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.

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.

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.

Heat Transfer Characteristics Within the Matrix Cooling Channels

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Andallib Tariq ◽  
Anjana N. Prajapati
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Turbine Blades ◽  
Percentage Increase ◽  
Heat Transfer Characteristics ◽  
Cooling Channels ◽  
Liquid Crystal Thermography ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
The Matrix

Abstract Matrix or latticework cooling has become a new area of research due to its advantage of providing a structural rigidity to the fragile structures like gas turbine blades, electronic components or circuitries, and compact heat exchangers. In this article, the heat transfer characteristics in matrix cooling channels with different rib angles have been studied using liquid crystal thermography. A total of three matrix models with rib angles 35 deg, 45 deg, and 55 deg having a common subchannel aspect ratio 0.8 have been studied. The results are evaluated in terms of local and average augmentation Nusselt numbers for different regions of the matrix. The augmentation Nusselt number has been found to increase in each region as the angle increases from 35 deg to 45 deg and the same has been found to decrease slightly upon the further increase in angle from 45 deg to 55 deg. The highest percentage increase in augmentation Nusselt number up to 50% has been observed in entry region, whereas the same remained nearly 26–30% in middle and exit regions in streamwise directions, i.e., the effect of the matrix rib angle is more prominent in the entry region. The higher resistance offered by the greater number of ribs for angle 55 deg is believed to be responsible for the decrease in augmentation Nusselt number for Re ≤ 9000.

Detailed Heat Transfer Characteristics of Matrix Cooling Channels With Rib Angle 35° Using Liquid Crystal Thermography

2019 ◽  
Author(s):  
Anjana N. Prajapati ◽  
Andallib Tariq
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Liquid Crystal ◽  
Aspect Ratio ◽  
Friction Factor ◽  
Hydraulic Performance ◽  
Liquid Crystal Thermography ◽  
Aspect Ratios ◽  
Factor Ratio ◽  
Channel Aspect Ratio

Abstract Matrix cooling is relatively newer cooling technique and preferred over the conventional rib turbulators or pin fin cooling due to its capacity to provide the structural rigidity and higher heat transfer enhancement. The present investigation addresses the detailed study of local and averaged heat transfer augmentation distributions within the sub-channels of matrixes with rib angle 35° and varying sub-channels aspect ratios using liquid crystal thermography. The effects of varying sub-channel aspect ratios 1.2, 0.8 and 0.4 on averaged Nusselt number augmentation, friction factor ratio and thermo-hydraulic performance factor have been also verified within the Reynolds numbers range 5800–14000. The flow trend within the sub-channels is typically found to be eccentric and attributed to the possible vortical flow within the sub-channels and this eccentricity reduces as the sub-channel aspect ratio decreases. Results have shown that the highest Nusselt number augmentation and the lowest friction factor ratio are obtained for the highest sub-channel aspect ratio i.e., the best thermo-hydraulic performance factor (≥ 1) has been found for sub-channel aspect ratio 1.2. The sub-channel aspect ratio is found to have significant effect on both Nusselt number augmentation and friction factor ratio as compared to Reynolds number.

An Experimental Investigation on Heat Transfer Characteristics of Hot Surface by Using CuO–Water Nanofluids in Circular Jet Impingement Cooling

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Mayank Modak ◽  
Sandesh S. Chougule ◽  
Santosh K. Sahu
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Jet Impingement ◽  
Test Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Hot Surface ◽  
Plate Distance

In the present study, an experimental investigation has been carried out to analyze the heat transfer characteristics of CuO–water nanofluids jet on a hot surface. A rectangular stainless steel foil (AISI-304, 0.15 mm thick) used as the test surface is electrically heated to obtain the required initial temperature (500 °C). The distribution of surface heat flux on the target surface is evaluated from the recorded thermal images during transient cooling. The effect of nanoparticle concentration and Reynolds number of the nanofluids on the heat transfer characteristics is studied. Tests are performed for varied range of Reynolds number (5000 ≤ Re ≤ 12,000), two different CuO–water nanofluids concentration (Ф = 0.15%, 0.6%) and two different nozzle to plate distance (l/d = 6, 12). The enhancement in Nusselt number for CuO–water nanofluids was found to be 14% and 90%, for nanofluids concentration of Ф = 0.15% and Ф = 0.60%, respectively, compared to pure water. The test surface characteristics after nanofluids jet impingement are studied using scanning electron microscope (SEM). Based on the investigation, a correlation among various parameters, namely, Reynolds number (Re), Prandtl number (Pr), nozzle to plate distance (l/d), and Nusselt number (Nu), is presented.

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 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.

scholarly journals Uncertainties Analysis on the Prediction of Flow and Heat Transfer of Liquid Sodium with CFD Technology

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Zhanwei Liu ◽  
Xinyu Li ◽  
Tenglong Cong ◽  
Rui Zhang ◽  
Lingyun Zheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Coefficient ◽  
Liquid Sodium ◽  
Heat Transfer Characteristics ◽  
Backward Facing Step ◽  
Heating Wall ◽  
Transfer Characteristics ◽  
Cfd Models ◽  
Flow And Heat Transfer

The prediction of flow and heat transfer characteristics of liquid sodium with CFD technology is of significant importance for the design and safety analysis of sodium-cooled fast reactor. The accuracies and uncertainties of the CFD models should be evaluated to improve the confidence of the numerical results. In this work, the uncertainties from the turbulent model, boundary conditions, and physical properties for the flow and heat transfer of liquid sodium were evaluated against the experimental data. The results of uncertainty quantization show that the maximum uncertainties of the Nusselt number and friction coefficient occurred in the transition zone from the inlet to the fully developed region in the circular tube, while they occurred near the reattachment point in the backward-facing step. Furthermore, in backward-facing step flow, the maximum uncertainty of temperature migrated from the heating wall to the geometric center of the channel, while the maximum uncertainty of velocity occurred near the vortex zone. The results of sensitivity analysis illustrate that the Nusselt number was negatively correlated with the thermal conductivity and turbulent Prandtl number, while the friction coefficient was positively correlated with the density and Von Karman constant. This work can be a reference to evaluate the accuracy of the standard k-ε model in predicting the flow and heat transfer characteristics of liquid sodium.

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