This document summarizes a numerical study of microchannels with internal fins for cooling electronic equipment. Three types of microchannels were studied: square channels with conventional and cross fins, and rectangular channels with conventional fins. Constant heat flux boundary conditions and laminar flow were assumed. Results for average local Nusselt number distribution along the channel length were obtained as a function of fin height ratio. An optimum fin height ratio that maximized heat transfer was found for each microchannel type. Grid independence testing was performed to select the appropriate mesh for the numerical simulations.
This document summarizes a numerical study that examines the effects of fin spacing, fin material, and jet velocity on the heat transfer performance of plate fin heat sinks cooled by impinging air jets. The study considers fin spacings of 2mm, 3mm, and 4mm, and fin materials of aluminum, copper, and steel. Jet velocities of 5m/s, 10m/s, and 15m/s are examined. The results show that heat transfer rate increases with decreasing fin spacing, higher thermal conductivity fin materials like copper, and increasing jet velocity. Copper fins achieved the highest heat transfer rates but are heavier and more expensive than aluminum. A fin spacing of 2mm with aluminum fins and a jet velocity of 15
Analytical and Experimental analysis ofthermal characteristics throughTriangu...IJERA Editor
Microscale heat transfer technique is widely intended for best cooling applications in electronic devices as high
heat transfer coefficients are achieved in microscale convection. In present study, analysis of thermal
characteristics has been carried out by analytical calculations along with experimental investigation for a straight
microchannel heat sink of equilateral triangular cross section of 173.21 μm hydraulic diameter with distilled
water as the working fluid. Designed Heater input watts and Reynolds number based on flow rate are varied for
optimized microchannel geometry. Experimental analysis is carried out under constant heat flux condition. The
microchannels are produced on highly accurate micro wire cut EDM. The Reynolds number is varied from 100
to 700. The major intension for this work is to enhance heat transfer coefficient and minimize pressure drop
across microchannel. The Reynolds number, temperature distribution, pressure distribution, heat transfer
coefficient, hydrodynamic entrance length, thermal entrance length, equivalent thermal resistances parameters
are calculated for microchannel heat sink performance analysis. The results of analytical calculations are verified
with experimental investigation. It is found that heat transfer coefficient and pressure drop increases with
increase in Reynolds numbers and decrease in microchannel heat sink hydraulic diameter. Also channel length is
directly proportional to temperature rise
Electrochemical Redox Cycling Realized by Chromatography Paper-based SensorTELKOMNIKA JOURNAL
In this work, we demonstrated that enhancement of electrochemical current due to
redox cycling could be accomplished by paper-based biosensor without any expensive microfabrication
process. The paper-based sensor had layered structure to generate higher current
than a conventional one. We took advantage of the fact that the paper thickness was
micrometer-sized (180um), and it defined the distance between two electrochemical electrodes
on both sides of the paper. Experimental results showed signatures of the redox cycling, where
the electrochemical current from low concentration molecules could be arbitrarily increased by
decreasing the distance between electrodes. Such a structure was advantageous for detecting
target molecules at very low concentration, proposing a low-cost highly-sensitive biochemcal
sensor.
This document summarizes a study analyzing electronic chip microchannels using ANSYS software. It presents the background on microchannel cooling technology and prior research. It then describes the numerical model setup in ANSYS, including the microchannel geometry, governing equations, and boundary/flow conditions. Results are shown for temperature contours, velocity vectors, pressure drops, and heat transfer coefficients for different materials and pressure drops. The study found that outlet water temperature was highest for a pressure drop of 30 kPa and when the substrate was silicon. Overall, the document analyzes heat transfer in a microchannel heat sink using computational fluid dynamics software.
This document discusses numerical simulations of heat transfer in an annulus tube with internal fins. The simulations solve the governing equations for mass, momentum, energy and turbulence using a k-ε model. Various fin configurations are analyzed by varying the number, shape and size of fins. The results show that heat transfer increases with fin number and height. Trapezoidal fins have higher heat transfer than other shapes. The study aims to determine the optimal fin design for maximum thermal performance in the annulus tube.
This document summarizes an experiment to measure the out-of-plane thermal conductivity of flexible substrate materials like polyethylene naphthalate (PEN) and polyethylene teraphthalate (PET). A steady-state method is used where a heat flux is applied through one copper block in contact with the substrate, and the temperature difference across the substrate is measured. Thermal conductivity values are determined from the temperature differences and heat fluxes for substrates of varying thicknesses. The results indicate low thermal conductivity for flexible substrates, which could challenge thermal management in flexible electronics due to limited heat spreading and lack of active cooling options.
This document discusses heat transfer and thermal transport in lithium-ion battery cells. The key points are:
1) Thermal conduction within lithium-ion battery cells is dominated by the thermal contact resistance between the cathode and separator, which accounts for around 88% of the total thermal resistance.
2) Measured values of the thermal contact resistance between the cathode and separator agree with theoretical models that account for weak adhesion between the materials.
3) Chemically bridging the cathode-separator interface using an amine reduces the thermal contact resistance by 4 times without negatively impacting electrochemical performance, resulting in an expected 3-fold increase in effective thermal conductivity and 60% reduction in peak temperature rise.
This study uses computational fluid dynamics software to model heat transfer in a water pipe as the fluid reaches supercritical conditions. The model considers both conductive heat transfer through the pipe walls and convective heat transfer from the fluid flow. Validation is performed against existing literature on supercritical water heat transfer in pipes. The results show that downward flow has the best heat transfer, while upward flow performance deteriorates and recovers over the length of the pipe due to buoyancy effects. Both improvement and deterioration of heat transfer are observed under different conditions.
This document summarizes a numerical study that examines the effects of fin spacing, fin material, and jet velocity on the heat transfer performance of plate fin heat sinks cooled by impinging air jets. The study considers fin spacings of 2mm, 3mm, and 4mm, and fin materials of aluminum, copper, and steel. Jet velocities of 5m/s, 10m/s, and 15m/s are examined. The results show that heat transfer rate increases with decreasing fin spacing, higher thermal conductivity fin materials like copper, and increasing jet velocity. Copper fins achieved the highest heat transfer rates but are heavier and more expensive than aluminum. A fin spacing of 2mm with aluminum fins and a jet velocity of 15
Analytical and Experimental analysis ofthermal characteristics throughTriangu...IJERA Editor
Microscale heat transfer technique is widely intended for best cooling applications in electronic devices as high
heat transfer coefficients are achieved in microscale convection. In present study, analysis of thermal
characteristics has been carried out by analytical calculations along with experimental investigation for a straight
microchannel heat sink of equilateral triangular cross section of 173.21 μm hydraulic diameter with distilled
water as the working fluid. Designed Heater input watts and Reynolds number based on flow rate are varied for
optimized microchannel geometry. Experimental analysis is carried out under constant heat flux condition. The
microchannels are produced on highly accurate micro wire cut EDM. The Reynolds number is varied from 100
to 700. The major intension for this work is to enhance heat transfer coefficient and minimize pressure drop
across microchannel. The Reynolds number, temperature distribution, pressure distribution, heat transfer
coefficient, hydrodynamic entrance length, thermal entrance length, equivalent thermal resistances parameters
are calculated for microchannel heat sink performance analysis. The results of analytical calculations are verified
with experimental investigation. It is found that heat transfer coefficient and pressure drop increases with
increase in Reynolds numbers and decrease in microchannel heat sink hydraulic diameter. Also channel length is
directly proportional to temperature rise
Electrochemical Redox Cycling Realized by Chromatography Paper-based SensorTELKOMNIKA JOURNAL
In this work, we demonstrated that enhancement of electrochemical current due to
redox cycling could be accomplished by paper-based biosensor without any expensive microfabrication
process. The paper-based sensor had layered structure to generate higher current
than a conventional one. We took advantage of the fact that the paper thickness was
micrometer-sized (180um), and it defined the distance between two electrochemical electrodes
on both sides of the paper. Experimental results showed signatures of the redox cycling, where
the electrochemical current from low concentration molecules could be arbitrarily increased by
decreasing the distance between electrodes. Such a structure was advantageous for detecting
target molecules at very low concentration, proposing a low-cost highly-sensitive biochemcal
sensor.
This document summarizes a study analyzing electronic chip microchannels using ANSYS software. It presents the background on microchannel cooling technology and prior research. It then describes the numerical model setup in ANSYS, including the microchannel geometry, governing equations, and boundary/flow conditions. Results are shown for temperature contours, velocity vectors, pressure drops, and heat transfer coefficients for different materials and pressure drops. The study found that outlet water temperature was highest for a pressure drop of 30 kPa and when the substrate was silicon. Overall, the document analyzes heat transfer in a microchannel heat sink using computational fluid dynamics software.
