Simulation Of Heat Flow Research Articles

IMatTOUGH: An open-source Matlab-based graphical user interface for pre- and post-processing of TOUGH2 and iTOUGH2 models

TOUGH2 and iTOUGH2 are powerful models that simulate the heat and fluid flows in porous and fracture media, and perform parameter estimation, sensitivity analysis and uncertainty propagation analysis. However, setting up the input files is not only tedious, but error prone, and processing output files is time consuming. In this study, we present an open source Matlab-based tool (iMatTOUGH) that supports the generation of all necessary inputs for both TOUGH2 and iTOUGH2 and visualize their outputs. The tool links the inputs of TOUGH2 and iTOUGH2, making sure the two input files are consistent. It supports the generation of rectangular computational mesh, i.e., it automatically generates the elements and connections as well as their properties as required by TOUGH2. The tool also allows the specification of initial and time-dependent boundary conditions for better subsurface heat and water flow simulations. The effectiveness of the tool is illustrated by an example that uses TOUGH2 and iTOUGH2 to estimate soil hydrological and thermal properties from soil temperature data and simulate the heat and water flows at the Rifle site in Colorado.

Evaluating geothermal and hydrogeologic controls on regional groundwater temperature distribution

AbstractA one‐dimensional (1‐D) analytic solution is developed for heat transport through an aquifer system where the vertical temperature profile in the aquifer is nearly uniform. The general anisotropic form of the viscous heat generation term is developed for use in groundwater flow simulations. The 1‐D solution is extended to more complex geometries by solving the equation for piece‐wise linear or uniform properties and boundary conditions. A moderately complex example, the Eastern Snake River Plain (ESRP), is analyzed to demonstrate the use of the analytic solution for identifying important physical processes. For example, it is shown that viscous heating is variably important and that heat conduction to the land surface is a primary control on the distribution of aquifer and spring temperatures. Use of published values for all aquifer and thermal properties results in a reasonable match between simulated and measured groundwater temperatures over most of the 300 km length of the ESRP, except for geothermal heat flow into the base of the aquifer within 20 km of the Yellowstone hotspot. Previous basal heat flow measurements (∼110 mW/m2) made beneath the ESRP aquifer were collected at distances of >50 km from the Yellowstone Plateau, but a higher basal heat flow of 150 mW/m2 is required to match groundwater temperatures near the Plateau. The ESRP example demonstrates how the new tool can be used during preliminary analysis of a groundwater system, allowing efficient identification of the important physical processes that must be represented during more‐complex 2‐D and 3‐D simulations of combined groundwater and heat flow.

Demonstration of a high repetition rate capillary discharge waveguide

A hydrogen-filled capillary discharge waveguide operating at kHz repetition rates is presented for parameters relevant to laser plasma acceleration (LPA). The discharge current pulse was optimized for erosion mitigation with laser guiding experiments and MHD simulation. Heat flow simulations and measurements showed modest temperature rise at the capillary wall due to the average heat load at kHz repetition rates with water-cooled capillaries, which is promising for applications of LPAs such as high average power radiation sources.

Lattice Boltzmann simulation of heat and fluid flow in 3D cylindrical heat exchanger with porous blocks

Inserting porous blocks into heat exchange pipe as a technology for heat transfer enhancement is widely used in engineering applications. In order to get the optimal heat transfer efficiency, this work is devoted to the numerical investigation of heat and fluid flow in cylindrical pipe with porous blocks using lattice Boltzmann method. The effects of several parameters, such as the width and height of the porous blocks, the distance between two adjoining porous blocks, Darcy number and porosity on fluid flow and temperature field are investigated. The numerical results indicate that the heat transfer effect caused by the height variation of porous block is more obvious compared with the other parameters.

