The experiment is studied on thermal distribution in the thermal energy storage system with non-phase change materials (NPCM): NaNO3, KNO3 and NaCl in the range of 25°C - 250°C. The cylindrical storage syste...The experiment is studied on thermal distribution in the thermal energy storage system with non-phase change materials (NPCM): NaNO3, KNO3 and NaCl in the range of 25°C - 250°C. The cylindrical storage system was made of stainless steel with 25.6 cm-diameter and 26.8 cm-height that was contained of these NPCM. There was one pipe for heat transfer fluid (HTF) with 1.27 cm-diameter that manipulates in the storage tank and submerges to NPCM. The inner pipe was connected to the 2.27 cm-diameter outer HTF tube. The tube was further connected to the thermal pump, heater and load. The pump circulates the synthetic oil (Thermia oil) within the pipe for heat transferring purposes (charging and discharging). An electric heater is used as the heat source. The limitation of the charging oil temperature is maintained at 250°C with the flow rates in the range of 0.58 to 1.45 kg/s whereas the inlet temperature of the discharge oil is maintained at 25°C. Thermal performances of TES (thermal energy storage) such as charging and discharging times, radial thermal distribution, energy storage capacity and energy efficiency have been evaluated. The experimental results show that the radial thermal distribution of NaCl for TR inside, TR middle and TR outside was optimum of temperature down to NaNO3 and KNO3 respectively. Comparison of NPCMs with oil, flow rates for NaCl were charging and discharging heat transfer than KNO3 and NaNO3. The thermal stored NaCl ranged from 5712 - 5912 J;KNO3 ranged from 7350 - 7939 J and NaNO3 ranged from 6623 - 6930 J respectively. The thermal energy stored for experimental results got with along the KNO3, NaNO3 and NaCl respectively. The thermal energy efficiency of NaCl, KNO3 and NaNO3 was in the range 66% - 70%.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
The heat storage performance of latent heat storage systems is not good due to the poor thermal conductivity of phase change materials.In this paper,a new type of pointer-shaped fins combining rectangular and triangul...The heat storage performance of latent heat storage systems is not good due to the poor thermal conductivity of phase change materials.In this paper,a new type of pointer-shaped fins combining rectangular and triangular fins has been employed to numerically simulate the melting process in the heat storage tank,and the fin geometry parameter effects on heat storage performance have been studied.The results indicate that compared with the bare tube and the rectangular finned tank,the melting time of the phase change material in the pointer-shaped finned tank is reduced by 64.2%and 15.1%,respectively.The closer the tip of the triangular fin is to the hot wall,the better the heat transfer efficiency.The optimal height of the triangular fin is about 8 mm.Increasing the number of fins from 4 to 6 and from 6 to 8 reduces the melting time by 16.0%and 16.7%respectively.However,increasing the number of fins from 8 to 10 only reduces the melting time by 8.4%.When the fin dimensionless length is increased from 0.3 to 0.5 and from 0.5 to 0.7,the melting time is shortened by 17.5%and 13.0%.But the melting time is only reduced by 2.9%when the dimensionless fin length is increased from 0.7 to 0.9.For optimising the design of the thermal storage system,the results can provide a reference value.展开更多
Water is essential to life. The origin and continuation of mankind is based on water. The supply of drinking water is an important problem for the developing countries. Among the non-conventional methods to desalinate...Water is essential to life. The origin and continuation of mankind is based on water. The supply of drinking water is an important problem for the developing countries. Among the non-conventional methods to desalinate brackish water or seawater, is solar distillation. The solar still is the most economical way to accomplish this objective. Tamilnadu lies in the high solar radiation band and the vast solar potential can be utilized to convert saline water to potable water. The sun’s energy heats water to the point of evaporation. When water evaporates, water vapour rises leaving the impurities like salts, heavy metals and condensate on the underside of the glass cover. Sunlight has the advantage of zero fuel cost but it requires more space and generally more equipment. Solar distillation has low yield, but safe and pure supplies of water in remote areas. In this context, the design modification of a single basin solar still has been discussed to improve the solar still performance through increasing the production rate of distilled water. The attempts are also made to increase the productivity of water by using different absorbing materials, depths of water, heat storage medium and also by providing low pressure inside the still basin. They greatly improve the rate of evaporation and hence the rate of condensation on the cooler surface. The theoretical results agree well with the experimental ones.展开更多
The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation.A one-dimensional,non-equilibrium packed bed laten...The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation.A one-dimensional,non-equilibrium packed bed latent heat storage mathematical model was established and the applicability of the model was verified.The results demonstrate that the inlet temperature of the heat transfer fluid(HTF)had the greatest influence on each index.When the inlet temperature increased from 333 K to 363 K,exergy destruction increased threefold,effective heat storage time decreased by 67%,effective heat storage increased by 38%,and exergy efficiency decreased by 11%.The decrease of the capsule diameter had a positive effect on each evaluation index.According to the sensitivity analysis,the order of importance of each parameter within their variation range was HTF inlet temperature,HTF flow rate,PCM capsule size and PCM initial temperature.展开更多