This document discusses numerical simulations of heat transfer in an annulus tube with internal fins. The simulations solve the governing equations for mass, momentum, energy and turbulence using a k-ε model. Various fin configurations are analyzed by varying the number, shape and size of fins. The results show that heat transfer increases with fin number and height. Trapezoidal fins have higher heat transfer than other shapes. The study aims to determine the optimal fin design for maximum thermal performance in the annulus tube.
This document summarizes an experiment to measure the out-of-plane thermal conductivity of flexible substrate materials like polyethylene naphthalate (PEN) and polyethylene teraphthalate (PET). A steady-state method is used where a heat flux is applied through one copper block in contact with the substrate, and the temperature difference across the substrate is measured. Thermal conductivity values are determined from the temperature differences and heat fluxes for substrates of varying thicknesses. The results indicate low thermal conductivity for flexible substrates, which could challenge thermal management in flexible electronics due to limited heat spreading and lack of active cooling options.
This document discusses heat transfer and thermal transport in lithium-ion battery cells. The key points are:
1) Thermal conduction within lithium-ion battery cells is dominated by the thermal contact resistance between the cathode and separator, which accounts for around 88% of the total thermal resistance.
2) Measured values of the thermal contact resistance between the cathode and separator agree with theoretical models that account for weak adhesion between the materials.
3) Chemically bridging the cathode-separator interface using an amine reduces the thermal contact resistance by 4 times without negatively impacting electrochemical performance, resulting in an expected 3-fold increase in effective thermal conductivity and 60% reduction in peak temperature rise.
This study uses computational fluid dynamics software to model heat transfer in a water pipe as the fluid reaches supercritical conditions. The model considers both conductive heat transfer through the pipe walls and convective heat transfer from the fluid flow. Validation is performed against existing literature on supercritical water heat transfer in pipes. The results show that downward flow has the best heat transfer, while upward flow performance deteriorates and recovers over the length of the pipe due to buoyancy effects. Both improvement and deterioration of heat transfer are observed under different conditions.
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.
NUMERICAL STUDIES ON THE LIQUID REQUIREMENTS FOR COMPLETE TRANSIENT CHILLDOWN...IAEME Publication
This document presents a numerical study on the liquid requirements for complete transient chilldown of helically coiled transfer lines. Computational fluid dynamics (CFD) modeling was used to determine the quantity of liquid nitrogen required and time taken for complete chilldown of transfer lines with different helix angles (20°, 25°, 30°). It was found that the mass of fluid used and time taken for complete chilldown reduces as the helix angle increases, due to increased centrifugal forces. Validation of the CFD code was also performed against experimental data from literature.
This document discusses using thermally conductive plastic housings for industrial control electronics like PLCs and power supplies. Finite element modeling and testing of materials from different suppliers found that a prototype material from GEP performed better than other options at dissipating heat. Samples of housings molded from the GEP material showed lower steady-state temperature readings when tested with instrumented I/O modules, verifying its improved thermal conductivity over conventional plastics. Further verification is still needed using a housing designed specifically for the GEP material.
Enhanced thermal conductivity of epoxy matrix composites filled with boron ni...IAEME Publication
This document summarizes research on enhancing the thermal conductivity of epoxy composites by adding boron nitride (BN) microparticles. Epoxy composites containing 0-11.3% BN by volume were prepared and their thermal conductivities were measured experimentally. Numerical simulations using ANSYS found the effective thermal conductivity increased by 27.82% for 11.3% BN and 440% for 30% BN, compared to neat epoxy. The results showed BN particles exhibited a percolation behavior, with a sudden jump in thermal conductivity occurring at 20% BN volume.
A Review on Thermal Aware Optimization of Three Dimensional Integrated Circui...IJMER
This document summarizes techniques for thermal optimization in 3D integrated circuits (3Ds ICs). It discusses heat transfer models, thermal-aware floorplanning algorithms, thermal-aware placement algorithms, and algorithms for through-silicon via (TSV) planning. For floorplanning, algorithms aim to minimize peak temperature, thermal gradients, and weighted sums of area and wirelength. Placement algorithms integrate thermal issues by placing hot cells near heat sinks. TSV planning algorithms consider leakage power, temperature, and timing dependencies to optimize number of vias.
IRJET- Study of Variation in Temperature in Concrete using SensorsIRJET Journal
This document summarizes a study that used sensors to measure the temperature variation in different grades of concrete over 28 days. Thermocoupled wired sensors were embedded in molds containing M33 grade concrete (made with Portland slag cement), M43 grade concrete (made with Portland pozzolana cement), and M53 grade concrete (made with ordinary Portland cement). The sensors recorded the temperature at the middle and top of each mold, as well as the water and atmospheric temperatures, on varying time intervals over 28 days. The results found that the temperature varied between the different concrete grades and cement types used. This information can help identify risks of cracking in large concrete structures so preventative measures can be taken.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
On the equality of electric power fractal dimension and capillary pressure fr...Khalid Al-Khidir
On the equality of electric power fractal dimension and capillary pressure fractal dimension for characterizing shajara reservoirs of the permo carboniferous shajara formation
IRJET- Enhancement of Heat Transfer Effectiveness of Plate-Pin Fin Heat S...IRJET Journal
This document summarizes a study on enhancing the heat transfer effectiveness of plate-pin fin heat sinks. Nineteen different plate-pin fin heat sink models were numerically simulated and analyzed based on factors like heat transfer coefficient, Nusselt number, pressure drop, base plate temperature, fan power, and thermal resistance. The results showed that a plate-pin fin heat sink model with a plate cut thickness of D/3, where D is the pin diameter, performed the best with higher heat transfer coefficient, Nusselt number, and lower base plate temperature, pressure drop, fan power, and thermal resistance compared to other models. A heat sink model with pin fins containing two holes also showed improved performance over solid pin fins.
Natural convection heat transfer inside inclined open cylinderIAEME Publication
This document summarizes an experimental study on natural convection heat transfer inside an inclined open cylinder. The study investigated the effects of inclination angle (0°, 30°, 60°, 90°) and heat flux (70-600 W/m2) on the heat transfer. Empirical correlations were developed relating the average Nusselt number to the Rayleigh number. Results showed that heat transfer, as measured by the local and average Nusselt number, increased with increasing heat flux and inclination angle from horizontal to vertical.
The results show that, with proper selection of physical parameters, significant heat transfer
enhancements and pressure drop reductions can be achieved simultaneously with porous pin fins and
the overall heat transfer performances in porous pin fin channels are much better than those in
traditional solid pin fin channels. The effects of pore density are significant. As PPI increases, the
pressure drops and heat fluxes in porous pin fin channels increase while the overall heat transfer
efficiencies decrease and the maximal overall heat transfer efficiencies are obtained at PPI 20.
Furthermore, the effects of pin fin form are also remarkable. With the same physical parameters, the
overall heat transfer efficiencies in the long elliptic porous pin fin channels are the highest while they
are the lowest in the short elliptic porous pin fin channels
ICWES15 - The Study of two Phase Flow Wall Erosion using a Generalized Comput...Engineers Australia
This document summarizes a study on using computational fluid dynamics (CFD) modeling to analyze two-phase flow and wall erosion in pipes with bends. The study found that bends with a larger radius induced less pressure drop and wall erosion compared to shorter radius bends. Modifying the pipe geometry by adding a spiral insert reduced velocities in the bends, lowering erosion rates by up to 399% and extending the predicted installation life.
This document summarizes a presentation on flow through microchannels. It introduces microchannels as channels less than 1 mm in hydraulic diameter and discusses their history, applications, and areas for further development. The presentation describes modeling single-phase flow through different microchannel designs using ANSYS Fluent software. It validates the models by comparing their thermal resistance values to experimental data from Tuckerman and Pease. The results show temperature, pressure, and viscosity variations along the microchannels' lengths for different flow parameters. The conclusion indicates temperature-dependent properties cause the Reynolds number term to diminish and discusses how flow rate and fins affect thermal resistance.
This document discusses failure analysis of bearing cups in drive shaft assemblies. It aims to find a cost-effective solution to eliminate bearing cup cracking during assembly of universal joints. Various heat treatment processes are considered and carbonitriding is identified as the optimal process. It reduces bearing cup failure and manufacturing costs compared to other options like case hardening. A systematic methodology is applied, including understanding the current problem, analysis using wear testing and FEA, and implementing and confirming the effects of carbonitriding as a corrective measure.
This study aimed to correlate knee height with body height and develop regression equations to estimate body height from knee height measurements in subjects from North India. The study measured the body height and knee height of 1000 healthy subjects aged 18 and older. Knee height was found to be positively correlated with body height. Regression analyses were used to generate equations to estimate body height based on knee height, with separate equations for males and females that also included age as a predictor variable. The equations were intended to provide a more accurate estimation of body height that is less affected by age-related changes.
