scholarly journals A MCDM Methodology to Determine the Most Critical Variables in the Pressure Drop and Heat Transfer in Minichannels

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2069
Author(s):  
Eloy Hontoria ◽  
Alejandro López-Belchí ◽  
Nolberto Munier ◽  
Francisco Vera-García
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Saturation Pressure ◽  
Computational Cost ◽  
Urban Systems ◽  
Condensation Process ◽  
Geometrical Parameters ◽  
Maximum Heat ◽  
Maximum Heat Transfer

This paper proposes a methodology aiming at determining the most influent working variables and geometrical parameters over the pressure drop and heat transfer during the condensation process of several refrigerant gases using heat exchangers with pipes mini channels technology. A multi-criteria decision making (MCDM) methodology was used; this MCDM includes a mathematical method called SIMUS (Sequential Interactive Modelling for Urban Systems) that was applied to the results of 2543 tests obtained by using a designed refrigeration rig in which five different refrigerants (R32, R134a, R290, R410A and R1234yf) and two different tube geometries were tested. This methodology allows us to reduce the computational cost compared to the use of neural networks or other model development systems. This research shows six variables out of 39 that better define simultaneously the minimum pressure drop, as well as the maximum heat transfer, saturation pressure fluid entering the condenser being the most important one. Another aim of this research was to highlight a new methodology based on operation research for their application to improve the heat transfer energy efficiency and reduce the CO2 footprint derived of the use of heat exchangers with minichannels.

Significance of Delta Winglets on the Air Side Performance of Flat Finned Versus Wavy Finned-Tube Heat Exchangers

2020 ◽  
Author(s):  
Tariq Amin Khan ◽  
Nasir Mehdi Gardezi ◽  
Wei Li ◽  
Yang Zhou ◽  
Zahid Ayub
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Heat Exchangers ◽  
Three Dimensional ◽  
Finned Tube ◽  
Maximum Heat ◽  
Multi Objective ◽  
Multi Objective Genetic Algorithm ◽  
Maximum Heat Transfer ◽  
Side Flow

Abstract The performance on the air side flow is often limited due to its lower heat transfer coefficient. This work is related to numerical simulation to study the significance of employing delta winglets in flat finned and wavy finned-tube heat exchangers. For this purpose, three-dimensional simulation data and a multi-objective genetic algorithm are employed. The angle of attack (α) of delta winglets and Reynolds number varied from 15° to 75° and 500 to 1300, respectively. Employing delta winglets has increased the heat transfer per unit temperature and per unit volume (Z) and the fan power per unit core volume (E) for both flat finned and wavy finned-tube heat exchangers. To achieve a maximum heat transfer enhancement and a minimum friction factor, the optimal values of these parameters (Re and α) are calculated using the Pareto optimal strategy. For this purpose, CFD data, a surrogate model (neural network) and a multi-objective optimization genetic algorithm are combined. Results show that the performance of wavy finned-tube heat exchangers is higher than flat-finned tube heat exchangers which signify the importance of delta winglets in the wavy finned-tube heat exchangers.

A study of non-redirection louvre fin-and-tube heat exchangers

1998 ◽  
Vol 212 (1) ◽  
pp. 1-14 ◽  
Author(s):  
C-C Wang ◽  
Y-P Chang ◽  
K-Y Chi ◽  
Y-J Chang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Wind Tunnel ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Geometrical Parameters ◽  
Tube Size ◽  
Collar Diameter ◽  
Fanning Friction Factor

Extensive experiments on the heat transfer and pressure drop characteristics of louvre finand-tube heat exchangers were carried out. In the present study, 14 samples of non-redirection louvre fin-and-tube heat exchangers with different geometrical parameters, including the number of tube row, fin pitch and tube size, were tested in a wind tunnel. Results are presented as plots of the Fanning friction factor f and the Colburn j factor against Reynolds number based on the tube collar diameter in the range of 300–8000.

