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R.s. Misra - One of the best experts on this subject based on the ideXlab platform.
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Thermal stratification with thermosyphon effects in solar water heating systems
Energy Conversion and Management, 1994Co-Authors: R.s. MisraAbstract:Abstract Thermal stratification in hot water Storage tanks is required for the thermosyphon effect in solar water heating systems. A model of a thermally Stratified Storage tank is described, and explicit expressions are obtained for the water temperature in the Storage tank, which include the effects of conduction in adjacent layers. Also given is a comparison of theoretical and experimental results.
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Evaluation of thermal stratification in thermosyphonic solar water heating systems
Energy Conversion and Management, 1993Co-Authors: R.s. MisraAbstract:Abstract Thermal stratification in hot water Storage tanks is required for the thermosyphonic effect in solar water heating systems. A simple transient thermal modelling of the Stratified Storage tank is described in this paper, and comparisons of the theoretically calculated values and experimental results have been made. Good agreement between the theoretical and experimental results proves the validity of the proposed transient thermal model.
Radhey Shyam Mishra - One of the best experts on this subject based on the ideXlab platform.
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Thermal stratification in thermosyphonic solar water heating systems
Energy Conversion and Management, 1991Co-Authors: Radhey Shyam MishraAbstract:Abstract Thermal stratification in the Storage tank is essential to provide a thermosyphonic effect in water heating systems, and it also helps to reduce heat losses. A periodic modelling of thermally Stratified Storage tanks has been presented, and comparisons of theoretical and experimental results have been made in this paper.
Patrick Bachèlery - One of the best experts on this subject based on the ideXlab platform.
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Integrating field, textural, and geochemical monitoring to track eruption triggers and dynamics: a case study from Piton de la Fournaise
Solid Earth, 2018Co-Authors: Lucia Gurioli, Andrea Di Muro, Ivan Vlastélic, Séverine Moune, Simon Thivet, Marina Valer, Nicolas Villeneuve, Guillaume Boudoire, Aline Peltier, Patrick BachèleryAbstract:Abstract. The 2014 eruption at Piton de la Fournaise (PdF), La Reunion, which occurred after 41 months of quiescence, began with surprisingly little precursory activity and was one of the smallest so far observed at PdF in terms of duration (less than 2 days) and volume (less than 0.4 × 106 m3). The pyroclastic material was composed of golden basaltic pumice along with fluidal, spiny iridescent and spiny opaque basaltic scoria. Density analyses performed on 200 lapilli reveal that while the spiny opaque clasts are the densest (1600 kg m−3) and most crystalline (55 vol. %), the golden pumices are the least dense (400 kg m−3) and crystalline (8 vol. %). The connectivity data indicate that the fluidal and golden (Hawaiian-like) clasts have more isolated vesicles (up to 40 vol. %) than the spiny (Strombolian-like) clasts (0–5 vol. %). These textural variations are linked to primary pre-eruptive magma Storage conditions. The golden and fluidal fragments track the hotter portion of the melt, in contrast to the spiny fragments and lava that mirror the cooler portion of the shallow reservoir. Exponential decay of the magma ascent and output rates through time revealed depressurization of the source during which a Stratified Storage system was progressively tapped. Increasing syn-eruptive degassing and melt–gas decoupling led to a decrease in the explosive intensity from early fountaining to Strombolian activity. The geochemical results confirm the absence of new input of hot magma into the 2014 reservoir and confirm the emission of a single shallow, differentiated magma source, possibly related to residual magma from the November 2009 eruption. Fast volatile exsolution and crystal–melt separation (second boiling) were triggered by deep pre-eruptive magma transfer and stress field change. Our study highlights the possibility that shallow magma pockets can be quickly reactivated by deep processes without mass or energy (heat) transfer and produce hazardous eruptions with only short-term elusive precursors.
