Effect of Ribs on Heat Transfer and Pressure Drop in a U-Bend Channel With Double-Layer, Dome-Shaped Turning Vanes

Volume 7A: Heat Transfer ◽

10.1115/gt2020-15980 ◽

2020 ◽

Author(s):

Bin Wu ◽

Xing Yang ◽

Zhao Liu ◽

Zhenping Feng

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Secondary Flow ◽

Double Layer ◽

Mass Flow ◽

Flow Distribution ◽

Hydraulic Diameter ◽

Sharp Turn ◽

Helical Vortex ◽

Bend Channel

Abstract In this paper, the combined effects of ribs and double-layer, dome-shaped turning vanes on heat transfer and pressure drop are investigated in an idealized U-bend channel. Five kinds of ribs including transverse ribs, 45° ribs, 135° ribs, V-shaped ribs, and reverse V-shaped ribs combined with one kind of double-layer, dome-shaped turning vanes are applied. Baseline results are compared with the above composite cooling structures. Numerical simulations are performed by solving 3D, steady Reynolds-averaged Navier-Stokes (RANS) equations with k-ω turbulence model. The channel aspect ratio is 1:2 and its hydraulic diameter is 93.13 mm, respectively. Based on the cooling air inlet velocity and the channel inlet hydraulic diameter, the inlet Reynolds numbers are ranging from 100,000 to 440,000. The detailed three-dimensional fluid flow, pressure and heat transfer distributions are presented. Moreover, the thermal performances of the U-bend channel are also evaluated and compared with different cases. The results revealed that combined with the double-layer, dome-shaped turning vanes, the transverse ribs case has the best thermal performance at the tip wall, and the reverse V-shaped ribs case is the best for the leading wall. The pressure drop of the channel with double-layer, dome-shaped turning vanes without any rib turbulator is the lowest, and that of the channel with inclined ribs is significantly higher than that of the channel with transverse ribs. The superposition of the secondary flow induced by the ribs and the Dean vortex induced by the 180° sharp turn has a marked impact on the flow and heat transfer in the channel. In the double-layer, dome-shaped turning vanes channel, the mass flow distribution of the coolant also affects the heat transfer on the tip wall of the channel, and the ribs can adjust the mass flow distribution. The helical vortex superposed by the mainstream flow and the secondary flow induced by the ribs represents typical flow phenomenon in ribbed channels. The flow and development of the helical vortex are the main factors affecting the heat transfer on the leading/trailing walls.

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EXPERIMENTAL STUDY OF PRESSURE DROP AND HEAT TRANSFER IN A U-BEND CHANNEL WITH VARIOUS GUIDE VANES AND RIBS

Journal of Enhanced Heat Transfer ◽

10.1615/jenhheattransf.2015013382 ◽

2015 ◽

Vol 22 (1) ◽

pp. 29-45 ◽

Cited By ~ 8

Author(s):

Susanna Cimina ◽

Chenglong Wang ◽

Lei Wang ◽

Alfonso Niro ◽

Bengt Sunden

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Pressure Drop ◽

Guide Vanes ◽

Bend Channel

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Heat transfer and exergy analysis of flow boiling evaporation in u-bend channel

Journal of Physics Conference Series ◽

10.1088/1742-6596/2116/1/012003 ◽

2021 ◽

Vol 2116 (1) ◽

pp. 012003

Author(s):

T Jatau ◽

T Bello-Ochende

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Entropy Generation ◽

Exergy Analysis ◽

Flow Boiling ◽

Saturation Temperature ◽

Ansys Fluent ◽

Mass Fluxes ◽

Bend Channel ◽

The Heat Transfer Coefficient

Abstract This study presents, a numerical method used to evaluate the exergy analysis of flow boiling evaporation of R134a in a U-bend channel using entropy generation criterion which is concerned with the degradation of exergy during the process due to irreversibilies (entropy generation) contributed by heat transfer and pressure drop. The simulations were conducted with the heat flux of 15 kW/m2, mass fluxes of 200-600 kg/m2s of R134a at the saturation temperature of 15 °C. Three(3) different geometries sizes of U-bend channel’s diameter 6, 8 and 10 mm with the bend radius of 10.2 mm were utilized. The Volume of Fluid (VOF) multiphase flow formulation was used in Ansys Fluent. The results show that the entropy generation increases with increase in mass fluxes due to irreversibilies contributed by the heat transfer coefficient and pressure drop as mass fluxes increase. Based on the size of the U-bend channel, the entropy generation was found to increase as the diameter of the channel increases. The numerical results were compared with the data in the open literature and there was a good agreement.

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Computational Study and Optimization of Laminar Heat Transfer and Pressure Loss of Double-Layer Microchannels for Chip Liquid Cooling

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4007778 ◽

2013 ◽

Vol 5 (1) ◽

Cited By ~ 40

Author(s):

Gongnan Xie ◽

Yanquan Liu ◽

Bengt Sunden ◽

Weihong Zhang

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Double Layer ◽

Flow Rate ◽

Single Layer ◽

Parallel Flow ◽

Heat Fluxes ◽

Liquid Cooling ◽

Counter Flow ◽

Flow Rates

The problem involved in the increase of the chip output power of high-performance integrated electronic devices is the failure of reliability because of excessive thermal loads. This requires advanced cooling methods to be incorporated to manage the increase of the dissipated heat. The traditional air-cooling can not meet the requirements of cooling heat fluxes as high as 100 W/cm2, or even higher, and the traditional liquid cooling is not sufficient either in cooling very high heat fluxes although the pressure drop is small. Therefore, a new generation of liquid cooling technology becomes necessary. Various microchannels are widely used to cool the electronic chips by a gas or liquid removing the heat, but these microchannels are often designed to be single-layer channels with high pressure drop. In this paper, the laminar heat transfer and pressure loss of a kind of double-layer microchannel have been investigated numerically. The layouts of parallel-flow and counter-flow for inlet/outlet flow directions are designed and then several sets of inlet flow rates are considered. The simulations show that such a double-layer microchannel can not only reduce the pressure drop effectively but also exhibits better thermal characteristics. Due to the negative heat flux effect, the parallel-flow layout is found to be better for heat dissipation when the flow rate is limited to a low value while the counter-flow layout is better when a high flow rate can be provided. In addition, the thermal performance of the single-layer microchannel is between those of parallel-flow layout and counter-flow layout of the double-layer microchannel at low flow rates. At last, the optimizations of geometry parameters of double-layer microchannel are carried out through changing the height of the upper-branch and lower-branch channels to investigate the influence on the thermal performance.

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