Heat Transfer Enhancement by Sinusoidal Motion of a Water-Based Nanofluid

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Omer F. Guler ◽  
Oguz Guven ◽  
Murat K. Aktas
Keyword(s):  
Heat Transfer ◽  
Capillary Tube ◽  
Tube Bundle ◽  
Measured Temperature ◽  
Maximum Displacement ◽  
Maximum Heat ◽  
Transfer Rates ◽  
High Heat Transfer ◽  
Maximum Heat Transfer ◽  
Experimental Apparatus

The oscillatory flows are often utilized in order to augment heat transfer rates in various industrial processes. It is also a well-known fact that nanofluids provide significant enhancement in heat transfer at certain conditions. In this research, heat transfer in an oscillatory pipe flow of both water and water–alumina nanofluid was studied experimentally under low frequency regime laminar flow conditions. The experimental apparatus consists of a capillary tube bundle connecting two reservoirs, which are placed at the top and the bottom ends of the capillary tube bundle. The upper reservoir is filled with the hot fluid while the lower reservoir and the capillary tube bundle are filled with the cold fluid. The oscillatory flow in the tube bundle is driven by the periodic vibrations of a surface mounted on the bottom end of the cold reservoir. The effects of the frequency and the maximum displacement amplitude of the vibrations on thermal convection were quantified based on the measured temperature and acceleration data. It is found that the instantaneous heat transfer rate between de-ionized (DI) water (or the nanofluid)-filled reservoirs is proportional to the exciter displacement. Significantly reduced maximum heat transfer rates and effective thermal diffusivities are obtained for larger capillary tubes. The nanofluid utilized oscillation control heat transport tubes achieve high heat transfer rates. However, heat transfer effectiveness of such systems is relatively lower compared to DI water filled tubes.

Heat Transfer in Separated, Reattached, and Redevelopment Regions Behind a Double Step at Entrance to a Flat Duct

1967 ◽  
Vol 89 (2) ◽  
pp. 163-167 ◽  
Author(s):  
E. G. Filetti ◽  
W. M. Kays
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Duct Flow ◽  
Double Step ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Maximum Heat Transfer ◽  
Flow Cross

Experimental data are presented for local heat transfer rates near the entrance to a flat duct in which there is an abrupt symmetrical enlargement in flow cross section. Two enlargement area ratios are considered, and Reynolds numbers, based on duct hydraulic diameter, varied from 70,000 to 205,000. It is found that such a flow is characterized by a long stall on one side and a short stall on the other. Maximum heat transfer occurs in both cases at the point of reattachment, followed by a decay toward the values for fully developed duct flow. Empirical equations are given for the Nusselt number at the reattachment point, correlated as functions of duct Reynolds number and enlargement ratio.

A Numerical Study of the Natural Convection in CPC Solar Collector Cavities with Tubular Absorbers

1989 ◽  
Vol 111 (1) ◽  
pp. 16-23 ◽  
Author(s):  
T. C. Chew ◽  
A. O. Tay ◽  
N. E. Wijeysundera
Keyword(s):  
Heat Transfer ◽  
Tilt Angle ◽  
Solar Collector ◽  
Numerical Study ◽  
Cover Plate ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Maximum Heat Transfer ◽  
Contour Plots ◽  
Flat Cover

The laminar free convection in a compound parabolic concentrator (CPC) solar collector cavity is numerically simulated using the finite element method. Results are presented for representative CPC collectors with tubular absorbers of concentration ratio 2. The effect of Grashof number, truncation and tilt angle were investigated. Generally, higher rates of heat transfer between the tubular absorber and the flat cover plate of the cavity are associated with larger Grashof numbers and shallower cavities. The maximum heat transfer rates occur when the tilt angle is about 60 deg. Contour plots are obtained for the field variables and these provide an insight into the spatial characteristics of the convective mechanisms within the cavity.

scholarly journals WEDM of Copper for the Fabrication of Large Surface-Area Micro-Channels: A Prerequisite for the High Heat-Transfer Rate

Micromachines ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 173 ◽  
Author(s):  
Naveed Ahmed ◽  
Mohammad Pervez Mughal ◽  
Waqar Shoaib ◽  
Syed Farhan Raza ◽  
Abdulrhman M. Alahmari
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
High Heat ◽  
Critical Feature ◽  
Maximum Heat ◽  
High Heat Transfer ◽  
Maximum Heat Transfer ◽  
Micro Channels

To get the maximum heat transfer in real applications, the surface area of the micro-features (micro-channels) needs to be large as possible. It can be achieved by producing a maximum number of micro-channels per unit area. Since each successive pair of the micro-channels contain an inter-channels fin, therefore the inter-channels fin thickness (IFT) plays a pivotal role in determining the number of micro-channels to be produced in the given area. During machining, the fabrication of deep micro-channels is a challenge. Wire-cut electrical discharge machining (EDM) could be a viable alternative to fabricate deep micro-channels with thin inter-channels fins (higher aspect ratio) resulting in larger surface area. In this research, minimum IFT and the corresponding machining conditions have been sought for producing micro-channels in copper. The other attributes associated with the micro-channels have also been deeply investigated including the inter-channels fin height (IFH), inter-channels fin radius (IFR) and the micro-channels width (MCW). The results reveal that the inter-channels fin is the most critical feature to control during the wire electrical discharge machining (WEDM) of copper. Four types of fin shapes have been experienced, including the fins: broken at the top end, deflected at the top end, curled bend at the top, and straight with no/negligible deflection.

