International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Analysis of Heat Generation in Double Pipe Heat Exchanger: An Experimental Ev...IRJET Journal
This document summarizes research on analyzing heat generation in a double pipe heat exchanger with an elliptical fin surface contact. An experiment was conducted to compare the heat transfer rate of an elliptical fin to other fin types (tube-tube, rectangular, annular, spiral rod). The results showed the elliptical fin had a higher heat transfer rate. The document reviews several other studies analyzing different fin geometries, heat transfer optimization techniques, and computational fluid dynamics simulations of heat exchangers. It provides background on analyzing heat exchangers using methods like logarithmic mean temperature difference and effectiveness-NTU and discusses prior work optimizing dimensions, materials, and flow conditions to improve heat transfer performance.
A Review on Comparative Study of Thermal Performance of Artificially Roughene...IRJAES
This document reviews research on enhancing heat transfer in solar air heaters through the use of artificial surface roughness. It summarizes findings from several studies that have experimentally analyzed heat transfer performance for different roughness configurations and geometries. The highest average Nusselt numbers were found for a multi V-rib roughness configuration experimentally, while analytical models predicted higher values for end-of-side roughened collectors. A roughness Reynolds number of around 24 was found to give optimal thermal-hydraulic performance across a range of studies.
Assessment of Performance Characteristic of Solar Air Heater with Assorted Ge...IJERA Editor
Artificial roughness is an efficient way for increasing the heat transfer rate in solar air heater with the
corresponding improvement in its thermal performance. A viscous sub-layer is responsible for the low heat
transfer coefficient between absorber plate and flowing air. Repeated ribs in form of artificial roughness are an
effective way to increase the heat transfer rate and improving the performance of solar air heater. Artificial
roughness of the absorber plate is much economical and effective way to improve the thermal performance of
solar air heater. Several investigators have done various investigations to improve heat transfer coefficient with
little penalty of friction factor. They have also developed different correlation for heat transfer coefficient and
friction factor. The correlations developed for heat transfer and friction factor by various investigators have been
reviewed and presented.
Effect of artificial roughness on heat transfer and friction factor charIAEME Publication
1) The study examines the effect of adding transverse ribs to the absorber plate of a double pass solar air heater on heat transfer and friction factor characteristics.
2) Maximum heat transfer and friction factor occurred at a relative roughness pitch of 10, with heat transfer enhanced 1.6 times over a smooth plate.
3) Artificial roughness is used to increase turbulence and break the laminar sub-layer on the absorber plate, improving heat transfer and thermal efficiency.
IRJET- Review of Convection and Magnetohydrodynamic Mixed Convection Heat Tra...IRJET Journal
This document provides a review of recent research on enhancing heat transfer through convection and magnetohydrodynamic mixed convection. It discusses two main techniques: using extra surfaces like inserts to disrupt thermal boundary layers, and applying magnetic fields in magnetohydrodynamic mixed convection systems. The review summarizes several studies on each technique, finding that extra surfaces generally enhance heat transfer by inducing turbulence, while magnetic fields can both enhance and suppress heat transfer depending on parameters. It concludes that both techniques show promise for improving thermal efficiency and optimizing heat exchanger design.
A Review on Experimental and CFD Analysis for Heat Transfer Enhancement in He...IRJET Journal
This document reviews experimental and computational fluid dynamics (CFD) analyses that have evaluated methods to enhance heat transfer in heat exchanger tubes. Specifically, it focuses on the use of drilled twisted tape inserts of various geometries within the tubes. It provides background on heat exchangers and heat transfer enhancement techniques, including passive techniques like twisted tape inserts. The literature review summarizes several studies that have examined twisted tape inserts computationally or experimentally, finding that inserts can increase turbulence and heat transfer but also pressure drop. The present study aims to contribute additional CFD and experimental analysis of drilled twisted tape inserts of different dimensions to further understand their impact on heat transfer and fluid friction characteristics in heat exchanger tubes.
IRJET- Numerical Analysis for Effect of Different Length Combination of Turbu...IRJET Journal
This document describes a numerical analysis of the effect of different length combinations of twisted tape and wire coil turbulators on heat transfer, pressure drop, and friction factor in a double pipe heat exchanger. Five combinations of twisted tape and wire coil lengths were analyzed (25-75%, 30-70%, 35-65%, 40-60%, 45-55%) using computational fluid dynamics software. The results were compared to existing studies on enhancing heat transfer using twisted tape and wire coil inserts in heat exchanger pipes. Key findings included increased heat transfer coefficients and Nusselt numbers but also higher friction factors compared to a plain pipe.
Effect of artificial roughness on Thermal and Thermohydraulic efficiency in R...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Analysis of Heat Generation in Double Pipe Heat Exchanger: An Experimental Ev...IRJET Journal
This document summarizes research on analyzing heat generation in a double pipe heat exchanger with an elliptical fin surface contact. An experiment was conducted to compare the heat transfer rate of an elliptical fin to other fin types (tube-tube, rectangular, annular, spiral rod). The results showed the elliptical fin had a higher heat transfer rate. The document reviews several other studies analyzing different fin geometries, heat transfer optimization techniques, and computational fluid dynamics simulations of heat exchangers. It provides background on analyzing heat exchangers using methods like logarithmic mean temperature difference and effectiveness-NTU and discusses prior work optimizing dimensions, materials, and flow conditions to improve heat transfer performance.
A Review on Comparative Study of Thermal Performance of Artificially Roughene...IRJAES
This document reviews research on enhancing heat transfer in solar air heaters through the use of artificial surface roughness. It summarizes findings from several studies that have experimentally analyzed heat transfer performance for different roughness configurations and geometries. The highest average Nusselt numbers were found for a multi V-rib roughness configuration experimentally, while analytical models predicted higher values for end-of-side roughened collectors. A roughness Reynolds number of around 24 was found to give optimal thermal-hydraulic performance across a range of studies.
Assessment of Performance Characteristic of Solar Air Heater with Assorted Ge...IJERA Editor
Artificial roughness is an efficient way for increasing the heat transfer rate in solar air heater with the
corresponding improvement in its thermal performance. A viscous sub-layer is responsible for the low heat
transfer coefficient between absorber plate and flowing air. Repeated ribs in form of artificial roughness are an
effective way to increase the heat transfer rate and improving the performance of solar air heater. Artificial
roughness of the absorber plate is much economical and effective way to improve the thermal performance of
solar air heater. Several investigators have done various investigations to improve heat transfer coefficient with
little penalty of friction factor. They have also developed different correlation for heat transfer coefficient and
friction factor. The correlations developed for heat transfer and friction factor by various investigators have been
reviewed and presented.
Effect of artificial roughness on heat transfer and friction factor charIAEME Publication
1) The study examines the effect of adding transverse ribs to the absorber plate of a double pass solar air heater on heat transfer and friction factor characteristics.
2) Maximum heat transfer and friction factor occurred at a relative roughness pitch of 10, with heat transfer enhanced 1.6 times over a smooth plate.
3) Artificial roughness is used to increase turbulence and break the laminar sub-layer on the absorber plate, improving heat transfer and thermal efficiency.
IRJET- Review of Convection and Magnetohydrodynamic Mixed Convection Heat Tra...IRJET Journal
This document provides a review of recent research on enhancing heat transfer through convection and magnetohydrodynamic mixed convection. It discusses two main techniques: using extra surfaces like inserts to disrupt thermal boundary layers, and applying magnetic fields in magnetohydrodynamic mixed convection systems. The review summarizes several studies on each technique, finding that extra surfaces generally enhance heat transfer by inducing turbulence, while magnetic fields can both enhance and suppress heat transfer depending on parameters. It concludes that both techniques show promise for improving thermal efficiency and optimizing heat exchanger design.
