Optimization Of Heat Exchanger Research Articles

Multi-objective optimization of elliptical tube fin heat exchangers based on neural networks and genetic algorithm

The application of machine learning based on neural networks (NNs) and genetic algorithm (GA) in multi-objective optimization of heat exchangers is studied. Taking the tube fin heat exchanger (TFHE) as the research object, the inlet air velocity and the ellipticity of tubes are taken as the optimization variables. In order to obtain the optimal heat transfer performance and pressure drop performance, Computational Fluid Dynamics (CFD) simulation is carried out for different Reynolds based on the hydraulic diameter numbers (150–750) and tube ellipticity (0.2–1). Then use simulation data to train the Back-Propagation neural networks and establish the prediction model of heat transfer coefficient and pressure drop. The non-dominated multi-objective genetic algorithm with elitist retention strategy (NSGA-II) is used to optimize two prediction results of NNs. Finally, the optimal heat transfer coefficient and pressure drop are given in the form of Pareto front. The optimization results show that when the Reynolds number is 541 and the ellipticity is 0.34, the pressure drop of the TFHE decreases 20%, and the heat transfer coefficient is basically unchanged, whose j/f is 1.28 times as much as that of the original heat exchanger.

Multi-objective optimization of a tubular heat exchanger enhanced with delta winglet vortex generator and nanofluid using a hybrid CFD-SVR method

The present study improves the thermal-hydraulic performance of a circular tube equipped with a delta winglet vortex generator by providing a numerical model, investigating the effect of two additional parameters, and developing a support vector regression (SVR) for prediction and optimization. The additional parameters are the angle of attack and SiO2 concentration, while the data on the variation of thermohydraulic parameters with pitch and blockage is already available in the literature. The boundary layer disruption and swirling flow caused by the delta winglet result in heat transfer enhancement. The presence of such inserts also increases the pressure drop in the heat exchanger. The nanofluid further enhances heat transfer by boosting the thermophysical properties of the fluid. The hybrid method, CFD-SVR, is carried out for turbulent water flow at Reynolds numbers ranging from 4200 to 16200. The delta winglets are in pair arrangement with ten angles of attack from 25∘ to 70∘ with 5∘ increments. The addition of SiO2 with volumetric concentrations varies from φ=0 to 0.5% has been explored. The diameter of the tube (D) is 50 mm, while the pitch ratio (P/D) and blockage ratio (B/D) vary from 1 to 3 and 0.1 to 0.2, respectively. Finally, the data of this study and the previously published experimental data were fed into an SVR to find the best possible arrangement of delta winglet for a tubular heat exchanger. The highest achieved thermal enhancement factor (TEF) was found to be 2.18 with α = 25°, PR = 0.83, BR = 0.13, and φ = 0.5% at the least Re number.

Thermohydraulic experiments on a supercritical carbon dioxide–air microtube heat exchanger

Heat exchangers are critical components in supercritical CO2 Brayton cycles and provide necessary heat input, recovery, and dissipation. Tubular heat exchangers with unconventionally small tube sizes (tube diameters less than 5 mm) are promising components for supercritical CO2 cycles and potentially provide excellent structural stability with wide scope of application. This paper provides essential design and fabrication guidelines for a compact shell-and-tube heat exchanger with microtubes (with an inner diameter equal to 1.75 mm). A heat exchanger test rig is used to evaluate the thermohydraulic performance of this heat exchanger with supercritical CO2 and air as working fluids. Thermohydraulic data are reported for more than forty sets of experiments with varying Reynolds numbers for shell and tube flows. Critical performance metrics are calculated from the data and compared with predictions from a previously described numerical model. The average deviations between the experimental and model results fall within 10% for all critical metrics. This excellent agreement validates the numerical model for supercritical CO2 heat exchanger optimization and scale-up.