This document provides a literature review on work stress of employees. It discusses how stress has been defined and the sources and types of stress. It reviews signs and symptoms of stress and strategies for coping with stress such as undertaking a stress audit, using scientific inputs, and spreading messages about stress management. The literature review section summarizes 12 previous research studies on topics like occupational stress among different professions, the relationship between emotional intelligence and occupational stress, and the impact of supportive leadership in moderating job stress and performance. The conclusion emphasizes the importance of managing stress and having a positive attitude and lifestyle to deal with distress and improve organizational well-being.
This document describes a proposed system for an automatic energy meter reading system using an ARM7 microcontroller and GSM technology. The system would automatically send meter readings and load information daily to the electricity provider via SMS. It would also allow the provider to remotely control load disconnection if payment is not made. This would make the meter reading process more efficient and accurate compared to manual readings, while also preventing electricity theft.
This document summarizes a study on the effect of lubrication conditions on surface roughness during facing operations. The study tested different lubrication conditions (dry, semi-dry, wet) using different cutting fluids on three materials (mild steel, aluminum, cast iron) at various cutting speeds. The results showed that lubrication conditions during facing impact the roughness of machined metal surfaces, with optimal cutting fluids providing economic and environmental benefits through improved machining performance.
This document summarizes a study on the effect of weld angles on butt weld joint strength. Specimens were made with V-groove weld geometries at included angles of 450, 500, 550, and 600 degrees. Tensile and fatigue tests were conducted on the specimens. The results showed that tensile strength and fatigue life increased with increasing included angle, with 600 degrees performing best. Tensile strength increased up to 76.64% and fatigue life up to 46.15% for the 600 degree angle compared to 450 degrees. Ultrasonic and magnetic testing found no defects in the welds. Therefore, the 600 degree angle provided better strength performance than the 450 degree commonly used.
This document describes the design and manufacturing of an autonomous cart capable of following a user. The cart uses a Microsoft Kinect sensor to recognize and track users through voice and gesture recognition. An Arduino microcontroller controls the cart's motors to follow the user while avoiding obstacles. Two prototypes were created, with the second using stronger aluminum wheels, an acrylic base, and improved Kinect mounting. The cart aims to autonomously follow a single identified user based on their commands, maintaining distance and navigating obstacles. The document evaluates the cart's stress resistance and ability to meet the objectives of autonomous user following.
This document proposes an improved steganography approach using color-guided channels in digital images. It begins with an introduction to steganography and discusses how it can be used to hide secret data or messages within cover objects like images, video, or audio files. The proposed method embeds data into a color image's RGB channels. It first converts the secret message to a binary bit stream and compresses it using run length encoding. The data is then embedded directly into the LSBs of some channels and indirectly into other channels by encoding counts. This approach aims to improve the visual quality of the stego image and have higher embedding capacity compared to existing methods.
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.
NUMERICAL STUDIES ON THE LIQUID REQUIREMENTS FOR COMPLETE TRANSIENT CHILLDOWN...IAEME Publication
This document presents a numerical study on the liquid requirements for complete transient chilldown of helically coiled transfer lines. Computational fluid dynamics (CFD) modeling was used to determine the quantity of liquid nitrogen required and time taken for complete chilldown of transfer lines with different helix angles (20°, 25°, 30°). It was found that the mass of fluid used and time taken for complete chilldown reduces as the helix angle increases, due to increased centrifugal forces. Validation of the CFD code was also performed against experimental data from literature.
This document discusses using thermally conductive plastic housings for industrial control electronics like PLCs and power supplies. Finite element modeling and testing of materials from different suppliers found that a prototype material from GEP performed better than other options at dissipating heat. Samples of housings molded from the GEP material showed lower steady-state temperature readings when tested with instrumented I/O modules, verifying its improved thermal conductivity over conventional plastics. Further verification is still needed using a housing designed specifically for the GEP material.
Enhanced thermal conductivity of epoxy matrix composites filled with boron ni...IAEME Publication
This document summarizes research on enhancing the thermal conductivity of epoxy composites by adding boron nitride (BN) microparticles. Epoxy composites containing 0-11.3% BN by volume were prepared and their thermal conductivities were measured experimentally. Numerical simulations using ANSYS found the effective thermal conductivity increased by 27.82% for 11.3% BN and 440% for 30% BN, compared to neat epoxy. The results showed BN particles exhibited a percolation behavior, with a sudden jump in thermal conductivity occurring at 20% BN volume.
A Review on Thermal Aware Optimization of Three Dimensional Integrated Circui...IJMER
This document summarizes techniques for thermal optimization in 3D integrated circuits (3Ds ICs). It discusses heat transfer models, thermal-aware floorplanning algorithms, thermal-aware placement algorithms, and algorithms for through-silicon via (TSV) planning. For floorplanning, algorithms aim to minimize peak temperature, thermal gradients, and weighted sums of area and wirelength. Placement algorithms integrate thermal issues by placing hot cells near heat sinks. TSV planning algorithms consider leakage power, temperature, and timing dependencies to optimize number of vias.
IRJET- Study of Variation in Temperature in Concrete using SensorsIRJET Journal
This document summarizes a study that used sensors to measure the temperature variation in different grades of concrete over 28 days. Thermocoupled wired sensors were embedded in molds containing M33 grade concrete (made with Portland slag cement), M43 grade concrete (made with Portland pozzolana cement), and M53 grade concrete (made with ordinary Portland cement). The sensors recorded the temperature at the middle and top of each mold, as well as the water and atmospheric temperatures, on varying time intervals over 28 days. The results found that the temperature varied between the different concrete grades and cement types used. This information can help identify risks of cracking in large concrete structures so preventative measures can be taken.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
On the equality of electric power fractal dimension and capillary pressure fr...Khalid Al-Khidir
On the equality of electric power fractal dimension and capillary pressure fractal dimension for characterizing shajara reservoirs of the permo carboniferous shajara formation
IRJET- Enhancement of Heat Transfer Effectiveness of Plate-Pin Fin Heat S...IRJET Journal
This document summarizes a study on enhancing the heat transfer effectiveness of plate-pin fin heat sinks. Nineteen different plate-pin fin heat sink models were numerically simulated and analyzed based on factors like heat transfer coefficient, Nusselt number, pressure drop, base plate temperature, fan power, and thermal resistance. The results showed that a plate-pin fin heat sink model with a plate cut thickness of D/3, where D is the pin diameter, performed the best with higher heat transfer coefficient, Nusselt number, and lower base plate temperature, pressure drop, fan power, and thermal resistance compared to other models. A heat sink model with pin fins containing two holes also showed improved performance over solid pin fins.
Natural convection heat transfer inside inclined open cylinderIAEME Publication
This document summarizes an experimental study on natural convection heat transfer inside an inclined open cylinder. The study investigated the effects of inclination angle (0°, 30°, 60°, 90°) and heat flux (70-600 W/m2) on the heat transfer. Empirical correlations were developed relating the average Nusselt number to the Rayleigh number. Results showed that heat transfer, as measured by the local and average Nusselt number, increased with increasing heat flux and inclination angle from horizontal to vertical.
The results show that, with proper selection of physical parameters, significant heat transfer
enhancements and pressure drop reductions can be achieved simultaneously with porous pin fins and
the overall heat transfer performances in porous pin fin channels are much better than those in
traditional solid pin fin channels. The effects of pore density are significant. As PPI increases, the
pressure drops and heat fluxes in porous pin fin channels increase while the overall heat transfer
efficiencies decrease and the maximal overall heat transfer efficiencies are obtained at PPI 20.
Furthermore, the effects of pin fin form are also remarkable. With the same physical parameters, the
overall heat transfer efficiencies in the long elliptic porous pin fin channels are the highest while they
are the lowest in the short elliptic porous pin fin channels
ICWES15 - The Study of two Phase Flow Wall Erosion using a Generalized Comput...Engineers Australia
This document summarizes a study on using computational fluid dynamics (CFD) modeling to analyze two-phase flow and wall erosion in pipes with bends. The study found that bends with a larger radius induced less pressure drop and wall erosion compared to shorter radius bends. Modifying the pipe geometry by adding a spiral insert reduced velocities in the bends, lowering erosion rates by up to 399% and extending the predicted installation life.
This document summarizes a presentation on flow through microchannels. It introduces microchannels as channels less than 1 mm in hydraulic diameter and discusses their history, applications, and areas for further development. The presentation describes modeling single-phase flow through different microchannel designs using ANSYS Fluent software. It validates the models by comparing their thermal resistance values to experimental data from Tuckerman and Pease. The results show temperature, pressure, and viscosity variations along the microchannels' lengths for different flow parameters. The conclusion indicates temperature-dependent properties cause the Reynolds number term to diminish and discusses how flow rate and fins affect thermal resistance.
