Local Heat Flow Research Articles

Impact of magnetohydrodynamics (MHD) on energy transmission through ferrofluid saturating porous medium contained in a lid-driven trapezoidal container with triangular notched heater configuration

This article conveys numerical simulations for energy flow by mixed convection under the impact of magnetohydrodynamics (MHD) through ferrofluid saturating porous media contained in a trapezoidal enclosure having triangular notched heater at the bottom wall when the container’s top boundary is in motion with constant speed. The side and top walls of the container are assumed to be cold, the bottom wall is insulated, and the triangular notched heater supplies uniform heat to the fluid. Equations governing the flow are initially exposed to penalty scheme to eradicate pressure from momentum equations, and subsequently, the Galerkin weighted residual method is employed to compute the numerical solutions for velocity and temperature profiles. Computed solutions are expressed in form of graphs for streamline circulations, isotherms, and local and mean heat flow rates for suitable ranges of important physical parameters governing the flow, including the Darcy number (10−5 ≤ Da ≤ 10−3), Reynolds number (1 ≤ Re ≤ 10), Hartmann number (30 ≤ Ha ≤ 100), Prandtl number (0.062 ≤ Pr ≤ 10), concentration of solid ferroparticles (0.03 ≤ [Formula: see text] ≤ 0.15), and Grashof number (105 ≤ Gr ≤107). This investigation deduces that flow strength rises with escalation in the concentration of ferroparticles, as well as Darcy and Grashof numbers. The convection energy flow regime appears dominating for small Hartmann number and large Prandtl number. The mean energy flow rate is found to increase with increase in Darcy and Grashof numbers and it attenuates with escalation in the Hartmann number.

A Simple Effective Method for Three-Dimensional Modelling of Cementation, Fracturing and Dissolution of Carbonate Rocks: Illustrated through Oolitic Limestone

Sandstones and many carbonates (e.g., oolitic limestone and other grainstones), comprise solid particulates (grains) and pores, which have a given pore network architecture relationship, and associated porosity—permeability values. Over time, through the process of diagenesis, the pore network architecture may be extensively altered. Changes can include compaction, particle deformation, cementation, dissolution and fracturing, with the pathway followed after deposition depending on factors such as the energy level, rate of burial, degree of biological activity, local heat flow, sediment composition, Eh, pH and the presence or absence of organic materials. Any method that provides a means of modelling changes is therefore highly desirable, in particular, allowing a prediction of changes in porosity and permeability with time. The current work illustrates a simple method that uses freely available open source image analysis software to model the development of cement phases within an oolitic limestone in three-dimensions. As well as cementation, it demonstrates the modelling of fracture development and dissolution processes, and records how porosity and permeability change during such processes.

Curie point depth, thermal gradient, and heat flow in the Colombian Caribbean (northwestern South America)

Geothermal gradients were estimated at the points of a grid with cell size of 50 km by 50 km in northwestern Colombia. Depths to the bottom of magnetic sources were assumed to represent Curie depths, and were estimated by means of statistical-spectral analysis of aeromagnetic data contained in square windows of 100 km by 100 km, 200 km by 200 km, and 300 km by 300 km. The centroid method and a variation of it that considers the fractal distribution of magnetization were applied. The modified centroid method provided better estimations of Curie depths, which range between 13 km and 47 km. Obtained Curie depths are comparable to those reported in other studies of regional character. The corresponding estimated geothermal gradients correlate quite well with estimations based on the bottom simulating reflector and bottom hole temperatures. Observed differences are small and can be accounted for by local heat flow variations due to shallow ground water flow, or recent sedimentation. Elaborated geothermal gradient and heat flow maps for northwestern Colombia are accurate and consistent with estimates of the thickness of the oceanic crust and continental cortical thicknesses, reported by previous authors. The maps presented in this study represent a contribution to the heat flow studies in northwestern South America.

