Porous Fin Research Articles

Convective-radiative moving porous fin with temperature-dependent thermal conductivity, heat transfer coefficient and wavelength-dependent surface emissivity

PurposeIn this paper, temperature distribution and fin efficiency in a moving porous fin have been discussed. The heat transfer equation is formulated by using Darcy's model. Heat transfer coefficient and thermal conductivity vary with temperature. The surface emissivity of the fin varies with temperature as well as with wavelength. Thermal conductivity is taken as a linear and quadratic form of temperature. The entire analysis of the paper is presented in non-dimensional form.Design/methodology/approachIn this study, a new mathematical model is investigated. The novelty of this model is surface emissivity which is considered temperature and wavelength dependent. Another interesting point is the addition of porous material. The Legendre wavelet collocation method has been used to solve the nonlinear heat transfer equation. Numerical simulations are carried out in MATLAB software.FindingsAn attempt has been made to discuss temperature distribution in the presence of porosity and wavelength-temperature-dependent surface emissivity. The effect of various parameters on temperature has been discussed, including thermal conductivity, emissivity, convection-radiation, Peclet number, sink temperature, exponent “n” and porosity. Fin efficiency is also calculated for some parameters. According to the study, heat transfer rate increases with higher radiation-convection, emissivity, wavelength and porosity parameters.Originality/valueThe numerical results are carried out by using the Legendre wavelet collocation method, which has been compared with exact results in a particular case and found to be in good agreement. The percent error is calculated to find the error between the current method and the exact result. A comparison of the obtained results with the previous data is presented to validate the numerical results.

Entropy generation analysis on thermo-hydraulic characteristics of microencapsulated phase change slurry in wavy microchannel with porous fins

• Combined design enables smaller temperature gradient and more uniform temperature. • Larger h m and lower ΔP can be concurrently gained in wavy MCHS with porous fins. • Thermal entropy is three orders of magnitude larger than the frictional entropy. • Thermal entropy increases with heat flux but the frictional entropy is opposite. • Lower irreversible losses can be achieved at the cost of higher power consumption. Recent advancement in micro/nano-scale electronic systems, the need for efficient heat dissipation has become more rigorous, and traditional thermal management solutions are facing enormous challenges. In this study, a novel combined design of wavy microchannel heat sink (MCHS) with porous fins and microencapsulated phase change material (MPCM) suspension is developed and numerically studied to achieve a balance between flow and heat transfer behaviors. The equivalent heat capacity method is adopted to deal with the phase change process of microcapsule particles in steady and laminar states, and the Brinkman–Darcy–Forchheimer model based on the volume-averaged method is employed to characterize the fluid flow in porous fins. A three-dimensional solid-fluid conjugate model is established based on the finite-volume method to investigate the effects of different coolant types (water and MPCM suspension), geometric parameters (wavy amplitude, wavelength, and channel width ratio), and working conditions (inlet flow velocity, heat flux, and slurry concentration) on the thermo-hydraulic properties and entropy generation of wavy MCHS. The results reveal that the combination of porous fins and MPCM suspension presents smaller temperature gradient and more uniform temperature distribution than conventional design. Larger heat transfer coefficient and lower pressure drop can be simultaneously obtained in wavy MCHS with porous fins than in solid fin configuration. The thermal entropy generation is three orders of magnitude larger than the frictional entropy generation, and the Bejan number is close to 1 for different microchannel configurations. Thermal entropy generation increases with increasing heat flux but the frictional entropy generation decreases. Lower irreversible losses can be achieved at the expense of greater pumping power consumption caused by increasing inlet velocity and suspension concentration. The superior effect of wavy MCHS with porous fins using MPCM suspension as coolant has been observed in all cases.

