Performance Evaluation of Heat Transfer Enhancement for Offset Strip Fins Used in Plate-Fin Heat Exchangers

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Yujie Yang ◽  
Yanzhong Li ◽  
Biao Si ◽  
Jieyu Zheng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Entropy Generation ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Distribution Factor ◽  
Transfer Enhancement ◽  
Entropy Generation Number ◽  
Fin Thickness

In general, offset strip fin (OSF) used in plate-fin heat exchangers is able to provide a greater heat transfer coefficient than the plain fin with the same cross section, but it will also cause the increase of flow friction and pressure drop owing to the fin offset. A new parameter denoted by Ψ*, called relative entropy generation distribution factor, is proposed in this paper to comprehensively reflect the thermodynamic performance of different passage structures in plate-fin heat exchanger. This parameter physically represents relative changes of entropy generation and irreversibility, which are induced by both heat transfer and friction loss due to the utilization of OSF fins. The high magnitude of Ψ* represents a beneficial contribution of OSF with higher degree of the heat transfer enhancement. The proposed method is more reasonable and comprehensive than either the conventional augmentation entropy generation number, Ns,a, or the entropy generation distribution factor, ψ, to evaluate the heat transfer enhancement for OSF cores subject to various operating conditions. With the proposed method, the relative effects of the geometrical parameters of OSF fins, such as the fin thickness-to-height ratio α, fin density γ, and fin thickness-to-length ratio δ, on the heat transfer enhancement are discussed in detail. The results show that relatively small δ results in a better performance, while the parameter α or γ, which contribute to a higher degree of heat transfer enhancement of OSF fin, should be determined after the selection of the other two geometric parameters.

scholarly journals Performance evaluation of tube-in-tube heat exchangers with heat transfer enhancement in the annulus

2006 ◽  
Vol 10 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Ventsislav Zimparov ◽  
Plamen Penchev ◽  
Joshua Meyer
Keyword(s):  
Heat Transfer ◽  
Performance Evaluation ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Evaluation Criteria ◽  
Relative Reduction ◽  
Geometrical Parameters ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Finned Tubes

Different techniques as angled spiraling tape inserts, a round tube in side a twisted square tube and spiraled tube in side the annulus have been used to enhance heat transfer in the annulus of tube-in-tube heat exchangers. The heat transfer enhancement in the shell can be supplemented by heat transfer augmentation in tubes using twisted tape inserts or micro-finned tubes. The effect of the thermal resistance of the condensing refrigerant could also be taken into consideration. To assess the benefit of using these techniques extended performance evaluation criteria have been implemented at different constraints. The decrease of the entropy generation can be combined with the relative in crease of the heat transfer rate or the relative reduction of the heat transfer area to find out the geometrical parameters of the tubes for optimal thermodynamics performance. The results show that in most of the cases considered, the angled spiraling tube insert technique is the most efficient.

scholarly journals Efficiency Improvement of Miniaturized Heat Exchangers

Fluids ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 25
Author(s):  
Iris Gerken ◽  
Thomas Wetzel ◽  
Jürgen J. Brandner
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Assessment Method ◽  
Flow Path ◽  
Transfer Enhancement ◽  
Pressure Losses ◽  
Pin Fin ◽  
Additional Pressure ◽  
The Impact

Micro heat exchangers have been revealed to be efficient devices for improved heat transfer due to short heat transfer distances and increased surface-to-volume ratios. Further augmentation of the heat transfer behaviour within microstructured devices can be achieved with heat transfer enhancement techniques, and more precisely for this study, with passive enhancement techniques. Pin fin geometries influence the flow path and, therefore, were chosen as the option for further improvement of the heat transfer performance. The augmentation of heat transfer with micro heat exchangers was performed with the consideration of an improved heat transfer behaviour, and with additional pressure losses due to the change of flow path (pin fin geometries). To capture the impact of the heat transfer, as well as the impact of additional pressure losses, an assessment method should be considered. The overall exergy loss method can be applied to micro heat exchangers, and serves as a simple assessment for characterization. Experimental investigations with micro heat exchanger structures were performed to evaluate the assessment method and its importance. The heat transfer enhancement was experimentally investigated with microstructured pin fin geometries to understand the impact on pressure loss behaviour with air.

