The conventional solar heating floor system contains a big water tank to store energy in the day time for heating at night,which takes much building space and is very heavy.In order to reduce the water tank volume eve...The conventional solar heating floor system contains a big water tank to store energy in the day time for heating at night,which takes much building space and is very heavy.In order to reduce the water tank volume even to cancel the tank,a novel structure of integrated water pipe floor heating system using shape-stabilized phase change materials(SSPCM)for thermal energy storage was developed.A numerical model was developed to analyze the performance of SSPCM floor heating system under the intermittent heating condition,which was verified by our experimental data.The thermal performance of the heating system and the effects of various factors on it were analyzed numerically.The factors including phase transition temperature,heat of fusion,thermal conductivity of SSPCM and thermal conductivity of the decoration material were analyzed.The results show that tm and kd are the most import influencing factors on the thermal performance of SSPCM floor heating system,since they determine the heat source temperature and thermal resistance between SSPCM plates and indoor air,respectively.Hm should be large to store enough thermal energy in the day time for nighttimes heating.The effects of kp can be ignored in this system.The SSPCM floor heating system has potential of making use of the daytime solar energy for heating at night efficiently in various climates when its structure is properly designed.展开更多
In thermal systems such as solar thermal and waste heat recovery systems, the available energy supply does not usually coincide in time with the process demand. Hence some form of thermal energy storage (TES) is neces...In thermal systems such as solar thermal and waste heat recovery systems, the available energy supply does not usually coincide in time with the process demand. Hence some form of thermal energy storage (TES) is necessary for the most effective utilization of the energy source. This study deals with the experimental evaluation of thermal performance of a packed bed latent heat TES unit integrated with solar flat plate collector. The TES unit contains paraffin as phase change material (PCM) filled in spherical capsules, which are packed in an insulated cylindrical storage tank. The water used as heat transfer fluid (HTF) to transfer heat from the solar collector to the storage tank also acts as sensible heat storage material. Charging experiments were carried out at varying inlet fluid temperatures to examine the effects of porosity and HTF flow rate on the storage unit performance. The performance parameters such as instantaneous heat stored, cumulative heat stored, charging rate and system efficiency are studied. Discharging experiments were carried out by both continuous and batchwise processes to recover the stored heat, and the results are presented.展开更多
In this article, a new kind of solar fresh air system is designed in order to realize the improvement of thermal efficiency by the integrated application of the PCMs and heat pipe technology. Under the adequate sunshi...In this article, a new kind of solar fresh air system is designed in order to realize the improvement of thermal efficiency by the integrated application of the PCMs and heat pipe technology. Under the adequate sunshine condition, the fresh air is directly delivered into the indoor environment after being heated by the solar collector. When the sun radiation is reduced, the heated air temperature can not satisfy the need of supply of air temperature.The main heat source is changed to phase change heat storage equipment instead of solar energy. The system adopt heat pipe for a high-efficiency and isothermal heat transfer which recover the shortcomings of PCMs such as： low coefficient of thermal conductivity and poor thermal efficiency. This article establishes the physical model of phase change solar energy fresh air thermal storage system and creates the mathematical model of its unsteady heat transfer to simulate and analyse the operation process by using Fluent software. The results of the study show that, compared to normal fresh air system, the phase change solar energy fresh air thermal storage system has a significant improvement in energy saving and indoor comfort level and will play an important role in the energy sustainable development.展开更多
This paper reports the performance investigation of a newly developed Latent Heat Thermal Battery(LHTB)integrated with a solar collector as the main source of heat.The LHTB is a new solution in the field of thermal st...This paper reports the performance investigation of a newly developed Latent Heat Thermal Battery(LHTB)integrated with a solar collector as the main source of heat.The LHTB is a new solution in the field of thermal storage and developed based on the battery concept in terms of recharge ability,portability and usability as a standalone device.It is fabricated based on the thermal battery storage concept and consists of a plate-fin and tube heat exchanger located inside the battery casing and paraffin wax which is used as a latent heat storage material.Solar thermal energy is absorbed by solar collector