This document discusses failure analysis of bearing cups in drive shaft assemblies. It aims to find a cost-effective solution to eliminate bearing cup cracking during assembly of universal joints. Various heat treatment processes are considered and carbonitriding is identified as the optimal process. It reduces bearing cup failure and manufacturing costs compared to other options like case hardening. A systematic methodology is applied, including understanding the current problem, analysis using wear testing and FEA, and implementing and confirming the effects of carbonitriding as a corrective measure.
This study aimed to correlate knee height with body height and develop regression equations to estimate body height from knee height measurements in subjects from North India. The study measured the body height and knee height of 1000 healthy subjects aged 18 and older. Knee height was found to be positively correlated with body height. Regression analyses were used to generate equations to estimate body height based on knee height, with separate equations for males and females that also included age as a predictor variable. The equations were intended to provide a more accurate estimation of body height that is less affected by age-related changes.
This document provides a literature review on work stress of employees. It discusses how stress has been defined and the sources and types of stress. It reviews signs and symptoms of stress and strategies for coping with stress such as undertaking a stress audit, using scientific inputs, and spreading messages about stress management. The literature review section summarizes 12 previous research studies on topics like occupational stress among different professions, the relationship between emotional intelligence and occupational stress, and the impact of supportive leadership in moderating job stress and performance. The conclusion emphasizes the importance of managing stress and having a positive attitude and lifestyle to deal with distress and improve organizational well-being.
This document describes a proposed system for an automatic energy meter reading system using an ARM7 microcontroller and GSM technology. The system would automatically send meter readings and load information daily to the electricity provider via SMS. It would also allow the provider to remotely control load disconnection if payment is not made. This would make the meter reading process more efficient and accurate compared to manual readings, while also preventing electricity theft.
This document summarizes a study on the effect of lubrication conditions on surface roughness during facing operations. The study tested different lubrication conditions (dry, semi-dry, wet) using different cutting fluids on three materials (mild steel, aluminum, cast iron) at various cutting speeds. The results showed that lubrication conditions during facing impact the roughness of machined metal surfaces, with optimal cutting fluids providing economic and environmental benefits through improved machining performance.
This document summarizes a study on the effect of weld angles on butt weld joint strength. Specimens were made with V-groove weld geometries at included angles of 450, 500, 550, and 600 degrees. Tensile and fatigue tests were conducted on the specimens. The results showed that tensile strength and fatigue life increased with increasing included angle, with 600 degrees performing best. Tensile strength increased up to 76.64% and fatigue life up to 46.15% for the 600 degree angle compared to 450 degrees. Ultrasonic and magnetic testing found no defects in the welds. Therefore, the 600 degree angle provided better strength performance than the 450 degree commonly used.
This document describes the design and manufacturing of an autonomous cart capable of following a user. The cart uses a Microsoft Kinect sensor to recognize and track users through voice and gesture recognition. An Arduino microcontroller controls the cart's motors to follow the user while avoiding obstacles. Two prototypes were created, with the second using stronger aluminum wheels, an acrylic base, and improved Kinect mounting. The cart aims to autonomously follow a single identified user based on their commands, maintaining distance and navigating obstacles. The document evaluates the cart's stress resistance and ability to meet the objectives of autonomous user following.
This document proposes an improved steganography approach using color-guided channels in digital images. It begins with an introduction to steganography and discusses how it can be used to hide secret data or messages within cover objects like images, video, or audio files. The proposed method embeds data into a color image's RGB channels. It first converts the secret message to a binary bit stream and compresses it using run length encoding. The data is then embedded directly into the LSBs of some channels and indirectly into other channels by encoding counts. This approach aims to improve the visual quality of the stego image and have higher embedding capacity compared to existing methods.
This document discusses processing private K-nearest neighbor (KNN) queries over untrusted cloud data. It proposes a framework that uses privacy homomorphism to securely process queries while preserving the privacy of both the data owner and the client submitting queries. The framework divides query processing into node traversal and distance computation steps. It encrypts the data index and uses the cloud to decrypt distances during computation, while preventing any party from accessing the actual query or result distances. The framework allows private querying without revealing sensitive information to the cloud or data owner.
This document describes the establishment of a fibroblast cell line from frozen embryos of Arbor Acre broiler chickens. Key findings include:
1) Fibroblast cells were successfully isolated from fresh and frozen embryos and exhibited typical fibroblast morphology.
2) Cell viability was over 80% after thawing frozen embryos and fibroblasts showed a population doubling time of around 42 hours.
3) Karyotyping showed the cells had a normal diploid chromosome number of 78 for chickens and a high percentage of cells were diploid.
4) Transfection of cells with a fluorescent protein vector showed protein expression and formation of fluorescent colonies over time, indicating the cells could be genetically modified.
This document summarizes several studies on human resource management (HRM) and employee performance in the banking sector in India. It discusses the main challenges faced by banks, including adapting to changing economic conditions and regulations. Several literature reviews are also summarized that examine topics like HRM best practices, leadership styles, job descriptions, quality of worklife, and organizational effectiveness in banks. Case studies are presented on innovative HRM practices at State Bank of India, including performance appraisal, training programs, and organization development initiatives.
The document discusses video streaming and content sharing between Android mobile devices and PCs using a peer-to-peer approach without servers. It presents an application that allows live video captured on a mobile device to be streamed and viewed on a nearby PC in real-time over WiFi. Content like images and text can also be shared between devices. The application has uses for social sharing, cooperative work, and assisting elderly/impaired users. It analyzes related works on mobile video streaming and discusses the system design.
This document analyzes India's import demand for petroleum during a period of liberalization from 1981 to 2006. It estimates import demand functions using cointegration and error correction modeling approaches. The empirical results suggest there is a long-run equilibrium relationship between petroleum imports, import prices, income, wholesale prices, import duties, and foreign exchange reserves. The study aims to determine if liberalization policies in India impacted the country's petroleum import demand function.
Carbon fiber is an important material used to make lightweight and strong composite materials. It has high strength and stiffness but is also very lightweight. Carbon fiber composites are used in applications like aerospace structures, wind turbines, sports equipment, and transportation. The manufacturing process of carbon fiber involves spinning a precursor material like polyacrylonitrile (PAN) or pitch into fibers, then stabilizing and carbonizing the fibers at high temperatures to form carbon crystals within tightly bonded atomic structures. The carbon fibers are also treated and coated to improve adhesion with matrix resins and handleability. The resulting carbon fiber composites have advantages like high strength-to-weight ratio, corrosion resistance, fatigue resistance, and design flexibility.
This document describes the design of a test bench to test the performance of a gearbox. The test bench will allow testing of shift performance, leakage, noise, and shift force in driving and dragging conditions. The test bench design includes a fixture to hold the gearbox, a clamping arrangement, a gear shifting mechanism, and an oil dispensing, extraction and filtration unit. The main components are designed, including motors, shafts, couplings, bearings, timing belts, and the gearbox fixture. The fixture design includes resting blocks, pads and plates to support the gearbox at an angle. A pneumatic clamping cylinder is selected to fix the gearbox. A pneumatic tandem cylinder is used for the gear shifting mechanism
This document discusses the study of nonlinear behavior in vibrating systems. It begins with an abstract that defines vibration and explains why nonlinear models are needed to accurately describe real structures. The document then focuses on optimizing the vibration behavior of an absorber system with two degrees of freedom, a shock absorber, and nonlinear stiffness, subjected to harmonic loads. Both deterministic and stochastic cases are considered to find optimal response envelopes for nonlinear displacements, phases, and forces. Different types of nonlinear vibration isolators are also described, including ultra-low frequency isolators, Euler column isolators, and Gospodnetic-Frisch-Fay beam isolators.
Role of Living and Surface Anatomy in Current Trends of Medical EducationIJARIIE JOURNAL
This document discusses current trends in teaching living and surface anatomy in medical education. It notes that allocated time for anatomy teaching has decreased in medical schools in recent decades. Living and surface anatomy help students develop clinical skills. New teaching methods like body painting, peer physical examination, medical imaging and virtual anatomy software have been implemented to teach living and surface anatomy due to reduced time and advances in technology. The document reviews the history of teaching living anatomy and compares different teaching methods, emphasizing that living and surface anatomy should be an integral part of medical curricula taught through various innovative strategies.
This document discusses environmental biotechnology and traditional Indian approaches to environmental issues. It provides an overview of environmental biotechnology techniques used to treat waste and pollution. It also discusses views from ancient Indian scriptures that emphasize harmony between humans and nature. The document advocates applying insights from Indian philosophy's holistic view of the world to help address modern environmental problems through a balanced approach considering both traditional knowledge and new technologies.
The document discusses using Bayesian inference and Dempster-Shafer theory to establish trust relationships and achieve security in mobile ad hoc networks (MANETs). It proposes combining direct observation using Bayesian inference with indirect observation using Dempster-Shafer theory to calculate trust values for nodes. The approach is tested in simulations using the AODV routing protocol, showing improved packet delivery ratio, throughput, and end-to-end delay compared to existing systems.