Unusual marbles in a non-metamorphic succession of the SW Alps (Valdieri, Italy) due to early Oligocene hydrothermal flow

In the SW Alps, at the NE margin of the Argentera Massif, the occurrence of isolated bodies of silicate-bearing marbles (Valdieri Marble), laterally passing to non-metamorphic Mesozoic limestones of the Dauphinois succession, appears enigmatic, since their origin cannot be related to the regional metamorphism. The stratigraphic, geometric, petrographic, and geochemical features of the Valdieri Marble indicate that it originated from the upflow of hydrothermal fluids which deeply recrystallised the limestone and provoked the abundant neoblastesis of silicate minerals, at an estimated crystallisation temperature of ca. 350 °C. This paper provides for the first time an absolute U/Pb age, comprised between 30 and 31.6 Ma (early Oligocene), for the Valdieri Marble, which is affected by a syn-genetic shear foliation in turn crosscut by the main Alpine tectonic foliations. The hydrothermal fluids that formed the Valdieri Marble migrated along low-angle shear zones, mostly parallel to the sedimentary primary bedding, which were downward connected with high-angle master faults of the “Alpine SW transfer”, a main Oligocene–early Miocene transcurrent shear zone at the southern termination of the Western Alps. The localized heat flow sustaining the hydrothermal system could be related to the early Oligocene thermal event, well documented by magmatic activity in the Western and Central Alps.

Solution of Thermoelectricity Problems Energy Method

On the basis of the fundamental laws of conservation of energy in conjunction with local quadratic spline functions was developed a universal computing algorithm, a method and associated software, which allows to investigate the Thermophysical insulated rod, with limited length, influenced by local heat flow, heat transfer and temperature

Enceladus’ near-surface CO2 gas pockets and surface frost deposits

Solid CO2 surface deposits were reported in Enceladus’ South Polar Region by Brown et al. (2006). They noted that such volatile deposits are temporary and posited ongoing replenishment. We present a model for this replenishment by expanding on the Matson et al. (2012) model of subsurface heat and chemical transport in Enceladus. Our model explains the distributions of both CO2 frost and complexed CO2 clathrate hydrate as seen in the Cassini Visual and Infrared Mapping Spectrometer (VIMS) data. We trace the journey of CO2 from a subsurface ocean. The ocean-water circulation model of Matson et al. (2012) brings water up to near the surface where gas exsolves to form bubbles. Some of the CO2 bubbles are trapped and form pockets of gas in recesses at the bottom of the uppermost ice layer. When fissures break open these pockets, the CO2 gas is vented. Gas pocket venting is episodic compared to the more or less continuous eruptive plumes, emanating from the “tiger stripes”, that are supported by plume chambers. Two styles of gas pocket venting are considered: (1) seeps, and (2) blowouts.The presence of CO2 frost patches suggests that the pocket gas slowly seeped through fractured, cold ice and when some of the gas reached the surface it was cold enough to condense (i.e., T ∼70 to ∼119 K). If the fissure opening is large, a blowout occurs. The rapid escape of gas and drop in pocket pressure causes water in the pocket to boil and create many small aerosol droplets of seawater. These may be carried along by the erupting gas. Electrically charged droplets can couple to the magnetosphere, and be dragged away from Enceladus. Most of the CO2 blowout gas escapes from Enceladus and the remainder is distributed globally. However, CO2 trapped in a clathrate structure does not escape. It is much heavier and slower moving than the CO2 gas. Its motion is ballistic and has an average range of about 17 km. Thus, it contributes to deposits in the vicinity of the vent. Local heat flow indicates that gas pockets can be located as deep as several tens of meters below the surface. Gas pockets can be reused, and we explore their life cycle.

Investigations of burning phenomena during the hard anodising of aluminium by local in-operando temperature measurements

The heat evolution during hard anodising in sulfuric acid with and without provoked burning is investigated using an in-house designed setup for local in-operando temperature measurements. Local heat flows are computed from the measurements and compared to the average Joule heating and the heat flow into the electrolyte. The development of temperature gradients during the anodization process and burning is discussed in view of the formation of thermo-mechanical stress and its influence on the properties and microstructure of the resulting oxide layer. Comprehensive SEM-mapping of the sample surface subjected to burning is performed and the results are analysed regarding the local temperatures as well as thermo-mechanical stress effects during anodising.