Mathematical Simulation of Heat Flows in a Building in case of Heat Supply Failure

Investigation of possible thermal modes in a building in case of heat supply failure has been carried out using the developed prognostic complex model. Time characteristics of processes of temperature reduction to critical values (which characterize the conditions of failure of a district heating system) in premises of various configurations have been defined. The influence of heating system structural features and the coolant circulation process at the time of its cooling to critical temperatures has been determined. Mathematical laws, which allow predicting the main parameters of building’s useful life according to the heating mode, have been derived. The specific numerical values of investigated processes for climatic conditions with outdoor temperatures from minus 10 °С to minus 40 °С have been given.

Investigation on the Designing of the Metal Diaphragm in Pulse Solid Rockets

To achieve the designing formula of a hard pulse separation device made by a metal diaphragm in a double-pulse solid rocket motor, the fracture mechanics theory and large deflection theory of a circular plate were used to establish the calculating formula of the stress intensity factor of the prefabricated gap on one side of the pulse separation device. The three-dimensional virtual crack-closure technique was used to compute the stress intensity factor of the prefabricated gap. The numerical results agreed with the results calculated by the formula very well. The intensity theory of a circular plate with a multihole was used to establish the checking method of the support strength. The results of the checking method were higher than the numerical results. The checking method was propitious in improving the designing, carrying capacity of the pulse separation device. To verify the accuracy of the formula, the validation tests were carried out. The average opening pressure of the tests of the pulse separation device was 5% higher than the numerical and formula results. Heat flow simulation tests were used to check the carrying capacity of the pulse separation device, and the structure of support remained intact. The results showed that the designing methods in this paper can be applied to design a double-pulse solid rocket motor directly.

A Method Of Calculating Thermal Diffusivity And Conductivity For Irregularly Shaped Specimens In Laser Flash Analysis

AbstractThe Low Temperature Joining Technique(LTJT) using silver compounds enables to significantly increase the thermal conductivity between joined elements, which is much higher than for soldered joints. However, it also makes difficult to measure the thermal conductivity of the joint.The Laser Flash Analysis(LFA) is a non-intrusive method of measuring the temperature rise of one surface of a specimen after excitation with a laser pulse of its other surface. The main limitation of the LFA method is its standard computer software, which assumes the dimensions of a bonded component to be similar to those of the substrate, because it uses the standard Parker’s formula dedicated for one-dimensional heat flow. In the paper a special design of measured specimen was proposed, consisting of two copper plates of different size joined with the sintered silver layer. It was shown that heat properties of these specimens can also be measured after modifying the LFA method. The authors adapted these specimens by masking the false heat signal sourced from the uncovered plate area. Another adaptation was introducing a correcting factor of the heat travel distance, which was calculated with heat-flow simulations and placed into the Parker’s formula. The heat-flow simulated data were compared with the real LFA measurement results, which enabled estimation of the joint properties,e.g.its porosity.

Thermal and Residual Stress Analysis on A36 Steel Plate Brazed with a Known Volume of Zn50 Brazing Alloy (Filler Metal)

The simulation of heat flow, residual stress, and thermal distortion developed in A36 steel plate using a known volume of Zn50 brazing alloy for torch brazing technique is presented in this paper. FEHT software and GTstrudle codes were used for the heat transfer and residual stress simulation, respectively. The result of the heat flow simulation showed excessive cooling at the joints corner following convective heat loss to the ambient and maximum heat flux gradient thereby making the joint predisposed to underfill. Also the von misses stress and strain distribution in the plate showed that the residual stress is compressive and is limiting at 1800 N/mm2, localized in the joint. This is a basic understanding for impedance to thermally induced cracking.

Impact of the Properties of a Green Roof Substrate on its Hydraulic and Thermal Behavior

Green roofs integrate vegetation into infrastructures to reach benefits that minimize negative impacts of the urbanization. Green roofs use artificial soils (substrates) that have an improved performance compared to natural soils. In this work, we characterized four substrates in terms of their hydraulic and thermal properties, and performed numerical simulations of heat and fluid flow to study the effect of these properties on green roof performance. Simulation results show that the green roof behavior strongly depends on substrate properties and on moisture content prior to a rainstorm, highlighting the need of dynamic biophysical models for design/maintenance of green roofs.