Correction to: Efficient Iterative Method for Investigation of Convective–Radiative Porous Fin with Internal Heat Generation Under a Uniform Magnetic Field

Correction to: Efficient Iterative Method for Investigation of Convective–Radiative Porous Fin with Internal Heat Generation Under a Uniform Magnetic Field

Thermal and multi-boiling analysis of a rectangular porous fin: A spectral approach

Abstract Fins are commonly utilized to enhance (dissipate) heat in various engineering systems that include heat exchangers. In the present investigation, the impact of multi-boiling and thermo-geometric factors on a convective–radiative rectangular porous fin subjected to the temperature-dependent thermal conductivity of linear and non-linear variations is discussed extensively. The governing equations describing the problem were formulated with the aid of Darcy law. Similarity variables were employed to reduce the models to non-dimensional form. The solution of the governing dimensionless equation is approximated using the RK4 and spectral local linearization methods. Before parametric analysis, the agreement between the two numerical methods was established. Findings reveal that the non-linear variation of thermal conductivity shows better thermal efficiency than the linear variation. An improvement in the multi-boiling heat transfer parameter retards the temperature distribution of the fin. Furthermore, increasing the thermo-geometric parameter will result in a progressive decrease in the temperature of the fin. The results obtained in this work will aid in the design of heat exchangers and other heat transfer equipments.

Heat transfer and flow characteristics in symmetric and parallel wavy microchannel heat sinks with porous ribs

Based on the synergistic design concept, double-layered microchannel heat sinks with parallel and symmetric wavy porous fins are developed with the desire to simultaneously attain pressure drop reduction, heat transfer enhancement, and cooling uniformity improvement. Using a 3D fluid-solid conjugate model, the hydrodynamic and thermal details are numerically studied to compare two wavy configurations with the solid- and porous-fin designs. The results demonstrate that for wavy microchannel heat sinks, the porous-fin design can significantly enhance heat transfer performance and reduce pressure drop. The symmetric configuration yields a higher pressure drop reduction, whereas the parallel one provides a higher increment in thermal performance. As a result, using the porous design, two wavy configurations have nearly the same level of pressure drop penalty, but the parallel configuration contributes to higher thermal performance. The decreased flow rate of the channel due to the permeation of coolant fluids into porous ribs and the slip effect on the channel wall contribute to the pressure drop reduction. The permeation effect of coolant greatly restrains secondary flow characteristics induced by wavy walls which are responsible for the enhanced coolant mixing in conventional heat sinks. Consequently, the increased inlet flow velocity at a constant pumping power contributes to the improved thermal performance, namely the reduced thermal resistance and the increased Nusselt number. With a stronger coolant permeation owing to the jet-like impingement flow, the parallel configuration yields a slightly lower thermal performance compared to the symmetric configuration in the new design. Finally, the parametric analysis at a fixed pumping power is further carried out for optimizing the proposed design.

Porous-fin microchannel heat sinks for future micro-electronics cooling

Porous-fin microchannel heat sinks offering high solid-fluid interfacial areas have the potential to be an integral part of future microelectronic cooling systems. Replacing solid with porous fins reduces the pressure drop penalty of the straight plate-fin microchannel heat sinks. However, prior research has shown that in some cases porous fins adversely affect the thermal performance of the microchannel heat sinks. The reduced effective thermal conductivity of the porous fins compared to the solid ones has been considered the main reason for the reduced thermal performance of porous-fin microchannels. In this work, a detailed study is conducted to assess the feasibility of using porous fins to simultaneously improve the thermal and hydraulic performances of the straight plate-fin microchannel heat sinks. Results revealed that the porous-fin microchannels outperform the solid-fin microchannels at small channel heights. However, at high channel heights, the low effective thermal conductivity of porous fins results in a weak vertical thermal diffusion. Consequently, replacing solid with porous fins degrades the thermal performance of the microchannel at high channel heights. Additionally, the porous-fin microchannels exhibit better thermal performance than the solid-fin microchannels at fin to fluid width ratios above 0.25. The increased coolant mass flow penetrated the porous fin section is the main reason for the enhanced heat transfer rate of the porous-fin microchannels at higher width ratios. Moreover, the porous-fin microchannels offer a lower pressure drop penalty than the solid-fin microchannels under all examined operating conditions. This research confirms the potential of substituting solid with porous fins to simultaneously improve the thermal and hydraulic performances of the straight plate-fin microchannel heat sinks.