and transferred to the LHTB using water as Heat Transfer Fluid(HTF).Charging experiments have been conducted with a HTF at three different temperatures of 68°C,88°C and 108°C and three different flow rates of 30,60 and 120 l/h.It is followed by discharging experiments on fully charged LHTB at three different temperatures of 68°C,88°C and 108°C using HTF at three different flow rates of 30,60 and 120 l/h.It is found that both higher HTF inlet temperature and flow rate have a positive impact on stored thermal energy.However,charging efficiency was decreased by increasing the HTF flow rate.The highest charging efficiency of 29%was achieved using HTF of 108°C at a flow rate of 30 l/h.Most of paraffin melted in this case,while part of the paraffin remained solid in other experiments.On the other hand,the results from discharging experiments revealed that both recovered thermal energy and recovery efficiency increased by either increasing the LHTB temperature or HTF flow rate.Highest recovered thermal energy of 5,825 KJ at 35%recovery efficiency achieved at LHTB of 108°C using 120 l/h of HTF.展开更多
Bionics provides a positive and beneficial impact on the development of various materials and systems, which has been widely used in energy storage, heat transfer enhancement, and solar thermochemical reactions. In th...Bionics provides a positive and beneficial impact on the development of various materials and systems, which has been widely used in energy storage, heat transfer enhancement, and solar thermochemical reactions. In this paper, the idea of heat storage unit with biomimetic alveoli structure is proposed and introduced to increase the heat transfer area and improve the thermal performance of the packed-bed latent heat thermal energy storage(LHTES) system. The effects of heat storage unit structure on temperature distribution, liquid fraction, thermal storage capacity, and other performance indexes of the conventional model and biomimetic model are analyzed. The numerical results indicate that the biomimetic alveoli structure can improve the thermal response of heat storage unit, increase the specific surface area, and achieve a faster heat storage process of the packed-bed compared with the conventional structure. Among various existing models, the double-cell model has a significant improvement.Compared with the conventional model, the maximum increase of liquid fraction and charging efficiency are 9.8% and 6.4%,respectively. This study can provide references to optimize packed-bed LHTES and improve its thermal performance under practical conditions.展开更多
基金Supported by National 11th Five-Year Plan of Dept.of Science,China(2006BAA04B02,2006BAJ02A09)
文摘The conventional solar heating floor system contains a big water tank to store energy in the day time for heating at night,which takes much building space and is very heavy.In order to reduce the water tank volume even to cancel the tank,a novel structure of integrated water pipe floor heating system using shape-stabilized phase change materials(SSPCM)for thermal energy storage was developed.A numerical model was developed to analyze the performance of SSPCM floor heating system under the intermittent heating condition,which was verified by our experimental data.The thermal performance of the heating system and the effects of various factors on it were analyzed numerically.The factors including phase transition temperature,heat of fusion,thermal conductivity of SSPCM and thermal conductivity of the decoration material were analyzed.The results show that tm and kd are the most import influencing factors on the thermal performance of SSPCM floor heating system,since they determine the heat source temperature and thermal resistance between SSPCM plates and indoor air,respectively.Hm should be large to store enough thermal energy in the day time for nighttimes heating.The effects of kp can be ignored in this system.The SSPCM floor heating system has potential of making use of the daytime solar energy for heating at night efficiently in various climates when its structure is properly designed.
基金Project supported by Sri Venkateswara college of Engineering,India.
文摘In thermal systems such as solar thermal and waste heat recovery systems, the available energy supply does not usually coincide in time with the process demand. Hence some form of thermal energy storage (TES) is necessary for the most effective utilization of the energy source. This study deals with the experimental evaluation of thermal performance of a packed bed latent heat TES unit integrated with solar flat plate collector. The TES unit contains paraffin as phase change material (PCM) filled in spherical capsules, which are packed in an insulated cylindrical storage tank. The water used as heat transfer fluid (HTF) to transfer heat from the solar collector to the storage tank also acts as sensible heat storage material. Charging experiments were carried out at varying inlet fluid temperatures to examine the effects of porosity and HTF flow rate on the storage unit performance. The performance parameters such as instantaneous heat stored, cumulative heat stored, charging rate and system efficiency are studied. Discharging experiments were carried out by both continuous and batchwise processes to recover the stored heat, and the results are presented.