A Review on Experimental and CFD Analysis for Heat Transfer Enhancement in He...IRJET Journal
This document reviews experimental and computational fluid dynamics (CFD) analyses that have evaluated methods to enhance heat transfer in heat exchanger tubes. Specifically, it focuses on the use of drilled twisted tape inserts of various geometries within the tubes. It provides background on heat exchangers and heat transfer enhancement techniques, including passive techniques like twisted tape inserts. The literature review summarizes several studies that have examined twisted tape inserts computationally or experimentally, finding that inserts can increase turbulence and heat transfer but also pressure drop. The present study aims to contribute additional CFD and experimental analysis of drilled twisted tape inserts of different dimensions to further understand their impact on heat transfer and fluid friction characteristics in heat exchanger tubes.
IRJET- Numerical Analysis for Effect of Different Length Combination of Turbu...IRJET Journal
This document describes a numerical analysis of the effect of different length combinations of twisted tape and wire coil turbulators on heat transfer, pressure drop, and friction factor in a double pipe heat exchanger. Five combinations of twisted tape and wire coil lengths were analyzed (25-75%, 30-70%, 35-65%, 40-60%, 45-55%) using computational fluid dynamics software. The results were compared to existing studies on enhancing heat transfer using twisted tape and wire coil inserts in heat exchanger pipes. Key findings included increased heat transfer coefficients and Nusselt numbers but also higher friction factors compared to a plain pipe.
Effect of artificial roughness on Thermal and Thermohydraulic efficiency in R...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Experimental analysis of heat transfer enhancementin circulariaemedu
This document summarizes an experimental study on enhancing heat transfer in a circular double tube heat exchanger using rectangular inserts. Air was passed through the inner tube while hot water flowed through the outer tube. Heat transfer coefficients and friction factors were determined for the plain tube and with inserts. The results showed that heat transfer was enhanced by 0.9 to 1.9 times with the inserts due to flow disruption, while friction factors increased by 1 to 1.7 times. Heat transfer coefficients increased with Reynolds number whereas friction factors decreased. Validation experiments on a plain tube agreed well with theoretical predictions within 10% uncertainty.
The Effect of insertion of different geometries on heat transfer performance ...IJMER
Abstract: Under turbulent flow conditions, the increase in heat transfer rate is more significant than that under laminar flow conditions. The turbulent effects become a dominant factor over secondary flow at higher Reynolds number. The turbulent flow can be produced by inserting different geometries in the circular pipe. This study focuses on the various methods or geometries used to produce turbulent geometries and its effect on the heat transfer. The turbulent generators with different geometrical
configurations have been used as one of the passive heat transfer enhancement techniques and are the most widely used in tubes in several heat transfer applications. Insertion of such geometries may lead to increase the friction factor and pressure drop which directly enhances the heat transfer characteristics.
IRJET- Experimental Analysis of Circular Perforated Fin Arrays by Forced Conv...IRJET Journal
This document summarizes an experimental analysis of heat transfer from circular perforated fin arrays under forced convection using a wind tunnel. Trapezoidal microfin arrays with circular perforations were selected and designed using Taguchi Method. Experiments were conducted in a wind tunnel on three test specimens - a solid rectangular fin array and two trapezoidal perforated fin arrays with different perforation pitches. The perforated fin arrays showed higher overall efficiency and effectiveness compared to the solid fin array. Maximum overall efficiency was obtained for the array with 5mm perforation pitch at an air velocity of 2m/s and heat input of 150W. Optimum effectiveness was obtained for the array with 7mm pitch at 2m/s and 120W input
IRJET-Numerical Investigation of Heat Performance Enhancement for a Double-Pi...IRJET Journal
This document presents a numerical investigation of heat transfer enhancement in a double-pipe heat exchanger with continuous helical baffles in the annulus and either water or alumina nanofluid as the working fluid. The study varies baffle spacing, mass flow rate, and nanofluid concentration to analyze their effects on heat transfer rate, pressure drop, and thermal performance. Results show that adding helical baffles increases the fluid flow path and turbulence, enhancing heat transfer. Replacing water with nanofluid further improves heat transfer while also increasing pressure drop. Graphs comparing the different configurations are presented and agree with previous research findings. The goal is to optimize baffle design and nanofluid parameters to maximize heat transfer rate and performance for practical
Review of Convective Heat Transfer from Plate Fins Under Natural and Mixed Co...IRJET Journal
This document reviews research on convective heat transfer from plate fins under natural and mixed convection conditions. It summarizes several previous studies that investigated the effects of fin geometry (such as fin length, height, width, spacing, thickness) and operating parameters (such as heat supplied, temperature difference) on heat transfer. The studies found that convective heat transfer increases with fin spacing until an optimal spacing is reached, beyond which further increases in spacing decrease heat transfer. Inclination angle and mixed convection were also found to impact heat transfer. The document provides background on using fins to dissipate heat from electronic devices and explores parameters that most affect natural convective heat transfer within constrained heat sink dimensions.
IRJET- Effect of Wavy Tube on Heat Transfer in a Concentric Tube Heat Exch...IRJET Journal
This document provides a review of research on using a wavy inner tube in a concentric tube heat exchanger to enhance heat transfer. It first discusses different heat transfer augmentation techniques, including active, passive and compound methods. It then reviews several previous studies that experimentally and numerically examined heat transfer performance of wavy tube heat exchangers. These studies found that a wavy inner tube could increase heat transfer by over 100% compared to a plain tube by generating swirl flow and turbulence. The document also reviews research on other passive techniques like wire coil inserts and their effects on heat transfer and pressure drop. Overall, the review shows that wavy tube and other passive inserts can significantly enhance heat transfer in heat exchangers.
Experimental and computational investigation of low cost standing wave thermo...IAEME Publication
This document presents experimental and computational investigation of a low-cost standing wave thermoacoustic refrigerator. Experimentally, a maximum temperature difference of 11K was obtained using a glass fiber stack with glass capillary tube spacers located at 0.15m from the speaker inlet. Computational fluid dynamics analysis using similar conditions obtained a temperature difference of 6K, in good agreement with experimental results. The study aims to develop an inexpensive standing wave thermoacoustic refrigerator design using readily available materials.
This document summarizes a numerical simulation study of heat transfer enhancement in a tube fitted with rod helical tape swirl generators. The study uses ANSYS Fluent to model heat transfer and flow characteristics of air flowing inside a circular tube with different tube insert configurations. Results are compared to experimental and analytical calculations from other studies. Enhanced heat transfer is observed with decreasing twist ratio of the helical tape inserts. Heat flux is also found to be more uniform along the tube length with the inserts.
This document summarizes a study on improving the cooling efficiency of fins in a two-stage reciprocating compressor through finite element analysis and dimensional modification. The existing annular fins are made of aluminum alloy. A finite element model of the fins is created in ANSYS to analyze temperature distribution over time under natural convection conditions. The results show the fins reach room temperature in 30 minutes. The fins are then modified by increasing the number of fins from 11 to 13. Finite element analysis of the modified fins shows cooling time is reduced to 22 minutes. In conclusion, modifying the fin geometry through additional fins improves the cooling rate of the reciprocating compressor.
