Investigation of thermal enhancement factor in micro pulsating heat exchanger using LIF visualization technique

2020 ◽  
Vol 159 ◽  
pp. 120121
Author(s):  
Young Bae Kim ◽  
Ho Kim ◽  
Jaeyong Sung
Keyword(s):  
Heat Exchanger ◽  
Enhancement Factor ◽  
Visualization Technique ◽  
Thermal Enhancement ◽  
Thermal Enhancement Factor

scholarly journals Thermohydraulic Performance Improvement in Heat Exchanger Square Duct Inserted with 45° Inclined Square Ring

2020 ◽  
Vol 2020 ◽  
pp. 1-22
Author(s):  
Amnart Boonloi ◽  
Withada Jedsadaratanachai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Enhancement Factor ◽  
Flow Behavior ◽  
Square Duct ◽  
Thermal Enhancement ◽  
Performance Development ◽  
Thermal Enhancement Factor

Thermal performance development, heat transfer structure, and flow behavior in the heat exchanger square duct equipped with a 45° inclined square ring are investigated numerically. The effects of flow blockage ratios and spacing ratios for the inclined square ring on fluid flow and heat transfer are considered. The Reynolds number (Re = 100–2000, laminar regime) based on the hydraulic diameter of the square duct is selected for the present work. The numerical domain of the square duct inserted with the 45° inclined square ring is solved with the finite volume method. The SIMPLE algorithm is picked for the numerical investigation. The heat transfer characteristics and flow topologies in the square duct inserted with the inclined square ring are plotted in the numerical report. The heat transfer rate, pressure loss, and efficiency for the square duct placed with the inclined square ring are presented in forms of Nusselt number, friction factor, and thermal enhancement factor, respectively. As the numerical results, it is detected that the heat transfer rate of the heat exchanger square duct inserted with the inclined square ring is around 1.00–10.05 times over the smooth duct with no inclined square ring. Additionally, the maximum thermal enhancement factor for the heat exchanger square duct inserted with the inclined square ring is around 2.84.

scholarly journals Experimental investigation of the effect of wave turbulators on heat transfer in pipes

2021 ◽  
pp. 183-183
Author(s):  
Sendogan Karagoz ◽  
Semih Erzincanli ◽  
Orhan Yildirim ◽  
Ilker Firat ◽  
Mehmet Kaya ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Enhancement Factor ◽  
Single Phase ◽  
Reynolds Numbers ◽  
Nusselt Numbers ◽  
Thermal Enhancement ◽  
Enhancement Factors ◽  
Thermal Enhancement Factor

This experimental study deals with the heat transfer and friction effects of sinusoidal part turbulators for single-phase flows occurring in a circular shaped pipe. Turbulators with three different radius values are placed in the pipe to make the flow turbulent. In this way, changes in Nusselt number and friction coefficient are examined. As a result of the experiments made with Reynolds numbers in the range of 6614-20710, the increase rates of the Nusselt numbers of turbulators with 20 mm, 110 mm and 220 mm radius compared to the empty pipe were obtained as 153.49%, 85.36%, and 52.09%, respectively. As a result of the decrease in the radius, there was an increase in the Nusselt number and the friction factor. Parallel to the Nusselt number, the highest friction factor was obtained in the smallest radius turbulator. It was found that the thermal enhancement factors of 110 mm and 220 mm radius turbulators increased by 179.54% and 132.95%, respectively, compared to the 20 mm radius turbulator. Similarly, it was determined that the thermal enhancement factor of the 110 mm radius turbulator increased by 20% compared to the 220 mm radius turbulator.