Nonlinear Thermal Response Analysis of an Internally Heated Radiative-Convective Porous Fin subjected to Magnetic Fields using Method of Lines

This paper demonstrated the computational efficiency and accuracy of method of lines for the nonlinear transient thermal response analysis of a radiative-radiative porous fin with temperature-dependent internal heat generation under the influence of magnetic fields. To establish the computational accuracy of the method, the results of the solution are compared with the results of the developed exact analytical method. Also, the numerical solutions through the method of lines are adopted to explore the impacts of the model parameters on the performance of the passive device. It is found that as the conductive-convective, conductive-radiative, and magnetic field parameters increase, the fin temperature distribution in the fin decreases. The temperature distribution in the fin increases through the ?n as the nonlinear thermal conductivity parameter increases. It is hoped that the present study gives a good insight into the nonlinear analysis of the extended surface which will aid the proper design of the extended surfaces in thermal systems.

Hybrid Method for Predictive Transient Nonlinear Analysis of a Radiative-Convective Moving Porous Fin with Temperature-variant Internal Heat Generation

In this work, Laplace transform-Legendre-wavelet collocation method is adopted for a semi-numerical analysis of predicting transient nonlinear behaviour of a radiative-convective fin with temperature-variant internal heat generation. The verification of the results of the hybrid method shown good agreements with the direct numerical and approximate analytical method s in previous works. Parametric analysis depicts the significance of the model parameters in a way that it is found that as the convective-conductive and radiative-conductive parameters increase, temperature distribution decreases in the extended surface. The thermal distribution is augmented in the passive device as thermal conductivity is amplified. At the different positions in the fin, the temperature is enhanced as time progress. The semi-numerical solution provides a very good platform for the predictive analyses of the extended surfaces.

Performance enhancement for exhaust thermoelectric power generation system by using porous pin fins based on a fully automatic optimization method

An intelligent optimization method combining Non-dominated Sorting Genetic Algorithm-II (NSGA-II) algorithm and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) decision is implemented to design the optimal arrangement of porous pin fins in the flow channel of the exhaust thermoelectric power generation (ETEG) system. This method realizes the optimal arrangement of the porous pin fins while considering the two contradictory performance indicators at the optimization level: system output power (P) and pressure drop (Pd). In this work, the design of porous and solid pin fins is first compared. Secondly, four typical pin fins arrangement models are established with preliminary analysis. Finally, the NSGA-II-TOPSIS intelligent optimization method is implemented, which takes P and Pd as objective function, the position, number and relative distance of the porous pin fins as optimization variables simultaneously. Through iterative optimization, the optimal arrangement scheme achieves a proper balance between P and Pd. The main conclusions include: The design of the porous pin fins can increase 22.89% for P of the ETEG system while reduces 82.98% for Pd. The distribution of dense downstream of porous pin fins can best improve the ETEG system performance. After optimization, higher P and lower Pd of the ETEG system are obtained with fewer pin fins. A new index is proposed to evaluate optimal solutions, the optimal design with 2 porous pin fins reaches the highest value: 5.86 W Pa−1, which means that each pin fin is fully used.

Prediction of Thermal Distribution in an Internally Heated Radiative-Convective Moving Porous Fin with variable Thermal Conductivity using Homotopy Perturbation Method

Thermal distribution of a rectangular moving convective-radiative porous fin with temperature-dependent thermal conductivity and internal heat generation is analyzed in this work homotopy perturbation method. With the aid of the analytical solutions, the impacts of the model parameters on the thermal behaviour of the fin are investigated. The parametric analysis reveals that increase in porosity and convective parameters, the rate of heat transfer from the fin increases and consequently improves the efficiency of the fin. The values of the temperature distribution in the fin increase as the Peclet number increases. However, as thermal conductivity and internal heat generation increase, the rate of heat transfer from the fin decreases. Therefore, the operational parameters of the fin must be carefully selected to ensure that the fin retains its primary purpose of removing heat from the primary surface.

