Finite Element Heat Research Articles

Early-stage hypogene karstification in a mountain hydrologic system: A coupled thermohydrochemical model incorporating buoyant convection

[1] The early stage of hypogene karstification is investigated using a coupled thermohydrochemical model of a mountain hydrologic system, in which water enters along a water table and descends to significant depth (∼1 km) before ascending through a central high-permeability fracture. The model incorporates reactive alteration driven by dissolution/precipitation of limestone in a carbonic acid system, due to both temperature- and pressure-dependent solubility, and kinetics. Simulations were carried out for homogeneous and heterogeneous initial fracture aperture fields, using the FEHM (Finite Element Heat and Mass Transfer) code. Initially, retrograde solubility is the dominant mechanism of fracture aperture growth. As the fracture transmissivity increases, a critical Rayleigh number value is exceeded at some stage. Buoyant convection is then initiated and controls the evolution of the system thereafter. For an initially homogeneous fracture aperture field, deep well-organized buoyant convection rolls form. For initially heterogeneous aperture fields, preferential flow suppresses large buoyant convection rolls, although a large number of smaller rolls form. Even after the onset of buoyant convection, dissolution in the fracture is sustained along upward flow paths by retrograde solubility and by additional “mixing corrosion” effects closer to the surface. Aperture growth patterns in the fracture are very different from those observed in simulations of epigenic karst systems, and retain imprints of both buoyant convection and preferential flow. Both retrograde solubility and buoyant convection contribute to these differences. The paper demonstrates the potential value of coupled models as tools for understanding the evolution and behavior of hypogene karst systems.

Thermoelectric Powered Wireless Sensors for Dry-Cask Storage

This paper describes using thermoelectric generators to power wireless sensors to monitor spent nuclear fuel during dry-cask storage. OrigenArp was used to determine the decay heat of the spent fuel at different times during the service life of the dry-cask. The Engineering Equation Solver computer program modeled the temperatures inside the dry-cask during its service life. The temperature distribution of a thermoelectric generator and heat sink was calculated using the computer program Finite Element Heat Transfer. From these temperature distributions the power produced by the thermoelectric generator was determined as a function of the service life of the dry-cask. To investigate the ability to provide wireless signal transmission using this power source, CST Microwave Studio was used to determine the scattering parameter S2,1 for a horizontal dry-cask. Important parameters that can influence the transmission of the signal are antenna orientation, antenna placement, and transmission frequency. This analysis estimates that a thermoelectric generator can produce enough power for a sensor to function and transmit data from inside the dry-cask throughout its service life.

Effect of protein denaturation degree on texture and water state of cooked meat

We prepared cooked meat with varied denaturation degrees that were predicted based on 3D finite element heat transfer analysis and reaction kinetics. Using a meat sample with a clear denaturation distribution, we performed stress-relaxation measurements to obtain the elastic modulus and identified the state of water in the meat by using proton magnetic resonance imaging (1H MRI) for quantification of a transverse relaxation time (T2). Even after the complete denaturation of myosin, the elastic modulus did not exceed 14kPa, which is not large compared with 6kPa for unheated meat. However, when actin denaturation was initiated, the elastic modulus dramatically increased while the T2 value at the meat surface remarkably decreased. The difference in the state of water between the surface and the core reflected the uneven denaturation distribution in the meat caused by heating. When actin denaturation was complete, the elastic modulus reached 60kPa, which was the equilibrium value, and T2 decreased and its distribution became more flat.

Influence of the Finite Element Model on the Inverse Determination of the Heat Transfer Coefficient Distribution over the Hot Plate Cooled by the Laminar Water Jets / Wpływ Modelu Metody Elementów Skonczonych Na Współczynnika Wymiany Ciepła Wyznaczany Z Rozwiazania Odwrotnego Procesu Laminarnego Chłodzenia Płyty Metalowej

