摘要
为寻求适应乌鲁木齐地区太阳能资源实际情况的最优蓄热水箱结构并确定不同时段的最佳运行工况,该研究对25种不同工况下太阳能蓄热水箱内的流动与传热过程进行数值分析。结果表明:球顶结构的水箱热分层效果最好,平顶结构的水箱热分层效果最差。在11:30、13:00、15:00、16:20和18:00,冷水入口流速0.42、0.42、0.1、0.18和0.26 m/s时,球顶结构的蓄热水箱无量纲[火用]值最小,分别为0.879、0.873、0.879、0.881和0.874,水箱的热分层效果最好。以蓄热水箱的瞬时换热效率作为评价指标,对考察的5个时刻,球顶结构的水箱的瞬时换热效率均在冷水入口流速0.1 m/s时达到最大值,蓄热效率最高。如果只采用蓄热水箱供暖,水箱的冷水入口流速下限值为0.26 m/s;对于冷水入口流速低于0.26 m/s的工况,可采用水箱并联或者水箱与电加热锅炉联合运行模式。研究结果可为不同气候条件下太阳能热水利用系统的优化运行提供参考。
Thermal storage performance is the key to improve the overall efficiency of solar hot water utilization systems.In order to find the optimal structure of solar water storage tank to adapt to the actual situation of solar energy resources in Urumqi,and to determine the optimal operating conditions in different periods of time,the flow and heat transfer processes in solar water storage tank under 25 different working conditions were numerically analyzed by standard k-ε model in this paper.The results showed that the thermal stratification effect of the solar water storage tank with the flat roof was the worst one,the dimensionless exergy was 0.903,the solar water storage tank with the spherical foof was the best and the dimensionless exergy was 0.881.The solar water storage tank with flat roof had the highest instantaneous heat transfer efficiency and its value was 0.899,while the solar water storage tank with the spherical roof had the lowest value 0.855.At 11:30,13:00,15:00,16:20 and 18:00,the solar water storage tank with spherical roof could obtain the optimal thermal stratification effect when the cold water inlet velocity were 0.42,0.42,0.1,0.18 and 0.26 m/s,respectively.The minimum dimensionless exergy for the five times were 0.879,0.873,0.879,0.881and 0.874,respectively.For the five studied times,however,the solar water storage tank with spherical roof had the maximum instantaneous heat transfer efficiency when the cold water inlet flow velocity was 0.10 m/s.And the maximum instantaneous heat transfer efficiency for the five times were 0.864,0.852,0.864,0.865 and 0.862,respectively.If the solar water storage tank was used for heating,the lower limit of cold water inlet velocity of the tank was 0.26 m/s.When the inlet velocity of cold water was under 0.26 m/s,the parallel operation mode of water tank or combined operation mode of water tank and electric heating boiler should be adopted.This study can provide reference for the operation optimization of solar energy storage system in different climate conditions.
作者
王烨
何腾
赵皓辰
孙振东
石成志
Wang Ye;He Teng;Zhao Haochen;Sun zhendong;Shi Chengzhi(School of Environmental and Municipal Engineering,Lanzhou Jiaotong University,Lanzhou 730070,China;Key Laboratory of Railway Vehicle Thermal Engineering,Ministry of Education,Lanzhou Jiaotong University,Lanzhou 730070,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2020年第7期225-231,共7页
Transactions of the Chinese Society of Agricultural Engineering
基金
国家自然科学基金项目(51476073,51266004)
甘肃省建设科技攻关项目(KJ2016-2)。
关键词
太阳能
数值模拟
优化
蓄热水箱
运行工况
无量纲[火用]
瞬时换热效率
solar energy
numerical simulation
optimization
hot water storage tank
operation conditions
dimensionless exergy
instantaneous heat transfer efficiency