Novel converging–diverging microchannel heat sink with porous fins for combined thermo-hydraulic performance

The optimum design of the microchannel heat sinks needs to consider both the heat transfer and pressure drop limitations of the microchannel. In this paper, a novel configuration of the microchannel heat sink is proposed to obtain improved thermo-hydraulic performance. The proposed microchannel includes porous fins that form adjacent converging–diverging channels. Three-dimensional steady laminar simulations were conducted to access the performance of this novel microchannel and compare it with the conventional parallel ones with porous and solid fins. The results showed that by using this novel design, a 9.75% decrease in pressure drop is observed when compared to conventional solid fin parallel microchannel. Also, the mean Nusselt number of the microchannel heat sink with converging–diverging porous fins showed a maximum improvement of 16.5% compared to the parallel microchannel with solid fins. The overall thermo-hydraulic performance evaluation factor of the converging–diverging microchannel showed also a significant 20% improvement compared to conventional designs. The analysis of the flow fields showed that the converging–diverging design with porous fins leads to a local pressure difference between two adjacent neighboring channels inducing a cross-wise velocity component within the porous fins leading to enhanced thermal performance. Moreover, it was shown that only for converging–diverging angles above 0.5 °, performance enhancement was observed compared with a microchannel with solid fins showing the existence of an optimum range for converging–diverging angles. The response surface method was used to find the optimum range of fin porosity and converging–diverging angle where the performance of the microchannel heat sink is maximum.

Comparative Analysis of Temperature Distributions in a Convective-Radiative Porous Fin using Homotopy Perturbation and Differential Transformation and Methods

In this work, a comparative study of two approximate analytical methods for the thermal behaviour of convective-radiative porous fin subjected to the magnetic field using homotopy perturbation and differential transform methods is presented. Also, parametric studies of the effects of thermal-geometric and thermo-physical fin parameters are investigated. From the study, it is found that an increase in a magnetic field, porosity, convective, radiative, and parameters increase the rate of heat transfer from the fin and consequently improves the efficiency of the fin. There are good agreements between the results of the homotopy perturbation and differential transform method with the results of the numerical method. Also, the results of the two approximate analytical methods agree very well with each other. It is hoped that the present work will serve as the basis of verifications of the other works on the nonlinear thermal analysis of the extended surface.

Transient analysis of convective-radiative heat transfer through porous fins with temperature-dependent thermal conductivity and internal heat generation

In this research study, the transient study of heat transfer through a convective-radiative porous fin is carried out considering temperature-dependent thermal conductivity and internal heat generation. The unsteady Galerkin weighted residuals technique is employed to obtain the transient temperatures of the porous fin. The results indicate that increasing of the fin base temperature, internal heat generation and, thermal conductivity lead to increase heat transfer along the fin and consequently the higher temperature of the entire of the fin achieved. However, increasing of the porous and radiative parameters result in more heat dissipation from the fin and cause to lowering the fin temperature which leads to increase heat flux entering the fin through the base. Furthermore, the transient thermal analysis of the porous fin illustrates that by increasing the porous and the radiation parameters, the fin cools down faster, so in the applications that the time of cooling is more important, these parameters can be more noticeable.