Multi-Objective Design Optimization of Rotating Regenerative Air Preheater Using Genetic Algorithm

2018 ◽  
Author(s):  
Limin Wang ◽  
Yufan Bu ◽  
Xun Chen ◽  
Xiaoyang Wei ◽  
Dechao Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Genetic Algorithm ◽  
Pressure Drop ◽  
Design Optimization ◽  
Hydraulic Calculation ◽  
Maximum Heat ◽  
Multi Objective ◽  
Upper Limit ◽  
Maximum Heat Transfer ◽  
Conflicting Objectives

In previous references, no study has been done on the optimization of rotary regenerative air preheaters (RAPHs) used in coal-fired power plants yet. The key structure parameters of RAPH include rotor radius, fluid section angles and matrix layer heights. In this study, work on the multi-objective design optimization of an RAPH was conducted by combing the thermal hydraulic calculation program which is developed to calculate the temperature and the pressure drop and the non-dominated sorting genetic algorithm (NSGA-II). The maximum heat transfer rate and the minimum friction, namely minimum outlet gas temperature and pressure drop, are considered as the conflicting objectives in the multi-optimization. The layer heights, rotor radius, angles of fluid sections and heights of matrix layers are involved in the design variables in the optimization. The optimization includes three cases in which the rotor radius upper limits are 7 m, 8 m and 9 m respectively. Sets of the Pareto-optimal front points were obtained for the different cases. The obtained optimal air-preheaters with larger upper limit of rotor radius would have better Pareto results. The optimum rotor radius is the upper limit value for different design range of rotor radius. The air-preheaters with larger upper design limit of rotor radius would have better Pareto results. In other words, if the upper design limit of rotor radius is too small, all the Pareto points in this case could not satisfy the performance requirements of heat transfer and friction, and the only way is to increase the upper design limit of rotor radius. The ratio of each optimum fluid section angle is determined by the fluid flow rate of each section.

Scrutiny the Heat Transfer Effect in an Annulus by Mounting Axial Fins with Different Shapes: Without and with Taylor Number

2021 ◽  
Vol 409 ◽  
pp. 142-157
Author(s):  
Farouk Kebir ◽  
Youcef Attou
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Annular Channel ◽  
Reynolds Stress Model ◽  
Taylor Number ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Rsm Model ◽  
Energy Equations ◽  
The Impact

This study aimed to investigate numerically the heat transfer improvement and pressure drop inside annular channel of a rotor-stator provided with fins mounted on the stator without and with Taylor number. The impact of mounting various types of fins (triangular, rectangular, trapezoidal shapes with small and large base) is studied by varying the fin width b from 0 to 14 mm. In the presence of axial air flow, numerical simulations are carried out by solving the governing continuity, momentum and energy equations of turbulent flow in cylindrical coordinates using the Finite Volume Method. The results obtained by Reynolds Stress Model RSM model have indicated that the heat transfer enhances as the surface area of the fins and the effective Reynolds number increase, while there is an increase in pressure drop. Furthermore, we have shown that the presence of Taylor number has a slight increase in Nusselt number and pressure drop compared to the case without Taylor number. Among the four geometries, it is found that the rectangular cavity is the best geometry which gives maximum heat transfer and minimum pressure loss.

Numerical Analysis of Fluid Flow and Heat Transfer of Flow Between Parallel Plates Having Rectangular Shape Micromixer

2017 ◽  
Vol 10 (1) ◽  
Author(s):  
Sudip Shyam ◽  
Aparesh Datta ◽  
Ajoy Kumar Das
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Secondary Flows ◽  
Parallel Plates ◽  
Maximum Enhancement ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Study Results ◽  
Study Heat Transfer

In this study, heat transfer and fluid flow of de-ionized water in two-dimensional parallel plates microchannel with and without micromixers have been investigated for various Reynolds numbers. The effects of heat transfer and fluid flow on height, diameter of micromixer, and also distance between the two micromixers are carried out in the study. Results showed that the diameter of the micromixer does not have much effect on heat transfer with a maximum enhancement of 9.5%. Whereas heat transfer gets enhanced by 85.57% when the height of the micromixer is increased from 100 μm to 400 μm, and also heat transfer gets improved by 11.45% when sb2 is increased from 4L to 5L. The separation and reattachment zone at the entry and exit of the micromixer cause the increase in heat transfer with the penalty of pressure drop. It is also found that increase of Reynolds number increases the intensity of the secondary flows leads to rapid increase in heat transfer and pressure drop. Finally, the optimized structure of micromixer is found out based on maximum heat transfer and minimum pressure drop.

