Showing papers in "International Journal of Heat and Mass Transfer in 2019"
TL;DR: In this article, the authors focus on the application of various phase change materials based on their thermophysical properties, in particular, the melting point, thermal energy storage density and thermal conductivity of the organic, inorganic and eutectic phases.
Abstract: In order to overcome the increasing demand–supply energy gap due to the rapid urbanization, labor productivity, consumerism and depletion of fossil fuel resources, there is a need for the development of technologies with renewable energy sources. Phase change materials are one of the most appropriate materials for effective utilization of thermal energy from the renewable energy resources. As evident from the literature, development of phase change materials is one of the most active research fields for thermal energy storage with higher efficiency. This review focuses on the application of various phase change materials based on their thermophysical properties. In particular, the melting point, thermal energy storage density and thermal conductivity of the organic, inorganic and eutectic phase change materials are the major selection criteria for various thermal energy storage applications with a wider operating temperature range. The strategy adopted in improving the thermal energy storage characteristics of the phase change materials through encapsulation as well as nanomaterials additives, are discussed in detail. Specifically, the future research trends in the encapsulation and nanomaterials are also highlighted.
813 citations
TL;DR: In this article, the variation of energy storage efficiency, Finite element method has been employed to show the variation in energy storage energy efficiency, important selected parameters are nanofluid concentration, angle of V shaped fin, copper oxide particle size and length of fin.
Abstract: Thermal storage unit can be utilized to satisfy the balance of energy supply and demand. Copper oxide nanoparticles and V shaped fins are involved in storage unit in current research to expedite the solidification. To show the variation of energy storage efficiency, Finite element method has been employed. Important selected parameters are nanofluid concentration, angle of V shaped fin, copper oxide particle size and length of fins. Contours and profiles in various time steps are depicted. Outputs display that discharging rate augments with rise of angle of V shaped fin. Using copper oxide helps solidification. Length of fin has inverse relationship with discharging rate.
407 citations
TL;DR: In this paper, a comprehensive review of published articles addressing passive enhancement of pool boiling using surface modification techniques is provided, including macroscale, microscale, and nanoscale surfaces, as well as multiscale (hybrid-scale), and hybrid-wettability techniques.
Abstract: This paper provides a comprehensive review of published articles addressing passive enhancement of pool boiling using surface modification techniques They include macroscale, microscale, and nanoscale surfaces, as well as multiscale (hybrid-scale), and hybrid-wettability techniques Different enhancement methods are assessed in terms of underlying fluid routing mechanisms and ability to achieve three distinct heat transfer goals: eliminating incipient boiling hysteresis, increasing nucleate boiling heat transfer coefficient, and ameliorating critical heat flux (CHF), especially for inert dielectric coolants that are both highly wetting and possess relatively poor thermophysical properties While different enhancement scales are shown to provide different degrees of success in achieving the three goals, it is shown that both microscale and nanoscale surface features are susceptible to blockage, resulting in deterioration of the enhancement over time This review also points to scarcity of sufficiently sized databases for a given enhancement scheme in terms of fluid type, surface material, size, and orientation, enhancement shape, pattern, and scale, and operating pressure This renders available findings less-than-adequate tools for design of practical cooling systems
343 citations
TL;DR: In this paper, the effect of porosity and pore density on heat transfer, thermal conductivity, specific heat, latent heat and charging/discharging time are critically reviewed.
Abstract: Phase change material (PCM) is promising media for thermal energy storage owing to its extensive value of latent heat (140–970 KJ/Kg). However, thermal conductivity of PCMs is too low which obstructs energy storage and retrieval rate. In recent days, thermally enhanced PCMs are considered promising materials for efficient heat transfer in many applications. This article designates the review on improved thermal properties and heat transfer of PCMs by using porous materials. Enhanced heat transfer of PCMs can be achieved using extended surfaces (triangular, conical, square, and rectangular fins), heat pipes, and addition of highly conductive nanoparticles (e.g. Cu, Al2O3, Au, SiC, SiO2 and TiO2). Major focus of this article is to study the enhanced heat transfer of PCMs through metallic (copper, nickel, and aluminum) and carbon based (carbon, graphite and expanded graphite) porous materials/foams. Effects of porosity and pore density on heat transfer, thermal conductivity, specific heat, latent heat and charging/discharging time are critically reviewed. Porous materials/foams are reported to be efficient for heat transfer/thermal conductivity enhancement by 3–500 times. Furthermore, correlations to find the effective thermal conductivity of PCM/foam are reported. Important applications of PCM/foam reported by different researchers are also discussed in this paper. Finally, conclusions and recommendations are presented to highlight the research gap in this area.
