scholarly journals Numerical investigation on heat transfer enhancement inside a rectangular microchannel with vortex generator using TiO2, Cuo-water nanofluids

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Arash Behaeen ◽  
Mohammad Nimafar
Keyword(s):  
Heat Transfer ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Transfer Enhancement ◽  
Rectangular Microchannel ◽  
Transfer Rates ◽  
Improve Heat Transfer ◽  
Transfer Properties

One of the innovative ways to improve heat transfer properties of heat exchangers, is using nanofluids instead of traditional fluids. Due to presence of metal and oxides of metal particles in nanofluids structure, they have better potential in different environments and conditions than conventional fluids and having higher thermal conductivity causes improvements in heat transfer properties. In this research flow of two different nanofluids through a rectangular microchannel consisting of different number of longitudinal vortex generators (lvgs), has been investigated. Simulations conducted under laminar flow boundary condition and for different Reynolds numbers from 100 to 250. Considered volumetric concentration in this paper is 1, 1/6 and 2/3 %. Results showed, nanofluids and the LVGs remarkably enhance the heat transfer rates inside the microchannel. havg improved with increasing the nanoparticles volume concentrations and Reynolds number, whereas the opposite trends observed for pressure drop. havg improved for 4 to 12 and 9 to 18% for TiO2 and CuO nanofluids, respectively for different volume concentrations in simple microchannel. For lvg-enhanced microchannel the amount of improvements is about 9-14 and 5-10% for CuO and TiO2, respectively. Also using vortex generators alone improved havg for 15-25% for different number of lvgs.

scholarly journals Compound Heat Transfer Enhancement of Wavy Fin-and-Tube Heat Exchangers through Boundary Layer Restarting and Swirled Flow

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1959 ◽  
Author(s):  
Ali Sadeghianjahromi ◽  
Saeid Kheradmand ◽  
Hossain Nemati ◽  
Jane-Sunn Liaw ◽  
Chi-Chuan Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Exchangers ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Transfer Enhancement ◽  
Flat Portion ◽  
Improve Heat Transfer ◽  
Swirled Flow

This study performs a 3D turbulent flow numerical simulation to improve heat transfer characteristics of wavy finandtube heat exchangers. A compound design encompassing louver, flat, and vortex generator onto wavy fins can significantly enhance the heat transfer performance of wavy fin-and-tube heat exchangers. Replacement of wavy fins around tubes with flat fins is not effective as far as the reduction of thermal resistance is concerned, although an appreciable pressure drop reduction can be achieved. Adding two louvers with a width of 8 mm to the flat portion can reduce thermal resistance up to 6% in comparison with the reference wavy fin. Increasing the louver number and width can further decrease the thermal resistance. Also, it is found that the optimum louver angle is equal to the wavy angle for offering the lowest thermal resistance. Therefore, compound geometry with three louvers, a width of 12 mm, and the louver angle being equal to wavy angle with waffle height to be the same as fin pitch of the reference wavy fin has the most reduction in thermal resistance of 16% for a pumping power of 0.001 W. Adding punching longitudinal vortex generators on this compound geometry can further decrease thermal resistance up to 18%.

An Efficient Approach for Performance Evaluation and Parameter Design of Heat Transfer Enhancing Structure

2010 ◽  
Author(s):  
Wen-Jing Zhou ◽  
Ju-Fang Fan ◽  
Zhi-Geng Wu ◽  
Ya-Ling He ◽  
Wen-Quan Tao
Keyword(s):  
Heat Transfer ◽  
Taguchi Method ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Parameter Design ◽  
Geometrical Parameters ◽  
Heat Transfer Area ◽  
Pumping Power ◽  
Transfer Enhancement

The effects of main geometrical parameters of the longitudinal vortex generator (LVG) called “common flow up” on heat transfer enhancement and pressure loss are numerically investigated. Taguchi method is used to guide the numerical simulations. Based on the results of the Taguchi method, a new fin with the combination of different vortex generators is proposed to substitute the original wavy fin-and-tube surface. The results show that the new fin with LVGs can save 9.08% of pumping power while reaching the same amount of heat transfer rate as the wavy fin at inlet velocity of 2m/s, and it can also save 33% of heat transfer area.