A Review on Nanofluid Heat Pipe

2014 ◽  
Author(s):  
Maryam Shafahi ◽  
Kevin Anderson ◽  
Ali Borna ◽  
Michael Lee ◽  
Alex Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Working Fluid ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Medical Instruments ◽  
Thermo Physical Properties

This paper reviews the improvement in the heat pipe’s performance using nanofluid as the working fluid. The use of nanofluid enhances heat transfer in the heat pipe due to its improved thermo-physical properties, such as a higher thermal conductivity. Nanofluids proved to be the innovative approach to a variety of applications, such as electronics, medical instruments, and heat exchangers. The influence of different nanoparticles on heat pipe’s performance has been studied. Utilizing nanofluid as the working fluid leads to a significant reduction in heat pipe thermal resistance, an increase in maximum heat transfer, and an improvement of heat pipe thermal performance.

scholarly journals Numerical prediction of heat transfer phenomena from a chip assembly for low Reynolds number

2011 ◽  
Vol 15 (2) ◽  
pp. 379-388
Author(s):  
Srinivas Bhatta ◽  
Seetharam Ramarao ◽  
Kankanhalli Seetharamuω
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Three Dimensional ◽  
Circuit Board ◽  
Bottom Plate ◽  
Moderate Pressure ◽  
Maximum Heat ◽  
Square Channel ◽  
Maximum Heat Transfer

A three dimensional study of heat transfer from three heated blocks in a square channel at a Reynolds number of 108 with height of the chip assembly as the characteristic length is presented. Heated blocks affixed to the bottom plate represent electronic chips mounted on horizontal circuit board. A hexahedron block is affixed on to the top shrouding wall over the heated section. Thickness of this block is varied to study the effect on heat transfer from the chip assembly. A block of thickness equal to the passage between substrates produces maximum heat transfer enhancement. A block over the first passage enhances heat transfer from both immediate upstream and downstream chips considerably. A block over each recirculation zone produces moderate heat transfer from all the chips for a moderate pressure-drop. It is also observed that addition of blocks in the top plate does not add much to the pressure-drop in the duct.

Heat Transfer Augmentation and Suppression in Optimal Rotating Cylinders in Cross-Flow

2011 ◽  
Author(s):  
Tunde Bello-Ochende ◽  
Josua P. Meyer ◽  
Oluseun I. Ogunronbi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Computational Domain ◽  
Maximum Heat ◽  
Dimensionless Pressure ◽  
First Case ◽  
Maximum Heat Transfer ◽  
Drop Number

A steady-state two dimensional numerical simulation was carried out to optimize the heat transfer rate density from cylinders under different conditions. The geometric design of the cylinders was varied in two ways. In the first case the cylinders are located on a plane where their leading edges are aligned, and in the second case the cylinders are aligned on a plane which passes through their respective centre-lines. The rotation of the cylinders is within the range of 0 ≤ ω˜ ≤ 1, and the dimensionless pressure drop number, Be, which drives the flow is in the range of 10 ≤ Be ≤ 104. The continuity, momentum and energy equations describing the flow of the coolant, across the cylinders in the computational domain are performed using a computational fluid dynamics code, the results obtained were validated by comparing it with past results in the open literature for stationary cylinders. The effects of the various parameters (dimensionless pressure drop number, rotation) on the maximum heat transfer rate density from the cylinders in terms of augmentation and the suppression were analysed and reported.

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