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Integrating field, textural, and geochemical monitoring to track eruption triggers and dynamics: a case study from Piton de la Fournaise
Solid Earth, 2018Co-Authors: Lucia Gurioli, Andrea Di Muro, Ivan Vlastélic, Séverine Moune, Simon Thivet, Marina Valer, Nicolas Villeneuve, Guillaume Boudoire, Aline Peltier, Patrick BachèleryAbstract:The 2014 eruption at Piton de la Fournaise (PdF), La Réunion, which occurred after 41 months of quiescence, began with surprisingly little precursory activity and was one of the smallest so far observed at PdF in terms of duration (less than 2 days) and volume (less than 0.4 × 10 6 m 3). The pyroclastic material was composed of golden basaltic pumice along with fluidal, spiny iridescent and spiny opaque basaltic scoria. Density analyses performed on 200 lapilli reveal that while the spiny opaque clasts are the densest (1600 kg m −3) and most crystalline (55 vol. %), the golden pumices are the least dense (400 kg m −3) and crystalline (8 vol. %). The con-nectivity data indicate that the fluidal and golden (Hawaiian-like) clasts have more isolated vesicles (up to 40 vol. %) than the spiny (Strombolian-like) clasts (0–5 vol. %). These tex-tural variations are linked to primary pre-eruptive magma Storage conditions. The golden and fluidal fragments track the hotter portion of the melt, in contrast to the spiny fragments and lava that mirror the cooler portion of the shallow reservoir. Exponential decay of the magma ascent and output rates through time revealed depressurization of the source during which a Stratified Storage system was progressively tapped. Increasing syn-eruptive degassing and melt–gas de-coupling led to a decrease in the explosive intensity from early fountaining to Strombolian activity. The geochemical results confirm the absence of new input of hot magma into the 2014 reservoir and confirm the emission of a single shallow , differentiated magma source, possibly related to residual magma from the November 2009 eruption. Fast volatile ex-solution and crystal–melt separation (second boiling) were triggered by deep pre-eruptive magma transfer and stress field change. Our study highlights the possibility that shallow magma pockets can be quickly reactivated by deep processes without mass or energy (heat) transfer and produce hazardous eruptions with only short-term elusive precursors.
Nesreen Ghaddar - One of the best experts on this subject based on the ideXlab platform.
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STUDY OF CHARGING OF Stratified Storage TANKS WITH FINITE WALL THICKNESS
International Journal of Energy Research, 1997Co-Authors: Nesreen Ghaddar, A. M. Al-maarafieAbstract:This paper presents a numerical and experimental study of finite wall thickness on stratification during charging of soar thermal Storage tanks. A numerical two-dimensional spectral-element model has been used. Predictions of the model are compared with experimental data, and with a one-dimensional plug flow model. The fluid inlet effect on the stratification is minimized in the experiments by the use of a proper diffuser design with a settling mesh. Both heat conduction in the tank wall and the developing flow in the tank have a significant effect on stratification during charging at low flow rates. The one-dimensional plug flow model is shown to be inferior to the two-dimensional model in representing the experimental data. Yet, a simple one-dimensional flow model corrected for both centreline velocity and mixing effects has given comparable results to the more expensive two-dimensional model.
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Stratified Storage tank influence on performance of solar water heating system tested in Beirut
Renewable Energy, 1994Co-Authors: Nesreen GhaddarAbstract:This paper presents an experimental and numerical study to evaluate the performance of an active solar water heating system that uses a Stratified Storage tank in both natural and forced circulation operation modes. A new inlet diffuser design was used in the tank to enhance stratification, and the performance of the solar water heating system was compared to heating systems with other tank inlet designs. A simulation program is used for modeling the thermal behavior of the Stratified-tank solar water heating system. Comparison of the resulting calculations with experimental data show good agreement. System efficiencies as high as 60% are observed in the Beirut climate. A substantial increase of up to 20% in the energy delivered is observed when stratification is employed in the Storage tank, as compared with the fully mixed tank model. The simulation model is then applied for actual Beirut weather to predict the monthly useful energy gain from using Stratified-tank solar water heating systems against the fully mixed tank model.
A. Benbassou - One of the best experts on this subject based on the ideXlab platform.
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Review on Solar Thermal Stratified Storage Tanks (STSST): Insight on stratification studies and efficiency indicators
Solar Energy, 2018Co-Authors: Saïf Ed-dîn Fertahi, Abdelmajid Jamil, A. BenbassouAbstract:Abstract This review is a synthesis of miscellaneous recent experimental and numerical studies carried out on Stratified Storage tanks for individual and collective solar hot water production applications. In fact, sensitive and latent thermal Storage remains very important, because the use of the produced solar thermal energy is not usually instantaneous. Hence, the necessity to properly size and design hot water Storage tanks to achieve an increased thermal performance during an applied charging/discharging cycles. This review was written in three parts. The first part provided a sharp insight of the recent studies that have been carried out on the Storage tanks connected to solar water heaters (SWHs). Horizontal thermal Storage tanks of SWH integrating Evacuated Tube Collectors (ETCs) with heat pipe were also considered in this review. In addition, the experimental approach often used to assess thermal Stratified hot water Storage tanks was synthesized. Moreover, innovation studies aimed at increasing the thermal efficiency of the Storage tanks were presented, either by integrating PCMs or by submerging components such as porous or tilted flat plates inside the tank. The second part of this review presents the equations setting to be established to ensure the physical modeling of thermal stratification within Storage tanks. Indeed, two approaches have been detailed: the three-dimensional CFD approach and the two-dimensional formulation based on the introduction of the vorticity stream function equation. Finally yet importantly, the third part of this review highlighted a set of thermal performance indicators usually used by the scientific community to evaluate the thermal yield of hot water Storage tanks.