Solar greenhouses have been used for producing vegetables in northern China during early spring,late autumn or over-winter.To improve the thermal performance of solar greenhouses,a traditional type and a retrofitted d...Solar greenhouses have been used for producing vegetables in northern China during early spring,late autumn or over-winter.To improve the thermal performance of solar greenhouses,a traditional type and a retrofitted design were comparatively evaluated.In the retrofitted design,three adjustments were incorporated:the material and structure of the walls,south-facing roof angle,and structure of the north-facing back-roof.The results indicated that the thermal and light performance of the retrofitted greenhouse was much better than that of the traditional greenhouse.Specifically,the daily mean temperature,minimum air temperature,and soil temperature inside the greenhouses after retrofit ting were increased by 1.3,2.4,and 1.9℃,respectively,meanwhile,the daily total solar radiation and PAR were increased by 28.2%and 9.2%,respectively.The wall temperature and its daily variation range were reduced with increasing depth and height.The characteristic analysis of heat storage and release indicated that higher locations have longer heat storage,and shorter heat release time in vertical direction,as well as a lower ratio of heat release to storage.In horizontal direction,the western wall has the shortest heat storage time but the highest heat release flux density.Altogether,the heat storage time of the wall is 1.5 h less than that of the soil.The heat storage flux density of the wall is 1.5 times of that of the soil,but the heat release flux is only 61%of the soil’s value.The total wall heat storage is half of that of the soil in the greenhouse;the total wall heat release amount is only a quarter of that of the soil.Therefore,the thermal environment of solar greenhouses can be further improved by improving the thermal insulation properties of the wall.展开更多
This paper introduces a novel solar-assisted heat pump system with phase change energy storage and describes the methodology used to analyze the performance of the proposed system.A mathematical model was established ...This paper introduces a novel solar-assisted heat pump system with phase change energy storage and describes the methodology used to analyze the performance of the proposed system.A mathematical model was established for the key parts of the system including solar evaporator,condenser,phase change energy storage tank,and compressor.In parallel to the modelling work,an experimental set-up of the proposed solar energy storage heat pump system was developed.The experimental data showed that the designed system is capable of meeting cold day heating demands in rural areas of Yanbian city located in Jilin province of China.In day-time operation,the solar heat pump system stores excess energy in the energy storage tank for heating purposes.A desired indoor temperature was achieved;the average coefficient of performance of solar heat pump was identified as 4.5,and the system showed a stable performance throughout the day.In night-time operation,the energy stored in the storage tank was released through a liquid-solid change of phase in the employed phase-change material.In this way,the provision of continuous heat for ten hours was ensured within the building,and the desired indoor air conditions were achieved.展开更多
文摘The experiment is studied on thermal distribution in the thermal energy storage system with non-phase change materials (NPCM): NaNO3, KNO3 and NaCl in the range of 25°C - 250°C. The cylindrical storage system was made of stainless steel with 25.6 cm-diameter and 26.8 cm-height that was contained of these NPCM. There was one pipe for heat transfer fluid (HTF) with 1.27 cm-diameter that manipulates in the storage tank and submerges to NPCM. The inner pipe was connected to the 2.27 cm-diameter outer HTF tube. The tube was further connected to the thermal pump, heater and load. The pump circulates the synthetic oil (Thermia oil) within the pipe for heat transferring purposes (charging and discharging). An electric heater is used as the heat source. The limitation of the charging oil temperature is maintained at 250°C with the flow rates in the range of 0.58 to 1.45 kg/s whereas the inlet temperature of the discharge oil is maintained at 25°C. Thermal performances of TES (thermal energy storage) such as charging and discharging times, radial thermal distribution, energy storage capacity and energy efficiency have been evaluated. The experimental results show that the radial thermal distribution of NaCl for TR inside, TR middle and TR outside was optimum of temperature down to NaNO3 and KNO3 respectively. Comparison of NPCMs with oil, flow rates for NaCl were charging and discharging heat transfer than KNO3 and NaNO3. The thermal stored NaCl ranged from 5712 - 5912 J;KNO3 ranged from 7350 - 7939 J and NaNO3 ranged from 6623 - 6930 J respectively. The thermal energy stored for experimental results got with along the KNO3, NaNO3 and NaCl respectively. The thermal energy efficiency of NaCl, KNO3 and NaNO3 was in the range 66% - 70%.
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financially supported by the National Natural Science Foundation of China(Grant No.51876147)。
文摘The heat storage performance of latent heat storage systems is not good due to the poor thermal conductivity of phase change materials.In this paper,a new type of pointer-shaped fins combining rectangular and triangular fins has been employed to numerically simulate the melting process in the heat storage tank,and the fin geometry parameter effects on heat storage performance have been studied.The results indicate that compared with the bare tube and the rectangular finned tank,the melting time of the phase change material in the pointer-shaped finned tank is reduced by 64.2%and 15.1%,respectively.The closer the tip of the triangular fin is to the hot wall,the better the heat transfer efficiency.The optimal height of the triangular fin is about 8 mm.Increasing the number of fins from 4 to 6 and from 6 to 8 reduces the melting time by 16.0%and 16.7%respectively.However,increasing the number of fins from 8 to 10 only reduces the melting time by 8.4%.When the fin dimensionless length is increased from 0.3 to 0.5 and from 0.5 to 0.7,the melting time is shortened by 17.5%and 13.0%.But the melting time is only reduced by 2.9%when the dimensionless fin length is increased from 0.7 to 0.9.For optimising the design of the thermal storage system,the results can provide a reference value.
