Multi-Source Thermal Model for Electrical Harness Design

2019 ◽  
Author(s):  
Julien Petitgirard ◽  
Philippe Baucour ◽  
Didier Chamagne ◽  
Eric Fouillien
Keyword(s):  
Heat Fluxes ◽  
Reduced Model ◽  
Geothermal Heat ◽  
Analytic Equation ◽  
Physical Point ◽  
Joule Effect ◽  
Variable Environment ◽  
Node Network ◽  
Thermal Sources ◽  
Nodal Methods

Abstract The challenges of improving wiring harness design are safety, ecology, weight and cost. To achieve this, a better prediction of the temperature in the wiring harnesses is necessary. In terms, this involves considering a lot of compact thermal sources with an uncontrolled layout. Up to now, the main methods dedicated to resolution are based on finite elements given that temperature’s evolution according to several thermal sources, Joule effect, without controlled wire layout is complicated to evaluate. This paper deals with an alternative and faster method. An analytic equation : Infinite Line Source (ILS), is used to create a nodal network. This method coming from geothermal heat exchangers relies on a fully-connected node network which is called here full-graph method. It will be shown that, for compact heat sources, this method can be improved with a reduced model. A reduced model is a pruned node network: only the wires corresponding to the adjoining wires are selected. The bundle is a complex system which has a variable environment and an uncontrolled wire layout. The adaptation required by the models requires many assumptions. This case study focuses on a 10 wire configuration with the following assumptions: stationary state, identical wires, axial heat fluxes and neglected heat convection. Comparative studies between the two nodal methods and a Finite Volumes Method (FVM) are also presented and discussed. From a physical point of view, the results are more interesting. Further investigations, depending on the different parameters, should lead us to make more realistic nodal methods.

scholarly journals Computational Ice-Divide Analysis of a Cold Plane Ice Sheet Under Steady Conditions

1989 ◽  
Vol 12 ◽  
pp. 170-177 ◽  
Author(s):  
F. Szidarovszky ◽  
K. Hutter ◽  
S. Yakowitz
Keyword(s):  
Ice Sheet ◽  
Reduced Model ◽  
Stress Distributions ◽  
Field Equations ◽  
Geothermal Heat ◽  
Local Flow ◽  
Plane Flow ◽  
Basal Sliding ◽  
Flow Features ◽  
Simplifying Assumptions

The dimensionless form of the field equations and boundary conditions governing plane flow of a grounded cold ice sheet emerge from balance statements of mass, momentum, and energy. They constitute an amended version of a reduced model of ice-sheet flow, due to Morland (1984) and Hutter (1983), and circumvent the restrictions imposed by the reduced model, namely the neglect of the longitudinal stretching effects. The amended version permits satisfaction of mass balance at the ice divide for arbitrary basal sliding conditions and gives a better reproduction of the local flow features. Under very mild simplifying assumptions, namely that horizontal thermal conduction can be ignored close to the divide, we present a numerical analysis of the ice divide which has second-order accuracy. This analysis permits determination of the temperature profile, velocity, and stress distributions in a symmetric ice divide, provided that the ice-divide height, the local behavior of the accumulation and surface-temperature functions, and the geothermal heat flow are prescribed.

Feedback Mechanisms between Heterogeneous Geothermal Heat Fluxes and the Dynamic Ice Sheet Reinforce the Formation of Tunnel Valleys

2021 ◽  
Author(s):  
Sascha Barbara Bodenburg ◽  
Sönke Reiche ◽  
Christian Hübscher ◽  
Julia Kowalski
Keyword(s):  
Heat Transport ◽  
Geothermal Energy ◽  
Ice Sheet ◽  
Heat Fluxes ◽  
Scaling Analysis ◽  
Local Concentration ◽  
Geothermal Heat ◽  
Feedback Mechanisms ◽  
Computational Strategy