CFD analysis for thermal performance augmentation of solar air heater using deflector ribs

2020 ◽  
Vol 14 (3) ◽  
pp. 7282-7295
Author(s):  
R. Venkatesh ◽  
Nitesh Kumar ◽  
N. Madhwesh ◽  
Manjunath M.S.
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Enhancement Factor ◽  
Air Gap ◽  
Solar Air Heater ◽  
Number Range ◽  
Reynolds Number Range ◽  
Thermal Enhancement ◽  
Gap Height ◽  
Thermal Enhancement Factor

This paper presents the effect of deflector ribs on the thermal performance of flat plate solar air heater using Computational Fluid Dynamics (CFD) methodology. The analysis is carried out using two-dimensional computational domain for the Reynolds number range of 6000-18000. RNG k-є turbulence model is used to capture the turbulence characteristics of the flow. The deflector rib has a cross-section of isosceles triangle and is placed transversely with respect to the flow. The distance between consecutive ribs is varied as 40mm, 80mm, 160mm and 320mm while the air gap height is varied as 2mm, 3mm, 5mm and 10mm. The numerical model is validated against the well-known correlation of Dittus-Boelter for smooth duct. The simulation results reveal that the presence of deflector ribs provide augmented heat transfer through flow acceleration and enhanced turbulence levels. With reference to smooth duct, the maximum achieved heat transfer improvement is about 1.39 times for the inter-rib distance of 40mm and an air gap height of 3mm while the maximum fiction factor achieved was about 3.82 times for pitch value of 40mm and air gap height of 3mm. The highest thermal enhancement factor is achieved for the pitch value of 320mm and an air gap height of 3mm at Re=6000. The air gap height value of 10mm exhibits thermal enhancement factor values lesser than 1.0 and hence is not recommended for use as heat transfer enhancement device for the entire Reynolds number range used in the analysis. The pitch value of 320 mm exhibits thermal enhancement factor greater than 1.0 for almost all the Reynolds number range used in the analysis and varies between 0.93 and 1.07.

Thermal performance enhancement of flat plate solar air heater using transverse U-shaped turbulator - A numerical study

2019 ◽  
Vol 13 (3) ◽  
pp. 5562-5587 ◽  
Author(s):  
M. S. Manjunath ◽  
R. Venkatesh ◽  
N. Madhwesh
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Enhancement Factor ◽  
Performance Enhancement ◽  
Numerical Study ◽  
Solar Air Heater ◽  
Air Heater ◽  
Relative Pitch ◽  
Thermal Enhancement ◽  
Thermal Enhancement Factor

The aim of this study is to determine the effect of U-shaped rib turbulator on the flow and heat transfer characteristics of flat plate solar air heater using two dimensional CFD analysis. The analysis is carried out using the CFD software tool ANSYS Fluent for the flow Reynolds number ranging from 9000 to 21,000.The relative pitch(P/e) of the U-shaped rib is varied as 5, 10, 25 and 40 for a fixed relative rib height of 0.0421. It is shown that the U-shaped rib augments the Nusselt number by about 1.76 times while the friction factor increased by about 1.95 times with reference to smooth duct for a relative pitch of 10 and 5 respectively. The maximum thermal enhancement factor is obtained as 1.5 for the configuration of P/e=25. A comparative analysis of U-shaped rib with circular rib reveals that the U-shaped rib turbulator is found to be more effective in providing heat transfer enhancement and has about 15% higher thermal enhancement factor as compared to circular turbulator.

scholarly journals Heat Transfer and Fluid Flow Characteristics of Microchannel with Oval-Shaped Micro Pin Fins

Entropy ◽  
2021 ◽  
Vol 23 (11) ◽  
pp. 1482
Author(s):  
Yuting Jia ◽  
Jianwei Huang ◽  
Jingtao Wang ◽  
Hongwei Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Enhancement Factor ◽  
Height Ratio ◽  
Flow And Heat Transfer ◽  
Thermal Enhancement ◽  
Pin Fins ◽  
Micro Pin Fins ◽  
Thermal Enhancement Factor