A Review- Comparative Study of Thermal and Hydrostatic Performance Analysis O...IRJET Journal
This document summarizes research comparing the thermal and hydrostatic performance of helical coil heat exchangers and straight tube heat exchangers. It first provides background on heat exchangers and discusses how helical coils offer advantages over straight tubes, including higher heat transfer coefficients and more compact designs. It then reviews several previous studies that have found helical coils provide higher heat transfer rates compared to straight tubes. Specifically, one study found heat transfer increased up to 3.955 times with corrugated tubes compared to smooth tubes. Another study found Nusselt numbers and friction factors increased up to 117% and 254% respectively when both inner and outer tubes were corrugated compared to only the inner tube being corrugated.
IRJET- A Reviw on Different Geometrical Fins and their Effect on Heat Tra...IRJET Journal
This document summarizes research on different geometric fin designs and their effect on heat transfer rates. It discusses how fins are used to increase surface area and improve heat transfer. Various fin geometries are described including longitudinal, radial, and pin fins. The performance of fins is evaluated using metrics like fin effectiveness and efficiency. Higher thermal conductivity materials, thinner fins with closer spacing, and conditions with lower heat transfer coefficients can improve fin performance. The document reviews several studies on topics like annular fins, dimpled pin fins, and modeling transient heat transfer in piston bore fins.
HEAT TRANSFER CO EFFICIENT VS HEAT FLOW RATE BY FORCED CONVECTIONTajammul Kamal
This document is a project report submitted by a student for their diploma in petrochemical engineering. It investigates heat transfer coefficients and heat flow rates through forced convection. Specifically, it looks at optimizing the design of heat sinks by considering factors like fin shape, thickness, spacing, and their effects on thermal resistance and heat dissipation. It provides background on previous related studies and the importance of heat transfer in applications like electronics cooling. The goal is to develop equations to determine the optimum specifications of fins in a heat sink based on parameters like the Biot number, heat transfer coefficient, and fin shape.
Experimental Analysis Of Heat Transfer From Square Perforated Fins In Stagger...IJERA Editor
This project gives the experimental analysis of heat transfer over a flat surface equipped with Square perforated
pin fins in staggered arrangement in a rectangular channel. The Fin dimensions are 100mm in height & 25mm in
width. The range of Reynolds number is fixed & about 13,500– 42,000, the clearance ratio (C/H) 0, 0.33 and 1,
the inter-fin spacing ratio (Sy /D) 1.208, 1.524, 1.944 and 3.417. Sy i.e. stream wise distance is varies and Sx i.e.
span wise distance is constant. The friction factor, enhancement efficiency and heat transfer correlate in
equations with each other. Here we are comparing Square pin fins with cylindrical pin fins. Staggered
arrangement and perforation will enhance the heat transfer rate. Clearance ratio and inter-fin spacing ratio affect
on Enhancement efficiency. Both lower clearance ratio and lower inter-fin spacing ratio and comparatively lower
Reynolds number give higher thermal performance. Friction factor & Nusselt number are Key parameter which
relates with efficiency enhancement and heat transfer rate.
Design of vertical axis wind turbine for harnessing optimum powerIAEME Publication
The document discusses the design and testing of a vertical axis wind turbine with a sloped wind reducer to increase wind speed and optimize power generation. Experiments were conducted with wind reducers of various slopes in a wind tunnel. The results showed that a 300 sloped reducer increased wind speed by 1.5 times and power output by 3.38 times compared to no reducer. Based on these findings, the authors constructed a vertical axis wind turbine with a 10-foot tall, 10-foot long, 300 sloped glass reinforced plastic reducer.
This document summarizes an experimental study on heat transfer enhancement from surface roughness at laminar flow. Specifically, it examines using circular and oval dimples on an aluminum plate to increase heat transfer from the plate to air flowing over it at Reynolds numbers from 600 to 2000. The study finds that both circular and oval dimples enhance heat transfer compared to a flat plate, while maintaining equivalent or lower pressure drops. The experimental results are validated by comparing the measured Nusselt numbers to theoretical values for a plain vertical plate under laminar flow conditions. In general, the dimpled surfaces increase thermal performance without significantly increasing pressure drops compared to a smooth surface.
IRJET- Experimental Analysis of Convective Heat Transfer Augmentation of Bi-M...IRJET Journal
This document provides a literature review of research on bi-metallic plate heat exchangers to enhance convective heat transfer. It discusses 8 studies that experimentally analyzed heat transfer coefficients and pressure drops of different combinations of bi-metallic plates under forced convection. The goal of improving heat transfer efficiency while minimizing pressure losses is important for industries using such heat exchangers like power plants, refrigeration, and chemical processes. The document focuses on reviewing work done to optimize the design of bi-metallic heat exchangers.
CIRCULAR FINS WITH SLANTED BLADES: UNIFORM HEAT FLUX AND ISOTHERMAL PROCESSES IAEME Publication
This paper investigates experimentally the heat transfer enhancement process over external surface of copper pipe with circular fins attached on the outer surface (heat exchanger) in rectangular channel with air cross-flow. Four types of circular fins were used in the experiments with 32 mm in. I.D., 92 mm. O.D and 1 mm. thick attached on copper pipe. Each type has five (5) circular fins. 1st type has five (5) fins without slanted blades, 2nd type has five (5) slanted blades per one fin, 3rd type has seven (7) slanted blades per one fin and 4th type has nine (9) slanted blades per one fin.
FLUID FLOW ANALYSIS IN AIR DUCT FLOW WITH AND WITHOUT INTERNAL THREADS USING ...IAEME Publication
Computational heat transfer flow modeling is one of the great challenges in the classical sciences. As with most problems in engineering, the interest in the heat transfer augmentation is increasing due to its extreme importance in various industrial applications. This paper deals with the analysis of heat transfer for fluid flowing through the pipe with and without internal threads using CFD. Using CFD codes for modeling the heat and fluid flow is an efficient tool for predicting equipment performance. CFD offers a convenient means to study the detailed flows and heat exchange processes, which take place inside the tube. Simulations were carried out using commercial CFD software ANSYS Fluent version 14.5. Friction factor and Nusselt number for air flowing through the specified tube (internal diameter = 0.005 m, length = 0.1 m) were obtained first for the plain tube and then for the tube with internal threads with pitch 5mm in the Reynolds number range of 2000 to 5000. Finally results will be compared to available experimental and analytical calculations. The data obtained by simulation are matching with the literature value for a plain tube with the discrepancy of less than plus or minus 5% for Nusselt number and for the friction factor.
Enhanced heat transfer for the tube with internal threads has been observed. Heat flux is more uniform all along the tube and decreases uniformly towards the center.
Assessment of Performance Characteristic of Solar Air Heater with Assorted Ge...IJERA Editor
Artificial roughness is an efficient way for increasing the heat transfer rate in solar air heater with the
corresponding improvement in its thermal performance. A viscous sub-layer is responsible for the low heat
transfer coefficient between absorber plate and flowing air. Repeated ribs in form of artificial roughness are an
effective way to increase the heat transfer rate and improving the performance of solar air heater. Artificial
roughness of the absorber plate is much economical and effective way to improve the thermal performance of
solar air heater. Several investigators have done various investigations to improve heat transfer coefficient with
little penalty of friction factor. They have also developed different correlation for heat transfer coefficient and
friction factor. The correlations developed for heat transfer and friction factor by various investigators have been
reviewed and presented.
