Application of a genetic algorithm to optimize the refrigerant circuit of fin-and-tube heat exchangers for maximum heat transfer or shortest tube

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.

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

Energies ◽

10.3390/en14082069 ◽

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.

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

Volume 2: Heat Exchanger Technologies; Plant Performance; Thermal Hydraulics and Computational Fluid Dynamics; Water Management for Power Systems; Student Competition ◽

10.1115/power2018-7417 ◽

2018 ◽

Cited By ~ 1

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.

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A Review on Nanofluid Heat Pipe

Volume 8B: Heat Transfer and Thermal Engineering ◽

10.1115/imece2014-39431 ◽

2014 ◽

Cited By ~ 2

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.

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A General Analytical Approach for Defining Effectiveness in Ideal Two Fluid Heat Exchangers

Advanced Energy Systems ◽

10.1115/imece2002-33142 ◽

2002 ◽

Author(s):

Devashish Shrivastava ◽

Tim Ameel

Keyword(s):

Heat Transfer ◽

Temperature Difference ◽

Heat Exchangers ◽

Maximum Temperature ◽

Maximum Temperature Difference ◽

Maximum Heat ◽

Maximum Heat Transfer ◽

Laws Of Thermodynamics ◽

Analytical Development ◽

Two Fluid

A general analytical development, based on the first and second laws of thermodynamics, is used to define the maximum possible heat transfer in an ideal two-fluid exchanger as well as the maximum possible temperature differences for both fluid streams. It is shown that the conventional expression for the maximum possible heat transfer in ideal two-fluid heat exchangers is a special case of the general expressions. The application of both the first and second laws of thermodynamics in defining the maximum possible heat transfer and maximum possible temperature difference provides only one expression (instead of two different expressions) for either stream which is a measure of both thermal and temperature effectiveness of the particular stream. Differences between the conventional and proposed effectiveness values are presented as functions of the capacity ratio and NTU. These data are used to demonstrate the advantages of the new definitions for maximum heat transfer and maximum temperature difference in ideal two-fluid heat exchangers.

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A SIMPLE MATHEMATICAL MODEL TO PREDICT HEAT PIPE MAXIMUM HEAT TRANSFER, EQUIVALENT THERMAL CONDUCTIVITY, AND THERMAL RESISTANCE

Heat Pipe Science and Technology An International Journal ◽

10.1615/heatpipescietech.2016017223 ◽

2016 ◽

Vol 7 (1-2) ◽

pp. 45-55

Author(s):

Masataka Mochizuki ◽

Thang Nguyen ◽

Yuji Saito ◽

Tien Nguyen ◽

Vijit Wuttijumnong

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Mathematical Model ◽

Thermal Resistance ◽

Heat Pipe ◽

Simple Mathematical Model ◽

Equivalent Thermal Conductivity ◽

Maximum Heat ◽

Maximum Heat Transfer

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Significance of Shape Factor in Heat Transfer Performance of Molybdenum-Disulfide Nanofluid in Multiple Flow Situations; A Comparative Fractional Study

Molecules ◽

10.3390/molecules26123711 ◽

2021 ◽

Vol 26 (12) ◽

pp. 3711

Author(s):

Asifa ◽

Talha Anwar ◽

Poom Kumam ◽

Zahir Shah ◽

Kanokwan Sitthithakerngkiet

Keyword(s):

Heat Transfer ◽

Skin Friction ◽

Molybdenum Disulfide ◽

Heat Transfer Rate ◽

Shape Factor ◽

Transfer Rate ◽

Maximum Heat ◽

Left Wall ◽

Maximum Heat Transfer ◽

Mos2 Nanoparticles

In this modern era, nanofluids are considered one of the advanced kinds of heat transferring fluids due to their enhanced thermal features. The present study is conducted to investigate that how the suspension of molybdenum-disulfide (MoS2) nanoparticles boosts the thermal performance of a Casson-type fluid. Sodium alginate (NaAlg) based nanofluid is contained inside a vertical channel of width d and it exhibits a flow due to the movement of the left wall. The walls are nested in a permeable medium, and a uniform magnetic field and radiation flux are also involved in determining flow patterns and thermal behavior of the nanofluid. Depending on velocity boundary conditions, the flow phenomenon is examined for three different situations. To evaluate the influence of shape factor, MoS2 nanoparticles of blade, cylinder, platelet, and brick shapes are considered. The mathematical modeling is performed in the form of non-integer order operators, and a double fractional analysis is carried out by separately solving Caputo-Fabrizio and Atangana-Baleanu operators based fractional models. The system of coupled PDEs is converted to ODEs by operating the Laplace transformation, and Zakian’s algorithm is applied to approximate the Laplace inversion numerically. The solutions of flow and energy equations are presented in terms of graphical illustrations and tables to discuss important physical aspects of the observed problem. Moreover, a detailed inspection on shear stress and Nusselt number is carried out to get a deep insight into skin friction and heat transfer mechanisms. It is analyzed that the suspension of MoS2 nanoparticles leads to ameliorating the heat transfer rate up to 9.5%. To serve the purpose of achieving maximum heat transfer rate and reduced skin friction, the Atangana-Baleanu operator based fractional model is more effective. Furthermore, it is perceived that velocity and energy functions of the nanofluid exhibit significant variations because of the different shapes of nanoparticles.