336 citations
TL;DR: In this article, the impact of using fins and nano-sized materials on performance of discharging system was investigated, and the mathematical model has been offered in the form of PDE's, which were solved using Galerkin FEM.
Abstract: The current article investigates the impact of using fins and nano sized materials on performance of discharging system. Various shapes for nanoparticle have been considered. Cold fluid flows in both inner and outer layers and middle layer is full of PCM. To make a careful choice of designing heat storage based on uniform solidification, two factor has been examined; length of fins and shape factor. Temperature and solid fraction distributions were reported at various time steps. The homogeneous model for nanofluid has been extended by incorporating various shapes of CuO nanoparticles. The mathematical model has been offered in the form of PDE's, which were solved using Galerkin FEM. It can be observed that the employing nanofluid augments the discharging rate and best performance is obtained for platelet shape.
336 citations
TL;DR: In this paper, a combined turbulator was proposed to achieve good thermal performance, in which the height of turbulator (b) has been selected and its variation as well as Reynolds number was demonstrated in outputs.
Abstract: In this research, combined turbulator was proposed to achieve good thermal performance. Steady turbulent flow of copper oxide nanofluid with homogeneous model was simulated involving k-ɛ model. Among various geometric parameters, height of turbulator (b) has been selected and its variation as well as Reynolds number was demonstrated in outputs. Exergy loss as well as flow and heat transfer was analyzed. Augmenting b is capable of increasing heat transfer. More disturbances can be seen with augmenting inlet velocity. Exergy loss is inversely proportional to increase of pumping power.
259 citations
TL;DR: In this article, the authors present the outputs for nano-refrigerant (R600a/oil/CuO) boiling heat transfer within flattened channels utilizing experimental method The influence of flattened percentage, flow rate, vapor quality as well as the mass fraction of CuO on boiling heat Transfer (h) were discussed Outcomes reveal that increasing the flattened percentage enhances the h Also, within the ranges of present experiment, h augments by increasing nanoparticle's concentration.
Abstract: This research presents the outputs for nano-refrigerant (R600a/oil/CuO) boiling heat transfer within flattened channels utilizing experimental method The influence of flattened percentage, flow rate, vapor quality as well as the mass fraction of CuO on boiling heat transfer (h) were discussed Outcomes reveal that increasing the flattened percentage enhances the h Also, within the ranges of present experiment, h augments by increasing nanoparticle’s concentration
257 citations
TL;DR: In this article, a double twisted tape was inserted in a H2O pipe to help its conductivity and a finite volume method was used to describe the flow and energy balance.
Abstract: In current modeling, turbulent heat transfer of homogeneous nanofluid due to inserting double twisted tapes has been carried out. To better describing performance of unit, generation of entropy has been examined. CuO nanomaterial has been dispersed in to H2O, to help its conductivity. The pipe was under the impact of uniform heat flux. Equations describing the flow and energy balance were solved applying finite volume method. The simulations illustrate that both augmenting pumping power and height of tape result in the reduction of thermal component and the augmentation of frictional component.
250 citations
TL;DR: In this paper, the authors studied free convective flow and heat transfer of a suspension of nano-encapsulated phase change materials (NEPCMs) in an enclosure and found that the enhancement of heat transfer is highly dependent on the non-dimensional fusion temperature, θf, and very good performance can be achieved in the range of ¼ < θ f < 0.
Abstract: Free convective flow and heat transfer of a suspension of Nano Encapsulated Phase Change Materials (NEPCMs) in an enclosure is studied. NEPCM particles are core-shell structured with Phase Change Material (PCM) as the core. The enclosure is a square cavity with top and bottom insulated walls and differentially-heated isothermal vertical walls. The NEPCM particles circulate under natural convection inside the cavity. The PCM cores undergo phase change from solid to liquid and absorb some of the surrounding’s heat in the form of latent heat in the hot region, and release the absorbed heat in the cold region by solidification. The governing equations representing the conservation of mass, flow, and heat of NEPCM suspension are introduced in the form of partial differential equations. The governing equations are transformed into non-dimensional form and solved by the finite element method. A grid check and validation test are performed to ensure the accuracy of the results. The outcomes show that the fusion temperature of NEPCM particles is the key factor affecting the heat transfer enhancement of NEPCMs in the natural convection flow. The enhancement of heat transfer is highly dependent on the non-dimensional fusion temperature, θf, and very good performance can be achieved in the range of ¼ < θf < ¾. Comparing to the base fluid, a relative enhancement of about 10% can be achieved by using NEPCMs at a non-dimensional fusion temperature of ¼.
240 citations
TL;DR: In this paper, the unsteady flow and heat transfer past a stretching/shrinking sheet in a hybrid nanofluid is studied, and the governing equations of the problem are transformed to the similarity equations by using similarity transformation technique.
