scholarly journals CFD Simulation of Heat Transfer from Elliptic Tube Bundle Buried in a Bubbling Fluidized Bed

2019 ◽  
pp. 1-12
Author(s):  
M. A. Abd-Rabbo ◽  
R. Y. Sakr ◽  
M. A. Mohammad ◽  
M. M. Mandour
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Granular Flow ◽  
Average Nusselt Number ◽  
Solid Phase ◽  
Tube Bundle ◽  
Tube Heat Exchanger

In the present work, numerical simulations are performed to study heat transfer characteristics and fluid flow around elliptic tube heat exchanger. The results for heat transfer coefficient between immersed inline and staggered bundles of horizontal smooth tubes and air-fluidized bed of pulverized coal, dp = 2 mm, are reported within the range of fluidization number, Usup/ Umf, ranges from 1 to 1.4. Heat transfer as well as multiphase flow dynamics in fluidized bed is modelled using the Eulerian-Eulerian and the Two-Fluid Model (TFM) with Kinetic Theory of Granular Flow (KTGF) to describe the granular flow characteristics of the solid phase. The average heat transfer coefficient for the present work is compared with that obtained from the well-known correlation of circular cylinder and a noticed improvement is observed. It is noticed that, the average Nusselt number increases with fluidization number. Also, it is noticed that, the average Nusselt number in case of staggered tubes bundle is higher than the case of inline tubes bundle. The inline tube bundle has lesser pressure drop than the staggered tube bundle.

scholarly journals Transient behavior of a plate-fin-and-tube heat exchanger taking into account different heat transfer coefficients on the individual tube rows

2019 ◽  
Vol 128 ◽  
pp. 04001
Author(s):  
Dawid Taler ◽  
Jan Taler ◽  
Katarzyna Wrona
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Analytical Formula ◽  
Cfd Modeling ◽  
Tube Heat Exchanger ◽  
Individual Tube ◽  
The Heat Transfer Coefficient

Experimental studies of multi-row plate-fin heat exchangers show that the highest average heat transfer coefficient on the air side occurs in the first row of tubes when the air velocity in front ofthe exchanger is less thanapproximately 3.5 m/s. In the subsequent rows of tubes up to about the fourth row the heat transfer coefficient decreases. In the fifth and further rows, it can be assumed that the heat transfer coefficient is equal in each tube row. It is necessary to find the relationships fortheair–side Nusselt number on each tube row to design a plate–fin and tube heat exchanger(PFTHE) with the appropriate number of tube rows. The air–side Nusselt number correlations canbe determined experimentally or by CFD modeling (Computational and Fluid Dynamics). The paper presents a newmathematical model of the transient operation of PFTHE, considering that the Nusselt numbers on the air side of individual tube rows are different. The heat transfer coefficient on an analyzed tube row was determined from the equality condition of mass– average air temperature differences on agiven tube row determined using the analytical formula and CFD modeling. The results of numerical modelingwere compared with the results of the experiments.

Experimental and numerical analysis of heat transfer in the helically coiled heat exchanger

2019 ◽  
Vol 30 (6) ◽  
pp. 2935-2951 ◽  
Author(s):  
Tomasz Sobota
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Least Squares Method ◽  
Thermal Design ◽  
Content Type ◽  
Tube Heat Exchanger

Purpose The knowledge of the heat transfer coefficient is important for the proper design of heat exchangers as well as for the determination of the working medium outlet temperatures. This paper aims to present a method of simultaneous determination of coefficients in correlation formulas for the Nusselt number on both sides of the heat transfer surface. Design/methodology/approach The idea of the developed method is based on determining such a values of the coefficients in Nusselt number correlations that fulfill the condition of equality between the measured and calculated temperature at the outlet of heat exchanger in terms of least squares method. To test the proposed method, a special experimental installation was built. The heat transfer in helically coiled tube-in-tube heat exchanger was examined for the wide range of temperature changes and volumetric flow rates of working fluid. Findings The simulation results were validated with an experimental data. The results show that the heat transfer coefficient of the counter-current is higher than the co-current flow in helically coiled heat exchanger. This phenomenon can be beneficial particularly in the laminar flow regime. Research limitations/implications The correlation for the Nusselt number as a function of the Reynolds and Prandtl numbers for hot and cold liquid was obtained with the least squares method for the experimental data. Practical implications The presented method allows for the simultaneous determination of heat transfer coefficient on both sides of the wall without the necessity of indirect calculation of the overall heat transfer coefficient. The presented method can be used in the thermal design of various type heat exchangers. Originality/value This work presents the new methodology of determination correlations for the helically coiled tube-in-tube heat exchanger for co-current and counter-current arrangement, which can be used in thermal design.

