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Wonkyong Song - One of the best experts on this subject based on the ideXlab platform.

  • exploring the concept of compressed air energy storage caes in lined rock caverns at shallow depth a Modeling Study of air tightness and energy balance
    Applied Energy, 2012
    Co-Authors: Jonny Rutqvist, Choon Sunwoo, Wonkyong Song
    Abstract:

    This paper presents a numerical Modeling Study of coupled thermodynamic, multiphase fluid flow and heat transport associated with underground compressed air energy storage (CAES) in lined rock caverns. Specifically, we explored the concept of using concrete lined caverns at a relatively shallow depth for which constructing and operation costs may be reduced if air tightness and stability can be assured. Our analysis showed that the key parameter to assure long-term air tightness in such a system was the permeability of both the concrete lining and the surrounding rock. The analysis also indicated that a concrete lining with a permeability of less than 1×10−18m2 would result in an acceptable air leakage rate of less than 1%, with the operation pressure range between 5 and 8MPa at a depth of 100m. It was further noted that capillary retention properties and the initial liquid saturation of the lining were very important. Indeed, air leakage could be effectively prevented when the air-entry pressure of the concrete lining is higher than the operation air pressure and when the lining is kept at relatively high moisture content. Our subsequent energy-balance analysis demonstrated that the energy loss for a daily compression and decompression cycle is governed by the air-pressure loss, as well as heat loss by conduction to the concrete liner and surrounding rock. For a sufficiently tight system, i.e., for a concrete permeability of less than 1×10−18m2, heat loss by heat conduction tends to become proportionally more important. However, the energy loss by heat conduction can be minimized by keeping the air-injection temperature of compressed air closer to the ambient temperature of the underground storage cavern. In such a case, almost all the heat loss during compression is gained back during subsequent decompression. Finally, our numerical simulation Study showed that CAES in shallow rock caverns is feasible from a leakage and energy efficiency viewpoint. Our numerical approach and energy analysis will next be applied in designing and evaluating the performance of a planned full-scale pilot test of the proposed underground CAES concept.

  • Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A Modeling Study of air tightness and energy balance
    Applied Energy, 2012
    Co-Authors: Hyung-mok Kim, Jonny Rutqvist, Choon Sunwoo, Dong-woo Ryu, Byung-hee Choi, Wonkyong Song
    Abstract:

    Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A Modeling Study of air tightness and energy balance Hyung-Mok Kim 1 , Jonny Rutqvist 2 , Dong-Woo Ryu 1 , Choon Sunwoo 1 , Won-Kyong Song 1 Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, 305-350 Korea Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720 U.S.A. September 28, 2011

Liang Xia - One of the best experts on this subject based on the ideXlab platform.

  • A Modeling Study on alleviating uneven defrosting for a vertical three-circuit outdoor coil in an air source heat pump unit during reverse cycle defrosting
    Applied Energy, 2016
    Co-Authors: Mengjie Song, Liang Xia
    Abstract:

    Reverse cycle defrosting is the most widely used standard defrosting method for air source heat pump (ASHP) units. It was suggested in previous experimental studies that downwards flowing of the melted frost over a vertical multi-circuit outdoor coil in an ASHP unit has negative effects on reverse cycle defrosting performance. To quantitatively Study the negative effects, an experimental Study and a Modeling Study on draining away locally the melted frost for an experimental ASHP unit with a three-circuit outdoor coil were carried out and separately reported. However, for exiting ASHP units, it is hardly possible to install water collecting trays between circuits. To alleviate uneven defrosting for a vertical multi-circuit outdoor coil in an existing ASHP unit, an effective alternative is to vary the heat supply to each refrigerant circuit by varying the opening values of modulating valves installed at an inlet pipe to each circuit. In this paper, a Modeling Study on varying heat (via refrigerant) supply to each refrigerant circuit in a three-circuit outdoor coil to alleviate uneven defrosting is reported. Finally, in the designed three Study cases, defrosting energy use could be decreased to 94.6%, as well as a reduction of 7 s in defrosting duration by fully closing the modulating valve on the top circuit when its defrosting terminated.

Jonny Rutqvist - One of the best experts on this subject based on the ideXlab platform.

  • exploring the concept of compressed air energy storage caes in lined rock caverns at shallow depth a Modeling Study of air tightness and energy balance
    Applied Energy, 2012
    Co-Authors: Jonny Rutqvist, Choon Sunwoo, Wonkyong Song
    Abstract:

    This paper presents a numerical Modeling Study of coupled thermodynamic, multiphase fluid flow and heat transport associated with underground compressed air energy storage (CAES) in lined rock caverns. Specifically, we explored the concept of using concrete lined caverns at a relatively shallow depth for which constructing and operation costs may be reduced if air tightness and stability can be assured. Our analysis showed that the key parameter to assure long-term air tightness in such a system was the permeability of both the concrete lining and the surrounding rock. The analysis also indicated that a concrete lining with a permeability of less than 1×10−18m2 would result in an acceptable air leakage rate of less than 1%, with the operation pressure range between 5 and 8MPa at a depth of 100m. It was further noted that capillary retention properties and the initial liquid saturation of the lining were very important. Indeed, air leakage could be effectively prevented when the air-entry pressure of the concrete lining is higher than the operation air pressure and when the lining is kept at relatively high moisture content. Our subsequent energy-balance analysis demonstrated that the energy loss for a daily compression and decompression cycle is governed by the air-pressure loss, as well as heat loss by conduction to the concrete liner and surrounding rock. For a sufficiently tight system, i.e., for a concrete permeability of less than 1×10−18m2, heat loss by heat conduction tends to become proportionally more important. However, the energy loss by heat conduction can be minimized by keeping the air-injection temperature of compressed air closer to the ambient temperature of the underground storage cavern. In such a case, almost all the heat loss during compression is gained back during subsequent decompression. Finally, our numerical simulation Study showed that CAES in shallow rock caverns is feasible from a leakage and energy efficiency viewpoint. Our numerical approach and energy analysis will next be applied in designing and evaluating the performance of a planned full-scale pilot test of the proposed underground CAES concept.

  • Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A Modeling Study of air tightness and energy balance
    Applied Energy, 2012
    Co-Authors: Hyung-mok Kim, Jonny Rutqvist, Choon Sunwoo, Dong-woo Ryu, Byung-hee Choi, Wonkyong Song
    Abstract:

    Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A Modeling Study of air tightness and energy balance Hyung-Mok Kim 1 , Jonny Rutqvist 2 , Dong-Woo Ryu 1 , Choon Sunwoo 1 , Won-Kyong Song 1 Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, 305-350 Korea Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720 U.S.A. September 28, 2011

Henry J. Curran - One of the best experts on this subject based on the ideXlab platform.

  • An updated experimental and kinetic Modeling Study of n-heptane oxidation
    Combustion and Flame, 2016
    Co-Authors: Kuiwen Zhang, Anne Rodriguez, Christine B'chir, Colin Banyon, John Bugler, Henry J. Curran, Olivier Herbinet, Frédérique Battin-leclerc, Karl Alexander Heufer
    Abstract:

    This work presents an updated experimental and kinetic Modeling Study of n-heptane oxidation. In the experiments, ignition delay times of stoichiometric n-heptane/air mixtures have been measured in two different high-pressure shock tubes in the temperature range of 726–1412 K and at elevated pressures (15, 20 and 38 bar). Meanwhile, concentration versus time profiles of species have been measured in a jet-stirred reactor at atmospheric pressure, in the temperature range of 500–1100 K at φ = 0.25, 2.0 and 4.0. These experimental results are consistent with those from the literature at similar conditions and extend the current data base describing n-heptane oxidation. Based on our experimental observations and previous Modeling work, a detailed kinetic model has been developed to describe n-heptane oxidation. This kinetic model has adopted reaction rate rules consistent with those recently developed for the pentane isomers and for n-hexane. The model has been validated against data sets from both the current work and the literature using ignition delay times, speciation profiles measured in a jet-stirred reactor and laminar flame speeds over a wide range of conditions. Good agreement is observed between the model predictions and the experimental data. The model has also been compared with several recently published kinetic models of n-heptane and shows an overall better performance. This model may contribute to the development of kinetic mechanisms of other fuels, as n-heptane is a widely used primary reference fuel. Since the sub-mechanisms of n-pentane, n-hexane and n-heptane have adopted consistent reaction rate rules, the model is more likely to accurately simulate the oxidation of mixtures of these fuels. In addition, the successful implementation of these rate rules have indicated the possibility of their application for the development of mechanisms for larger hydrocarbon fuels, which are of great significance for practical combustion devices.

  • Detailed Kinetic Modeling Study of n-Pentanol Oxidation
    Energy & Fuels, 2012
    Co-Authors: Karl Alexander Heufer, Henry J. Curran, S. Mani Sarathy, Charles K Westbrook, Alexander C. Davis, William J Pitz
    Abstract:

    To help overcome the world’s dependence upon fossil fuels, suitable biofuels are promising alternatives that can be used in the transportation sector. Recent research on internal combustion engines shows that short alcoholic fuels (e.g., ethanol or n-butanol) have reduced pollutant emissions and increased knock resistance compared to fossil fuels. Although higher molecular weight alcohols (e.g., n-pentanol and n-hexanol) exhibit higher reactivity that lowers their knock resistance, they are suitable for diesel engines or advanced engine concepts, such as homogeneous charge compression ignition (HCCI), where higher reactivity at lower temperatures is necessary for engine operation. The present Study presents a detailed kinetic model for n-pentanol based on Modeling rules previously presented for n-butanol. This approach was initially validated using quantum chemistry calculations to verify the most stable n-pentanol conformation and to obtain C–H and C–C bond dissociation energies. The proposed model has b...