A new method to simultaneously measure local heat transfer and visualize flow boiling in plate heat exchanger

This paper presents the development of a novel method to combine measurement of local heat transfer coefficient and flow visualization in frame-and-plate heat exchanger (FPHE) simultaneously. A heat flux plate is built using two original chevron plates and clay as thermal infills. Thermocouples are deployed on the inner surfaces of both plates. With the known thickness and thermal conductivity of the clay, the instrumented plate functions as a heat flux sensor. After initial calibration, this plate is installed to measure fluid heat transfer from one side, while leaving visual access from the other. Preliminary results of water-water single-phase heat transfer and R245fa-water flow boiling are presented. Combined with visualization, the method provides a viable solution to relate local heat transfer with flow regime within a plate channel, while preserving the real geometry and operating condition.

Investigation of flow structure and heat exchange formation in corrugated pipes at transient reynolds numbers

The problem of convective heat transfer in the initial section of a pipe with a corrugated section was considered at transient Reynolds numbers. Influence on the intensity of heat exchange and the magnitude of hydraulic resistance of geometric parameters (wavelength and amplitude) of the corrugated insert, variability of the thermophysical properties of the heat carrier and the direction of the heat flow was estimated. Threshold value of the corrugation wavelength (L/R 0 >0.6) was determined for the Reynolds number range under consideration for which there was a significant growth of heat exchange. Influence of the gradient of the dynamic viscosity coefficient on flow stability and intensification of heat exchange in internal flows was demonstrated. Influence of Reynolds and Prandtl numbers on local heat transfer, hydraulic resistance and flow structure was determined. It was established that the use of corrugated surfaces is ineffective at Reynolds numbers less than 2000. It was shown that heat exchange in a pipe can be raised to 30 % with an increase in hydraulic resistance of 1.05 times in the range of Reynolds numbers 2·10 3 ...1.4·10 4 with the use of a nonencumbering corrugation.

Thermal rectification in mass-graded next-nearest-neighbor Fermi-Pasta-Ulam lattices.

We study the thermal rectification efficiency, i.e., quantification of asymmetric heat flow, of a one-dimensional mass-graded anharmonic oscillator Fermi-Pasta-Ulam lattice both with nearest-neighbor (NN) and next-nearest-neighbor (NNN) interactions. The system presents a maximum rectification efficiency for a very precise value of the parameter that controls the coupling strength of the NNN interactions, which also optimizes the rectification figure when its dependence on mass asymmetry and temperature differences is considered. The origin of the enhanced rectification is the asymmetric local heat flow response as the heat reservoirs are swapped when a finely tuned NNN contribution is taken into account. A simple theoretical analysis gives an estimate of the optimal NNN coupling in excellent agreement with our simulation results.

Heat flow: The neglected potential field for mineral exploration

This paper argues that heat flow is a valid ‘potential field method’ for mineral exploration. Certain ore deposits, most notably iron oxide copper gold uranium (IOCG-U) deposits, demonstrably affect the local heat flow and ground temperature conditions. The physics of steady state conductive heat flow is mathematically the same as gravitational acceleration, with buried heat sources analogous to buried masses. Detecting the surface signature of a buried heat source can therefore yield direct evidence of an ore body. The physics is robust, appropriate tools exist for the collection of heat flow data for exploration, and some simple strategies could yield valuable additional information about the subsurface for small marginal cost.

Air-sea heat fluxes associated to mesoscale eddies in the Southwestern Atlantic Ocean and their dependence on different regional conditions

Heat fluxes between the ocean and the atmosphere largely represent the link between the two media. A possible mechanism of interaction is generated by mesoscale ocean eddies. In this work we evaluate if eddies in Southwestern Atlantic (SWA) Ocean may significantly affect flows between the ocean and the atmosphere. Atmospherics conditions associated with eddies were examined using data of sea surface temperature (SST), sensible (SHF) and latent heat flux (LHF) from NCEP–CFSR reanalysis. On average, we found that NCEP–CFSR reanalysis adequately reflects the variability expected from eddies in the SWA, considering the classical eddy-pumping theory: anticyclonic (cyclonic) eddies cause maximum positive (negative) anomalies with maximum mean anomalies of 0.5 °C (−0.5 °C) in SST, 6 W/m2 (−4 W/m2) in SHF and 12 W/m2 (−9 W/m2) in LHF. However, a regional dependence of heat fluxes associated to mesoscale cyclonic eddies was found: in the turbulent Brazil–Malvinas Confluence (BMC) region they are related with positive heat flux anomaly (ocean heat loss), while in the rest of the SWA they behave as expected (ocean heat gain). We argue that eddy-pumping do not cool enough the center of the cyclonic eddies in the BMC region simply because most of them trapped very warm waters when they originate in the subtropics. The article therefore concludes that in the SWA: (1) a robust link exists between the SST anomalies generated by eddies and the local anomalous heat flow between the ocean and the atmosphere; (2) in the BMC region cyclonic eddies are related with positive heat anomalies, contrary to what is expected.

