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
Chemical heat storage is a promising technology for improving thermal energy efficiency. In this study, CaCl<sub>2</sub> and H<sub>2</sub>O were selected as a reaction system for utilization of...Chemical heat storage is a promising technology for improving thermal energy efficiency. In this study, CaCl<sub>2</sub> and H<sub>2</sub>O were selected as a reaction system for utilization of low-grade exhaust heat that is cooler than 200<span style="white-space:nowrap;"><span style="white-space:nowrap;">°</span></span>C. Heat discharging and charging were conducted through the CaCl<sub>2</sub> hydration reaction. A silicon carbide honeycomb was adopted to improve heat transfer in the CaCl<sub>2</sub> packed bed. The heat storage, condenser, and evaporator temperature were set at 150<span style="white-space:nowrap;">°</span>C, 30<span style="white-space:nowrap;">°</span>C and 90<span style="white-space:nowrap;">°</span>C respectively. Repeated trials and experiments are time consuming for optimizing design of the equipment. Therefore, in this research, we constructed a simulation that can predict the performance of the device. A numerical simulation model was utilized in preparation for the design of the heat storage module. The consistency of both the simulation and the experimental results was confirmed by comparing them.展开更多
In order to effectively recover low and medium grade heat energy,a novel combined cooling and heating storage system based on zeolite-water is proposed in this paper.The system coupled the zeolite-water adsorption pro...In order to effectively recover low and medium grade heat energy,a novel combined cooling and heating storage system based on zeolite-water is proposed in this paper.The system coupled the zeolite-water adsorption process with the water evaporation refrigeration process during discharging process to realize generating cold energy and heat energy simultaneously.A more accurate kinetic model of zeolite and water adsorption is developed,and the thermodynamic performance of discharging process of the system is numerically analyzed.The results show the system has the higher energy conversion coefficient of 1.49 and the higher energy density of 1216.6 kJ/kg-zeolite.The change laws of system performances,such as energy generated,energy conversion coefficient and energy density,with key parameters during discharging process are revealed.The study provides a way for efficient utilization of low and medium grade heat energy.展开更多
Borehole thermal energy storage(BTES)systems have garnered significant attention owing to their efficacy in storing thermal energy for heating and cooling applications.Accurate modeling is paramount for ensuring the p...Borehole thermal energy storage(BTES)systems have garnered significant attention owing to their efficacy in storing thermal energy for heating and cooling applications.Accurate modeling is paramount for ensuring the precise design and operation of BTES systems.This study conducts a sensitivity analysis of BTES modeling by employing a comparative investigation of five distinct parameters on a wedge-shaped model,with implications extendable to a cylindrical configuration.The parameters examined included two design factors(well spacing and grout thermal conductivity),two operational variables(charging and discharging rates),and one geological attribute(soil thermal conductivity).Finite element simulations were carried out for the sensitivity analysis to evaluate the round-trip efficiency,both on a per-cycle basis and cumulatively over three years of operation,serving as performance metrics.The results showed varying degrees of sensitivity across different models to changes in these parameters.In particular,the round-trip efficiency exhibited a greater sensitivity to changes in spacing and volumetric flow rate.Furthermore,this study underscores the importance of considering the impact of the soil and grout-material thermal conductivities on the BTES-system performance over time.An optimized scenario is modelled and compared with the base case,over a comparative assessment based on a 10-year simulation.The analysis revealed that,at the end of the 10-year period,the optimized BTES model achieved a cycle efficiency of 83.4%.This sensitivity analysis provides valuable insights into the merits and constraints of diverse BTES modeling methodologies,aiding in the selection of appropriate modeling tools for BTES system design and operation.展开更多
本文在传统的复叠式空气源热泵中增加一个双螺旋盘管形式的蓄热器,并测量蓄热器内不同位置水温及蓄热器进出口制冷剂温度变化。研究了当室内侧模拟工况干球温度为22℃±0.1℃,相对湿度为50%±3%,室外侧模拟工况干球温度为-12℃&...本文在传统的复叠式空气源热泵中增加一个双螺旋盘管形式的蓄热器,并测量蓄热器内不同位置水温及蓄热器进出口制冷剂温度变化。研究了当室内侧模拟工况干球温度为22℃±0.1℃,相对湿度为50%±3%,室外侧模拟工况干球温度为-12℃±0.1℃时,蓄热器在蓄热模式、间断制热蓄能除霜模式、不间断制热蓄能除霜模式下的蓄放热特性。结果表明:该蓄热器有良好的蓄热能力及在不同低位热源条件下的放热能力。在间断和不间断制热蓄能除霜过程中,蓄热器的释热量分别为1 642.7 k J和1 892.4 k J,可以满足除霜的要求和部分室内供热需求。展开更多
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Chemical heat storage is a promising technology for improving thermal energy efficiency. In this study, CaCl<sub>2</sub> and H<sub>2</sub>O were selected as a reaction system for utilization of low-grade exhaust heat that is cooler than 200<span style="white-space:nowrap;"><span style="white-space:nowrap;">°</span></span>C. Heat discharging and charging were conducted through the CaCl<sub>2</sub> hydration reaction. A silicon carbide honeycomb was adopted to improve heat transfer in the CaCl<sub>2</sub> packed bed. The heat storage, condenser, and evaporator temperature were set at 150<span style="white-space:nowrap;">°</span>C, 30<span style="white-space:nowrap;">°</span>C and 90<span style="white-space:nowrap;">°</span>C respectively. Repeated trials and experiments are time consuming for optimizing design of the equipment. Therefore, in this research, we constructed a simulation that can predict the performance of the device. A numerical simulation model was utilized in preparation for the design of the heat storage module. The consistency of both the simulation and the experimental results was confirmed by comparing them.