Significance of non-Fourier heat conduction in the thermal analysis of a wet semi-spherical fin with internal heat generation

The transient temperature distribution of a wet semi-spherical porous fin with convection, internal heat generation, and radiation is researched using a non-Fourier heat conduction (NFHC) model. A mathematical model for transient heat transfer in a dehumidifying environment is developed from the non-Fourier law and the corresponding governing equation is formulated. This equation is subjected to nondimensionalization using suitable dimensionless terms and is further solved by employing the finite difference method (FDM). A substantial deviation in thermal response by considering non-Fourier law under unsteady heat transmission has been analyzed graphically with the influence of various nondimensional parameters on the dry and wetted fins surface. The examination reveals the notable difference in temperature variation between the dry and wetted fins surfaces. Some important key results of the research analysis include that the transient thermal distribution through the fin decrease as the magnitude of the convective, wet porous and radiation-conduction parameters develop. For higher generating numbers, thermal distribution will be higher. The temperature in the hyperbolic model increases after some time in the existence of relaxation time and the temperature in a non-Fourier model flow in the form of a thermal wave.

Inspection of thermal distribution through a porous fin of triangular profile with internal heat generation and electromagnetic field

The transient thermal analysis of a triangular profiled longitudinal porous fin with the combined effect of magnetic and electric fields is explained in this article. The heat transmission through the porous fin is modeled by a time-dependent nonlinear partial differential equation (PDE). The PDE and boundary conditions are transformed into a nonlinear dimensionless PDE with the aid of dimensionless terms. The numerical solution is obtained by using the technique of FDM (finite difference method). The consequences of non-dimensional thermoelectrical and thermomagnetic parameters, and other thermo-physical constraints including generation number, ambient temperature, radiation, and the convective parameter are also examined with the graphical explanations. The outcomes reveal that the emerging radiation, convective parameter, and dimensionless time parameter, faster the fin dissipate heat to the surrounding temperature. The presence of an electromagnetic field assists the triangular porous fin to distribute transient temperature effectively.

Heat transfer analysis from moving convection-radiative triangular porous fin exposed to heat generation

The aim of this work is to analyze the enhancement in the heat transfer and investigate the efficiency of moving, porous and triangular fins. The influence of the various dimensionless parameters, like porosity, radiation-conduction, Peclet number, thermo-geometric parameters, convection-conduction, and surface temperature are analyzed on the efficiency of moving, porous and triangular fins. The model is investigated numerically as well as analytically by using DTM. The result is compared to check the accuracy of the semi-analytical solution, where good agreement is obtained. The effects of the considered parameters on the temperature distribution and efficiency of the considered fins are studied to investigate better efficiency, which plays a significant role in mechanical engineering.

Local hotspot thermal management improved by ionic wind generator coupled with porous materials

Ionic wind is induced by corona discharge caused by extremely inhomogeneous electric field between two electrodes. Due to its compact size, energy saving, flexible design, and easy integration, ionic wind technique exhibits great potential to improve hotspot cooling, especially for compact electronic devices. However, the heat removal capability towards high power density is relatively low due to the limited heat transfer area and low air thermal conductivity. The principle and designs are still lacking for local hotspot cooling. Here, an ionic wind generator with a novel architecture coupled with porous medium is conceived to enhance cooling performance. It is demonstrated that when a porous medium block is coupled, heat transfer can be significantly boosted due to the modified heat and mass transfer in the porous block. It is also found that electrode configuration significantly influences the device performance. There is a trade-off between heat transfer area and airflow impediment in the device. The geometry and property parameters of the porous block are critical for the cooling performance, which is attributed to the modified flow field by changing porous structure. Based on this principle, another ionic wind generator improved by a coupled heat sink with porous fins is proposed, whose performance can be further enhanced by optimizing its design parameters. The optimized heat sink structure can maintain the max temperature of the cooling surface below 83.2 °C at a heat flux of 90 kW/m2. This study provides a promising way for air-side thermal management of hotspot. The findings are helpful for understanding EHD-induced airflow heat transfer in porous medium and shed new light on designing ionic wind generators with better performance.

