Implication of geometrical configuration on heat transfer enhancement in converging minichannel using nanofluid by two phase mixture model: A numerical analysis

2020 ◽  
pp. 095440892096469
Author(s):  
Md. Faizan ◽  
Sukumar Pati ◽  
Pitamber R Randive
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Straight Channel ◽  
Particle Loading ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Phase Mixture ◽  
Converging Angle

In the present study laminar forced convective flow of nanofluid through a converging minichannel is investigated numerically by employing two phase mixture model. The heat transfer enhancement and the corresponding pressure drop are analyzed for the following range of parameters: Reynolds number (700 ≤ Re ≤ 1650), particle volume concentration (0% ≤ ϕ ≤ 4%) and converging angle (θ = 0.029°, 0.043° and 0.05°). The results indicate that there is a considerable increase in pressure drop coupled with enhancement in heat transfer rate with particle loading due to the improvement in the thermal properties of the resulting mixture. The pressure drop in the converging channel increases with the converging angle. The pressure drop augments as high as 2 times by advancing the particle loading from 0% to 4%. The wall temperature decreases appreciably by 34 K and heat transfer coefficient is enhanced by as high as 98% from Re =  700, ϕ = 0% and straight channel to Re =1650, Hout = 2.75mm and ϕ = 4%. The enhancement in heat transfer and corresponding increase in pressure drop as compared to equivalent straight channel is presented by the performance factor, which increases with decrease in converging angle. There is a significant concern of the pumping power with increase in converging angle, volume fraction and Reynolds number.

Heat Transfer Enhancement in a Rectangular (AR = 3:1) Channel With V-Shaped Dimples

2012 ◽  
Vol 135 (1) ◽  
Author(s):  
C. Neil Jordan ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Liquid Crystal ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Secondary Flows ◽  
Transfer Enhancement ◽  
Reduced Pressure

An alternative to ribs for internal heat transfer enhancement of gas turbine airfoils is dimpled depressions. Relative to ribs, dimples incur a reduced pressure drop, which can increase the overall thermal performance of the channel. This experimental investigation measures detailed Nusselt number ratio distributions obtained from an array of V-shaped dimples (δ/D = 0.30). Although the V-shaped dimple array is derived from a traditional hemispherical dimple array, the V-shaped dimples are arranged in an in-line pattern. The resulting spacing of the V-shaped dimples is 3.2D in both the streamwise and spanwise directions. A single wide wall of a rectangular channel (AR = 3:1) is lined with V-shaped dimples. The channel Reynolds number ranges from 10,000–40,000. Detailed Nusselt number ratios are obtained using both a transient liquid crystal technique and a newly developed transient temperature sensitive paint (TSP) technique. Therefore, the TSP technique is not only validated against a baseline geometry (smooth channel), but it is also validated against a more established technique. Measurements indicate that the proposed V-shaped dimple design is a promising alternative to traditional ribs or hemispherical dimples. At lower Reynolds numbers, the V-shaped dimples display heat transfer and friction behavior similar to traditional dimples. However, as the Reynolds number increases to 30,000 and 40,000, secondary flows developed in the V-shaped concavities further enhance the heat transfer from the dimpled surface (similar to angled and V-shaped rib induced secondary flows). This additional enhancement is obtained with only a marginal increase in the pressure drop. Therefore, as the Reynolds number within the channel increases, the thermal performance also increases. While this trend has been confirmed with both the transient TSP and liquid crystal techniques, TSP is shown to have limited capabilities when acquiring highly resolved detailed heat transfer coefficient distributions.

Numerical investigation of fluid flow structure and heat transfer in a passage with continuous and truncated V-shaped ribs

2015 ◽  
Vol 25 (1) ◽  
pp. 171-189 ◽  
Author(s):  
Shian Li ◽  
Gongnan Xie ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose – The employment of continuous ribs in a passage involves a noticeable pressure drop penalty, while other studies have shown that truncated ribs may provide a potential to reduce the pressure drop while keeping a significant heat transfer enhancement. The purpose of this paper is to perform computer-aided simulations of turbulent flow and heat transfer of a rectangular cooling passage with continuous or truncated 45-deg V-shaped ribs on opposite walls. Design/methodology/approach – Computational fluid dynamics technique is used to study the fluid flow and heat transfer characteristics in a three-dimensional rectangular passage with continuous and truncated V-shaped ribs. Findings – The inlet Reynolds number, based on the hydraulic diameter, is ranged from 12,000 to 60,000 and a low-Re k-e model is selected for the turbulent computations. The local flow structure and heat transfer in the internal cooling passages are presented and the thermal performances of the ribbed passages are compared. It is found that the passage with truncated V-shaped ribs on opposite walls provides nearly equivalent heat transfer enhancement with a lower (about 17 percent at high Reynolds number of 60,000) pressure loss compared to a passage with continuous V-shaped ribs or continuous transversal ribs. Research limitations/implications – The fluid is incompressible with constant thermophysical properties and the flow is steady. The passage is stationary. Practical implications – New and additional data will be helpful in the design of ribbed passages to achieve a good thermal performance. Originality/value – The results imply that truncated V-shaped ribs are very effective in improving the thermal performance and thus are suggested to be applied in gas turbine blade internal cooling, especially at high velocity or Reynolds number.