  • a comprehensive Modeling Study of iso octane oxidation
    Combustion and Flame, 2002
    Co-Authors: Henry J. Curran, P. Gaffuri, William J Pitz, Charles K Westbrook
    Abstract:

    A detailed chemical kinetic mechanism has been developed and used to Study the oxidation of iso-octane in a jet-stirred reactor, flow reactors, shock tubes and in a motored engine. Over the series of experiments investigated, the initial pressure ranged from 1 to 45 atm, the temperature from 550 K to 1700 K, the equivalence ratio from 0.3 to 1.5, with nitrogen-argon dilution from 70% to 99%. This range of physical conditions, together with the measurements of ignition delay time and concentrations, provide a broad-ranging test of the chemical kinetic mechanism. This mechanism was based on our previous Modeling of alkane combustion and, in particular, on our Study of the oxidation of n-heptane. Experimental results of ignition behind reflected shock waves were used to develop and validate the predictive capability of the reaction mechanism at both low and high temperatures. Moreover, species’ concentrations from flow reactors and a jet-stirred reactor were used to help complement and refine the low and intermediate temperature portions of the reaction mechanism, leading to good predictions of intermediate products in most cases. In addition, a sensitivity analysis was performed for each of the combustion environments in an attempt to identify the most important reactions under the relevant conditions of Study. © 2002 by The Combustion Institute

  • A comprehensive Modeling Study of n-heptane oxidation
    Combustion and Flame, 1998
    Co-Authors: Henry J. Curran, P. Gaffuri, William J Pitz, Charles K Westbrook
    Abstract:

    A detailed chemical kinetic mechanism has been developed and used to Study the oxidation of n-heptane in flow reactors, shock tubes, and rapid compression machines. Over the series of experiments numerically investigated, the initial pressure ranged from 1-42 atm, the temperature from 550-1700 K, the equivalence ratio from 0.3-1.5, and nitrogen-argon dilution from 70-99%. The combination of ignition delay time and species composition data provide for a stringent test of the chemical kinetic mechanism. The reactions are classed into various types, and the reaction rate constants are given together with an explanation of how the rate constants were obtained. Experimental results from the literature of ignition behind reflected shock waves and in a rapid compression machine were used to develop and validate the reaction mechanism at both low and high temperatures. Additionally, species composition data from a variable pressure flow reactor and a jet- stirred reactor were used to help complement and refine the low-temperature portions of the reaction mechanism. A sensitivity analysis was performed for each of the combustion environments. This analysis showed that the low- temperature chemistry is very sensitive to the formation of stable olefin species from hydroperoxy-alkyl radicals and to the chain-branching steps involving ketohydroperoxide molecules.

Choon Sunwoo - One of the best experts on this subject based on the ideXlab platform.

  • exploring the concept of compressed air energy storage caes in lined rock caverns at shallow depth a Modeling Study of air tightness and energy balance
    Applied Energy, 2012
    Co-Authors: Jonny Rutqvist, Choon Sunwoo, Wonkyong Song
    Abstract:

    This paper presents a numerical Modeling Study of coupled thermodynamic, multiphase fluid flow and heat transport associated with underground compressed air energy storage (CAES) in lined rock caverns. Specifically, we explored the concept of using concrete lined caverns at a relatively shallow depth for which constructing and operation costs may be reduced if air tightness and stability can be assured. Our analysis showed that the key parameter to assure long-term air tightness in such a system was the permeability of both the concrete lining and the surrounding rock. The analysis also indicated that a concrete lining with a permeability of less than 1×10−18m2 would result in an acceptable air leakage rate of less than 1%, with the operation pressure range between 5 and 8MPa at a depth of 100m. It was further noted that capillary retention properties and the initial liquid saturation of the lining were very important. Indeed, air leakage could be effectively prevented when the air-entry pressure of the concrete lining is higher than the operation air pressure and when the lining is kept at relatively high moisture content. Our subsequent energy-balance analysis demonstrated that the energy loss for a daily compression and decompression cycle is governed by the air-pressure loss, as well as heat loss by conduction to the concrete liner and surrounding rock. For a sufficiently tight system, i.e., for a concrete permeability of less than 1×10−18m2, heat loss by heat conduction tends to become proportionally more important. However, the energy loss by heat conduction can be minimized by keeping the air-injection temperature of compressed air closer to the ambient temperature of the underground storage cavern. In such a case, almost all the heat loss during compression is gained back during subsequent decompression. Finally, our numerical simulation Study showed that CAES in shallow rock caverns is feasible from a leakage and energy efficiency viewpoint. Our numerical approach and energy analysis will next be applied in designing and evaluating the performance of a planned full-scale pilot test of the proposed underground CAES concept.

  • Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A Modeling Study of air tightness and energy balance
    Applied Energy, 2012
    Co-Authors: Hyung-mok Kim, Jonny Rutqvist, Choon Sunwoo, Dong-woo Ryu, Byung-hee Choi, Wonkyong Song
    Abstract:

    Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A Modeling Study of air tightness and energy balance Hyung-Mok Kim 1 , Jonny Rutqvist 2 , Dong-Woo Ryu 1 , Choon Sunwoo 1 , Won-Kyong Song 1 Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, 305-350 Korea Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720 U.S.A. September 28, 2011