Estimation of Temperature Conductivity Coefficient Impact upon Fatigue Damage of Material

In the paper we consider the peculiarities of adhesive wear of cutting tools. Simulation of heat flows in the cutting zone showed that, as thermal conduction and heat conductivity of tool material grow, the heat flows from the front and back surfaces to tool holder will increase and so, the temperature of the contact areas of the tool will lower. When estimating the adhesive wear rate of cemented-carbide tool under the cutting rates corresponding to the cutting temperature of up to 900 °C, it is necessary to take the fatigue character of adhesive wear into consideration. The process of accumulation and development of fatigue damage is associated with micro- and macroplastic flowing of material, which is determined by the processes of initiation, motion, generation, and elimination of line defects - dislocations. Density of dislocations grows with increase of the loading cycles amount and increase of load amplitude. Growth of dislocations density leads to loosening of material, formation of micro- and macrocracks. The heat capacity of material grows as the loosening continues. In the given paper the authors prove theoretically that temperature conductivity coefficient which is associated with heat capacity of material, decreases as fatigue wear grows.

Low Energy Direct Contact Membrane Desalination: Conjugated Heat and High Fidelity Flow Simulation

The steady state performance of Low Energy Direct Contact Membrane Distillation (DCMD) is numerically investigated. A case of uniform flow is considered entering both the feed side at a temperature above the permeate side. The developed fluid model is governed by the Navier-Stokes flow and energy equation in a coupled conjugate heat transfer formulation to the flow and the solid membrane. Across the membrane and depending on the membrane parameters including permeability, thickness, pore size and conductivity the local temperature difference creates a driving pressure gradient responsible of evaporation part of the feed adjacent to the membrane surface, transport it through the pores, and condense it at permeate side through the hydrophobic membrane. The membrane's coefficients of DCMD membrane is evaluated along with the mass flux, heat flux, temperature polarization factor, and thermal efficiency. In this paper, two flow configurations are studied: Counter and Parallel flow. A parametric study is conducted incorporating velocity combinations and concluding an optimum configuration in terms of DCMD efficiency, mass flux. In view of these plausible results, a sensitivity study to the flow rates is carried out to gain better insight to the temperature polarization, heat flux including convective, conductive and the associated latent heat as well as in understanding its effect on the process metrics and yield.

New thermal parameters identification approach applied to the thermal renovation of buildings

In this article, a new technique for identification of the thermal parameters of simplified mathematical model for an existing building is presented. This thermal simulation model allows the performance analysis of a building. The model is based on the electrical analogue with resistances and capacitors (RC) used for the simulation of the unsteady heat flow in the building. The model is validated with the results of a TRNSYS simulation. The obtained accuracy lies within a 7% interval. This tool is then used in an inverse method in order to determine the value of the electrical (RC) equivalent thermo physical characteristics of the building envelope. The model for the determination is based upon the least squares method, between the indoor measured temperatures and the model response, using an inverse iterative algorithm (Reflective Newton).

A spectral model for transient heat flow in a double U-tube geothermal heat pump system

This paper introduces a semi-analytical model based on the spectral analysis method for the simulation of transient conductive-convective heat flow in an axisymmetric shallow geothermal system consisting of a double U-tube borehole heat exchanger embedded in a soil mass. The proposed model combines the exactness of the analytical methods with an important extent of generality in describing the geometry and boundary conditions of the numerical methods. It calculates the temperature distribution in all involved borehole heat exchanger components and the surrounding soil mass using the fast Fourier transform, for the time domain; and the complex Fourier and Fourier-Bessel series, for the spatial domain. Numerical examples illustrating the model capability to reconstruct thermal response test data together with parametric analysis are given. The CPU time for calculating temperature distributions in all involved components, pipe-in, pipe-out, grout, and soil, using 16,384 FFT samples, for the time domain, and 100 Fourier-Bessel series samples, for the spatial domain, was in the order of 3 s in a normal PC. The model can be utilized for forward calculations of heat flow in a double U-tube geothermal heat pump system, and can be included in inverse calculations for parameter identification of shallow geothermal systems.

