Possible effects of Mercury surface temperatures on the exosphere

2020 ◽  
Author(s):  
Edoardo Rognini ◽  
Alessandro Mura ◽  
Maria Teresa Capria ◽  
Angelo Zinzi ◽  
Anna Milillo ◽  
...  
Keyword(s):  
Internal Heat ◽  
Thermal Response ◽  
Circulation Model ◽  
Sodium Content ◽  
Heat Propagation ◽  
Conductive Heat ◽  
High Porosity ◽  
Surface Temperatures ◽  
Thermophysical Model ◽  
The One

<div> <p>The BepiColombo mission is the first European mission to Mercury; the spacecraft will reach its destination in December 2025, and will study in detail the surface, the exosphere and the magnetosphere of the planet. </p> </div> <div> <p>We have developed a thermophysical model with the aim to analyze the dependence of the temperature of the surface and of the layers close to it on the assumptions on the thermophysical properties of the soil. The code solves the one-dimensional heat equation, assumes purely conductive heat propagation and no internal heat sources; the surface is assumed to be composed of a regolith layer with high porosity and density increasing with depth. The illumination conditions are calculated by using a Mercury shape model and the SPICE routines [1]. </p> </div> <div> <p>The model will help us to interpret the data that will be provided by the instruments onboard the BepiColombo mission. Preliminary calculations have been carried out to analyze the thermal response of the soil as a function of thermal conductivity. The model is currently also used to study the sodium content in the planet's exosphere, whose origin is under investigation [2]; the MESSENGER mission has measured the exospheric sodium content as a function of time, detecting an increase at the "cold poles" (so called because of their lower than average temperature). We therefore want to study the effect of surface temperatures on the sodium content in the exosphere; for this purpose, the temperature distribution calculated with the code is used together with an atmospheric circulation model that calculates the exospheric sodium content [3]. </p> </div> <div> <p>A simplified version of the thermophysical code is almost ready to be available to the scientific community through MATISSE [4], the software developed at the SSDC in ASI and available at https://tools.ssdc.asi.it/Matisse. </p> </div> <p>[1] Acton, C. H. (1996), Planetary and Space Science, 44, 65-70<br />[2] Cassidy, T., et al. (2016), GRL, 43, 11 121-128<br />[3] Mura, A., et al. (2009), Icarus, 1, 1-11<br />[4] Zinzi, A., et al. (2016), Astronomy & Computing, 15, 16-28</p>

Quantitative Phase Shift Analysis for 3D Defect Localization Using Lock-in Thermography

2011 ◽  
Author(s):  
Christian Schmidt ◽  
Frank Altmann
Keyword(s):  
Phase Shift ◽  
Internal Heat ◽  
Thermal Response ◽  
Heat Propagation ◽  
Quantitative Phase ◽  
Material Layer ◽  
Shift Analysis ◽  
Reference Device ◽  
Periodic Stimulation ◽  
Lock In

Abstract It was already demonstrated, that the method of Lock-in Thermography (LIT) enables 3D localization of thermal active defects, e.g. electrical shorts and resistive opens, on die level and within fully packaged single and multichip devices [1,2]. The depth of a defect can be derived from phase shift measurements of the defective compared to a reference device For a general approach of this method, thermal modeling is used and verified by experimental data to investigate the internal heat propagation under periodic stimulation in correlation to the LIT measuring process. [3]. A basic requirement for the successful application of the method is a precise and reproducible measurement of both the thermal material properties of each material layer and the phase shift between the internal heat excitation and thermal response measured by LIT. Significant influences from the material and measurement setup to the detected phase shift have to be identified and taken into account. However, to identify and distinguish the relevant influences measurements with defined internal heat sources are necessary which are presented in this paper. First, the relationship between geometrical thickness of a material layer and the resulting thermal parameters for both homogeneous and heterogeneous materials are measured and discussed. A new measurement setup generating a defined point heat source will be presented to calibrate the LIT system for quantitative phase shift measurements and to determine the phase shift to thickness parameters of single material layers. In addition the variation of the phase shift caused by the defect geometry and the defect environment will be investigated. Finally, a case study is presented comparing the experimental results to the obtained results from a real stacked die device.