<p>The large variety of subglacial landforms observed on Earth are due to a complex interplay between the overlying ice sheet and the solid Earth below. While the ice cover thermally isolates the subglacial region, hence shields it from any influence by variations in the atmosphere, spatially varying geothermal heat fluxes from below may lead to the formation or reinforcement of existing subglacial landform patterns, such as tunnel valleys. An observed spatial correlation between tunnel valleys and underlying salt structures in the North German Basin is often explained mechanically. In this work, we alternatively focus on the role of heat transfer for the formation of tunnel valleys, which has not been holistically investigated until now. As salt has a higher thermal conductivity than the surrounding rocks, a local concentration of geothermal energy above salt structures may lead to increased subglacial melting rates of the overlying ice sheet. In particular, it is our goal to investigate to which extent the resulting meltwater discharge and corresponding erosion has the potential to reinforce tunnel valley formation. For our analysis, we develop a coupled computational strategy capable of determining the interplay between the temperature distribution within the heterogeneous subsurface including heat transport and ground water flow, and the overlying ice sheet. Modelling the interfacial heat flux from the subsurface into the ice sheet then allows us to infer on subglacial melt rates, which can be further assessed with respect to their role in the formation of tunnel valleys. In this contribution, we present results of a scaling analysis that takes into account the ice sheet with its internal horizontal and vertical velocity fields, the subsurface and the subglacial interfacial area. We furthermore describe a 1D computational strategy to combine the heat transport including subglacial phase change into a coupled process model allowing for investigating feedback mechanisms. Finally, we discuss strategies how this can be integrated into a full dimensional computational subsurface model, such as SHEMAT-Suite. Preliminary results for two tunnel valleys overlying salt structures in the German North Sea show that the local concentration of geothermal energy solely basing on heat conduction is only slightly augmented. The role of hydrothermal flow processes still remains to be quantified. We can therefore conclude that the geothermal distribution has a complementary effect to mechanical processes together leading to the formation of tunnel valleys.</p>

scholarly journals Deciphering Interannual Temperature Variations in Springs of the Campania Region (Italy)

Water ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 288 ◽  
Author(s):  
Micòl Mastrocicco ◽  
Gianluigi Busico ◽  
Nicolò Colombani
Keyword(s):  
Water Quality ◽  
Quality Parameters ◽  
Spring Water ◽  
Heat Fluxes ◽  
Precipitation Trend ◽  
Groundwater Temperature ◽  
Geothermal Heat ◽  
Campania Region ◽  
The Impact ◽  
Average Annual Precipitation

While the effects of climate change on the thermal regimes of surface waters have already been assessed by many studies, there is still a lack of knowledge on the effects on groundwater temperature and on the effects on spring water quality. The online available dataset of the Campania Environmental Agency (ARPAC) was analysed via spatial, temporal and statistical analyses to assess the impact of climate variability on 118 springs, monitored over the period from 2002 to 2017. The meteorological dataset was used to compute average annual precipitation and atmospheric temperatures. Spring water temperatures, electrical conductivity, pH, chloride and fluoride were selected to determine if climate variations had a significant impact on spring water quality. This study shows that the Campania region has experienced an increase of spring water temperatures of approximately 2.0 °C during the monitored period. This is well-linked with the increase of atmospheric minimum temperatures, but not with average and maximum atmospheric temperatures. The spring water temperature increases were not reflected by a concomitant change of the analysed water quality parameters. The latter were linked to the precipitation trend and other local factors, like spring altitude and the presence of geothermal heat fluxes.

scholarly journals Heat flux and the North East Greenland Ice Stream

2021 ◽  
Author(s):  
Paul D. Bons ◽  
Tamara de Riese ◽  
Steven Franke ◽  
Maria-Gema Llorens ◽  
Till Sachau ◽  
...  
Keyword(s):  
Heat Flux ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Geothermal Heat ◽  
Radiogenic Heat ◽  
East Greenland ◽  
North East ◽  
Ice Stream