Human Milk Warming Temperatures Using a Simulation of Currently Available Storage and Warming Methods.

Human milk handling guidelines are very demanding, based upon solid scientific evidence that handling methods can make a real difference in infant health and nutrition. Indeed, properly stored milk maintains many of its unique qualities and continues to be the second and third best infant feeding alternatives, much superior to artificial feeding. Container type and shape, mode of steering, amount of air exposure and storage temperature may adversely affect milk stability and composition. Heating above physiological temperatures significantly impacts nutritional and immunological properties of milk. In spite of this knowledge, there are no strict guidelines regarding milk warming. Human milk is often heated in electrical-based bottle warmers that can exceed 80°C, a temperature at which many beneficial human milk properties disappear. High temperatures can also induce fat profile variations as compared with fresh human milk. In this manuscript we estimate the amount of damage due to overheating during warming using a heat flow simulation of a regular water based bottle warmer. To do so, we carried out a series of warming simulations which provided us with dynamic temperature fields within bottled milk. We simulated the use of a hot water-bath at 80°C to heat bottled refrigerated milk (60ml and 178 ml) to demonstrate that large milk portions are overheated (above 40°C). It seems that the contemporary storage method (upright feeding tool, i.e. bottle) and bottle warming device, are not optimize to preserve the unique properties of human milk. Health workers and parents should be aware of this problem especially when it relates to sick neonates and preemies that cannot be directly fed at the breast.

3D structural and stratigraphic model of the Perth Basin, Western Australia: Implications for sub-basin evolution

The history of rifting and breakup of eastern Gondwana is recorded by the development and fill of the Perth Basin in Western Australia. Knowledge of the structural architecture and stratigraphic geometry of the Perth Basin is essential to understand the evolution of the Western Australian margin and its applications to hydrocarbon and geothermal prospects, and effective aquifer management. This study integrates existing, publicly available geological, gravity, magnetic and digital elevation data to develop the first refined, regional structural and stratigraphic interpretation of the entire onshore and offshore Perth Basin, Western Australia. This new 3D model offers formation depth and thickness predictions in areas of sparse or no data. The model shows significant heterogeneity in the preserved formation thicknesses and depths at both local and regional scales. These differences may have resulted from differential subsidence and/or differential exhumation, but the formation geometries alone cannot distinguish between these two models if any erosion has occurred. Only the Lower to Middle Jurassic stratigraphy has been minimally eroded and thereby records the net subsidence. This stratigraphic interval shows that subsidence was broadly hinged from south to north, with a greater subsidence rate in the southern and central Perth Basin. Localised differences in thicknesses across adjacent sub-basins were likely controlled by differential displacement along sub-basin bounding faults during subsidence and, subsequently, during exhumation episodes. This new 3D model of the entire Perth Basin provides a framework for numerical simulations of fluid and heat flow and large-scale tectonic analysis, such as stratigraphic forward modelling of the southwestern Australian margin.

Hydrothermal fluid migration and brine pool formation in the Red Sea: the Atlantis II Deep