A novel microchannel heat sink with oval-shaped micro pin fins (MOPF) is proposed and the characteristics of fluid flow and heat transfer are studied numerically for Reynolds number (Re) ranging from 157 to 668. In order to study the influence of geometry on flow and heat transfer characteristics, three non-dimensional variables are defined, such as the fin axial length ratio (α), width ratio (β), and height ratio (γ). The thermal enhancement factor (η) is adopted as an evaluation criterion to evaluate the best comprehensive thermal-hydraulic performance of MOPF. Results indicate that the oval-shaped pin fins in the microchannel can effectively prevent the rise of heat surface temperature along the flow direction, which improves the temperature distribution uniformity. In addition, results show that for the studied Reynolds number range and microchannel geometries in this paper, the thermal enhancement factor η increases firstly and then decreases with the increase of α and β. In addition, except for Re = 157, η decreases first and then increases with the increase of the fin height ratio γ. The thermal enhancement factor for MOPF with α = 4, β = 0.3, and γ = 0.5 achieves 1.56 at Re = 668. The results can provide a theoretical basis for the design of a microchannel heat exchanger.

scholarly journals A CFD Analysis on the Influence of Upstream Surface Geometry Modifications of Clerestory Shaped Rib on Heat Transfer Characteristics of Solar Air Heater

2021 ◽  
Vol 18 (3) ◽  
pp. 8907-8926
Author(s):  
Dr. Dolfred Vijay Fernandes ◽  
Manjunath M.S.
Keyword(s):  
Heat Transfer ◽  
Enhancement Factor ◽  
Recirculation Zone ◽  
Lower Surface ◽  
Vertical Surface ◽  
Solar Air Heater ◽  
Dimensional Approach ◽  
Surface Geometry ◽  
Thermal Enhancement ◽  
Thermal Enhancement Factor

Two-dimensional numerical analysis is conducted to determine the influence of upstream surface modifications of a novel clerestory shaped rib turbulator on thermal performance augmentation. The upstream surface of the rib is divided into two parts where the upper rib surface is always normal to the incoming flow and the lower rib surface, which is inclined to the flow. The elevation of the vertical surface is varied using non-dimensional approach length (h/e=0, 0.25, 0.5 and 0.75), and the inclination of the lower surface is varied using the rib angle (θ=15°, 45° and 90°). The relative roughness height and pitch of rib is fixed as 0.0421 and 12.5, respectively. RNG k-ϵ turbulence model is used in the analysis, and Reynolds number is varied from 8000-20000. The results reveal that the combined effect of flow impingement and the suppression of formation of recirculation zone leads to increased heat transfer. Lower values of non-dimensional approach length and rib angle provides a higher thermal enhancement factor. The highest increase in Nusselt number is found to be about 1.82 times that of the smooth duct at Re=8000 for h/e=0.25 and rib angle of 15°. The maximum thermal enhancement factor is found to have a range of 1.6-1.45 for an approach length of 0.25 and a rib angle of 15°.

Numerical investigation of electrohydrodynamic effects on the airflow through corrugated channels

2013 ◽  
Vol 227 (12) ◽  
pp. 2730-2741 ◽  
Author(s):  
HM Deylami ◽  
N Amanifard ◽  
F Dolati ◽  
R Kouhikamali ◽  
K Mostajiri
Keyword(s):  
Enhancement Factor ◽  
Average Nusselt Number ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Numerical Approach ◽  
Two Dimensional ◽  
Air Stream ◽  
Thermal Enhancement ◽  
Thermal Enhancement Factor ◽  
Electrohydrodynamic Actuator

To enhance the forced convection heat transfer of turbulent air stream inside the different corrugated channels, a numerical study has been conducted to explore the effect of electrohydrodynamic actuator. In this regard, a two-dimensional numerical approach has been developed to evaluate the average Nusselt number and friction factor. The results obtained show that, while the thermal enhancement factor without electrohydrodynamic is best with trapezoidal corrugation for flows in the low Reynolds number regime, the addition of electrohydrodynamic works best with rectangular corrugation.

