Thermal Natural Convection Research Articles

Evaluation of the airflow distribution of a vertical air ventilation system in a car cabin using PIV measurements and CFD simulations

The main goal of a ventilation system in the car cabin in general is to guarantee an adequate thermal comfort for all passengers and to enable a good air quality with sufficient air supply into the cabin. Quantifying the indoor air distribution is essential to provide the necessary thermal comfort and the required air quality. The aim of this study is therefore to analyze the subsequent airflow distribution of the vertical air ventilation system presented as a possible solution for future cars with modern interior designs. With the vertical air ventilation concept, air vents are located at the ceiling and floor area of the car cabin, as ceiling and floor regions enable a large-area influx of air into the car cabin and allow accessibility to passengers in every seating position. For the analysis of the airflow distribution of the ventilation system, Particle Image Velocimetry (PIV) measurements have been performed with a test vehicle in a climate chamber under specific conditions. Two different thermal manikins, one heated and the other unheated, have been used in the experiments. The results of the comparison between the two thermal manikins reflect a relatively low to medium impact of the human thermal natural convection on the airflow pattern around the manikin in the different air distribution modes of the vertical air ventilation system. Using the same ventilation settings, numerical simulations have been performed. The results of the numerical simulations are analyzed and compared with the results of the PIV measurements. The developed numerical model shows a good agreement with the experiments. It can hence be used for example in further studies to evaluate the thermal comfort or the air quality of the vertical airflow system as a new ventilation concept for future car interior designs.

Extracting fundamental parameters of 2D natural thermal convection using convolutional neural networks

The Lattice Boltzmann Method (LBM) is an approach for modeling mesoscopic fluid flow and heat transfer, based on modeling distributions of particles moving and colliding on a lattice. Using a perturbative formulation of the Boltzmann equation, it scales to the macroscopic Navier–Stokes equation. We simulate natural thermal convection via LBM in a 2D rectangular box being heated from below and cooled from above, and use the results as training, testing, and generalization datasets to build a deep learning model. GoogLeNet, a convolutional neural network, is used to classify the simulation results based on two parameters: Rayleigh (Ra) and Prandtl (Pr) numbers, from a single snapshot of either the entire modeling field of resolution 1024×1024, or a 224×224 crop. For each fixed Pr in a range from 1 to 128, increasing by a factor of 2, we estimate Ra with an accuracy varying from 40% to 90%, depending on the chosen augmentation strategy. For each fixed Ra in the range from 105 to 109, increasing of a factor 10, the method predicts Pr with a systematically lower accuracy ranging from 30% to 80%. This approach has great potential for industrial applications like being able to control the industrial flow or scientific research on geophysical ones including the transport of heat in the earth’s interiors, ocean, and atmosphere.

The effect of baffles on vertical wall PCM to enhance natural convection

The objective of this study is to enhance convective heat transfer within phase change materials (PCM) using baffles on a vertical wall. PCMs have major drawbacks of low thermal conductivity, high viscosity, and limited natural convection. To address these issues, we investigated a passive approach to enhance natural convection with baffles. The new approach is to arrange multiple baffles with gaps on the opposite side of the heated vertical wall. This placement can minimize vertical temperature difference by blending upward-flowing hot liquid PCM with downward-flowing cold liquid PCM across the gaps and also increase circulating velocity by shortening path of circulation cell through sections divided by baffles. Visualization experiments of shadowgraphy and particle image velocimetry (PIV) were conducted to compare the case with baffle (WB) against the case without baffle (NB). The presence of the baffles lowered the average temperature difference in the horizontal direction by 40%. The WB case reduced the temperature difference in the vertical direction by 50%, compared with the NB case. Furthermore, comparison of the WB with NB showed that at the heat power levels of (4, 6, and 8) W, the convection coefficient increased by up to (28, 34, and 27)%, respectively. Therefore, by changing the internal flow pattern, the baffles on the vertical wall improved convective heat transfer performance.

Thermoelectric convection in a planar capacitor: theoretical studies and experiments in parabolic flights

Thermoelectric convection in a plane capacitor is investigated in a microgravity environment and in the case of the thermal stable and unstable stratification in terrestrial conditions. Energetic analysis shows that in the thermal stable stratification, the thermoelectric convection is delayed while in the thermal unstable stratification, it is enhanced by the Archimedean buoyancy before the latter takes over the dielectrophoretic buoyancy and drives natural thermal convection. An experiment in parabolic flights shows the formation of thermoelectric convection at the end of the microgravity phase.