Numerical heat and fluid flow simulations of the Atlantis II Deep in the Red Sea were conducted to investigate the development, migration, and discharge of hydrothermal fluids into a submarine depression and determine the conditions necessary to form a brine pool. High-salinity fluids are predicted to form by leaching Miocene evaporates, migrate and convect within young oceanic crust, and discharge onto the seafloor. Predicted fluid discharge temperatures (T max, 301 °C), discharge fluid velocities (V max, 0.09 m/s), and salinities (S max, 21 wt%) increase over time and reach values comparable to modern seafloor observations. Established convection patterns and discharge behavior are robust and are not greatly affected by geometry of rock property changes. Modeling results were used to calculate the minimum conditions for hydrothermal fluids from a developing hydrothermal system to mix with seawater, reverse buoyancy, and begin to form a brine pool in a submarine depression. Under conditions encountered on the seafloor (T, 25–300 °C; S, 5–25 wt%), fluid mixtures predicted to pond on the seafloor range from late in the mixing process (99 %) at low temperatures (T, 26 °C) to much earlier (36 % mixing) at higher temperatures (T, 94 °C). A model of brine pool evolution is proposed that describes the processes and conditions necessary to initiate brine pool formation and compares formation conditions with accumulated ore material in the Atlantis II Deep and other locations.

Numerical simulation of bare soil water and heat flow under an automated irrigation system

Modern irrigation techniques use automated systems where irrigation schedules are controlled according to certain criteria. The objective of this study is to numerically estimate irrigation events, water content and temperature distributions, evaporation, drainage, and soil water under closed loop automated irrigation systems of a bare soil. The automated irrigation system is activated and deactivated according to the water content value. The governing equations for transient one-dimensional liquid water flow and heat transfer of unsaturated porous media are applied. The energy balance equation at the soil surface is used as an upper boundary condition based on measured meteorological data of Jeddah City. The results show that the current procedure can be applied to simulate different variables under automated irrigation systems. The water content shows periodic behavior, as well as time lags and decreases in amplitude with soil depth. The timing of applied irrigation has an important impact on evaporation and soil temperature. Applying irrigation water during the daytime leads to increased evaporation. The soil surface temperature decreases suddenly when water is supplied in the afternoon, while a slight increase is observed when irrigation is applied at midnight.

Development of magneto-thermal lattice Boltzmann heat and fluid flow simulation

In this study, magneto-thermal lattice Boltzmann model is developed and heat transfer enhancement is investigated for a porous media heat exchanger. First, two models of thermal LBM are discussed in terms of its precision and applicability to magneto-thermal LBM including tolerance range of computational parameter. The implemented magneto-thermal LBM is then validated by convection in a cubic enclosure comparing with finite difference computation. The incompressibility limit of magneto-thermal LBM is additionally discussed. Finally, the effect of magnetic field on a flow through heated porous media is numerically investigated. It is found that, the magneto-thermal force is effective at the stagnant region inside the porous media to enhance the heat transfer. In a macroscopic view, the heat transfer enhancement is found in overall region. The effect becomes remarkable at low Reynolds number flow. Since its effect is aligned on a curve of Nusselt–Reynolds relation, the magnetic effect obviously found to assist the main flow.

Heat accumulation in ultra-short pulsed scanning laser ablation of metals.

High average laser powers can have a serious adverse impact on the ablation quality in ultra-short pulsed laser material processing of metals. With respect to the scanning speed, a sharp transition between a smooth, reflective and an uneven, dark ablated surface is observed. Investigating the influence of the sample temperature, it is experimentally shown that this effect stems from heat accumulation. In a numerical heat flow simulation, the critical scanning speed indicating the change in ablation quality is determined in good agreement with the experimental data.

Numerical 3-D heat flow simulations on double-pass solar collector with and without porous media

A transient 3-D mathematical model for double-pass solar collector with porous media in the lower channel has been developed. Numerical simulations model based on setting mass, momentum and energy balances on finite volumes method are carried out. The governing equations inside the two channels, together with the energy equation in the absorber, insulating and glass cover walls were solved iteratively in a segregated manner. Effects of porosity (70-90 %), mass flow (0.03-0.07 kg/s), solar intensity (514-714 W/m2) and spacing glassabsorber-insulation (7-10 cm) on the dynamic and thermal behaviors of the double-pass solar collector with and without porous media have been discussed. The study concluded that the presence of the porous media at the bottom of the absorber is the best configuration and allow increasing the outlet temperature