| 1. |
- Ding, J., et al.
(författare)
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Theoretical prediction of the local structures and transport properties of binary alkali chloride salts for concentrating solar power
- 2017
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Ingår i: Nano Energy. - : Elsevier. - 2211-2855 .- 2211-3282. ; 39, s. 380-389
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Tidskriftsartikel (refereegranskat)abstract
- Comprehensive molecular simulations have been carried out to compute local structures and transport properties of different components of binary NaCl-KCl over a wide operating temperature range. The partial radial distribution functions, coordination number curves and angular distribution functions were calculated to analyze the influence of temperature and component on local structures of molten Alkali Chlorides. Transport properties were calculated by using reverse non-equilibrium molecular dynamics (RNEMD) simulations including densities, shear viscosity and thermal conductivity. The results show that ion clusters are considered to be formed and the distance of ion clusters become larger with increasing temperature which has great influence on macro-properties. The calculated properties have a good agreement with the experimental data, and similar method could be used to computationally calculate the properties of various molten salts and their mixtures.
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| 2. |
- Wang, W., et al.
(författare)
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Carbon dioxide adsorption thermodynamics and mechanisms on MCM-41 supported polyethylenimine prepared by wet impregnation method
- 2015
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 142, s. 221-228
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Tidskriftsartikel (refereegranskat)abstract
- Amine-functionalized sorbents prepared by wet impregnation method shows great promises for CO2 capture from real flue gas in power plants. The objective of this work is to understand CO2 adsorption thermodynamics and mechanisms at varied polyethylenimine (PEI) loadings on mesoporous MCM-41 by wet impregnation method using a computational approach for the first time. The structures of PEI/MCM-41 sorbents were optimized using molecular dynamics (MD), and the CO2 adsorption thermodynamics at varied PEI loadings was simulated using Grand Canonical Monte Carlo (GCMC) method. Results showed a good agreement between experiments and simulation. On the surface of the MCM-41, there are high CO2-philic sites for CO2 adsorption, which were firstly covered by PEI molecular. The functionalization groups increased the interactions of the CO2 with more PEI molecular deployed on the surface of the MCM-41, then to the center of the pore. The adsorption performance of the composite sorbents depended on the adsorption cites and the space for CO2 diffusion. The CO2 adsorption thermodynamics and mechanisms at varied PEI loadings shed lights on tuning CO2 capture performance with amine-functionalized sorbents for power plant greenhouse gas control.
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| 3. |
- Pan, G., et al.
(författare)
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Thermal performance of a binary carbonate molten eutectic salt for high-temperature energy storage applications
- 2020
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 262
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Tidskriftsartikel (refereegranskat)abstract
- Molten carbonate eutectic salts are promising thermal storage and heat transfer fluid materials in solar thermal power plant with the feature of large specific heat capacity, wide operating temperature range and little corrosive. The high-temperature properties of molten carbonates should be determined accurately over the entire operating temperature for energy system design. In this paper, molecular dynamic simulation is used to study temperature and component dependence of microstructures and thermophysical properties of the binary carbonate molten salt. Negative linear temperature dependence of densities and thermal conductivities of binary mixtures of different components is confirmed with respect to the distances of ion clusters. Besides, positive linear temperature dependence of self-diffusion coefficient is also obtained. When temperature is constant, densities and thermal conductivities of binary mixtures are linearly related with components. Self-diffusion coefficients of CO32− firstly increase and then decrease with increasing mole fraction of Na2CO3. The temperature-thermophysical properties-composition correlation formulas are obtained, and the database of thermophysical properties of molten carbonate salts over the entire operating temperature is complemented, which will provide the essential data for heat transfer and storage system design, operation, and optimization in CSP.
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| 4. |
- Petropoulos, Fotios, et al.
(författare)
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Operational Research : methods and applications
- 2024
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Ingår i: Journal of the Operational Research Society. - : Taylor & Francis Group. - 0160-5682 .- 1476-9360. ; 75:3, s. 423-617
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Forskningsöversikt (refereegranskat)abstract
- Throughout its history, Operational Research has evolved to include methods, models and algorithms that have been applied to a wide range of contexts. This encyclopedic article consists of two main sections: methods and applications. The first summarises the up-to-date knowledge and provides an overview of the state-of-the-art methods and key developments in the various subdomains of the field. The second offers a wide-ranging list of areas where Operational Research has been applied. The article is meant to be read in a nonlinear fashion and used as a point of reference by a diverse pool of readers: academics, researchers, students, and practitioners. The entries within the methods and applications sections are presented in alphabetical order. The authors dedicate this paper to the 2023 Turkey/Syria earthquake victims. We sincerely hope that advances in OR will play a role towards minimising the pain and suffering caused by this and future catastrophes.
