. One typical goal of micro-fin design is to increase heat transfer with a minimum pressure-drop penalty (to increase the efficiency of heat transfer). Normally, researchers analyze the macro relationship between the efficiency of heat transfer and micro-fins to obtain correlations. The correlations reveal how newly designed geometries, i.e., width, height, shape, angle, etc., affect the heat transfer and pressure drops but are not predictive for new geometries because the detailed flow physics are not identified [1]. Very few studies have explored the link between flow characteristics and heat transfer/pressure drops both experimentally and numerically. The detailed time-resolved characteristics of flow near the wall around the micro-fins are not well understood because experimental and numerical data are limited.The current study proposes a numerical method with ANSYS Fluent to collect and analyze the relationships between the flow patterns and heat transfer/pressure drops on a microfin enhanced surface. The fin structure matched the one used by Webb et al. [2] and was manufactured on the top of the copper block through micro-machining. We utilized a large eddy simulation (LES) with a localized dynamic kinetic energy subgrid-scale model (LDKM) to predict the flow patterns. The authors were aware of very few systematic studies in the literature on implementing LES in wall-bounded flows with heat transfer/pressure drops on microfin enhanced surfaces. Furthermore, a commercial, telescopic, particle image velocimetry (PIV) system was used to capture flow characteristics for validation. PIV is a powerful tool used in many configurations. However, it is rarely used to collect flow characteristics near heat transfer fins. Therefore, both computational and experimental entries will be submitted for the competition.Flow visualization images are good tools to illustrate the detailed time-resolved flow patterns. It is convenient to reveal the relationships by showing the zoom-in images frame by frame with necessary descriptions. The flow visualization images with high quality help the researchers to figure out the physics and mechanics driving the performance of the micro-finned surfaces.Reference[1] Li P, Campbell M, Zhang N, et al. Relationship between turbulent structures and heat transfer in microfin enhanced surfaces using large eddy simulations and particle image velocimetry[J]. International Journal of Heat and Mass Transfer, 2019, 136: 1282-1298.[2] Webb R L, Narayanamurthy R, Thors P. Heat transfer and friction characteristics of internal helical-rib roughness[J]. J. Heat Transfer, 2000, 122(1): 134-142.

Flow Pattern on Microfin Enhanced Surfaces (Images)

Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2021/volume/85284

ASME 2021 Fluids Engineering Division Summer Meeting (FEDSM2021)

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