A Detailed Review on Artificial Roughness Geometries for Optimizing Thermo-Hy...IJMER
It is well known fact that the heat transfer coefficient between the absorber surface of solar air collector & flowing fluid i.e. air can be improved by providing artificial roughness geometry on heat transfer surface (absorber surface).In this way the Thermal efficiency is increased. But at the same time due to roughness geometry pumping power of solar air collector in increased due to fictional losses in duct. So it necessary to examine the shape, size & flow pattern of various roughness elements to get maximum efficiency with minimum frictional losses. Therefore the selection of roughness geometry has to be based on the parameter that takes into account both Thermal & Hydraulic (friction) performance i.e. Thermo-hydraulic Performance of Solar air collector. Number of roughness elements has been investigated on heat transfer & friction characteristics of solar air collectors. In this paper, reviews of various artificial roughness elements used as passive heat transfer techniques, in order to improve Thermo-hydraulic performance of solar air collectors is reviewed & presented. Correlations developed by various researchers with the help of experimental results for heat transfer & friction factor for solar air collector by taking different roughness geometries are given & these correlations are useful to predict the Thermo-hydraulic performance of solar air collector having roughened ducts. The objective of this paper is also the awareness of effect of various types’ roughness geometries on heat
IRJET- CFD Study of Different Turbulent Parameters for a Radiator in Louv...IRJET Journal
This study uses computational fluid dynamics (CFD) to analyze the effects of changing louver angle (24 and 29 degrees) and inlet velocity (4-8 m/s) on turbulent parameters for a radiator with louvered fins. The results show that turbulent intensity and length increase with higher inlet velocity and are generally higher for the 29 degree louver angle compared to 24 degrees. The objective is to understand how louver angle and velocity affect boundary layer breaking and heat transfer performance through changes in turbulence.
Performance evaluations of two pass solar air heater using 60â° inclinedv-sh...inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Experimental analysis of heat transfer enhancementin circulariaemedu
This document summarizes an experimental study on enhancing heat transfer in a circular double tube heat exchanger using rectangular inserts. Air was passed through the inner tube while hot water flowed through the outer tube. Heat transfer coefficients and friction factors were determined for the plain tube and with inserts. The results showed that heat transfer was enhanced by 0.9 to 1.9 times with the inserts due to flow disruption, while friction factors increased by 1 to 1.7 times. Heat transfer coefficients increased with Reynolds number whereas friction factors decreased. Validation experiments on a plain tube agreed well with theoretical predictions within 10% uncertainty.
The Effect of insertion of different geometries on heat transfer performance ...IJMER
Abstract: Under turbulent flow conditions, the increase in heat transfer rate is more significant than that under laminar flow conditions. The turbulent effects become a dominant factor over secondary flow at higher Reynolds number. The turbulent flow can be produced by inserting different geometries in the circular pipe. This study focuses on the various methods or geometries used to produce turbulent geometries and its effect on the heat transfer. The turbulent generators with different geometrical
configurations have been used as one of the passive heat transfer enhancement techniques and are the most widely used in tubes in several heat transfer applications. Insertion of such geometries may lead to increase the friction factor and pressure drop which directly enhances the heat transfer characteristics.
IRJET- Experimental Analysis of Circular Perforated Fin Arrays by Forced Conv...IRJET Journal
This document summarizes an experimental analysis of heat transfer from circular perforated fin arrays under forced convection using a wind tunnel. Trapezoidal microfin arrays with circular perforations were selected and designed using Taguchi Method. Experiments were conducted in a wind tunnel on three test specimens - a solid rectangular fin array and two trapezoidal perforated fin arrays with different perforation pitches. The perforated fin arrays showed higher overall efficiency and effectiveness compared to the solid fin array. Maximum overall efficiency was obtained for the array with 5mm perforation pitch at an air velocity of 2m/s and heat input of 150W. Optimum effectiveness was obtained for the array with 7mm pitch at 2m/s and 120W input
IRJET-Numerical Investigation of Heat Performance Enhancement for a Double-Pi...IRJET Journal
This document presents a numerical investigation of heat transfer enhancement in a double-pipe heat exchanger with continuous helical baffles in the annulus and either water or alumina nanofluid as the working fluid. The study varies baffle spacing, mass flow rate, and nanofluid concentration to analyze their effects on heat transfer rate, pressure drop, and thermal performance. Results show that adding helical baffles increases the fluid flow path and turbulence, enhancing heat transfer. Replacing water with nanofluid further improves heat transfer while also increasing pressure drop. Graphs comparing the different configurations are presented and agree with previous research findings. The goal is to optimize baffle design and nanofluid parameters to maximize heat transfer rate and performance for practical
Review of Convective Heat Transfer from Plate Fins Under Natural and Mixed Co...IRJET Journal
This document reviews research on convective heat transfer from plate fins under natural and mixed convection conditions. It summarizes several previous studies that investigated the effects of fin geometry (such as fin length, height, width, spacing, thickness) and operating parameters (such as heat supplied, temperature difference) on heat transfer. The studies found that convective heat transfer increases with fin spacing until an optimal spacing is reached, beyond which further increases in spacing decrease heat transfer. Inclination angle and mixed convection were also found to impact heat transfer. The document provides background on using fins to dissipate heat from electronic devices and explores parameters that most affect natural convective heat transfer within constrained heat sink dimensions.
IRJET- Effect of Wavy Tube on Heat Transfer in a Concentric Tube Heat Exch...IRJET Journal
This document provides a review of research on using a wavy inner tube in a concentric tube heat exchanger to enhance heat transfer. It first discusses different heat transfer augmentation techniques, including active, passive and compound methods. It then reviews several previous studies that experimentally and numerically examined heat transfer performance of wavy tube heat exchangers. These studies found that a wavy inner tube could increase heat transfer by over 100% compared to a plain tube by generating swirl flow and turbulence. The document also reviews research on other passive techniques like wire coil inserts and their effects on heat transfer and pressure drop. Overall, the review shows that wavy tube and other passive inserts can significantly enhance heat transfer in heat exchangers.
Experimental and computational investigation of low cost standing wave thermo...IAEME Publication
This document presents experimental and computational investigation of a low-cost standing wave thermoacoustic refrigerator. Experimentally, a maximum temperature difference of 11K was obtained using a glass fiber stack with glass capillary tube spacers located at 0.15m from the speaker inlet. Computational fluid dynamics analysis using similar conditions obtained a temperature difference of 6K, in good agreement with experimental results. The study aims to develop an inexpensive standing wave thermoacoustic refrigerator design using readily available materials.
This document summarizes a numerical simulation study of heat transfer enhancement in a tube fitted with rod helical tape swirl generators. The study uses ANSYS Fluent to model heat transfer and flow characteristics of air flowing inside a circular tube with different tube insert configurations. Results are compared to experimental and analytical calculations from other studies. Enhanced heat transfer is observed with decreasing twist ratio of the helical tape inserts. Heat flux is also found to be more uniform along the tube length with the inserts.
This document summarizes a study on improving the cooling efficiency of fins in a two-stage reciprocating compressor through finite element analysis and dimensional modification. The existing annular fins are made of aluminum alloy. A finite element model of the fins is created in ANSYS to analyze temperature distribution over time under natural convection conditions. The results show the fins reach room temperature in 30 minutes. The fins are then modified by increasing the number of fins from 11 to 13. Finite element analysis of the modified fins shows cooling time is reduced to 22 minutes. In conclusion, modifying the fin geometry through additional fins improves the cooling rate of the reciprocating compressor.
A Review- Comparative Study of Thermal and Hydrostatic Performance Analysis O...IRJET Journal
This document summarizes research comparing the thermal and hydrostatic performance of helical coil heat exchangers and straight tube heat exchangers. It first provides background on heat exchangers and discusses how helical coils offer advantages over straight tubes, including higher heat transfer coefficients and more compact designs. It then reviews several previous studies that have found helical coils provide higher heat transfer rates compared to straight tubes. Specifically, one study found heat transfer increased up to 3.955 times with corrugated tubes compared to smooth tubes. Another study found Nusselt numbers and friction factors increased up to 117% and 254% respectively when both inner and outer tubes were corrugated compared to only the inner tube being corrugated.
