Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD mod...Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercdtical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers CA, B, C D, E, F and G）, which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water （SCW） to evaluate the uniformity of the velocity dis- tribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-ram inlet pipe diameter.展开更多
The influence of shallow groundwater on the diurnal heat transport of the soil profile was analyzed using a soil sensor automatic monitoring system that continu- ously measures temperature and water content of soil pr...The influence of shallow groundwater on the diurnal heat transport of the soil profile was analyzed using a soil sensor automatic monitoring system that continu- ously measures temperature and water content of soil profiles to simulate heat transport based on the Philip and de Vries （PDV） model. Three experiments were conducted to measure soil properties at depths of 5 cm, 10 cm, 20 cm, and 30 cm when groundwater tables reached l0 cm, 30 cm, and 60 cm （Experiments I, II, and III）. Results show that both the soil temperature near shallow groundwater and the soil water content were effectively simulated by the PDV model. The root mean square errors of the temperature at depths of 5 cm, 10 cm, and 20 cm were 1.018℃, 0.909℃, and 0.255℃, respectively. The total heat flux generated the convergent and divergent planes in space-time fields with valley values of-161.5 W-m 2 at 7：30 and -234.6 W.m2 at 11：10 in Experiments II and III, respectively. The diurnal heat transport of the saturated soil occurred in five stages, while that of saturated-unsaturated and unsaturated soil profiles occurred in four stages because high moisture content led to high thermal conductivity, which hastened the heat transport.展开更多
藏东南地区的雅鲁藏布大峡谷地区(以下简称大峡谷地区)是印度洋暖湿气流输送至青藏高原的重要通道,在高原水分与能量循环过程中具有重要地位。为了揭示不同水汽输送对陆-气间水热交换通量的影响,本文利用欧洲中期天气预报中心第五代再...藏东南地区的雅鲁藏布大峡谷地区(以下简称大峡谷地区)是印度洋暖湿气流输送至青藏高原的重要通道,在高原水分与能量循环过程中具有重要地位。为了揭示不同水汽输送对陆-气间水热交换通量的影响,本文利用欧洲中期天气预报中心第五代再分析数据产品,根据大气中总水汽含量和水汽水平输送通量将大峡谷地区2013年5月20日至7月9日的水汽强度划分为强/弱/极弱三种级别。并利用第五代公用陆面模式(Community Land Model version 5.0,CLM5.0)模拟了水汽输送对大峡谷-大气间水热交换的影响。研究表明:大峡谷地区的南(东)边界为水汽主要的输入(输出)边界,大峡谷南侧河谷存在水汽强输送带。CLM5.0模拟的大峡谷-大气间水热交换通量与实际相比误差较大,通过优选热力学粗糙度参数化方案和土壤属性替代数据集,提高了CLM5.0模拟大峡谷-大气间水热交换通量的精度。其中Zeng and Dickinson(1998)的方案(以下简称Z98方案)效果最优,较CLM5.0默认参数化方案下模拟的小麦站和草地站近地面感热通量均方根误差分别下降18.2%和10.9%。区域模拟结果显示:大峡谷地区近地面潜热通量区域模拟总体分布为东南高而西北低,近地面感热通量则相反,随水汽水平输送强度的减弱,潜热通量大值区向西北延伸面增大,而感热通量大值区则向东南延伸面增大。冰雪覆盖的高海拔地区近地面感热通量维持低值,而潜热通量则相反。整个试验阶段,大峡谷地区降水时长达59%,不同水汽输送条件下近地面有效能量主要以潜热的方式向大气输送,其中在强水汽水平输送条件下的水汽强输送带的近地面感热输送最弱,Z98方案下的感热通量日均值仅为-1.80 W·m^(-2),潜热通量则大于70.0 W·m^(-2)。对于大峡谷地区,当水汽维持高值范围时,近地面净辐射降低,但近地面净辐射主要被潜热消化,水汽保温大气的效应使得地-气温差降低,近地面感热输送抑制显著。本研究结果对认识雅鲁藏布大峡谷地区陆面过程及其对水汽水平输送的响应有一定的参考价值。展开更多
基金Supported by the National Basic Research Program of China(2014CB745100)the National Natural Science Foundation of China(21576197)+1 种基金Tianjin Research Program of Application Foundation and Advanced Technology(14JCQNJC06700)Tianjin Penglai 19-3 Oil Spill Accident Compensation Project(19-3 BC2014-03)
文摘Heat exchangers play an important role in supercritical water coal gasification systems for heating feed and cooling products. However, serious deposition and plugging problems always exist in heat exchangers. CFD modeling was used to simulate the transport characteristics of solid particles in supercdtical water through the shell and tube of heat exchangers to alleviate the problems. In this paper, we discuss seven types of exchangers CA, B, C D, E, F and G）, which vary in inlet nozzle configuration, header height, inlet pipe diameter and tube pass distribution. In the modeling, the possibility of deposition in the header was evaluated by accumulated mass of particles; we used the velocity contour of supercritical water （SCW） to evaluate the uniformity of the velocity dis- tribution among the tube passes. Simulation results indicated that the optimum heat exchanger had structure F, which had a rectangular configuration of tube pass distractions, a bottom inlet, a 200-mm header height and a 10-ram inlet pipe diameter.