Energy, exergy, economy analysis and geometry optimization of spiral coil heat exchangers

The present investigation deals with the exergy and exergoeconomic study of a heat exchanger with a shell and spiral tube, considering different geometries. The Realizable k-ε turbulent model is employed to simulate the heat exchanger and irreversibility calculation in the shell and spiral tube. The numerical results in this study are validated through experimental data from previous research. The influences of the different geometrical parameters on purchased equipment cost, heat exchanger irreversibility as well as efficiency of the second law are investigated. These parameters include the coil pitch, the minimum radius of the spiral, coil radius, shell thickness, and shell radius. It is realized that heat transfer is the primary source of exergy destruction. Increasing coil pitch from 20 to 40 mm results in a reduction of, on average, 4% of the second law efficiency of the heat exchanger and 3.54% increase in purchased equipment cost value. Similarly, increasing the coil radius comes up with a reduction by about 19% of the heat exchanger efficiency. Moreover, investigating the influence of studied geometrical parameters on purchased equipment cost reveal that the most and least effective geometrical parameters are coil radius and minimum radius of spiral, respectively.

Enhancing flow structure in heat exchangers analysis of dynamic and thermal air-flow behavior with perforated and inclined baffles

This paper presents a comprehensive analysis of the dynamic and thermal behavior of air-flow within a heat exchanger equipped with two distinctive baffles: a perforated baffle and a partially inclined baffle. The influence of hole positioning in the perforated baffle on the overall performance of the heat exchanger is thoroughly investigated through a systematic examination of temperature curves at varying Reynolds number values. The results demonstrate significant enhancements in flow characteristics attributed to the presence of these baffles. The flow structure exhibits prominent main currents across the gaps and secondary currents through the holes. The inclusion of these barriers leads to significant deformations and the emergence of well-developed recycling cells in the form of vortices. Both the perforated and inclined baffles effectively reduce pressure values on their frontal regions, thereby mitigating friction losses. Furthermore, the introduction of a perforation in the lower part of the baffle induces a more turbulent flow compared to the other cases. This is attributed to the expansion of the recirculating cells, resulting in improved fluid mixing and subsequent enhancement of thermal energy gain. These findings offer valuable insights into the design and optimization of heat exchangers, enabling improved performance and efficiency in various engineering applications.

Fluid Flow and Mixed Heat Transfer in a Horizontal Channel with an Open Cavity and Wavy Wall

Heat exchangers are utilized extensively in different industries and technologies. Consequently, optimizing heat exchangers has been a major concern among researchers. Although various studies have been conducted to improve the heat transfer rate, the use of a wavy wall in the presence of different types of heat transfer mechanisms has not been investigated. This study thus investigates the mixed heat transmission behavior of fluid in a horizontal channel with a cavity and a hot, wavy wall. The fluid flow in the channel is considered laminar, and the governing equations including continuity, momentum, and energy are all solved numerically. The numerical solution is stabilized by using a first-order multi-dimensional characteristic-based scheme in combination with a fifth-order Runge-Kutta method. The flow and heat transfer effects of varying Richardson numbers, Reynolds numbers, wave amplitude, wavelength, channel height, and cavity width are examined. The results indicate that the mean Nusselt number increases with an increase in Reynolds number, wave amplitude, and cavity width, while it decreases with an increase in Richardson number, wavelength, and channel height. The minimum Nusselt number is calculated to be 0.7, whereas the maximum Nusselt number is 27.09. The Nusselt number has only increased by 40% in the higher depths of the cavity, despite the Richardson number being 10,000 times larger. But this figure increases to 130% at lower depths. The mean Nusselt number is thus significantly influenced by channel height and cavity width. The influence of wave amplitude on the mean Nusselt number is twice that of wavelength.

SENSITIVITY ANALYSIS AND OPTIMIZATION OF WAVY FIN CIRCULAR TUBE HEAT EXCHANGER

The present study shows the strong ability of a genetic algorithm (GA) in the thermal design and optimization of a herringbone wavy fin and circular tube compact heat exchanger (FTHE). The influences of various design parameters on friction factor, Colburn factor, and minimum total annual cost (TAC) are presented. Mainly, three design objectives are considered, such as minimum friction factor, maximum Colburn factor, and minimum TAC. For optimization, the Optimization toolbox of Matlab is used. In the GA routine, tournament selection, single point crossover, and constraint dependent mutation are adopted. The multiobjective optimization reveals a couple of sets of optimal solutions by optimizing the two objectives, i.e., minimum friction factor and maximum Colburn factor. By minimizing the TAC, a significant amount of cost is found to be reduced as compared to previous works in the literature with some optimum geometrical parameters.

