scholarly journals Advective Heat Transport and the Salt Chimney Effect: A Numerical Analysis

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-18
Author(s):  
David P. Canova ◽  
Mark P. Fischer ◽  
Richard S. Jayne ◽  
Ryan M. Pollyea
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Transport ◽  
Conductive Heat ◽  
High Porosity ◽  
Model Sets ◽  
Advective Heat Transfer ◽  
Geologic Heterogeneity ◽  
Advective Heat Transport ◽  
Chimney Effect

We conducted numerical simulations of coupled fluid and heat transport in an offshore, buried salt diapir environment to determine the effects of advective heat transport and its relation to the so-called “salt chimney effect.” Model sets were designed to investigate (1) salt geometry, (2) depth-dependent permeability, (3) geologic heterogeneity, and (4) the relative influence of each of these factors. Results show that decreasing the dip of the diapir induces advective heat transfer up the side of the diapir, elevating temperatures in the basin. Depth-dependent permeability causes upwelling of warm waters in the basin, which we show to be more sensitive to basal heat flux than brine concentration. In these model scenarios, heat is advected up the side of the diapir in a narrower zone of upward-flowing warm water, while cool waters away from the diapir flank circulate deeper into the basin. The resulting fluid circulation pattern causes increased discharge at the diapir margin and fluid flow downward, above the crest of the diapir. Geologic heterogeneity decreases the overall effects of advective heat transfer. The presence of low permeability sealing horizons reduces the vertical extent of convection cells, and fluid flow is dominantly up the diapir flank. The combined effects of depth-dependent permeability coupled with geologic heterogeneity simulate several geologic phenomena that are reported in the literature. In this model scenario, conductive heat transfer dominates in the basal units, whereas advection of heat begins to affect the middle layers of the model and dominates the upper units. Convection cells split by sealing layers develop within the upper units. From our highly simplified models, we can predict that advective heat transport (i.e., thermal convection) likely dominates in the early phases of diapirism when sediments have not undergone significant compaction and retain high porosity and permeability. As the salt structures mature into more complex geometries, advection will diminish due to the increase in dip of the salt-sediment interface and the increased hydraulic heterogeneity due to complex stratigraphic architecture.

scholarly journals Sensitivity of Thermal Predictions to Uncertain Surface Tension Data in Laser Additive Manufacturing

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
J. Coleman ◽  
A. Plotkowski ◽  
B. Stump ◽  
N. Raghavan ◽  
A. S. Sabau ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Fluid Flow ◽  
Additive Manufacturing ◽  
Current Model ◽  
Surface Tension Gradient ◽  
Process Conditions ◽  
Conductive Heat ◽  
Melt Pool ◽  
Super Alloy

Abstract To understand the process-microstructure relationships in additive manufacturing (AM), it is necessary to predict the solidification characteristics in the melt pool. This study investigates the influence of Marangoni driven fluid flow on the predicted melt pool geometry and solidification conditions using a continuum finite volume model. A calibrated laser absorptivity was determined by comparing the model predictions (neglecting fluid flow) against melt pool dimensions obtained from single laser melt experiments on a nickel super alloy 625 (IN625) plate. Using this calibrated efficiency, predicted melt pool geometries agree well with experiments across a range of process conditions. When fluid mechanics is considered, a surface tension gradient recommended for IN625 tends to overpredict the influence of convective heat transfer, but the use of an intermediate value reported from experimental measurements of a similar nickel super alloy produces excellent experimental agreement. Despite its significant effect on the melt pool geometry predictions, fluid flow was found to have a small effect on the predicted solidification conditions compared to processing conditions. This result suggests that under certain circumstances, a model only considering conductive heat transfer is sufficient for approximating process-microstructure relationships in laser AM. Extending the model to multiple laser passes further showed that fluid flow also has a small effect on the solidification conditions compared to the transient variations in the process. Limitations of the current model and areas of improvement, including uncertainties associated with the phenomenological model inputs are discussed.

scholarly journals ADVECTIVE HEAT TRANSPORT AND THE SALT CHIMNEY EFFECT: A NUMERICAL ANALYSIS

2016 ◽  
Author(s):  
David P. Canova ◽  
◽  
Mark P. Fischer ◽  
Ryan Pollyea ◽  
Rick Jayne
Keyword(s):  
Numerical Analysis ◽  
Heat Transport ◽  
Advective Heat Transport ◽  
Chimney Effect