Abstract: The unsteady flow and heat transfer past a stretching/shrinking sheet in a hybrid nanofluid is studied. The governing equations of the problem are transformed to the similarity equations by using similarity transformation technique. The problem is solved numerically using the boundary value problem solver (bvp4c) in Matlab software. The plots of the skin friction coefficient and the local Nusselt number as well as the velocity and temperature profiles for selected parameters are presented. It is found that dual solutions exist for a certain range of the unsteadiness parameter. A temporal stability analysis is performed to determine the stability of the dual solutions in a long run, and it is reveals that only one of them is stable while the other is unstable.
219 citations
TL;DR: A review of the major studies on the hybrid heat transfer enhancement techniques can be found in this paper, where it was found that best enhancement is achieved via the hybrid application of the heat pipe with fins or metal foam.
Abstract: The potential of phase-change materials (PCMs) for application in the fields of thermal energy storage and thermal management is well recognized, due to their remarkable energy storage density and negligible temperature variation during operation. However, these materials do face the primary challenge of low thermal conductivity which necessitates incorporation of heat transfer enhancement techniques. Heat transfer enhancement in these systems has been a subject of interest for numerous studies, many of which have focused on employing only one enhancement technique. Very few studies have investigated the combination of two or more techniques. This combination of techniques is referred to as hybrid heat transfer enhancement. This paper provides a review of the major studies on the hybrid heat transfer enhancement techniques. It was found from the study that best enhancement is achieved via the hybrid application of the heat pipe with fins or metal foam. It was also found that the hybrid use of nanoparticles with fins or metal foam is more efficient than the use of nanoparticles alone within the same containment volume. Further research is recommended to explore other possible hybrid enhancement techniques which could lead to improved performance of PCM-based systems.
TL;DR: In this paper, the exothermic reactions model with constant heat source in the porous media with strong memory effects is considered and the mathematical equation of the problem is confined in a fractional energy balance equation (FEBE), which furnishes the temperature portrayal in conduction state having uniform heat source on steady state.
Abstract: The present article deals with the exothermic reactions model having constant heat source in the porous media with strong memory effects. The Caputo, Caputo-Fabrizio and Atangana-Baleanu fractional operators are used to induce memory effects in the mathematical modeling of exothermic reactions. The patterns of heat flow profiles are very essential for heat transfer in every kind of the thermal insulation. In the present investigation, we focus on the driving force problem due to the fact that temperature gradient is assumed. The mathematical equation of the problem is confined in a fractional energy balance equation (FEBE), which furnishes the temperature portrayal in conduction state having uniform heat source on steady state. The fractional Laplace decomposition technique is utilized to obtain the numerical solution of the corresponding FEBE describing the exothermic reactions. Some numerical results for the fractional exothermic reactions model are presented through graphs and tables.
TL;DR: In this article, the authors used a triangular wave form of conductive corrugated partition for free convection in a cavity with a corrugation partition which have different fluids on different parts of the partition was numerically examined.
Abstract: In the present study, free convection in a cavity with a corrugated partition which have different fluids on different parts of the partition was numerically examined. In one of the domains carbon nanotube (CNT)-water nanofluid with an inclined uniform magnetic field is considered. A triangular wave form of conductive corrugated partition is used. The numerical simulation was performed with Galerkin weighted residual finite element method. Various values of pertinent parameters of current thermal configuration such as Rayleigh number (between 104 and 106), Hartmann number (between 0 and 50), magnetic inclination angle (between 0° and 90°), solid particle volume fraction (between 0 and 0.03), number of triangular waves (between 1 and 40), height of triangular waves (between 0.01H and 0.2H) and thermal conductivity ratio (between 0.1 and 100) and their influence on the hydro-thermal behavior were examined. It was observed that significant enhancements in the Nusselt number is obtained with CNTs. The average heat transfer decreases for higher values of Hartmann number but slightly varies as the value of magnetic inclination angle changes. As the number and height of the triangular waves increase, the average heat transfer reduce which are 32 % and 27 % for the highest values of number and height of triangular waves both for water and nanofluid. For forecasting the average heat transfer coefficient of the current thermal system, a novel method based on Proper Orthogonal Decomposition (POD) and Adaptive-Network-Based Fuzzy Inference System (ANFIS) is used which yields highly accurate results that are computationally inexpensive.
TL;DR: A comprehensive review of the lattice Boltzmann (LB) method for single-phase and solid-liquid phase-change heat transfer in porous media at both the pore scale and representative elementary volume (REV) scale is presented in this paper.