The industrial hot rolling mills are equipped with systems for controlled cooling of hot steel products. In the case of strip rolling mills the main cooling system is situated at run-out table to ensure the required strip temperature before coiling. One of the most important system is laminar jets cooling. In this system water is falling down on the upper strip surface. The proper cooling rate affects the final mechanical properties of steel which strongly dependent on microstructure evolution processes. Numerical simulations can be used to determine the water flux which should be applied in order to control strip temperature. The heat transfer boundary condition in case of laminar jets cooling is defined by the heat transfer coefficient, cooling water temperature and strip surface temperature. Due to the complex nature of the cooling process the existing heat transfer models are not accurate enough. The heat transfer coefficient cannot be measured directly and the boundary inverse heat conduction problem should be formulated in order to determine the heat transfer coefficient as a function of cooling parameters and strip surface temperature. In inverse algorithm various heat conduction models and boundary condition models can be implemented. In the present study two three dimensional finite element models based on linear and non-linear shape functions have been tested in the inverse algorithm. Further, two heat transfer boundary condition models have been employed in order to determine the heat transfer coefficient distribution at the hot plate cooled by laminar jets. In the first model heat transfer coefficient distribution over the cooled surface has been approximated by the witch of Agnesi type function with the expansion in time of the approximation parameters. In the second model heat transfer coefficient distribution over the cooled plate surface has been approximated by the surface elements serendipity family with parabolic shape functions. The heat transfer coefficient values at surface element nodes have been expanded in time by the cubic-spline functions. The numerical tests have shown that in the case of heat conduction model based on linear shape functions inverse solution differs significantly from the searched boundary condition. The dedicated finite element heat conduction model based on non-linear shape functions has been developed to ensure inverse determination of heat transfer coefficient distribution over the cooled surface in the time of cooling. The heat transfer coefficient model based on surface elements serendipity family is not limited to a particular form of the heat flux distribution. The solution has been achieved for measured temperatures of the steel plate cooled by 9 laminar jets.

Multi-objective optimization for free-phase LNAPL recovery using evolutionary computation algorithms

A nonlinear, multi-objective optimization methodology is presented that seeks to maximize free product recovery of light non-aqueous phase liquids (LNAPLs) while minimizing operation cost, by introducing the novel concept of optimal alternating pumping and resting periods. This process allows more oil to flow towards the extraction wells, ensuring maximum free product removal at the end of the remediation period with minimum groundwater extraction. The methodology presented here combines FEHM (Finite Element Heat and Mass transfer code), a multiphase groundwater model that simulates LNAPL transport, with three evolutionary algorithms: the genetic algorithm (GA), the differential evolution (DE) algorithm and the particle swarm optimization (PSO) algorithm. The proposed optimal free-phase recovery strategy was tested using data from a field site, located near Athens, Greece. The PSO and DE solutions were very similar, while that provided by the GA was inferior, although the computation time was roughly the same for all algorithms. One of the most efficient algorithms (PSO) was chosen to approximate the optimal Pareto front, a method that provides multiple options to decision makers. When the optimal strategy is implemented, although a significant amount of LNAPL free product is captured, a spreading of the LNAPL plume occurs. Editor Z.W. Kundzewicz; Associate editor L. See Citation Dokou, Z. and Karatzas, G.P., 2013. Multi-objective optimization for free-phase LNAPL recovery using evolutionary computation algorithms. Hydrological Sciences Journal, 58 (3), 671–685.

Hydrological effects of dip‐slip fault rupture on a hydrothermal plume

AbstractEarthquakes cause a variety of hydrological effects, including changes in well levels, streamflow, hot‐spring temperatures, and geyser periodicity. These may be produced by changes in pore‐fluid pressure or by changes in permeability. We investigate near‐field effects of normal earthquakes on fault‐controlled hydrothermal plumes, e.g., at the Te Kopia geothermal system on the Paeroa Fault, New Zealand. A numerical model is detailed that addresses the effects of coseismic pore‐pressure and permeability perturbations on geothermal upflow along a dip‐slip fault. Fluid flow is modeled using the heat and mass transfer code Finite Element Heat and Mass transfer. The 2 m wide fault is impermeable and thus behaves as a partition between fluid flow in the adjacent fault blocks, as well as a structure for upflow to localize upon. A realistic distribution for the coseismic change in mean rock stress is obtained from a plane‐strain mechanical model for normal fault rupture in an elastic‐plastic‐viscous crust. These stress changes are imported into the fluid flow model as pore‐fluid pressure changes. In addition, we consider the effects of fault core fracture and damage by introducing an increase in permeability at the fault plane. Results show that short‐term effects are dominated by pore‐pressure changes, which cause increased heat and mass fluxes at the surface for a period of several weeks. Longer‐term, an elevated mass flux remains due to the increase in subsurface permeability. Upflow migrates from the footwall scarp into the hanging wall and away from the fault, because rising fluids are no longer deflected by the fault.

