Numerical Investigation of Laminar Flow and Heat Transfer in Micro-Cylinder-Groups

2010 ◽  
Author(s):  
Ning Guan ◽  
Zhigang Liu ◽  
Masahiro Takei ◽  
Chengwu Zhang
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Numerical Study ◽  
Differential Pressure ◽  
Temperature Fields ◽  
Geometrical Parameters ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Pressure Resistance

A numerical study on flow and heat transfer of de-ionized water over in-line and staggered micro-cylinder-groups had been performed with Reynolds number varying in the range from 0 to 150. A 3-D incompressible numerical model was employed to investigate the vortex distributions and the influences of the vortexes on the flow and heat transfer characteristics at low Re numbers in micro-cylinder-groups with different geometrical parameters, including micro-cylinder diameters (100μm, 250μm and 500μm), ratios of pitch to micro-cylinder diameter (1.5 2 and 2.5) and ratios of micro-cylinder height to diameter (0.5, 1, 1.5 and 2), etc. The vortex distributions, the flow and temperature fields, and the relationships among them were investigated by solving the numerical model with the finite volume method. It was found that the vortex number became larger with the increase of pitch ratio, and the change of flow rate distribution affected the heat transfer characteristics apparently. The appearance of vortexes in micro-cylinder-group increased the differential pressure resistance; as a result the total flow resistance in micro-cylinder-groups correspondingly increased. Meanwhile, the local heat transfer coefficients nearby the locations of vortexes greatly increased due to the boundary layer separation, which further enhanced the heat transfer in micro-cylinder-groups. The new correlations which could predict Nusselt number of de-ionized water over micro-cylinders with Re number varying from 0–150 had been proposed considering the differential pressure resistance and the natural convection based on numerical calculations in this paper.

Investigations of water-cooled tubes with protrusions for flow and heat transfer characteristics

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fei Wang ◽  
Xiaobing Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Transfer Effect ◽  
Oil Refining ◽  
Geometrical Parameters ◽  
Heat Transfer Characteristics ◽  
Content Type ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Purpose This study aims to present a numerical study on the flow and heat transfer performance of a water-cooled tube with protrusions in different geometrical parameters. Design/methodology/approach A new type of enhanced heat exchanger tube is designed. Protrusions are formed on the inner surface of the tube by mechanical expansion, compression and other processing methods. A three-dimensional numerical symmetry model is established by ANSYS for studying the influence of protrusion distance, protrusion radius and protrusion arrangement on flow and heat transfer characteristics in turbulent flow. Findings The results show that the protrusions increase the heat transfer area and improve the heat transfer effect but also increase the flow resistance. Performance evaluation criteria (PEC) is applied to evaluate the flow and heat transfer characteristics of convex tubes. When adopting the aligned protrusions arrangement, the radius of 2 mm and distance of twice the protrusion radius is most heat transfer effect. The PEC of protrusion tubes with a staggered arrangement are higher than those in aligned arrangement, and the maximum value is 2.36 when Reynolds number is 12,000. Originality/value At present, most of the protrusion technology applications are based on the cold plate heat dissipation of electronic devices, and the flow path is rectangular. Convex tube heat exchanger is a high-efficiency heat exchanger, which uses convex tubes instead of smooth tubes in tubular heat exchangers to enhance heat transfer and widely used in petroleum, chemical, textile, oil refining and other industries.

Laminar Flow and Heat Transfer Characteristics of Colloid Suspensions in Water: A Numerical Study

2009 ◽  
Author(s):  
Khalid N. Alammar ◽  
Lin-wen Hu
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Flow Rate ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Numerical analysis is performed to examine axisymmetric laminar flow and heat transfer characteristics of colloidal dispersions of nanoparticles in water (nanofluids). Effect of volume fraction on flow and heat transfer characteristics is investigated. Four different materials, Alumina, Copper, Copper Oxide, and Graphite are considered. Heat transfer and property measurements were conducted previously for Alumina nanofluid. The measurements have shown that nanofluids can behave as homogeneous mixtures. It is found that oxide-based nanofluids offer the least heat transfer enhancement compared to elements-based nanofluids. When normalized by friction pressure drop, it is shown that graphite can have the highest effective heat transfer enhancement. For a given volume flow rate, all nanofluids exhibited linear increase in heat transfer enhancement with increasing colloids volume fraction, up to 0.05.

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