Numerical Consideration of LTNE and Darcy Extended Forchheimer Models for the Analysis of Forced Convection in a Horizontal Pipe in the Presence of Metal Foam

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Prakash H. Jadhav ◽  
N. Gnanasekaran ◽  
D. Arumuga Perumal
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Forced Convection ◽  
Heat Exchangers ◽  
Heat Dissipation ◽  
Metal Foam ◽  
Metallic Foam ◽  
High Porosity ◽  
Transition Flow ◽  
Horizontal Pipe

Abstract The intent of the current research work is to emphasize the computational modeling of forced convection heat dissipation in the presence of high porosity and thermal conductivity metallic foam in a horizontal pipe for different regimes of the fluid flow for a range of Reynolds number. A two-dimensional physical domain is considered in which Darcy extended Forchheimer (DEF) model is adopted in the aluminum metallic foam to predict the features of fluid flow and local thermal nonequilibrium (LTNE) model is employed for the analysis of heat transfer in a horizontal pipe for different flow regimes. The numerical results are initially matched with experimental and analytical results for the purpose of validation. The average Nusselt number for fully filled foam is found to be higher compared to other filling rate of metallic foams and the clear pipe at the cost of pressure drop. As an important finding, it has been observed that the laminar and transition flow gives higher heat transfer enhancement ratio and thermal performance factor compared to turbulent flow. This work resembles numerous industrial applications such as solar collectors, heat exchangers, electronic cooling, and microporous heat exchangers. The novelty of the work is the selection of suitable flow and thermal models in order to clearly assimilate the flow and heat transfer in metallic foam. The presence of aluminum metal foam is highlighted for the augmentation of heat dissipation in terms of PPI and porosity. The parametric study proposed in this work surrogates the complexity and cost involved in developing an expensive experimental setup.

Coupled fluid flow, heat and mass transport, and erosion in the Alberta basin: implications for the origin of the Athabasca oil sands

2004 ◽  
Vol 41 (9) ◽  
pp. 1077-1095 ◽  
Author(s):  
J J Adams ◽  
B J Rostron ◽  
C A Mendoza
Keyword(s):  
Fluid Flow ◽  
Heat Transport ◽  
Oil Sands ◽  
Conductive Heat ◽  
Formation Water ◽  
Athabasca Oil Sands ◽  
Peace River ◽  
Regional Topography ◽  
Alberta Basin ◽  
Flow Heat

Regional topography-driven flow systems related to Laramide tectonic rebound were simulated using two-dimensional, coupled fluid-flow, heat transport, and solute transport numerical models to replicate present formation water salinity and temperature distributions and investigate the accumulation of the Athabasca oil sands. Previous modelling of this system was replicated, and it predicted repeated replacement of all basin formation water with freshwater during deposition of the oil sands due to high permeabilities. To match present Alberta basin temperature and salinity distributions, model hydrostratigraphy, permeabilities, and heat fluxes were adjusted. This revised model conducts fluids along the Mannville aquifer, rather than the Upper Devonian aquifer, and replicates present salinity distributions, assuming instantaneous uplift around 60 Ma. Fluid fluxes in principal aquifers decrease by two-orders of magnitude using new permeabilities, resulting in primarily conductive heat transport. Thus, genesis of the Athabasca oil sands cannot be explained by dissolved-phase petroleum transport due to low simulated fluxes. Model simulations representing constant erosion of a higher topographic gradient produce similar flow patterns, but fluid fluxes, temperatures and hydraulic heads uniformly decrease over 58 million years. Increased erosion rates in the last stage of simulations produce sub-hydrostatic pressures near the uplift, which trigger a flow reversal in the basin. Thinning of the capping Cretaceous aquitard and Mannville permeability distribution causes discharge in the vicinity of the Peace River, coincident with Peace River oil sands and solonetzic soil zones. Regional topography-driven flow gradually decays via diminishing fluid fluxes, underpressuring near the disturbed belt, and development of local flow sub-systems driven by small-scale relief.

scholarly journals Transport of heat through the skin

2017 ◽  
Vol 15 (1) ◽  
pp. 68-71
Author(s):  
Yury I Luchakov ◽  
Petr D Shabanov
Keyword(s):  
Heat Transfer ◽  
Mathematical Model ◽  
Heat Transport ◽  
Convective Heat ◽  
Human Body ◽  
Blood Stream ◽  
Conductive Heat ◽  
Skin Region ◽  
Superficial Skin ◽  
Different Tissues

