Aspects of Flow and Heat Transfer in Louver-Fin Round-Tube Heat Exchangers

2005 ◽  
Author(s):  
Hailing Wu ◽  
Ying Gong ◽  
Xiaobo Zhu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Flow Region ◽  
Recirculation Region ◽  
Round Tube ◽  
Flow And Heat Transfer ◽  
Representative Cell ◽  
Conjugated Heat Transfer ◽  
Good Agreement

Experimental and numerical investigations on flow and heat transfer were conducted for louver-fin round-tube two-row heat exchangers. The airflow velocity ranged from 1 m/s to 3 m/s. A three-dimensional numerical method was developed by modeling representative cell units with fluid-solid conjugated heat transfer. Results of three-dimensional numerical simulations were in good agreement with the experimental data. A stagnant flow region exists behind the round tubes, and results in diminished local convective heat transfer. For two-row heat exchangers operating at Reynolds number, Re<300, the first row dominates the heat transfer rate. With Re increasing, the heat transfer contribution of both rows tends to be more uniform. The flow pattern shows a recirculation region downstream of the heat exchanger at higher Re flows, which may be induced by a vortex-shedding instability from the tube and louver bank.

Numerical Simulation of Laminar Flow and Heat Transfer Over a Blunt Flat Plate in Square Channel

2001 ◽  
Vol 124 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Hideki Yanaoka ◽  
Hiroyuki Yoshikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Flow Region ◽  
Recirculation Region ◽  
Square Channel ◽  
Flow And Heat Transfer ◽  
Side Walls

Three-dimensional simulations of laminar separated and reattached flow and heat transfer over a blunt flat plate in a square channel are presented. Numerical calculations of Navier-Stokes equations and energy equation are carried out using the finite difference method. Results of three-dimensional calculation are compared with two-dimensional ones and effects of the side walls are described. It is clarified from the present results that the reattachment length increases with an increase of Reynolds number and the flow in the recirculation region becomes three-dimensional. The reattachment line is curved by the side wall effects. Two-dimensionality of the flow is reduced as Reynolds number increases. The horseshoe-vortex formed near the side walls has great effects upon the heat transfer in the redeveloping flow region. The separated shear layer around the center of plate becomes unstable with a further increase of Reynolds number and the vortices are periodically shed from the reattachment flow region. Such vortices exhibit a hairpin-like structure and greatly influence the heat transfer.

DNS of Expansion Ratio Effects on Three-Dimensional Unsteady Separated Flow and Heat Transfer Around a Downward Step

2005 ◽  
Author(s):  
Aya Kito ◽  
Kazuaki Sugawara ◽  
Hiroyuki Yoshikawa ◽  
Terukazu Ota
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Three Dimensional ◽  
Side Wall ◽  
Separated Flow ◽  
Flow Region ◽  
Expansion Ratio ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Channel Expansion

The direct numerical simulation methodology was employed to analyze the unsteady features of a three-dimensional separated flow and heat transfer around a downward step in a rectangular channel, and to clarify systematically the channel expansion ratio effects upon them. Numerical calculations were carried out using the finite difference method. The Reynolds number Re based on the mean velocity at inlet and the step height was varied from 300 to 1000. The channel expansion ratio ER is 1.5, 2.0 and 3.0 under a step aspect ratio of 36.0. It is found that the flow is steady upto Re = 500 but becomes sensibly unsteady at Re = 700 for all the three expansion ratios. In the case of ER = 2.0, the separated shear layer is most unstable. In the case of ER = 1.5, the longitudinal vortices formed near the side walls of channel are strongest. Nusselt number reaches its maximum in the reattachment flow region and also in the neighborhood of the side wall, and their locations depend greatly upon ER and Re.

Three-Dimensional Numerical Simulation on the Laminar Flow and Heat Transfer in Four Basic Fins of Plate-Fin Heat Exchangers

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Yinhai Zhu ◽  
Yanzhong Li
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Exchangers ◽  
Flow Direction ◽  
Three Dimensional ◽  
Entry Length ◽  
Flow And Heat Transfer ◽  
F Factor ◽  
The One ◽  
Data Reduction Method

In this paper, four basic fins of the plate-fin heat exchangers, rectangular plain fin, strip offset fin, perforated fin, and wavy fin, are modeled and simulated by taking account of fin thickness, thermal entry effect, and end effect. Three-dimensional numerical simulations on the flow and heat transfer in the four fins are investigated and carried out at laminar flow regime. Validity of the modeling technique is verified by comparing computational results with both corresponding experimental data and three empirical correlations from literatures. Global average Colburn factor (j factor) and friction factor (f factor) and their local 1D streamwise-average distributions along the fins are presented by introducing data reduction method. The heat transfer behaviors in both the developing and developed regions are analyzed by examining variations of the local Nusselt number along the flow direction. It is found that the thermal entry length of the four fins might be expressed in the format of Le=c1 Rec2 Pr Dh, which has the same form as the one in a circular tube.

