Pressure Loss and Heat Transfer Characterization of a Cam-Shaped Cylinder at Different Orientations

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
A. Nouri-Borujerdi ◽  
Arash M. Lavasani
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Angle Of Attack ◽  
Cross Flow ◽  
Equivalent Diameter ◽  
Pressure Drag ◽  
The Mean

Pressure drag coefficient and heat transfer are experimentally investigated around a single noncircular cylinder in cross-flow under angle of attack 0 deg<α<360 deg and Reynolds number 1.5×104<Reeq<4.8×104 based on equivalent diameter of a circular cylinder. The results show that the trend of pressure drag coefficient against the angle of attack has a wavy shape but the wavy trend of the Nusselt number is smoother relative to the drag coefficient behavior. It is found that for l∕Deq=0.4 and over the whole range of the Reynolds number, the pressure drag coefficient has a minimum value of about CD=0.4 at α=30 deg, 180 deg, and 330 deg and a maximum value of about CD=0.9 at α=90 deg and 270 deg. The corresponding value of the mean Nusselt number to that of the equivalent circular tube is 1.05<Nu¯cam∕Nu¯cir<1.08 at α=90 deg and 270 deg as well as 0.87<Nu¯cam∕Nu¯cir<0.92 at α=30 deg and 180 deg.

scholarly journals Effect of angle of attack on heat transfer and hydrodynamic characteristics for staggered drop-shaped tubes bundle in cross-flow

2020 ◽  
pp. 21-36
Author(s):  
Rawad Deeb ◽  
◽  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Power Plants ◽  
Numerical Study ◽  
Angle Of Attack ◽  
Organic Rankine Cycle ◽  
Cross Flow ◽  
Hydrodynamic Characteristics ◽  
Equivalent Diameter

Tube bundles can be used as a separation heat exchanger in the organic Rankine cycle power plants (ORC), while the hot gas passes over the outer surface, and the working substance ORC flows inside the tubes. A numerical study has been conducted to clarify heat transfer and hydrodynamics of a cross-flow heat exchanger with staggered drop-shaped tubes at different flow angles of attack in comparison with circular tubes of the same equivalent diameter. The study was performed for the Reynolds number Re= 1.8  103 ~ 9.4  103, the longitudinal and transverse spacing of the tubes in the bundle are the same and are equal to 37 mm. Four cases of the tube’s arrangement with different angles of attack were investigated: 0, 45, 135, and 180 angles. The article presents a literature review related to the subject of the study. A mathematical and numerical model has been developed to calculate the heat transfer coefficient of the studied staggered drop-shaped tubes bundle using the ANSYS package, taking into account the stress-strain state of the tubes. Correlations of the average Nusselt numbers and the friction coefficient for the considered bundles in terms of the Reynolds number and angle of attack were presented. The results reveal that the thermal–hydraulic performance of the drop-shaped tubes bundle with zero-angle of attack is about 1.6 ~ 1.7 times greater than the circular one.

Heat transfer to pulsating turbulent flow in an abrupt pipe expansion

2003 ◽  
Vol 13 (3) ◽  
pp. 286-308 ◽  
Author(s):  
S.A.M. Said ◽  
M.A. Habib ◽  
M.O. Iqbal
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Turbulent Flow ◽  
Pulsation Frequency ◽  
Pipe Expansion ◽  
Cent Increase ◽  
The Mean ◽  
Mean Time

A numerical investigation aimed at understanding the flow and heat transfer characteristics of pulsating turbulent flow in an abrupt pipe expansion was carried out. The flow patterns are classified by four parameters; the Reynolds number, the Prandtl number, the abrupt expansion ratio and the pulsation frequency. The influence of these parameters on the flow was studied in the range 104<Re<5×104, 0.7<Pr<7.0, 0.2<d/D<0.6 and 5<f<35. It was found that the influence of pulsation on the mean time‐averaged Nusselt number is insignificant (around 10 per cent increase) for fluids having a Prandtl number less than unity. This effect is appreciable (around 30 per cent increase) for fluids having Prandtl number greater than unity. For all pulsation frequencies, the variation in the mean time‐averaged Nusselt number, maximum Nusselt number and its location with Reynolds number and diameter ratio exhibit similar characteristics to steady flows.

Direct Numerical Simulation of Flow and Heat Transfer From a Sphere in a Uniform Cross-Flow

2000 ◽  
Vol 123 (2) ◽  
pp. 347-358 ◽  
Author(s):  
P. Bagchi ◽  
M. Y. Ha ◽  
S. Balachandar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Vortex Shedding ◽  
Axisymmetric Flow ◽  
Three Dimensional ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Temperature Fields ◽  
Flow And Heat Transfer