SIMULATION OF TRANSIENT CONJUGATE HEAT TRANSFER VIA A TEMPORAL MULTISCALE APPROACH

This paper describes a numerical investigation of the transient temperature field in a solid with a conjugate heat transfer method. The basic approach is based on the strong partitioned coupling of a finite-volume Navier-Stokes solver and a finite-element heat conduction solver. The numerical model employs a quasidynamic algorithm in which the transient thermal field in the solid is coupled with a sequence of steady states in the fluid. Experimental results from a simple test case are compared to numerical simulations and they are found to correspond to within the experimental uncertainties. This model represents a contribution to the field of real-time transient heat loads in solids.

Numerical simulation for the temperature environment of cryogenic pump

To improve performance and design of the cryogenic pump, analyze and solve the pump fault, and ensure the reliability of design and operating, it is highly necessary to understand the cryogenic pump temperature profile. Regarding horizontal single cryogenic centrifugal pump as the studied object, the flow field and structural heat transfer is calculated and analyzed. Based on reasonable boundary condition, three dimensional steady state of the pump mesh model is calculated by finite-element method with the software of Fluent, the fluid pressure field and the whole structural temperature profile is obtained. The structural temperature profile by finite-element heat transfer calculation indicates that: in the operating range of the cryogenic pump, the pumping cryogenic liquid is unable to vaporize at the room temperature, and the low temperature area is unable to interfere with the gear case in normal operation.

Analytical model of metalworking fluid penetration into the flank contact zone in orthogonal cutting

Metalworking fluids (MWFs) are used widely in machining process to dissipate heat, lubricate moving surfaces, and clear chips. They have also been linked to a number of environmental and worker health problems. To reduce these impacts, minimum quantity lubrication (MQL) sprays of MWF delivered in air or CO2 have been proposed. MQL sprays can achieve performance comparable with conventional water-based or straight oil MWFs while only delivering a small fraction of the fluid. This performance advantage could be explained by the enhanced penetration into the cutting zone that results from delivering MWF in high pressure and precise sprays. To explore this hypothesis, an analytical model of MWF penetration into the flank face of the cutting zone is developed and validated using experimental data. The model is based on a derivation of the Navier–Stokes equation and the Reynolds equation for lubrication and applied to an orthogonal cutting geometry under steady-state conditions. A solution to the model is obtained using a numerical strategy of discretizing the analytical scheme with two-dimensional centered finite difference method. Penetration into the cutting zone is estimated for MQL sprays delivered in air, CO2 and N2 as well as two conventional MWFs, straight oil and semi-synthetic emulsion. The model suggests that conventional MWFs, do not penetrate the cutting zone fully and fail to provide direct cooling to the flank zone where wear is most likely to occur. MQL sprays do penetrate the cutting zone completely. Using convective heat transfer coefficients from a previous study, a finite element heat balance is carried out on the tool to understand how each fluid impacts temperature near the flank tip of the tool. The results of the modeling effort are consistent with experimental measurements of tool temperature during turning of titanium (6AL4V) using a K313 carbide tool. The prediction of temperature near the flank indicates that MQL sprays do suppress temperatures near the flank effectively. These results help explain the low levels of tool wear observed for some MQL sprays, particularly those based on high pressure CO2. This modeling framework provides valuable insight into how lubricant delivery characteristics such as speed, viscosity, and cutting zone geometry can impact lubricant penetration.

Thermoelectric Powered Wireless Sensors for Spent Fuel Monitoring

This paper describes using thermoelectric generators to power wireless sensors to monitor spent nuclear fuel during dry-cask storage. OrigenArp was used to determine the decay heat of the spent fuel at different times during the service life of the dry-cask. The Engineering Equation Solver computer program modeled the temperatures inside the spent fuel storage facility during its service life. The temperature distribution in a thermoelectric generator and heat sink was calculated using the computer program Finite Element Heat Transfer. From these temperature distributions the power produced by the thermoelectric generator was determined as a function of the service life of the dry-cask. In addition, an estimation of the path loss experienced by the wireless signal can be made based on materials and thickness of the structure. Once the path loss is known, the transmission power and thermoelectric generator power requirements can be determined. This analysis estimates that a thermoelectric generator can produce enough power for a sensor to function and transmit data from inside the dry-cask throughout its service life.

Experimental heat transfer to supercritical carbon dioxide flowing upward vertical tube with highly conducting surroundings

This paper presents heat transfer characteristics of supercritical carbon dioxide flow inside vertical circular pipe surrounded by highly conducting material, and develops an adequate tool to test the performance of available heat transfer correlations with. The possible situations are illustrated for the nuclear power plant to which the above-mentioned geometric configuration might be applicable. An experimental loop with vertical circular geometry is designed and constructed to test the upward flow in supercritical state when the axial heat transfer is enhanced by the surrounding metals, resulting in a wall boundary condition between the constant heat flux and temperature. The set of correlations and important findings are critically reviewed from extensive literature survey. Incorporating nondimensional groups resorting to past insights from the available literature, a convective heat transfer correlation is proposed. The optimization procedure is described which utilizes a random walk method along with the in-house finite element heat transfer code to determine the coefficients of the proposed heat transfer correlation. The proposed methodology can be applied to evaluation of heat transfer when the heat transfer coefficient data cannot directly be determined from the experiment.