This document summarizes a research paper on using k-means clustering to analyze big data. It begins with an introduction to big data and its characteristics. It then discusses related work on big data storage, mining, and analytics. The HACE theorem for defining big data is presented. The k-means clustering algorithm is explained as an efficient method for partitioning big data into groups. The proposed system uses k-means clustering followed by data mining and classification modules. Experimental results on two datasets show that the recursive k-means approach finds clusters closer to the actual number than the iterative approach. In conclusion, clustering is effective for handling big data attributes like heterogeneity and complexity, and k-means distribution helps distribute data into appropriate clusters.
EFFECT OF DIMPLES ON FLOW PERFORMANCE OF ENHANCED SURFACE TUBESIRJET Journal
The document presents a numerical study investigating the effects of dimples on the heat transfer and flow characteristics inside a tube. Computational fluid dynamics simulations are performed for smooth tubes and tubes with inward- and outward-facing dimples at Reynolds numbers of 2500, 5000, and 7500. The simulations analyze the velocity streamlines, temperature distributions, and heat transfer coefficients. Preliminary results show that maximum velocity occurs in the center of all tube types, while temperature is highest near the walls. Tubes with dimples demonstrate enhanced heat transfer compared to smooth tubes. Further analysis of heat transfer and pressure drop characteristics is needed to assess the influence of dimples.
Exploring the Use of Computation Fluid Dynamics to Model a T-Junction for UM ...Doug Kripke
1) This document discusses using computational fluid dynamics (CFD) to model a T-junction where hot and cold fluid flows combine. Specifically, it will compare the realizable and standard k-ε turbulence models in replicating experimental velocity field measurements of water in a T-junction.
2) Extensive previous water experiments on a T-junction characterized the thermal striping phenomenon and measured velocity and temperature distributions. This project will use those experimental conditions and measurements for validation of CFD simulations.
3) Reynolds number calculations confirmed the flows are fully turbulent, validating the use of turbulence models. The CFD model setup and boundary conditions aimed to replicate the previous experimental conditions for validation purposes.
IRJET- Study of Heat Transfer Characteristics for the Flow of Air over a Heat...IRJET Journal
This document summarizes a study that used computational fluid dynamics (CFD) to analyze heat transfer from circular and diamond-shaped tubes. The study found that the diamond shape performed better than the circular shape. Specifically:
1) Temperature distribution results showed higher surface temperatures on the circular tube compared to the diamond tube. Higher Reynolds numbers also reduced surface temperatures for both shapes.
2) Nusselt number, a measure of heat transfer, increased with Reynolds number for both shapes. However, the diamond shape had higher Nusselt numbers, indicating better heat transfer performance compared to the circular shape.
3) Tube shape was found to significantly impact heat transfer characteristics, with the diamond shape offering better heat
Experimental Investigation of Flow Pattern on Rectangular Fin Arrays under Na...IJMER
Abstract: In Natural convection heat transfer with the help of fin arrays, parameter are fin length to height ratio, spacing
and orientation of geometry. In the longitudinally short fin array, where single chimney flow pattern is present hence heat
transfer coefficient is high. In long rectangular fin arrays, air is stagnant at central zone hence it is not so much contributed
in heat dissipation. In present study experimental setup is developed to studying the effect of natural convection over
rectangular fin array. Fin spacing, height and heater input are the parameter study during experimentation. Lampblack
coating is used to black fin surface. Flow patterns of various spacing’s are investigated using smoke flow visualization
techniques.
Keyword: Fin Arrays, Flow Visualization, Flow Pattern, Heat Transfer Coefficient, Natural convection.
Numerical simulations have been undertaken
for the benchmark problem in a Square cavity by using
computational fluid dynamics software. This work aims at
discussing the fundamental numerical and computational
fluid dynamic aspects which can lead to the definition of
the following meshing methods and turbulence models.
The meshes used for the simulation are hexahedral,
hexahedral cell with near wall refinement, tetrahedral
grid, polyhedral, tetrahedral with near wall refinement
and polyhedral mesh with prism layer cells based the near
wall thickness of Y+ less than one. The turbulence models
used for the simulation work are AKN K-Epsilon Low-Re,
Realizable K-Epsilon, Realizable K-Epsilon Two-Layer,
standard K-Epsilon, standard K-Epsilon Low-Re,
Standard K-Epsilon Two-Layer, V2F K-Epsilon,
SST(Menter) K-Omega, and Standard(Wilcox) K-Omega.
From these meshes and turbulence models, we will
conclude the suitable mesh and turbulence for the
recirculation flow by the grid independent test. These
analytical values of results are compared with reference
data which gives an optimization of experimental work.
Unsteady simulation was ran for all the Grid Independent
mesh with the SST k omega model with the time step of
0.01 sec for 40 seconds. The flow nature is studied with
and without the temperature for Reynolds number, 1000
and 10000.
This document presents a numerical investigation of mixed convective flow inside straight and bend pipes. The study examines the effects of inlet Rayleigh number and Reynolds number on velocity and temperature profiles within the pipes. For a straight horizontal pipe, secondary flow develops at higher L/D ratios due to density variations, producing maximum velocity at the bottom. For bend pipes, secondary flow in the horizontal section combines with buoyancy effects in the vertical section. Higher Rayleigh numbers indicate a transition from forced to mixed to free convection. Results show secondary flow weakens and profiles become more uniform at farther downstream positions.
Numerical Investigation of Mixed Convective Flow inside a Straight Pipe and B...iosrjce
The present study deals with a numerical investigation of steady laminar and turbulent mixed
convection heat transfer in a horizontal pipe and bend pipe using air as the working fluid.The thermal boundary
condition chosen is that of uniform temperature at the outer wall. Computations were performed to investigate
the effect of inlet Rayleigh number and Reynolds number in the velocity and temperature profile at inside of the
pipe. The secondary flow is more intense in the upper part of the cross-section. It increases throughout the
cross-section until its intensity reaches a maximum, and then it becomes weak at far downstream. For the
horizontal pipe the value of the L/D ratio becomes more than 10 the secondary flow effects are neutralized and
the velocity profile almost become constant throughout.
This document presents a numerical investigation of mixed convective flow inside straight and bend pipes. The study examines the effects of inlet Rayleigh number and Reynolds number on velocity and temperature profiles within the pipes. For a straight horizontal pipe, secondary flow develops at higher L/D ratios, producing maximum velocity at the bottom of the pipe. As L/D increases beyond 10, secondary flow effects diminish. Higher Rayleigh numbers indicate stronger buoyancy effects on flow and temperature distribution. In a bend pipe, secondary flow and buoyancy-driven effects combine to influence mixed convection patterns.
Thermal and fluid characteristics of three-layer microchannels heat sinksjournal ijrtem
ABSTRACT : A heat sink with three layers of microchannels with different flow arrangements has been studied numerically using CFD fluent software version 15. The different flow arrangements using uniform and divergence channels on thermal characteristics of heat sinks at the same mass flow rate are investigated. The results indicated that, uniform channels with counter-flow 1 arrangement provide the best temperature uniformity and divergence channels with counter flow gives the best heat sink performance.
CFD Analysis of a Double Pipe Heat Exchanger by using Fluid Based Nanomaterialsijtsrd
This document summarizes a study analyzing the heat transfer performance of different nanofluids (Al2O3, CuO, Fe3O4) flowing in a double pipe heat exchanger using computational fluid dynamics (CFD). The study examines the effects of nanofluid volume concentration (0.03%) and mass flow rate (8 Lpm, 10 Lpm) on heat transfer rate, pressure, temperature, and velocity distribution. The results show that Fe3O4 nanofluid provides the highest heat transfer rate at both flow rates compared to Al2O3 and CuO nanofluids. Specifically, at a flow rate of 10 Lpm and 0.03% concentration, Fe3O4 nanofluid achieves the
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
IRJET- Numerical Investigation of Heat Transfer Enhancement in Circular Pipe ...IRJET Journal
1. The document numerically investigates heat transfer enhancement in a circular pipe with various rib geometries, including flat, conical, and right angle ribs.
2. It uses computational fluid dynamics to model water flow through the pipe with Reynolds numbers from 5000 to 60000 and a constant heat flux of 50 W/cm2 applied to the pipe surface.
3. The results show that ribs on the inside of the pipe enhance turbulence in the flow and produce recirculation, disturbing the thermal boundary layer and increasing the rate of heat transfer through the pipe.
