Previous studies in literatures adequately emphasized that inserting fins into phase change material is among the most promising techniques to augment thermal performance of shell-and-tube latent heat thermal energy s...Previous studies in literatures adequately emphasized that inserting fins into phase change material is among the most promising techniques to augment thermal performance of shell-and-tube latent heat thermal energy storage unit.In this study,the novel unequal-length fins are designed from the perspective of synergistic benefits of heat transfer and energy storage performance,and the effects of arrangement,number and total length of unequal-length fins are numerically investigated.Results show that utilization of fins with ascending length,when short and long fins are located in the inlet and outlet of heat transfer fluid respectively,can further promote the heat transfer and energy storage performance compared with equal length fins,and a maximum 6.17%and 0.43%increment of heat transfer performance and stored energy is achieved in full melting time,respectively.The number of unequal-length fins plays a major role in the energy storage,and 18.95%and 0.91%improvement of heat transfer performance and stored energy is realized when equipped with 2 unequal-length fins.A 21.17%improvement of the heat transfer performance is obtained when the total length of unequal-length fins is 18 mm.The present study is helpful to make further efforts to enhance heat transfer and energy storage of shell-and-tube latent heat thermal energy storage unit with unequal-length fins.展开更多
In this study,an innovative thermal energy storage design method was developed by adding the combination of metal foam and fin to phase change materials(PCMs).A numerical model was built and verified based on the comp...In this study,an innovative thermal energy storage design method was developed by adding the combination of metal foam and fin to phase change materials(PCMs).A numerical model was built and verified based on the comparison among the present model prediction,experimental measurements,and numerical results in open lit-erature.To highlight the novel design method,four cases including fin-PCM,foam-PCM,fin-foam-PCM,and PCM unit were compared by means of solidification features.The temperature distribution,solidification front propa-gation,and buoyancy-induced convection in the liquid PCM were accounted for.Numerical results demonstrated that metal foam outperformed fin regarding the improvement on solidification phase change.The combination of foam and fin achieved the best performance,leading to a 90.5%reduction in complete energy release time in comparison with the PCM unit.The proposed design method provided reference potentials for advancing energy storage engineering.However,buoyancy-induced convection in the liquid PCM before solidification was harmful to the formation of solidification front and its movement.A maximal 11.5%prolonging time for the complete solidification was found.展开更多
In view of the high temperature problem faced by mining activities,the coordinated mining of ore deposit and geothermal energy is a solution in line with the concept of green mining.The layered backfill body with finn...In view of the high temperature problem faced by mining activities,the coordinated mining of ore deposit and geothermal energy is a solution in line with the concept of green mining.The layered backfill body with finned double-pipe heat exchanger continuously exchanges heat with the surrounding thermal environment,which plays an effective role in gathering geothermal energy.In this paper,the heat storage process of each layered backfill body under different boundary conditions is simulated by Fluent.The results show the heat storage characteristic of layered backfill body can be significantly improved by adding fins to the double-pipe heat exchanger.On the whole,the heat storage effect of bottom layer backfill body(BLBB)is the best.The total heat storage capacity of top layer backfill body(TLBB),middle layer backfill body(MLBB)and BLBB with the finned double-pipe heat exchanger is 666.3 kJ,662.2 kJ,1003.0 kJ;1639.0 kJ,1760.8 kJ,1911.2 kJ and 1731.1 kJ,1953.3 kJ,1962.8 kJ respectively at 1 h,8 h and 24 h.This study explores the law of heat storage of layered backfill body under different boundary conditions and also expands the idea for layered backfill body to efficiently accumulate geothermal energy.展开更多
In times of increasing global warming,enormous efforts are required to rapidly reduce greenhouse gas(GHG)emissions.Due to the EU’s target of climate neutrality by 2050 and the even more ambitious goal of becoming cli...In times of increasing global warming,enormous efforts are required to rapidly reduce greenhouse gas(GHG)emissions.Due to the EU’s target of climate neutrality by 2050 and the even more ambitious goal of becoming climate-neutral in Germany by 2045,it is necessary to systematically increase energy efficiency and decarbonize the industrial heat sector.The methods of heat integration can be used to exploit existing potentials for waste heat utilization and to integrate renewable technologies for heating and cooling.By using a non-stationary,multiperiod approach,additional energy savings can be achieved by integrating a thermal energy storage(TES)that enables heat transportation over time.This paper presents a simultaneous approach for thermal energy storage integration into multiperiod heat integration problems.The approach can be used to minimize energy demand,costs and CO 2 emissions and is demonstrated in two case studies.In case study 1,it is shown that the presented approach is capable of integrating a TES properly into a simple multiperiod heat integration problem with two periods.In case study 2,a simplified example from a cosmetics manufactory is investigated.The total utility demand can be reduced by up to 44.3%due to TES integration and the energetic optimal storage size can be determined as 125 m 3.The savings are strongly dependent on the constellation of heat flows between the periods,on the temperature levels and on the storage size.Significant reductions of energy demand,costs and CO 2 emissions can be achieved with TES being properly integrated into a suitable operating environment.展开更多