THERMAL FIELD IN A HORIZONTAL WELL APPLIED TO THE DETERMINATION OF FLUID FLOW BY ACTIVE THERMOMETRY

Today, in the context of falling oil production and increasing water cut, the importance of geophysical control over field development is increasing. A promising method of production logging is active thermometry, it is based on the creation of a thermal disturbance area in the wellbore, for example, due to induction heating of a section of a metal pipe (liner or casing, depending on the design of the well). As a result of heat exchange with a locally heated pipe section, heat marks are formed in the liquid, moving along the wellbore. The article presents the results of physical modeling of thermal processes during local induction heating of a section of a horizontal well. It has been experimentally established that with an induction heater power of about 1 kW and flow rates in the pipe up to 50 m3/day, the heating of the pipe wall reaches 12 K. As part of the experimental studies, the movement of heat marks was monitored using two modules of temperature sensors distributed over the pipe cross section. It is shown that the nature of temperature change in time is determined by the position of the temperature sensor in the pipe section. The greatest thermal anomalies are noted for sensors pressed against the pipe in its upper part, the smallest - for sensors located in the lower part of the pipe. The fluid flow rate in the pipe was estimated from the rate of passage of the heat mark between the temperature modules. It is shown that the calculated flow rate is overestimated relative to the actual one due to the influence of natural thermal convection, which causes the occurrence of a natural convective fluid flow in addition to the forced movement with a given flow rate. A new analytical solution has been obtained for calculating the dynamics of the pipe temperature in the induction heating section, a comparison of the results of calculations using the analytical model with the experimental results showed good agreement. The results of experimental studies can be used in interpreting the results of field logging wells using active thermometry, in particular, the sensitivity of the pipe temperature in the induction heating section to the flow rate can be used to solve inverse problems of estimating the flow rate in a pipe by measuring its surface temperature using the obtained analytical solution.

LBM simulation for combined thermal radiation and natural convection in 2D enclosure with multiple solid blocks

A numerical investigation of conjugate natural convection in a 2D square enclosure with multiple solid blocks, considering the impact of volumetric thermal radiation, was conducted using the lattice Boltzmann method (LBM). The effect of Planck number wall surface emissivity extinction coefficient solid-to-fluid volume fraction and the number of solid blocks on the fluid-structure and heat transfer within the enclosure were analyzed. The numerical model was validated using benchmark problems from the literature, showing good agreement. The results revealed that at and increasing wall surface emissivity significantly increased the Nusselt number, ranging from approximately 51-116% for different wall emissivity values, as compared to scenarios without surface radiation (). On the other hand, reducing χ, Pl, and β improved the heat transfer rate. The results also demonstrated that subdividing the initial block reduced the heat transfer rate depending on the number of blocks and the value of the Planck number. For instance, when 64 solid blocks were present in the cavity and the Nusselt number decreased by 59.36% compared to the case with a lower solid-to-fluid volume fraction (χ = 15%). The parametric analysis provided useful insights for engineering design in the modern construction industry, with possible applications in building block design and energy efficiency enhancements.

Numerical optimization of forced thermal convection in transverse tube bundles based on double-distribution-function lattice Boltzmann method

Forced thermal convection of transverse tube bundles is common in various thermal equipment, such as boiler economizers and air pre-heaters. In this study, the forced thermal convection in transverse tube bundles is simulated based on the double-distribution-function lattice Boltzmann method (DDF-LBM). The coupled lattice BGK (CLBGK) model is applied to construct the algorithm. The tube's normal gradient of temperature is calculated by the generalized four-point bilinear interpolation method. The algorithm is verified by the simulations of the flow at a low Re∞ around a cylinder, natural thermal convection in the cavity, and forced thermal convection in staggered transverse tube bundles. Remax, S*T and S*L are the three most important factors optimization heat transfer efficiency. The range, variance, and significance analyses of the orthogonal test conclude that S*T and Remax have the most significant impact on the evaluation index j and G, and fc, respectively. In Origin 2018, the fitting accuracy of the fitting curve and the original data is judged by Reduced Chi-Sqr, and the error is judged by Adj. R-Square. The present study's conclusions can guide the parameter selection design to obtain the best thermal performance of transverse tube bundles with a lowest economic cost.

