This research evaluates the performance of a Phase Change Material(PCM)battery integrated into the climate system of a new transparent meeting center.The main research questions are:a.“Can the performance of the batt...This research evaluates the performance of a Phase Change Material(PCM)battery integrated into the climate system of a new transparent meeting center.The main research questions are:a.“Can the performance of the battery be calculated?”and b.“Can the battery reduce the heating and cooling energy demand in a significant way?”The first question is answered in this document.In order to be able to answer the second question,especially the way the heat loading in winter should be improved,then more research is necessary.In addition to the thermal battery,which consists of Phase Change Material plates,the climate system has a cross-flow heat exchanger and a heat pump.The battery should play a central role in closing the thermal balance of the lightweight building,which can be loaded with hot return or cold outdoor air.The temperature of the battery plates is monitored by multi-sensors and simulated by the use of PHOENICS(Computational Fluid Dynamics)and MATLAB.This paper reports reasonable agreement between the numerical predictions and the measurements,with a maximum variance of 10%.The current coefficient of performance for heating and cooling is already high,more than 27.There is scope for increasing this much further by making use of the very low-pressure difference of the battery(below 25 Pascal),low pressure fans and the ventilation system as a whole.展开更多
A thermal heat storage system with an energy content of 40 kWh and a temperature of 58°C will be presented. This storage system is suitable for supporting the use of renewable energies in buildings and for absorb...A thermal heat storage system with an energy content of 40 kWh and a temperature of 58°C will be presented. This storage system is suitable for supporting the use of renewable energies in buildings and for absorbing solar heat, heat from co-generation and heat pumps or electric heat from excess wind and solar power. The storage system is equipped with a plate heat exchanger that is so powerful that even with small temperature differences between the flow temperature and the storage temperature a high load dynamic is achieved. The storage system has a performance of 2.8 kW at 4 K and 10.6 kW at a temperature difference of 10 K. Thus, large performance variations in solar thermal systems or CHP plants can be buffered very well. Further a storage charge function Q(T, t) will be presented to characterize the performance of the storage.展开更多
One of the likely methods for enhancing heat transfer in a latent thermal energy storage system is the conception of a thermal unit.In this study,the orientation of oval tubes(horizontal,vertical,and oblique)in phase ...One of the likely methods for enhancing heat transfer in a latent thermal energy storage system is the conception of a thermal unit.In this study,the orientation of oval tubes(horizontal,vertical,and oblique)in phase change material(PCM,C_(19)-C_(20))-based shell-tube heat exchanger was analyzed with respect to the metal foam(MF)type(graphite,copper,and nickel)in comparison to the case of pure PCM.For this purpose,a two-dimensional mathematical model was developed to investigate the thermal efficiency of the PCM-metal foam based composite energy storage unit.It was concluded that the orientation of the oval tubes(oblique,horizontal,and vertical)has a negligible impact on the performance of the thermal unit during the melting/solidification processes.Based on the liquid/solid fraction,total enthalpy and the average temperature in the annular space,the performance of a heat exchanger during fusion/solidification periods is in the order:copper-MF>graphite-MF>nickel-MF>pure PCM.Whatever the adopted MF or the geometry of tubes,the melting process is expedited compared to the solidification mechanism.展开更多
Arranging heat exchanger in filling body to extract geothermal energy is an effective way to alleviate the problems of high ground pressure and high ground temperature in deep resource exploitation.Filling body with c...Arranging heat exchanger in filling body to extract geothermal energy is an effective way to alleviate the problems of high ground pressure and high ground temperature in deep resource exploitation.Filling body with casing heat exchanger was acted as research object,encapsulating phase change materials(PCMs)in annular space.During heat storage and heat release process,the effects of different PCMs on temperature distribution,phase-change process and heat transfer performance were studied.The result indicates:During heat storage process,the temperature increases rapidly and the melting process is accelerated for the position closer surrounding rock.CaCl_(2)·6H_(2)O/EG can make filling body complete heat storage process in the shortest time because of its good thermal diffusivity.The heat storage capacity of PCMs backfill is significantly higher than that of ordinary backfill;it increases by 36.6%-67.3%at heat storage of 10 h.During heat release process,the closer to the heat exchange tube,the greater the temperature drop in filling body.The maximum value of heat release rate and heat release capacity is in CaCl_(2)·6H_(2)O/EG backfill,it can release 116.4%more heat than RT35backfill after heat release of 12 h,the maximum value of effectiveness and its heat transfer rate also is in CaCl_(2)·6H_(2)O/EG backfill.This paper provides the basic data for the selection of PCMs in phase-change thermal storage filling body.展开更多
Heat sinks were invented to absorb heat from an electronic circuit conduct, and then to dissipate or radiate this heat to the surrounding supposedly, ventilated space, at a rate equal to or faster than that of its bui...Heat sinks were invented to absorb heat from an electronic circuit conduct, and then to dissipate or radiate this heat to the surrounding supposedly, ventilated space, at a rate equal to or faster than that of its buildup. Ventilation was not initially recognized as an essential factor to thermal dispersion. However, as electronic circuit-boards continued to heat up, circuit failure became a problem, forcing the inclusion of miniaturized high speed fans. Later, heat sinks with fins and quiet fans were incorporated in most manufactured circuits. Now heat sinks come in the form of a fan with fans made to function as fins to disperse heat. Heat sinks absorb and radiate excess heat from circuit-boards in order to prolong the circuit’s life span. The higher the thermal conductivity of the material used the more efficient and effective the heat sink is. This paper is an attempt to theoretically design a heat sink with a temperature gradient lower than that of the circuit board’s excess heat.展开更多
基金The project is financed via a public grant of the Rijksdienst Voor Ondernemend Nederland(RVO,https://www.rvo.nl/)within the Urban Energy 2018 Research-Line with Grant No.TEUE318008.The grant is awarded to the following consortium:The Delft University of Technology(https://www.tudelft.nl/en),Van Dorp B.V.,Hunter Douglas Europe B.V.(https://www.hunterdouglasarchitectural.eu/),Priva B.V.(https://www.priva.com/nl)and the Green Village Foundation(https://www.thegreenvillage.org/en/).
