Numerical Study of Flow and Heat Transfer Enhancement by Using Delta Winglets in a Triangular Wavy Fin-and-Tube Heat Exchanger

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Liting Tian ◽  
Yaling He ◽  
Pan Chu ◽  
Wenquan Tao
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Numerical Study ◽  
Attack Angle ◽  
Geometrical Parameters ◽  
Tube Heat Exchanger ◽  
Delta Winglet

In this paper, three-dimensional numerical simulations with renormalization-group (RNG) k-ε model are performed for the air-side heat transfer and fluid flow characteristics of wavy fin-and-tube heat exchanger with delta winglet vortex generators. The Reynolds number based on the tube outside diameter varies from 500 to 5000. The effects of different geometrical parameters with varying attack angle of delta winglet (β=30 deg, β=45 deg, and β=60 deg), tube row number (2–4), and wavy angle of the fin (θ=0–20 deg) are examined. The numerical results show that each delta winglet generates a downstream main vortex and a corner vortex. The longitudinal vortices are disrupted by the downstream wavy trough and only propagate a short distance along the main flow direction but the vortices greatly enhance the heat transfer in the wake region behind the tube. Nusselt number and friction factor both increase with the increase in the attack angle β, and the case of β=30 deg has the maximum value of j/f. The effects of the tube row number on Nusselt number and friction factor are very small, and the heat transfer and fluid flow become fully developed very quickly. The case of θ=5 deg has the minimum value of Nusselt number, while friction factor always increases with the increase in wavy angle. The application of delta winglet enhances the heat transfer performance of the wavy fin-and-tube heat exchanger with modest pressure drop penalty.

Numerical Study of Shellside Performance of Heat Transfer and Flow Resistance for Heat Exchanger with Trefoil-Hole Baffles

2012 ◽  
Vol 557-559 ◽  
pp. 2141-2146
Author(s):  
Yong Hua You ◽  
Ai Wu Fan ◽  
Chen Chen ◽  
Shun Li Fang ◽  
Shi Ping Jin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Numerical Study ◽  
Shell Side ◽  
Tube Heat Exchanger

Trefoil-hole baffles have good thermo-hydraulic performances as the support of heat pipes, however the published research paper is relatively limited. The present paper investigates the shellside thermo-hydraulic characteristics of shell-and-tube heat exchanger with trefoil-hole baffles (THB-STHX) under turbulent flow region, and the variations of shellside Nusselt number, pressure loss and overall thermo-hydraulic performance (PEC) with Reynolds number are obtained for baffles of varied pitch with the numerical method. CFD results demonstrate that the trefoil-hole baffle could enhance the heat transfer rate of shell side effectively, and the maximal average Nusselt number is augmented by ～2.3 times that of no baffle, while average pressure loss increases by ～9.6 times. The PEC value of shell side lies in the range of 16.3 and 73.8 kPa-1, and drops with the increment of Reynolds number and the decrement of baffle pitch, which indicates that the heat exchanger with trefoil-hole baffles of larger pitch could generate better overall performance at low Reynolds number. Moreover, the contours of velocity, turbulent intensity and temperature are presented for discussions. It is found that shellside high-speed jet, intensive recirculation flow and high turbulence level could enhance the heat transfer rate effectively. Besides good performance, THB-STHXs are easily manufactured, thus promise widely applied in various industries.

Convective heat transfer and fluid flow characteristics in fin and oval-tube heat exchanger

2021 ◽  
Vol 15 (2) ◽  
pp. 7936-7947
Author(s):  
Yamina Abdoune ◽  
Sahel Djamel ◽  
Benzeguir Redouane ◽  
Alem Karima
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Tube Heat Exchanger ◽  
Baseline Case ◽  
Oval Tube ◽  
The Heat Transfer Coefficient