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| 5. |
- Rong, Z., et al.
(författare)
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Experimental and theoretical investigation of an innovative composite nanofluid for solar energy photothermal conversion and storage
- 2022
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Ingår i: Journal of Energy Storage. - : Elsevier Ltd. - 2352-152X .- 2352-1538. ; 52
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Tidskriftsartikel (refereegranskat)abstract
- Molten salts play a key role in the heat transfer and thermal energy storage processes of concentrated solar power plants. A novel composite material was prepared in this work by adding micron-sized magnesium particles into Li2CO3-Na2CO3-K2CO3 molten salt, the heat transfer and thermal energy storage properties of the composites were studied experimentally. A stable composite nanofluid can be obtained, and a thermal conductivity of 0.728 W/(m·K) at 973 K with an enhancement of 31% is achieved for the Mg/molten carbonate nanofluid. And the strengthening mechanism of thermal conductivity was revealed by using ab-initio molecular dynamics method. It is found that the main bonding interactions exist between Mg and O atoms at the surface of Mg particles. A compressed ion layer with a more compact and ordered ionic structure is formed around Mg particles, and the Brownian motions of Mg particles lead to the micro-convections of carbonate ions around them. These factors are helpful to the enhancement of thermal conduction with the improved probability and frequency of ion collisions. This work can provide a guidance for further studies and applications on metal/molten salt composites with enhanced heat transfer and thermal energy storage capacity.
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| 6. |
- Wang, W., et al.
(författare)
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Experimental study on the direct/indirect contact energy storage container in mobilized thermal energy system (M-TES)
- 2014
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 119, s. 181-189
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Tidskriftsartikel (refereegranskat)abstract
- A mobilized thermal energy storage (TES) system has been proposed to recover and use industrial waste or excess heat for distributed users. In this paper, lab-scale test facilities have been built to understand the mechanisms of heat charging and discharging processes. The facilities consist of a direct/indirect-contact thermal energy storage container, heat transfer oil (HTO)/water tanks, an electrical boiler, HTO/water pumps and a plate heat exchanger. The organic phase change material (PCM), erythritol, which is sugar alcohol, was chosen as the working material due to its large heat density (330. kJ/kg) and suitable melting point (118. °C) for industrial low-temperature heat recovery, as well as non toxic and corrosive. Although differential scanning calorimetry tests have shown that a large temperature range exists during the phase change of erythritol, it did not affect the heat discharging during the tests of system performance. Heat charging/discharging results show that for the direct-contact storage container, heat discharging process is much faster than charging process. At the initial stage of heat charging, heat transfer oil is blocked to enter the container, resulting in a slow charging rate. Meanwhile, the PCM attached on the container wall on the bottom always melts last. It has been found that increasing the flow rate of HTO can effectively enhance the charging/discharging processes. For the indirect-contact storage container, heat charging and discharging take almost the same time; and the flow rate of HTO does not show an obvious effect on the charging and discharging processes due to the weak thermal conductivity of the solid phase change material. Comparatively, using the direct-contact storage container may achieve shorter charging/discharging processes than using the indirect-contact storage container.
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| 7. |
- Wang, W., et al.
(författare)
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Numerical simulation study on discharging process of the direct-contact phase change energy storage system
- 2015
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 150, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- The mobilized thermal energy storage system (M-TES) has been demonstrated as a promising technology to supply heat using waste heat in industries to distributed users, where heat discharging determines whether M-TES system can satisfy the required heating rate. The objective of this work is to investigate the solidification mechanism of phase change materials (PCM) for heat discharging in a direct-contact thermal energy storage (TES) container for M-TES. A 2-dimensional (2D) numerical simulation model of the TES tank is developed in ANSYS FLUENT, and validated with the experimental measurement. Effects of flow rate and inlet temperature of heat transfer oil (HTO) were studied. Results show that (a) the discharging process includes the formation of solidified PCM followed by the sinking of solidified PCM; (b) the discharging time of M-TES can be reduced by increasing the flow rate of heat transfer oil. When the flow rate is increased from 0.46m3/h to 0.92m3/h, the solidified PCM is increased from 25vol.% to 90vol.% within 30min; (c) the discharging time can be reduced by decreasing the inlet temperature of HTO. While the inlet temperature is reduced from 50°C to 30°C, the solidified PCM is increased from 60vol.% to 90vol.% within 30min. This work provides engineering insights for the rational design of discharging process for M-TES system.