Direct numerical solution for flow and heat transfer past a sphere in a uniform flow is obtained using an accurate and efficient Fourier-Chebyshev spectral collocation method for Reynolds numbers up to 500. We investigate the flow and temperature fields over a range of Reynolds numbers, showing steady and axisymmetric flow when the Reynolds number is less than 210, steady and nonaxisymmetric flow without vortex shedding when the Reynolds number is between 210 and 270, and unsteady three-dimensional flow with vortex shedding when the Reynolds number is above 270. Results from three-dimensional simulation are compared with the corresponding axisymmetric simulations for Re>210 in order to see the effect of unsteadiness and three-dimensionality on heat transfer past a sphere. The local Nusselt number distribution obtained from the 3D simulation shows big differences in the wake region compared with axisymmetric one, when there exists strong vortex shedding in the wake. But the differences in surface-average Nusselt number between axisymmetric and three-dimensional simulations are small owing to the smaller surface area associated with the base region. The shedding process is observed to be dominantly one-sided and as a result axisymmetry of the surface heat transfer is broken even after a time-average. The one-sided shedding also results in a time-averaged mean lift force on the sphere.

The Influence of Vortex Generators on the Drag and Heat Transfer From a Circular Cylinder Normal to an Airstream

1969 ◽  
Vol 91 (1) ◽  
pp. 91-99 ◽  
Author(s):  
T. R. Johnson ◽  
P. N. Joubert
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Circular Cylinder ◽  
Drag Coefficient ◽  
Angular Position ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Experimental Investigations ◽  
Stagnation Line

Experimental investigations were carried out to examine the effect of vortex generators on drag and heat transfer from a circular cylinder in a crossflow. The cylinder was fitted with two rows of vortex generators which were symmetrically placed on either side of and parallel to the front stagnation line. One configuration of vortex generator was used and the angular position of the rows from the front stagnation line was varied. In the heat transfer runs the vortex generator position remained unvaried. Results are presented to show the variation of drag coefficient with Reynolds number for several angular positions of the generator rows. Results are also presented to show the variation of Nusselt number with Reynolds number both for a cylinder with and without generators. These show that both decreases in drag coefficient and increases in Nusselt number can be obtained when vortex generators are fitted.

Investigation of Heat Transfer and Flow Characteristics in Heat Exchanger With Microscale Channels

2007 ◽  
Author(s):  
Shaokun Xu ◽  
Baoming Chen ◽  
Shui Ji ◽  
Shiqi Zhao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Prandtl Number ◽  
Ethylene Glycol ◽  
Flow Characteristics ◽  
Equivalent Diameter ◽  
Flow Friction ◽  
Glycol Solution

The experimental study of heat transfer and flow characteristics are conducted for water and ethylene-glycol solution flowing in the heat exchanger with rectangular or triangular microscale channels, which have equivalent diameter of 0.55mm, 0.91mm, 1.38mm and 5mm. During experiments, the Reynolds number ranges from 300 to 2500. The experimental results show that: at a fixed Reynolds number, the Nusselt number increases along with increasing equivalent diameter, the Nusselt number for ethylene-glycol solution with larger Prandtl number is greater than that for water, the geometrical configuration of the microscale channels have a significant effect on the heat transfer; the flow friction factors of microscale channels are smaller than that of normal channels, flow characteristics of rectangular channels are evidently better than that of triangular, the flow friction factor decreases with increasing Reynolds number, the experiment also show that the flow friction factor is independent of Prandtl number; The critical Reynolds number at which the flow transiting to turbulent flow is 700∼1200.

Effects of a High Porous Material on Heat Transfer and Flow in a Circular Tube

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Koichi Ichimiya ◽  
Tetsuaki Takeda ◽  
Takuya Uemura ◽  
Tetsuya Norikuni
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Porous Material ◽  
Entropy Generation ◽  
Circular Tube ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Equivalent Diameter

This paper describes the heat transfer and flow characteristics of a heat exchanger tube filled with a high porous material. Fine copper wires (diameter: 0.5 mm) were inserted in a circular tube dominated by thermal conduction and forced convection. The porosity was from 0.98 to 1.0. The working fluid was air. The hydraulic equivalent diameter was cited as the characteristic length in the Nusselt number and the Reynolds number. The Nusselt number and the friction factor were expressed as functions of the Reynolds number and porosity. The thermal performance was evaluated by the ratio of the Nusselt number with and without a high porous material and the entropy generation. It was recognized that the high porous material was effective in low Reynolds numbers and the Reynolds number, which minimized the entropy generation existed.

Heat-Transfer Mechanisms in an In-Line Tube Bundle Subject to a Particulate Cross Flow

1992 ◽  
Vol 206 (5) ◽  
pp. 317-326
Author(s):  
D C Sterritt ◽  
D B Murray
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Tube Bundle ◽  
Cross Flow ◽  
Thermal Capacity ◽  
Solid Particles ◽  
Enhancement Of Heat Transfer ◽  
Tube Arrays ◽  
Loading Ratio