Analysis of Heat Dissipation and the Energy Conservation in Cast Iron Dryer Head of Paper Machine

Analyzed the result computed of finite element heat transfer, discovered the temperature difference between the two sides of head is very small. Therefore its hot loss is very big. In addition, the temperature of dryer head flank is basically the same. Therefore the dryer head's heat dissipation can be simplified as a question of univariate heat conduction, also simplified to be a big plate heat conduction problem. This article offers simple algorithmic analysis of dryer head temperature field algorithm and the heat dissipation computation, and studied the head temperature computation and the heat dissipation analysis with a heat preservation board added. The importance that increased heat preservation board for energy conservation is pointed out.

역열전달해석기법에 의한 LED 조명용 무동력 냉각사이클링 방열기 성능평가

In this study, the performance of a thermo siphon type radiator made of copper for LED lighting system was evaluated by using an inverse heat transfer method. Heating experiments and finite element heat transfer analysis were conducted for three different cases. The data obtained from experiments were compared with the analysis results. Based on the data obtained from experiments, the inverse heat transfer method was used in order to evaluate the heat transfer coefficient. First, the heat transfer analysis was conducted for non-vacuum state, without the refrigerant. The evaluated heat transfer coefficient on the radiator surface was 40W/<TEX>$m^2^{\circ}C$</TEX>. Second, the heat transfer analysis was conducted for non-vacuum state, with the refrigerant, resulting in the heat transfer coefficient of 95W/<TEX>$m^2^{\circ}C$</TEX>. Third, the heat transfer analysis was conducted for vacuum state, with refrigerant. For the third case, the evaluated heat transfer coefficients were 140W/<TEX>$m^2^{\circ}C$</TEX>. Third, the heat transfer analysis was conducted for vacuum state, with refrigerant. For the third case, the evaluated heat transfer coefficients were 140W/<TEX>$m^2^{\circ}C$</TEX> for the radiator body, 5W/<TEX>$m^2^{\circ}C$</TEX>. Third, the heat transfer analysis was conducted for vacuum state, with refrigerant for the rising position of radiator pipe, 35W/<TEX>$m^2^{\circ}C$</TEX>. Third, the heat transfer analysis was conducted for vacuum state, with refrigerant. For the highest position of radiator pipe, and 120W/<TEX>$m^2^{\circ}C$</TEX> for the downturn position of radiator pipe. As a result of inverse heat transfer analysis, it was confirmed that the thermal performance of the current radiator was best in the case of the vacuum state using the refrigerant.

A Simplified Approach for Predicting Temperature Profile in Steel Members With Locally Damaged Fire Protection

Steel structures in building are to be provided with external insulation to delay temperature rise and associated strength degradation when exposed to fire. However, due to delicateness and fragility of some insulation systems, damage might occur in these insulation systems during their service life, and such damage can lead to rapid rise in steel temperature and result in lower fire resistance of structural members. Currently, there are no simple calculation methods for quantifying the effect of insulation loss on steel temperature. In this paper, a simple approach is proposed for tracing the temperature profile in steel members with partial loss of fire protection. The method is developed based on modifying the existing one-dimensional finite difference solutions of the heat transfer equation. The validity of the proposed method is established by comparing the predictions from the proposed method against temperatures obtained from finite element heat transfer model that is created using ANSYS. The comparisons indicate that the proposed method is capable of predicting temperature in steel members with partially damaged insulation to a good degree of accuracy over a wide range of situations. Further, the simplicity of the proposed method makes it attractive for use in fire resistance assessment in steel structures.

Prediction of the Hardened Layer in Traverse Cylindrical Grinding-Hardening

A finite element heat transfer model incorporating a moving heat source has been developed to predict the temperature field in traverse cylindrical grinding. The model was then applied to analyse the grinding-hardening of quenchable steel 1045. It was found that in the region where the grinding wheel had an entire contact with the workpiece, material would experience a heating-cooling cycle, enabling the generation of a uniform hardened layer. In the transient regions at the two ends of the workpiece where the wheel-workpiece contacts were partial, the material was not hardened but experienced an annealing process. The results were in good agreement with the experimental observations.