Optimization of wickless heat pipe heat exchanger using R1234-yf and ethanol as working fluids

Optimization of wickless heat pipe heat exchanger using R1234-yf and ethanol as working fluids

Shell-side flow study and structural optimization of a double helical-like flow heat exchanger

A double helical-like flow heat exchanger model was built, its shell-side flow state was studied by the CFD method, and the difference in heat transfer performance between it and the torsional flow heat exchanger was compared. From the numer?ical simulation results, it is found that the heat transfer coefficient and pressure drop are improved by 7.07-8.93% and 15.50-18.22%, respectively at the same flow rate, and the comprehensive performance expressed as Nu/f 1/3 is improved by 21.84-24.08%. Using the orthogonal test method to optimize the shell-side struc?ture, it is found that the comprehensive performance is influenced by the two factors of spacing/groups and angle of baffles, and the influence of the deflection angle of two adjacent groups of baffles is very small, and the optimal structural combi-nation of comprehensive performance is 30-0-70/11 (the angle of baffles is 30?, the deflection angle of two adjacent groups of baffles is 0?, the spacing between two adjacent sets of baffles is 70 mm, and the number of baffle groups is 11). The reliability and feasibility of the simulation method were verified by experiments.

Numerical and experimental performance investigation of a heat exchanger designed using topologically optimized fins

Topology optimization for thermal-fluid problems has been successfully used to improve performance of small structures used for heat transfer. Optimization of full heat exchangers, due to analysis method limitations and computational costs, has not been able to produce manufacturable designs complex enough to satisfy heat exchanger specifications. The goal of this study is determining if a practical heat exchanger design can be obtained by the use of topology optimization. By considering a plate-fin heat exchanger, topology optimization is used to obtain a locally optimized fin pattern which is extended to form a heat exchanger core. A modification of the Number of transfer units method is presented to deal with the unique topology obtained by optimization and evaluate the performance of the exchanger. The performance, when compared to traditional serrated fin designs, show that optimization improvements extend beyond the optimized region onto the entire exchanger. The results show that the optimized design is an improvement outside optimization flow parameters. However, the limitations in 3D printer technology result in slight deviation of experiment results compared to the analysis, and prevent the manufacturing of designs with comparable total performance values to heat exchangers manufactured through traditional methods. • Design procedure obtains a heat exchanger core by localized topology optimization. • NTU method is modified to evaluate results of topology optimization. • Modified NTU, CFD and experimental evaluations are in good agreement with each other. • Performance improvements are maintained outside optimization flow parameters.

Methods of Simplifying Optimal Control Problems, Heat Exchange and Parametric Control of Oscillators

Methods of simplifying optimal control problems by decreasing the dimension of the space of states are considered. For this purpose, transition to new phase coordinates or conversion of the phase coordinates to the class of controls is used. The problems of heat exchange and parametric control of oscillators are given as examples: braking/swinging of a pendulum by changing the length of suspension and variation of the energy of molecules’ oscillations in the crystal lattice by changing the state of the medium (exposure to laser radiation). The last problem corresponds to changes in the temperature of the crystal.

Aerodynamic Shape Optimization of Heat Exchangers

Aerodynamic Shape Optimization of Heat Exchangers

MODELS AND METHODS FOR IMPROVING THE OPERATION OF THE ENERGY FACILITY CONTROL SYSTEM

This article is devoted to improving methods and models for a computer-integrated control system (CICS) that monitors the wear of heat exchange surfaces of pipes in steam boilers at coal-fired thermal power stations (TPP), in particular for coal with unknown abrasive composition. The system uses real-time coal quality data to 1manage the abrasive, optimize coal distribution, and verify coal quality to reduce costs. It is described that the difficulties faced by the global coal industry are related to quality, price and environmental issues, and the transition to sustainable energy is complicated by this diversity. Efficient power generation depends on accurate identification of fuel composition and minimizing damage from abrasive impurities in the fuel of heat exchangers. Despite the existing analytical methods, there is a need for improved diagnostic technology, which involves the integration of automated systems to improve efficiency and sustainability. The paper presents a mathematical model that calculates the effect of different types of coal and impurities on the wear of heat exchange tubes, maximizing service life and minimizing costs. It includes a Cochran sampling rule to improve coal quality control. An automated coal quality management method was also developed to reduce wear from abrasive coal impurities. It includes a stepwise supplier selection and stock utilization method, enhancing wear control using the Cochran stepwise sampling method. In addition, a fuzzy logic-based control device distributes the flow in such a way as to ensure satisfactory coal quality, emphasizing the need for continuous system monitoring. A model-based CICS has been developed that controls coal flow based on real-time impurity identification, resulting in significant cost savings and extended overhaul intervals. Computational experiments confirm that the CICS can more than double the service life of heat exchange tubes by maintaining a satisfactory thickness, thereby postponing repairs and reducing operating costs. Overall, this article presents a comprehensive approach to managing and optimizing heat exchanger tube wear at TPP using modelling, real-time data analysis, and automated control systems to improve efficiency and sustainability.