<p>The prominent North East Greenland Ice Stream (NEGIS) is an exceptionally large ice stream in the Greenland Ice sheet. It is over 500 km long, originates almost at the central ice divide, and contributes significantly to overall ice drainage from the Greenland Ice sheet. Surface velocities in the inland part of the ice stream are several times higher inside NEGIS than in the adjacent ice sheet. Modelling NEGIS is still a challenge as it remains unclear what actually causes and controls the ice stream.</p><p>An elevated geothermal heat flux is one of the factors that are being considered to trigger or drive the fast flow inside NEGIS. Unfortunately, the geothermal heat flux below NEGIS and its upstream area is poorly constrained and estimates vary from close to the global average for continental crust (ca. 60 mW/m<sup>2</sup>) to values as high as almost 1000 mW/m<sup>2</sup>. The latter would cause about 10 cm/yr of melting at the base of the ice sheet.</p><p>We present a brief survey of global geothermal heat flux data, especially from known hotspots, such as Iceland and Yellowstone. Heat fluxes in these areas that are known to be among the hottest on Earth rarely, if ever, exceed 300 mW/m<sup>2</sup>. A plume hotspot or its trail can therefore not cause heat fluxes at the high end of the suggested range. Other potential factors, such as hydrothermal fluid flow and radiogenic heat, also cannot raise the heat flux significantly. We conclude that the heat flux at NEGIS is very unlikely to exceed 100-150 mW/m<sup>2</sup>, and future modelling studies on NEGIS should thus be mindful of implementing realistic geothermal heat flux values. If NEGIS is not the result of an exceptionally high heat flux, we are left with the exciting challenge to find the true trigger of this fascinating structure.</p>

scholarly journals R1234ze(E) Flow Boiling inside a 2.5 mm ID Smooth Tube and Comparison against an Equivalent Microfin Tube

2021 ◽  
Vol 11 (6) ◽  
pp. 2627
Author(s):  
Andrea Diani ◽  
Luisa Rossetto
Keyword(s):  
Flow Boiling ◽  
Experimental Tests ◽  
Test Tube ◽  
Heat Fluxes ◽  
Smooth Tube ◽  
Internal Diameter ◽  
Transfer Coefficients ◽  
Convective Boiling ◽  
Joule Effect ◽  
Global Warming Impact

The air conditioning and refrigeration industry is now dealing with an imminent substitution of widely implemented refrigerants having a non-negligible global warming impact. Among the proposed hydrofluoroolefins, R1234ze(E) has thermodynamic and transport properties close to those of R134a, and thus it can be one of its substitutes. This paper experimentally analyzes R1234ze(E) flow boiling inside a smooth tube with an internal diameter of 2.5 mm. Mass velocity is investigated from 200 to 600 kg m−2 s−1, for vapor quality from 0.15 to 0.99. The test tube is electrically heated by the Joule effect, by supplying heat fluxes from 12 to 60 kW m−2. Heat transfer coefficients and frictional pressure drops were evaluated from the experimental tests, and compared against values estimated by empirical correlations. Additional experimental tests permitted the comparison between the thermal and hydraulic characteristics of the smooth tube and those of a microfin tube with an inner diameter at the fin tip of 2.4 mm. The comparison revealed the higher contribution of convective boiling for the microfin tube compared to the smooth tube for all of the investigated working conditions.

scholarly journals On the Consumption of Antarctic Bottom Water in the Abyssal Ocean

2016 ◽  
Vol 46 (2) ◽  
pp. 635-661 ◽  
Author(s):  
Casimir de Lavergne ◽  
Gurvan Madec ◽  
Julien Le Sommer ◽  
A. J. George Nurser ◽  
Alberto C. Naveira Garabato
Keyword(s):  
Bottom Water ◽  
Heat Fluxes ◽  
Internal Tides ◽  
Antarctic Bottom Water ◽  
Geothermal Heat ◽  
Geothermal Heating ◽  
Mixing Energy ◽  
Lee Waves ◽  
Lee Wave