Abstract: Over the past 30 years, the lattice Boltzmann (LB) method has been developed into a versatile and powerful numerical methodology for computational fluid dynamics and heat transfer. Owing to its kinetic nature, the LB method has the capability to incorporate the essential mesoscopic physics, and it is particularly successful in modeling transport phenomena involving complex boundaries and interfacial dynamics. Up to now, the LB method has achieved great success in modeling fluid flow and heat transfer in porous media. Since the LB method is inherently transient, it is especially useful for investigating transient solid-liquid phase-change processes wherein the interfacial behaviors are very important. In this article, a comprehensive review of the LB methods for single-phase and solid-liquid phase-change heat transfer in porous media at both the pore scale and representative elementary volume (REV) scale. The review first introduces the fundamental theory of the LB method for fluid flow and heat transfer. Subsequently, the REV-scale LB method for fluid flow and single-phase heat transfer in porous media and the LB method for solid-liquid phase-change heat transfer are discussed in detail. Moreover, the applications of the LB methods in single-phase and solid-liquid phase-change heat transfer in porous media are reviewed. The LB modeling and predictions of the effective thermal conductivity of porous materials are also reviewed. Finally, further developments of the LB method in the related areas are briefly discussed.
TL;DR: In this article, the effect of magnetic field on Ag-MgO nanofluid forced convection and heat transfer in a channel with active heaters and coolers is analyzed.
Abstract: A two-dimensional (2D) numerical simulation is presented to study the effect of magnetic field on Ag-MgO nanofluid forced convection and heat transfer in a channel with active heaters and coolers. A Fortran code according to Lattice Boltzmann method (LBM) is developed for this purpose. The effects of thermal arrangement (Case1, 2 and 3), block side length (0.3 ≤ h ≤ 0.5), Reynolds number (50 ≤ Re ≤ 100), Hartmann number (0 ≤ Ha ≤ 60) and volume fraction of nanoparticles (0 ≤ ϕ ≤ 0.02) on flow pattern and heat transfer characteristics are analyzed systematically. The obtained results showed that the highest value of local Nusselt number occurs at the junction of the heater and the cooler due to the high temperature gradient, followed by the sharp corner of heaters and coolers. Moreover, the heat transfer at the heater sharp corner is higher than that of the cooler sharp corner. The average Nusselt numbers indicated that the rate of heat transfer increases with increasing ϕ or decreasing Ha. Finally, the heat transfer rate in Case 1 is more than Case 3 and Case 2.
TL;DR: In this article, the effect of the Brownian motion on the effective thermal conductivity and viscosity of nanofluid was investigated in a baffled U-shaped enclosure in the presence of a magnetic field.
Abstract: In this study, nanofluid natural convection in a baffled U-shaped enclosure in the presence of a magnetic field is investigated. Lattice Boltzmann method (LBM) is used to study present problems. KKL (Koo-Kleinstreuer-Li) correlation is applied to calculate the effective thermal conductivity and viscosity of nanofluid. The effect of the Brownian motion on the effective thermal conductivity is considered in this correlation. The combination of the four topics (nanofluid, U-shaped enclosure, baffle, magnetic field) is the main novelty of the present study. Effect of Rayleigh number, Hartmann number, nanoparticle volume fraction and cavity aspect ratio on the flow field and heat transfer characteristics have been investigated. The results demonstrate that the average Nusselt number increases by increments of the Rayleigh number, nanoparticle solid volume fraction and aspect ratio. However, the rate of heat transfer is suppressed by the magnetic field. The effect of magnetic field on heat transfer is more significant at higher Rayleigh number and the effect of Ra on the average Nusselt number is more noteworthy at lower Ha. Besides, the effect of Rayleigh number on heat transfer enhancement becomes more significant at higher aspect ratio.
TL;DR: In this article, a compact and lightweight liquid-cooled BTM system is presented to control the maximum temperature (Tmax) and the temperature difference (ΔT) of lithium-ion power battery pack.
Abstract: Battery thermal management (BTM) is indispensable to the battery pack of electric vehicles (EVs) for safety. Among different types of BTM technologies, liquid cooling shows its superiority with high heat transfer coefficient and low power consumption. However, the previous works paid little attention to the compactness and weight ratio of liquid-cooled BTM system, which is vital to the specific energy of battery pack. In this study, a compact and lightweight liquid-cooled BTM system is presented to control the maximum temperature (Tmax) and the temperature difference (ΔT) of lithium-ion power battery pack. In this liquid-cooled solution, one thermal conductive structure (TCS) with three curved contact surfaces is developed to cool cylindrical battery. The influences of mass flow rate (mf), inner diameter (d), contact surface height (h) and contact surface angle (α) of the TCS are investigated through numerical study. It is found that for the 5C discharge rate process of battery, Tmax can be maintained within 313 K when mf is larger than 1 × 10−4 kg/s. A weight sensitive factor is defined to evaluate the influences of d, h and α on ΔT and the weight of TCS. It is found that d is the most important parameter that influences the weight. h is the secondary parameter, and α is the parameter with the minimal impact on the weight. Then the values of d, h, and α are designed to reduce the weight of TCS while maintaining its cooling performance. The designed TCS can control Tmax under 313 K with ΔT as 4.137 K. Compared to the original TCS, ΔP, ΔT and the weight are respectively reduced by 80%, 14% and 46% for the designed TCS. Furthermore, the performance of liquid-cooled system with parallel TCSs is discussed. The flow distribution among parallel TCSs is improved through designing the positions of the inlet and the outlet, which enables that Tmax and ΔT of battery pack is similar to the ones of a single battery. The present study facilitates the guideline for compact and lightweight design of liquid-cooled battery thermal management system.