文摘Water is essential to life. The origin and continuation of mankind is based on water. The supply of drinking water is an important problem for the developing countries. Among the non-conventional methods to desalinate brackish water or seawater, is solar distillation. The solar still is the most economical way to accomplish this objective. Tamilnadu lies in the high solar radiation band and the vast solar potential can be utilized to convert saline water to potable water. The sun’s energy heats water to the point of evaporation. When water evaporates, water vapour rises leaving the impurities like salts, heavy metals and condensate on the underside of the glass cover. Sunlight has the advantage of zero fuel cost but it requires more space and generally more equipment. Solar distillation has low yield, but safe and pure supplies of water in remote areas. In this context, the design modification of a single basin solar still has been discussed to improve the solar still performance through increasing the production rate of distilled water. The attempts are also made to increase the productivity of water by using different absorbing materials, depths of water, heat storage medium and also by providing low pressure inside the still basin. They greatly improve the rate of evaporation and hence the rate of condensation on the cooler surface. The theoretical results agree well with the experimental ones.
基金supported by the National Key R8cD Program of China(No.2018YFB0905104)the Science and Technology Planning Project of Jilin Province(No.20180201006SF).
文摘The goal of this study is to investigate the effect of key design parameters on the thermal performance of the packed bed heat storage device by numerical calculation.A one-dimensional,non-equilibrium packed bed latent heat storage mathematical model was established and the applicability of the model was verified.The results demonstrate that the inlet temperature of the heat transfer fluid(HTF)had the greatest influence on each index.When the inlet temperature increased from 333 K to 363 K,exergy destruction increased threefold,effective heat storage time decreased by 67%,effective heat storage increased by 38%,and exergy efficiency decreased by 11%.The decrease of the capsule diameter had a positive effect on each evaluation index.According to the sensitivity analysis,the order of importance of each parameter within their variation range was HTF inlet temperature,HTF flow rate,PCM capsule size and PCM initial temperature.
基金The study was financially supported by the National Natural Science Foundation of China(31601794)International cooperation fund of Beijing Academy of Agriculture and Forestry Sciences(GJHZ2018-04)the project of Facilities Horticulture Innovation Team of Beijing Academy of Agriculture and Forestry Sciences(JNKST201615).
文摘Solar greenhouses have been used for producing vegetables in northern China during early spring,late autumn or over-winter.To improve the thermal performance of solar greenhouses,a traditional type and a retrofitted design were comparatively evaluated.In the retrofitted design,three adjustments were incorporated:the material and structure of the walls,south-facing roof angle,and structure of the north-facing back-roof.The results indicated that the thermal and light performance of the retrofitted greenhouse was much better than that of the traditional greenhouse.Specifically,the daily mean temperature,minimum air temperature,and soil temperature inside the greenhouses after retrofit ting were increased by 1.3,2.4,and 1.9℃,respectively,meanwhile,the daily total solar radiation and PAR were increased by 28.2%and 9.2%,respectively.The wall temperature and its daily variation range were reduced with increasing depth and height.The characteristic analysis of heat storage and release indicated that higher locations have longer heat storage,and shorter heat release time in vertical direction,as well as a lower ratio of heat release to storage.In horizontal direction,the western wall has the shortest heat storage time but the highest heat release flux density.Altogether,the heat storage time of the wall is 1.5 h less than that of the soil.The heat storage flux density of the wall is 1.5 times of that of the soil,but the heat release flux is only 61%of the soil’s value.The total wall heat storage is half of that of the soil in the greenhouse;the total wall heat release amount is only a quarter of that of the soil.Therefore,the thermal environment of solar greenhouses can be further improved by improving the thermal insulation properties of the wall.
基金This research is supported by the National Natural Science Foundation of China(No.51906020)the Natural Science Foundation of Jiangsu Educational committee(No.18KJD480001).
文摘This paper introduces a novel solar-assisted heat pump system with phase change energy storage and describes the methodology used to analyze the performance of the proposed system.A mathematical model was established for the key parts of the system including solar evaporator,condenser,phase change energy storage tank,and compressor.In parallel to the modelling work,an experimental set-up of the proposed solar energy storage heat pump system was developed.The experimental data showed that the designed system is capable of meeting cold day heating demands in rural areas of Yanbian city located in Jilin province of China.In day-time operation,the solar heat pump system stores excess energy in the energy storage tank for heating purposes.A desired indoor temperature was achieved;the average coefficient of performance of solar heat pump was identified as 4.5,and the system showed a stable performance throughout the day.In night-time operation,the energy stored in the storage tank was released through a liquid-solid change of phase in the employed phase-change material.In this way,the provision of continuous heat for ten hours was ensured within the building,and the desired indoor air conditions were achieved.