AbstractThe abyssal ocean is primarily filled by cold, dense waters formed around Antarctica and collectively referred to as Antarctic Bottom Water (AABW). At steady state, AABW must be consumed in the ocean interior at the same rate it is produced, but how and where this consumption is achieved remains poorly understood. Here, estimates of abyssal water mass transformation by geothermal heating and parameterized internal wave–driven mixing are presented. This study uses maps of the energy input to internal waves by tidal and geostrophic motions interacting with topography combined with assumptions about the distribution of energy dissipation to evaluate dianeutral transports induced by breaking internal tides and lee waves. Geothermal transformation is assessed based on a map of geothermal heat fluxes. Under the hypotheses underlying the constructed climatologies of buoyancy fluxes, the authors calculate that locally dissipating internal tides and geothermal heating contribute, respectively, about 8 and 5 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) of AABW consumption (upwelling), mostly north of 30°S. In contrast, parameterized lee wave–driven mixing causes significant transformation only in the Southern Ocean, where it forms about 3 Sv of AABW, decreasing the mean density but enhancing the northward flow of abyssal waters. The possible role of remotely dissipating internal tides in complementing AABW consumption is explored based on idealized distributions of mixing energy. Depending mostly on the chosen vertical structure, such mixing could drive 1 to 28 Sv of additional AABW upwelling, highlighting the need to better constrain the spatial distribution of remote dissipation. Though they carry large uncertainties, these climatological transformation estimates shed light on the qualitative functioning and key unknowns of the diabatic overturning.

scholarly journals New insights into the subglacial and periglacial hydrology of Vatnajökull, Iceland, from a distributed physical model

2003 ◽  
Vol 49 (165) ◽  
pp. 257-270 ◽  
Author(s):  
Gwenn E. Flowers ◽  
Helgi Björnsson ◽  
Finnur Pálsson
Keyword(s):  
Large Scale ◽  
Heat Fluxes ◽  
Seasonal Migration ◽  
Effective Pressure ◽  
Geothermal Heat ◽  
Future Evolution ◽  
Ice Cap ◽  
Digital Elevation ◽  
Starting Point ◽  
Glacial Discharge

AbstractWe apply a time-dependent distributed glaciohydraulic model to Vatnajökull ice cap, Iceland, aiming to determine the large-scale subglacial drainage structure, the importance of basally derived meltwater, the influence of a permeable glacier bed and Vatnajökull’s discharge contribution to major rivers in Iceland. The model comprises two coupled layers that represent the subglacial horizon perched on a subsurface aquifer in the western sector and bedrock in the eastern sector. To initialize and drive the simulations, we use digital elevation models of the ice surface and bed, the 1999/2000 measured mass balance and an estimate of subglacial geothermal heat fluxes. The modelled subglacial flow field differs substantially from that derived by hydraulic-potential calculations, and the corresponding distribution of basal effective pressure shows a strong correlation between low effective pressure and surge-prone areas in northeastern and southern sectors of Vatnajökull. Simulations suggest that geothermally derived basal melt may account for up to ∼5% of the annual glacial discharge, and buried aquifers may evacuate up to ∼30% of subglacialwater.Time-dependent tests yield estimates of the glacial discharge component in various outlet rivers and suggest a possible seasonal migration of subglacial hydraulic divides. This study of present-day Vatnajökull hydrology forms the starting point for investigations of its future evolution.

Modelling the formation and evolution of glaciovolcanic caves and chimneys.

