An Efficient Finite Element Procedure for the Analysis of Cross-Flow Micro Heat Exchangers

2010 ◽  
Author(s):  
C. Nonino ◽  
S. Savino ◽  
S. Del Giudice
Keyword(s):  
Heat Exchangers ◽  
Three Dimensional ◽  
Cross Flow ◽  
Computational Effort ◽  
Velocity Fields ◽  
Hybrid Technique ◽  
Number Of Layers ◽  
Micro Heat Exchanger ◽  
Finite Element Procedure ◽  
Transfer Problems

As an alternative to massive CFD, a hybrid technique, which has the advantage of accounting for all of the three-dimensional features of the flow field, but with a limited computational effort, is used for the solution of conjugate convection-conduction heat transfer problems in cross-flow micro heat exchangers. The key feature of the proposed method is represented by the separate computation of the velocity fields in single microchannels and on the subsequent mapping of such velocity fields onto the three-dimensional grid used to solve the thermal problem. The cross-flow micro heat exchangers considered in the paper consist of a number of layers of rectangular microchannels. A parametric study is carried out on the combined effect on cross-flow micro heat exchanger thermal performances due to the variation of the microchannel cross-section and of the ratio of solid to fluid thermal conductivity.

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.

Numerical Prediction of Enhanced Heat Transfer Using Oval Tubes and Delta Winglets

2002 ◽  
Author(s):  
D. Maurya ◽  
S. Tiwari ◽  
G. Biswas ◽  
V. Eswaran ◽  
A. K. Saha
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Power Plants ◽  
Transport Coefficients ◽  
Three Dimensional ◽  
Cross Flow ◽  
Vortex Generators ◽  
Delta Winglet ◽  
Fin Tube ◽  
Oval Tube

Unsteady three-dimensional laminar flow and heat transfer in a channel with a built-in oval tube and delta winglets have been obtained through the solution of the complete Navier-Stokes and energy equations using a body-fitted grid and a finite-volume method. The geometrical configuration represents an element of a gas-liquid fin-tube cross flow heat exchanger. The air-cooled condensers of the geothermal power plants also use fin-tube heat exchangers. The size of such heat exchangers can be reduced through enhancement in transport coefficients on the air (gas) side, which are usually small compared to the liquid side. In a suggested strategy, oval tubes are used in place of circular tubes, and delta winglet type vortex generators in common-flow-down configuration are mounted on the fin-surface in front of the tubes, while another delta winglet pair in common-flow-up configuration is mounted downstream of the first set of winglets. An evaluation of this augmentation strategy is attempted in this investigation. The investigation was carried out for a winglet angle of attack of 40 degrees to the incoming flow. The structures of the velocity field, and the heat transfer characteristics have been presented. The results indicate that vortex generators in conjunction with the oval tube show definite promise for the improvement of fin-tube heat exchangers.

A Study About Performance Evaluation Criteria of Tube Banks With Various Shapes and Arrangements Using Numerical Simulation

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Amin Jodaei ◽  
Kamiar Zamzamian
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Evaluation Criteria ◽  
Cross Flow ◽  
Transfer Coefficients ◽  
Tube Bank ◽  
Shaped Tube ◽  
Tube Banks

Tube bank heat exchangers are designed to efficiently transfer heat between two fluids. Shapes and arrangements of tubes in heat exchangers have significant effects in heat transfer and pressure drop of fluid. In this study, the three-dimensional (3D) numerical investigation is performed to determine heat transfer coefficients, friction factor, and performance evaluation criteria (PEC) of cam-shaped tube banks in aerodynamic and inverse aerodynamic directions in the cross flow air and compared with those of elliptical tube banks in heat exchanger. The arrangements of tubes are aligned and staggered with longitudinal pitch of 44.88 mm and transverse pitch of 28.05 mm. Reynolds number in the range of 11,500–18,500 was used, and the tube surface temperature was fixed and considered 352 K. Results indicate the superior heat transfer of elliptical tube bank over the cam-shaped tube banks in inverse aerodynamic and aerodynamic directions in both arrangements. Moreover, the PEC of the cam-shaped tube banks with inverse aerodynamic and aerodynamic directions and elliptical tube bank in aligned arrangement are approximately 1.4, 1.1, and 1.6, respectively. The obtained results for staggered arrangements are also 1.5, 1.3, and 1.8, respectively.

Transient Heat Transfer Analysis of a Micro Heat Exchanger

2013 ◽  
Vol 455 ◽  
pp. 330-334 ◽  
Author(s):  
Zhong Qian ◽  
Hai Min Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Heat Exchanger ◽  
Silicon Nitride ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Heat Transfer Analysis ◽  
Transient Heat Transfer ◽  
Micro Heat Exchanger

The research object is a micro heat exchanger (MHT) applied in chip cooling, a three dimensional simulation model is developed to analyze the transient heat transfer of the exchanger according to both exponential and periodic heat fluxes. Based on the computational results of the profiles of temperature and thermal stress, a comparison of performance of heat exchangers made of copper and silicon nitride compound is carried out. The results indicate that the capability of a copper heat exchanger is better than that of a silicon nitride exchanger under low load working condition due to the excellent thermal conductivity of copper. However, with large load fluctuations, the advantage of structure strength of compound makes the exchanger attractive since it has lower thermal stress and could guarantee a long-term stability. The efforts of this paper are referable for further research and development of micro heat exchangers.

Investigation of Interstitial Velocity Field Inside Micro-Porous Media

2010 ◽  
Author(s):  
Debjyoti Sen ◽  
Mona Abdolrazaghi ◽  
David S. Nobes ◽  
Sushanta K. Mitra
Keyword(s):  
Porous Media ◽  
Velocity Field ◽  
Three Dimensional ◽  
Cross Flow ◽  
Flow Cell ◽  
Velocity Fields ◽  
Pore Region ◽  
Flow Recirculation ◽  
Two Component ◽  
Interstitial Velocity

An investigation of interstitial velocity field within a micro porous media is studied using a three component three dimensional (3C3D) μ-PIV system. The porous media is formed by packing of micro glass beads of size 400 μm inside a flow cell. The two component two dimensional (2C2D) velocity fields in micro pore region are obtained near the wall. 3C3D velocity field is obtained by scanning through 100 μm inside the porous media using the scanning μ-PIV system. Cross flow pattern and flow recirculation is observed within the micro pore region.

Integral Transforms for Three-Dimensional Steady Turbulent Dispersion in Rivers and Channels

2005 ◽  
Author(s):  
Felipe P. J. de Barros ◽  
Renato M. Cotta
Keyword(s):  
Turbulent Flows ◽  
Integral Transform ◽  
Three Dimensional ◽  
Integral Transforms ◽  
Computational Effort ◽  
Velocity Fields ◽  
Turbulent Dispersion ◽  
Test Case ◽  
Solution Convergence ◽  
Integral Transform Technique

A three-dimensional steady-state mathematical model is considered for predicting the fate of dissolved contaminants in rivers and channels under turbulent flows. The model allows for variable velocity fields and non-uniform turbulent diffusivities. Making use of the Generalized Integral Transform Technique (GITT), a hybrid numerical-analytical solution is then obtained. The solution convergence behavior is investigated and the criterion for reordering the terms in the infinite series is discussed, with the aim of reducing the computational effort associated with the double eigenfunction expansion. A test case is presented to illustrate the proposed approach.

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