TL;DR: In this paper, a liquid cooling system for lithium-ion battery with changing contact surface is designed, and a mathematical derivation and numerical analysis are conducted to evaluate cooling performance and the consumption of pump power, and the results show that increasing inlet mass flow can effectively limit the maximum temperature, but cannot improve temperature uniformity significantly.
Abstract: Liquid cooling system is of great significance for guaranteeing the performance of lithium-ion battery because of its good conductivity to keep battery working in a cool environment. In this paper, a liquid cooling system for lithium-ion battery with changing contact surface is designed. Contact surface is determined by the width of cooling plate. Mathematical derivation and numerical analysis are conducted to evaluate cooling performance and the consumption of pump power. The results show that increasing inlet mass flow can effectively limit the maximum temperature, but cannot improve temperature uniformity significantly. The temperature is proportional to the inlet temperature, but inversely proportional to the width of cooling plate. Considering the effect of temperature on thermal properties, the thermal properties will weaken the effect of width of cooling plate, inlet temperature and mass flow rate on temperature performance, specifically the maximum temperature and temperature difference, and cause temperature changes in a nonlinear manner. It is difficult to improve the overall performance of the battery by only optimizing a single factor. Three factors (mass flow rate, inlet temperature, the width of cooling plate) for the thermal performance of battery are optimized by using the single factor analysis and the orthogonal test. The best cooling performance can be obtained when inlet temperature is 18 °C, the width of cooling plate is 70 mm and the mass flow rate is 0.21 kg/s. With the use of the optimization method, the lower bound of temperature and the temperature uniformity of battery are achieved and the pump consumption can be reduced. The strategy adopted in this research can be widely applied to battery thermal management to reduce analysis time.
TL;DR: In this article, a novel serpentine-channel liquid cooling plate with double inlets and outlets is developed for better managing an undesirable temperature distribution of a cell module, and numerical analyses are implemented using the software of FloEFD to study effects of flow directions, flow rates and channel widths of the cooling plate on cell temperature distribution under different operating conditions; a ratio of power consumption as a non-dimensional number is defined to analyze the hydraulic performance of the developed cooling plate.
Abstract: The thermal management for a lithium ion battery cell plays a pivotal role in enhancing the cell performance and reliability for electric vehicles. In this work, a novel serpentine-channel liquid cooling plate with double inlets and outlets is developed for better managing an undesirable temperature distribution of a cell module. With a simplified model for the cell module, numerical analyses are implemented using the software of FloEFD to study effects of flow directions, flow rates and channel widths of the cooling plate on cell temperature distribution under different operating conditions; Likewise, a ratio of power consumption as a non-dimensional number is defined to analyze the hydraulic performance of the developed cooling plate. Results show that locations of the inlet and the outlet as well as flow directions have great impacts on the cell temperature distribution and the ratio of power consumption of the cooling plate. Increasing fluid flow rate substantially decreases the maximum temperature rise of the cell module while it has little effect on the temperature distribution. Moreover, the channel width of the cooling plate has a strong influence on its ratio of power consumption as well as the cell temperature distribution but it has a weak influence on the cell maximum temperature rise. Interestingly, the developed serpentine-channel cooling plate offers one a new method to design a lithium ion battery thermal management system for controlling temperature distribution of a cell module.
TL;DR: In this paper, a fractal model based on the capillary model and fractal theory of porous media is proposed to quantify the effective electrolyte diffusivity in porous media with consideration of the electrical double layer (EDL) effects.
Abstract: Electrolyte diffusion in electrolyte solutions exists in various areas including rechargeable batteries, soil physics and chemical engineering. In this paper, a fractal model based on the capillary model and fractal theory of porous media is proposed to quantify the effective electrolyte diffusivity in porous media with consideration of the electrical double layer (EDL) effects. The present model explicitly relates to the micro-structural parameters of porous media and electrokinetic parameters. To validate this model, a comparison is carried out with experimental data and semi-analytical model results, and yields satisfying agreement. Besides, the influences of the parameters (the porosity, equivalent particle diameter, ratio of the minimum pore radius to the maximum pore radius, molar concentration, zeta potential, and dimensionless parameter β ) are discussed in details.
