The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform
Hang Guo - One of the best experts on this subject based on the ideXlab platform.
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study on the characteristics of expander power output used for offsetting Pumping Work consumption in organic rankine cycles
Energies, 2014Co-Authors: Biao Lei, Lei Zhao, Jingfu Wang, Hang GuoAbstract:The circulation pump in an organic Rankine cycle (ORC) increases the pressure of the liquid Working fluid from low condensing pressure to high evaporating pressure, and the expander utilizes the pressure difference to generate Work. A portion of the expander output power is used to offset the consumed Pumping Work, and the rest of the expander power is exactly the net Work produced by the ORC system. Because of the relatively great theoretical Pumping Work and very low efficiency of the circulation pump reported in previous papers, the characteristics of the expander power used for offsetting the Pumping Work need serious consideration. In particular, the present Work examines those characteristics. It is found that the characteristics of the expander power used for offsetting the Pumping Work are satisfactory only under the condition that the Working fluid absorbs sufficient heat in the evaporator and its specific volume at the evaporator outlet is larger than or equal to a threshold value.
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Study on the Characteristics of Expander Power Output Used for Offsetting Pumping Work Consumption in
2014Co-Authors: Lei Biao, Lei Zhao, Jingfu Wang, Hang GuoAbstract:Abstract: The circulation pump in an organic Rankine cycle (ORC) increases the pressure of the liquid Working fluid from low condensing pressure to high evaporating pressure, and the expander utilizes the pressure difference to generate Work. A portion of the expander output power is used to offset the consumed Pumping Work, and the rest of the expander power is exactly the net Work produced by the ORC system. Because of the relatively great theoretical Pumping Work and very low efficiency of the circulation pump reported in previous papers, the characteristics of the expander power used for offsetting the Pumping Work need serious consideration. In particular, the present Work examines those characteristics. It is found that the characteristics of the expander power used for offsetting the Pumping Work are satisfactory only under the condition that the Working fluid absorbs sufficient heat in the evaporator and its specific volume at the evaporator outlet is larger than or equal to a threshold value.
Christos Tzivanidis - One of the best experts on this subject based on the ideXlab platform.
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multiple cylindrical inserts for parabolic trough solar collector
Applied Thermal Engineering, 2018Co-Authors: Evangelos Bellos, Ilias Daniil, Christos TzivanidisAbstract:Abstract The use of insert flow is a promising technique for increasing the performance of parabolic trough solar collectors. The objective of this Work is to investigate the use of multiple cylindrical longitudinal inserts in the parabolic trough solar collector LS-2 module. Totally 15 cases are investigated with a computational dynamic model developed in SolidWorks Flow Simulation. More specifically, the reference empty tube, one case with a single insert, eight cases with two inserts flow, three cases with three insert flow and two cases with four insert flow. It is found that the use of more inserts leads to higher thermal, exergy and overall efficiency performance of the collector. Moreover, it is found that the exact location of the inserts plays a significant role in the results. The Pumping Work is found to be generally low in all the cases, the fact that proves that the increase in the pressure drop is not so important in the total system performance. The global maximum efficiency is found for the case with the four inserts and in this case, the thermal efficiency is enhanced 0.656%, the thermal losses are reduced about 5.63% and the heat transfer coefficient is increased 26.88%. The results of this Work can be used for the proper design of multiple inserts design in solar systems.
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investigation of a star flow insert in a parabolic trough solar collector
Applied Energy, 2018Co-Authors: Evangelos Bellos, Christos TzivanidisAbstract:Abstract The use of flow inserts is a common passive technique for enhancing the thermal performance of parabolic trough solar collectors. The objective of this Work is to investigate a novel insert with a star shape. The shape of this insert is optimized by examining different combinations of its geometric characteristics. Totally 16 different cases are studied with the fin length to be varied from 15 mm to 30 mm and the fin thickness from 2 mm to 5 mm. The evaluation criteria of the examined cases are the thermal efficiency, the exergy efficiency and the overall efficiency of the solar collector. The exergy efficiency and the overall efficiency are suitable criteria for evaluation the Nusselt number increase with the simultaneous friction factor increase. The collector is examined for inlet temperatures between 400 K and 650 K with a volumetric flow rate equal to 150 L/min. According to the final results, the thermal efficiency, the exergy efficiency and the overall efficiency are increased for all the examined flow inserts. The thermal efficiency enhancement is higher with the inlet temperature increase and it can reach up to 1%. Moreover, it is found that greater dimensions of the insert lead to higher performance enhancements. The pressure drop is found to increases many times with the use of inserts but the Pumping Work value is extremely low in all the cases. The analysis is conducted with SolidWorks Simulation Studio with a validated model.