文摘The influence of shallow groundwater on the diurnal heat transport of the soil profile was analyzed using a soil sensor automatic monitoring system that continu- ously measures temperature and water content of soil profiles to simulate heat transport based on the Philip and de Vries （PDV） model. Three experiments were conducted to measure soil properties at depths of 5 cm, 10 cm, 20 cm, and 30 cm when groundwater tables reached l0 cm, 30 cm, and 60 cm （Experiments I, II, and III）. Results show that both the soil temperature near shallow groundwater and the soil water content were effectively simulated by the PDV model. The root mean square errors of the temperature at depths of 5 cm, 10 cm, and 20 cm were 1.018℃, 0.909℃, and 0.255℃, respectively. The total heat flux generated the convergent and divergent planes in space-time fields with valley values of-161.5 W-m 2 at 7：30 and -234.6 W.m2 at 11：10 in Experiments II and III, respectively. The diurnal heat transport of the saturated soil occurred in five stages, while that of saturated-unsaturated and unsaturated soil profiles occurred in four stages because high moisture content led to high thermal conductivity, which hastened the heat transport.
文摘藏东南地区的雅鲁藏布大峡谷地区(以下简称大峡谷地区)是印度洋暖湿气流输送至青藏高原的重要通道,在高原水分与能量循环过程中具有重要地位。为了揭示不同水汽输送对陆-气间水热交换通量的影响,本文利用欧洲中期天气预报中心第五代再分析数据产品,根据大气中总水汽含量和水汽水平输送通量将大峡谷地区2013年5月20日至7月9日的水汽强度划分为强/弱/极弱三种级别。并利用第五代公用陆面模式(Community Land Model version 5.0,CLM5.0)模拟了水汽输送对大峡谷-大气间水热交换的影响。研究表明:大峡谷地区的南(东)边界为水汽主要的输入(输出)边界,大峡谷南侧河谷存在水汽强输送带。CLM5.0模拟的大峡谷-大气间水热交换通量与实际相比误差较大,通过优选热力学粗糙度参数化方案和土壤属性替代数据集,提高了CLM5.0模拟大峡谷-大气间水热交换通量的精度。其中Zeng and Dickinson(1998)的方案(以下简称Z98方案)效果最优,较CLM5.0默认参数化方案下模拟的小麦站和草地站近地面感热通量均方根误差分别下降18.2%和10.9%。区域模拟结果显示:大峡谷地区近地面潜热通量区域模拟总体分布为东南高而西北低,近地面感热通量则相反,随水汽水平输送强度的减弱,潜热通量大值区向西北延伸面增大,而感热通量大值区则向东南延伸面增大。冰雪覆盖的高海拔地区近地面感热通量维持低值,而潜热通量则相反。整个试验阶段,大峡谷地区降水时长达59%,不同水汽输送条件下近地面有效能量主要以潜热的方式向大气输送,其中在强水汽水平输送条件下的水汽强输送带的近地面感热输送最弱,Z98方案下的感热通量日均值仅为-1.80 W·m^(-2),潜热通量则大于70.0 W·m^(-2)。对于大峡谷地区,当水汽维持高值范围时,近地面净辐射降低,但近地面净辐射主要被潜热消化,水汽保温大气的效应使得地-气温差降低,近地面感热输送抑制显著。本研究结果对认识雅鲁藏布大峡谷地区陆面过程及其对水汽水平输送的响应有一定的参考价值。