TL;DR: In this article, the authors provide a comprehensive review of published literature concerning heat transfer benefits of nanofluids for both macro-channels and micro channels, including both experimental and numerical findings concerning several important performance parameters, including single-phase and two-phase heat transfer coefficients, pressure drop, and critical heat flux.
Abstract: This paper provides a comprehensive review of published literature concerning heat transfer benefits of nanofluids for both macro-channels and micro-channels. Included are both experimental and numerical findings concerning several important performance parameters, including single-phase and two-phase heat transfer coefficients, pressure drop, and critical heat flux (CHF), each being evaluated based on postulated mechanisms responsible for any performance enhancement or deterioration. The study also addresses issues important to heat transfer performance, including entropy minimization, hybrid enhancement methodologies, and nanofluid stability, as well as the roles of Brownian diffusion and thermophoresis. Published results point to appreciable enhancement in single-phase heat transfer coefficient realized in entrance region, but the enhancement subsides downstream. And, while some point to the ability of nanofluids to increase CHF, they also emphasize that this increase is limited to short duration boiling tests. Overall, studies point to many important practical problems associated with implementation of nanofluids in cooling situations, including clustering, sedimentation, and precipitation of nanoparticles, clogging of flow passages, erosion to heating surface, transient heat transfer behavior, high cost and production difficulties, lack of quality assurance, and loss of nanofluid stability above a threshold temperature.
TL;DR: Results indicate that LSSVM approach has the best performance and the proposed model by this approach has R-squared value equals to 1.
Abstract: Nowadays, nanofluids are broadly utilized for various engineering and industrial systems including heat exchangers, power plants, air-conditioning, etc The helically coiled tube heat exchangers are of the most interesting and efficient kinds of heat exchangers The current study has focused on proposing model to predict Nusselt number by considering Prandtl number, volumetric concentration, and helical number of helically coiled heat exchanger as input variables The investigated heat exchanger utilizes water carbon nanofluid To propose an accurate model, a multilayer perceptron artificial neural network (MLP-ANN), adaptive neuro-fuzzy inference system (ANFIS), and least squares support vector machine (LSSVM) models are used 72 experimental data are utilized as input data Results indicate that LSSVM approach has the best performance and the proposed model by this approach has R-squared value equals to 1
TL;DR: In this article, the impact of volume concentration of Fe3O4 nanoparticles and temperature on the viscosity and thermal conductivity of liquid paraffin based nanofluid was analyzed.
Abstract: This research aims to understand the impacts of volume concentration of Fe3O4 nanoparticles and temperature on the viscosity & thermal conductivity of liquid paraffin based nanofluid. Several experiments are conducted in the Fe3O4 concentration range of 0.5–3% and temperature range of 20–90 °C. Oleic acid is utilized as a surfactant for the improved dispersibility and stability of nanofluids. It was found that the nanofluid behaves as a shear thinning fluid. Additionally, it was revealed that both the thermal conductivity and viscosity boost with increasing the nanoparticle concentration, whereas when the temperature increases the viscosity reduces and the thermal conductivity rises. Moreover, the Artificial Neural Network (ANN) was utilized to model the thermal conductivity and viscosity of the nanofluid using experimental data. The accuracy of the models was assessed based on four known statistical indices including root meant square (RMS), root mean square error (RMSE), mean absolute deviation (MAE), and coefficient of determination ( R 2 ). Results showed that the proposed model of thermal conductivity could estimate outputs with RMS, RMSE, MAE & R 2 values of 0.0678, 0.0179, 0.0041 and 0.96, respectively.
TL;DR: In this article, a critical review of different heat sink designs, limiting factors, effectiveness, limitations of various techniques and recent advancements in the field of innovative heat sinks is presented. But, the focus of the review was not on the design of the heat sink, but rather on its suitability for present day heat dissipation issues, statistical data of various heat sinks designs and a rich discussion of the work so far.
Abstract: With the prologue of new components with more and more heat dissipation, urge for novel heat sink philosophy is becoming a real challenge in today’s world. The new solutions should be able to cope with massive heat emanation while keeping the space and cost constraints. Finned (plate and pin) heat sinks are contrivance to these challenges with growing applications in present-day engineering arena and drawing the concentration of researchers. Paper deals with the critical review of different heat sink designs, limiting factors, effectiveness, limitations of various techniques and recent advancements in the field of innovative heat sinks. This study initiates with brief and comprehensive discussion regarding importance of heat sinks, its methodology; it’s suitability for present day heat dissipation issues, statistical data of various heat sink designs and a rich discussion of the work so far. The sole aspiration for this article is digging out the literature available so far with emphasis on experimental techniques and to propose strategy for future research. The outcome of the research will validate the concept of improved heat transfer approach, provide useful data for innovative design and help better understand the cooling capabilities of the pin fin technology.