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Effect of liquid cooling on PCR performance with the parametric study of cross-section shapes of microchannels

Scientific Reports ◽

10.1038/s41598-021-95446-0 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Yousef Alihosseini ◽

Mohammad Reza Azaddel ◽

Sahel Moslemi ◽

Mehdi Mohammadi ◽

Ali Pormohammad ◽

...

Keyword(s):

Heat Transfer ◽

Cross Section ◽

Cross Sections ◽

Heat Sink ◽

Evaluation Criteria ◽

Circular Cross Section ◽

Microchannel Heat Sink ◽

Liquid Cooling ◽

Maximum Heat ◽

Maximum Heat Transfer

AbstractIn recent years, PCR-based methods as a rapid and high accurate technique in the industry and medical fields have been expanded rapidly. Where we are faced with the COVID-19 pandemic, the necessity of a rapid diagnosis has felt more than ever. In the current interdisciplinary study, we have proposed, developed, and characterized a state-of-the-art liquid cooling design to accelerate the PCR procedure. A numerical simulation approach is utilized to evaluate 15 different cross-sections of the microchannel heat sink and select the best shape to achieve this goal. Also, crucial heat sink parameters are characterized, e.g., heat transfer coefficient, pressure drop, performance evaluation criteria, and fluid flow. The achieved result showed that the circular cross-section is the most efficient shape for the microchannel heat sink, which has a maximum heat transfer enhancement of 25% compared to the square shape at the Reynolds number of 1150. In the next phase of the study, the circular cross-section microchannel is located below the PCR device to evaluate the cooling rate of the PCR. Also, the results demonstrate that it takes 16.5 s to cool saliva samples in the PCR well, which saves up to 157.5 s for the whole amplification procedure compared to the conventional air fans. Another advantage of using the microchannel heat sink is that it takes up a little space compared to other common cooling methods.

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Dimensionless Correlations for Natural Convection Heat Transfer from a Pair of Vertical Staggered Plates Suspended in Free Air

Applied Sciences ◽

10.3390/app11146511 ◽

2021 ◽

Vol 11 (14) ◽

pp. 6511

Author(s):

Alessandro Quintino ◽

Marta Cianfrini ◽

Ivano Petracci ◽

Vincenzo Andrea Spena ◽

Massimo Corcione

Keyword(s):

Heat Transfer ◽

Rayleigh Number ◽

Convection Heat Transfer ◽

Separation Distance ◽

Vertical Alignment ◽

Maximum Heat ◽

Plate Length ◽

Optimal Separation ◽

Maximum Heat Transfer ◽

Free Air

Buoyancy-induced convection from a pair of staggered heated vertical plates suspended in free air is studied numerically with the main scope to investigate the basic heat and momentum transfer features and to determine in what measure any independent variable affects the thermal performance of each plate and both plates. A computational code based on the SIMPLE-C algorithm for pressure-velocity coupling is used to solve the system of the governing conservation equations of mass, momentum and energy. Numerical simulations are carried out for different values of the Rayleigh number based on the plate length, as well as of the horizontal separation distance between the plates and their vertical alignment, which are both normalized by the plate length. It is observed that an optimal separation distance between the plates for the maximum heat transfer rate related to the Rayleigh number and the vertical alignment of the plates does exist. Based on the results obtained, suitable dimensionless heat transfer correlations are developed for each plate and for the entire system.

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Heat Transfer in Separated, Reattached, and Redevelopment Regions Behind a Double Step at Entrance to a Flat Duct

Journal of Heat Transfer ◽

10.1115/1.3614343 ◽

1967 ◽

Vol 89 (2) ◽

pp. 163-167 ◽

Cited By ~ 27

Author(s):

E. G. Filetti ◽

W. M. Kays

Keyword(s):

Heat Transfer ◽

Local Heat Transfer ◽

Reynolds Numbers ◽

Local Heat ◽

Duct Flow ◽

Double Step ◽

Maximum Heat ◽

Transfer Rates ◽

Maximum Heat Transfer ◽

Flow Cross

Experimental data are presented for local heat transfer rates near the entrance to a flat duct in which there is an abrupt symmetrical enlargement in flow cross section. Two enlargement area ratios are considered, and Reynolds numbers, based on duct hydraulic diameter, varied from 70,000 to 205,000. It is found that such a flow is characterized by a long stall on one side and a short stall on the other. Maximum heat transfer occurs in both cases at the point of reattachment, followed by a decay toward the values for fully developed duct flow. Empirical equations are given for the Nusselt number at the reattachment point, correlated as functions of duct Reynolds number and enlargement ratio.

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