Steady Boundary Conditions Research Articles

Optimal human respiratory simulation for exhaled gas based on CFD method.

Human breathing is crucial for studying indoor environments and human health. Computational Fluid Dynamics (CFD) is a key tool for simulating human respiration. To enhance the accuracy of CFD simulations and reduce computation time, a new simulation strategy for human respiration is proposed in this paper. The effects of steady versus unsteady boundary conditions on simulation results were examined. For the unsteady boundary, sinusoidal exhalation velocities and non-inhalation gas were assumed, while the steady boundary involved constant velocities during both exhalation and inhalation phases. The jet center trajectory under different boundary conditions was analyzed and compared with experimental data. Additionally, variations in pollutant dispersion near the mouth under the two boundary conditions were discussed. Furthermore, the paper compared the calculation accuracy, calculation time and memory occupied by a single turbulence model or switching flow character models in human respiration simulation. Differences in exhaled gas vorticity and jet penetration depth across different flow models were identified. Finally, combined with the non-iterative algorithm, the optimal strategy of human respiration simulation was proposed. Results show that under the comprehensive consideration of calculation accuracy, calculation time and memory occupancy, using sinusoidal expiratory boundary conditions combined with the PISO algorithm, with the RNG k-ε model during expiratory phase, and switching into the laminar flow during inspiratory phase, is the optimal strategy of simulating human breathing.

Project Report: Thermal Performance of FIRSTLIFE House

The paper deals with selected thermal properties of a small building that was built during the international student competition Solar Decathlon 2021/2022 and is now part of the Living Lab in Wuppertal. It summarizes the essential information about the overall design of this wooden building with construction and technologies corresponding to the passive building standard. Built-in sensors and other equipment enable long-term monitoring of thermal parameters. Part of the information comes from the building operation control system. The thermal transmittance value for the perimeter wall matches calculated expectation well, even from a short period of time and not at an achievable perfectly steady state boundary condition. The (positive) difference between the calculated values and the measured ones did not exceed 0.015 W/(m2K). It was proven that even for such a small building with a very small heat demand, the heat transfer coefficient can be estimated alternatively from a co-heating test (measured electricity power for a fan heater) and from energy delivered to underfloor heating (calorimeter in heating system). Differences among both measurement types and calculation matched in the range ± 10%. In the last section, the dynamic response test is briefly described. The measured indoor air temperature curves under periodic dynamic loads (use of fan heater) are compared with the simulation results. The simulation model working with lumped parameters for each element of the building envelope was able to replicate the measured situation well, while its use does not require special knowledge of the user. In the studied case, the differences between measured and simulated air temperatures were less than 1 Kelvin if the first two to three days of the test period are ignored due to large thermal inertia. Finally, the measurement campaign program for the next period is outlined.

Boundary conditions in flutter simulations of subsonic, transonic and supersonic blade cascades

Simulations of blade flutter are highly sensitive to undesired wave reflections at inlet and outlet boundaries. A careful treatment of boundary conditions is required to prevent the generation of perturbations. This study is motivated by the need to perform flutter analysis of low-pressure steam turbine blades, for which supersonic inflow conditions may occur in the near-tip region. The exact steady non-reflecting boundary condition (NRBC), the spectral NRBC and a simple isentropic boundary condition are implemented in a time-marching flow solver and applied to turbomachinery flutter simulations covering a wide range of operating conditions. For the first time, the spectral NRBC is applied to a blade flutter simulation with a supersonic inlet and its performance is analysed and compared with other boundary condition formulations. It is shown that an effective non-reflective treatment in the design of the boundary condition is essential for an accurate aeroelastic prediction at all operating conditions, including the subsonic flow regime. The limitation of the exact steady NRBC to spatial modes causes it to perform poorly in some unsteady flow simulations, whereas the spectral NRBC achieves a satisfactory suppression of undesired wave reflections in all investigated cases.