TL;DR: In this paper, a phase change materials (PCM) based battery thermal management system (BTMS) is proposed for heat transfer enhancement, which consists of longitudinal fins and cylindrical rings.
Abstract: Phase change materials (PCM) based battery thermal management system (BTMS) usually suffers from the low thermal conductivity of PCM. In this paper, novel fin structures which consist of longitudinal fins and cylindrical rings are proposed for heat transfer enhancement. Experiments are firstly designed to compare the thermal performance of different BTMSs. Results demonstrate that the PCM-Fin system shows superior performance over the pure battery system and the PCM system. Numerical simulations are also conducted based on the model validation with the experimental data to reveal the underlying mechanisms. It is found that fin structures not only increase the heat transfer area but also introduce a thermal conductive network within the PCM, which contributes positively to the improvement of thermal performance of the battery. Moreover, the effects of the position of rings, the number of rings and fins, and the heat generation rate on the thermal management performance are evaluated. Results show that the optimal numbers for rings and fins are 1 and 8, respectively, and the recommended dimensionless distance between ring and battery is 0.2. It is also found that the PCM-Fin system can control the temperature rise of the battery even under the heat generation rate of 20 W.
TL;DR: In this paper, a novel cooling strategy based on air distribution pipes is proposed for the cylindrical Liium-ion battery module, and the results show that the maximum temperature of the battery module can be effectively reduced by the increase of inlet pressure resulting in a significant rise of power consumption.
Abstract: For a typical air cooling thermal management system, the inlet and outlet of air flow on both sides of the battery module would increase the temperature difference. In here, a novel cooling strategy based on air distribution pipes is proposed for the cylindrical Lithium-ion battery module. The three-dimensional computational fluid dynamics model of battery module is constructed and validated by the experimental tests. The thermal behavior of battery module and the flow field of air have been explored using numerical simulations at different discharge rates, and then the effects of orifice parameters, inlet pressure and discharge rate on the performance of air cooling strategy have been analyzed. The results show that the maximum temperature of the battery module can be effectively reduced by the increase of inlet pressure resulting in a significant rise of power consumption. Meanwhile, it declines when the diameter and number of rows of the orifice increase, following a minor rise in power consumption. When the inlet pressure is 100 Pa, the diameter of the orifice is 1.5 mm, the number of rows of the orifice is 5 and the discharge rate is 3C, the maximum temperature of battery module decreases from 325.9 K to 305.7 K in comparison to that under none air cooling condition. In addition, the maximum temperature difference of battery module is within 3 K. When the battery module discharge at the current rate of 4C and 5C, the maximum temperature of battery module maintains within 313.15 K, but the temperature difference slightly exceeds the optimal range at 5C discharge when the inlet pressure is 200 Pa, the diameter of the orifice is 1.5 mm and the number of rows of the orifice is 5. Moreover, it is an efficient and a practical cooling strategy with no need to modify the arrangement of the battery module.
TL;DR: In this paper, a double multi relaxation time (MRT) Lattice Boltzmann method (LBM) has been used to simulate magnetohydrodynamics (MHD) natural convection in a porous media.
Abstract: In this paper, a new double multi relaxation time (MRT) Lattice Boltzmann method (LBM) has been used to simulate magnetohydrodynamics (MHD) natural convection in a porous media. A new nanofluid named; multi-walled carbon nanotubes–iron oxide/water nanofluid (MWCNT–Fe3O4/water hybrid nanofluid) has been utilized to investigate the effect of nanoparticle on heat transfer. The thermo-physical properties of the nanofluid have been extracted from experimental results. D2Q9 and D2Q5 lattices are used to solve the flow and temperature fields respectively, and the effect of various parameters such as; Darcy number (Da) (10−2–10−1), Rayleigh number (103 ≤ Ra ≤ 105), porosity (0.4 ≤ e ≤ 0.9), volume fraction of nanoparticles (0≤ O ≤ 0.003) and Hartmann number (0 ≤ Ha ≤ 50) have been investigated. Based on the present results, the new double MRT LBM is a proper method to solve the complex flows such as MHD natural convection in porous media. The results show that augmentation of Rayleigh number increases the heat transfer rate for all cases however by increasing the Hartmann number the effect of Rayleigh number decreases. Also, adding the nanoparticles enhances the average Nusselt number as increases 4.9% for Ra = 105, Da = 10−1, Ha = 50, and e = 0.9 when the volume fraction of nanoparticles rises from 0 to 0.003. Results indicate that by enhancing Darcy number heat transfer rate increases and average Nusselt number improves by porosity.