IRJET- A Reviw on Different Geometrical Fins and their Effect on Heat Tra...IRJET Journal
This document summarizes research on different geometric fin designs and their effect on heat transfer rates. It discusses how fins are used to increase surface area and improve heat transfer. Various fin geometries are described including longitudinal, radial, and pin fins. The performance of fins is evaluated using metrics like fin effectiveness and efficiency. Higher thermal conductivity materials, thinner fins with closer spacing, and conditions with lower heat transfer coefficients can improve fin performance. The document reviews several studies on topics like annular fins, dimpled pin fins, and modeling transient heat transfer in piston bore fins.
HEAT TRANSFER CO EFFICIENT VS HEAT FLOW RATE BY FORCED CONVECTIONTajammul Kamal
This document is a project report submitted by a student for their diploma in petrochemical engineering. It investigates heat transfer coefficients and heat flow rates through forced convection. Specifically, it looks at optimizing the design of heat sinks by considering factors like fin shape, thickness, spacing, and their effects on thermal resistance and heat dissipation. It provides background on previous related studies and the importance of heat transfer in applications like electronics cooling. The goal is to develop equations to determine the optimum specifications of fins in a heat sink based on parameters like the Biot number, heat transfer coefficient, and fin shape.
Experimental Analysis Of Heat Transfer From Square Perforated Fins In Stagger...IJERA Editor
This project gives the experimental analysis of heat transfer over a flat surface equipped with Square perforated
pin fins in staggered arrangement in a rectangular channel. The Fin dimensions are 100mm in height & 25mm in
width. The range of Reynolds number is fixed & about 13,500– 42,000, the clearance ratio (C/H) 0, 0.33 and 1,
the inter-fin spacing ratio (Sy /D) 1.208, 1.524, 1.944 and 3.417. Sy i.e. stream wise distance is varies and Sx i.e.
span wise distance is constant. The friction factor, enhancement efficiency and heat transfer correlate in
equations with each other. Here we are comparing Square pin fins with cylindrical pin fins. Staggered
arrangement and perforation will enhance the heat transfer rate. Clearance ratio and inter-fin spacing ratio affect
on Enhancement efficiency. Both lower clearance ratio and lower inter-fin spacing ratio and comparatively lower
Reynolds number give higher thermal performance. Friction factor & Nusselt number are Key parameter which
relates with efficiency enhancement and heat transfer rate.
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Generative AI leverages algorithms to create various forms of content
I0364050063
1. International Journal of Engineering Science Invention
ISSN (Online): 2319 – 6734, ISSN (Print): 2319 – 6726
www.ijesi.org Volume 3 Issue 6ǁ June 2014 ǁ PP.50-63
www.ijesi.org 50 | Page
Enhancement of Heat Transfer Using Artificial Roughness In
Solar Air Heater
D.S. Rawat1
, Dr. A. R. Jaurker2
;
1
Researcher, Department Of Mechanical Engineering, Jabalpur Engineering College Jabalpur (India).
2
Professor, Department Of Mechanical Engineering, Jabalpur Engineering College Jabalpur (India).
E- Mail Of Corresponding Author:ds_rawat1@yahoo.com
ABSTRACT: Heat transfer plays an important role in the field of thermal engineering. Heat transfer involves
transfer of heat energy without transfer of mass and plays most important role in the field of power plant,
refrigeration and air conditioning, electric transformer, and electronic equipment etc., Heat transfer takes place
by three modes i.e. Conduction, convection and radiation. Conduction and convection mode need the working
medium for heat transfer whereas radiation mode of heat transfer takes placeamong space bodies with or
without medium. The convection mode of heat transfer is mostly used in industrial field where liquid; gases and
air are the heat transfer medium is used. It is found that the convective heat transfer coefficient between hot gas
to metal or hot metal to air is low. Due to the low value of heat transfer coefficient, the performance of the heat
transfer system which is working with air as a working fluid is low. A lot of passive and active techniques are
investigated to increase the efficiency or the heat transfer performance of system. Artificial roughness is the
most important technique for enhancing the heat transfer among heat transfer techniques. Artificial roughness
is defined by non-dimensional parameters as relative roughness pitch, relative roughness height and relative
modifications for easy of analysis of system, comprising and evaluating of systems. A lot of research work is
found in the field of enhancement of heat transfer by application of artificial roughness in the form of ribs as
listed in details. This paper covers the introduction of artificial roughness in the field of heat transfer in various
shapes and modifications made by researchers. This paper covers the literature of roughened heat transfer
system by different types of artificial roughness, their technique/ correlations to evaluate the heat transfer rate,
and analyse the results, which are very helpful in the field of heat transfer engineering, to selection of
roughness, to predict the performance of system and compare the systems. This paper conclude that artificial
roughness in the form of different typed of ribs used in heat transferring system, increase heat transfer rate
around 2 to 4 times as compares to conventional type system.
KEYWORDS: -Heat Transfer, Artificial Roughness, passive and active techniques, relative roughness pitch,
relative roughness height.
I. INTRODUCTION
Energy plays an important role in the development processes ofthe world. There are two types of
energy resources one is alternative source of energy and other is fossil fuel sources. Since the rapid depilation of
fossil Fuel resources forces the investigator to search new resources of energy. Solar energy is the ultimate
source of energy which has most promising, large quantity in nature, available free of cost and pollution free in
nature, available at anywhere. Solar energy is collected by solar collector’s i.e. solar air heater, solar water
heater and photo voltaic methods. As the geographical location of India nature gives most efficient solar
radiation over the country. India has agricultural environment and its economy depends on agriculture and
industrial field. In view of Indian economically viability, solar air heater is the most economical solar collecting
device in the field of crop drying, seasoning of wood, solar drier and maintaining the moderate temperature at
industrial processes in winter season. Solar air heater is simple in design, easy of manufacturing and simple to
use. Literature shows that heat transfer rate between the air and metallic plate is low, which leads to lower
efficiency of the solar air heaters. Literature shows one of the most viable techniques of increasing the heat
transfer rate and thermal efficiency of solar air heater is the application of artificial roughness in the form of ribs
as shown in figure 1.This paper introducing the artificial roughness to enhance the heat transfer rate and
mythology adopted by various investigators to achieve its goal.
2. Enhancement of Heat Transfer Using…
www.ijesi.org 51 | Page
II.ROUGHNESS GEOMETRIES IN HEAT TRANSFER FIELD
The roughness element may be
[1] Sand grain on heat transfer surface
[2] Two-dimensional ribs
[3] Three dimensional
[4] Grooves
[5] Compounding ribs
[6] Combination of rib and groove rib
[7] Transvers or
[8] Inclined.
[9] Wire fixation;
[10] Expanded wire mesh fixation;
[11] Rib formation by machining process;
[12] Dimple/ protrusion formation and
[13] Inverted u-shaped turbulators.
[14] Z-shaped rib
III. ROUGHNESSAND DUCT PERAMETERS
Artificial roughness is defined by non-dimensional parameters such as
[1] Relative roughness pitch (p/e)
[2] Relative roughness height (e/D)
[3] Angle of attack (α)
[4] Modified shape
Relative roughness pitch (p/e): It the ratio of distance between two consecutive ribs and height of the rib.
Relative roughness height (e/D): It is the ratio of rib height to equivalent diameter of the air passage.
Angle of attack (α): Angle of attack is defined as the inclination of rib with direction of air flow in the duct.