Measurement and prediction of the detachment of Aspergillus niger spores in turbulent flows

Aspergillus niger (A. niger) spores can induce numerous health problems. Once the airflow-imposed drag force on an A. niger spore exceeds its binding force with the colony, the spore is detached. Turbulent flow may considerably increase the spore detachment. No method is currently available for prediction of the drag force on a spore and its detachment in turbulent flows. This investigation measured the turbulent velocities and detachment of A. niger colonies in a wind tunnel. Computational fluid dynamics (CFD) was employed to model an A. niger unit subjected to turbulent flow blowing. The top 1 % quantile instantaneous velocity of the turbulent flow was specified as the steady entry flow boundary condition for solving the peak velocity distribution and the peak drag forces onto spores. The predicted spore detachment ratios were compared with the measurement data for model validation. The results revealed that the spore detachment ratios with a turbulence intensity of 17 % to 20 % can be twice to triple the ratio with a turbulence intensity of approximately 1 %, when the average velocity for blowing remains the same. The proposed CFD model can accurately predict the detachment ratios of the A. niger spores. Environmental ImplicationSome people are sensitive to the Aspergillus niger (A. niger) spores, and excessive exposure can cause nasal congestion, skin tingling, coughing, and even asthma. Turbulent flow can considerably increase the spore detachment, due to the increased airflow-imposed drag force on the spores during turbulence. This investigation developed a numerical model to solve for the peak velocity distribution and the peak drag forces onto spores in turbulent flows to predict the spore detachment. With the numerical tool, the airborne fungal spore concentrations would be predictable, which paves a way for intelligent and precise control of fungal aerosol pollution.

Sediment Compaction in Experimental Deltas: Toward a Meso‐Scale Understanding of Coastal Subsidence Patterns

AbstractWe present the first investigation of subsidence due to sediment compaction and consolidation in two laboratory‐scale river delta experiments. Spatial and temporal trends in subsidence rates in the experimental setting may elucidate behavior which cannot be directly observed at sufficiently long timescales, except for in reduced scale models such as the ones studied. We compare subsidence between a control experiment using steady boundary conditions, and an otherwise identical experiment which has been treated with a proxy for highly compressible marsh deposits. Both experiments have non‐negligible compactional subsidence rates across the delta‐top, comparable in magnitude to our boundary condition relative sea level rise rate of 250 μm/hr. Subsidence in the control experiment (on average 54 μm/hr) is concentrated in the lowest elevation (<10 mm above sea level) areas near the coast and is likely related to creep induced by a rising water table near the shoreface. The treatment experiment exhibits larger (on average 126 μm/hr) and more spatially variable subsidence rates controlled mostly by compaction of recent marsh deposits within one channel depth (∼10 mm) of the sediment surface. These rates compare favorably with field and modeling based subsidence measurements both in relative magnitude and location. We find that subsidence “hot spots” may be relatively ephemeral on longer timescales, but average subsidence across the entire delta can be variable even at our shortest measurement window. This suggests that subsidence rates over a short time frame may exceed thresholds for marsh platform drowning, even if the long term trend does not.

On the theory of fast projection methods for high-order Navier-Stokes solvers

We propose a new framework for the design of fast-projection solvers for the Navier-Stokes equations using Runge-Kutta integrators. The framework uses the full nonlinear equations along with rooted trees and exposes the need to track non-linear advection terms for fourth-order and higher integrators as those introduce irreducible elementary derivatives in the truncation error. The framework is then used to derive approximations to the pressure projection by replacing those with suitable approximations that do not affect formal order of accuracy. The proposed pseudo-pressure approximations are easy-to-implement with some of the variants including parametric coefficients that can be exploited to optimize fast-projection solvers for stability or other desirable properties. In addition, we report approximations for adaptive timestepping. Both the parametric and adaptive timestepping results are being reported for the first time in the literature. The proposed approximations are verified with computations of the full Navier-Stokes equations on two benchmark problems with steady and unsteady boundary conditions and fixed and adaptive timestepping. All calculations agree with the theoretical results and produce the correct formal order of accuracy. The proposed framework lays the foundation for future work on fast-projection methods and can be used to reproduce existing results in the literature.

Numerical simulation of the cavopulmonary connection flow with conduit stenoses of varying configurations

The circulation in the total cavopulmonary connection (TCPC) is a low-energy system which operation and efficiency are subjected to multiple factors. Some retrospective studies report that the abnormal narrowing of vessels in the system, i.e. stenosis, is one of the most dangerous geometric factors which can result in heart failure.In the present study, the effect of varying extracardiac conduit (ECC) stenosis on the hemodynamics in a surrogate TCPC model is investigated using high-fidelity numerical simulations. The efficiency of the surrogate TCPC model was quantified according to the power loss, relative perfusion in lungs and the percentage of conduit surface area with abnormally low and high wall shear stress for venous flow. Additionally, the impact of respiration and asymmetry in the stenosis geometry to the system was examined. The results show that the flow in the TCPC model exhibits pronounced unsteadiness even under the steady initial boundary conditions, while the uneven pulmonary flow distribution and the presence of the ECC stenosis amplify the chaotic nature of the flow. Energy efficiency of the system is shown to strongly correlate with amount of vortical structures in the model and their range of scales. Finally, the study demonstrates that the presence of respiration in the model adds to perturbations in the flow which causes increase in the power loss. Results obtained in the study provide valuable insights on how the ECC stenosis effect the flow in the surrogate TCPC model under different flow conditions.