Effects of Particle Shape on Nanofluids Laminar Forced Convection in Helically Coiled Tubes

2017 ◽  
Author(s):  
Fang Liu ◽  
Yang Cai
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Particle Shape ◽  
Spherical Nanoparticles ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Laminar Forced Convection ◽  
Shape And Size

In this study, effects of particle morphology (shape and size) on nanofluids laminar forced convection in helically coiled tubes are investigated numerically using Eulerian-Lagrangian two-phase approach. The laminar forced convective heat transfer and pressure drop of Al2O3-water nanofluids containing nanoparticles with various particle shapes (sphere, platelet, blade, cylinder and brick) and sizes at different volume fractions in the developing and fully developed regions are investigated using the validated two-phase model. It is found that the nanofluids containing platelet particle shape has the highest heat transfer enhancement, which is followed by nanofluids containing cylinder, blade, sphere and brick nanoparticle shapes, respectively. Non-spherical nanoparticles with larger aspect ratio, small particle size and a suitable particle volume concentration are beneficial for heat transfer enhancement of forced convection. Heat transfer efficiency reaches minima at Re of 1250 for laminar forced convection with 1% volume fraction. The correlations of Nusselt number and pressure drop with nanoparticle shape and size were developed to predict convective heat transfer of nanofluids containing spherical nanoparticles and non-spherical nanoparticles.

Electrohydrodynamically Enhanced Convective Boiling: Relationship Between Electrohydrodynamic Pressure and Momentum Flux Rate

1999 ◽  
Vol 122 (2) ◽  
pp. 266-277 ◽  
Author(s):  
J. E. Bryan ◽  
J. Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Momentum Flux ◽  
Saturation Temperature ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Convective Boiling ◽  
The Mean ◽  
R 134A

The relationship between the mean radial electrohydrodynamic (EHD) pressure and the rate of the axial momentum flux and its influence on heat transfer enhancement and pressure drop in EHD-enhanced convective boiling of R-134a in a horizontal smooth tube was investigated in detail. A simple theory, which included the characteristics of two-phase flow, was developed to determine the mean radial EHD pressure. It was shown that the amount of heat transfer enhancement and the pressure drop penalty were dependent upon the size of the mean radial EHD pressure relative to the rate of the axial momentum flux. The influence of the mass flux, change in quality, and saturation temperature on the mean radial EHD pressure relative to the rate of the axial momentum flux was also studied. This study has provided a greater understanding of EHD enhancement of the convective boiling heat transfer. [S0022-1481(00)01802-8]

Mechanism of Annular Two-Phase Flow Heat Transfer Enhancement and Pressure Drop Penalty in the Presence of a Radial Electric Field—Turbulence Analysis

2003 ◽  
Vol 125 (3) ◽  
pp. 478-486 ◽  
Author(s):  
Y. Feng ◽  
J. Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Annular Flow ◽  
Radial Electric Field ◽  
Phase Flow ◽  
Transfer Enhancement ◽  
Two Phase ◽  
Flow Heat

The mechanism of heat transfer enhancement and pressure drop penalty in the presence of a radial electric field for the two-phase (liquid/vapor) annular flow is presented. The turbulence spectral theory shows that the radial electric field fluctuation changes the turbulent energy distribution, especially in the radial direction. Consequently, the Reynolds stresses are directly affected by the applied electric field. The analysis reveals that the influence of the applied electric field on the turbulence distribution in an annular two-phase flow leads to the changes in the heat transfer and the pressure drop. The magnitudes of the heat transfer enhancement and the pressure drop penalty are strongly related to the ratio of the radial pressure difference generated by the EHD force to the axial frictional pressure drop. The existing experimental data agree with the predictions of the analysis presented in this paper. The analysis developed here can be a valuable tool in properly predicting the two-phase annular flow heat transfer enhancement and pressure drop penalty in the presence of a radial electric field for both convective boiling and condensation processes.

Heat Transfer Enhancement by Insertion of Vortex Generators in Electronic Chip Cooling: A Numerical Study

2017 ◽  
Author(s):  
Mohammad Rejaul Haque ◽  
Amy Rachel Betz
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Vortex Generators ◽  
Transfer Enhancement ◽  
Maximum Heat

The present work represents a 2-D numerical investigation of forced convection heat transfer over three electronic blocks (silicon chip) in an inline arrangement with elliptical shaped vortex generators (VG-copper made) placed on top of the channel, for a range of Reynolds numbers. The block is prescribed with a 1,000 W/m2 heat flux due to heating of the electronic components installed in the CPU casing. The results show that, vortex generators could effectively enhance the heat transfer in the channel. Subsequently, the effects of Reynolds number (from 500 to 1050), the number of vortex generators (baseline, 1, 2 and 3), aspect ratio of heated block (0.125, 0.15, 0.22), and aspect ratio of vortex generators (0.3125, 0.4, 0.5) on the heat transfer and fluid flow characteristics are examined. The characteristics of the performance parameters are studied numerically with the aid of computational fluid dynamics (CFD). The 3 VG demonstrates nearly 28.35% enhancement of Nusselt number compared to the 1 VG case at Re = 479. The change in pressure drop is less at low Reynolds number compared to higher Reynolds number respective to other parameters. Increasing the aspect ratio of the block increases the convection coefficient while decreasing aspect ratio of VG increases heat transfer coefficient. This enhancement is less significant for the third block as the cooling effect is predominant close to the channel inlet. Increasing consecutive distance between the blocks, enhances the heat transfer coefficient with the penalty of additional pressure drop. However, parametric studies are conducted for the maximum heat transfer enhancement.

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