High Volumetric Heat Capacity Research Articles

Observations of Near-Surface Heat-Flux and Temperature Profiles Through the Early Evening Transition over Contrasting Surfaces

Near-surface turbulence data from the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program are used to study countergradient heat fluxes through the early evening transition. Two sites, subjected to similar large-scale forcing, but with vastly different surface and sub-surface characteristics, are considered. The Playa site is situated at the interior of a large dry lakebed desert with high sub-surface soil moisture, shallow water table, and devoid of vegetation. The Sagebrush site is located in a desert steppe region with sparse vegetation and little soil moisture. Countergradient sensible heat fluxes are observed during the transition at both sites. The transition process is both site and height dependent. At the Sagebrush site, the countergradient flux at 5 m and below occurs when the sign change of the sensible heat flux precedes the local temperature gradient sign change. For 10 m and above, the countergradient flux occurs when the sign change of the sensible heat flux follows the local temperature gradient sign change. At the Playa site, the countergradient flux at all tower levels occurs when the sign change of the sensible heat flux follows the local temperature gradient sign change. The phenomenon is explained in terms of the mean temperature and heat-flux evolution. The temperature gradient sign reversal is a top-down process while the flux reversal occurs nearly simultaneously at all heights. The differing countergradient behaviour is primarily due to the different subsurface thermal characteristics at the two sites. The combined high volumetric heat capacity and high thermal conductivity at the Playa site lead to small vertical temperature gradients that affect the relative magnitude of terms in the heat-flux tendency equation. A critical ratio of the gradient production to buoyant production of sensible heat flux is suggested so as to predict the countergradient behaviour.

Stability Testing of Thermal Oil in Direct Contact with Rocks used as Filler Material for Thermal Energy Storage in CSP Power Plants

Abstract A Thermocline Thermal Energy Storage (TES) system potentially offers a cheap and simple way of achieving dispatchability of energy after sunset or during intermittent cloudy weather conditions. The system performance depends on the properties of the suitable media selected. As very promising solid TES material, natural rocks can be chosen as filler material for energy storage system owing their availability and many advantages such as high volumetric heat capacity and stable physical and chemical performance. In previous tests, quartzite rock was identified as a potential filler material for TES. In the present paper, the compatibility of the heat transfer fluid (HTF) with rocks and silica sand was tested in laboratory under defined conditions. Physicochemical and thermal characterizations of the studied materials were performed in order to evaluate their sustainability after extended time over a range of temperature. It has been concluded that no significant deterioration of tested oil aged in contact with quartzite and silica sand can affect the performance of the thermocline thermal energy storage system.

Geothermal energy: deep sources in Victoria

Geothermal energy is heat stored naturally within the rocks of the earth. The higher the temperature of the rock, the more thermal energy is potentially available. In general, temperature increases with depth so deeper rocks store larger amounts of geothermal energy. Water has a higher volumetric heat capacity than most solid minerals, so saturated porous rocks tend to store larger amounts of heat than non-porous rocks. Under the right circumstances, geothermal energy can be economically extracted and put to use either directly (for example, to heat buildings) or by converting it to electrical energy. There are already two geothermal power generators in Australia (a 120 kWe plant at Birdsville, Queensland, and one 1 MWe plant at Innamincka, South Australia) and a range of direct applications of geothermal energy (heated buildings, swimming pools and spas)

A buoyantly-driven shutdown rod concept for passive reactivity control of a Fluoride salt-cooled High-temperature Reactor

This paper presents a novel buoyantly-driven shutdown rod concept for use in Fluoride salt-cooled High-temperature Reactors (FHRs). The baseline design considered here is a 900MWth modular version of the FHR class called the Pebble Bed Advanced High-Temperature Reactor (PB-AHTR) that uses pebble fuel. Due to the high volumetric heat capacity of the primary coolant, the FHRs operate with a high power density core with a similar average coolant temperature as in modular helium reactors. The reactivity control system for the baseline PB-AHTR uses a novel buoyantly-driven shutdown rod system that can be actively or passively activated during reactor transients. In addition to a traditional active insertion mechanism, the new shutdown rod system is designed to also operate passively, fulfilling the role of a reserve shutdown system. The physical response of the shutdown rod was simulated both computationally and experimentally, using scaling arguments where applicable, with an emphasis on key phenomena identified by a preliminary Phenomena Identification and Ranking Table (PIRT) study. This paper presents results from both the pre-predicted simulation and experimental validation efforts.