文摘In this article, a new kind of solar fresh air system is designed in order to realize the improvement of thermal efficiency by the integrated application of the PCMs and heat pipe technology. Under the adequate sunshine condition, the fresh air is directly delivered into the indoor environment after being heated by the solar collector. When the sun radiation is reduced, the heated air temperature can not satisfy the need of supply of air temperature.The main heat source is changed to phase change heat storage equipment instead of solar energy. The system adopt heat pipe for a high-efficiency and isothermal heat transfer which recover the shortcomings of PCMs such as： low coefficient of thermal conductivity and poor thermal efficiency. This article establishes the physical model of phase change solar energy fresh air thermal storage system and creates the mathematical model of its unsteady heat transfer to simulate and analyse the operation process by using Fluent software. The results of the study show that, compared to normal fresh air system, the phase change solar energy fresh air thermal storage system has a significant improvement in energy saving and indoor comfort level and will play an important role in the energy sustainable development.
基金the University of Malaya,Faculty of Engineering,Faculty Research Grant No.GPF023A-2019.
文摘This paper reports the performance investigation of a newly developed Latent Heat Thermal Battery(LHTB)integrated with a solar collector as the main source of heat.The LHTB is a new solution in the field of thermal storage and developed based on the battery concept in terms of recharge ability,portability and usability as a standalone device.It is fabricated based on the thermal battery storage concept and consists of a plate-fin and tube heat exchanger located inside the battery casing and paraffin wax which is used as a latent heat storage material.Solar thermal energy is absorbed by solar collector and transferred to the LHTB using water as Heat Transfer Fluid(HTF).Charging experiments have been conducted with a HTF at three different temperatures of 68°C,88°C and 108°C and three different flow rates of 30,60 and 120 l/h.It is followed by discharging experiments on fully charged LHTB at three different temperatures of 68°C,88°C and 108°C using HTF at three different flow rates of 30,60 and 120 l/h.It is found that both higher HTF inlet temperature and flow rate have a positive impact on stored thermal energy.However,charging efficiency was decreased by increasing the HTF flow rate.The highest charging efficiency of 29%was achieved using HTF of 108°C at a flow rate of 30 l/h.Most of paraffin melted in this case,while part of the paraffin remained solid in other experiments.On the other hand,the results from discharging experiments revealed that both recovered thermal energy and recovery efficiency increased by either increasing the LHTB temperature or HTF flow rate.Highest recovered thermal energy of 5,825 KJ at 35%recovery efficiency achieved at LHTB of 108°C using 120 l/h of HTF.
基金supported by the National Key Research and Development Program of China (Grant No. 2018YFA0702300)the National Natural Science Foundation of China (Grant Nos. 52006094 and 52076064)the Taishan Scholars of Shandong Province (Grant No. tsqn201812105)。
文摘Bionics provides a positive and beneficial impact on the development of various materials and systems, which has been widely used in energy storage, heat transfer enhancement, and solar thermochemical reactions. In this paper, the idea of heat storage unit with biomimetic alveoli structure is proposed and introduced to increase the heat transfer area and improve the thermal performance of the packed-bed latent heat thermal energy storage(LHTES) system. The effects of heat storage unit structure on temperature distribution, liquid fraction, thermal storage capacity, and other performance indexes of the conventional model and biomimetic model are analyzed. The numerical results indicate that the biomimetic alveoli structure can improve the thermal response of heat storage unit, increase the specific surface area, and achieve a faster heat storage process of the packed-bed compared with the conventional structure. Among various existing models, the double-cell model has a significant improvement.Compared with the conventional model, the maximum increase of liquid fraction and charging efficiency are 9.8% and 6.4%,respectively. This study can provide references to optimize packed-bed LHTES and improve its thermal performance under practical conditions.