On the possibility of control restoration in some inverse problems of heat and mass transfer

The hypersonic aircraft permeable surfaces effective heat protection problems are considered. The physic-chemical processes (the dissociation and the ionization) in laminar boundary layer of compressible gas are appreciated in mathematical model. The statements of direct problems of heat and mass transfer are given: according to preset given controls it is necessary to compute the boundary layer mathematical model parameters and determinate the local and total heat flows and friction forces and the power of blowing system. The A.A.Dorodnicyn's generalized integral relations method has been used as calculation basis. The optimal control - the blowing into boundary layer (for continuous functions) was constructed as the solution of direct problem in extreme statement with the use of this approach. The statement of inverse problems are given: the control laws ensuring the preset given local heat flow and local tangent friction are restored. The differences between the interpolation and the approximation statements are discussed. The possibility of unique control restoration is established and proved (in the stagnation point). The computational experiments results are presented.

On computational experiments in some inverse problems of heat and mass transfer

The results of mathematical modeling of effective heat and mass transfer on hypersonic aircraft permeable surfaces are considered. The physic-chemical processes (the dissociation and the ionization) in laminar boundary layer of compressible gas are appreciated. Some algorithms of control restoration are suggested for the interpolation and approximation statements of heat and mass transfer inverse problems. The differences between the methods applied for the problem solutions search for these statements are discussed. Both the algorithms are realized as programs. Many computational experiments were accomplished with the use of these programs. The parameters of boundary layer obtained by means of the A.A.Dorodnicyn's generalized integral relations method from solving the direct problems have been used to obtain the inverse problems solutions. Two types of blowing laws restoration for the inverse problem in interpolation statement are presented as the examples. The influence of the temperature factor on the blowing restoration is investigated. The different character of sensitivity of controllable parameters (the local heat flow and local tangent friction) respectively to step (discrete) changing of control (the blowing) and the switching point position is studied.

창호 전체 단열성능과 열교부위 열성능 상관관계 분석

Thermal bridge in windows can cause multiple problems, including heat loss and mold/condensation problems. The energy performance of window has been dramatically improved in recent years, however, mold/condensation are still challenging problems. This paper analyzed the relationship of thermal performance between the whole window and thermal bridging area. Also, it identified the factors which affect the local heat flow of window thermal bridging. The results show that the thermal performance of window thermal bridging area has no direct relationship with window U-value. The window type and the position of Low-e coating were identified as key factors affecting the thermal performance of window thermal bridging area.

Coupling of Human Thermoregulation and URANS Computation for Investigation of Local Heat Transfer and Flow Structures in a Generic Car Cabin

Commonly used flow regimes, e.g. defrost and panel mode, are compared regarding human skin temperature and local comfort in dependence of the inlet direction, temperature levels and position of the driver. To avoid the standard application of a constant heat flux of about 50W/m2 for consideration of realistic thermal boundary conditions of the human, the heat emission of the driver is introduced using active and passive thermoregulation with application of the well-known Fiala model. The heat transfer through the seat is calculated using CHT method by coupling three regions, human - seat - environment. Computations using large computational resources allow for exploration of different climate control strategies as they relate to local flow structures and skin temperatures on the human body in a detailed manner.