Determination of Optimal Row Spacing for a Staggered Cross-Pin Array in a Turbine Blade Cooling Passage

1998 ◽  
Author(s):  
E. E. Donahoo ◽  
A. K. Kulkarni ◽  
A. D. Belegundu ◽  
C. Camci
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Total Pressure ◽  
Reynolds Numbers ◽  
Steady Increase ◽  
Maximum Heat ◽  
High Heat Transfer ◽  
Maximum Heat Transfer ◽  
Wide Range ◽  
Cooling Passage

Crosspin configurations are of interest in turbine blade design due to the enhanced cooling they provide. In addition, crosspins which extend from the walls of hollow blades provide structural integrity and stiffness to the blade itself. Numerous crosspin shapes and arrangements are possible, but only certain combinations offer high heat transfer capability while maintaining low overall total pressure loss. This study presents results from 2-D numerical simulations of coolant airflow through a turbine blade internal cooling passage. The simulations model viscous flow and heat transfer over circular pins in a staggered arrangement of varying pin spacing. Preliminary analysis over a wide range of Reynolds numbers indicates existence of an optimal spacing for which maximum heat transfer and minimum total pressure drop occurs. Pareto plots, which graphically identify the optimum data points with multiple optimization parameters, were obtained for a range of Reynolds numbers and streamwise soarings in a staggered crosspin arrangement. There is a steady increase in crosspin heat transfer up to a certain number of rows, then a gradual decrease in heat transfer in subsequent rows. Knowledge obtained from such findings can be used to determine the number of crosspins used, as well as the ultimate pin arrangement.

scholarly journals Numerical Investigation of Heat Transfer and Friction Factor Characteristics in a Circular Tube Fitted with V-Cut Twisted Tape Inserts

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Sami D. Salman ◽  
Abdul Amir H. Kadhum ◽  
Mohd S. Takriff ◽  
Abu Bakar Mohamad
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Investigation ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Twisted Tape ◽  
Maximum Heat ◽  
High Heat Transfer ◽  
Maximum Heat Transfer ◽  
Twist Ratio

Numerical investigation of the heat transfer and friction factor characteristics of a circular fitted with V-cut twisted tape (VCT) insert with twist ratio (y=2.93) and different cut depths (w=0.5, 1, and 1.5 cm) were studied for laminar flow using CFD package (FLUENT-6.3.26). The data obtained from plain tube were verified with the literature correlation to ensure the validation of simulation results. Classical twisted tape (CTT) with different twist ratios (y=2.93, 3.91, 4.89) were also studied for comparison. The results show that the enhancement of heat transfer rate induced by the classical and V-cut twisted tape inserts increases with the Reynolds number and decreases with twist ratio. The results also revealed that the V-cut twisted tape with twist ratioy=2.93and cut depthw=0.5 cm offered higher heat transfer rate with significant increases in friction factor than other tapes. In addition the results of V-cut twist tape compared with experimental and simulated data of right-left helical tape inserts (RLT), it is found that the V-cut twist tape offered better thermal contact between the surface and the fluid which ultimately leads to a high heat transfer coefficient. Consequently, 107% of maximum heat transfer was obtained by using this configuration.

Improvement of Thermal Performance of Pin Fin Heat Sink Using Different Types of Perforations: A Study Under Natural Convection

2019 ◽  
Author(s):  
Aashish Kumar ◽  
Manoj Kumar Mondal
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Heat Sink ◽  
Transfer Rate ◽  
Coefficient Of Performance ◽  
Reduced Pressure ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Pin Fin ◽  
Maximum Heat Transfer

Abstract Improvement of thermal management can significantly enhance the coefficient of performance (COP) of the thermoelectric (TE) system which is one of the potential solutions for cooling electronic components. Since heat sinks are an integral part of all the electronic equipment, therefore, great consideration is given towards meticulous selection of heat sink for improving its reliability and performance. Various methods are being studied to improve heat transfer rates of heat sink such as microchannel, liquid cooling, nano-fluids, fin topology optimization, anodization of pins, and changing heat sink materials. Recent studies have demonstrated that perforations in pins increase the heat transfer rate of pin fin heat sink, though, the results are inadequate to infer the best geometry. Further research is hence necessary to establish the best possible combination of geometry, size, and number of perforations. The present work aims to numerically identify a heat sink configuration with maximum heat transfer rate among several configuration possibilities under laminar flow condition using ANSYS Fluent 18.2. The simulation results demonstrate that lateral perforation in fins enable higher heat transfer rate than the unmodified heat sink geometry, due to higher Nusselt number and reduced pressure drop. The parametric study also reveals that heat sink with three elliptical perforations boost heat transfer rates (about 21% higher) when compared to heat sink with solid and other perforated geometries. Furthermore, perforations reduce weight and greater effectiveness, making it more desirable for its wide-scale applications.

