Thermo-hydraulic performance evaluation of heat exchanger tube with vortex generator inserts

This work is undertaken as a scientific experiment to test a new design of a turbulent generator. The current research experiments the influence of novel vortex generator (VG )inserts on heat transfers within a tube under a uniform heat flux. A copper tube with a 45 mm inner diameter and 1,350 mm length is used along with a solid disc injector (swirl generator) that comprises ten crescent holes with equal circumferential distribution angles around the disk canter. Subsequently, a swirl flow is generated by deviating the stream flow 45 degrees causing it to spin in the direction of the axial flow. Flow directors are on 45? angles toward the axial direction for each of the crescent holes. This study is an example of flow degradation. Reynolds numbers (Re). range from 6000 to 13500. Therefore, fluid flow is treated as a turbulent system. All experiments done with air are regarded as a power fluid; the Prandtl number is fixed at about 0.71. Thermo-hydraulic performance of heat exchanger is analyzed. The average heat transfer Nusselt number is calculated and discussed. The experiment found out that Nusselt number (Nu) increases with an increase in Re. as well as the number of swirl generators. At four vortex generators (VGs), the maximum augmentation in heat transfer is around 4.3 times greater than the plain tube and friction factor is about 1.28 with 5 VG insets. The results indicate a promising heat exchanger enhancement in the local petroleum industries.

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THE EFFECT OF VORTEX GENERATOR BASE LENGTH ON THERMAL HYDRAULIC PERFORMANCE ACROSS FIN-AND-TUBE HEAT EXCHANGER

Jurnal Teknologi ◽

10.11113/jt.v79.11897 ◽

2017 ◽

Vol 79 (7-3) ◽

Author(s):

Mohd Fahmi Md Salleh ◽

Mazlan Abdul Wahid ◽

Seyed Alireza Ghazanfari

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Pressure Drop ◽

Heat Transfer Enhancement ◽

Vortex Generator ◽

Hydraulic Performance ◽

Base Length ◽

Transfer Enhancement ◽

Tube Heat Exchanger ◽

Baseline Case

Heat transfer enhancement is believed can be achieved by using vortex generator. In the past decades, many researches have been performed to investigate the effect of various vortex generator geometry and parameters including vortex generator angle of attack and height. However, less study has been conducted to investigate the influence of vortex generator length at different arrangement towards the heat transfer performance across the fin-and-tube heat exchanger (FTHE). Therefore, the effects of different strategy on the rectangular winglet vortex generator (RWVG) base length towards the thermal hydraulic performance across the FTHE were numerically investigated in this study. Two types of RWVG arrangement known as common flow down (CFD) or common flow up (CFU) arrangement were used and placed behind four rows of tube in inline arrangement. Total of 7 cases were investigated including the default RWVG, extended front and extended back for both RWVG in CFD and CFU arrangement together with FTHE without vortex generator which was set as the baseline case. The Reynolds number ranged from 500 to 900. It was found that the size of the wake region behind the RWVG contributed to the additional pressure drop penalty across the FTHE. Meanwhile, different thermal characteristics were found for different base length strategy in CFD and CFU arrangement. For RWVG arranged in CFD and CFU arrangement, the extended back case shows the highest heat transfer enhancement with 5 – 25 % and 5 – 15 % increment compared to the baseline case respectively. Based on JF factor evaluation, default RWVG in CFU arrangement provide better heat transfer enhancement than the pressure drop penalty compared to other RWVG cases with average JF factor value is 0.8. Nonetheless, none of the tested cases shows higher JF factor value than the baseline case.

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The Effect of Axial Flow on Heat Transfer in Decaying, Swirling Flow in a Pipe

Heat Transfer: Volume 1 ◽

10.1115/ht2003-47177 ◽

2003 ◽

Author(s):

Heather L. McClusky ◽

Donald E. Beasley

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Swirling Flow ◽

Axial Flow ◽

Number Range ◽

Tangential Flow ◽

Nusselt Numbers ◽

Swirl Generator ◽

Inlet Conditions

Local Nusselt numbers were experimentally measured in decaying, swirling flow in a pipe. Using a tangential injection mechanism, the two inlet conditions examined in this study were tangential flow and superimposed tangential and axial flow. Local Nusselt numbers at the pipe inlet were greater for tangential flow than for superimposed tangential and axial flow at the same Reynolds number. Local Nusselt numbers increased as the amount of fluid injected tangentially was increased for the superimposed case. For both inlet conditions employed with the present swirl generator, the local Nusselt number approached the fully-developed value in the far field. At the exit of the pipe, L/D = 62.8, local Nusselt numbers were greater than the fully-developed Nusselt number; therefore, heat transfer enhancement was still present at the exit of the pipe. The effect of axial flow on the local Nusselt numbers is explored in this investigation for air and over a Reynolds number range of 12,000 to 29,000.