Numerical Analysis of Inverted Notched Fin Array Using Natural ConvectionIOSR Journals
Abstract:Geometry and orientation plays an important role in natural convection heat transfer. For
horizontal rectangular fin array a chimney flow pattern is developed due to density difference. This flow
pattern creates a stagnant zone near central bottom region. That portion does not contribute much towards
heat dissipation. This area is removed from fins and they became inverted notched fins. This modified geometry
reduces material cost, material weight without hampering heat transfer rate. Numerical models are prepaid to
investigate heat transfer characteristics in plane fins and inverted notched fins. This investigation is also
extended over different types of notches and their effectiveness comparison. Fin spacing, fin height, fin length,
heater input, percentage of area removed in the form of inverted notch are the parameters under
consideration. This analysis is done numerically using CFD package (Fluent). It is found that the heat transfer
coefficient of inverted notch fin array is 25% to 35% higher as compared with normal fin array. Also we found
that the triangular shape notch gives better result than trapezoidal and rectangular shape notch.
Key words: Inverted Notched Fin, Chimney Flow, Natural Convection, Heat transfer coefficient enhancement
Numerical Analysis of Header Configuration of the Plate-Fin Heat ExchangerIJMER
Numerical analysis of a plate fin heat exchanger accounting for the effect of fluid flow
maldistribution onthe inlet header configuration of the heat exchanger is investigated. In this analysis , it
was found that flow maldistribution has effect on the flow perpendicular to its velocity direction. The peak
velocity occurs in the central zone of the header while the velocityalong the perpendicular direction of the
inlet flow diminishes more and more. By this investigation,the results of the flow maldistribution are
presented for a plate fin heat exchangerwhich is reduced as compare to theexisting configuration of the
plate fin heat exchanger.
Thermal analysis of various duct cross sections using altair hyperworks softwaresushil Choudhary
In this work thermal analysis and comparison of various duct cross sections is done computationally using Altair
Hyperworks Software. Simple Analytical results were obtained for conduction and convection through the ducts
which can be used to build up thermal circuit. The inner surface of all ducts is maintained at constant
temperature and ambient air is at certain temperature that is less than inner surface temperature of pipe. Due to
temperature difference heat will flow from higher temperature to lower temperature. Due to temperature
difference heat will flow from higher temperature to lower temperature. The material of pipe provides
conductive resistance and air provides convective resistance. Hence this is a mix mode of heat transfer. The heat
transfer takes place in one dimension only and properties are considered to be isotropic. The ducts are assumed
to be made of aluminium having known thermal conductivity and density. The surroundings of ducts have
known convective heat transfer coefficient and temperature. The results are obtained on hyperview which are for
heat flux, temperature gradient and grid temperature. The different characteristics can be obtained by varying the
material of the ducts.
Comparative Study of Heat Transfer Enhancement in Rectangular And Interruped ...IJERDJOURNAL
Abstract: To increase the heat transfer rate of heat exchanger through fins in compact regionthe louvered interrupted plate fins has designed for increasing fins surface area. FLUENT and Multi-physics software are used in order to develop a 3-D numerical model for investigation ofinterrupted louvered fins. ILF analyzed by CFD tool, on the basis of geometrical parameters the compact relationship for Nusselt Number exhibits enhancement of thermal performance. Fin-plate weight reduces while surface area increases. Air is taken as the working fluid andThe flow regime is assumed to be turbulence, and the mean velocity is such that the Reynolds numbers of interest are above the critical Reynolds number. This study gives a performance data for a rectangular fin in simple and ILF in a plate-fin heat exchanger. In order to evaluate the performance, bulk temperature and combined span wise average Nusselt number (Nusa) are calculated. The heat transferenhancement is observed with the use of different interruption angles of 300 , 400 and 50
Numerical_Analysis_of_Turbulent_Momentum_and_Heat_Transfer_in_a_Rectangular_H...Nate Werner
- The document analyzes turbulent momentum and heat transfer in a rectangular helical duct using water and freon-12 as working fluids.
- It develops a 3D model of the helical duct geometry based on prior research. Simulations are run using ANSYS Fluent and CFX to analyze flow, temperature, and turbulence fields.
- The results show secondary flows developing with higher velocities near the outer wall. While some aspects agree with prior work, the simulations produce higher velocities and different vortex structures than expected. Thermal development also takes longer than velocity development.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document summarizes a study on improving heat transfer in tubes by using different types of twisted tape inserts. Experiments were conducted to assess heat transfer and pressure drop in a tube fitted with alternating clockwise and counter-clockwise twisted tapes (C-CC tapes) as well as serrated twisted tapes (STT). For C-CC tapes, heat transfer increased with higher twist ratios and lower twist angles. For STT, heat transfer increased with higher serration depth ratios but decreased with higher serration width ratios. Thermal performance factors above unity indicated STT provided advantages over plain tubes or twisted tapes. Correlations for Nusselt number and friction factor were determined for both C-CC and STT.
This document summarizes a study that uses computational fluid dynamics (CFD) to analyze the flow and heat transfer characteristics of different elliptical pin fin heat sink configurations. The study aims to examine the effects of elliptical pin fin design parameters on heat sink performance. CFD simulations are conducted using ANSYS Fluent software to compute the thermal resistance, heat transfer coefficient, and surface Nusselt number of plate fin and elliptical pin fin heat sinks. Results show that the elliptical pin fin heat sink has better heat transfer performance than the plate fin heat sink. Simulation results for thermal resistance and pressure drop are validated against experimental data from previous studies.
This document summarizes the design and standardization of a scissor jack to avoid failures in the field. It presents the objectives of modifying the current jack design to improve reliability and reduce costs. It also describes developing a mathematical model for scissor jack design using inputs like vehicle weight and ground clearance. The design process involves modeling the jack in CATIA and developing equations in MATLAB to size components like the power screw, links, and nuts based on applied loads and stresses. Testing procedures are outlined to validate the jack's performance under different load conditions.
This document reviews techniques for emotion recognition from facial expressions. It begins by outlining the general steps of emotion recognition systems as face detection, feature extraction, and classification. Popular techniques discussed include principal component analysis (PCA), local binary patterns (LBP), active appearance models, and Haar classifiers. PCA and LBP were found to provide higher recognition rates. The paper also reviews the Facial Action Coding System and compares the performance of different techniques based on recognition rate. In conclusion, PCA is identified as having the highest recognition rate and performance for emotion recognition.
- The document describes a proposed zigbee-based electronic menu ordering system using an ARM7 microcontroller.
- The system has two sections - a handheld customer section and a main section. The customer section allows selecting menu items via touchscreen and sends the order wirelessly to the main section using zigbee.
- The main section receives orders from multiple customer sections via zigbee, displays orders on an LCD, and sends the data to a PC for billing purposes. The goal is to develop a low-cost wireless ordering system for small restaurants.
1) This document discusses several research papers related to continuous data acquisition algorithms for smart grids using cloud-based technologies and smart meters.
2) It summarizes papers on cloud-based smart metering systems that use standardized communication between smart meters and servers stored in the cloud to optimize energy consumption. Another paper proposes a data collection algorithm that uses energy maps and clustering to reduce energy consumption and increase network lifetime.
3) A third paper discusses utilities using satellites to remotely collect meter data in real-time for accuracy. A final paper presents an algorithm for smart building power consumption scheduling that uses smart meters and dynamic pricing to incentivize shifting usage to low-cost time periods.
1. The document summarizes T.S. Eliot's 1934 work "After Strange Gods" in which he advocates for cultural and religious homogeneity. He argues societies with multiple cultures will become "adulterate" and that a shared religious background is necessary.
2. Eliot discusses his views on tradition, arguing it should not be associated with fixed dogmas but should evolve over time. However, he is criticized for holding anti-Semitic views and an attitude of cultural superiority.
3. The work analyzes Eliot's commentary on various 20th century writers, assessing whether they conform to his ideas of tradition and orthodoxy. Eliot advocates a centralized control of religion, culture,
This document summarizes an experimental investigation of welding distortion in austenitic stainless steel 316 using TIG welding. Taguchi methods were used to design experiments varying welding current, speed, and groove angle at three levels each. Welding was performed and distortion was measured. ANOVA was conducted to determine the significant parameters affecting distortion. Current was found to have the greatest effect on distortion, followed by groove angle, while speed had less influence. The goal of the study was to optimize welding parameters to minimize distortion using Taguchi methods.
This document discusses various load balancing algorithms that can be applied in cloud computing. It begins with an introduction to cloud computing models including infrastructure as a service (IaaS), platform as a service (PaaS), and software as a service (SaaS). It then discusses the goals of load balancing in cloud computing. The main part of the document describes and provides examples of several load balancing algorithms: Round Robin, Opportunistic Load Balancing, Minimum Completion Time, and Minimum Execution Time. For each algorithm, it explains the basic approach and provides an example to illustrate how it works.