Correlating Equations for Laminar Free Convection From Misaligned Horizontal Cylinders in Interacting Flow Fields

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Massimo Corcione ◽  
Claudio Cianfrini ◽  
Emanuele Habib ◽  
Gino Moncada Lo Giudice
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Free Convection ◽  
Computer Code ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Maximum Heat Transfer ◽  
Tilting Angle ◽  
Correlating Equations ◽  
Horizontal Cylinders

Steady laminar free convection in air from a pair of misaligned, parallel horizontal cylinders, i.e., a pair of parallel cylinders with their axes set in a plane inclined with respect to the gravity vector, is studied numerically. A specifically developed computer code based on the SIMPLE-C algorithm is used for the solution of the dimensionless mass, momentum, and energy transfer governing equations. Results are presented for different values of the center-to-center cylinder spacing from 1.4 up to 10 diameters, the tilting angle of the two-cylinder array from 0degto90deg, and the Rayleigh number based on the cylinder diameter in the range between 103 and 107. It is found that the heat transfer rates at both cylinder surfaces may in principle be traced back to the combined contributions of the so-called plume effect and chimney effect, which are the mutual interactions occurring in the vertical and horizontal alignments, respectively. In addition, at any misalignment angle, an optimum spacing between the cylinders for the maximum heat transfer rate, which decreases with increasing the Rayleigh number, does exist. Heat transfer dimensionless correlating equations are proposed for any individual cylinder and for the pair of cylinders as a whole.

scholarly journals Study on Heat Pipe : 1st Report, Maximum Heat Transfer Rates of Capillary Limited Heat Pipe

1978 ◽  
Vol 44 (380) ◽  
pp. 1355-1365
Author(s):  
Shinzo SHIBAYAMA ◽  
Shinichi MOROOKA ◽  
Riichiro KITAGAWA ◽  
Katsumi ISHIKAWA
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Maximum Heat ◽  
Transfer Rates ◽  
Maximum Heat Transfer

Experimental Investigation of Oscillation Controlled Thermal Transport in Water-Based Nanofluids

2016 ◽  
Author(s):  
Oguz Guven ◽  
Murat K. Aktas ◽  
Yildiz Bayazitoglu
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Pipe Flow ◽  
Low Frequency ◽  
Measured Temperature ◽  
Maximum Displacement ◽  
Vibration Displacement ◽  
Experimental Apparatus ◽  
Frequency Regime ◽  
Bottom Side

The oscillatory flows are often in order to augment heat transfer rates in various processes. It is also well known fact that nanofluids provide significant enhancement in heat transfer at certain conditions. In this research, heat transfer in an oscillatory pipe flow of both water and water-alumina nanofluid were studied experimentally under low frequency regime flow conditions. The aim of the conducted research is parametric experimental investigation of the convective heat transfer in the oscillatory pipe flow. Firstly, the nanofluids were prepared and thermophysical properties weare measured. The experimental apparatus consist of a capillary pipe bundle connecting two reservoirs which are placed at the top and bottom side of the capillary pipe bundle. Upper reservoir contains the hot fluid while lower reservoir and capillary pipe bundle filled with cold fluid. The oscillatory flow in the pipe bundle is driven by the periodic vibrations of a surface mounted on the bottom end of the cold reservoir. The effects of the maximum displacement amplitude of the vibrations and volumetric concentration of nanoparticles on heat transfer were evaluated based on the measured temperature and acceleration data. It is found that heat transfer rate increases with increasing vibration displacement in the fluid.

Impingement Cooling Performance in Gas Turbine Airfoils Including Effects of Leading Edge Sharpness

1972 ◽  
Vol 94 (3) ◽  
pp. 219-225 ◽  
Author(s):  
D. E. Metzger ◽  
R. T. Baltzer ◽  
C. W. Jenkins
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Leading Edge ◽  
Maximum Heat ◽  
Turbine Engine ◽  
Transfer Rates ◽  
Maximum Heat Transfer ◽  
Circular Jets ◽  
Edge Sharpness ◽  
Turbine Airfoils

An experimental study of the heat transfer characteristics of impingement into cavities which model the cooled leading edges of gas turbine engine airfoils is presented. The study includes both two-dimensional slot jets and single lines of evenly-spaced circular jets. For broad cylindrical cavities correlations are given for the maximum heat transfer rates attainable with optimum positioning of the jet nozzle with respect to the cooled surface. For elongated narrow cavities heat transfer rates relative to these maximum values are presented for a variety of cavity shapes.

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