Numerical simulation of the tree higro-thermal response in forest fire environment

2020 ◽  
pp. 57-65
Author(s):  
Eusébio Conceiçã ◽  
João Gomes ◽  
Maria Manuela Lúcio ◽  
Jorge Raposo ◽  
Domingos Xavier Viegas ◽  
...  
Keyword(s):  
Forest Fire ◽  
Numerical Study ◽  
Thermal Response ◽  
View Factor ◽  
Tree Model ◽  
Pine Tree ◽  
Surface Temperatures ◽  
Fire Environment ◽  
Fire Front ◽  
Heat Exchanges

This paper refers to a numerical study of the hypo-thermal behaviour of a pine tree in a forest fire environment. The pine tree thermal response numerical model is based on energy balance integral equations for the tree elements and mass balance integral equation for the water in the tree. The simulation performed considers the heat conduction through the tree elements, heat exchanges by convection between the external tree surfaces and the environment, heat exchanges by radiation between the flame and the external tree surfaces and water heat loss by evaporation from the tree to the environment. The virtual three-dimensional tree model has a height of 7.5 m and is constituted by 8863 cylindrical elements representative of its trunks, branches and leaves. The fire front has 10 m long and a 2 m high. The study was conducted taking into account that the pine tree is located 5, 10 or 15 m from the fire front. For these three analyzed distances, the numerical results obtained regarding to the distribution of the view factors, mean radiant temperature and surface temperatures of the pine tree are presented. As main conclusion, it can be stated that the values of the view factor, MRT and surface temperatures of the pine tree decrease with increasing distance from the pine tree in front of fire.

A Stefan problem in a Bridgman crystal grower

1995 ◽  
Vol 6 (3) ◽  
pp. 191-199
Author(s):  
P. den Decker ◽  
R. van der Hout ◽  
C. J. Van Duijn ◽  
L. A. Peletier
Keyword(s):  
Critical Speed ◽  
Internal Heat ◽  
Mushy Region ◽  
Dimensional Model ◽  
Real Situation ◽  
One Dimensional ◽  
Dimensional Approximation ◽  
The One ◽  
Strong Curvature ◽  
Bridgman Crystal Grower

We discuss a one-dimensional model for a Bridgman crystal grower, where the removal of heat is described by an internal heat sink. A consequence is the apparent existence of mushy regions for relatively large velocities of the cooling machine; these mushy regions are an artefact of the one-dimensional approximation. We show that for some types of cooling profiles there exists a critical speed for the existence of mushy regions, whereas for different cooling profiles no such critical speed exists. The presence of a mushy region may indicate a strong curvature of the liquid/solid interface in the real situation.

scholarly journals A method for solving a boundary value problem in a multilayered area

2020 ◽  
Keyword(s):  
Boundary Condition ◽  
Heat Conduction ◽  
Boundary Value ◽  
Internal Heat ◽  
Electrical Machine ◽  
Problem Solution ◽  
Conductive Heat ◽  
Heat Sources ◽  
Internal Layers ◽  
Internal Heat Sources

A mathematical model of thermal process in an electrical machine was built as an example, presented as a three-layer cylinder where internal heat sources operate in one of the layers and heat is submitted to the other two by means of heat conduction. A method of solving the boundary-value problems for heat conduction equation in a complex area – a multi-layered cylinder with internal heat sources operating in one part of the layers and external ones in another part, is proposed. A method of problem solution in conditions of uncertainty of one of the boundary condition at the layers interface with conductive heat exchange between the layers is reviewed. The principle of method lies in the averaging of temperature distributions radially in the internal layers. As a result of transformations at the layers interface a boundary condition of the impedance-type conjugation appears. The analytical and numeric-analytical solutions of simplified problems were obtained.

scholarly journals High-Fidelity Calculation of Effective Thermal Response of Composite Media With Heat Generation Source