In this study,experimental and numerical investigations were conducted on a tube-fin heat-exchanger latent-heat cold energy storage unit.The fin side of the heat exchanger was filled with water as the energy storage m...In this study,experimental and numerical investigations were conducted on a tube-fin heat-exchanger latent-heat cold energy storage unit.The fin side of the heat exchanger was filled with water as the energy storage medium,and modified expanded graphite(MEG)was employed to improve the thermal characteristics of water.The water contact angle of the expanded graphite decreased from 106.31°to 0°,and the hydrophilicity and the absorption rate of water significantly improved after the modification.Moreover,the experimental analyses of the charge/discharge process showed that the cooling capacity of the system filled with 90 wt.%water/MEG was 80.8%of that of pure water,whereas its cooling time was only 69.7%of that of pure water.The average power increased by 15.9%compared with that of water.The system filled with 90 wt.%water/MEG completed two energy charging and discharging cycles,whereas the system filled with water completed only 1.5 cycles within 15000 s.Furthermore,the effects of the flow rate and inlet temperature of the heat transfer fluid on the charging process were explored.Finally,a numerical model was built and validated to investigate the phase change behavior and the effect of the structure size on the performance of the system.The heat-exchanger fin spacing had no significant effect on the cold energy storage unit,whereas the vertical spacing of the tube pass had the highest effect.It can be concluded that the heat exchanger combined with high-thermal-conductivity water/MEG exhibits better energy storage capacity and working power,showing a wide application prospect in the field of cold energy storage.展开更多
Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering,energy conversion,and sustainability.This research addr...Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering,energy conversion,and sustainability.This research addresses the challenge of enhancing these critical aspects to ensure prolonged system performance and durability in the context of evolving energy technologies.This research analyses the anti-oxidation and filtration behaviours of micro and nano-scale structures in the context of electro-and photo-thermal energy conversion and also storage systems.A micro multiscale hierarchical structure strategy is presented to fabricate multi-scale double-layer porous wick evaporators with the electrospun nanofibers made of gelatin-polyamide 6(GPA6)and Ti_(3)C_(2)T_(x)MXene/silver nanowire with Cellulose Micro/NanoFibers(CMNF)cryogens by using spark plasma sintering(SPS)based high-pressure hydrothermal treatment model.An excellent anti-oxidation effect was offered by coating the film in thermal conditions and the anti-oxidation properties were further examined from 500℃to850℃.The results are analysed using Matlab software to improve the efficiency of energy conversion processes by integrating nanostructures into thermal systems,to increase energy output while minimizing losses.The silver nanowire is with a heat transfer coefficient of 78%,a mass remaining rate of 98.7%,and an energy storage efficiency of 23.8%.This study enhances energy density and duration by integrating nanostructures into thermal systems while minimizing energy losses,and it not only exhibits excellent anti-oxidation properties but also possesses superior filtration capabilities for designing and engineering multifunctional nanomaterials.展开更多
This paper aims to explore an efficient, cost-effective, and water-saving seasonal cold energy storage technique based on borehole heat exchangers to cool the condenser water in a 10 MW solar thermal power plant. The ...This paper aims to explore an efficient, cost-effective, and water-saving seasonal cold energy storage technique based on borehole heat exchangers to cool the condenser water in a 10 MW solar thermal power plant. The proposed seasonal cooling mechanism is designed for the areas under typical weather conditions to utilize the low ambient temperature during the winter season and to store cold energy. The main objective of this paper is to utilize the storage unit in the peak summer months to cool the condenser water and to replace the dry cooling system. Using the simulation platform transient system simulation program (TRNSYS), the borehole thermal energy storage (BTES) system model has been developed and the dynamic capacity of the system in the charging and discharging mode of cold energy for one-year operation is studied. The typical meteorological year (TMY) data of Dunhuang, Gansu province, in north-western China, is utilized to determine the lowest ambient temperature and operation time of the system to store cold energy. The proposed seasonal cooling system is capable of enhancing the efficiency of a solar thermal power plant up to 1.54% and 2.74% in comparison with the water-cooled condenser system and air-cooled condenser system respectively. The techno-economic assessment of the proposed technique also supports its integration with the condenser unit in the solar thermal power plant. This technique has also a great potential to save the water in desert areas.展开更多
基金This investigation was financially supported by the National Science Foundation of China(NSFC)(No.52078110)the Natural Science Foundation of Heilongjiang Province(No.LH2019E015)the Scientific Project of Ministry of Housing and Urban-Rural Development of China(No.2020-K-184,No.2021-K-160).