Determination of geothermal temperature and temperature gradient via measurements in the production well sump

Data on the geothermal temperature and the temperature gradient of the earth's crust section are necessary for solving a number of fundamental and applied problems. However, the currently used methods for determining the geothermal temperature based on the temperature measured in the wellbore have known disadvantages and can only be used in a small number of wells in the field under study. The article proposes a new method for determining the geothermal temperature and the temperature gradient from the measured temperature distribution in production wells with a long enough sump. It is shown that every other well out of more than four hundred considered wells of oil fields in the Republic of Bashkortostan (Russia) has an appropriate sump. The influence of heat transfer from the working formation, metal casing and natural thermal convection in the borehole fluid on the temperature field in the sump of the production well is studied analytically and numerically. An algorithm for finding an area with undisturbed temperature distribution in the sump of the wellbore is described. The requirements for the choice of a well and corresponding sump section are given, as well as the procedure for the subsequent processing of thermograms, which makes it possible to determine the geothermal temperature and the temperature gradients in the sump. The efficiency of the proposed technique is demonstrated by two cases of field data examples.

Numerical investigation of mixed convection through an infrared-suppression (IRS) device

The flow through an infrared-suppression (IRS) device, installed on a warship, is often subject to various thermal regimes, including forced, natural, and mixed convection. When the ship becomes stationary/idle in the middle of a sea or in a port, mixed convection flow through the IRS device becomes noteworthy. In this paper, we numerically investigate the thermo-fluid characteristics through a cylindrical IRS device in mixed convection regime. Computations are performed for turbulent flow mixed convection with Richardson number in the range 0.1 ≤ Ri ≤ 10 to analyze the entrainment ratio (ER), flow field, and temperature variations in the IRS device. For a parametric study, dimensionless parameters such as nozzle-exit temperature, diameter ratio, nozzle protrusion, and funnel overlap are varied over the range of 1.91 ≤ T* ≤ 2.577, 1.05 ≤ DR ≤ 1.25, −1.5 ≤ NP ≤ 1.5, and − 22% ≤ OL ≤ 22% respectively. Temperature-dependent fluid properties are considered to obtain accurate results at higher temperature scales. The computed ER fairly agrees with the benchmark experimental results. With increase in Ri, the ER rises, whereas the actual mass suction diminishes. The centerline plume temperature at the exit of the IRS device is around 0.53 times the nozzle-exit temperature for Ri = 10, whereas it is almost identical at Ri = 0.1. The optimal Ri (=0.75) is obtained based on the maximum cooling efficiency. Finally, an empirical correlation for the ER is developed as a function of the above pertinent parameters.

Nonisothermal Fluid Flow in a Well during Induction Heating of the Casing String

The distinctive features of the flow velocity and temperature fields of ascending fluid flow in a metal round pipe (round casing string installed in a production well) under the conditions of its local induction heating are studied. The results of investigation are based on numerical solution of the Navier–Stokes equations in the Boussinesq–Oberbeck approximation. The calculations were performed using the Ansys Fluent software package (license ANSYS Academic Research CFD under the agreement with the Bashkir State University dated June 15, 2020). The fluid flow rates of 10 and 50 m3 per day are considered. Such flow rates correspond to the laminar and transitional flow regimes in the casing pipe. It is found that local perturbations of the velocity and temperature fields are presented in the near-wall region of the heated casing. Fluid temperature perturbations reach several Kelvin degrees, the local flow velocity which increases due to natural thermal convection in the near-wall region of the casing string being several times higher than the cross-section-average flow velocity. The occurrence of areas of vortex flow motion over the interval of induction heating due to natural thermal convection is shown.

Solidification performance improvement of phase change materials for latent heat thermal energy storage using novel branch-structured fins and nanoparticles