TL;DR: In this paper, a multiphysics numerical model for the multi-track/multi-layer L-PBF is developed and used for analysing the formation and evolution of voids caused by lack of fusion and improper melting.
Abstract: Laser-based powder bed fusion (L-PBF) is a branch of additive manufacturing technology which is considered to be a superior process due to its capability of producing complex designs with low material waste. Despite L-PBFs various unique characteristics, manufactured parts still suffer from a wide variety of defects, among which porosity is one of the most important. In this paper, a multiphysics numerical model for the multi-track/multi-layer L-PBF is developed and used for analysing the formation and evolution of voids caused by lack of fusion and improper melting. The multiphysics model is in meso-scale and is used to track and observe the formation of porosities, and considers phenomena such as multi-phase flow, melting/solidification, radiation heat transfer, capillary and thermo-capillary (Marangoni effect) forces, recoil pressure, geometry dependant absorptivity and finally evaporation and evaporative cooling. A novel methodology has been introduced to model the two subsequent powder-laying and fusion processes, for each layer, by means of a discrete element method (DEM) in a Lagrangian framework and a computational fluid dynamics (CFD) model, both implemented in Flow-3D. The results for the investigated process parameters indicate that the porosities (voids) are mainly formed in between the tracks, largely due to improper fusion of the particles. Moreover, it is observed that the pores are mostly elongated in the direction parallel to the laser scanning paths, as expected. The probability of the presence of pores is also observed to be higher in the first layer, where the average layer temperature is lower as well. Furthermore, the lack of fusion zones are seen to become smaller in the subsequent layers, largely due to better fluid flow and higher temperatures, because of heat accumulation in those layers.
TL;DR: In this paper, a two-dimensional numerical model based on finite volume method (FVM) was developed with considering natural convection and the calculation results were validated with experimental data.
Abstract: Embedded fin in phase change materials (PCMs) is one of the most efficient methods to enhance the heat transfer between the PCM and heat transfer fluid (HTF). An appropriate arrangement of the fins plays significant role to design a highly efficient latent heat thermal energy storage (LHTES) unit. The aim of this study is to find the most efficient arrangement of fins to accelerate the charging rate. A two-dimensional numerical model based on finite volume method (FVM) was developed with considering natural convection and the calculation results were validated with experimental data. The heat transfer characteristics of LHTES unit with different fins arrangements were firstly explored. These include no fins, straight fins, angled fins, lower fins and upper fins. Then, the effects of fins number (N), dimensionless fins length (l), heat transfer fluid temperature (Tw) and outer tube material on melting performance for four arrangements were studied. In addition, the best type of arrangements to increase the efficiency of heat exchanger was suggested. The performance enhancement of LHTES through fins configuration were quantitatively described based on complete melting time and heat storage capacity, and the conclusions are arrived as follows: when N ≤ 6, the optimum arrangement is the lower fins, while it is the angled fins when N > 6. For N = 6, only l could change the optimum arrangement of fins. At l equals 0.5 and 0.95, the optimum arrangement is angled case. While at l = 0.75, the optimum arrangement is lower case. It is also found that the heat storage capacity of lower fins configuration is minimal compared to other three configurations.
TL;DR: In this article, a novel conjugated cooling configuration using phase change material (PCM) and liquid cooling techniques is proposed, and its thermal performance is investigated for a battery module.
Abstract: A novel conjugated cooling configuration using phase change material (PCM) and liquid cooling techniques is proposed, and its thermal performance is investigated for a battery module. 106 cylindrical batteries are connected to the cold plate at the bottom through a heat spreading plate and the adjacent thermal columns, with PCM filled in between the gaps, which forms the cooling configuration. Three-dimensional numerical models are established for the cooling of the representative battery and battery module, which includes the battery connected to a liquid cooled mini-channel cold plate through the heat spreading plate and thermal column structures. The thermal characteristics of the battery incorporating the PCM melting and liquid cooling are examined at large flow rate. The geometrical parameters such as the size of the thermal column, the thickness of the heat spreading plate and the spacing of the batteries are investigated for the present conjugated cooling configuration. Both the battery temperature ramp-up rate and the steady-state battery temperature are significantly reduced by the conjugated cooling, in comparison with single PCM or liquid cooling conditions. The effects of various structure parameters on the thermal performance can be visualized by plotting the working time t50 vs the heat density based on the PCM volume. A comparison of the numerical simulation with the preliminary experiment work shows good agreement. This work can be useful in the design of conjugated configurations for the battery thermal management.