文摘Previous studies in literatures adequately emphasized that inserting fins into phase change material is among the most promising techniques to augment thermal performance of shell-and-tube latent heat thermal energy storage unit.In this study,the novel unequal-length fins are designed from the perspective of synergistic benefits of heat transfer and energy storage performance,and the effects of arrangement,number and total length of unequal-length fins are numerically investigated.Results show that utilization of fins with ascending length,when short and long fins are located in the inlet and outlet of heat transfer fluid respectively,can further promote the heat transfer and energy storage performance compared with equal length fins,and a maximum 6.17%and 0.43%increment of heat transfer performance and stored energy is achieved in full melting time,respectively.The number of unequal-length fins plays a major role in the energy storage,and 18.95%and 0.91%improvement of heat transfer performance and stored energy is realized when equipped with 2 unequal-length fins.A 21.17%improvement of the heat transfer performance is obtained when the total length of unequal-length fins is 18 mm.The present study is helpful to make further efforts to enhance heat transfer and energy storage of shell-and-tube latent heat thermal energy storage unit with unequal-length fins.
基金This work was supported by the National Natural Science Founda-tion of China(51976155)the Fundamental Research Funds for Central Universities(xtr042019019).The author(Xiaohu Yang)gratefully ac-knowledged the support of K.C.Wong Education Foundation.
文摘In this study,an innovative thermal energy storage design method was developed by adding the combination of metal foam and fin to phase change materials(PCMs).A numerical model was built and verified based on the comparison among the present model prediction,experimental measurements,and numerical results in open lit-erature.To highlight the novel design method,four cases including fin-PCM,foam-PCM,fin-foam-PCM,and PCM unit were compared by means of solidification features.The temperature distribution,solidification front propa-gation,and buoyancy-induced convection in the liquid PCM were accounted for.Numerical results demonstrated that metal foam outperformed fin regarding the improvement on solidification phase change.The combination of foam and fin achieved the best performance,leading to a 90.5%reduction in complete energy release time in comparison with the PCM unit.The proposed design method provided reference potentials for advancing energy storage engineering.However,buoyancy-induced convection in the liquid PCM before solidification was harmful to the formation of solidification front and its movement.A maximal 11.5%prolonging time for the complete solidification was found.
基金supported by the National Natural Science Foundation of China(Nos.51974225,51874229,51674188,51504182,51904224,51904225,51704229)Shaanxi Innovative Talents Cultivate Program-New-star Plan of Science and Technology(No.2018KJXX-083)+3 种基金Natural Science Basic Research Plan of Shaanxi Province of China(Nos.2018JM5161,2018JQ5183,2015JQ5187,2019JM-074)Scientific Research Program funded by the Shaanxi Provincial Education Department(Nos.15JK1466,19JK0543)China Postdoctoral Science Foundation(No.2015M582685)Outstanding Youth Science Fund of Xi’an University of Science and Technology(No.2018YQ2-01)。
文摘In view of the high temperature problem faced by mining activities,the coordinated mining of ore deposit and geothermal energy is a solution in line with the concept of green mining.The layered backfill body with finned double-pipe heat exchanger continuously exchanges heat with the surrounding thermal environment,which plays an effective role in gathering geothermal energy.In this paper,the heat storage process of each layered backfill body under different boundary conditions is simulated by Fluent.The results show the heat storage characteristic of layered backfill body can be significantly improved by adding fins to the double-pipe heat exchanger.On the whole,the heat storage effect of bottom layer backfill body(BLBB)is the best.The total heat storage capacity of top layer backfill body(TLBB),middle layer backfill body(MLBB)and BLBB with the finned double-pipe heat exchanger is 666.3 kJ,662.2 kJ,1003.0 kJ;1639.0 kJ,1760.8 kJ,1911.2 kJ and 1731.1 kJ,1953.3 kJ,1962.8 kJ respectively at 1 h,8 h and 24 h.This study explores the law of heat storage of layered backfill body under different boundary conditions and also expands the idea for layered backfill body to efficiently accumulate geothermal energy.
文摘In times of increasing global warming,enormous efforts are required to rapidly reduce greenhouse gas(GHG)emissions.Due to the EU’s target of climate neutrality by 2050 and the even more ambitious goal of becoming climate-neutral in Germany by 2045,it is necessary to systematically increase energy efficiency and decarbonize the industrial heat sector.The methods of heat integration can be used to exploit existing potentials for waste heat utilization and to integrate renewable technologies for heating and cooling.By using a non-stationary,multiperiod approach,additional energy savings can be achieved by integrating a thermal energy storage(TES)that enables heat transportation over time.This paper presents a simultaneous approach for thermal energy storage integration into multiperiod heat integration problems.The approach can be used to minimize energy demand,costs and CO 2 emissions and is demonstrated in two case studies.In case study 1,it is shown that the presented approach is capable of integrating a TES properly into a simple multiperiod heat integration problem with two periods.In case study 2,a simplified example from a cosmetics manufactory is investigated.The total utility demand can be reduced by up to 44.3%due to TES integration and the energetic optimal storage size can be determined as 125 m 3.The savings are strongly dependent on the constellation of heat flows between the periods,on the temperature levels and on the storage size.Significant reductions of energy demand,costs and CO 2 emissions can be achieved with TES being properly integrated into a suitable operating environment.