Technique for calculating streamwise local fluxes in general flows

This paper presents a new technique for calculating microscopic local fluxes that provides a robust and accessible way to obtain the streamwise fluxes in general flows. Flux calculation is one of the fundamental elements in molecular simulations. Several-decades-long research efforts on the subject made significant progresses since the pioneering work of Irving and Kirkwood [J. Chem. Phys, (1950) 18, 817–829]. However, some issues remain regarding the fluxes in the flow direction. The streaming velocity (SV) and the fluxes independent of SV are difficult to manage during computation. For example, the local fluxes and SV that vary in more than one direction are not well represented despite being prevalent in the microscopic phenomena such as nanofluidics, biotechnologies, and energy conversions. The technique presented in this paper is based on the instantaneous microscopic conservation equations and depends only on the total fluxes that include the convective contributions. This allows a calculation of all the fluxes at the end of a simulation run, with no complication arising in terms of defining and collecting SV, pressure tensor, and heat flux vector. Widely-used methods such as the method of planes and volume-average method were adapted, respectively. This study then investigated a planar shear flow in a highly confined channel, where a flow is unknown at the beginning of a simulation, and the controversial streamwise heat flux with no temperature gradient was present. The flow and fluxes were structured, and the streamwise heat flux evolved significantly and slowly over a few tens of nano-seconds even with steady boundary conditions.

Realistic flight conditions on ground: new research facility for cabin ventilation

A new full-scale test bench was developed and set up at the German Aerospace Center in Göttingen to experimentally analyze novel ventilation approaches for aircraft under realistic thermodynamic boundary conditions. The new ground-based test rig represents a modern twin-aisle cabin layout characteristic for long-haul airliners. In addition to having a realistic cabin geometry, it also facilitates the experimental simulation of thermodynamic boundary conditions to study the performance of alternative ventilation concepts for different flight phases (e.g., climbing or cruising). The implemented fuselage elements as well as the floor are temperature controllable. Using this kind of mantle heating/cooling system allows dynamic changes of inner surface temperatures in a range covering the operationally relevant temperature and time scales. With this experimental set-up, a complete flight scenario (i.e., taxiing, climbing, cruising and descent) can be simulated thermodynamically. Thermal manikins were used during the studies to simulate the passenger’s heat impact experimentally. Latest measurement techniques comprising the acquisition of flow velocities, fluid temperatures as well as surface temperatures were used. Based on these data, integral quantities like the mean temperature stratification and mean velocity levels near the manikins, the heat removal efficiency as well as the predicted mean vote and the percentage of dissatisfied passengers were calculated to score the ventilation concepts in terms of passenger comfort for two different operational scenarios under steady boundary conditions.

Validated numerical simulation of airflow in child respiratory airways

Both pulmonary airway geometry and breathing pattern evolve from birth to adulthood. These gradual changes significantly influence airflow dynamics and subsequently particle transport and deposition. Regarding the airway structure, the differences between infants and adults are most profound till 5 years of age. Since that age the child airway geometry can be downsized from adult lungs. The objective of the present work was to investigate airflow patterns in child airways. The digital model of male respiratory airways was downsized to dimensionally correspond to a 5–year old child. Airflow simulations with properly validated RANS k–ω turbulence model were performed under steady inhalation boundary conditions. The inspiratory flow rate was 12.5 L/min. The velocity profiles just upstream of the first bifurcation were validated by Laser–Doppler anemometry (LDA) experiments. A replica of the same geometry as the one used in the simulation was 3D printed and part of the trachea was replaced by a glass tube. LDA measurements in several points upstream of the first bifurcation were carried out. The validated flow patterns were compared to the ones obtained in adult lungs.