2020 ◽  
Author(s):  
Kevin Irick ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Behavior ◽  
Nuclear Fuel ◽  
Heat Generation ◽  
Thermal Response ◽  
Thermal Conditions ◽  
Unit Cell ◽  
High Fidelity ◽  
Conductive Heat

Abstract The complexity of conductive heat transfer in a structure increases with heterogeneity (e.g., multi-component solid-phase systems with a source of internal thermal heat generation). Any discontinuity of material property — especially thermal conductivity — would warrant a thorough analysis to evaluate the thermal behavior of the system of interest. Heterogeneous thermal conditions are crucial to heat transfer in nuclear fuel assemblies, because the thermal behavior within the assemblies is governed significantly by the heterogeneous thermal conditions at both the system and component levels. A variety of materials have been used as nuclear fuels, the most conventional of which is uranium dioxide, UO2. UO2 has satisfactory chemical and irradiation tolerances in thermal reactors, whereas the low thermal conductivity of porous UO2 can prove challenging. Therefore, the feasibility of enhancing the thermal conductivity of oxide fuels by adding a high-conductivity secondary solid component is still an important ongoing topic of investigation. Undoubtedly, long-term, stable development of clean nuclear energy would depend on research and development of innovative reactor designs and fuel systems. Having a better understanding of the thermal response of the unit cell of a composite that represents a fuel matrix cell would help to develop the next generation of nuclear fuel and understand potential performance enhancements. The aim of this article is to provide an assessment of a high-fidelity computational model response of heterogeneous materials with heat generation in circular fillers. Two-dimensional, steady-state systems were defined with a circular, heat-generating filler centered in a unit-cell domain. A Fortran-based finite element method (FEM) code was used to solve the heat equation on an unstructured triangular mesh of the systems. This paper presents a study on the effects of a heat-generating filler material’s relative size and thermal conductivity on effective thermal conductance, Geff, within a heterogenous material. Code verification using the method of manufactured solution (MMS) was employed, showing a second-order accurate numerical implementation. Solution verification was performed using a global deviation grid convergence index (GCI) method to assess solution convergence and estimate solution numerical uncertainty, Unum. Trend results are presented, showing variable response in Geff to filler size and thermal conductivity.

Grinding Performance of Porous Diamond Wheels on Different Materials

2011 ◽  
Vol 189-193 ◽  
pp. 3191-3197
Author(s):  
Qiu Lian Dai ◽  
Can Bin Luo ◽  
Fang Yi You
Keyword(s):  
Grain Size ◽  
Specific Energy ◽  
Experimental Results ◽  
Grinding Process ◽  
High Porosity ◽  
Grinding Forces ◽  
Abrasive Grain ◽  
Grinding Conditions ◽  
Medium Porosity ◽  
The One

In this paper, metal-bonded diamond wheels of different sized abrasive grain with different porosity were fabricated. Grinding experiments with these wheels on three kinds of materials were carried out under different grinding conditions. Experimental results revealed that wheel with high porosity (38%) had smaller grinding forces and specific energy than the one with a medium porosity (24%) on grinding G603. However, on grinding harder materials like Red granite or ceramics of Al2O3, the wheel with 38% porosity had bigger grinding forces and specific energy than the wheel with 24% porosity. Both wheels exhibited good self-sharpening capability during the grinding process of G603 and Red granite, but on grinding ceramics of Al2O3 the wheel with 38% porosity displayed in dull state during the grinding process . With the same porosity, the grinding forces of the wheel with a grain size of 230/270 US mesh were lower than the one with a grain size of W10 when grinding Red granite and ceramics of Al2O3. However revising results were obtained on grinding G603.

scholarly journals GCM Systematic Error Correction and Specification of the Seasonal Mean Pacific–North America Region Atmosphere from Global SSTs

1999 ◽  
Vol 12 (1) ◽  
pp. 273-288 ◽  
Author(s):  
Thomas M. Smith ◽  
Robert E. Livezey
Keyword(s):  
North America ◽  
General Circulation ◽  
Southern Oscillation ◽  
Circulation Model ◽  
Systematic Errors ◽  
Sea Surface ◽  
Average Output ◽  
Surface Temperatures ◽  
Model Variability ◽  
The U.S

