| 1. |
- Li, Lifeng, et al.
(författare)
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Hydrodynamics and mass transfer of concentric-tube internal loop airlift reactors : A review
- 2022
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 359
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Forskningsöversikt (refereegranskat)abstract
- The concentric-tube internal loop airlift reactor is a typical reactor configuration which has been adopted for a myriad of chemical and biological processes. The reactor hydrodynamics (including mixing) and the mass transfer between the gas and liquid phases remarkably affect the operational conditions and thus are crucial to the overall reactor performance. Hence, this study aims at providing a thorough description of the basic concepts and a comprehensive review of the relevant reported studies on the hydrodynamics and mass transfer of the concentric-tube internal loop airlift reactors, taking microalgae cultivation as an exemplary application. In particular, the reactor characteristics, geometry, CFD modeling, experimental characterization, and scale up considerations are elucidated. The research gaps for future research and development are also identified.
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| 2. |
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| 3. |
- Li, L., et al.
(författare)
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Optical analysis of a multi-aperture solar central receiver system for high-temperature concentrating solar applications
- 2020
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Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 28:25, s. 37654-37668
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Tidskriftsartikel (refereegranskat)abstract
- A multi-aperture solar central receiver system is optically analyzed for increasing the net power to the receiver in a wide temperature range of 600-1800 K. A model system comprises a tower, a multi-aperture receiver with compound parabolic concentrators, and heliostat sub-fields. Optical modeling is performed using in-house developed Monte-Carlo ray-tracing programs. The heliostat sub-field geometrical configuration, the number of receiver apertures and optical properties of reflective surfaces are varied in the parametric study. Increasing the number of apertures from one to four increases the maximum net receiver power from 116MW to 332MW. The use of more than four apertures results in only limited further gain of the net receiver power but significantly decreases the overall optical efficiency and the solar-to-thermal efficiency. The optimal temperature for the maximized annual solar-to-exergy efficiency is found in the range of 1100-1200 K. This optimal temperature decreases slightly with an increasing number of apertures.
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| 4. |
- Ruan, Tianqi, et al.
(författare)
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A new optimal PV installation angle model in high-latitude cold regions based on historical weather big data
- 2024
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 359
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Tidskriftsartikel (refereegranskat)abstract
- PV technologies are regarded as one of the most promising renewable options for the transition towards Net Zero. Despite the rapid development of PV systems in recent years, achieving the necessary goals requires more than a threefold increase in annual capacity deployment by 2030. However, current PV systems often fall short of optimal performance due to improper installation angles. In high-latitude cold regions, the actual PV generation capacity is frequently overestimated due to the omission of snow conditions. This study introduces a novel model designed for high-latitude regions to predict local optimal PV installation angle that maximizes PV power generation, utilizing historical weather big data, including snowfall and melting effects. A case study is presented within a Swedish context to demonstrate the implementation of these methods. The results highlight the crucial role snow conditions play in determining PV performance, resulting in an average reduction of 14.7% in annual PV power generation. Optimal installation angle could yield approximately a 4.8% improvement compared to common installation angles. The study also explores the application of snow removal agents, which could potentially increase PV generation by 0.1–2.3%. Additionally, the new PV installation angle successfully captures the impact of the local weather changes on PV power generation, potentially serving as a bridge between climate change adaptation and future PV power generation endeavors.
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| 5. |
- Shao, X. -F, et al.
