Numerical Prediction of Flow and Heat Transfer Past a Circular Tube With Annular Fins

2003 ◽  
Author(s):  
D. Chakraborty ◽  
G. Biswas ◽  
P. K. Panigrahi
Keyword(s):  
Heat Transfer ◽  
Circular Tube ◽  
Flow Characteristics ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Stagnation Line ◽  
Flow And Heat Transfer ◽  
Annular Fin ◽  
Annular Fins

A numerical investigation was carried out to study the flow and heat transfer behavior of a vertical circular tube, which is situated between two annular fins in cross-flow. The flow structure of the limiting streamlines on the surface of the circular tube and the annular fins was analysed. A finite volume method was employed to solve the Navier-Stokes and energy equations. The numerical results pertaining to heat transfer and flow characteristics were compared with the available experimental results. The following salient features were observed in this configuration. A horseshoe vortex system was formed at the junction of the stagnation line of the circular tube and the annular fin. The separation took place at the rear of the tube. The influence of the horseshoe vortices on local heat transfer was substantial. The ratio of the axial gap between two annular fins (L) to the radial protrusion length of the annular fin (LR) was identified as an important parameter. The flow and heat transfer results were presented for different L/LR ratios for a Reynolds number of 1000.

Numerical Investigation of Thermal-Hydraulic Performance of Circular and Non-Circular Tubesin Cross-Flow

2021 ◽  
pp. 102-117
Author(s):  
R. Deeb ◽  
D.V. Sidenkov ◽  
V.I. Salokhin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Circular Tube ◽  
Numerical Study ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Ansys Fluent

A numerical study has been conducted to clarify flow and heat transfer characteristics around circular, cam, and drop-shaped tubes using the software package ANSYS FLUENT. Reynolds number Re based on equivalent circular tube is varied in range of (8.1--19.2)·103. All tube shapes are investigated under similar operating conditions. Local heat transfer, pressure and friction coefficients over a surface of the tubes were presented. Obtained results agree well with those available in the literature. Correlations of the average Nusselt number Nuav and a friction factor f in terms of Reynolds number for the studied tubes were proposed. The results indicated that Nuav increases with increasing Re. In the contrary, f decreases as Re increases. Thermal-hydraulic performance is used to estimate the efficiency of the cam and drop-shaped tubes. Results show that the drop-shaped tube has the best thermal-hydraulic performance, which is about 1.6 and 2.5 times higher than that of the cam-shaped and circular tube, respectively

Mechanism of Novel Streamlined Roughness Element Enhancing the Flow and Heat Transfer Performance From Arrays of Impinging Jets

2020 ◽  
Author(s):  
Zhuang Wu ◽  
Hui-ren Zhu ◽  
Cun-liang Liu ◽  
Lin Li ◽  
Qiang Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Roughness Element ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Local Heat ◽  
Impinging Jets ◽  
Remarkable Effect ◽  
Flow And Heat Transfer

Abstract The numerical investigation of the flow and heat transfer characteristics from arrays of impinging jets with the roughed target surface is presented in this paper. Three novel streamlined roughness elements are proposed: similar round protuberance, similar trapezoidal straight rib, and similar trapezoidal curved rib. The jet Reynolds number ranges from 15000 to 30000, the protuberance height is h/H = 0.36, the rib height is h/H = 0.3, 0.5, and 0.7 respectively. The results show that the protuberance can shorten the nozzle to the stagnation point distance, increasing the heat transfer at the stagnation point by nearly 40%. The rib has a remarkable effect of guiding the flow in span-wise direction and away from the target surface, weakening the cross-flow effect. The straight rib gets a better guidance performance, the curved rib provides a larger surface area. An appropriate increase of rib height can improve local heat transfer, continuing to increase mainly enlarge heat transfer area. The decent aerodynamic shape decreases the flow discharge coefficient by only 2% at the rib height of 0.3H.