Abstract Specifications of 1- and 3-month mean Pacific–North America region 700-hPa heights and U.S. surface temperatures and precipitation, from global sea surface temperatures (SSTs) and the ensemble average output of multiple runs of a general circulation model with the same SSTs prescribed, were explored with canonical correlation analysis. In addition to considerable specification skill, the authors found that 1) systematic errors in SST-forced model variability had substantial linear parts, 2) use of both predictor fields usually enhanced specification performance for the U.S. fields over that for just one of the predictor fields, and 3) skillful specification and model correction of the heights and temperatures were also possible for nonactive or transitional El Niño–Southern Oscillation situations.

Investigation of Building Passive Thermal Storage for Optimal Heating System Design

2014 ◽  
Author(s):  
Oluwaseyi Ogunsola ◽  
Li Song
Keyword(s):  
Energy Use ◽  
Thermal Characteristics ◽  
Internal Heat ◽  
Thermal Storage ◽  
Heating System ◽  
Building Envelope ◽  
Conductive Heat ◽  
Fundamental Study ◽  
Worst Case ◽  
Simplified Approach

Heating and cooling load calculations are critical to size Heating, Ventilation and Air conditioning (HVAC) systems and determine energy use of their operations. The ASHRAE (2009) model, which is most commonly used for heating load calculations, adopts a simplified approach by considering only steady-state instantaneous conductive heat transfer and ignoring internal heat gains and thermal storage effects. Those assumptions evaluate the worst case conditions which can reasonably occur at nights when the outdoor air temperature is lowest and with no inputs from solar, occupants, lights, or any electronic devices. However, due to thermal storage effect, heat generated in daytime can be still stored in buildings. Such ignorance leads to significantly over-sized heating system, high initial cost and a higher cost of energy uses. On the other hand, by considering passive thermal storage of buildings and allowing space air to drift to reasonably lower values, buildings need to be warmed up in the morning before being occupied. The worst case conditions might happen in the morning warm-up period, when heating is needed. This study therefore examines the thermal response of different constructions (heavy, medium, and light) of the building envelope and investigates the effect of their passive thermal storage on the size of the heating system. Results show tremendous opportunities for downsizing of the heating system while still maintaining thermal comfort requirements. As such, this paper is a fundamental study of building thermal characteristics in order to investigate the potentials of establishing a new heating device design standard.

Granites and crustal heat budget

2019 ◽  
Vol 491 (1) ◽  
pp. 77-100 ◽  
Author(s):  
Jean-François Moyen
Keyword(s):  
Heat Production ◽  
Heat Budget ◽  
Internal Heat ◽  
Balance Model ◽  
Conductive Heat ◽  
Crustal Melting ◽  
Abstract Approach ◽  
Production And Consumption ◽  
Conductive Heat Flux ◽  
Basalt Differentiation

AbstractThe origin of large I-type batholiths remains a disputed topic. One model states that I-type granites form by partial melting of older crustal lithologies (amphibolites or intermediate igneous rocks). In another view, granites are trapped rhyolitic liquids occurring at the end of fractionation trends defining a basalt–andesite–dacite–rhyolite series. This paper explores the thermal implications of both scenarios, using a heat balance model that abstracts the heat production and consumption during crustal melting. Heat is consumed by melting and by losses through the surface (conductive or advective, as a result of eruption). It is supplied as a basal conductive heat flux, as internal heat production or as advective heat carried by an influx of hot basalt into the crust. Using this abstract approach, it is possible to explore the role different parameters play in the balance of granites formed by differentiation of basalts or by crustal melting. Two end-member situations appear equally favourable to generating large volumes of granites: (1) short-lived environments dominated by high basaltic flux, where granites result mostly from basalt differentiation; and (2) long-lived systems with no or minimal basalt flux, with granites resulting chiefly from crustal melting.

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