Heat Transfer and Flow Structure in a Latticework Duct With Different Sidewalls

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Wei Du ◽  
Lei Luo ◽  
Songtao Wang ◽  
Jian Liu ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Flow Structure ◽  
Suction Side ◽  
Reynolds Numbers ◽  
Pressure Side ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Abstract Heat transfer characteristics in a latticework duct with various sidewalls are numerically investigated. The crossing angle is 90 deg and the number of subchannels is eleven on both the pressure side and suction side for each latticework duct. The thickness of the ribs is 8 mm and the distance between adjacent ribs is 24 mm. The investigation is conducted for various Reynolds numbers (11,000 to 55,000) and six different sidewalls. Flow structure, pressure drop, and heat transfer characteristics are analyzed. Results revealed that the sidewall has significant effects on heat transfer and flow structure. The triangle-shaped sidewall provides the highest Nusselt number accompanied by the highest friction factor. The sidewall with a slot shows the lowest friction factor and Nusselt number. An increased slot width decreased the Nusselt number and friction factor simultaneously.

Experimental Investigation on Heat Transfer and Friction Factor in Open Matrix Sub-Channels

2021 ◽  
Author(s):  
Anjana Narottambhai Prajapati ◽  
Andallib Tariq
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Nusselt Number ◽  
Friction Factor ◽  
Elevated Temperatures ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Aspect Ratios ◽  
Factor Ratio ◽  
The Matrix

Abstract Matrix cooling has opened new possibilities for enhancing the convective heat transfer coefficients without compromising upon the structural rigidity and the life of the gas turbine blade at elevated temperatures. However, the dense structure of the matrix significantly increases the flow resistance, and imposes the limitation to its usage. Recently, a matrix with a gap on the sidewalls called open matrix has been proposed by few researchers to reduce the associated pressure penalties. This detailed experimental investigation aims to study the open matrix channel flow, and presents the effects of varying sidewall gaps on heat transfer characteristics and friction factor in the open matrixes having rib angle 45o for three different sub-channel aspect ratios 1.2, 0.8, and 0.4. Liquid crystal thermography has been utilized to discern the detailed heat transfer characteristics. Results have been evaluated in terms of augmentation Nusselt number, friction factor ratio, and overall thermal performance factor over the Reynolds numbers 5800 -14000. The closed matrixes provided the highest augmentation in Nusselt number, and the gaps on the sidewall have shown an overall reduction in augmentation Nusselt number in most cases. However, the suitable sidewall gap showed the effective reduction in pressure penalties for the smaller sub-channel aspect ratios. The highest augmentation Nusselt number amongst the open matrixes has been found as 3.83 with a reduced friction factor ratio for the matrix with a 4 mm gap in sub-channel aspect ratio = 0.8 (i.e. 4 sub-channels) at Re = 8100.

Theoretical prediction of performance of Single and Double pass solar air heaters with artificial roughened absorber plates

2018 ◽  
Vol 8 (4) ◽  
Author(s):  
S. G. Sam Stanley ◽  
K.Kalidasa Murugavel Kumar Reddy ◽  
M. Blessy Queen Mary
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Theoretical Prediction ◽  
Friction Factor ◽  
The Other ◽  
Solar Air Heater ◽  
Roughness Parameters ◽  
Heat Transfer Characteristics ◽  
Double Pass ◽  
Transfer Characteristics

Investigations are carried out on artificial roughened absorber plates on Solar air heater. The roughness parameters are identified in to five basic profiles A, B, C, D and E. The profiles A, B and C are basic cubical and cylindrical profiles and the profiles D and E are categorized as rod arrangement of inline and staggered nature. Both frictional and heat transfer characteristics have been studied. Optimum results of frictional and heat transfer characteristics have been arrived out. Results show a higher value of frictional factor for the profile E. All reasons of variations have been justified and discussed. The deviation of friction factor from modified Balsius equation is within the limit of 4.32 %. Results also show higher value of Nusselt number for the inline rod arrangement of SAH than the other profiles.

Numerical Investigation of Flow and Heat Transfer in Microchannels

2008 ◽  
Author(s):  
Emrah Deniz ◽  
I. Yalcin Uralcan
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Experimental Studies ◽  
Numerical Results ◽  
Turbulent Regime ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Micro Channels

Mini and microchannel applications have become an important and attractive research area during the past decades. For micro systems design purposes, numerical and experimental studies have been conducted on flow and heat transfer characteristics of mini and microchannels and various friction factor and Nusselt number correlations have been proposed. Some researchers have tried to apply conventional tube correlations to mini and micro channels, rather than deriving new correlations. In this study, using commercial CFD software, flow and heat transfer characteristics in laminar and turbulent flow through circular channels are analyzed numerically. The applicability of conventional correlations in calculating the friction factor and Nusselt number is investigated. It is concluded that, in laminar regime conventional correlations can be used to calculate the friction factor for the channel sizes considered. In turbulent regime, however, numerical results for friction factor yielded greater values than those calculated by the conventional correlations. Numerical Nusselt numbers are found to be closer to the conventional values in laminar and turbulent regimes. In turbulent regime, on the other hand, Nusselt number values calculated with the microchannel correlations are determined to be greater than the numerical results and the values calculated with the conventional correlations.