Influence of stepped cylindrical turbulence generators on the thermal enhancement factor of a flat plate solar air heater

Solar Energy ◽  
2020 ◽  
Vol 198 ◽  
pp. 295-310 ◽  
Author(s):  
A. Leander Antony ◽  
Shreyas P. Shetty ◽  
N. Madhwesh ◽  
N. Yagnesh Sharma ◽  
K. Vasudeva Karanth
Keyword(s):  
Flat Plate ◽  
Enhancement Factor ◽  
Solar Air Heater ◽  
Air Heater ◽  
Thermal Enhancement ◽  
Thermal Enhancement Factor

Numerical Investigation of Flow Friction and Heat Transfer in a Channel with Various Shaped Ribs Mounted on Two Opposite Ribbed Walls

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Khwanchit Wongcharee ◽  
Wayo Changcharoen ◽  
Smith Eiamsa-ard
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Turbulence Model ◽  
Enhancement Factor ◽  
Temperature Fields ◽  
Flow Friction ◽  
High Heat Transfer ◽  
Thermal Enhancement ◽  
The One ◽  
Thermal Enhancement Factor

Heat transfer and fluid flow characteristics through a channel with two - dimensional transverse ribs are numerically investigated. The effects of different shaped ribs (rectangular rib, triangular rib, cylindrical rib, concave-concave rib, convex-concave rib, long convex-short concave rib and long concave-short concave rib) are examined. The investigation is performed for the ribs mounted on top and bottom walls with rib pitch to height ratio (P/e) of 6.67, in Reynolds number between 3000 and 7000, under constant wall temperature condition. For the present case, the data predicted by SST k-omega turbulence model show better agreement with the experimental data, than those predicted by RNG k-epsilon turbulence model. The mean heat transfer, flow friction, temperature fields and the local heat transfer coefficients as well as the flow structure behaviors are reported. For the ribs considered, the channel with triangular-ribs yields the highest Nusselt number, the one with concave-concave rib provides the highest friction and the one with cylindrical rib show the best thermal enhancement. At the similar condition, the triangular rib gives higher Nusselt number than that provided by the cylindrical one by around 29.3 percent, while the cylindrical rib offers the highest thermal enhancement factor of 1.4 which is higher than that of the cylindrical one by around 1.33 percent while the cylindrical rib offers the highest thermal enhancement factor of 1.33 which is higher than that of the triangular one by around 9.6 percent. In addition, in spite of their high heat transfer, the concave-concave rib and long concave-concave rib yield low thermal performance factors, due to the prominent effect of high friction factor.

scholarly journals Multidisciplinary Optimization in Helical Grooved Tubes for Heat Transfer Enhancement

2021 ◽  
pp. 172-186
Author(s):  
Shamoon Jamshed
Keyword(s):  
Reynolds Number ◽  
Enhancement Factor ◽  
Numerical Study ◽  
Multidisciplinary Optimization ◽  
Numerical Studies ◽  
Design Variables ◽  
Plate Design ◽  
Thermal Enhancement ◽  
Thermal Enhancement Factor

Optimization in engineering is a significant tool for selecting the best fit when several design variables are present. It helps in determining the optimum through a combination of a set of design variables with objective functions subject to certain constraints. In the design of heat exchangers too, where tremendous research is going on to optimize its effectiveness, certain efforts are being done to improve the quality of the inner tube, shell, or plate design. In this respect, surface enhancement has been actively researched in recent decades. This sort of augmentation is usually dominant on the tube side. It has been seen that the study is greatly conducted in the past experimentally, but numerical studies are limited to determine friction factor or Nusselt number. Only a few discussed an important factor called entropy generation minimization. In this paper, with the optimization in view, the design is based on multiple disciplines. That is, first a numerical study is performed on the helically grooved tubes to examine the thermal enhancement factor. Numerical results are initially validated with published experimental results. The optimized tube is then selected based on the D-optimal design for the thermal enhancement factor and finally, the entropy minimization study concerning the Reynolds number is conducted on the optimized tube. It is observed that the tube with the greatest number of grooves, the maximum depth, and the least pitch performs the best. However, the optimum Reynolds number is at the point where the tube has the least entropy generated as compared to the smooth tube.

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