Numerical Prediction of Flow and Heat Transfer in a Parallel Plate Channel With Staggered Fins

1987 ◽  
Vol 109 (1) ◽  
pp. 25-30 ◽  
Author(s):  
K. M. Kelkar ◽  
S. V. Patankar
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Periodic Variation ◽  
Local Heat ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Constant Property ◽  
Cross Sectional ◽  
Flow And Heat Transfer ◽  
Order Of Magnitude

Fluid flow and heat transfer in two-dimensional finned passages were analyzed for constant property laminar flow. The passage is formed by two parallel plates to which fins are attached in a staggered fashion. Both the plates are maintained at a constant temperature. Streamwise periodic variation of the cross-sectional area causes the flow and temperature fields to repeat periodically after a certain developing length. Computations were performed for different values of the Reynolds number, the Prandtl number, geometric parameters, and the fin-conductance parameter. The fins were found to cause the flow to deflect significantly and impinge upon the opposite wall so as to increase the heat transfer significantly. However, the associated increase in pressure drop was an order of magnitude higher than the increase in heat transfer. Streamline patterns and local heat transfer results are presented in addition to the overall results.

Experimental Investigation of Local Heat Transfer Distribution on Smooth and Roughened Surfaces Under an Array of Angled Impinging Jets

2001 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Deborah A. Kaminski
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Roughened Surface

Abstract Measurements of the local heat transfer distribution on smooth and roughened surfaces under an array of angled impinging jets are presented. The test rig is designed to simulate impingement with cross-flow in one direction which is a common method for cooling gas turbine components such as the combustion liner. Jet angle is varied between 30, 60, and 90 degrees as measured from the impingement surface, which is either smooth or randomly roughened. Liquid crystal video thermography is used to capture surface temperature data at five different jet Reynolds numbers ranging between 15,000 and 35,000. The effect of jet angle, Reynolds number, gap, and surface roughness on heat transfer efficiency and pressure loss is determined along with the various interactions among these parameters. Peak heat transfer coefficients for the range of Reynolds number from 15,000 to 35,000 are highest for orthogonal jets impinging on roughened surface; peak Nu values for this configuration ranged from 88 to 165 depending on Reynolds number. The ratio of peak to average Nu is lowest for 30-degree jets impinging on roughened surfaces. It is often desirable to minimize this ratio in order to decrease thermal gradients, which could lead to thermal fatigue. High thermal stress can significantly reduce the useful life of engineering components and machinery. Peak heat transfer coefficients decay in the cross-flow direction by close to 24% over a dimensionless length of 20. The decrease of spanwise average Nu in the crossflow direction is lowest for the case of 30-degree jets impinging on a roughened surface where the decrease was less than 3%. The decrease is greatest for 30-degree jet impingement on a smooth surface where the stagnation point Nu decreased by more than 23% for some Reynolds numbers.

scholarly journals Local Heat Transfer and Flow Characteristics in Two-Pass Channels with an Inclined Divider Wall.

2002 ◽  
Vol 68 (669) ◽  
pp. 1523-1530
Author(s):  
Masafumi HIROTA ◽  
Hiroshi NAKAYAMA ◽  
Lei CAI ◽  
Hideomi FUJITA ◽  
Tatsuhito KATOH ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat

Flow and Heat Transfer Past a Sudden Contraction With a Porous Insert Using Linear and Non-Linear Turbulence Models

2004 ◽  
Author(s):  
Marcelo Assato ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Porous Insert ◽  
Macroscopic Models ◽  
Flow And Heat Transfer ◽  
Non Linear ◽  
Abrupt Contraction ◽  
Stream Lines

This work presents a numerical investigation for the turbulent flow and heat transfer in an abrupt contraction channel with a porous material placed in a flow passage. The channel has a contraction rate of 3:2. Results for the hybrid medium were obtained using linear and non-linear k-ε macroscopic models. It was used an inlet Reynolds number of Re = 132000 based on the height of the step. Parameters such as porosity, permeability and thickness of the porous insert were varied in order to analyze their effects on the flow pattern. The results of local heat transfer, friction coefficient and stream lines obtained by the two turbulence models were compared for the cases without and with porous insertion of thickness a/H=0.083, 0.166 and 0.250, where H is the step height. Insert porosity of varied between 0.85 and 0.95 with permeability in the range 10−6–10−2 m2.