scholarly journals Numerical Investigations on Heat Transfer Characteristics of Single Particle and Hybrid Nanofluids in Uniformly Heated Tube

Symmetry ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 876
Author(s):  
Kunal Sandip Garud ◽  
Moo-Yeon Lee
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Performance Evaluation ◽  
Friction Factor ◽  
Volume Fraction ◽  
Evaluation Criteria ◽  
Hybrid Nanofluid ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

In the present study, the heat transfer characteristics, namely, heat transfer coefficient, Nusselt number, pressure drop, friction factor and performance evaluation criteria are evaluated for water, Al2O3 and Al2O3/Cu nanofluids. The effects of Reynolds number, volume fraction and composition of nanoparticles in hybrid nanofluid are analyzed for all heat transfer characteristics. The single particle and hybrid nanofluids are flowing through a plain straight tube which is symmetrically heated under uniform heat flux condition. The numerical model is validated for Nusselt number within 7.66% error and friction factor within 8.83% error with corresponding experimental results from the previous literature study. The thermophysical properties of hybrid nanofluid are superior to the single particle nanofluid and water. The heat transfer coefficient, Nusselt number and pressure drop show increasing trend with increase in the Reynolds number and volume fraction. The friction factor shows the parabolic trend, and the performance evaluation criteria shows small variations with change in Reynolds number. However, both friction factor and performance evaluation criteria have increased with increase in the volume fraction. The 2.0% Al2O3/Cu with equal composition of both nanoparticles (50/50%) have presented superior heat transfer characteristics among all working fluids. Further, the heat transfer characteristics of 2.0% Al2O3/Cu hybrid nanofluid are enhanced by changing the nanoparticle compositions. The performance evaluation criteria for 2.0% Al2O3, 2.0% Al2O3/Cu (50/50%), 2.0% Al2O3/Cu (75/25%) and 2.0% Al2O3/Cu (25/75%) are evaluated as 1.08, 1.11, 1.10 and 1.12, respectively.

scholarly journals Numerical Simulation Study on Flow Laws and Heat Transfer of Gas Hydrate in the Spiral Flow Pipeline with Long Twisted Band

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 489
Author(s):  
Yongchao Rao ◽  
Lijun Li ◽  
Shuli Wang ◽  
Shuhua Zhao ◽  
Shidong Zhou
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Gas Hydrate ◽  
Pipe Wall ◽  
Heat Transfer Characteristics ◽  
Natural Gas Hydrate ◽  
Spiral Flow ◽  
Transfer Characteristics ◽  
Straight Flow

The natural gas hydrate plugging problems in the mixed pipeline are becoming more and more serious. The hydrate plugging has gradually become an important problem to ensure the safety of pipeline operation. The deposition and heat transfer characteristics of natural gas hydrate particles in the spiral flow pipeline have been studied. The DPM model (discrete phase model) was used to simulate the motion of solid particles, which was used to simulate the complex spiral flow characteristics of hydrate in the pipeline with a long twisted band. The deposition and heat transfer characteristics of gas hydrate particles in the spiral flow pipeline were studied. The velocity distribution, pressure drop distribution, heat transfer characteristics, and particle settling characteristics in the pipeline were investigated. The numerical results showed that compared with the straight flow without a long twisted band, two obvious eddies are formed in the flow field with a long twisted band, and the velocities are maximum at the center of the vortices. Along the direction of the pipeline, the two vortices move toward the pipe wall from near the twisted band, which can effectively carry the hydrate particles deposited on the wall. With the same Reynolds number, the twisted rate was greater, the spiral strength was weaker, the tangential velocity was smaller, and the pressure drop was smaller. Therefore, the pressure loss can be reduced as much as possible with effect of the spiral flow. In a straight light flow, the Nusselt number is in a parabolic shape with the opening downwards. At the center of the pipe, the Nusselt number gradually decreased toward the pipe wall at the maximum, and at the near wall, the attenuation gradient of the Nu number was large. For spiral flow, the curve presented by the Nusselt number was a trough at the center of the pipe and a peak at 1/2 of the pipe diameter. With the reduction of twist rate, the Nusselt number becomes larger. Therefore, the spiral flow can make the temperature distribution more even and prevent the large temperature difference, resulting in the mass formation of hydrate particles in the pipeline wall. Spiral flow has a good carrying effect. Under the same condition, the spiral flow carried hydrate particles at a distance about 3–4 times farther than that of the straight flow.