Heat Transfer in Grinding-Hardening of a Cylindrical Component

A three-dimensional finite element heat transfer model incorporating a moving heat source was developed to investigate the heat transfer mechanism in grinding-hardening of a cylindrical component. The model was applied to analyze the grinding-hardening of quenchable steel 1045 by two grinding methods, traverse and plunge grinding. It was found that the heat generated can promote the martensitic phase transformation in the ground workpiece. As a result, a hardened layer with a uniform thickness can be produced by traverse grinding. However, the layer thickness generated by plunge grinding varies circumferentially. The results are in good agreement with the experimental observations.

Realisation of grinding-hardening in workpieces of curved surfaces—Part 1: Plunge cylindrical grinding

This paper investigates the feasibility to achieve grinding-hardening in a plunge cylindrical grinding process. To understand the mechanisms, a temperature-dependent finite element heat transfer model incorporating a triangular moving heat source was developed to describe the temperature field, thus to predict the thickness of the grinding-hardened layer. The analysis carried out included the variation effect of depth of cut caused by the change in wheel–workpiece engagement. The model was applied on quenchable steel 1045 and the analysis was verified experimentally. It was shown that the heating cycle in plunge cylindrical grinding is the result of consecutive heating and cooling processes, varying from location to location in a workpiece. The ratio of the workpiece speed to the infeed rate plays an important role in the heat treatment cycle.

Modeling of the Effect of Path Planning on Thermokinetic Evolutions in Laser Powder Deposition Process

A thermokinetic model coupling finite-element heat transfer with transformation kinetics is developed to determine the effect of deposition patterns on the phase-transformation kinetics of laser powder deposition (LPD) process of a hot-work tool steel. The finite-element model is used to define the temperature history of the process used in an empirical-based kinetic model to analyze the tempering effect of the heating and cooling cycles of the deposition process. An area is defined to be covered by AISI H13 on a substrate of AISI 1018 with three different deposition patterns: one section, two section, and three section. The two-section pattern divides the area of the one-section pattern into two sections, and the three-section pattern divides that area into three sections. The results show that dividing the area under deposition into smaller areas can influence the phase transformation kinetics of the process and, consequently, change the final hardness of the deposited material. The two-section pattern shows a higher average hardness than the one-section pattern, and the three-section pattern shows a fully hardened surface without significant tempered zones of low hardness. To verify the results, a microhardness test and scanning electron microscope were used.

Modelling thermal performance of gypsum plasterboard‐lined light timber frame walls using SAFIR and TASEF

AbstractGypsum plasterboard is commonly used as a lining material on lightweight timber or steel framing. Gypsum contains moisture, both free and chemically bound in its crystal structure. The dehydration of the gypsum and decomposition of calcium carbonate absorb heat giving gypsum plasterboard fire resistant qualities. This paper discusses the suitability of the finite element heat transfer program SAFIR for modelling plasterboard‐lined light timber frame assemblies and its limitations. The default material properties in SAFIR for gypsum plasterboard do not give good results and ‘smoothing’ of enthalpy curves has insignificant effects on the results but substantially reduces processing time. Modelling with SAFIR gives similar results to prior modelling using the program TASEF with slight differences. Both programs give better overall results for slower developing fires and furnace tests than more rapidly growing fires. Reasonable, slightly conservative results for thermal analysis of heat transfer through the walls and into timber studs can be achieved using the parameters suggested in this paper. More sophisticated and detailed models incorporating mass transfer, effect of fasteners, gaps between lining sheets and ablation are required to achieve better comparisons. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Heat Transfer and Stress Analysis of Coke Drum for a Complete Operating Cycle

Coke drums experience severe thermal and mechanical loadings during operation, and the reliability and safety of the coke drums are critical to the industry. The objective of this study is to analyze temperature and stress of the coke drum for a complete process cycle. The thermal analysis model of the coke drum is first developed incorporating appropriate boundary conditions. The heat transfer coefficients at the inner surface of the coke drum, which change with the operation stages and the levels of oil filling and water quenching, are determined based on the temperature measurement data at a certain location on the outer surface of the coke drum. The temperature history of the coke drum of a complete cycle is then obtained by finite element heat transfer analysis, and computed temperature data are used for the stress analysis of the coke drum, including both thermal and mechanical loadings. It is found from numerical results that the clad experiences a biaxial stress cycling with maximum value higher than the yield limit of the material, which coincide with the low cycle fatigue failure of the structure.