Study of the edge thermal bridging effect in vacuum insulation panels: Steady and unsteady-state approaches using numerical and experimental methods

This study presents an experimental and numerical investigation on edge thermal bridges effects in vacuum insulation panels. For this purpose, an experimental campaign was carried out using a guarded hot plate apparatus to determine the linear thermal transmittance between different types of panel joints assemblies. Numerical modelling under steady and unsteady boundary conditions were carried out and compared with the experimental results. Focusing on a VIP suitable for external thermal insulation composite systems (ETICS), a sensitivity analysis regarding different edge protection materials, thickness and panels dimensions were also carried out and discussed. Additionally, the contribution of the point thermal transmittance of mechanical fixing devices was numerically evaluated. Finally, transient thermal simulations are applied to VIP based ETICS in different support walls.The results allowed for the quantification of the influence of the edge thermal bridging effects on equivalent thermal conductivity, as well as on the overall thermal performance of ETICS walls. The size of the panels, edge material and air gaps between panels are key-factors to be considered for minimizing linear thermal bridges in VIP solutions. VIP based ETICS walls showed high thermal delay when compared with a conventional ETICS wall.

A Computational Analysis of Heat Transfer in an Air-Cooled Proton Exchange Membrane Fuel Cell for Unsteady Flow Conditions Using a Reynolds Stress Turbulence Model

Within telecom applications, the air-cooled fuel cell, as a backup power system, has recently been gaining popularity. These fuel cells are cost effective, simple, and additionally they do not require a secondary coolant loop. However, since airflow is used as coolant, the heat generated by the fuel cell limits the current density and thus the power density. A turbulence inducing grid is placed in front of the cathode channel to make the airflow turbulent and hence increase the convective cooling effect from the air. The turbulence inducing grid is placed 2.5mm from the cathode channel since previous studies have shown this distance to be most effective.In this study, a three dimensional CFD analysis on the effect of a transient boundary conditions on the cooling effect of the turbulence grid has been conducted. Special emphasis has been on using the comprehensive Reynolds Stress Model as turbulence model. Additional analysis has been made on the cooling effect of pulsating flow with a period of 10 seconds excluding the turbulence inducing grid. At an electrode heat flux of 2600 W/m2, the results indicate that the convective cooling effect increases when using transient boundary conditions compared to steady state boundary conditions. Furthermore, results show that the start-up time is seven minutes, and the time-averaged peak temperature in the transient case is two degrees Celsius below the peak temperature of the steady state case. The CFD analysis show an additional cooling effect due to accelerated-decelerated flow conditions. Figure 1

Capturing the S-Shape of Pump-Turbines by Computational Fluid Dynamics Simulations Using an Anisotropic Turbulence Model

Abstract Pump-turbines cope very well with modern electricity-market demand, having high operational flexibility and storage capabilities. Nevertheless, dynamic operation of these machines can lead to very challenging transient conditions, depending on the shape of the characteristic. Mechanical integrity can be correspondingly affected. Therefore, assessment of the characteristic during the design phase is of crucial importance. In the past years, different attempts to accurately compute the characteristic under steady and transient conditions have been undertaken using Reynolds-averaged Navier–Stokes (RANS) computational fluid dynamics. While the k–ω shear stress transport (SST) turbulence model has become the reference for machine design, it often fails for conditions close to or around instabilities. Under unstable conditions, which are characterized by continuous unsteady vortex formation, turbulence isotropy as assumed by linear two equation models is no longer the right choice. Accordingly, a turbulence model able to capture anisotropy, explicit algebraic Reynolds stress model (EARSM), has been implemented in an in-house code and used for the computation of the characteristic of various machines, stable and unstable, to assess the model performance. In this paper, computations of three different dynamic pump-turbine operating conditions are presented. Results using steady boundary conditions (BC) in the unstable region as well as transient BC like load-rejection and runaway are computed with EARSM, showing its superiority compared to linear two equation models. The model's capability to capture anisotropic effects—such as the influence of corners—produces more physical flow structures in the vaneless space, which lead to an overall improvement of the predicted stability characteristics.

