Extending acoustic in‐line pipe rheometry and friction factor modeling to
            low‐Reynolds
            ‐number,
            non‐Newtonian
            slurries

The goal of this study is to evaluate the computational fluid dynamic (CFD) predictions of friction factor and Nusselt number from six different low Reynolds number k–ε (LRKE) models namely Chang–Hsieh–Chen (CHC), Launder–Sharma (LS), Abid, Lam–Bremhorst (LB), Yang–Shih (YS), and Abe–Kondoh–Nagano (AKN) for various heat transfer enhancement applications. Standard and realizable k–ε (RKE) models with enhanced wall treatment (EWT) were also studied. CFD predictions of Nusselt number, Stanton number, and friction factor were compared with experimental data from literature. Various parameters such as effect of type of mesh element and grid resolution were also studied. It is recommended that a model, which predicts reasonably accurate values for both friction factor and Nusselt number, should be chosen over disparate models, which may predict either of these quantities more accurately. This is based on the performance evaluation criterion developed by Webb and Kim (2006, Principles of Enhanced Heat Transfer, 2nd ed., Taylor and Francis Group, pp. 1–72) for heat transfer enhancement. It was found that all LRKE models failed to predict friction factor and Nusselt number accurately (within 30%) for transverse rectangular ribs, whereas standard and RKE with EWT predicted friction factor and Nusselt number within 25%. Conversely, for transverse grooves, AKN, AKN/CHC, and LS (with modified constants) models accurately predicted (within 30%) both friction factor and Nusselt number for rectangular, circular, and trapezoidal grooves, respectively. In these cases, standard and RKE predictions were inaccurate and inconsistent. For longitudinal fins, Standard/RKE model, AKN, LS and Abid LRKE models gave the friction factor and Nusselt number predictions within 25%, with the AKN model being the most accurate.

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Effect of Pin Diameter Degressive Gradient on Heat Transfer in a Microreactor with Non-Uniform Pin-Fin Array under Low Reynolds Number Conditions

Energies ◽

10.3390/en12142702 ◽

2019 ◽

Vol 12 (14) ◽

pp. 2702

Author(s):

Miao Qian ◽

Jie Li ◽

Zhong Xiang ◽

Chao Yan ◽

Xudong Hu

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Pressure Drop ◽

Friction Factor ◽

Low Reynolds Number ◽

Hydrodynamic Characteristics ◽

Pin Fin ◽

Low Reynolds ◽

Pin Fin Array

To improve the efficiency of hydrogen-producing microreactors with non-uniform pin-fin array, the influence of the pin diameter degressive gradient of the non-uniform pin-fin array (NPFA) on heat transfer and pressure drop characteristics is analyzed in this study via numerical simulation under low Reynolds number conditions. Because correlations in prior studies cannot be used to predict the Nusselt number and pressure drop in the NPFA, new heat transfer and friction factor correlations are developed in this paper to account for the effect of the pin diameter degressive gradient, providing a method for the optimized design of the pin diameter degressive gradient for a microreactor with NPFA. The results show that the Nusselt number and friction factor under a low Reynolds number are quite sensitive to the pin diameter degressive gradient. Based on the new correlations, the exponents of the pin diameter degressive gradient for the friction factor and Nusselt number were 6.9 and 2.1, respectively, indicating the significant influence of the pin diameter degressive gradient on the thermal and hydrodynamic characteristics in the NPFA structure.

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Analytic solutions of the friction factor and the Nusselt number for the low-Reynolds number flow between two wavy plate fins

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2017.08.025 ◽

2017 ◽

Vol 115 ◽

pp. 307-316 ◽

Cited By ~ 4

Author(s):

Dahm Yu ◽

Wonju Jeon ◽

Sung Jin Kim

Keyword(s):

Reynolds Number ◽

Nusselt Number ◽

Friction Factor ◽

Low Reynolds Number ◽

Analytic Solutions ◽

Low Reynolds Number Flow ◽

Reynolds Number Flow ◽

Number Flow ◽

Low Reynolds

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Airside Performance of Wavy Fin-and-Tube Heat Exchangers: Data With Larger Diameter Tube

2010 14th International Heat Transfer Conference, Volume 4 ◽

10.1115/ihtc14-22409 ◽

2010 ◽

Author(s):

Huau Pao Lo ◽

Chinghua Hung ◽

Chi-Chuan Wang

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Friction Factor ◽

Heat Exchangers ◽

Heat Transfer Performance ◽

Low Reynolds Number ◽

Transfer Performance ◽

Frictional Performance ◽

Low Reynolds

This study examines the airside fin-and-tube heat exchangers having a larger diameter tube Dc = 16.59 mm) with the tube row ranging from 1 to 16. It is found that the effect of tube row on the heat transfer performance is quite significant, and the heat transfer performance deteriorates with the rise of tube row. The performance deteriorates with the rise of tube row. The performance drop is especially pronounced at the low Reynolds number region. Actually more than 85% drop of heat transfer performance is seen for Fp ∼ 1.7 mm as the row number is increased from 1 to 16. Upon the influence of tube row on the frictional performance, an unexpected row dependence of the friction factor is encountered. The effect of fin pitch on the airside performance is comparatively small for N = 1 or N = 2. However, a notable drop of heat transfer performance is seen when the number of tube row is increased, and normally higher heat transfer and frictional performance is associated with that of the larger fin pitch.

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Thermal Performance of Pin Fins at Low Reynolds Numbers in Mini-Micro-Channels

ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference, Volume 2 ◽

10.1115/ht2007-32158 ◽

2007 ◽

Cited By ~ 4

Author(s):

A. Rozati ◽

D. K. Tafti ◽

N. E. Blackwell

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Friction Factor ◽

Thermal Performance ◽

Low Reynolds Number ◽

Reynolds Numbers ◽

High Density ◽

Low Reynolds Numbers ◽

Micro Channels ◽

Low Reynolds

The computational study investigates different pin fin arrangements at low Reynolds numbers, which would typically be prevalent in mini-micro-channels used in enhancing heat as well as mass transfer. The effect of pin density, span-wise pitch, and stream-wise pitch is investigated on friction and heat transfer over a range 5<ReD<400. High density pins with small span-wise pitches were found to provide the highest augmentation in heat transfer capacity (conductance), whereas low density pins with or without a large stream-wise pitch were found to provide the least heat transfer benefits in the low Reynolds number range studied. Friction factor decreases considerably as the pin density decreases. The effect of decreasing span-wise pitch increases the friction factor in the low Reynolds number regime (ReD<200) but decreases it beyond ReD = 200 by delaying wake instabilities and the associated increase in form drag. Increasing the stream-wise pitch decreases the friction factor at low ReD<200, but increases it at ReD>200 due to the formation of larger recirculating wakes. Overall it is concluded that a high density arrangement with a small span-wise pitch provides the best thermal performance.

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