Aspect ratio: Aspect ratio is defined as the ratio of duct width to duct height. This factor also plays a very
crucial role in investigating thermo-hydraulic performance.
Shape of roughness element: The common shape of roughness element is Square, circular, semi-circular,
chamfered, arc shaped wire, dimple or cavity, compound rib-grooved, and v-shaped continuous or broken ribs
with or without gap.
IV. EFFECT OF ROUGHNESS PERAMETERS ON HEAT TRANSFER
4.1 Relative Roughness Pitch (P/e)
roughness pitch is one of the most important key parameter of designing the artificial roughness in the
field of heat transfer. Prasad and saini [1988] conducted an experimental investigation in solar air heater with
artificial roughness plates with different Relative roughness pitches. They show very important phenomena of
flow pattern downstreamof a rib as a function of relative roughness pitch as shown in Fig-1.They observed that
the maximum heat transfer coefficient occurs in vicinity of the reattachment point due to the phenomenon of
separation and reattachment of flow.The position of relative roughness pitch (p/e) for maximum heat transfer
coefficient are listed shown in table.1
Table 1: relative roughness pitch (p/e) for maximum heat transfer rate.
S.NO. Investigators Roughness geometry Value of (p/e) for maximum heat transfer
1. Prasad and saini [1988] Small dia. protrusion wires 10.00
2. Bhagoria et al [2002] Wedge shape rib 07.57
3. Karwa et al [2001] Chamfered rib 07.09
4. Jaurker et al [2006] Rib-grooved 06.00
5. Sahu and bhagoria [2005] 90⁰ broken transverse rib 13.33
6. Karmare [2007] Metal grit rib 17.50
7. Saini and verma [2008] Dimple shaped rib 10.00
8. Varun et al [2008] Combination ribs 08.00
3. Enhancement of Heat Transfer Using…
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4.2 Relative roughness height (e/D)
Relative roughness height is one of the most important key parameter of designing the artificial
roughness in the field of heat transfer. Prasad and saini [1988] conducted an experimental investigation in
solar air heater with artificial roughness plates with different Relative roughness height. They shows very
important phenomena of flow pattern downstream of a rib as a function of relative roughness height as shown in
Fig-2.They found that the flow pattern downstream and effect on the heat transfer and laminar sub layer as the
rib height is changed. Heat transfer rate can be increased by creating local wall turbulence. Taking the rib height
is slightly higher than the transition sub layer thickness can be obtained optimum thermo-hydraulic performance
conditions. The trend for of relative roughness height (e/D) is listed for maximum heat transfer rate in Table. 2
Table 2: Trend of relative roughness height (e/D) for maximum heat transfer rate
S.NO. Investigators Roughness geometry
Value of (e/D) for maximum
heat transfer
1 Prasad and saini [1988]
Small diameter protrusion
wires
0.033
2 Bhagoria et al [2002] Wedge shape rib 0.033
3 Karwa et al [2001] Chamfered rib 0.0441
4 Jaurker et al [2006] Rib-grooved 0.036
5 Karmare and tikekar [2007] Metal grit rib 0.044
6 Saini and verma [2008] Dimple shaped rib 0.0379
7 Momin et al [2002] V-shaped rib 0.034
8 Layek et al [2007] chamfered rib& grooved 0.04
9 Saini and saini [2008] Arc shaped rib 0.0422
Fig. 1. Effect of rib pitch on flow [01]. Fig. 2. Effect of rib height on flow [01].
4. Enhancement of Heat Transfer Using…
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4.3 Angle of attack (α)
Beside of the relative roughness pitch and relative roughness height, it has been experimentally found
by various researchers that, the inclined rib gives higher heat transfer rate than the transverse rib because of the
secondary flow induced by the rib, in addition to break the viscous sub layer and produces local wall turbulence.
In other word the vertices move along the rib so subsequently to join the main stream causing the fluid to enter
near the leading end of the inclined rib. These moving vertices therefore bring in cooler channel fluid in contact
with leading end, raising the heat transfer rate. While the trailing end heat transfer is relatively lower. This
phenomenon gives the strong span wise variation of heat transfer.
Table 2: Trend of Angle of attack (α) for maximum heat transfer rate
S.NO. Investigators Roughness geometry
Angle of attack (α)
for maximum heat
transfer
1 Gupta et al. [1997] Inclined rib 70o
.
2 Karwa et al.[2003] inclined rectangular ribs 60⁰
3 Kumar et al. [2008] discrete w-shaped ribs 45o
4 Lau et al. [1991] V-shape rib 60o
5 Kumar et al. [2011] Discrete inclined discrete rib 60o
6 Sukhmeet singh et al[2011] periodic discrete v-down rib 60o
7 Pongjet promvonge[2010] multiple V- baffle turbulator 600
V. REVIEW OF ROUGHNESS GEOMETRIES
The general arrangement of different types of roughness geometries reported by the various Investigators as
follows.
[1] Wire fixation;
[2] Expanded wire mesh fixation;
[3] Rib formation by machining process;
[4] Dimple/ protrusion formation;
[5] Inverted u-shaped turbulators; and
[6] Z-shaped rib.
Wire fixation :Heat transfer enhancement and friction loss by fixing wire of different shapes, size and
orientation by various investigators as an artificial roughness element on the absorber plate has been discussed
below.
Transverse continuous rib : Prasad and saini [01] [1988] Investigated experimentally, the effect of relative
roughness pitch (p/e) and relative roughness height (e/D) on the heat transfer coefficient and friction factor of
the fully developed turbulent flow in a solar air heater duct with small diameter protrusion wire on absorber
plate. The type and orientation of the geometry is depicted in fig.-5. It observed thatthe average Nusselt number
and average friction factor in the roughened duct were as 2.10, 2.24, 2.38 and 3.08, 3.67, 4.25 times that of
smooth duct for relative roughness height (e/D) of 0.020, 0.027 and 0.033 respectively. It has also been found
that increase in the average Nusselt number and average friction factor in the roughened duct were about 2.38,
2.14, 2.01 and 4.25, 3.39, 2.93 times of that of the smooth duct for a relative roughness pitch (p/e) of 10, 15 and
20 respectively. The maximum enhancement heat transfer coefficient and friction factor were as 2.38 and 4.25
times than that of smooth duct respectively.
Transvers broken ribs : Sahu and bhagoria [02] [2005] Reported the effect on heat transfer coefficient and
thermal Efficiency of solar air heater by providing 90⁰ broken transvers rib on absorber plate. Integral rib
Roughened absorber plate were prepared by fixing wire of 1.5mm diameter over one side of absorber plate as
depicted in fig.-6, with the roughness geometry having pitch (p) range from 10-30mm, height of rib of 1.5mm,
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duct aspect ratio was 8 and Reynolds number of 3000-12000. It was also reported that, heat transfer coefficient
and maximum thermal efficiency obtained as 1.25 to 1.4 times and 83.5% than that of smooth duct respectively.
The maximum enhancement of heat transfer coefficient occurs at pitch of about 20mm. while on other side of
this pitch, the Nusselt Number decreases.
Varun et al [03] [2008] Experimentally investigated the thermal preformation of solar air heater having
roughness element as combination of inclined as well as transverse rib as depicted in Fig.-7, with the Reynolds
number (Re) ranges from 2000-14000,relative roughness pitch (p/e) of 3-8 and relative roughness height (e/D)
of 0.030. It was observed that the optimum thermal performance occurs having the value of relative roughness
pitch (p/e) of 8.