scholarly journals Diamond-Shaped Extended Fins for Heat Transfer Enhancement in a Double-Pipe Heat Exchanger: An Innovative Design

2021 ◽  
Vol 11 (13) ◽  
pp. 5954
Author(s):  
Muhammad Ishaq ◽  
Amjad Ali ◽  
Muhammad Amjad ◽  
Khalid Saifullah Syed ◽  
Zafar Iqbal
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Adaptive Finite Element Method ◽  
Transfer Enhancement ◽  
Enhanced Heat Transfer ◽  
Frictional Loss ◽  
Special Cases ◽  
Double Pipe ◽  
Pipe Heat

Heat transfer enhancement in heat exchangers results in thermal efficiency and energy saving. In double-pipe heat exchangers (DPHEs), extended or augmented fins in the annulus of the two concentric pipes, i.e., at the outer surface of the inner pipe, are used to extend the surface of contact for enhancing heat transfer. In this article, an innovative diamond-shaped design of extended fins is proposed for DPHEs. This type of fin is considered for the first time in the design of DPHEs. The triangular-shaped and rectangular-shaped fin designs of DPHE, available in the literature, can be recovered as special cases of the proposed design. An h-adaptive finite element method is employed for the solution of the governing equations. The results are computed for various performance measures against the emerging parameters. The results dictate that the optimal configurations of the diamond-shaped fins in the DPHE for an enhanced heat transfer are recommended as follows: If around 4–6, 8–12, or 16–32 fins are to be placed in the DPHE, then the height of the fins should be 20%, 80%, or 100%, respectively, of the annulus width. If frictional loss of heat is also to be considered, then for fin-heights of 20–80% and 100% of the annulus width, the placement of 4 and 8 diamond-shaped fins, respectively, is recommended for an enhanced heat transfer. These recommendations are for the radii ratio (i.e., the ratio of the inner pipe radius to that of the outer pipe) of 0.25. The recommendations are be modified if the radii ratio is altered.

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.

Design and testing of energy-efficient heat exchangers for Newtonian and non-Newtonian fluids – A review

2021 ◽  
pp. 095765092110470
Author(s):  
Jayesh P ◽  
Mukkamala Y ◽  
Bibin John
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Internal Surface ◽  
Surface Modifications ◽  
Newtonian Fluids ◽  
Tube Surface ◽  
Pumping Power ◽  
Transfer Enhancement ◽  
The Impact

Heat transfer enhancement, pumping power and weight minimization in enhanced heat exchangers has long been achieved by deploying tubes with internal surface modifications like microgrooves, ribs, fins, knurls, and dimples with and without tube inserts. This article presents a very extensive review of experimental and computational studies on heat transfer enhancement, which covers convectional and unconventional working fluids under different fluid flow conditions. Compound augmentation with tube surface modifications and inserts has yielded enhancements in the overall heat transfer coefficient of over 116% in the fully developed turbulent flow regime. Exotic fluids like nano-coolants deployed in spiral grooved mircofin tubes yielded 196% enhancement in tube side heat transfer rate for concentrations as low as 0.5% by volume, while the thermal efficiency index measuring the overall enhancement in relation to the pumping power was 75%. However, reviews that address the combined effect of unconventional fluids, surface modifications and tube inserts on the overall thermo-hydraulic performance of annular heat exchangers seem to be limited. Further, nano-coolants aren’t frequently used in the process industry. The goal of this study is to document and evaluate the impact of cost-effective and energy-saving passive enhancement techniques such as tube surface modifications, tube inserts, and annular enhancement techniques on annular heat exchangers used in the process industries with Newtonian and non-Newtonian fluids. This review should be useful to engineers, academics and medical professionals working with non-Newtonian fluids and enhanced heat exchangers.

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