2021 ◽  
Author(s):  
Tryggvi Unnsteinsson ◽  
Gwenn Flowers ◽  
Glyn Williams-Jones
Keyword(s):  
Flow Model ◽  
Heat Fluxes ◽  
Analytical Models ◽  
Geothermal Heat ◽  
Ice Flow ◽  
Geothermal Activity ◽  
Transient Simulations ◽  
Formation And Evolution ◽  
Bed Slope ◽  
Steady State Solutions

<p>Localised elevated subglacial or subnivean geothermal activity has the potential to influence the morphology and flow of glaciers. Under conditions where the meltwater produced by these glaciovolcanic interactions is effectively drained away from the geothermal source, glaciovolcanic voids may form. These voids can only exist if the influx of geothermal vapours/gases provides more heat for melting than can be compensated by the inflow of ice. We identify two distinct glaciovolcanic void morphologies: horizontal passageways or chambers beneath the ice/snow, termed <em>caves</em>, and vertical shafts, termed <em>chimneys</em>. Both transient and long-lived caves and chimneys have been observed, with their formation sometimes being precursory or concurrent expressions of volcanic unrest. A better understanding of these features can therefore aid volcano monitoring programs and volcanic hazard assessments. Here we investigate the relationships between glaciological and geothermal conditions and their effects on the formation and evolution of glaciovolcanic caves and chimneys. We adapt existing analytical models, originally developed to describe subglacial hydrology, to derive and balance expressions for the radial melt-opening and creep-closure to find steady-state solutions for cave and chimney geometries. The effects of localised geothermal heat fluxes on fully drained glaciovolcanic voids are further investigated using a numerical full-Stokes ice-flow model. Idealised voids, subject to a prescribed geothermally induced mass balance, are inserted within synthetic glaciers of variable bed slope and thickness. Transient simulations are then used to map out the parameter space that influences the formation and evolution of glaciovolcanic caves and chimneys.</p>

Experimental Investigation and Discussion of Heat Transfer Mechanisms During Flow Boiling in Mini-Channels Using Refrigerant R134a

2016 ◽  
Author(s):  
Nicolas La Forgia ◽  
Carlos A. Dorao ◽  
Maria Fernandino
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Bubble Nucleation ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Joule Effect ◽  
Mini Channels ◽  
Transfer Mechanisms

The main objective of this work was to investigate the heat transfer characteristics of elongated bubbles in 0.5mm diameter mini-channels using R134a as working fluid. In particular to identify the contribution of the nucleate and film boiling to the heat transfer mechanism at low thermodynamical qualities. The measurements were performed in a glass test section with several diabatic and adiabatic regions. The adiabatic region was heated by Joule effect using an ITO coating as heater. The measurement of heat transfer coefficient for elongated bubbles without the presence of bubble nucleation were compared with the case with nucleation showing that heat transfer in elongated bubbles is only larger than the case with nucleation at very small heat fluxes. In addition, heat transfer coefficient showed a dependence with the thermodynamic quality.

Computational Ice-Divide Analysis of a Cold Plane Ice Sheet Under Steady Conditions

1989 ◽  
Vol 12 ◽  
pp. 170-177 ◽  
Author(s):  
F. Szidarovszky ◽  
K. Hutter ◽  
S. Yakowitz
Keyword(s):  
Ice Sheet ◽  
Reduced Model ◽  
Stress Distributions ◽  
Field Equations ◽  
Geothermal Heat ◽  
Local Flow ◽  
Plane Flow ◽  
Basal Sliding ◽  
Flow Features ◽  
Simplifying Assumptions

The dimensionless form of the field equations and boundary conditions governing plane flow of a grounded cold ice sheet emerge from balance statements of mass, momentum, and energy. They constitute an amended version of a reduced model of ice-sheet flow, due to Morland (1984) and Hutter (1983), and circumvent the restrictions imposed by the reduced model, namely the neglect of the longitudinal stretching effects. The amended version permits satisfaction of mass balance at the ice divide for arbitrary basal sliding conditions and gives a better reproduction of the local flow features.Under very mild simplifying assumptions, namely that horizontal thermal conduction can be ignored close to the divide, we present a numerical analysis of the ice divide which has second-order accuracy. This analysis permits determination of the temperature profile, velocity, and stress distributions in a symmetric ice divide, provided that the ice-divide height, the local behavior of the accumulation and surface-temperature functions, and the geothermal heat flow are prescribed.

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