Fluid Flow and Heat Transfer in a Novel Microchannel Heat Sink Partially Filled With Metal Foam Medium

2014 ◽  
Vol 6 (2) ◽  
Author(s):  
E. Farsad ◽  
S. P. Abbasi ◽  
M. S. Zabihi
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Metal Foam ◽  
Three Dimensional ◽  
Numerical Data ◽  
Flow And Heat Transfer ◽  
Cooling Devices ◽  
Volume Method ◽  
Steady Laminar ◽  
Good Agreement

Performance of microchannel heatsink (MCHS) partially filled with foam is investigated numerically. The open cell copper foams have the porosity and pore density in the ranges of 60–90% and 60–100 PPI (pore per inch), respectively. The three-dimensional steady, laminar flow, and heat transfer governing equations are solved using finite volume method. The performance of microchannel heatsink is evaluated in terms of overall thermal resistance, pressure drop, and heat transfer coefficient and temperature distribution. It is found that the results of the surface temperature profile are in good agreement with numerical data. The results show the microchannel heatsink with insert foam appears to be good candidates as the next generation of cooling devices for high power electronic devices. The thermal resistance for all cases decreases with the decrease in porosity. The uniformity of temperature in this heatsink is enhanced compared the heatsink with no foam. The thermal resistance versus the pumping power is depicted, it is found that 80% is the optimal porosity for the foam at 60 PPI with a minimum thermal resistance 0.346 K/W. The results demonstrate the microchannel heatsink partially filled with foam is capable for removing heat generation 100 watt over an area of 9 × 10−6 m2 with the temperature of heat flux surface up to 59 °C.

scholarly journals The Effect of Geometrical Parameters on Heat Transfer Characteristics of Compact Heat Exchanger with Louvered Fins

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
P. Gunnasegaran ◽  
N. H. Shuaib ◽  
M. F. Abdul Jalal
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Cross Flow ◽  
Geometrical Parameters ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Drop Flow ◽  
Louvered Fins

Compact heat exchangers (CHEs) have been widely used in various applications in thermal fluid systems including automotive thermal management systems. Among the different types of heat exchangers for engine cooling applications, cross-flow CHEs with louvered fins are of special interest because of their higher heat rejection capability with the lower flow resistance. In this study, the effects of geometrical parameters such as louver angle and fin pitch on air flow and heat transfer characteristics on CHEs are numerically investigated. Numerical investigations using five different cases with increased and decreased louver angles (+2°, +4°, −2°, −4°, and uniform angle 20°), with a fixed fin pitch and using three different fin pitches (1.0 mm, 2.0 mm, and 4.0 mm), and with the fixed louver angle are examined. The three-dimensional (3D) governing equations for the fluid flow and heat transfer are solved using a standard finite-volume method (FVM) for the range of Reynolds number between 100 and 1000. The computational model is used to study the variations of pressure drop, flow temperature, and Nusselt number.

THERMAL PERFORMANCE OF SINE WAVE FIN-AND-OVAL TUBE HEAT EXCHANGERS

2013 ◽  
Vol 21 (01) ◽  
pp. 1350008 ◽  
Author(s):  
NAE-HYUN KIM ◽  
KANG-JONG LEE ◽  
JI-CHAO HAN ◽  
BYUNG-NAM CHOI
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Sine Wave ◽  
Heat Transfer Characteristics ◽  
Round Tube ◽  
Flow And Heat Transfer ◽  
Wave Channel ◽  
Oval Tube

Experiments were conducted on sine wave fin-and-tube heat exchangers having oval tubes of 0.6 aspect ratio. Twelve samples having different fin pitches and tube rows were tested. Eight herringbone wave fin-and-tube heat exchangers having round tubes were also tested. For round tube samples, the effect of tube row on j factor is not prominent. For oval tube samples, however, the highest j factor is observed for two row configuration, whereas the lowest one is observed for one row configuration. Possible reasoning is provided considering the flow and heat transfer characteristics of sine wave channel combined with connecting oval tubes. The friction factor decreases as number of tube row increases. Comparison with round tube samples reveals that airside performance of oval fin-and-tube heat exchangers is generally superior except for one-row configuration.