Effect of Utilizing Staggered Semi-Porous Fins on Channel Flow Heat Transfer Enhancement

A comprehensive numerical investigation of fluid stream and laminar forced convection were conducted to simulate the effects of the semi-porous fins, which are a new combination of porous and solid parts, inside a partially heated channel with a staggered arrangement. The present numerical approach is based on the Navier-Stocks and Darcy-Brinkman-Forchheimer equations in the fluid and semi-porous regions, respectively. The effects of various parameters such as Reynolds number, Darcy number, fin height, and aspect ratio of the porous region’s height to total fin height were studied. Also, the effects of these parameters are illustrated further as a variation of dimensionless pressure penalty and heat transfer enhancement ratio in the flow domain. The results demonstrate that using a new type of fin with both solid and porous parts in a single fin, enhances the heat transfer up to 6% compared to the porous fin and decreases the pressure penalty up to 23% compared to the solid fin at Darcy number of 10−4 when the percentage of aspect ratio is equal to 20%. Furthermore, it was found that the Darcy number of 10−5 is a critical value for the optimum utilization of semi-porous fins.

On the Computational Study of a Fully Wetted Longitudinal Porous Heat Exchanger Using a Machine Learning Approach.

The present study concerns the modeling of the thermal behavior of a porous longitudinal fin under fully wetted conditions with linear, quadratic, and exponential thermal conductivities surrounded by environments that are convective, conductive, and radiative. Porous fins are widely used in various engineering and everyday life applications. The Darcy model was used to formulate the governing non-linear singular differential equation for the heat transfer phenomenon in the fin. The universal approximation power of multilayer perceptron artificial neural networks (ANN) was applied to establish a model of approximate solutions for the singular non-linear boundary value problem. The optimization strategy of a sports-inspired meta-heuristic paradigm, the Tiki-Taka algorithm (TTA) with sequential quadratic programming (SQP), was utilized to determine the thermal performance and the effective use of fins for diverse values of physical parameters, such as parameter for the moist porous medium, dimensionless ambient temperature, radiation coefficient, power index, in-homogeneity index, convection coefficient, and dimensionless temperature. The results of the designed ANN-TTA-SQP algorithm were validated by comparison with state-of-the-art techniques, including the whale optimization algorithm (WOA), cuckoo search algorithm (CSA), grey wolf optimization (GWO) algorithm, particle swarm optimization (PSO) algorithm, and machine learning algorithms. The percentage of absolute errors and the mean square error in the solutions of the proposed technique were found to lie between to and to , respectively. A comprehensive study of graphs, statistics of the solutions, and errors demonstrated that the proposed scheme’s results were accurate, stable, and reliable. It was concluded that the pace at which heat is transferred from the surface of the fin to the surrounding environment increases in proportion to the degree to which the wet porosity parameter is increased. At the same time, inverse behavior was observed for increase in the power index. The results obtained may support the structural design of thermally effective cooling methods for various electronic consumer devices.

Solidification of nano-enhanced PCM-porous composites in a cylindrical cold thermal energy storage enclosure

Latent thermal energy storage units are extensively used for compensating for the misalignment of energy production and demand. Regardless of the extensive applications of these appliances in the industries, they suffer from the slow progress of phase change, which restricts their great potential. The efforts of the current research are concentrated on using the combination of several enhancement techniques, including the implementation of porous foams, fins, and nanomaterials for pushing the phase change rate of one of these systems towards the desirable speed. For this purpose, first, the influence of container orientation is studied. Then, the freezing process of four different nano-enhanced phase change material (PCM)-porous composites, with porous materials of aluminum, copper, nickel, and graphite is examined. After selecting copper foam as the superior composite for the unit, different foam porosities are tested. It was found that while occupying 3%vol of the container capacity with CuO nanomaterials creates only 24.3% of improvement, spending the same volume on copper foam accelerates the process by 84.6%. The evaluations also indicated that by using copper foam with a porosity of 0.95 and CuO nanomaterials with a concentration of 0.03 at the same time, the phase change rate can be elevated by 92.5%.