The effect of solid particles in suspension on heat transfer for tubes located within a square tube bundle of pitch-diameter ratio 1.75 has been investigated. Tests conducted at a Reynolds number of 6000 with mean particle diameters of 58 and 127 μm at a mass loading ratio of 0.5 kg particles/kg air indicate that heat transfer is enhanced at all locations by the presence of the particles. However, at a Reynolds number of 12 000 there is a net decrease in the mean Nusselt number at all positions, with the exception of the first row. Assessment of the main mechanisms by which particles modify heat transfer in in-line tube arrays suggests that the enhancement of heat transfer is a consequence of the increased thermal capacity of the suspension, whereas the reduction in Nusselt number is considered to result from a change in the flow structure and turbulence within the array.

scholarly journals Effect of wall proximity in fluid flow and heat transfer from a square prism placed inside a wind tunnel

2007 ◽  
Vol 11 (4) ◽  
pp. 65-78 ◽  
Author(s):  
Dipes Chakrabarty ◽  
Ranajit Brahma
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Drag Coefficient ◽  
Average Nusselt Number ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Height Ratio ◽  
Flow And Heat Transfer ◽  
Square Prism ◽  
Wall Proximity

Experimental investigations in fluid flow and heat transfer have been carried out to study the effect of wall proximity due to flow separation around square prisms. Experiments have been carried out for the Reynolds number 4.9?104, blockage ratios are 0.1, 0.2, 0.3 and 0.4, different height-ratios, and various angles of attack. The static pressure distribution has been measured on all faces of the square prisms. The results have been presented in the form of pressure coefficient, drag coefficient for various height-ratios and blockage ratios. The pressure distribution shows positive values on the front face whereas on the rear face negative values of the pressure coefficient have been observed. The positive pressure coefficient for different height-ratios does not vary too much but the negative values of pressure coefficient are higher for all points on the surface as the bluff body approaches towards the upper wall of the wind tunnel. The drag coefficient decreases with the increase in angle of attack as the height-ratio decreases. The maximum value of drag coefficient has been observed at an angle of attack nearly 50? for square prism at all height-ratios. The heat transfer experiments have been carried out under constant heat flux condition. Heat transfer coefficients are determined from the measured wall temperature and ambient temperature, and presented in the form of Nusselt number. Both local and average Nusselt numbers have been presented for various height-ratios. The variation of local Nusselt number has been shown with non-dimensional distance for different angles of attack and blockage ratios. The variation of average Nusselt number has also been shown with different angles of attack for blockage ratios. The local as well as average Nusselt number decreases as the height-ratio decreases for all non-dimensional distance and angle of attack for square prisms. The average Nusselt number for square prisms of different blockage ratio varies with the angle of attack. But there is no definite angle of attack at different block- age ratio at which the value of average Nusselt number is either maximum or minimum.

Effects of a High Porous Material on Heat Transfer and Flow in a Circular Tube

2007 ◽  
Author(s):  
Koichi Ichimiya ◽  
Tetsuaki Takeda ◽  
Takuya Uemura ◽  
Tetsuya Norikuni
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Porous Material ◽  
Entropy Generation ◽  
Circular Tube ◽  
Copper Wire ◽  
Flow Characteristics ◽  
Working Fluid ◽  
Equivalent Diameter

This paper describes the heat transfer and flow characteristics of a heat exchanger tube filled with a high porous material. Fine copper wire (diamete: 0.5 mm) was inserted in a circular tube dominated by thermal conduction and forced convection. The porosity was from 0.98 to 1.0. Working fluid was air. Hydraulic equivalent diameter was cited as the characteristic length in Nusselt number and Reynolds number. Nusselt number and friction factor were expressed as functions of Reynolds number and porosity. Thermal performance was evaluated by the ratio of Nusselt number with and without a high porous material and the entropy generation. It was recognized that the high porous material was effective in low Reynolds number and the Reynolds number which minimized the entropy generation existed.

scholarly journals Unsteady Heat Transfer from an Equilateral Triangular Cylinder in the Unconfined Flow Regime

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
Amit Dhiman ◽  
Radhe Shyam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Prandtl Number ◽  
Flow Regime ◽  
Cross Flow ◽  
Navier Stokes ◽  
Central Difference ◽  
Simple Method ◽  
Energy Equations

Effects of Reynolds number on the heat transfer characteristics of a long (heated) equilateral triangular cylinder are investigated for the range of conditions Re = 50–150 (in the steps of 10) and Prandtl number = 0.71 (air) in the unconfined unsteady cross-flow regime. In order to simulate the present situation, the computational grid is created by using commercial grid generator GAMBIT and the numerical computations are carried out by using FLUENT (6.3). The SIMPLE method is used to solve continuity, Navier-Stokes and energy equations along with the appropriate boundary conditions. The second order upwind scheme is used to discretize the convective terms, while the central difference scheme is used to discretize the diffusive terms in the governing equations. The present results are in an excellent agreement with the literature values. The temperature isotherms and temporal history of Nusselt number are presented in detail. The local as well as time-averaged Nusselt numbers are calculated. The time-averaged Nusselt number increases with increasing Reynolds number for the fixed value of the Prandtl number. Finally, the present numerical results are used to develop the simple heat transfer correlation for the range of conditions covered here.

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