Effect of Cylinder Aspect Ratio and Channel Dimensions on the Fluid Flow and Heat Transfer in Parallel-Plate Channel Heat Exchangers

2002 ◽  
Author(s):  
A. K. Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Heat Exchangers ◽  
Parallel Plate ◽  
Numerical Study ◽  
Three Dimensional ◽  
Channel Height ◽  
Flow And Heat Transfer ◽  
Plate Channel

A comparative numerical study has been carried out to analyze the unsteady three-dimensional flow and heat transfer in a parallel-plate channel heat exchangers with in-line arrays of periodically mounted square cylinders (pins) at various Reynolds number and geometrical configurations. The geometry considered represents the narrow trailing edge region of the blade where pin fins are used to serve both a structural and a heat transfer role. The three-dimensional unsteady Navier-Stokes and energy equations are solved using higher order temporal and spatial discretizations. The simulations have been carried out for a range of Reynolds number based on cylinder width (180–600) and a Prandtl number of 6.99 (corresponding to water). Conjugate heat transfer calculations have been employed to account for the conduction in the solid cylinder and convection in the fluid. The thermal performance factor (TPF) increases significantly when the flow becomes unsteady. The choice of aspect ratio of the cylinders is judged by their relative increase in friction factor and heat transfer at transitional Reynolds number. The TPF is found to increase with the increase in pitch of the cylinders. The increase in channel height enhances the TPF though the heat transfer decreases at higher channel height.

Air Flow and Heat Transfer in Louver-Fin Round-Tube Heat Exchangers

2006 ◽  
Vol 129 (2) ◽  
pp. 200-210 ◽  
Author(s):  
H. L. Wu ◽  
Y. Gong ◽  
X. Zhu
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Air Flow ◽  
Fluid Temperature ◽  
Round Tube ◽  
Flow And Heat Transfer ◽  
Representative Unit Cell

Experimental investigations were conducted to understand the air flow and heat transfer in louver-fin round-tube two-row two-pass cross-counterflow heat exchangers. The Colburn factor j and friction factor f were obtained by using the ε-NTU approach. A three-dimensional computational fluid dynamics model was developed based on a representative unit cell with periodical and symmetric boundary conditions. Analysis of tube-side circuiting effect has been conducted and showed improvement by applying overall nonlinear tube-side fluid temperature boundary conditions. Comparison of heat transfer rate of the first and second rows showed that the first row was much more effective, achieving 68-53% of the total heat transfer rate, when air velocity changes from 1.02m∕sto2.54m∕s. A dimensionless parameter, F, was introduced to describe the louver interaction for different fin designs with various louver angles. Using j′∕f1∕3 as a criterion to evaluate the heat transfer and pressure loss performance, an optimal F was predicted around 0.62.

Numerical Simulation and Experimental Validation of Flow and Heat Transfer in Flat-Tube Heat Exchangers

2007 ◽  
Author(s):  
Jiuyang Yu ◽  
Wenwu Xia ◽  
Xingkui Feng
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Flat Tube ◽  
Flow Energy ◽  
Flow Parameters ◽  
Flow And Heat Transfer ◽  
Measured Flow

A three dimensional numerical simulation study has been carried out to predict air flow and temperature distribution in flat-tube heat exchangers. Due to the symmetry in geometrical construction, a section of heat exchanger has been considered for CFD analysis by using PHOENICS software. The k-ε turbulence model has been used to solve the transport equations for turbulent flow energy and the dissipation rate. In order to check the validity of the computational modeling, the results were compared with the measured flow parameters such as pressure and velocity distribution. It is found that both the heat transfer coefficient and the pressure drop for the shell-side are in good arrangement with experimental results. Comparing with circular-tube heat exchangers, the simulation result shows that the pressure drop of flat-tube heat exchangers decreases 12%∼20%, and the coefficient of integral performance Nu/ζ0.29 has an increment, which is between 22%∼34%.

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