The forced convective heat transfer behavior of a turbulent air flow, steady and Newtonian over a fin and oval-tube heat exchanger has been examined numerically. Where, the effect of the tube tilt angle (α) on the heat transfer coefficient and the friction factor was tested. The inclination angle of the oval-tubes going from 0° (Baseline case) to 90° with a step of 10°. The fluid flows and heat transfer characteristics are presented for Reynolds numbers ranging from 3.000 to 12.000. All investigations are carried out with the help of the CFD ANSYS Fluent. Heat transfer coefficient results in the term of the Nusselt number are validated with the available experimental data and a maximum deviation of 9 % is observed. Reasonable agreement is found. The obtained results show that the tube's inclination angle of 20° is the best design which significantly removes the hot spots behind the tubes, thus giving an increase in the heat transfer coefficient of 13 % compared to the baseline case. In addition, useful correlations are developed to predict Nusselt number and friction factor in the fin and oval-tube heat exchanger.

Heat Transfer Enhancement in a Double Pipe Heat Exchanger by Insertion of Propeller-Type Swirl Generators

2010 ◽  
Author(s):  
Khwanchit Wongcharee ◽  
Somsak Pethkool ◽  
Chinaruk Thianpong
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Operating Conditions ◽  
Interval Length ◽  
Tube Heat Exchanger ◽  
Nusselt Numbers ◽  
Plain Tube

This paper describes an experimental study of turbulent convective heat transfer and flow friction characteristics in a double tube heat exchanger equipped with propellers (2 blade-type). The propellers are used as the decaying swirl generators in the inner tube. The experiments were performed using the propellers with four different interval lengths (l = 1D, 2D, 3D and 4D where D is diameter of the inner tube), for the Reynolds number ranging from 5000 to 32,000, using water with temperature of 27°C and 70°C as cold and hot working fluids, respectively. The data of the tube equipped with the propellers are reported together with those of the plain tube, for comparison. The obtained results demonstrate that the heat transfer rate in term of Nusselt number (Nu) and friction factor (f) in the tube with propellers are higher than those in the plain tube at the similar operating conditions. This is due to the chaotic mixing and efficient interruption of thermal boundary layer caused by the propellers. In addition, the Nusselt number and friction factor in the tube fitted with the propellers increase as the interval length decreases. Depending on Reynolds number and interval length, Nusselt numbers and friction factors in the tube fitted with the propellers are augmented to 1.95 to 2.3 times and 5.8 to 13.2 times of those in the plain tube. In addition, the correlations of the Nusselt number (Nu) and the friction factor (f) for tube fitted with the propellers are reported and the performance evaluation to access the real benefits of using the turbulators is also determined.

scholarly journals Numerical Study of Heat Transfer Enhancement of Internal Flow Using Double-Sided Delta-Winglet Tape Insert

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3170 ◽  
Author(s):  
Agung Wijayanta ◽  
Muhammad Aziz ◽  
Keishi Kariya ◽  
Akio Miyara
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Thermal Performance ◽  
Numerical Study ◽  
Performance Factor ◽  
Thermal Performance Factor ◽  
Enhanced Tube ◽  
Delta Winglet ◽  
Experimental Values

A numerical study was performed to investigate the thermal performance characteristics of an enhanced tube heat exchanger fitted with punched delta-winglet vortex generators. Computational fluid dynamics modeling was applied using the k–ε renormalized group turbulence model. Benchmarking was performed using the results of the experimental study for a similar geometry. Attack angles of 30°, 50°, and 70° were used to investigate the heat transfer and pressure drop characteristics of the enhanced tube. Flow conditions were considered in the turbulent region in the Reynolds number range of 9100 to 17,400. A smooth tube was employed for evaluating the increment in the Nusselt number and the friction factor characteristics of the enhanced tube. The results show that the Nusselt number, friction factor, and thermal performance factor have a similar tendency. The presence of this insert offers a higher thermal performance factor as compared to that obtained with a plain tube. Vortex development in the flow structure aids in generating a vortex flow, which increases convective heat transfer. In addition, as the angle is varied, it is observed that the largest attack angle provides the highest thermal performance factor. The greatest increase in the Nusselt number and friction factor, respectively, was found to be approximately 3.7 and 10 times greater than those of a smooth tube. Through numerical simulations with the present simulation condition, it is revealed that the thermal performance factor approaches the value of 1.1. Moreover, the numerical and experimental values agree well although they tend to be different at high Reynolds number conditions. The numerical and experimental values both show similar trends in the Nusselt number, friction factor, and thermal performance factor.