Spatial and Temporal Changes of Groundwater Storage in the Quaternary Aquifer, UAE

To study the temporal and spatial variations of the groundwater quantity and quality in response to intensive groundwater exploitation from the Quaternary aquifer in UAE, a water budget model with a cell size of one km2 was developed. The available historical records of groundwater levels and salinity have been used to develop the water table and salinity maps of UAE for the years 1969, 2005, 2010, and 2015. The available water resources and soil information system was used to facilitate validity, cogency, and consistency of the groundwater analysis. The spatial analysis module of GIS was used to define the aquifer setting, saturated thickness, aquifer base elevation, effective porosity, and groundwater salinity at each grid cell. The obtained results indicated that the volume of fresh groundwater resources in the Quaternary aquifer in UAE has decreased from 238 km3 in 1969 to around 10 km3 in 2015. A major part of these depleted fresh groundwater resources was replaced by brackish water, and, therefore, the total groundwater storage in this aquifer has only decreased from 977 in 1969 to 922 km3 in 2015, respectively. If the same groundwater exploitation continues, the freshwater storage in the surficial aquifer might be totally depleted in agricultural areas. Most probably, the brackish groundwater resources will be exploited. In such areas, more attention should be devoted to the management of brackish water resources to avoid the exacerbation of the saltwater intrusion problem. Despite the fact that the obtained results indicate the negative impacts of the improper water resources management in a small part of the arid area, the learned lessons are valid for other arid countries, in particular, using the proper steady state boundary conditions for the initial conditions in modeling the available future management alternatives.

Computational Fluid Dynamic Analysis of Flow around Mangrove roots.

The objective of this paper is to study the flow patterns around mangrove roots to understand its significance in coastal risk reduction. A computational model of two-dimensional Pneumatophores mangrove roots is developed, and flow is simulated using ANSYS software with a predefined mathematical model and boundary conditions. Computational fluid dynamic analysis of a two-dimensional, viscous, incompressible, turbulent flow under steady and unsteady boundary condition is performed using the Finite volume method. Detailed velocity profiles, residual plots, pressure distributions, vectors of the velocity magnitude and pressure and velocity at different positions around the mangrove roots are presented to visualize the importance of mangroves in reducing the wave velocity. The simulation outcome confirms that the mangrove roots of mangrove species can reduce the initial velocity of water flow. The flow patterns and flow structures around the root in the mangrove forest establishes precious data in increasing the effectiveness of current breakwater model.

Flow ventricular catheters for shunted hydrocephalus: initial clinical results.

The non-homogenous flow of the cerebrospinal fluid within the ventricular catheter is one of the causative factors in shunt obstructions during the treatment of hydrocephalus. Previously, we studied the flow in ventricular catheters under the steady and pulsatile boundary conditions by means of computational fluid dynamics (CFD) in three-dimensional paradigms. Subsequently, several catheter designs with homogeneous flow patterns were developed out of which one prototype was chosen after a validation study. To test the effectiveness of the flow ventricular catheter in a prospective, multicenter, comparative study. Eligible centers were three pediatric hospitals: two with sole adult practice and one a mixed pediatric-adult. Standard silicone material was used to develop a parametric catheter model with homogenous flow characteristics. The flow catheters were inserted in pediatric (n = 30) and adult (n = 10) patients with all types of hydrocephalus. Simultaneously, regular ventricular catheters were inserted in another 43 control patients in the participating centers. Catheter positioning was standardized according to the Schaumann and Thomale classification. All ventricular catheters had a cephalad grade I or II positioning, and caudally, its extension had a peritoneal location. Programmable valves were utilized in 70% and antisiphon devices in 20% of the cases. Regular differential pressure valves were utilized in the remaining. No case of flow catheter obstruction was identified during a mean follow-up period of 2 years at the time of this writing. There were four catheter obstructions in the control cohort, all pediatric cases, during the first year. Shunt infections occurred in two cases in the control group, while there was one recurrent case of adult ventriculitis in the flow catheter group. This prototype model represents the next generation of ventricular catheters with a homogeneous flow pattern. The flow catheter can be inserted safely in hydrocephalic patients, and this preliminary prospective comparative study showed a possible obstruction-free functionality.