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Numerical Study of Heat Transfer Enhancement in Contour Corrugated Channel Using Water and Engine Oil

CFD letters ◽

10.37934/cfdl.12.12.1737 ◽

2020 ◽

Vol 12 (12) ◽

pp. 17-37

Author(s):

Naseer Dawood khata ◽

Zena Khalefa Kadim ◽

Kamil Abdulhussein Khalaf

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Heat Exchanger ◽

Wave Height ◽

Thermal Performance ◽

Numerical Study ◽

Hydraulic Performance ◽

Performance Criteria ◽

Engine Oil ◽

Corrugated Channel

Improving the design of geometrical parameters of heat exchanger leads to enhance heat transfer and makes it further compacted which in turn increases the efficiency of the thermal process, leading to save operating costs. In the present investigation, thermal and hydraulic performance of laminar flow of the trapezoidal, sinusoidal, and straight counter heat exchanger with water and engine oil was carried out numerically over Reynolds number ranges of 1100-2300 for water and 250 for engine oil. The effect of wave height and wavelength of both trapezoidal and sinusoidal on the thermal properties and hydraulic performance are studied. The numerical study showed that the effect of wave height on the Nusselt number was greater than that of wavelength in both trapezoidal and sinusoidal channels. The study also showed that the trapezoidal channel's influence on Nusselt number was higher than that of the sinusoidal channel and straight channel respectively. Thermal and flow characteristics are explored with the help of the streamwise velocity and isotherms contours for trapezoidal and sinusoidal-corrugated channels. In addition, the success of the heat exchanger design was evaluated by the results of the thermal performance criteria. The results of the thermal performance criteria at all wave heights and wavelength of the corrugated channel were greater than 1, which is indicating that the heat transfer rate is higher than the friction losses. Consequently, the use of corrugated surfaces in Contour heat exchangers can improve heat transfer in many applications.

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Heat transfer enhancement using second mode self-oscillating structures

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-07-2019-0583 ◽

2019 ◽

Vol 30 (7) ◽

pp. 3827-3842

Author(s):

Samer Ali ◽

Zein Alabidin Shami ◽

Ali Badran ◽

Charbel Habchi

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Laminar Flow ◽

Flow Regime ◽

Vortex Generator ◽

Reynolds Numbers ◽

Content Type ◽

Laminar Flow Regime ◽

Second Mode

Purpose In this paper, self-sustained second mode oscillations of flexible vortex generator (FVG) are produced to enhance the heat transfer in two-dimensional laminar flow regime. The purpose of this study is to determine the critical Reynolds number at which FVG becomes more efficient than rigid vortex generators (RVGs). Design/methodology/approach Ten cases were studied with different Reynolds numbers varying from 200 to 2,000. The Nusselt number and friction coefficients of the FVG cases are compared to those of RVG and empty channel at the same Reynolds numbers. Findings For Reynolds numbers higher than 800, the FVG oscillates in the second mode causing a significant increase in the velocity gradients generating unsteady coherent flow structures. The highest performance was obtained at the maximum Reynolds number for which the global Nusselt number is improved by 35.3 and 41.4 per cent with respect to empty channel and rigid configuration, respectively. Moreover, the thermal enhancement factor corresponding to FVG is 72 per cent higher than that of RVG. Practical implications The results obtained here can help in the design of novel multifunctional heat exchangers/reactors by using flexible tabs and inserts instead of rigid ones. Originality/value The originality of this paper is the use of second mode oscillations of FVG to enhance heat transfer in laminar flow regime.

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Oscillatory Heat Transfer in a Pipe Subjected to a Laminar Reciprocating Flow

Journal of Heat Transfer ◽

10.1115/1.2822673 ◽

1996 ◽

Vol 118 (3) ◽

pp. 592-597 ◽

Cited By ~ 46

Author(s):

T. S. Zhao ◽

P. Cheng

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Heat Flux ◽

Nusselt Number ◽

Numerical Study ◽

Temperature Cycle ◽

Uniform Heat Flux ◽

Fluid Temperature ◽

Cycle Space ◽

Reciprocating Flow

An experimental and numerical study has been carried out for laminar forced convection in a long pipe heated by uniform heat flux and subjected to a reciprocating flow of air. Transient fluid temperature variations in the two mixing chambers connected to both ends of the heated section were measured. These measurements were used as the thermal boundary conditions for the numerical simulation of the hydrodynamically and thermally developing reciprocating flow in the heated pipe. The coupled governing equations for time-dependent convective heat transfer in the fluid flow and conduction in the wall of the heated tube were solved numerically. The numerical results for time-resolved centerline fuid temperature, cycle-averaged wall temperature, and the space-cycle averaged Nusselt number are shown to be in good agreement with the experimental data. Based on the experimental data, a correlation equation is obtained for the cycle-space averaged Nusselt number in terms of appropriate dimensionless parameters for a laminar reciprocating flow of air in a long pipe with constant heat flux.