Simulation of Flow and Heat Transfer in the MTPV Systems

2013 ◽  
Vol 448-453 ◽  
pp. 3291-3295
Author(s):  
Ge Ping Wu ◽  
Jun Wang ◽  
Ping Lu
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Friction Factor ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Transfer Characteristics ◽  
Pressure Losses ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Different Types

Flow and heat transfer characteristics in the microchannel cooling passages with three different types of the MTPV systems are numerically investigated. Reynolds ranged from 100 to 1000 and hydraulic diameter from 0.4mm to 0.8mm. The steady, laminar flow and heat transfer equations are solved in a finite-volume method. The local heat transfer characteristics, thermal resistance, Nusselt numbers, friction factor and pressure losses of the different types are analyzed. A comparison of the heat transfer coefficient, pressure losses and friction factor of the different microchannels are also presented. The heat transfer performance of the rob bundles microchannel is found to be much better than others. However, the rectangular passage has the lowest thermal resistance than the other types of microchannels.

The Effect of Entrance Configuration on Local Heat-transfer Coefficients in Subsonic Diffusers

1972 ◽  
Vol 94 (4) ◽  
pp. 355-359 ◽  
Author(s):  
E. O. Stoffel ◽  
J. R. Welty
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Two Dimensional ◽  
Transfer Coefficients ◽  
Transfer Rates ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Transfer Equations ◽  
Subsonic Diffuser

The effects of square and reentrant entrances on flow regimes (no “appreciable” separation, large transitory stall, and fully developed two-dimensional stall) and local heat-transfer coefficients were determined with air flowing through a symmetrical, plane-wall, two-dimensional subsonic diffuser with one of the diverging walls heated and maintained isothermal. Flow and heat-transfer studies were made for the following ranges: 2θ = 0 to 45 deg, L/W = 6 to 18, and Rextut = 4 × 104 to 3 × 105. Results indicated that 2θ, L/W, and entrance configuration greatly affected the flow regime and heat transfer. Equations relating Um′ to Ut, Ur to Ut, and equations of the type Nu = C Pr0.6Rex0.8 are presented. For the configurations tested, heat-transfer rates were greater for reentrant than for square entrances.

Convective Heat Transfer Enhancement Due to Intermittency in an Impinging Jet

1993 ◽  
Vol 115 (1) ◽  
pp. 91-98 ◽  
Author(s):  
D. A. Zumbrunnen ◽  
M. Aziz
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Stagnation Line ◽  
High Heat Transfer ◽  
Short Period

An experimental investigation has been performed to study the effect of flow intermittency on convective heat transfer to a planar water jet impinging on a constant heat flux surface. Enhanced heat transfer was achieved by periodically restarting an impinging flow and thereby forcing renewal of the hydrodynamic and thermal boundary layers. Although convective heat transfer was less effective during a short period when flow was interrupted, high heat transfer rates, which immediately follow initial wetting, prevailed above a threshold frequency, and a net enhancement occurred. Experiments with intermittent flows yielded enhancements in convective heat transfer coefficients of nearly a factor of two, and theoretical considerations suggest that higher enhancements can be achieved by increasing the frequency of the intermittency. Enhancements need not result in an increased pressure drop within a flow system, since flow interruptions can be induced beyond a nozzle exit. Experimental results are presented for both the steady and intermittent impinging jets at distances up to seven jet widths from the stagnation line. A theoretical model of the transient boundary layer response is used to reveal parameters that govern the measured enhancements. A useful correlation is also provided of local heat transfer results for steadily impinging jets.

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