A Comparative Study of Fin-and-Tube Heat Exchangers With Various Fin Patterns

2008 ◽  
Author(s):  
L. H. Tang ◽  
G. N. Xie ◽  
M. Zeng ◽  
M. Lin ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Delta Wing ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Algorithm Optimization ◽  
Different Types ◽  
High Reynolds

Air-side heat transfer and friction characteristics of five kinds of fin-and-tube heat exchangers, with the number of tube rows (N = 12) and the diameter of tubes (Do = 18 mm), have been experimentally investigated. The test samples consist of five types of fin configurations: Crimped spiral fin, plain fin, slit fin, fin with delta-wing longitudinal vortex generators and mixed fin with front 6-row vortex-generator fin and rear 6-row slit fin. The heat transfer and friction factor correlations for different types of heat exchangers are obtained with the Reynolds numbers ranging from 4000 to 10000. It is found that crimped spiral fin provides higher heat transfer and pressure drop than the other four fins. The air-side performance of heat exchangers with crimped spiral fin, plain fin, slit fin, fin with delta-wing longitudinal vortex generators and mixed fin with front 6-row vortex-generator fin / rear 6-row slit fin has been evaluated under four sets of criteria and it is shown that the heat exchanger with mixed fin (front vortex-generator fin and rear slit fin) has better performance than that with fin with delta-wing vortex generators, and the slit fin offers best heat transfer performance at high Reynolds numbers. Based on Genetic Algorithm optimization results it is indicated that the increase of length and decrease of height may enhance the performance of vortex generator fin.

scholarly journals Parametric optimization of a stamped longitudinal vortex generator inside a circular tube of a solar water heater at low Reynolds numbers

2021 ◽  
Vol 3 (8) ◽  
Author(s):  
Felipe A. S. Silva ◽  
Luis Júnior ◽  
José Silva ◽  
Sandilya Kambampati ◽  
Leandro Salviano
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Reynolds Numbers ◽  
Geometric Parameters ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Solar Water Heater ◽  
Water Heater ◽  
Solar Water

AbstractSolar Water Heater (SWH) has low efficiency and the performance of this type of device needs to be improved to provide useful and ecological sources of energy. The passive techniques of augmentation heat transfer are an effective strategy to increase the convective heat transfer coefficient without external equipment. In this way, recent investigations have been done to study the potential applications of different inserts including wire coils, vortex generators, and twisted tapes for several solar thermal applications. However, few researchers have investigated inserts in SWH which is useful in many sectors where the working fluid operates at moderate temperatures. The longitudinal vortex generators (LVG) have been applied to promote heat transfer enhancement with a low/moderate pressure drop penalty. Therefore, the present work investigated optimal geometric parameters of LVG to enhance the heat transfer for a SWH at low Reynolds number and laminar flow, using a 3D periodical numerical simulation based on the Finite Volume Method coupled to the Genetic Algorithm optimization method (NSGA-II). The LVG was stamped over a flat plate inserted inside a smooth tube operating under a typical residential application corresponding to Reynolds numbers of 300, 600, and 900. The geometric parameters of LGV were submitted to the optimization procedure which can find traditional LVG such as rectangular-winglet and delta-winglet or a mix of them. The results showed that the application of LGVs to enhance heat transfer is an effective passive technique. The different optimal shapes of the LVG for all Reynolds numbers evaluated improved more than 50% of heat transfer. The highest augmentation heat transfer of 62% is found for the Reynolds number 900. However, the best thermo-hydraulic efficiency value is found for the Reynolds number of 600 in which the heat transfer intensification represents 55% of the pressure drop penalty.

scholarly journals Heat transfer and entropy generation in a microchannel with longitudinal vortex generators using Nanofluids

2020 ◽  
Author(s):  
Amin Ebrahimi ◽  
Farhad Rikhtegar Nezami ◽  
Amin Sabaghan ◽  
Ehsan Roohi
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Single Phase ◽  
Pure Water ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Working Fluid ◽  
Two Phase ◽  
Rectangular Microchannel ◽  
Important Conclusion

Conjugated heat transfer and hydraulic performance for nanofluid flow in a rectangular microchannel heat sink with LVGs (longitudinal vortex generators) are numerically investigated using at different ranges of Reynolds numbers. Three-dimensional simulations are performed on a microchannel heated by a constant heat flux with a hydraulic diameter of 160 μm and six pairs of LVGs using a single-phase model. Coolants are selected to be nanofluids containing low volume-fractions (0.5%–3.0%) of Al2O3 or CuO nanoparticles with different particle sizes dispersed in pure water. The employed model is validated and compared by published experimental, and single-phase and two-phase numerical data for various geometries and nanoparticle sizes. The results demonstrate that heat transfer is enhanced by 2.29–30.63% and 9.44%–53.06% for water-Al2O3 and water-CuO nanofluids, respectively, in expense of increasing the pressure drop with respect to pure-water by 3.49%–16.85% and 6.5%–17.70%, respectively. We have also observed that the overall efficiency is improved by 2.55%–29.05% and 9.78%–50.64% for water-Al2O3 and water-CuO nanofluids, respectively. The results are also analyzed in terms of entropy generation, leading to the important conclusion that using nanofluids as the working fluid could reduce the irreversibility level in the rectangular microchannel heat sinks with LVGs. No exterma (minimums) is found for total entropy generation for the ranges of parameters studied.

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