Determination of the optimal heat exchanger configuration for wastewater heat recovery

The work aims to increase the efficiency of the hot water supply system based on local recovery of the heat of wastewater generated in the shower room for preheating cold water. The work uses mathematical modeling of the thermal operation of the heat exchanger under study. Physical modeling of the heat exchange process between media flows in a heat exchanger was carried out (experimental test). Temperatures of media flows were measured. The temperature distribution inside media flows was compared experimentally with data obtained analytically. In conclusion, an analysis and generalization of the results obtained is made. The result of the research was a designed recovery heat exchanger. Data were obtained on the thermal inertia of the device, i.e., about the required time for the device to achieve a stationary thermal regime from the moment it is turned on. Data were obtained on the potential energy effect from introducing a recovery heat exchanger, taking into account its thermal inertia. The number of showers required to pay off the heat exchanger was calculated. Data were obtained on the influence of changes in the geometric and operating parameters of the heat exchanger on the efficiency of wastewater thermal energy utilization. A methodology for designing a heat exchanger for specific operating conditions was developed. The developed method for designing a recovery heat exchanger allows one to determine the optimal configuration of the device under particular operating conditions and mode of use of the heat exchanger, taking into account its thermal inertia. It is planned to continue the work by assessing the energy and economic effect of using local wastewater heat recovery within the heat supply system of a separate settlement/region.

Performance optimization of a thermoelectric generator for automotive application using an improved whale optimization algorithm

A TEG system using a low-backpressure polyhedral heat exchanger is optimized with an improved whale optimization algorithm (IWOA), which balances the output performance and backpressure and provides a new vision to heat exchanger optimization.

Design optimization of cross-counter flow compact heat exchanger for energy recovery ventilator

Energy recovery ventilators (ERVs) are the key equipment to fresh air ventilation, which is helpful for the control of respiratory diseases like COVID-19. In this paper, design optimization of the compact heat exchanger in a proposed heat recovery ventilator of the energy efficient building has been carried out and discussed. Appropriate theoretical models are required to evaluate system performance and potential energy savings. This is challenging because of the complexity of the preferred module combining cross- and counter-flow regions. The objective of the design optimization is to maximize the heat transfer effectiveness and to minimize the pressure loss of the compact heat exchanger with limited space. In this study, the allowable dimensions, heat transfer specifications and design requirements of the proposed heat exchanger are firstly defined. Then, the flow configuration, numbers, and dimensions of the air flow channels inside the heat exchanger are identified as the design parameters. A systematic design and optimization method for heat exchanger effectiveness improvement is explored. Furthermore, a detailed mathematical modeling is conducted and validated against the experimental results using the effectiveness-NTU method. It is found that the proposed modeling method is expected to be used to design of the compact heat exchanger. Finally, guidelines for improving the heat transfer effectiveness of air-to-air heat recovery ventilator were derived.

Heat transfer characteristics of a water heater operating on natural gas and cofiring with pulverized rumen contents

This study discusses the heat exchange optimization of a 450 kW water heater operating with natural gas (NG) and in cofiring mode burning solid pulverized rumen and NG. The rumen material is a byproduct from cattle slaughter processes, consisting of the waste contained in the cow stomachs and intestines. In NG mode, the gaseous fuel provides 100% of the heat input, and in cofiring mode 50% of the heat rate input is obtained from the rumen contents and NG balances the heat rate. The paper presents experimental analysis on a scaled prototype of 45 kW, and the results are complemented with CFD analysis of the aerothermochemistry of the combustion chamber and heat exchanger. The heterogeneous reactions are stabilized using a low swirl injector. The optimization seeks to use swirling flows inside the combustion chamber to improve convective heat transfer from the combustion products to the water-cooled surfaces, and the use of decaying swirl generators to enhance heat transfer at the second and third gas passes. The geometry variations attain effectiveness above 86%, with low emissions CO, THC and NOx, and to attain reaction stability of the rumen biowastes.