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optical and thermal analysis of a linear fresnel reflector operating with thermal oil molten salt and liquid sodium
Applied Thermal Engineering, 2018Co-Authors: Evangelos Bellos, Christos Tzivanidis, Angelos PapadopoulosAbstract:Abstract Linear Fresnel collectors are promising technologies for the exploitation of solar irradiation in medium and high temperatures. In this study, a linear Fresnel collector with flat primary mirrors and a parabolic shape secondary reflector is investigated. The location of the secondary reflector is simply optimized and then the collector is investigated under different incident angles (transversal and longitudinal). The next step is the thermal analysis of the collector with three different Working fluids: thermal oil, molten salt and liquid sodium. The analysis is performed for temperatures up to 900 K with liquid sodium in order to examine the collector up to its stagnation temperature. Both the optical and thermal analysis are conducted with SolidWorks Flow Simulation. According to the final results, the exergy performance of the collector is maximized at 700 K and it is 30.20% with liquid sodium and 30.05% with molten salt. Generally, liquid sodium was found to be the best candidate according to performance criteria, with molten salt and thermal oil to follow. The high heat transfer coefficient is the reason for the superior performance of the liquid sodium. Moreover, the Pumping Work is maximized for operation with molten salt.
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multi criteria evaluation of a nanofluid based linear fresnel solar collector
Solar Energy, 2018Co-Authors: Evangelos Bellos, Christos TzivanidisAbstract:Abstract Solar linear Fresnel reflector (LFR) is a promising concentrating technology, which presents important advantages such as the low investment cost, the reduced wind loads and the relatively low land utilization factor. The objective of this Work is to investigate an innovative way for enhancing the thermal performance of LFR, especially at high temperatures. The utilization of nanofluid as heat transfer fluid is the investigated thermal enhancement method and more specifically the use of CuO nanoparticle dispersed on Syltherm 800 (6% volumetric concentration). The examined collector has total net aperture equal to 154 m2 and concentration ratio of 58.36. The primary reflectors are curved mirrors, the secondary reflectors have compound parabolic shape and the receiver is an evacuated tube. The operation with nanofluid is compared to the operation with pure thermal oil for various inlet temperatures from 350 K up to 650 K and flow rate equal to 200 L/min. According to the final results, the maximum thermal efficiency enhancement with the nanofluid is close to 0.8%, while the Pumping Work demand is increased up to 50% with the nanofluid. Various criteria like the exergy efficiency, overall efficiency and entropy generation are applied in order to evaluate the nanofluid utilization properly. Finally, the operation with nanofluid is found to be beneficial, especially in high-temperature levels. The analysis is conducted with SolidWorks Flow Simulation with a validated model.
Aldo Steinfeld - One of the best experts on this subject based on the ideXlab platform.
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design of packed bed thermal energy storage systems for high temperature industrial process heat
Applied Energy, 2015Co-Authors: Giw Zanganeh, Andrea Pedretti, Andreas Haselbacher, Aldo SteinfeldAbstract:A previously validated quasi-one-dimensional transient two-phase heat transfer model is used to assess the effect of operational and design parameters on the performance of thermocline thermal energy storage (TES) based on a packed bed of rocks and high-temperature air from process heat as heat transfer fluid. The performance indicators are thermal losses, Pumping Work, discharge outflow temperature, and overall storage efficiency. A 7.2GWhth TES unit is used as a baseline design. It is found that initial charging of the TES prior to cyclic operation significantly improves its performance at the expense of additional storage material. The temperature drop during the discharge phase is reduced and the efficiency is increased by decreasing the tank diameter-to-height ratio and the rock diameter at the expense of increased pressure drop and Pumping Work. Increasing the cone angle results in reduced storage size, but increases the temperature drop during discharging. It is shown that thin insulation layers are sufficient to ensure low thermal losses. For all investigated cases, the overall efficiency of the storage stays above 95%.
Evangelos Bellos - One of the best experts on this subject based on the ideXlab platform.
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multiple cylindrical inserts for parabolic trough solar collector
Applied Thermal Engineering, 2018Co-Authors: Evangelos Bellos, Ilias Daniil, Christos TzivanidisAbstract:Abstract The use of insert flow is a promising technique for increasing the performance of parabolic trough solar collectors. The objective of this Work is to investigate the use of multiple cylindrical longitudinal inserts in the parabolic trough solar collector LS-2 module. Totally 15 cases are investigated with a computational dynamic model developed in SolidWorks Flow Simulation. More specifically, the reference empty tube, one case with a single insert, eight cases with two inserts flow, three cases with three insert flow and two cases with four insert flow. It is found that the use of more inserts leads to higher thermal, exergy and overall efficiency performance of the collector. Moreover, it is found that the exact location of the inserts plays a significant role in the results. The Pumping Work is found to be generally low in all the cases, the fact that proves that the increase in the pressure drop is not so important in the total system performance. The global maximum efficiency is found for the case with the four inserts and in this case, the thermal efficiency is enhanced 0.656%, the thermal losses are reduced about 5.63% and the heat transfer coefficient is increased 26.88%. The results of this Work can be used for the proper design of multiple inserts design in solar systems.