Thermohydraulic optimization of triple concentric-tube heat exchanger: A multi-objective approach

2018 ◽  
Vol 233 (3) ◽  
pp. 589-600 ◽  
Author(s):  
Tarikayehu Amanuel ◽  
Manish Mishra
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Effective Parameters ◽  
Ansys Fluent ◽  
Tube Heat Exchanger ◽  
Large Growth ◽  
Design Factors ◽  
Response Variables

In the present study, optimization of heat transfer and pressure drop characteristics in a triple concentric tube heat exchanger has been done using the results of numerical simulation. A commercial CFD software ANSYS Fluent v17.0 has been employed for simulating the flow and heat transfer, while optimization has been done by Response surface methodology (RSM) and Genetic algorithm (GA). The effective parameters in the study are Reynolds number (2500 ≤ Re ≤ 10,000) and Length to hydraulic diameter ratio (100 ≤ L/Dh ≤ 220). The optimum values, as well as the functional relationship between the design factors (Re and L/Dh) and response variables (Nu and f), have also been developed. It has been found that both the design factors (Re and L/Dh) have a strong influence on the response variables (Nu and f). With the increase in Re (flow rate), a large growth in Nusselt number and decline in friction factor has been observed. However, with the increase in L/Dh, an enormous decrease in both Nusselt number and friction factor has been found.

Investigation of Conjugate Heat Transfer in a Fin-and-Tube Heat Exchanger

2014 ◽  
Author(s):  
M. Kadja ◽  
R. Mebrouk
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Turbulence Modeling ◽  
Numerical Study ◽  
Turbulence Models ◽  
Momentum Conservation ◽  
Conservation Equations ◽  
Tube Heat Exchanger

A numerical study was achieved on a realistic fin-and-tube heat exchanger in order to investigate its heat transfer and friction characteristics. The computations assume a steady-state heat transfer and fluid flow. Nusselt number and friction factor characteristics of the heat exchanger are determined for various values of Reynolds numbers. Conjugate convection-conduction energy conservation equations in 3 dimensions have been solved along with mass and momentum conservation equations in order to determine these characteristics. Both laminar and turbulent flow regimes are considered. The effect of turbulence modeling was investigated using three different models (the one equation Spalart-Allmaras turbulence model, the standard k-ε model and the RSM model). The computations allowed the determination of the dynamic and thermal fields. Model validation was carried out by comparing the calculated friction factor f and Colburn j-factor to experimental results found in the literature. The plotted results showed a qualitatively good agreement between numerical results and experimental data. The results obtained also showed that the simplest of the three turbulence models tested (i.e. Spalart-Allmaras) gives the closest values to the experimental data.

scholarly journals A numerical study of flow and temperature fields in circular tube heat exchanger with elliptic vortex generators

2008 ◽  
Vol 12 (2) ◽  
pp. 129-136 ◽  
Author(s):  
Ehsan Mohseni-Languri ◽  
Mofid Gorji-Bandpy ◽  
Reza Masoodi
Keyword(s):  
Nusselt Number ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Circular Tube ◽  
Numerical Study ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Computational Domain ◽  
Tube Heat Exchanger ◽  
Energy Equations

The two-dimensional fluid flow and heat transfer in a circular tube heat exchanger with two elliptic obstacles at the back is studied numerically. The computational domain consists of a circular tube and two elliptic obstacles that are situated after the tube, such that the angle between their centerlines and the direction of free coming flow is 45 degrees. The numerical solution is achieved by numerical integration of full Navier-Stokes and energy equations over the computational domain, using finite volume method. The fluid flow is assumed to be laminar, incompressible and steady-state with constant thermo-physical characteristics. In this study major thermo-fluid parameters such as temperature, pressure and velocity fields as well as Nusselt number and friction factor variations are computed and some results are presented in the graphs. It is shown that using of elliptic obstacles leads to an increase in the average Nusselt number and also pressure. .

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