Interannual perturbations of the Martian surface heat flow by atmospheric dust opacity variations

AbstractThe InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission will perform the first Martian in situ heat flow measurement by deploying the Heat Flow and Physical Properties Package (HP3) onto the Martian surface. In order to estimate the heat flow coming from the planetary interior, HP3 will measure the local subsurface thermal gradient as well as the local thermal conductivity to a depth of up to 5 m. From these measurements, local heat flow can be determined, but this will in general differ from the heat flow emanating from the planetary interior due to atmosphere‐induced perturbations. Here we quantify heat flow perturbation induced by dust loading of the Martian atmosphere using dust opacity data obtained by the Mars Exploration Rover Opportunity. Dust opacity data span the time period between Mars year (MY) 27 and MY 32, thus incorporating the global dust storm event of MY 28 as a signal. We consider two end‐member cases for the regolith thermal conductivity and find that the background planetary heat flow is superposed by atmosphere‐induced perturbations of less than 1.5 mW m−2 at depths below 2 m if regolith thermal conductivity is low and around 0.025 W m−1 K−1 on average. If thermal conductivity is high and around 0.05 W m−1 K−1 on average, perturbations are less than 2.5 mW m−2 at depths below 3 m. Overall, the influence of interannual variability on subsurface heat flow is found to be moderate following a global dust storm. Considerably smaller perturbations are introduced by regional dust storms, which are of shorter duration and smaller magnitude.

An experimental investigation on flow boiling heat transfer of R-600a in a horizontal small tube

The local heat transfer coefficient and flow pattern were studied experimentally during flow boiling of R-600a inside a horizontal small tube (inner diameter ID = 1.0 mm). The effects of heat flux, mass velocity and vapor quality have been investigated. The tests were conducted at heat fluxes from 5 to 60 kW m−2, mass velocity from 240 to 480 kg m−2 s−1 at 25 °C saturation temperature. Results show that flow patterns are related to the heat transfer coefficient. Convective boiling was found to be predominant during the tests. Nucleate boiling was predominant only in low vapor quality region. The resultant database was compared against predicting correlation available in literature for heat transfer coefficient. It was found that mass velocity have significant influence of heat transfer coefficients.

Numerical Simulation of Temperature Distribution Field in Beam Bulk in the Simultaneous Presence of Heat Insulation, Heat Flux and Heat Exchange

Most of the bearing elements of electric power installations operate in the presence of local cold insulator, heat flow, and heat transfer. To ensure the smooth operation of these elements it is necessary to develop appropriate computational algorithms and methods that allow to investigate numerically the thermomechanical condition of bearing elements. Besides, obtained numerical results should have different precision and respectively describe such a complex exceptional nonlinear process under study. Under the established process for the length of the test rod bearing element temperature field, displacement field, elastic, thermal and thermoelastic stress components field will arise. To determine these decisions, taking into account natural conditions and maintenance, we should use the techniques oriented on the basic laws of conservation of energy [1, 2].

Wellbore and groundwater temperature distribution eastern Snake River Plain, Idaho: Implications for groundwater flow and geothermal potential

A map of groundwater temperatures from the Eastern Snake River Plain (ESRP) regional aquifer can be used to identify and interpret important features of the aquifer, including aquifer flow direction, aquifer thickness, and potential geothermal anomalies. The ESRP is an area of high heat flow, yet most of this thermal energy fails to reach the surface, due to the heat being swept downgradient by the aquifer to the major spring complexes near Thousand Springs, ID, a distance of 300km. Nine deep boreholes that fully penetrate the regional aquifer display three common features: (1) high thermal gradients beneath the aquifer, corresponding to high conductive heat flow in low-permeability hydrothermally-altered rocks; (2) isothermal temperature profiles within the aquifer, characteristic of an actively flowing groundwater; and (3) moderate thermal gradients in the vadose zone with values that indicate that over half of the geothermal heat flow is removed by advective transport in the regional aquifer system. This study utilized temperature data from 250 ESRP aquifer wells to evaluate regional aquifer flow direction, aquifer thickness, and potential geothermal anomalies. Because the thermal gradients are typically low in the aquifer, any measurement of groundwater temperature is a reasonable estimate of temperature throughout the aquifer thickness, allowing the construction of a regional aquifer temperature map for the ESRP. Mapped temperatures are used to identify cold thermal plumes associated with recharge from tributary valleys and adjacent uplands, and warm zones associated with geothermal input to the aquifer. Warm zones in the aquifer can have various causes, including local circulation of groundwater through the deep conductively dominated region, slow groundwater movement in low-permeability regions, or localized heat flow from deeper thermal features.