Phase change microcapsules can carry large amounts of heat and be dispersed into other mediums either as a solid composite or as slurry fluids without changes to their appearance or fluidity. These two standout featur...Phase change microcapsules can carry large amounts of heat and be dispersed into other mediums either as a solid composite or as slurry fluids without changes to their appearance or fluidity. These two standout features make phase change microcapsules ideal for use in thermal energy applications to enhance the efficiency of energy utilisation. This review paper includes methods used for the encapsulation of phase change materials, especially the method suitable for large scale productions, the trends of phase change microcapsule development and their use in thermal energy applications in static and dynamic conditions. The effect of phase change microcapsules on convective heat transfer through addition to thermal fluids as slurries is critically reviewed. The review highlighted that so far the phase change microcapsules used mainly have polymeric shells, which has very low thermal conductivities. Their enhancement in convective heat transfer was demonstrated in locations where the phase change material experiences phase change. The phase change results in the slurries having higher apparent local specific heat capacities and thus higher local heat transfer coefficients. Out of the phase change region, no enhancement is observed from the solid microcapsule particles due to the low specific heat capacity and thermal conductivity of the phase change microcapsules compared to that of water, which is normally used as slurry media in the test. To further the research in this area, phase change microcapsules with higher specific heat capacity, higher thermal conductivity and better shape stability need to be applied.展开更多
该文以盐城国家级珍禽自然保护区核心区为案例区,以1983—2021年12期遥感影像为数据源,将景观生态学方法和GIS技术相结合,探究研究区互花米草时空轨迹及其对景观格局的影响,结果如下:①1983—2021年,互花米草扩张明显,面积增加了12.365...该文以盐城国家级珍禽自然保护区核心区为案例区,以1983—2021年12期遥感影像为数据源,将景观生态学方法和GIS技术相结合,探究研究区互花米草时空轨迹及其对景观格局的影响,结果如下:①1983—2021年,互花米草扩张明显,面积增加了12.365倍;依次经历了初始扩张阶段、加速增长阶段、停滞增长阶段,即将进入治理消除阶段;互花米草面积与时间线性关系显著。②互花米草时空轨迹呈现3组团特征,1983年、1988年、1992年和1997年为西部组团,以向东南方向移动为主;2000年、2002年、2006年和2009年为东部组团,以向东北方向移动为主,这2个组团都表现出向海的趋势;2011年、2014年、2017年和2021年为中部组团,方向上虽表现出无序性,但有明显向陆的趋势。③互花米草扩张对区域景观结构变化的累积贡献率为43.352%,与互花米草面积扩张阶段一致,又表现出“低→高→低”的3个阶段。互花米草面积与区域景观格局指数显著相关;互花米草景观格局与区域景观格局相关明显,类型尺度的最大斑块指数(largest patch index,LPI)、总边缘长度(total edge,TE)、边缘密度(edge density,ED)、面积加权平均分维度(fractal dimension index of area-weighted mean,FRAC_AM)与区域景观格局指数在0.01水平下显著相关;互花米草面积与栖息地生境质量呈显著负相关。结果表明,互花米草扩张对景观格局与功能影响深刻,互花米草治理必须因地制宜。展开更多
文摘Phase change microcapsules can carry large amounts of heat and be dispersed into other mediums either as a solid composite or as slurry fluids without changes to their appearance or fluidity. These two standout features make phase change microcapsules ideal for use in thermal energy applications to enhance the efficiency of energy utilisation. This review paper includes methods used for the encapsulation of phase change materials, especially the method suitable for large scale productions, the trends of phase change microcapsule development and their use in thermal energy applications in static and dynamic conditions. The effect of phase change microcapsules on convective heat transfer through addition to thermal fluids as slurries is critically reviewed. The review highlighted that so far the phase change microcapsules used mainly have polymeric shells, which has very low thermal conductivities. Their enhancement in convective heat transfer was demonstrated in locations where the phase change material experiences phase change. The phase change results in the slurries having higher apparent local specific heat capacities and thus higher local heat transfer coefficients. Out of the phase change region, no enhancement is observed from the solid microcapsule particles due to the low specific heat capacity and thermal conductivity of the phase change microcapsules compared to that of water, which is normally used as slurry media in the test. To further the research in this area, phase change microcapsules with higher specific heat capacity, higher thermal conductivity and better shape stability need to be applied.
文摘该文以盐城国家级珍禽自然保护区核心区为案例区,以1983—2021年12期遥感影像为数据源,将景观生态学方法和GIS技术相结合,探究研究区互花米草时空轨迹及其对景观格局的影响,结果如下:①1983—2021年,互花米草扩张明显,面积增加了12.365倍;依次经历了初始扩张阶段、加速增长阶段、停滞增长阶段,即将进入治理消除阶段;互花米草面积与时间线性关系显著。②互花米草时空轨迹呈现3组团特征,1983年、1988年、1992年和1997年为西部组团,以向东南方向移动为主;2000年、2002年、2006年和2009年为东部组团,以向东北方向移动为主,这2个组团都表现出向海的趋势;2011年、2014年、2017年和2021年为中部组团,方向上虽表现出无序性,但有明显向陆的趋势。③互花米草扩张对区域景观结构变化的累积贡献率为43.352%,与互花米草面积扩张阶段一致,又表现出“低→高→低”的3个阶段。互花米草面积与区域景观格局指数显著相关;互花米草景观格局与区域景观格局相关明显,类型尺度的最大斑块指数(largest patch index,LPI)、总边缘长度(total edge,TE)、边缘密度(edge density,ED)、面积加权平均分维度(fractal dimension index of area-weighted mean,FRAC_AM)与区域景观格局指数在0.01水平下显著相关;互花米草面积与栖息地生境质量呈显著负相关。结果表明,互花米草扩张对景观格局与功能影响深刻,互花米草治理必须因地制宜。