Inclined ribs
Kumar et al. [04][2011]experimental study has been carried out for enhancement of heat transfer
coefficient of a solar air heater having roughened air duct provided with artificial roughness in the form 60o
Discrete inclined rib. Considerably enhancement in heat transfer coefficient has been achieved with such
roughness element. The investigated geometry has been shown in Fig.-8.
Aharwal et al[05] [2008] Investigated the effect of artificial roughness by inclined split rib arrangement in a
rectangular duct in solar air heater depicted in fig.-9, considering the gap of width ratio (g/e) and gap of position
ratio (d/w). The increase in Nusselt number and the friction factor were in the range of 1.48-2.59 times and 2.26-
2.9 times of smooth duct, respectively.
Gupta et al. [06] [1997]carried out an extensive experimental investigation on fluid flow and heat transfer
characteristics of artificially roughened solar air heater ducts with inclined wires as shown in Fig.-10. They
found that maximum heat transfer coefficient occurred for an angle of attack of 60_ whereas the friction factor
maximum for an angle of attack of 70o
.
Fig. 3: Phenomena of Inclined rib
V- shape ribs
Momin et al [07] [2002] Experimentally investigated the effect of relative roughness height and angle
of attack for fixed relative roughness pitch of 10 with the Reynolds number range of 2500- 18000 for a v-shaped
rib as shown in fig.-11. It was found that the rate of increase of the Nusselt number with an increase in Reynolds
number is lower than the rate of increase of the friction factor. It was also found that for the relative roughness
height of 0.034, the v- shaped rib enhanced the value of Nusselt number by 1.14 and 2.30 times over inclined
ribs and smooth plate.
Singh et al. [08] [2011] Experimental investigation on heat transfer and friction in rectangular ducts roughened
with a new configuration of discrete v-rib on one broad wall are presented. The maximum enhancement in
Nusselt number and friction factor has been obtained at relative gap position of 0.65 and is of order of 2.8
and3.0 times of that of the smooth duct, respectively. The investigated geometry has been shown in Fig.-12.
Karwa [09] [2003] Investigated the effect on heat transfer and friction factor by using the Transverse, inclined,
v-continuous and v-discrete rib on absorber plate in solar air heater depicted in Fig.-13, with Reynolds number
range of 2800-15000, relative roughness height (e/D) range of 0.0467 - 0.050 duct aspect ratio range of 7.19-
7.75 at the fixed value of relative roughness pitch (p/e) of 10 and also developed the correlation for Stanton
number and friction factor. The rib in the v-pattern were tested for both pointing upstream (V-up) and (V-down)
to the flow. Enhancement in Stanton number and friction factor over that of the smooth duct was observed of the
order of 65 -90% and 2.68 - 2.94 times, respectively. It is observed that 60⁰ inclined rectangular ribs produces
better results than transvers rib. The enhancement in the Stanton number over the smooth duct was up to 137%,
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147%, 134% and 142% for the V-up continuous, V-down continuous, V-up discrete and V-down discrete rib
arrangement respectively. The friction factor ratio for these arrangements was up to 3.92, 3.65, 2.47 and 2.58
respectively. Based on the equal pumping power, V-down discrete roughness provides the best heat transfer
performance.
Lau et al. [10][1991] studied the effect of V-shaped ribs arrays on turbulent heat transfer and friction of fully
developed flow in a square channel.Fig.14,represents the typical rib configurations. They showed that the 60O
V-
shaped ribs have highest thermal performance.
Fig. 4: Phenomena of V shaped rib
Arc shaped ribs : Saini and saini [11][2008] Experimentally investigated the effect on heat transfer
coefficient and friction factor of relative roughness height (e/D) and angle of attack (α/90) with providing the
arc shaped parallel wire on the absorber plate in solar air heater as depicted in fig.-15, with Reynolds number
(Re) ranges of 2000-17000, relative roughness height (e/D) of 0.0213-0.0422and angle of attack (α/90) of
0.3333-0.6666 for a fixed relative roughness pitch (p/e) of 10. The maximum enhancement in Nusselt number
was obtained as 3.80 times corresponding to the relative angle of attack (α/90) of 0.3333 at relative roughness
height (e/D) of 0.0422. However, increment in the friction factor corresponding to these parameters was found
to be only 1.75 times.
W-shaped rib :Kumar et al. [12] [2008] carried out an experimental investigation to determine the heat
transfer distributions in solar air heater having its absorber plate roughened with discrete w-shaped ribs. The
experiment encompassed Reynolds number (Re) range from3000 to 15,000, rib height (e) values of 0.75 mm
and 1 mm, relative roughness height (e/D) 0.0168 and 0.0225 and relative roughness pitch (p/e) of 10 and angle
of attack (a) 45o
. Thermal performance of roughened solar air collector was compared with that of smooth one
under similar flow conditions and it was reported that thermal performance of the roughened channelwas1.2–1.8
times the smooth channel for range of parameters investigated. Discretization was found to have significant
effect on heat transfer enhancement. The geometry investigated has been shown in Fig.-16.
Expanded Wire Mesh Fixation :Saini and saini [13] [1997] Experimentally investigated the effect on heat
transfer coefficient and friction factor by providing the expanded metal mesh geometry on the absorber plate in
solar air heater as depicted in fig.-17. For fully developed turbulent flow in a rectangular duct with a large aspect
ratio of 11.1 has been found maximum Nusselt number and friction factor corresponding to relative long way
length of mesh and relative short way length of mesh was 46.87, 71.87 and 25, 15 respectively. The maximum
enhancement in Nusselt number and friction factor values were reported of the order of 4 and 5 times to that of
the smooth absorber plate respectively.
Machining Ribs Of Different Shapes : The study of heat transfer and friction factor characteristics of solar
air heater, experimentally investigated by various researchers using integral ribs generated on absorber plate by
machining process reported in literature is discussed in following subsections.
Wedge shaped ribs : Bhagoria [14] [2002] Experimentally investigated the effect of relative roughness pitch
(p/e) relative roughness height (e/D) and wedge angle on heat transfer coefficient and friction factor in solar air
heater rectangular duct roughened with wedge shaped transvers integral rib depicted in fig.-18, taking the range
of relative roughness pitch (p/e) of 60.17ɸ-1.0264
<p/e<12.12, range of relative roughness height (e/D) of 0.015-
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0.033, Reynolds number (Re) range of 3000-18000 and wedge angle (ɸ) was 8-15⁰. It has been observed that
the maximum heat transfer occurs for a relative roughness pitch of about 7.57. While the friction factor
decreased as the relative roughness pitch increased. The maximum enhancement of heat transfer at wedge angle
of about 10⁰. Author reported an enhancement in Nusselt number up to 2.4 times while the fiction factor
increases up to 5.3 times as compared to smooth duct.
Chamfered ribs : Karwa et al [15] [1999] Experimentally investigated the effect ofrepeated integral chamfered
rib roughness on absorber plate as depicted in fig.-19, with rib chamfered angle of -15⁰ to 18⁰ having aspect
ratio of 4.8 to 12, relative roughness pitch (p/e) of 4.5 to 8.5, relative roughness height (e/D) of 0.0141 to 0.0328
and Reynolds number (Re) of 3000 to 20000. The highest heat transfer and friction factor was found for 15⁰
chamfered rib angles. The heat transfer increases with increasing of aspect ratio from 4.65 to9.66 and the
roughness function deceases with the increases in aspect ratio from 4.65 to 7.75. As compared to smooth
absorber plate there was an appreciable increment in the value of thermal efficiency about 10 to 40% with
chamfered rib roughened absorber plate of solar air heater due to enhancement of Nusselt number in order of 50
to 120%. The enhancement in thermal efficiency, fiction factor and Nusselt number were found to be strong
function of the relative roughness height (e/D). The greatest enhancement was found for air heater with the
highest relative roughness height.