The transport of heat through the skin of the human body has been investigated in the paper. The analysis of cytoarchiterture of this region was done, a model of vascular stream of the skin was built where the transient microregion typical for its different tissues was separated. A mathematical model taking part both convective and conductive heat transport was reproduced for this microregion. There was no heat transfer through the blood but only conductive heat transport was shown to be in the superficial skin tissue strates having blood current. In the norm, there was convective heat transport preferably in the deeper skin strates of the hypoderm where arterials and veins of more than 100 and 300 um in diameter were lying. The organism was revealed to able to increase or decrease the skin region where there was only convective or conductive heat transport by means of changing the blood stream. Therefore, the organism is able to change the size of peripheral tissue where there is only convective or only conductive heat transfer according to physiological necessity.

Heat Transfer and Fluid Flow Characteristics of One Side Heated Vertical Rectangular Channel Applied As Vessel Cooling System of VHTR

2018 ◽  
Author(s):  
Kenta Fujikami ◽  
Tetsuaki Takeda ◽  
Shumpei Funatani
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
High Temperature ◽  
Natural Convection ◽  
Porous Material ◽  
Cooling System ◽  
Flow Characteristics ◽  
High Porosity ◽  
High Temperature Reactor ◽  
Fluid Flow Characteristics

A Very High Temperature Reactor (VHTR) is one of the next generation nuclear reactor systems. From a view point of safety characteristics, a passive cooling system should be designed as the best way of a reactor vessel cooling system (VCS) in the VHTR. Therefore, the gas cooling system with natural circulation is considered as a candidate for the VCS of the VHTR. Japan Atomic Energy Agency (JAEA) is advancing the technology development of the VHTR and is now pursuing design and development of commercial systems such as the 300MWe gas turbine high temperature reactor GTHTR300C (Gas Turbine High Temperature Reactor 300 for Cogeneration). In the VCS of the GTHTR300C, many rectangular flow channels are formed around the reactor pressure vessel (RPV), and a cooling panel utilizing natural convection of air has been proposed. In order to apply the proposed panel to the VCS of the GTHTR300C, it is necessary to clarify the heat transfer and flow characteristics of the proposed channel in the cooling panel. Thus, we carried out an experiment to investigate heat transfer and fluid flow characteristics by natural convection in a vertical rectangular channel heated on one side. Experiments were also carried out to investigate the heat transfer and fluid flow characteristics by natural convection when a porous material with high porosity is inserted into the channel. An experimental apparatus is a vertical rectangular flow channel with a square cross section in which one surface is heated by a rubber heater. Dimensions of the experimental apparatus is 600 mm in height and 50 mm on one side of the square cross section. Air was used as a working fluid and fine copper wire (diameter: 0.5 mm) was used as a porous material. The temperature of the wall surface and gas in the channel were measured by K type thermocouples. The flow velocity distribution was obtained by a PIV method. In this paper, we discuss the heat transfer and fluid flow characteristics of the proposed channel. From the results obtained in the experiment, it was found that the amount of removed heat decreased with increasing of temperature of gas when a copper wire was inserted into the channel with high porosity. This is because the mass flow rate decreased with increasing of viscosity of gas. Since it is expected that the porosity of a porous material will have an optimum value, further studies will be needed.

Conjugate Heat Transfer in an Enclosure With Internal Contaminant and Heat Source Using Lattice Boltzmann Method

2010 ◽  
Author(s):  
Salah Hosseini ◽  
Vahid Abdollahi ◽  
Amir Nejat
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Fluid Flow ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Solid Phase ◽  
Internal Heat ◽  
Fluid Phase ◽  
Conductive Heat ◽  
Boltzmann Method

Conjugate convective-conductive heat transfer in an enclosure is simulated. Internal heat and contaminant sources are included in the fluid flow domain, causing mass transfer within the cavity. The two-dimensional governing equations for natural heat and mass convection in the fluid phase and heat conduction in the solid phase are solved employing lattice Boltzmann method. The effects of Rayleigh number and buoyancy ratio variations on the fluid flow, heat and mass transfer characteristics are studied.

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