基金This study is financially supported by National Key R&D Plan(Grant No.2017YFB0903605)the National Science Fund for Distinguished Young Scholars(Grant No.51925604)+2 种基金International Partnership Program,Bureau of International Cooperation of Chinese Academy of Sciences(Grant No.182211KYSB20170029)Transformational Technologies for Clean Energy and Demonstration,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21070302)Beijing Key Laboratory of Distributed Combined Cooling Heating and Power System.
文摘In order to effectively recover low and medium grade heat energy,a novel combined cooling and heating storage system based on zeolite-water is proposed in this paper.The system coupled the zeolite-water adsorption process with the water evaporation refrigeration process during discharging process to realize generating cold energy and heat energy simultaneously.A more accurate kinetic model of zeolite and water adsorption is developed,and the thermodynamic performance of discharging process of the system is numerically analyzed.The results show the system has the higher energy conversion coefficient of 1.49 and the higher energy density of 1216.6 kJ/kg-zeolite.The change laws of system performances,such as energy generated,energy conversion coefficient and energy density,with key parameters during discharging process are revealed.The study provides a way for efficient utilization of low and medium grade heat energy.
文摘Borehole thermal energy storage(BTES)systems have garnered significant attention owing to their efficacy in storing thermal energy for heating and cooling applications.Accurate modeling is paramount for ensuring the precise design and operation of BTES systems.This study conducts a sensitivity analysis of BTES modeling by employing a comparative investigation of five distinct parameters on a wedge-shaped model,with implications extendable to a cylindrical configuration.The parameters examined included two design factors(well spacing and grout thermal conductivity),two operational variables(charging and discharging rates),and one geological attribute(soil thermal conductivity).Finite element simulations were carried out for the sensitivity analysis to evaluate the round-trip efficiency,both on a per-cycle basis and cumulatively over three years of operation,serving as performance metrics.The results showed varying degrees of sensitivity across different models to changes in these parameters.In particular,the round-trip efficiency exhibited a greater sensitivity to changes in spacing and volumetric flow rate.Furthermore,this study underscores the importance of considering the impact of the soil and grout-material thermal conductivities on the BTES-system performance over time.An optimized scenario is modelled and compared with the base case,over a comparative assessment based on a 10-year simulation.The analysis revealed that,at the end of the 10-year period,the optimized BTES model achieved a cycle efficiency of 83.4%.This sensitivity analysis provides valuable insights into the merits and constraints of diverse BTES modeling methodologies,aiding in the selection of appropriate modeling tools for BTES system design and operation.
文摘本文在传统的复叠式空气源热泵中增加一个双螺旋盘管形式的蓄热器,并测量蓄热器内不同位置水温及蓄热器进出口制冷剂温度变化。研究了当室内侧模拟工况干球温度为22℃±0.1℃,相对湿度为50%±3%,室外侧模拟工况干球温度为-12℃±0.1℃时,蓄热器在蓄热模式、间断制热蓄能除霜模式、不间断制热蓄能除霜模式下的蓄放热特性。结果表明:该蓄热器有良好的蓄热能力及在不同低位热源条件下的放热能力。在间断和不间断制热蓄能除霜过程中,蓄热器的释热量分别为1 642.7 k J和1 892.4 k J,可以满足除霜的要求和部分室内供热需求。