This document describes the design and standardization of a toggle jack. It begins with an abstract that outlines the purpose and components of a toggle jack. It then provides background on toggle jacks and their advantages over other jack designs. The main body of the document details the design process, including formulas and sample calculations for sizing the screw, nut, pins, and links based on design loads. It presents a sample design calculation for a 3kN load using medium carbon steel for the screw and phosphor bronze for the nut. Charts of results show stress values remain below allowable limits. The conclusion indicates alloy steel and phosphor bronze is a suitable material combination that keeps stresses within safe limits compared to other materials.
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Study Of Microchannels With Fins For
Effective Cooling Of Electronic Equipment
With Help Of Cfd
1
Vishal S.Sanap, 2
Dr. S.V. Dingare,
1
Student, M.E. Heat Power , 2
Professor, Dept. of Mech. Engineering
1,2
MAEER'S MIT ,College Of Engineering, Kothrud, Pune
ABSTRACT
This paper includes Numerical study of different microchannel with internal fins to investigate fluid flow and
heat transfer characteristics. Three types of microchannels are studied –square channel with conventional and
cross fins and rectangular channel with conventional fins. Constant heat flux boundary conditions were
assumed on external walls of microchannel along with mass flow inlet and atm pressure outlet condition. Result
of average local nusselt no distribution along the channel length were obtained as function of the fin height
ratio. The analysis was carried out for different fin height and flow parameters in presence of a
hydrodynamically developed, thermally developing laminar flow. The existence of optimum fin height ratio for
each type of microchannel is found out in present study.
Keywords—; Microchannel; Electonic cooling; Heat flux; liquid cooling.
1. INTRODUCTION
In the natural system such as lungs and kidney in the human and other animals it has been observed that the
transport processes become more efficient at microscale level dimensions. The increase in the area/volume ratio
of passage and the change in the relative importance of different forces create new class of transport process that
can lead to significant size reductions in practical devices utilizing this process. Although this benefits are well
known as demonstrated by pioneering work of Tuckerman and Peace (1) significant research in this area started
only after their successful application in high heat flux electronics cooling and microfluidic devices. The
definition of microscale is somewhat flexible depending on dimension at which the transport characteristics are
affected. In general channel dimension of 10-200µm are considered microscale.For improving operation
reliability of electronic products efficient removal of internally generated heat is very important which also
affect design consideration of microelectronic components. As many modern devices are densely packed with
microelectronic circuit. Internal heat generated also increased and heat dissipation requirements have
exponentially increased. So traditional cooling technique like fan cooling has become insufficient and imposes
limits on product design. A significant amount of research has been made for developing some innovative
cooling technique that have potential to deliver high heat flux rates for microelectronic application. The concept
of microchannel can be best practical alternative for meeting the future cooling needs of advanced electronic
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applications. The use of very large scale integrated (VLSI) electronic modern devices where internal heat
generation has dramatically increased microchannel heat sink with passive enhancement devices find
application in portable electronic equipment , miniature fuel cells etc and have become major focal point for
challenging research activities in the field of heat transfer.
2. MODEL FORMULATION AND SOLUTION PROCEDURE :-
(b)
Fig.1.(a) Schematic diagram showing the cross section of square microchannel with conventional internal
fins.(b) Computational domain and the grid pattern
The square channel is 200 μm (W) x 200 μm (H) in crosssection, and 120 mm (L) in length and rectangular
channel is 400 μm (W) x 200 μm (H) in cross-section, and 120 mm (L) in length . The microchannel and all the
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internal fins are considered to be made of aluminium. Channel wall thickness (tw) of 10 um and fin thickness
(tf) of 20μm are used in the study, and are kept constant. Fin height ratios H* from 0 (nofin) to 0.9 were
considered in the modeling
Fig.1(c) Schematic diagram showing the cross section of square microchannel with cross internal fins.
Fig.1.(d) Schematic diagram showing the cross section of rectangular microchannel with conventional internal
fins
The dashed lines shown in Fig. 1(a) are the boundaries of the computational domain, where symmetrical
boundary conditions are considered. The external walls of the channel are subjected to a uniform heat flux
thermal boundary condition. A uniform heat flux of 5×105 W/m2 is applied at the four external walls of the
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channel. Hydrodynamically fully developed laminar flow of water at an inlet temperature of 300 K is assumed
to enter the channel. The flow is assumed to be steady, and undergoes thermal boundary layer development from
the inlet of the channel. The microchannel is sufficiently long, such that both hydrodynamically and thermally
fully developed flow is obtained at the channel outlet. The following boundary conditions are specified: atm
pressure boundary condition at the channel and symmetrical boundary condition at the symmetrical wall. The
symmetrical boundary condition reduces the number of nodes required for the model, and thus reduces the
computational time and iteration for convergence. The symmetrical boundary condition assumes that no
diffusion flux transfer occurs across the symmetry plane, and that the normal gradients of all flow variables are
zero. The Reynolds number is suitably varied within the laminar region (1100—1330) with a constant mass flow
rate of 2.2×10-4 kg/s for square channel and 4.4×10-4 kg/s for rectangular channel for all fin height ratios.
Assuming steady, laminar and incompressible flow conditions together with the specified boundary conditions,
the continuity, Navier-Stokes, and the energy equation were solved using the Finite volume based computational
fluid dynamics solver FLUENT 6.3. The following governing equations were used in the mathematical
modelling.
Fig.1(b) shows the computational domain and the grid pattern. For the sake of completeness, the boundary
conditions corresponding to fig.1(b) are mathematically restated below
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The SIMPLE algorithm was used to solve the pressure velocity coupling. The standard discretization scheme
was used in the modelling following the first order upwind of the momentum and energy discretization. The
convergence criterion that was used to ensure accuracy in the modelling is less than 10-6 for the scaled residues
of mass and momentum flux. The average local Nusselt number and surface heat transfer coefficients were
obtained from the numerical simulation once the convergence criterion was satisfied. The average local Nusselt
number and the convective heat transfer coefficient on the inside walls of the channel are defined using the
following equations.
In above Eqs Tw is the local average wall temperature, Tb is the local bulk fluid temperature. 2.1 Grid
Independence : Grid independence test was conducted on the square unfinned channel to ensure that the
obtained result does not depend on the meshing scheme followed. This involved meshing the same geometry of
a square unfinned channel using three different grid sizes and comparing their results. Uniform hexahedral cells
of 10×10×400 (coarse), 20×20×400 (medium) and 40×40×400 (fine) were considered for the grid independence
study. The local average Nusselts number at the exit for unfinned microchannel was obtained as 4.17, 4.05 and
4.03 respectively. Thus upon refinement from coarse to medium grid, an improvement of 2.87% was obtained
and upon further refinement from medium to fine mesh only 0.49% improvement was obtained. The variation of
average local Nusselts number with distance from the inlet of the channel obtained from the grid independence
test for finless channels is shown in the fig 2. It can be seen from the graph that the variation of the results with
alteration the grid is very negligible. Thus, based on the results obtained from the grid independence study, the
medium grid size was chosen for further work involving numerical computations, taking advantage of the
accuracy of the refinement process, data storage, and computational time.
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3. RESULTS AND DISCUSSION :
3.1. Conventional Unfinned Channel :
The fully developed average local Nusselt numbers for the present study was obtained as 4.05 and from the
literature, this value was found to be 3.676. The computational error in the Nusselts number was thus around
9%, which although not a large deviation, may be justified by the convergence criteria adopted. The present
study adopts a convergence criteria of 10-6 in view of the computational time constraints, whereas from those
adopted by the authors may be still lower.
3.2. Conventional Finned Square Channel : With the channel wall thickness and fin thickness held constant, the
fin height ratio was suitably varied. A constant mass flow rate of 2.2 × 10-4 kg/s was given as the inlet for each
case, while varying the fin height ratio. The external dimensions of the channel were also held a constant for all
cases. Fig 3 shows the average local Nusselt number as a function of distance from the inlet of the channel for
some typical cases considered. A larger average local Nusselt number could be seen at the entrance of the
channel due to the development of the thermal boundary layer with the entrance section as the leading edge of
the channel. Nusselt number converges asymptotically to a fully developed value at the outlet of the channel. At
any particular channel location from the inlet, it can be seen that as the fin height increases, the average local
Nusselt number values also increase. However, for a fin height ratio H* of 0.80, the average local Nusselt
numbers are lower, when compared to the case of a fin height ratio H* of 0.60. This clearly shows that there is
an optimum value that lies between fin height ratios H* from 0.60 to 0.80. Curve fitting technique and
interpolation were used to determine the optimum value of the fin height ratio, H*. The optimum value fin
height ratio H* is found to be 0.67.