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| 8. |
- Ye, Y., et al.
(författare)
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Enhanced hydrogen storage of a LaNi5 based reactor by using phase change materials
- 2021
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Ingår i: Renewable energy. - : Elsevier Ltd. - 0960-1481 .- 1879-0682. ; 180, s. 734-743
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Tidskriftsartikel (refereegranskat)abstract
- Safe and efficient hydrogen storage technology is of great significance for large-scale hydrogen energy utilization. Using metal hydride (MH) materials such as LaNi5 for hydrogen storage is an effective way. In application, the heat and mass transfer characteristics in the reactor are one of the important factors and key problems affecting the hydrogen storage performance of MH. This paper proposes a novel hydrogen storage reactor installing a concentric finned tube heat exchanger and using phase change materials (PCM) by surrounding the reactor to improve heat transfer and hydrogen storage performance. A numerical model is built to describe transportation and reaction of two reactors with or without PCM. By comparison, the reactor surrounded by PCM has faster heat discharge and hydrogen absorption rate, and the absorption time is shortened by 50%. For the reactor with PCM, the optimal amount of PCM and the inlet velocity of heat transfer fluid (HTF) are investigated. The results show that the effective thermal conductivity of MH play a key role to improve heat transfer and reaction rate rather than that of PCM. Furthermore, increasing hydrogen supply pressure can effectively accelerate heat discharge and hydrogen absorption rate owning to larger temperature differences and improved reaction kinetics. © 2021
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| 9. |
- Wang, W., et al.
(författare)
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A combined experimental and simulation study on charging process of Erythritol-HTO direct-blending based energy storage system
- 2014
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Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 83, s. 306-313
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Tidskriftsartikel (refereegranskat)abstract
- Thermal energy storage (TES) system is essential to recover and use intermittent heat, such as industrial waste/excess heat or solar energy. In this paper, a direct-contact erythritol/heat transfer oil (HTO) energy storage system has been studied experimentally, consisting of a thermal energy storage unit, electrical heaters, heat exchanger and water cycle. In the system, erythritol has been used as an energy storage media (melting point = 118 °C, heat enthalpy = 330 kJ/kg), and HTO is used as a heat transfer material. Moreover, simulation has been conducted to understand heat transfer enhancement mechanisms of direct-contact heat storage. It is noticed that, at the beginning of heat storage, heat transfer oil has a small flow rate due to the block of solid part. PCM in the middle area of the storage unit melts faster than other parts due to the greater heat transfer on the liquid-solid interface of the both sides, and erythritol attached on the storage unit wall melts slowly since small heat conductivity plays a key role for heat transfer. It is also found that increasing the flow rate of HTO can significantly decrease the melting time by increasing fluid turbulent degree.
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| 10. |
- Wang, Weilong, 1978-, et al.
(författare)
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Preparation and performance of form-stable polyethylene glycol/silicon dioxide composites as solid–liquid phase change materials
- 2009
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 86:2, s. 170-174
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Tidskriftsartikel (refereegranskat)abstract
- This work mainly involved the preparation and characterization of form-stable polyethylene glycol (PEG)/silicon dioxide (SiO2) composite as a novel solid–liquid phase change material (PCM). In this study, the polyethylene glycol/silicon dioxide composites as form-stable, solid–liquid phase change material (PCM) was prepared. In this new material, the polyethylene glycol acts as the latent heat storage material and silicon dioxide serves as the supporting material, which provides structural strength and prevents the leakage of the melted polyethylene glycol. Results indicated that the composite remained solid when the weight percentage of silicon dioxide was higher than 15%. Moreover, the polyethylene glycol was observed to disperse into the network of the solid silicon dioxide by investigation of the structure of the composite PCMs using a scanning electronic microscope (SEM). The properties of the porous materials and phase change materials were characterized using Fourier transformation infrared spectroscope (FTIR). The transition process was observed using polarizing optical microscope (POM) and dynamic thermo mechanic analysis (DMA). The melting temperatures and latent heats of the form-stable PEG/SiO2 composite PCMs were determined using differential scanning calorimeter (DSC).
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