基金National Key R&D Program of China(Grant No.:2020YFA0210704).
文摘In this study,experimental and numerical investigations were conducted on a tube-fin heat-exchanger latent-heat cold energy storage unit.The fin side of the heat exchanger was filled with water as the energy storage medium,and modified expanded graphite(MEG)was employed to improve the thermal characteristics of water.The water contact angle of the expanded graphite decreased from 106.31°to 0°,and the hydrophilicity and the absorption rate of water significantly improved after the modification.Moreover,the experimental analyses of the charge/discharge process showed that the cooling capacity of the system filled with 90 wt.%water/MEG was 80.8%of that of pure water,whereas its cooling time was only 69.7%of that of pure water.The average power increased by 15.9%compared with that of water.The system filled with 90 wt.%water/MEG completed two energy charging and discharging cycles,whereas the system filled with water completed only 1.5 cycles within 15000 s.Furthermore,the effects of the flow rate and inlet temperature of the heat transfer fluid on the charging process were explored.Finally,a numerical model was built and validated to investigate the phase change behavior and the effect of the structure size on the performance of the system.The heat-exchanger fin spacing had no significant effect on the cold energy storage unit,whereas the vertical spacing of the tube pass had the highest effect.It can be concluded that the heat exchanger combined with high-thermal-conductivity water/MEG exhibits better energy storage capacity and working power,showing a wide application prospect in the field of cold energy storage.
文摘Thermal energy conversion and also storage system is to advance knowledge and develop practical solutions at the intersection of micro and nano-scale engineering,energy conversion,and sustainability.This research addresses the challenge of enhancing these critical aspects to ensure prolonged system performance and durability in the context of evolving energy technologies.This research analyses the anti-oxidation and filtration behaviours of micro and nano-scale structures in the context of electro-and photo-thermal energy conversion and also storage systems.A micro multiscale hierarchical structure strategy is presented to fabricate multi-scale double-layer porous wick evaporators with the electrospun nanofibers made of gelatin-polyamide 6(GPA6)and Ti_(3)C_(2)T_(x)MXene/silver nanowire with Cellulose Micro/NanoFibers(CMNF)cryogens by using spark plasma sintering(SPS)based high-pressure hydrothermal treatment model.An excellent anti-oxidation effect was offered by coating the film in thermal conditions and the anti-oxidation properties were further examined from 500℃to850℃.The results are analysed using Matlab software to improve the efficiency of energy conversion processes by integrating nanostructures into thermal systems,to increase energy output while minimizing losses.The silver nanowire is with a heat transfer coefficient of 78%,a mass remaining rate of 98.7%,and an energy storage efficiency of 23.8%.This study enhances energy density and duration by integrating nanostructures into thermal systems while minimizing energy losses,and it not only exhibits excellent anti-oxidation properties but also possesses superior filtration capabilities for designing and engineering multifunctional nanomaterials.
基金This work was supported by the Key Project of the National Natural Science Foundation of China for International Academic Exchanges(Grant No.51561145012)and the Gree Electric Appliances,Inc.Zhuhai,Guangdong Province.
文摘This paper aims to explore an efficient, cost-effective, and water-saving seasonal cold energy storage technique based on borehole heat exchangers to cool the condenser water in a 10 MW solar thermal power plant. The proposed seasonal cooling mechanism is designed for the areas under typical weather conditions to utilize the low ambient temperature during the winter season and to store cold energy. The main objective of this paper is to utilize the storage unit in the peak summer months to cool the condenser water and to replace the dry cooling system. Using the simulation platform transient system simulation program (TRNSYS), the borehole thermal energy storage (BTES) system model has been developed and the dynamic capacity of the system in the charging and discharging mode of cold energy for one-year operation is studied. The typical meteorological year (TMY) data of Dunhuang, Gansu province, in north-western China, is utilized to determine the lowest ambient temperature and operation time of the system to store cold energy. The proposed seasonal cooling system is capable of enhancing the efficiency of a solar thermal power plant up to 1.54% and 2.74% in comparison with the water-cooled condenser system and air-cooled condenser system respectively. The techno-economic assessment of the proposed technique also supports its integration with the condenser unit in the solar thermal power plant. This technique has also a great potential to save the water in desert areas.