In the present study, we propose the combination of novel branch-structured fins and Al2O3 nanoparticles to enhance the performance of a phase change material (PCM) during the solidification process in a triple-tube heat exchanger. The inevitable drawback of PCMs is their lower heat conductivity, which can result in a long response time during the phase change process in latent heat thermal storage systems. Therefore, any serious improvement strategy needs an optimized phase change process. A mathematical model for a two-dimensional structure composed of a PCM with paraffin RT82 and Al2O3 nanoparticles that considers the thermal conduction in metal fins, Brownian motion of nanoparticles, and natural convection in a liquid phase PCM is proposed and verified based on experimental results. The impact of various volume fractions and fin layouts on the solidification process is discussed, involving the evolution and deformation of solid–liquid interfaces and distribution of isotherms and average temperature and liquid fraction curves. The results imply that the solidification behaviour can be significantly enhanced by the application of nanoparticles and metal fins. Compared with the inherent structure of the heat exchanger, the solidification time is decreased by 8.5%, 9.3%, and 10.3% for Al2O3 nanoparticles (at 2%, 5%, and 8%, respectively) only and by 83.0%, 80.7%, 80.8%, and 82.9%, respectively, for various fin layouts only. This is attributed to increased heat transfer by thermal conduction and natural convection. It can be concluded that the impact of the use of fins is preferable compared to that for nanoparticles, and the benefit of nanoparticles is limited.

Thermal radiation effect measurement in enclosure calibration

The effect of thermal radiation could be the biggest issue in enclosure calibration. Reducing it by taking accurate measurements can improve the calibration uncertainty or calibration measurement capability (CMC). However, there is still less information related to the measurement procedure that can be taken from references such as DKD-R 5-7: Calibration of Climatic Chambers, DKD-R 5-8: Calibration of Hygrometers for Direct Measurement of Relative Humidity, and KAN Pd-02.04: Pedoman Kalibrasi Enklosur Suhu. Moreover, one of those reference documents suggests a value of 0.35 °C as the standard uncertainty contributed by thermal radiation for enclosure temperatures up to about 30 °C above ambient. This large value can be understood as an attempt to produce secure uncertainty since it is not measured directly. Therefore, this study describes the detailed measurement of the effect of thermal radiation. Two enclosures, which are an oven and a climatic chamber, are used as the samples. The oven represents an enclosure with natural thermal convection while the climatic chamber represents an enclosure with flowing air at a certain relative humidity. The thermal radiation effect is measured by two small PRTs class A with a diameter of 3 mm and length of 15 mm. Those PRTs are wrapped in aluminum foil to have low emissivity (ɛ=0.4) and one of them is then painted by Nextel 811-21 to have high emissivity (ɛ=0.97). The resistance outputs from the PRTs are measured by 34401A 6½ Digital Multimeter manufactured by Keysight. Before being used, those PRTs were calibrated in a stirred bath having uncertainty U=0.06 °C with a confidence level of 95 % and coverage factor k=2. The temperature range for the oven is from 60 °C to 140 °C while for the climatic chamber is from 40 %rh to 90 %rh at 20 °C and is from 40 %rh to 90 %rh at 25 °C. A mathematical model is proposed and the results are presented graphically where for the oven the higher temperature is the higher the thermal radiation effect, ranging from ±0.1 °C to ±0.4 °C. Variation of relative humidity inside the climatic chamber does not change the thermal radiation effect since the difference is 0.05 °C which is still within the uncertainty of PRTs

The study of heat exchange processes during induction heating of the casing string in relation to the determination of behind-the-casing flows

One of the promising methods of geophysical survey of existing wells is active thermometry. The technology for conducting research using this method includes induction heating of a section of a metal casing string, registration and analysis of temperature changes in the range of induction exposure. As a result of heat exchange with the heated section of the column, a thermal disturbance is created in the fluid flow moving inside the column or in the behind-the-casing flow channel. The analysis of non-stationary temperature in the process of induction action allows solving actual practical problems, for example, determining the presence of fluid overflows in the space behind the casing string. In this work, on the basis of numerical simulation, the features of the formation of a temperature field in the process of inductive heating of the casing string are studied in relation to the determination of behind-the-casing fluid flows. Numerical simulation was performed using the Ansys Fluent software package. Fluid movement in the well is described by the Navier–Stokes equation in the Boussinesq–Oberbeck approximation, and its temperature is calculated taking into account forced and free convection. To calculate the temperature in the inductor, casing string, rocks and cement sheath, a non-stationary heat equation is used. The application of induction heating in diagnosing behind-the-casing flows in the sump, localized below the working perforated formations, in the annular space between the casing string and the cement ring is considered. The distribution curves of the cross-sectional average temperature in the casing string body in the induction heating interval at different flow rates in the casing cross-flow channel are plotted. It is shown that with an increase in the volume flow in the overflow channel, the maximum heating of the column decreases due to more intense heat transfer to the flow in the overflow channel. It has been established that the temperature curves show a “pull” of temperature (temperature disturbances in the body of the casing string propagate in the direction of flow in the overflow channel), the value of which increases with the flow rate in the overflow channel. It is shown that the temperature “pull” (the distance over which the thermal disturbance propagates) during upward flow exceeds the “pull” during downward flow, which is due to the influence of natural thermal convection in the fluid inside the casing string. On the example of the modeling conditions adopted in the work, it was found that up and down flows of more than 0.5 m3/day can be reliably determined from temperature measurements during the induction effect.

