A critical review on different roughness geometries and their effect on heat transfer and friction factor

This study investigates the nanofluid flow towards a shrinking cylinder consisting of Al2O3 nanoparticles. Here, the flow is subjected to prescribed surface heat flux. The similarity variables are employed to gain the similarity equations. These equations are solved via the bvp4c solver. From the findings, a unique solution is found for the shrinking strength λ≥−1. Meanwhile, the dual solutions are observed when λc<λ<−1. Furthermore, the friction factor Rex1/2Cf and the heat transfer rate Rex−1/2Nux increase with the rise of Al2O3 nanoparticles φ and the curvature parameter γ. Quantitatively, the rates of heat transfer Rex−1/2Nux increase up to 3.87% when φ increases from 0 to 0.04, and 6.69% when γ increases from 0.05 to 0.2. Besides, the profiles of the temperature θ(η) and the velocity f’(η) on the first solution incline for larger γ, but their second solutions decline. Moreover, it is noticed that the streamlines are separated into two regions. Finally, it is found that the first solution is stable over time.

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Turbulent Heat and Momentum Transports in an Infinite Rod Array

Journal of Heat Transfer ◽

10.1115/1.3248130 ◽

1987 ◽

Vol 109 (3) ◽

pp. 599-605 ◽

Cited By ~ 8

Author(s):

An-Shik Yang ◽

Ching-Chang Chieng

Keyword(s):

Heat Transfer ◽

Friction Factor ◽

Equation Model ◽

Temperature Fields ◽

Turbulent Heat ◽

Fluid Temperature ◽

Transfer Coefficients ◽

Anisotropic Factor ◽

Flow Through ◽

Rod Array

An anisotropic factor is carefully selected from eleven distributions and adopted to the k–ε two-equation model of turbulence to obtain detailed velocity and temperature fields for steady-state, fully developed turbulent flow through infinite triangular/square rod array. The present study covers the ranges of pitch-to-diameter ratio from 1.123 to 1.5, and Reynolds number from 2.4 × 104 to 106. Velocity and wall shear stress are calculated and compared to experimental data. Normalized fluid temperature, friction factor, and heat transfer coefficient are also computed. The correlations of friction factor and heat transfer coefficients for flow inside circular pipe and flow through finite rod arrays are compared with the results for flow through infinite rod arrays.

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Experimental study of turbulent forced convection heat transfer and friction factor in dimpled plate heat exchanger

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2019.114254 ◽

2019 ◽

Vol 162 ◽

pp. 114254 ◽

Cited By ~ 4

Author(s):

Divya P. Soman ◽

S. Karthika ◽

P. Kalaichelvi ◽

T.K. Radhakrishnan

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Heat Exchanger ◽

Friction Factor ◽

Forced Convection ◽

Convection Heat Transfer ◽

Plate Heat Exchanger ◽

Convection Heat ◽

Plate Heat ◽

Forced Convection Heat Transfer

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Thermal Performance Assessment of Turbulent Flow Through Dimpled Tubes

2010 14th International Heat Transfer Conference, Volume 2 ◽

10.1115/ihtc14-22503 ◽

2010 ◽

Cited By ~ 2

Author(s):

Pornchai Nivesrangsan ◽

Somsak Pethkool ◽

Kwanchai Nanan ◽

Monsak Pimsarn ◽

Smith Eiamsa-ard

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Friction Factor ◽

Heat Transfer Rate ◽

Thermal Performance ◽

Transfer Rate ◽

Staggered Arrangement ◽

Plain Tube ◽

Pitch Ratio ◽

Surface Patterns

This paper presents the heat transfer augmentation and friction factor characteristics by means of dimpled tubes. The experiments were conducted using the dimpled tubes with two different dimpled-surface patterns including aligned arrangement (A-A) and staggered arrangement (S-A), each with two pitch ratios (PR = p/Di = 0.6 and 1.0), for Reynolds number ranging from 9800 to 67,000. The experimental results achieved from the dimpled tubes are compared with those obtained from the plain tube. Evidently, the dimpled tubes with both arrangements offer higher heat transfer rates compared to the plain tube and the dimpled tube with staggered arrangement shows an advantage on the basis of heat transfer enhancement over the dimpled tube with aligned arrangement. The increase in heat transfer rate with reducing pitch ratio is due to the higher turbulent intensity imparted to the flow between the dimple surfaces. The mean heat transfer rate offered by the dimpled tube with staggered arrangement (S-A) at the lowest pitch ratio (PR = 0.6), is higher than those provided by the plain tube and the dimpled tube with aligned arrangement (A-A) at the same PR by around 127% and 8%, respectively. The empirical correlations developed in terms of pitch ratio (PR), Prandtl number (Pr) and Reynolds number, are fitted the experimental data within ±8% and ±2% for Nusselt number (Nu) and friction factor (f), respectively. In addition, the thermal performance factors under an equal pumping power constraint of the dimple tubes for both dimpled-surface arrangements are also determined.

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