A generic algorithm-based application for pinch-exergy prediction in process industries: A case study

In the industrial sector, efficient production and optimal use of thermal energy are primary concerns for managers and engineers. Considerable research has been devoted to improving and promoting thermal energy efficiency, especially energy recovery in the context of sustainability. Pinch analysis is one of the most powerful methods in this regard. To maximise the energy recovery (MER), the pinch method is well-established in designing an optimal heat exchange network (HEN). Exergy analysis is combined with the pinch method to minimise the work potential loss (exergy loss) while ensuring maximum heat recovery. This study presents a generic algorithm built using Python language to predict and quantify energy and exergy targets in industrial processes. It provides a framework to guide experts and planners in efficiently using the combined analysis tools. The generic algorithm is based on advanced numerical and graphical tools. It provides exergy problem table algorithm (Ex–PTA) and grand composite curve (EHR and HRP) tools. For Δ T min = 10°C, the generic algorithm is implemented in a building complex case study. The energy targets for heating and cooling requirements are 316.2625 kW and 0 kW, respectively. The obtained exergy targets are less attractive given an improvement from advanced utility integration; this is due to the treated system (medium-temperature system) and not to the reliability and efficiency of the generic algorithm. To evaluate the generic algorithm calculations, they are executed in a low-temperature process in which pinch exergy analysis (PExA) has already been performed. The simulated and generated results are identical, demonstrating the reliability and effectiveness of the developed generic algorithm.

Parametric optimization of a spiral ground heat exchanger by response surface methodology and multi-objective genetic algorithm

Horizontal spiral-coil type ground heat exchanger (HSGHE) has been increasingly used in ground source heat pump systems owing to its high heat transfer performance and low cost. This study proposes a method to optimize the design and operation parameters based on the combination of response surface methodology (RSM) and multi-objective genetic algorithm (MOGA). First, a 3D numerical model simulating the thermal–hydraulic characteristics of the HSGHE was built and the reliability of the model was validated through an indoor test rig. Subsequently, some parametric studies were performed to analyze the degree of influences that each input parameter on the outputs. On this basis, the Box-Behnken design method and RSM were used to establish response surface models between the input parameters (spiral diameter, pitch, and fluid velocity) and objective functions (net heat exchange rate and thermal performance capability) and determined the interactions between them. The results showed that the spiral diameter had the most significant influence, followed by the pitch, and fluid velocity. Finally, based on the developed models, the MOGA employing the Pareto optimum solutions were used to optimize the design and operation parameters and determine their optimal combination: spiral diameter of 0.4 m, pitch of 0.1 m, and fluid velocity of 0.4 m/s. The findings of this study may assist designers in the development of high efficiency ground heat exchangers.

Multi-objective optimization of plate heat exchanger for commercial electric vehicle based on genetic algorithm

Plate heat exchanger (PHE) has been extensively utilized in cooling systems of commercial electric vehicles (CEVs). To enhance comprehensive performance, it is crucial to optimize the structural configuration of PHE. In this paper, a simplified model of the PHE from a CEV was numerically analyzed for thermal-hydraulic performance and verified by experimental data. After that, a multi-objective genetic algorithm optimization (MOGAO), where -j and f factors were set as objective functions, was implemented for its optimal structural configuration, and JF factor was proposed to assist the result selection. Finally, Optimization model 1 (OM1) was numerically compared with the original model under j, f, and JF factors to confirm enhancement. It is found that the simulation results could fit experimental data well within a reasonable error range. Among all the optimization results, OM1 owns the better JF factor. Compared with the original model, OM1 presents a higher average velocity and outlet temperature on the cold side. In detail, OM1 discovers the better comprehensive performance with a f decrement of 42.08%, j and JF increments of 5.02% and 21.53%, respectively.