(författare)
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Screening of sugar alcohols and their binary eutectic mixtures as phase change materials for low-to-medium temperature latent heat storage. (Ⅰ) : Non-isothermal melting and crystallization behaviors
- 2018
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 160, s. 1078-1090
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Tidskriftsartikel (refereegranskat)abstract
- Towards latent heat storage in the low-to-medium temperature range (70–250 °C), screening of sugar alcohols and their binary eutectic mixtures as potential phase change materials was carried out by focusing on the non-isothermal melting and crystallization behaviors. A preliminary screening shortened the long list of isomers from common four-carbon to six-carbon sugar alcohols to only six affordable candidates, i.e., xylitol, d-sorbitol, erythritol, d-mannitol, d-dulcitol and inositol (ordered with increasing the melting point). Based on the six pre-screened sugar alcohols, a total of 15 binary eutectic mixtures were prepared to manipulate the melting points for more flexible match with real applications. Non-isothermal tests were then performed on a differential scanning calorimeter at various ramping/cooling rates up to 10 °C/min. In addition to determination of the melting point and latent heat of fusion, a special attention was paid to the crystallization behaviors by undertaking consecutive melting-crystallization cyclic tests. It was found that the two candidates with the lowest melting points (both below 100 °C), i.e., xylitol and d-sorbitol, as well as the nine binary eutectic mixtures containing at least one of them, are unable to crystallize from the melt during cool-down at any cooling rates tested (down to 0.5 °C/min). Four other binary eutectic mixtures, i.e., erythritol (84 mol%) + d-mannitol, erythritol (95 mol%) + d-dulcitol, erythritol (96 mol%) + inositol and d-dulcitol (69 mol%) + inositol, were also shown to be unable to crystallize upon cooling, with the crystallization occurring during the reheating process instead, referred to as cold crystallization. The rest four pure sugar alcohols with relatively high melting points (110–230 °C), i.e., erythritol, d-mannitol, d-dulcitol, inositol, and two mixtures, i.e., d-mannitol (70 mol%) + d-dulcitol and d-mannitol (82 mol%) +inositol, were found to be able to crystallize upon cooling, although they all suffer from severe supercooling (e.g., up to over 100 °C for erythritol). The affordable pure and mixture sugar alcohols were deemed to have desirably high latent heat storage density, especially for those with higher melting points. However, they all face specific issues associated with crystallization, which must be addressed before they can really be utilized in real applications. In addition, it may not worth making eutectic mixtures, although this is deemed to be an effective way of manipulating the melting points of sugar alcohols.
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| 6. |
- Shao, Xue-Feng, et al.
(författare)
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Screening of sugar alcohols and their binary eutectic mixtures as phase change materials for low-to-medium temperature thermal energy storage. (II) : Isothermal melting and crystallization behaviors
- 2019
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 180, s. 572-583
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Tidskriftsartikel (refereegranskat)abstract
- Based on the non-isothermal phase change behaviors of twenty-one pure and mixture sugar alcohols presented in our previous study (Part 1), the isothermal melting and crystallization behaviors were further tested in this supplemental work for five selected pure sugar alcohols (xylitol, erythritol, dmannitol, d-dulcitol and inositol) and their five binary eutectic mixtures to make an advanced screening of these candidates for low-to-medium temperature latent heat storage. The isothermal melting and crystallization behaviors of these ten candidates were tested at a constant degree of superheat (10 degrees C) and various degrees of subcooling up to 210 degrees C. The phase change temperatures, degrees of supercooling and durations of phase change were determined by the recorded temperature-history curves. It was found that the incrystallizable xylitol and its eutectic mixture of xylitol (75 mol%) + erythritol with low melting points under 100 degrees C are also unable to crystallize during isothermal cool-down at any degrees of subcooling (30-90 degrees C) due to the unavailability to nucleation. The rest eight crystallizable candidates all suffer from severe supercooling and are unable to crystallize at low degrees of subcooling (<20 degrees C). They undergo both one-phase supercooling due to poor nucleation performance and two-phase supercooling, which was unable to be obtained previously by non-isothermal cooling, due to slow crystallization kinetics. However, it seems difficult to find a correlation between the observed degrees of supercooling in both the liquid and solid phases and the prescribed degrees of subcooling by only three consecutive isothermal melting and crystallization cycles, as a result of the randomness of nucleation and large size of samples. The duration of crystallization was shown to decrease with increasing the degree of subcooling for both pure and mixture sugar alcohols due to the enhanced driving force for crystallization. The durations of crystallization of the mixture sugar alcohols appear to be longer than those of their pure compounds, due to the lower thermal conductivity and higher dynamic viscosity of the mixtures. Combining the present isothermal and the previous non-isothermal test results, it has been confirmed that the difficulty in crystallization and the severe supercooling are the primary issues for sugar alcohols, which must be addressed before they can be used in real-world latent heat storage systems.
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| 7. |
- Shao, Xue-Feng, et al.