A model for a set of porous fins on a long rotating cylinder considering thermal radiation and natural convection

This article proposes a method to estimate the heat transfer and temperature distribution from a porous fin placed on a constantly rotating long cylinder with a hexagonal cross section. Moreover, both radiation and natural convection are considered, as well as radiation interchange between the cylinder and the fin and among the porous fins themselves, giving rise to an Integro-Differential problem. Time-averaged thermal properties are employed since the proposed problem is periodic. The numerical simulation is validated by comparing three different numerical methods: Finite Difference Method (FDM), Finite Volumes Method (FVM), and Spectral Collocation Method with Chebyshev interpolation polynomials (CGL). The three methods demonstrated good agreement among themselves. They provided results according to the existing literature concerning heat transfer and temperature distribution on porous fins, such as showing that convection, as the convective parameter grows from 0 to 10, can quickly become the dominant mode of heat transfer instead of the radiation parameter, which ranged from 0 to 50. The impact on the temperature at the tip ranged from less than 4% to 18.9%, depending on the changes made to thermal and physical parameters under similar conditions. The dimensionless temperature stayed in the stipulated variation from 0 to 1.

A novel method to concurrently enhance heat conduction and natural convection inside PCM thermal buffer

A thermal buffer filled with phase change materials (PCM) can effectively prevent the intermittently working electronic devices from overheating and prolong the working time of the disposable electronic devices. This paper reported a novel composite PCM consisting of low-melting-temperature alloy bars embedded in pure paraffin that can concurrently improve thermal conductivity and natural convection during melting. Moreover, the effects of heat flux, filling height, and alloy mass fraction on the transient temperature of electronic devices and the effective protection time of thermal buffer were discussed experimentally. The results demonstrated that the heat conduction in stage one was enhanced by embedding alloy bars in pure paraffin, meanwhile the dripping of the alloy droplets in stage two not only enhanced the intensity of natural convection but also significantly delayed the increase of surface temperature. Moreover, correlations with a maximum error of 46∼126 s were obtained to predict the matching status between the thermal buffer and electronic devices, the effective protection time, etc., which was expected to guide the design of thermal buffers. In the future, some efforts should be made to alleviate the mismatching conditions, such as disturbing the boundary layers of natural convection by the elastic potential energy of spring or clockwork, etc.

Quantitative measurement of natural thermal convection temperature field based on color stripe background oriented schlieren (CSBOS)

In this study, a new color stripe background oriented schlieren (CSBOS) was proposed. Through multiple experiments, the oblique stripes with color alternating arrangements were selected to draw the background pattern, and the natural thermal convection temperature fields of premixed flame combustion in butane laminar flow with different equivalence ratios were analyzed and reconstructed. A color stripe background oriented schlieren experimental platform was built to collect images of the natural thermal convection field above the butane flame, which can improve the accuracy and spatial resolution, and analyze the influence of different equivalence ratios on the flow field morphology and temperature distribution. The root mean square error (RMSE) between the temperature reconstructed by CSBOS and the temperature measured by invasive measurement (the flow field is not destroyed) is 5.26 at different equivalence ratios, and the maximum measurement error between the reconstructed flow field temperature distribution and the contact measurement is only 2.7%, indicating that CSBOS can accurately reconstruct the temperature of the natural thermal convection field.