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.

Local Heat Transfer in a Rotating Square Channel With Jet Impingement

1999 ◽  
Vol 121 (4) ◽  
pp. 811-818 ◽  
Author(s):  
S.-S. Hsieh ◽  
J.-T. Huang ◽  
C.-F. Liu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Average Nusselt Number ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient

The influence of rotation and jet mass flow rate on the local heat transfer coefficient for a single confined impinging round jet with a fixed jet-to-wall spacing of H/d = 5 was studied for the jet Reynolds number from 6500 to 26,000 and the rotational Reynolds number from 0 to 112,000. The local heat transfer coefficient along the surface is measured and the effect of the rotation on the stagnation (peak) point, local and average Nusselt number, is presented and discussed. Furthermore, a correlation was developed for the average Nusselt number in terms of the parameters of Rej and ReΩ. In general, the combined jet impingement and rotation effect are shown to affect the heat transfer response. Rotation decreases the average Nusselt number values from 15 to 25 percent in outward and inward radial flow, respectively. Finally, comparisons of the present data with existing results for multijets with rotation were also made.

scholarly journals Experimental investigation of heat transfer performance coefficient in tube bundle of shell and tube heat exchanger in two-phase flow

2014 ◽  
Vol 35 (1) ◽  
pp. 87-98 ◽  
Author(s):  
Marcin Karaś ◽  
Daniel Zając ◽  
Roman Ulbrich
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Tube Bundle ◽  
Limiting Current ◽  
Phase Flow ◽  
Two Phase ◽  
Tube Heat Exchanger

Abstract This paper presents the results of studies in two phase gasliquid flow around tube bundle in the model of shell tube heat exchanger. Experimental investigations of heat transfer coefficient on the tubes surface were performed with the aid of electrochemical technique. Chilton-Colburn analogy between heat and mass transfer was used. Twelve nickel cathodes were mounted on the outside surface of one of the tubes. Measurement of limiting currents in the cathodic reduction of ferricyanide ions on nickel electrodes in aqueous solution of equimolar quantities of K3Fe(CN)6 and K4Fe(CN)6 in the presence of NaOH basic solution were applied to determine the mass transfer coefficient. Controlled diffusion from ions at the electrode was observed and limiting current plateau was measured. Measurements were performed with data acquisition equipment controlled by software created for this experiment. Mass transfer coefficient was calculated on the basis of the limiting current measurements. Results of mass transfer experiments (mass transfer coefficient) were recalculated to heat transfer coefficient. During the experiments, simultaneously conducted was the the investigation of two-phase flow structures around tubes with the use of digital particle image velocimetry. Average velocity fields around tubes were created with the use of a number of flow images and compared with the results of heat transfer coefficient calculations.

scholarly journals STUDY OF THE INFLUENCE OF THE TUBE POSITION IN THE TUBE BUNDLE OF THE SHELL AND TUBE HEAT EXCHANGER ON THE PROCESS OF HEAT TRANSFER

2020 ◽  
Vol 1 (22) ◽  
pp. 99-108
Author(s):  
K. V. Lunyaka ◽  
◽  
O. I. Kliuiev ◽  
S. A. Rusanov ◽  
O. O. Kliuieva ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Tube Bundle ◽  
Uniform Field ◽  
Uniform Heating ◽  
Transfer Coefficients ◽  
Tube Heat Exchanger ◽  
Shell And Tube