COMBINATION OF DIFFERENT INTEGRAL RIB ROUGHNESS ELEMENTS
Jaurker et al [16] [2006] Experimentally investigated the effect on heat transfer and friction factor or fluid flow
characteristics of relative roughness pitch(p/e), relative roughness height(e/D) and relative groove position by
providing rib-grooved artificial roughness on absorber plate in rectangular solar air heater duct as depicted in
fig.-20, withReynolds number(Re) of 3000 to 21000, relative roughness height(e/D) of 0.0181 to0.0363,relative
roughness pitch(p/e) of 4.5 to 10, and groove position to pitch ratio(g/p) of 0.3 to 0.7. It has been observed that
the maximum heat transfer was obtained for a relative roughness pitch (p/e) of 6 and the optimum condition for
heat transfer was found at a groove position of 0.4. It has also been observed that as compared to smooth duct,
the pressure of rib grooved artificial roughness increase the Nusselt number up to 2.75 times, while the friction
factor raised up to 3.61 times in the range of parameters investigated.
Layek et al [17] [2007] Reported the effect on heat transfer and friction factor characteristics with providing
repeated integral transverse chamfered rib-groove roughness on absorber plate in solar air heater with Reynolds
number (Re) of 3000 to 21000, relative roughness pitch (p/e) of 4.5 to 10, chamfered angle of 5 to30⁰, relative
groove position of 0.3 to 0.6 and relative roughness height (e/D) of 0.022, 0.04. It is found that Nusselt number
and friction factor increased by 3.24 times and 3.78 times respectively as compared to smooth duct. Maximum
enhancement of Nusselt number and friction factor was obtained corresponding to relative groove position of
0.4.
Dimple Shaped Geometry : Saini and verma et al [18] [2008] presented the effect of relative roughness
pitch (p/e) and relative roughness height (e/D) of dimple shape roughness geometry on heat transfer and friction
factor as depicted in fig.-21, by taking of Reynolds number (Re) of 2000 to 12000, relative roughness pitch (p/e)
range of 8 to 12 and relative roughness height (e/D) range of 0.018 to0.037. It was found that Nusselt number
and friction factor increases by 1.8 and 1.4 times respectively as compared to smooth duct.
Inverted U-Shaped Tabulators : Bopche and Tandale [19] [2009] Experimentally investigated the effect
on heat transfer and friction factor by providing the inverted U-shaped turbulators on the absorber surface of a
solar air heater duct. The inverted U-shaped tabulator shows appreciable heat transfer enhancement even at low
value of Reynolds number (Re<5000) where rib were inefficient. The maximum enhancement in Nusselt
number and friction factor at the Reynolds number of Re=3800 was the order of 2.388 and 2.50 times
respectively. The maximum enhancement in the Nusselt number and friction factor values compared to the
smooth duct were of the order of 2.82 and 3.72 times respectively. The turbulence generated only in the viscous
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sub-layer region of the boundary layer resulted in better thermo hydraulic performance i.e. maximum heat
transfer enhancement at an affordable friction penalty.
Z-SHAPED GEOMETRY : Sriromrein and Promvong [20][2010]carried out an experimental investigation
to study the heat transfer coefficient and friction factor of a rectangular duct roughened artificially with z-shape
ribs. The roughness geometry is shown in Fig.-22. The 45_ Z-rib provides the highest increase in the heat
transfer rate and the best thermal performance.
Table 3: Rib geometries:
S.NO. INVESTIGATORS Rib Geometries
1 Prasad and saini [01] [1988]
Fig.5Transvers rib
2 Sahu and bhagoria [02] [2005]
Fig.6Transverse broken ribs
3
Varun et al [03] [2008]
Fig.7Inclined and transverse ribs
4 Kumar et al. [04][2011]
Fig.8 Discrete inclined ribs
5 Aharwal et al[05] [2008]
Fig.9 Inclined with gap rib
6 Gupta et al. [06] [1997]
Fig.10Inclined rib
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7 Momin et al [07] [2002]
Fig.11V-Shaped Rib
8 Singh et al. [08] [2011]
Fig. 12 Inverted -V -discrete rib
9
Karwa [09] [2003]
Fig.13 V-Continuous and Discrete
10 Lau et al. [10][1991]
Fig.14 transvers and V-shaped ribs
11
Saini and saini [11][2008]
Fig.15Arc shaped ribs
12
Kumar et al. [12] [2008]
Fig.16Discrete W-shaped ribs
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13 Saini and saini [13] [1997]
Fig.17Expanded wire mesh fixation
14 Bhagoria [14] [2002]
Fig.18Wedge shape rib
15 Karwa et al [15] [1999]
Fig.19Chamfered rib geometry
16 Jaurker et al [16] [2006]
Fig.20Rib-grooved
17
Saini and verma et al [18]
[2008]
Fig.21 Dimple shaped rib
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18
Sriromrein and Promvong
[20][2010]
Fig.22 Z-shaped rib
19
Muluwork et al.[21][2000]
Fig.23 V-discrete rib
20 Atul lanjewar et al[22] [2011]
Fig.24 W-shaped
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VI. CONCLUSION
An attempt has been made in the present paper to report the heat transfer coefficient and friction factor
characteristics of artificially roughened duct in solar air heater using of different shapes of geometry. It can be
concluded that there is a considerable enhancement in heat transfer with little penalty of friction. This is
interesting to see for further work that how Correlations can be developed for heat transfer and Friction factor
for solar air heater ducts having artificial roughness of different geometries for different investigators. These
correlations can be used to predict the thermal efficiency, effective efficiency and then hydraulic performance of
artificial roughened solar air heater ducts. Correlations developed for heat transfer and friction factor of solar air
heater duct having artificial roughness of different geometries by different investigators are also presented in
tabular form. These correlations can be used to predict the thermal efficiency, effective efficiency and hydraulic
performance of artificially roughened solar air heater duct. Information provided in the present paper may be
useful to the beginners in this area of research to find out and optimize the new element geometries for the
maximum enhancement of heat transfer.
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Nomenclature
Ac surface area of absorber plate, m2
B half-length of full V-rib element, m
Cp specific heat of air, J/kg K
D, Dh equivalent or hydraulic diameter of duct, m
e rib height, m
g groove position, m
h heat transfer coefficient, W/m2 K
H depth of air duct, m
I intensity of solar radiation, W/m2
K thermal conductivity of air, W/m K
L length of test section of duct or long way length of
mesh, m
m mass flow rate, kg/s
P pitch, m
DP pressure drop, Pa
qu useful heat flux, W/m2
Qu useful heat gain, W
Ql heat loss from collector, W
Qt heat loss from top of collector, W
S length of discrete rib or short way length of mesh, m
To fluid outlet temperature, K
Ti fluid inlet temperature, K
Ta ambient temperature, K
Tpm mean plate temperature, K
W width of duct, m
Dimensionless parameters
e/D, e/Dh relative roughness height
e/H rib to channel height ratio
f friction factor
g/P relative groove position
Nu Nusselt number
Nus Nusselt number for smooth channel
Nur Nusselt number for rough channel
p/e relative roughness pitch
Pr Prandtl number
Re Reynolds number
St Stanton number
W/H duct aspect ratio
Greek symbols
ɸ rib chamfer/wedge angle, degree
ηth thermal efficiency
μ dynamic viscosity, Ns/m2
ρ density of air, kg/m3
α angle of attack, degree
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