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As stated earlier, the fully developed Nusselt number value for an unfinned square microchannel obtained from
the present numerical simulation is found to be 4.05. The Nusselt number for a microchannel having internal
fins and fully developed flow for an optimum fin height ratio H* of 0.675 is found to be 9.15. This clearly
shows that the Nusselt number is about 2.26 times higher for an internally finned microchannel when compared
to an unfinned microchannel, thereby reinforcing the advantage of this passive heat transfer enhancement
technique. Fig 4 shows the variation of average local Nusselt number as a function of the fin height ratio H* for
several cases considered in this study. This graph obviously shows the peak Nusselt number at H*=0.67. For a
given fluid, the thermal development length is a function of the hydraulic diameter, Prandtl number and the
Reynolds number. For the same mass flow rate, in an internally finned channel, the flow reaches fully developed
conditions at a shorter distance from the inlet than an unfinned channel. This is due to the fact that for the same
mass flow rate in both the channels, the finned channel provides a smaller hydraulic diameter. An important
factor that goes into consideration for flow through a microchannel is the pressure drop. Increase in the pressure
drop increases the pumping power needed for the micropump. Fig 5 the plot of pressure drop and the average
local Nusselt number in the microchannel, as a function of the fin height ratio H*. As can be seen from graph,
from the pressure drop point of view, there is no benefit in increasing the fin height ratio beyond the optimum
value.
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3.3 Cross Finned Square Channel :
Cross finned microchannels were introduced with the objective of improving the Nusselt number, owing to the
fact that the wetted perimeter is obviously higher than that of conventional fins. The fins are erected from the
corners and extend diagonally as was shown earlier in fig 1(c). As in the case of conventional finned channels,
channel wall thickness and fin thickness were held constant and the fin height ratio was varied. Fig 3. shows the
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average local Nusselt number as a function of distance from the inlet of the channel. A similar explanation can
be given for a larger value of average local Nusselt number at the entrance section and the asymptotic
convergence of the Nusselt number to a fully developed value, as in the case of conventional finned channels. It
can be seen that as the fin height increases, at any particular channel location from the inlet the average local
Nusselt number values also increase. However, unlike conventional finned channels, the optimum value of fin
height ratio H* is found to be 0.80, corresponding to 0.67 of the latter. Although a higher Nusselt number was
expected for the cross finned channels, the optimum value is lower than that of conventional fins.
Corresponding to the optimum Nusselt number of 9.15 at a fin height ratio of 0.67, the optimum value obtained
here was 8.11 at a fin height ratio of 0.80. The presence of more acute corners than that of the latter and the
corresponding drop in velocities at the corners may be interpreted as the reason for this unexpected lower result.
Fig 6 shows the variation of average local Nusselt number as a function of the fin height ratio H* for several
cases considered in this study. It can be seen that the value of average local Nusselt number first drops with
increase in fin height, due to the stagnant effects of the fluid in the corners. But still higher fin heights tend to
increase this as surface area of heat transfer increases. Explanations for thermal development length and
pressure drop can be adopted from that of conventional channels.
3.4 Rectangular Channels With Aspect Ratio 2 :
The study was extended to rectangular channels, where the horizontal and vertical fin height ratios H1* and
H2* are varied independently. Here too the external dimensions, fin and channel thickness were kept constant
and the fin height ratios were varied individually, keeping the mass flow rate same at 4.4×10-4 kg/s. The aim of
this study was to check whether the optimum fin height, if present could be found out by varying the horizontal
and vertical fin height ratios equally or independently. was varied from 0.3 to 0.9. A total of 56 cases were
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solved excluding that of finless rectangular channel. Fig 7 shows the average local Nusselt number as a function
of distance from the inlet of the channel.
The fully developed average local Nusselt number for unfinned square microchannel was found to be 4.88.
From all the values obtained, the maximum Nusselt number was found to be 10.08 for the case in which
H1*=0.60 and H2*=0.80. It is thus observed that the optimum value cannot be reached by varying the horizontal
and vertical fin height ratios equally. Moreover it is inferred that the effect of varying the fin height ratio of
longer side (here H2*) is better than that of varying the shorter one, which is evident from the higher slope of
the surface near H2* kept constant at 0.9 and H1* varied suitably The Nusselt number thus got improved by
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2.07 times from the finless value by the addition of fins in the optimum way. A table and graph showing the
average local Nusselt number at exit for all the cases solved are also given. It should be noted that all this
improvement in the Nusselt number was obtained at the expense of pressure drop. So it may be stated that the
primary constrain for choosing the fin height of microchannels is the pumping power of the micropump
employed.
3.5. Contours Of Velocity :
The contours of velocity at the exit section for different fin heights are shown in Fig 9. It is interesting to
observe the migratory patterns of the velocity. In an unfinned channel, the region of maximum velocity fluid is
always at the centre of the channel. When internal fins are added to the channel, the region of maximum velocity
is shifted. In the case of four fins, as the fin height increases, the region of maximum velocity moves
progressively, to four separate zones formed due to the presence of the fins. The existence of an optimum fin
height is also very clear from figure. The figures show the development of flow pattern within the microchannel
as the fin height increases. As can be seen from Fig 9, there is a significant change in the flow pattern for fin
height ratios H* =0.4, 0.6,0.8 and 0. 9. For the cases considered in this study, the best flow situation is found to
occur for H* = 0.8. For this case, it can also be seen that there is significant improvement in the corner flow,
which helps to enhance the heat transfer in the microchannel. However for fin height above the optimum eight
ratio H* = 0.9, the flow pattern is not favorable for maximum heat transfer due to the stagnation of the fluid t the
centre of the channel.
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For a deep insight into the phenomenon of the increase in heat transfer coefficient due to the presence of fins,
the fluid velocity distribution is plotted along the diagonal extending from the center of the microchannel to one
of the corners in the exit plane for the case of conventional square finned channels. This is done for H* varying
from 0 to 0.90. For finless channel, the peak velocity occurs at the center of the channel. With the increase in
H*, the velocity at center decreases and new peaks occur at the side quadrants of the channel. For the case of the
channel having the optimum fin height ratio, the peak fluid velocity is found to occur at the centre region of the
channel and at the side quadrants of the channel. A higher fluid velocity near the fins and at the heated section
increases the convective heat transfer in the channel.
Any further increase of the fin height ratio beyond the optimum value alters the flow across the centre of the
channel, and the fin tip would not be effective in contributing to the convective heat transfer process that occurs
within the channel. Similar interpretation can be done in case of cross finned channels also. Instead of diagonal
lines, straight lines are drawn at the exit section. Velocity variation is plotted along its length. It is maximum at
the center of channel and comes down to 0 at the walls. With the introduction of fins diagonally, redistribution
takes place and new peaks are formed. The optimum is the case when all the peaks of fluid velocity are of
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similar magnitude, which happens for H*=0.8. Diagonal line at the exit is drawn again for rectangular channels
where the velocity is plotted and peaks of similar magnitude corresponds to maximum Nusselt number at
H1*=0.60;H2*=0.80 3.6. Comparison With Published Results: In order to validate the modelling scheme, the
unfinned channel results of Ramesh and Chandratilleke [13] were compared with a case of an unfinned channel
modelled in the present study. The fully developed average local Nusselt numbers for both the cases were
compared. For the present study, this value was obtained as 4.05 and from the literature, this value was found to
be 3.676. The computational error in the Nusselts number was thus around 9%, which although not a large
deviation, may be justified by the convergence criteria adopted. The present study adopts a convergence criteria
of 10-6 in view of the computational time constraints, whereas from those adopted by the authors may be still
lower. Moreover, the thermo-physical properties were assumed to be temperature dependent. The scheme
adopted by the authors is unavailable.
4.CONCLUSION :
Based on this numerical study, it was concluded that internal fins in a microchannel have the potential to
provide heat transfer augmentation. The work done by Ramesh and Chandratilleke were validated. For a given
microchannel, there is an optimum fin height that provides the best possible heat transfer and pressure drop
characteristics. The optimum fin height ratio H* for a square microchannel found in this study is 0.67. The
following beneficial features are also realized in a microchannel with internal longitudinal fins as compared to
an unfinned microchannel: shorter length required for the development of the thermal boundary layer, better
flow mixing, steeper velocity gradient at the heated surface, increase in the surface area for heat transfer, and
increase in surface heat transfer coefficient and Nusselt number. Similar studies were conducted on cross finned
channels, and the optimum height ratio was found to be 0.80. The cross fin microchannels which when
compared with the conventional finned microchannels failed to show any improvement of the optimum Nusselt
number as expected. Moreover, the additional pressure drop and manufacturing constrains makes the
conventional channels more efficient. From study of all the cases of rectangular channels it was understood that
the optimum value might not be reached by varying the fin height ratios simultaneously equally. Improvement
of fully developed Nusselt number by almost 2.07 times was obtained by adopting a fin height ratio of
H1*=0.60 by H2*=0.8.
5. FUTURE SCOPE OF WORK :
Future scope may include extending the study to higher aspect ratio microchannels, and developing a general
correlation for optimum fin heights with aspect ratio of the channel considered.
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