Stability of a cable in conduit conductor under fast magnetic field variations

Under fast magnetic field variations, ac losses are deposited in a Cable in Conduit Conductor (CICC). The corresponding power losses are transferred to helium thanks to the high wetted perimeter of the conductor. The critical energy of the CICC can be expected to be proportional to the high volumetric heat capacity of helium and to the temperature margin. To confirm the expectations, stability tests under a transversal pulsed magnetic field were performed in the Sultan test facility on a prototype JT-60SA conductor sample. The shape of the magnetic field variation as a function of time is a truncated sinusoid. The experimental results are not totally in agreement with expected behavior on two particular points: - the deposited energy in the conductor as a function of the pulsed field amplitude, measured by calorimetry, deviates from the expected quadratic behavior for coupling losses. The deviation is also increasingly dependent on the transport current. - at a given Sultan background magnetic field, the critical energies at low temperature margins are reduced in comparison with expected values. An explanation based on the saturation of parts of the cable is proposed.

Potential of Nanoparticle-Enhanced Ionic Liquids (NEILs) as Advanced Heat-Transfer Fluids

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTPotential of Nanoparticle-Enhanced Ionic Liquids (NEILs) as Advanced Heat-Transfer FluidsNicholas J. Bridges, Ann E. Visser, and Elise B. Fox*View Author Information Savannah River National Laboratory, Aiken, South Carolina 29808, United StatesTelephone: 803-507-8560. E-mail: [email protected]Cite this: Energy Fuels 2011, 25, 10, 4862–4864Publication Date (Web):September 26, 2011Publication History Received8 August 2011Revised26 September 2011Published online4 October 2011Published inissue 20 October 2011https://doi.org/10.1021/ef2012084Copyright © 2011 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1212Altmetric-Citations98LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (680 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Fluids,Heat capacity,Salts,Solvents,Thermal stability Get e-Alerts

Abrasive and slurry wear behavior of chilled aluminum alloy (A356) reinforced with fused silica (SiO2p) metal matrix composites

This paper describes the fabrication and testing of aluminum alloy MMCs reinforced with fused silica particles cast in sand moulds containing metallic and nonmetallic chills. Fused silica particles of size 50–100μm were dispersed (3–12wt.%) into the matrix. The resulting composites cast were tested for their microstructure, strength, hardness, and wear behavior. Microstructural studies indicate good bonding along with uniform distribution of the dispersoid. Strength, hardness and wear resistance increase up to 9wt.% additions of dispersoid and copper chill was found to be the best because of its high volumetric heat capacity.

Microstructure, mechanical properties and wear behavior of metallic, nonmetallic and deep cryogenically chilled ASTM A216 WCB steel

This paper deals with the production of Deep Cryogenically Chilled (DCC) ASTM A216 WCB steel (plane carbon group) having 0.5% chromium, subject to different chilling rates to study the effect of chilling on microstructure and mechanical properties. In this investigation, metallic, nonmetallic and subzero chills (one each) were used. The specimens taken from casting were tested for their strength, hardness and wear behavior. Results of the investigation reveal that chilling rate and addition of chromium (0.5%) has improved both mechanical properties (strength and hardness) and wear resistance of the steel developed. Out of all the chills, subzero chill is found to be good in improving mechanical properties because of its high volumetric heat capacity (VHC). It is concluded from the above investigation that type of chill and chilling rate has an effect on mechanical properties.

Heat Transfer Analysis of Air-to-Carbon Dioxide Two-Phase Heat Absorption and Supercritical Heat Rejection

Regulations restricting the present and future use of fluorocarbon-based refrigerants have prompted a worldwide investigation of new refrigerants and refrigeration cycles. In particular, carbon dioxide is a fluid with a history of being used as a refrigerant that has recently been considered for certain applications that may take advantage of its unique thermophysical properties. The high volumetric heat capacity of carbon dioxide is a particular feature that could make a carbon-dioxide-based refrigerating/air-conditioning device appropriate for a weight or space-limited application. This study presents a comparison of heat-exchanger models of the heat absorption (evaporation) and heat rejection process for both carbon dioxide and R-22 air-conditioning cycles. The heat exchangers were modeled as single straight tubes with outside fins of constant thickness and spacing. Diameters for each tube were based on operating pressure and allowable power loss. The required length, weight, and volume for the heat exchangers were determined and compared.