NUMERICAL EVALUATION OF THERMO-HYDRAULIC PERFORMANCE IN FIN-AND-TUBE COMPACT HEAT EXCHANGERS WITH DIFFERENT TUBE CROSS-SECTIONS

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
Ahmadali Gholami ◽  
Mazlan Abdul Wahid ◽  
Hussein A. Mohammed ◽  
A. Saat ◽  
M.F. Mohd Yasin ◽  
...  
Keyword(s):  
Heat Exchangers ◽  
Circular Tube ◽  
Hydraulic Performance ◽  
Flat Tube ◽  
Compact Heat Exchangers ◽  
Average Area ◽  
Flat Tubes ◽  
Goodness Factor ◽  
Circle Tube ◽  
Oval Tube

This study examined numericallythe Thermal-hydrodynamic properties of airflow in the fin-and-tube compact heat exchangers (FTCHEs) with considering different shapes of tubes in lowReynoldsnumbers. The influence of applying flat, oval and circular tube adjustments on the thermal and hydraulic characteristics of air flow were analyzed on the in-line tube arrangements. Establishing standard conditions, the study compared different geometries based on circular tubes of 10.459 mm diameter tubes with 25.4 mm longitudinal pitches and 25.4 mm transverse pitches. The other geometries of tubes were assumed in a stable and constant state preparing the same heat transfer surface area per unit volume as that of the nominal case. The results showed that the FTCHE with flat tubes gives the best area goodness factor (j/f) with in a certainrange of Reynoldsnumbers. In addition, FTCHE with flat tubes shown the best thermo-hydraulic performance and a significant augmentation of up to 10.83% and 35.63% in the average area goodness factor achieved accompanied by a decrease in the average friction factor of 17.02% and 43.41% in the flat tube case compared to the oval and circle tube shapes, respectively. It is concluded that the average area goodness factorfor the oval tube is about 25.04% higher than that of the circular tube, while the average friction factor for the oval tube is about 26.9% lower than that of the circular tube. This means that the flat tube has a better-combined thermal–hydraulic performance than the oval and circle tube.

scholarly journals A Review of Airside Heat Transfer Augmentation with Vortex Generators on Heat Transfer Surface

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2737 ◽  
Author(s):  
Lei Chai ◽  
Savvas Tassou
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Circular Tube ◽  
Vortex Generator ◽  
Heat Transfer Surface ◽  
Vortex Generators ◽  
Flat Tube ◽  
Heat Transfer Augmentation ◽  
Oval Tube

Heat exchanger performance can be improved via the introduction of vortex generators to the airside surface, based on the mechanism that the generated longitudinal vortices can disrupt the boundary layer growth, increase the turbulence intensity and produce secondary fluid flows over the heat transfer surfaces. The key objective of this paper is to provide a critical overview of published works relevant to such heat transfer surfaces. Different types of vortex generator are presented, and key experimental techniques and numerical methodologies are summarized. Flow phenomena associated with vortex generators embedded, attached, punched or mounted on heat transfer surfaces are investigated, and the thermohydraulic performance (heat transfer and pressure drop) of four different heat exchangers (flat plate, finned circular-tube, finned flat-tube and finned oval-tube) with various vortex-generator geometries, is discussed for different operating conditions. Furthermore, the thermohydraulic performance of heat transfer surfaces with recently proposed vortex generators is outlined and suggestions on using vortex generators for airside heat transfer augmentation are presented. In general, the airside heat transfer surface performance can be substantially enhanced by vortex generators, but their impact can also be significantly influenced by many parameters, such as Reynolds number, tube geometry (shape, diameter, pitch, inline/staggered configuration), fin type (plane/wavy/composite, with or without punched holes), and vortex-generator geometry (shape, length, height, pitch, attack angle, aspect ratio, and configuration). The finned flat-tube and finned oval-tube heat exchangers with recently proposed vortex generators usually show better thermohydraulic performance than finned circular tube heat exchangers. Current heat exchanger optimization approaches are usually based on the thermohydraulic performance alone. However, to ensure quick returns on investment, heat exchangers with complex geometries and surface vortex generators, should be optimized using cost-based objective functions that consider the thermohydraulic performance alongside capital cost, running cost of the system as well as safety and compliance with relevant international standards for different applications.

The Air-Side Thermal-Hydraulic Performance of Flat-Tube Heat Exchangers With Louvered, Wavy, and Plain Fins Under Dry and Wet Conditions

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Young-Gil Park ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Hydraulic Performance ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Flat Tube ◽  
Parametric Effects ◽  
Dry And Wet Conditions ◽  
Wet Surface ◽  
Friction Performance

The air-side thermal-hydraulic performance of flat-tube aluminum heat exchangers is studied experimentally for conditions typical to air-conditioning applications, for heat exchangers constructed with serpentine louvered, wavy, and plain fins. Using a closed-loop calorimetric wind tunnel, heat transfer and pressure drop are measured at air face velocities from 0.5 m/s to 2.8 m/s for dry- and wet-surface conditions. Parametric effects related to geometry and operating conditions on heat transfer and friction performance of the heat exchangers are explored. Significant differences in the effect of geometrical parameters are found for dry and wet conditions. For the louver-fin geometry, using a combined database from the present and the previous studies, empirical curve-fits for the Colburn j- and f-factors are developed in terms of a wet-surface multiplier. The wet-surface multiplier correlations fit the present database with rms relative residuals of 21.1% and 24.4% for j and f multipliers, respectively. Alternatively, stand-alone Colburn j and f correlations give rms relative residuals of 22.7% and 29.1%, respectively.

A Correlation for Laminar Hydrodynamic Entry Length Solutions for Circular and Noncircular Ducts

1978 ◽  
Vol 100 (2) ◽  
pp. 177-179 ◽  
Author(s):  
R. K. Shah
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchangers ◽  
Circular Tube ◽  
Parallel Plates ◽  
Entry Length ◽  
Compact Heat Exchangers ◽  
Friction Factors ◽  
Proper Design ◽  
Flow Devices

Laminar hydrodynamic entry length solutions for circular and noncircular ducts are essential in proper design of compact heat exchangers and other heat transfer and fluid flow devices. A closed form equation has been proposed to present these solutions for the circular tube, parallel plates, rectangular, equilateral triangular, and concentric annular ducts. The necessary constants are evaluated and it is shown that the proposed correlation predicts the apparent friction factors within ± 2.4 percent.

Simulation Investigation on Multi-Unit Parallel-Flow Type Condenser with Flat Tubes Distribution

2013 ◽  
Vol 423-426 ◽  
pp. 1910-1913
Author(s):  
Jian Rong Du ◽  
Zu Yi Zheng ◽  
Jun Hua Wan ◽  
Yi De Wang ◽  
Zhong Min Wan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Air Velocity ◽  
Flat Tube ◽  
Tube Arrangement ◽  
First Pass ◽  
Flat Tubes

Three heat exchangers, all of which have 38 tubes in total and 6 passes, with different tube arrangements were simulation investigated in laboratory. The effect of flat tube distribution on heat transfer performance and pressure drop characteristic was simulation investigated. The effect of different air velocity and flow on heat transfer performance and pressure drop characteristic was simulation investigated too. The results show that similar tube distribution has little effect on heat transfer but has great effect on pressure drop. It was found the tube arrangement from first pass to sixth pass is 10,9,6,5,4,4 has the best heat transfer performance and its pressure drop is small. The heat transfer and pressure drop increase with the air velocity and refrigerant flow.

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