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3D Computational Analysis of Thermal and Hydraulic Performance of Louvered Fin Heat Exchanger With Variable Louver Angle and Louver Pitch

Volume 6B: Energy ◽

10.1115/imece2016-66534 ◽

2016 ◽

Cited By ~ 2

Author(s):

Abdulkerim Okbaz ◽

Ali Pınarbaşı ◽

Ali Bahadır Olcay

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Pressure Drop ◽

Flow Characteristics ◽

Hydraulic Performance ◽

Double Row ◽

Louvered Fin ◽

Goodness Factor ◽

Fluid Flow Characteristics ◽

Louvered Fins

In the present study, 3-D numerical simulations on heat and fluid flow characteristics of double-row multi-louvered fins heat exchanger are carried out. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles in the range of 20° ≤θ≤ 30°, louver pitches of Lp = 2,7mm, 3,5mm and 3,8mm and frontal velocities of Uin between 1.22 m/s and 3 m/s. The results are reported in terms of Colburn j-factor, Fanning friction factor f and area goodness factor j/f based on louver angle, louver pitch and Reynolds number. To understand local behavior of flow around louvered fins and heat exchanger tubes, flow visualization results of velocity vectors and stream-lines with temperature counters are presented. It is investigated that increasing louver angle enhances convective heat transfer while hydraulic performance decreases due to increased pressure drop. The flow noticeably behaves louver directed for all louver angles The flow can easily travel between different fins. This case study has been done to design and manufacture an industrial louver fin heat exchanger.

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CFD SIMULATION OF A PLATE HEAT EXCHANGER WITH TRAPEZOIDAL CHEVRON

Jurnal Teknologi ◽

10.11113/jt.v78.9580 ◽

2016 ◽

Vol 78 (8-4) ◽

Author(s):

Chin Yung Shin ◽

Normah Mohd-Ghazali

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Heat Exchanger ◽

Friction Factor ◽

Cfd Simulation ◽

General Pattern ◽

Plate Heat Exchanger ◽

Plate Heat ◽

Flow Configuration ◽

Heat Transfer Capacity

In this research, the trapezoidal shaped chevron plate heat exchanger (PHE) is simulated using computational fluid dynamics (CFD) software to determine its heat transfer capacity and friction factor. The PHE is modelled with chevron angles from 30° to 60°, and also the performances are compared with the plain PHE. The validation is done by comparing simulation result with published references using 30° trapezoidal chevron PHE. The Nusselt number and friction factor obtained from simulation model is plotted against different chevron angles. The Nusselt number and friction factor is also compared with available references, which some of the references used sinusoidal chevron PHE. The general pattern of Nusselt number and friction factor with increasing chevron angle agrees with the references. The heat transfer capacity found in current study is higher than the references used, and at the same time, the friction factor also increased. Besides this, it is also found that the counter flow configuration has better heat transfer capacity performance than the parallel flow configuration.

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Review on Heat Transfer Enhancement by Louvered Fin

International Journal of Engineering Materials and Manufacture ◽

10.26776/ijemm.06.01.2021.06 ◽

2021 ◽

Vol 6 (1) ◽

pp. 60-80

Author(s):

Samsul Islam ◽

Md. Shariful Islam ◽

Mohammad Zoynal Abedin

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Heat Exchanger ◽

Heat Transfer Enhancement ◽

Vortex Generator ◽

Transfer Enhancement ◽

Maximum Heat ◽

Louvered Fin ◽

Heat Transfer Improvement ◽

Better Than

The heat transfer enhancement is recycled in many engineering uses such as heat exchangers, refrigeration and air conditioning structures, chemical apparatuses, and automobile radiators. Hence many enhancing extended fin patterns are developed and used. In multi louvered fin, in this segment for multi-row fin and tube heat exchanger, an increase in heat transfer enhancement is found 58% for ReH = 350. When the Reynolds number is 1075, the temperature gradient is more distinct for greater louver angle that is the higher heat transfer enhanced for large louver angle. For variable louver angle heat exchanger, the maximum heat transfer improvement achieved by 118% Reynolds number at 1075. In the vortex generator for the delta winglet vortex generator, the extreme enhancement of heat transfer increased to 16% compared to the baseline geometry (at ReDh = 600). For a compact louvered heat exchanger, the results showed that a regular arrangement of louvered fins gives a 9.3% heat transfer improvement. In multi-region louver fins and flat tubes heat exchanger, the louver fin with 4 regions and the louver fin with 6 regions are far better than the conventional fin in overall performance. At the same time, the louver fin with 6 regions is also better than the louver fin with 4-region. The available work is in experimental form as well as numerical form performed by computational fluid dynamics.

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