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investigation of a star flow insert in a parabolic trough solar collector
Applied Energy, 2018Co-Authors: Evangelos Bellos, Christos TzivanidisAbstract:Abstract The use of flow inserts is a common passive technique for enhancing the thermal performance of parabolic trough solar collectors. The objective of this Work is to investigate a novel insert with a star shape. The shape of this insert is optimized by examining different combinations of its geometric characteristics. Totally 16 different cases are studied with the fin length to be varied from 15 mm to 30 mm and the fin thickness from 2 mm to 5 mm. The evaluation criteria of the examined cases are the thermal efficiency, the exergy efficiency and the overall efficiency of the solar collector. The exergy efficiency and the overall efficiency are suitable criteria for evaluation the Nusselt number increase with the simultaneous friction factor increase. The collector is examined for inlet temperatures between 400 K and 650 K with a volumetric flow rate equal to 150 L/min. According to the final results, the thermal efficiency, the exergy efficiency and the overall efficiency are increased for all the examined flow inserts. The thermal efficiency enhancement is higher with the inlet temperature increase and it can reach up to 1%. Moreover, it is found that greater dimensions of the insert lead to higher performance enhancements. The pressure drop is found to increases many times with the use of inserts but the Pumping Work value is extremely low in all the cases. The analysis is conducted with SolidWorks Simulation Studio with a validated model.
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optical and thermal analysis of a linear fresnel reflector operating with thermal oil molten salt and liquid sodium
Applied Thermal Engineering, 2018Co-Authors: Evangelos Bellos, Christos Tzivanidis, Angelos PapadopoulosAbstract:Abstract Linear Fresnel collectors are promising technologies for the exploitation of solar irradiation in medium and high temperatures. In this study, a linear Fresnel collector with flat primary mirrors and a parabolic shape secondary reflector is investigated. The location of the secondary reflector is simply optimized and then the collector is investigated under different incident angles (transversal and longitudinal). The next step is the thermal analysis of the collector with three different Working fluids: thermal oil, molten salt and liquid sodium. The analysis is performed for temperatures up to 900 K with liquid sodium in order to examine the collector up to its stagnation temperature. Both the optical and thermal analysis are conducted with SolidWorks Flow Simulation. According to the final results, the exergy performance of the collector is maximized at 700 K and it is 30.20% with liquid sodium and 30.05% with molten salt. Generally, liquid sodium was found to be the best candidate according to performance criteria, with molten salt and thermal oil to follow. The high heat transfer coefficient is the reason for the superior performance of the liquid sodium. Moreover, the Pumping Work is maximized for operation with molten salt.
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multi criteria evaluation of a nanofluid based linear fresnel solar collector
Solar Energy, 2018Co-Authors: Evangelos Bellos, Christos TzivanidisAbstract:Abstract Solar linear Fresnel reflector (LFR) is a promising concentrating technology, which presents important advantages such as the low investment cost, the reduced wind loads and the relatively low land utilization factor. The objective of this Work is to investigate an innovative way for enhancing the thermal performance of LFR, especially at high temperatures. The utilization of nanofluid as heat transfer fluid is the investigated thermal enhancement method and more specifically the use of CuO nanoparticle dispersed on Syltherm 800 (6% volumetric concentration). The examined collector has total net aperture equal to 154 m2 and concentration ratio of 58.36. The primary reflectors are curved mirrors, the secondary reflectors have compound parabolic shape and the receiver is an evacuated tube. The operation with nanofluid is compared to the operation with pure thermal oil for various inlet temperatures from 350 K up to 650 K and flow rate equal to 200 L/min. According to the final results, the maximum thermal efficiency enhancement with the nanofluid is close to 0.8%, while the Pumping Work demand is increased up to 50% with the nanofluid. Various criteria like the exergy efficiency, overall efficiency and entropy generation are applied in order to evaluate the nanofluid utilization properly. Finally, the operation with nanofluid is found to be beneficial, especially in high-temperature levels. The analysis is conducted with SolidWorks Flow Simulation with a validated model.
Biao Lei - One of the best experts on this subject based on the ideXlab platform.
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study on the characteristics of expander power output used for offsetting Pumping Work consumption in organic rankine cycles
Energies, 2014Co-Authors: Biao Lei, Lei Zhao, Jingfu Wang, Hang GuoAbstract:The circulation pump in an organic Rankine cycle (ORC) increases the pressure of the liquid Working fluid from low condensing pressure to high evaporating pressure, and the expander utilizes the pressure difference to generate Work. A portion of the expander output power is used to offset the consumed Pumping Work, and the rest of the expander power is exactly the net Work produced by the ORC system. Because of the relatively great theoretical Pumping Work and very low efficiency of the circulation pump reported in previous papers, the characteristics of the expander power used for offsetting the Pumping Work need serious consideration. In particular, the present Work examines those characteristics. It is found that the characteristics of the expander power used for offsetting the Pumping Work are satisfactory only under the condition that the Working fluid absorbs sufficient heat in the evaporator and its specific volume at the evaporator outlet is larger than or equal to a threshold value.