Experimental Study and Genetic-Algorithm-Based Correlation on Pressure Drop and Heat Transfer Performances of a Cross-Corrugated Primary Surface Heat Exchanger

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Qiu-Wang Wang ◽  
Dong-Jie Zhang ◽  
Gong-Nan Xie
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Surface Heat ◽  
Heat Transfer Correlations ◽  
Surface Heat Exchanger

Heat transfer and pressure drop characteristics of a cross-corrugated (CC) primary surface heat exchanger with different CC passages (P/H=2, θ=60 and 120 deg, called CC2-60 and CC2-120, respectively) in two air sides have been experimentally investigated in this study. It is shown that the corrugation angle (θ) and the ratio of the wavelength P to height H(P/H) are the two key parameters of CC passages to influence the heat transfer and flow friction performances. The heat transfer and friction factor correlations for these two configurations are also obtained with Reynolds numbers ranging from Re=450–5500(CC2-60) and Re=570–6700(CC2-120). At a certain P/H, the Nusselt number, Nu, and the friction factor, f, are affected by the corrugation angle, θ. The heat transfer performance of CC2-120 are much better than that of CC2-60 while the pressure drop of the former is higher than that of the latter, especially at high Reynolds numbers region. The critical Reynolds numbers at which the flow mode transits from laminar to turbulent in the two different passages are also estimated. Furthermore, in this study a genetic algorithm (GA) has been used to determine the coefficients of heat transfer correlations by separation of total heat transfer coefficient without any information of measured wall temperatures. It is concluded that the GA-based separated heat transfer Nusselt number provides a good agreement with the experimental data; the averaged relative deviation by GA (1.95%) is lower than that by regression analysis (2.84%). The inversely yielding wall temperatures agree well with the measured data in turn supporting the reliability of experimental system and measurements. It is recommended that GA techniques can be used to handle more complicated problems and to obtain both-side heat transfer correlations simultaneously, where the conventional Wilson-plot method cannot be applied.

scholarly journals Effects of Reynolds number, baffle angle, and baffle distance on three-dimensional turbulent flow and heat transfer in a circular pipe

2015 ◽  
Vol 19 (5) ◽  
pp. 1633-1648 ◽  
Author(s):  
Oguz Turgut ◽  
Erkan Kizilirmak
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Thermal Performance ◽  
Three Dimensional ◽  
Circular Pipe ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

In this study, steady-state three-dimensional turbulent forced convection flow and heat transfer characteristics in a circular pipe with baffles attached inside pipe have been numerically investigated under constant wall heat flux boundary condition. Numerical study has been carried out for Reynolds number Re of 3000-50,000, Prandtl number Pr of 0.71, baffle distances s/D of 1, 2, and 3, and baffle angle a of 30o-150o. Ansys Fluent 12.0.1 software has been used to solve the flow field. It is observed that circular pipe having baffles has a higher Nusselt number and friction factor compared to the smooth circular pipe without baffles. Maximum Nusselt number and friction factor are obtained for the baffle angle of 90o. Nusselt number increases while baffle distance increases in the range of studied; however, friction factor decreases. Periodically fully developed conditions are obtained after a certain module. Thermal performance factor increases with increasing baffle distance in the rage of studied but decreases with increasing Reynolds number; maximum thermal performance factor is obtained for the baffle angle of 150?. Results show that baffle distance, baffle angle, and Reynolds number play important role on both flow and heat transfer characteristics. The accuracy of the results obtained in this study is verified by comparing the results with those available in the literature for smooth circular pipes. All the numerical results are correlated within accuracy of ?10 and ?15% for average Nusselt number and Darcy friction factor, respectively.

Flow Structure and Heat Transfer Characteristics of a Rectangular Channel With Pin Fins and Dimples With Different Shapes

2018 ◽  
Vol 11 (2) ◽  
Author(s):  
Lei Luo ◽  
Han Yan ◽  
Wei Du ◽  
Songtao Wang ◽  
Changhai Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Flow Structure ◽  
Rectangular Channel ◽  
Horseshoe Vortex ◽  
Heat Transfer Characteristics ◽  
Pin Fin ◽  
Heat Transfer Augmentation ◽  
Transfer Characteristics ◽  
Pin Fins

Abstract In this study, numerical simulations are conducted to investigate the effects of pin fin and dimple shape on the flow structure and heat transfer characteristics in a rectangular channel. The studied shapes for dimple and pin fin are circular, spanwise-elliptical, and streamwise-elliptical, respectively. The flow structure, friction factor, and heat transfer performance are obtained and analyzed with Reynolds number ranging from 10,000 to 50,000. Channel with circular pin fin and dimple is chosen as the Baseline. Channels with spanwise-elliptical pin fins have the best heat transfer augmentation, while also accompanied with the largest friction factor. Spanwise-elliptical pin fin generates the strongest horseshoe vortex which is responsible for the best heat transfer augmentation. Besides, channels with streamwise-elliptical pin fins show the worst heat transfer augmentation and the smallest friction factors. Dimple plays an important role in improving the heat transfer. Spanwise-elliptical dimple yields the best heat transfer augmentation which is attributed to the strongest counter-rotating vortex, while streamwise-elliptical dimple shows the worst heat transfer enhancement.

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