The paper is concerned with an issue of liquid distribution in the diametrical bank tubes of the shell and tube heat exchanger. The experimental-theoretical approach for the research has been applied. The data on the determination of velocities of the heated liquid through the pipes of the heat exchanger have been obtained and processed. The research was carried out at the created experimental factory. Water at a temperature of 20 ºС has been supplied to the tubes. The temperature of the water has been maintained by a thermostat. The temperature at the outlet of the tube has been measured with a thermocouple element. Water (heat conductor,) at a temperature of 60, 80 or 95 ºС has been circulating in the outside of tubes space. The temperature of the water has been maintained by pumping it through a thermostat. The velocities of the heated liquid in the diametric bank tubes have been determined, which differed considerably depending on the position of the tube. Consequently, the results of the research obtained have discovered the significant deviations of such parameters as the liquid temperature at the outlet of the apparatus, tube wall temperature and heat transfer coefficients between the tube and heated liquid. The distribution insert has been used, in order to match the above-mentioned indicators. The distribution insert is a disk with the optimized holes. The alignment of the liquid velocities through the tubes of the diametric bank has been observed, which has consequently led to the uniform heating of both the central and side tubes. The study outcome has proven to be the solution to prevent the overheating of the peripheral tubes. Thus, the generation of a uniform field of velocities for the heat transfer agent through the tubes of the shell and tube heat exchanger contributes to the uniform heating of both central and peripheral tubes, and increases the heat transfer coefficient in the side tubes. The conclusion has been drawn that the reason for the failure or heat transfer low efficiency in the peripheral tubes of the shell and tube heat exchanger is the nonuniform distribution of liquid velocities in different tubes and as a consequence, the low heat transfer coefficient in those tubes where the velocity is low.

scholarly journals Investigation of Heat Transfer in a Large-Scale External Heat Exchanger with Horizontal Smooth Tube Bundle

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5553
Author(s):  
Artur Blaszczuk ◽  
Szymon Jagodzik
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Fluidized Bed ◽  
Tube Bundle ◽  
External Heat ◽  
Average Heat Transfer Coefficient ◽  
Average Heat ◽  
External Heat Exchanger

In the research work, energy transport between a dense fluidized bed and submerged horizontal tube bundle is analyzed in the commercial external heat exchanger (EHE). In order to investigate the heat transfer behavior, the authors carried out eight performance tests in a fluidized bed heat exchange chamber with a cross-section of 2.7 × 2.3 m in depth and width and a height of 1.3 m. The authors have been developing a mechanistic model for the prediction of the average heat transfer coefficient, which includes the effect of the geometric structure of the tube bundle and the location of the heat transfer surface on the heat transfer rate. The computational results depict that the average heat transfer coefficient is essentially affected by superficial gas velocity and suspension density rather than bed particle size. The empirical correlations have been proposed for predicting heat transfer data since the existing literature data is not sufficient for industrial fluidized bed heat exchangers. On the basis of the evaluated operating conditions of an external heat exchanger, the optimal conditions where heat transfer occurs could be deduced. The developed mechanistic heat transfer model is validated by experimental data under the examined conditions.

Numerical simulation of the effect of baffle cut and baffle spacing on shell side heat exchanger performance using CFD

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Swanand Gaikwad ◽  
Ashish Parmar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Numerical Results ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Two Parameters

AbstractHeat exchangers possess a significant role in energy transmission and energy generation in most industries. In this work, a three-dimensional simulation has been carried out of a shell and tube heat exchanger (STHX) consisting of segmental baffles. The investigation involves using the commercial code of ANSYS CFX, which incorporates the modeling, meshing, and usage of the Finite Element Method to yield numerical results. Much work is available in the literature regarding the effect of baffle cut and baffle spacing as two different entities, but some uncertainty pertains when we discuss the combination of these two parameters. This study aims to find an appropriate mix of baffle cut and baffle spacing for the efficient functioning of a shell and tube heat exchanger. Two parameters are tested: the baffle cuts at 30, 35, 40% of the shell-inside diameter, and the baffle spacing’s to fit 6,8,10 baffles within the heat exchanger. The numerical results showed the role of the studied parameters on the shell side heat transfer coefficient and the pressure drop in the shell and tube heat exchanger. The investigation shows an increase in the shell side heat transfer coefficient of 13.13% when going from 6 to 8 baffle configuration and a 23.10% acclivity for the change of six baffles to 10, for a specific baffle cut. Evidence also shows a rise in the pressure drop with an increase in the baffle spacing from the ranges of 44–46.79%, which can be controlled by managing the baffle cut provided.

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