(författare)
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Screening of sugar alcohols and their binary eutectic mixtures as phase change materials for low-to-medium temperature thermal energy storage. (III) : Thermal endurance
- 2020
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Ingår i: Energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-5442 .- 1873-6785. ; 209
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Tidskriftsartikel (refereegranskat)abstract
- The thermal endurance of four pure and three binary eutectic mixture sugar alcohols were examined as a complementary work to the previous screening efforts based on the phase change behaviors towards latent heat storage. It was shown that both the melting point and latent heat of fusion of these sugar alcohols degrade with increasing the heating duration, and that a higher degree of superheat leads to faster degradation. The melting point drift mainly attributes to the shrinking range of hydrogen bonding, whereas the decay of latent heat is likely resulted from the disruption of hydrogen bond networks and incomplete crystallization. Among the various candidates, erythritol exhibits the best thermal endurance. The infrared spectra demonstrated that sugar alcohols can be oxidized to generate aldehydes upon heating when exposed to air. It was also found that the duration for 10% degradation of the latent heat of fusion of inositol can be extended by similar to 9 times when being protected by nitrogen gas. However, although the introduction of nitrogen gas could efficiently improve the thermal endurance, other complex reactions can still occur in inert gas atmosphere at high temperatures, leaving the room for further improving the thermal endurance of sugar alcohols toward real-world applications.
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| 8. |
- Wang, Wujun, 1984-, et al.
(författare)
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The effect of the cooling nozzle arrangement to the thermal performance of a solar impinging receiver
- 2016
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Ingår i: Solar Energy. - : Elsevier. - 0038-092X .- 1471-1257. ; 131, s. 222-234
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the multi-row nozzle arrangement to the thermal performance of an impinging solar receiver is studied, and new governingequations are introduced for modifying the earlier introduced inverse design method. With the help of the modified inverse designmethod and a numerical conjugate heat transfer model, an impinging receiver based on stainless steel 253 MA material has been designedfor the combination of a micro gas turbine and the EuroDish collector system. At a DNI level of 800 W/m2, the average air temperatureat the outlet and the thermal efficiency can reach 1071.5 K and 82.7%. Furthermore, the temperature differences on the absorber can bereduced to 130 K and 149 K for two different DNI levels respectively. This represents a greatly improvement compared with other publishedcavity receiver designs.
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| 9. |
- Aichmayer, Lukas, et al.
(författare)
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Experimental evaluation of a novel solar receiver for a micro gas-turbine based solar dish system in the KTH high-flux solar simulator
- 2018
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Ingår i: Energy. - : Elsevier. - 0360-5442 .- 1873-6785. ; 159, s. 184-195
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Tidskriftsartikel (refereegranskat)abstract
- This work presents the experimental evaluation of a novel pressurized high-temperature solar air receiver for the integration into a micro gas-turbine solar dish system reaching an air outlet temperature of 800°C. The experiments are conducted in the controlled environment of the KTH high-flux solar simulator with well-defined radiative boundary conditions. Special focus is placed on providing detailed information to enable the validation of numerical models. The solar receiver performance is evaluated for a range of operating points and monitored using multiple point measurements. The porous absorber front surface temperature is measured continuously as it is one of the most critical components for the receiver performance and model validation. Additionally, pyrometer line measurements of the absorber and glass window are taken for each operating point. The experiments highlight the feasibility of volumetric solar receivers for micro gas-turbine based solar dish systems and no major hurdles were found. A receiver efficiency of 84.8% was reached for an air outlet temperature of 749°C. When using a lower mass flow, an air outlet temperature of 800°C is achieved with a receiver efficiency of 69.3%. At the same time, all material temperatures remain below permissible limits and no deterioration of the porous absorber is found.
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| 10. |
- Choque Campero, Luis Antonio, et al.
(författare)
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Biomass-based Brayton-Stirling-AGMD polygeneration for small-scale applications in rural areas
- 2024
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 304
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Tidskriftsartikel (refereegranskat)abstract
- The lack of access to electricity and clean water still affects a substantial proportion of rural areas worldwide, in particular the global south. This paper presents a sustainable polygeneration system that can provide electricity, heat, and drinking water by using agricultural residues in remote rural areas. This polygeneration system consists of a solid biomass-fueled Brayton-Stirling combined cycle system, a boiler, and an air-gap membrane distillation unit. Four different system operation modes were designed to examine the most ideal configurations for maximizing power output, overall efficiency, and/or clean water production, considering a polygeneration system designed for a rural village with daily demands of 13450 kWh electricity and 7.5 m3 drinking water. A thermodynamic analysis are employed to analyze and compare these modes, each operating under steady state conditions. The highest electricity output, up to 160 kW, while the highest clean water is up to 0.7 m3/h. The fuel consumption can reach 0.9 kWh/kg of solid fuel and provide up to 0.0045 m3 of freshwater. In addition, nonlinear multi-objective optimization is used to meet the power demands of typical day in rural areas by varying the polygeneration operation modes and turbine inlet temperature.
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