文摘This research evaluates the performance of a Phase Change Material(PCM)battery integrated into the climate system of a new transparent meeting center.The main research questions are:a.“Can the performance of the battery be calculated?”and b.“Can the battery reduce the heating and cooling energy demand in a significant way?”The first question is answered in this document.In order to be able to answer the second question,especially the way the heat loading in winter should be improved,then more research is necessary.In addition to the thermal battery,which consists of Phase Change Material plates,the climate system has a cross-flow heat exchanger and a heat pump.The battery should play a central role in closing the thermal balance of the lightweight building,which can be loaded with hot return or cold outdoor air.The temperature of the battery plates is monitored by multi-sensors and simulated by the use of PHOENICS(Computational Fluid Dynamics)and MATLAB.This paper reports reasonable agreement between the numerical predictions and the measurements,with a maximum variance of 10%.The current coefficient of performance for heating and cooling is already high,more than 27.There is scope for increasing this much further by making use of the very low-pressure difference of the battery(below 25 Pascal),low pressure fans and the ventilation system as a whole.
文摘A thermal heat storage system with an energy content of 40 kWh and a temperature of 58°C will be presented. This storage system is suitable for supporting the use of renewable energies in buildings and for absorbing solar heat, heat from co-generation and heat pumps or electric heat from excess wind and solar power. The storage system is equipped with a plate heat exchanger that is so powerful that even with small temperature differences between the flow temperature and the storage temperature a high load dynamic is achieved. The storage system has a performance of 2.8 kW at 4 K and 10.6 kW at a temperature difference of 10 K. Thus, large performance variations in solar thermal systems or CHP plants can be buffered very well. Further a storage charge function Q(T, t) will be presented to characterize the performance of the storage.
基金supported by the Ministry of Higher Education and Scientific Research of Algeria(Project No.:A16N01UN250320220002)the General Directorate of Scientific Research and Technological Development(GD-SRTD).
文摘One of the likely methods for enhancing heat transfer in a latent thermal energy storage system is the conception of a thermal unit.In this study,the orientation of oval tubes(horizontal,vertical,and oblique)in phase change material(PCM,C_(19)-C_(20))-based shell-tube heat exchanger was analyzed with respect to the metal foam(MF)type(graphite,copper,and nickel)in comparison to the case of pure PCM.For this purpose,a two-dimensional mathematical model was developed to investigate the thermal efficiency of the PCM-metal foam based composite energy storage unit.It was concluded that the orientation of the oval tubes(oblique,horizontal,and vertical)has a negligible impact on the performance of the thermal unit during the melting/solidification processes.Based on the liquid/solid fraction,total enthalpy and the average temperature in the annular space,the performance of a heat exchanger during fusion/solidification periods is in the order:copper-MF>graphite-MF>nickel-MF>pure PCM.Whatever the adopted MF or the geometry of tubes,the melting process is expedited compared to the solidification mechanism.
基金supported by the National Natural Science Foundation of China(Nos.51974225,51674188,51874229,51504182,51904224,51904225,51704229)Shaanxi Innovative Talents Cultivate Program-New-star Plan of Science and Technology(No.2018KJXX-083)+4 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)the Scientific Research Program funded by Xi’an Science and Technology Bureau(No.201805036YD14CG20)。
文摘Arranging heat exchanger in filling body to extract geothermal energy is an effective way to alleviate the problems of high ground pressure and high ground temperature in deep resource exploitation.Filling body with casing heat exchanger was acted as research object,encapsulating phase change materials(PCMs)in annular space.During heat storage and heat release process,the effects of different PCMs on temperature distribution,phase-change process and heat transfer performance were studied.The result indicates:During heat storage process,the temperature increases rapidly and the melting process is accelerated for the position closer surrounding rock.CaCl_(2)·6H_(2)O/EG can make filling body complete heat storage process in the shortest time because of its good thermal diffusivity.The heat storage capacity of PCMs backfill is significantly higher than that of ordinary backfill;it increases by 36.6%-67.3%at heat storage of 10 h.During heat release process,the closer to the heat exchange tube,the greater the temperature drop in filling body.The maximum value of heat release rate and heat release capacity is in CaCl_(2)·6H_(2)O/EG backfill,it can release 116.4%more heat than RT35backfill after heat release of 12 h,the maximum value of effectiveness and its heat transfer rate also is in CaCl_(2)·6H_(2)O/EG backfill.This paper provides the basic data for the selection of PCMs in phase-change thermal storage filling body.
文摘Heat sinks were invented to absorb heat from an electronic circuit conduct, and then to dissipate or radiate this heat to the surrounding supposedly, ventilated space, at a rate equal to or faster than that of its buildup. Ventilation was not initially recognized as an essential factor to thermal dispersion. However, as electronic circuit-boards continued to heat up, circuit failure became a problem, forcing the inclusion of miniaturized high speed fans. Later, heat sinks with fins and quiet fans were incorporated in most manufactured circuits. Now heat sinks come in the form of a fan with fans made to function as fins to disperse heat. Heat sinks absorb and radiate excess heat from circuit-boards in order to prolong the circuit’s life span. The higher the thermal conductivity of the material used the more efficient and effective the heat sink is. This paper is an attempt to theoretically design a heat sink with a temperature gradient lower than that of the circuit board’s excess heat.