Numerical investigation of thermal losses within an internal gear train submerged in a multiphase flow and enclosed in a rotating casing

This paper presents results of a numerical study of thermal losses generated within an internal gear train consisting of a pinion and an annular gear. The gear train is submerged in a multiphase flow of Air and Oil and enclosed within a horizontal rotating cylinder (casing) attached to the annular gear. The casing rotates at a constant speed and exchanges heat through thermal radiation and natural convection to the ambient air. The study has been carried out using KISSsys and KISSsoft computer software. Numerical results have been validated using published experimental data. The maximum deviation is about 9.3%. The effects of several operating parameters; including the casing rotational speed (N), the torque (ζ) and the oil level (OV) on the various thermal losses generated within the gear train have been investigated. The effects of N, ζ and OV have been investigated in the following ranges: 20–160 rpm, 13–100 N.m, and 0–100%, respectively. The types of thermal losses considered in the present study are the churning, the meshing and the bearing losses. The gear ratio used in the present study is 4.45, therefore, the pinion gear rotational speed varied from 90 to 712 rpm. The present results indicated that increasing the rotational speed or the torque increases the thermal losses within the gear train. Increasing the oil level leads to an increase in the churning losses, up to a specific value of OV of about 31%, above which churning losses remained constant. The oil level at the 31% OV value is the oil level required to just submerge the pinion gear. Increasing the casing rotational speed enhanced the rate of heat transfer to the ambient air which improved the overall thermal performance of the gear train by about 12% at N = 460 rpm, compared to the stationary casing case.

Entropy-based analysis and economic scrutiny of magneto thermal natural convection enhancement in a nanofluid-filled porous trapezium-shaped cavity having localized baffles

This article presents a modeling approach to predict the thermal natural convection inside a porous trapezium-shaped zone with baffles installed on the adiabatic side-walls. The cavity is filled with nanofluid and exposed under the effect of a magnetic field. The equations which govern the phenomenon have been solved numerically. For various configurations of the installed baffles, temperature field, the flow structure, heat exchange rate, and entropy production have been characterized for sundry figures of parameters i.e. Rayleigh (Ra), Hartmann (Ha), Darcy (Da), material’s porosity (ϵ), and nanoparticles’ concentration (ϕ). In addition, a cost–benefit analysis of the convection enhancement process within the system based on nanomaterials has been proposed. It has been ascertained that rising Ra, Da, and ϵ while lowering Ha improved the convective nanofluid flow. The influence of porous medium properties (material's porosity and permeability) on the convective flow intensity is more effective at moderate Ra. The average cooling rate increases with rising Ra, Da, and ϕ and declining Ha and ϵ. Moreover, obtained results characterize a positive economic feasibility of utilizing nanomaterials to improve thermal natural convection in the presence or absence of a magnetic field.

Heat Transfer under Magnetohydrodynamics Flow of Nanofluids Past an Inclined Plate with Non Uniform Boundary Conditions

This paper deals with natural thermal convection combined with the mass transfer of nanoparticles occurring in the boundary layers of a nanofluid subjected to magnetohydrodynamics. The wall consists of an inclined plate is considered according to a temperature as well as the volume fraction of the nanoparticles varying as the power of the axial coordinate. In addition, internal heat generation/absorption is taken into account in the mathematical formulation. The governing partial differential equations based on Buongiorno's approach are transformed into a set of ordinary differential equations. The two-level method of no-similarity equations is used to achieve higher accuracy. The whole calculation procedure is implemented using a limit value problem program written according to the Matlab computer language that applies the Lobbato IIIa finite difference method. The obtained results have revealed that small variations of the boundary conditions with the axial coordinate become very significant on the local Nusselt number and the local Sherwood number for nanoparticles. Moreover, a better heat transfer has been obtained with a larger S. However, a trade-off between desired heat transfer rate and level of reduced skin friction should be scheduled.

Analysis of the local non-equilibria on the heat transfer and entropy generation during thermal natural convection in a non-Darcy porous medium

This paper addressed new and unique information on the influence of local thermal non-equilibrium (LTNE) effects on heat exchange and entropy generation during thermal-free convection in a non-Darcy porous domain. The simplest configuration was considered, which consisted of a square cavity in which the steady-thermal-free convection motion is generated by maintaining the vertical sidewalls at different and constant temperatures. The Darcy-Brinkman-Forchheimer design has been adopted. The governing equations, which include the two energy equations for the fluid and solid phases, along with momentum equations in their dimensionless form, are solved using the finite volume computational approach. Due to the application of two different heat transport equations under the LTNE modeling technique, sources of entropy generation owing to thermal diffusion in the fluid phase and in the solid phase in addition to the entropy generation owing to viscous dissipation were identified. Maps of the distribution pattern of LTNE sources were also visualized. Furthermore, to assess and compare the thermal diffusion irreversibility in the two components of the porous structure, for the first time, we introduced and examined a new parameter (Ty), which is the ratio of the thermal entropy generation rate in the fluid phase to that in the solid phase.