Effect of Blade Row Interaction on Rotor Film Cooling

Abstract The mechanisms of blade row interaction affecting rotor film cooling are identified to make recommendations for the design of film cooling in the real, unsteady turbine environment. Present design practice makes the simplifying assumption of steady boundary conditions despite intrinsic unsteadiness due to blade row interaction; we argue that if film cooling responds nonlinearly to unsteadiness, the time-averaged performance will then be in error. Nonlinear behavior is confirmed using experimental measurements of flat-plate cylindrical film cooling holes, mainstream unsteadiness causing a reduction in film effectiveness of up to 31% at constant time-averaged boundary condition. Unsteady computations are used to identify the blade row interaction mechanisms in a high-pressure turbine rotor: a “negative jet” associated with the upstream vane wake, and frozen and propagating vane potential field interactions. A quasi-steady model is used to predict unsteady excursions in momentum flux ratio of rotor cooling holes, with fluctuations of at least ±30% observed for all hole locations. Computations with modified upstream vanes are used to vary the relative strength of wake and potential field interactions. In general, both mechanisms contribute to rotor film cooling unsteadiness. It is recommended that the designer should choose a cooling configuration that behaves linearly over the expected unsteady excursions in momentum flux ratio as predicted by a quasi-steady hole model.

Background-oriented schlieren technique for two-dimensional visualization of convective indoor air flows

This article focuses on further developments of the background-oriented schlieren (BOS) technique to visualize convective indoor air flow, which is usually defined by very small density gradients. Since the light rays deflect when passing through fluids with different densities, BOS can detect the resulting refractive index gradients as integration along a line of sight. In this paper, the BOS technique is used to yield a two-dimensional visualization of small density gradients. The novelty of the described method is the implementation of a highly sensitive BOS setup to visualize the ascending thermal plume from a heated thermal manikin with temperature differences of minimum 1 K. To guarantee steady boundary conditions, the thermal manikin was seated in a climate laboratory. For the experimental investigations, a high-resolution DLSR camera was used capturing a large field of view with sufficient detail accuracy. Several parameters such as various backgrounds, focal lengths, room air temperatures, and distances between the object of investigation, camera, and structured background were tested to find the most suitable parameters to visualize convective indoor air flow. Besides these measurements, this paper presents the analyzing method using cross-correlation algorithms and finally the results of visualizing the convective indoor air flow with BOS. The highly sensitive BOS setup presented in this article complements the commonly used invasive methods that highly influence weak air flows.

Measurements of thermal Transmittance of an External massive timber wall in-situ and in the Laboratory

The thermal transmittance of an exterior massive timber wall was measured in situ in Appenzell, Switzerland according to the standard ISO 9869-1. The measurements were performed with two different measurement sets in parallel. The measurements started in February and stopped at end of April. The measuring data were analyzed using mean values of the thermal transmittance coefficient and of the thermal resistance following the procedure of ISO 9869-1. In order to clarify if the in-situ measurement results show significant deviations from the measurement results of the thermal transmittance obtained in the laboratory, the thermal transmittance of the identical wall construction was measured in the laboratory of Bern University of Applied Sciences in Biel according to the standard EN ISO 8990 for steady state boundary conditions in a guarded and calibrated hot box. The test results will be presented and the measurement setup will be described. The calculation value of the thermal transmittance coefficient of the massive timber wall according to EN ISO 6946 is U = 0.53 W/(m2K). The test results of the thermal transmittance coefficient, U-value of the wall, measured in the hot box, agreed well within a confidence level of 95 % with the calculated value. The in-situ measurement results of the thermal transmittance coefficient of the two measurement sets differ significantly in the order of 8 % referred to the calculated U-value of the wall as the basic amount. Furthermore, both in situ test results of the U-value of the wall show significant deviations from the calculated U-value up to 27 %.

Experimental validation of a steady periodic analytical model for Breathing Walls

The Breathing Wall behaviour under variable boundary conditions is described by an analytical model based on a one-dimensional porous domain crossed by air and subject to third type steady periodic boundary conditions. To the best of the authors’ knowledge, its experimental validation is not provided in literature.In this work, a new model is derived considering Dirichlet steady periodic boundary conditions. The model is experimentally validated testing a 1 m2 no-fines concrete sample in the Dual Air Vented Thermal Box apparatus, specially improved to replicate dynamic thermal conditions. The experiments show that increasing the air flow velocity across the Breathing Wall from 0 to 12 mm/s enhances thermal coupling between the two environments, namely reduces the wall thermal capacity, with a decrease in the penetration time from 4.3 h to 3 h.The model shows a very good agreement with experimental data when predicting temperature distribution across the domain, with error averages and standard deviations within the thermocouple accuracy after calibration, assumed to be 0.15 ∘C. The lesser yet good agreement concerning conduction heat flux density is explained in terms of accuracy in the measurement of the boundary conditions and critical issues in the heat flow measure itself (i.e. probe thermal resistance, thermal contact, emissivity mismatch).