The heat transfer performance of the phase change materials used in free cooling and air conditioning applications is low,due to the poor thermal conductivity of the materials.The recent phenomenal advancement in nano...The heat transfer performance of the phase change materials used in free cooling and air conditioning applications is low,due to the poor thermal conductivity of the materials.The recent phenomenal advancement in nano technology provides an opportunity for an appreciable enhancement in the thermal conductivity of the phase change materials.In order to explore the possibilities of using nano technology for various applications,a detailed parametric study is carried out,to analyse the heat transfer enhancement potential with the thermal conductivity of the conventional phase change materials and nano enhanced phase change materials under various flow conditions of the heat transfer fluid.Initially,the theoretical equation,used to determine the time for outward cylindrical solidification of the phase change material,is validated with the experimental results.It is inferred from the parametric studies,that for paraffinic phase change materials with air as the heat transfer fluid,the first step should be to increase the heat transfer coefficient to the maximum extent,before making any attempt to increase the thermal conductivity of the phase change materials,with the addition of nano particles.When water is used as the phase change material,the addition of nano particles is recommended to achieve better heat transfer,when a liquid is used as the heat transfer fluid.展开更多
为解决伪随机二相编码雷达高度表回波信号在波形匹配滤波处理时存在的多普勒失配问题,在深入分析雷达高度表回波信号功率分布特征的基础上,提出了基于天底点的回波多普勒检测和补偿算法。该算法首先对回波中的脉间多普勒信息进行检测、...为解决伪随机二相编码雷达高度表回波信号在波形匹配滤波处理时存在的多普勒失配问题,在深入分析雷达高度表回波信号功率分布特征的基础上,提出了基于天底点的回波多普勒检测和补偿算法。该算法首先对回波中的脉间多普勒信息进行检测、精细估计和补偿,再对补偿后回波中的脉内多普勒信息进行检测和补偿,从而解决匹配滤波中多普勒失配问题。仿真和实验表明:当信噪比大于-6 d B时,该算法最大检测误差小于50 Hz,可有效对回波多普勒信息进行检测和补偿。展开更多
文摘The heat transfer performance of the phase change materials used in free cooling and air conditioning applications is low,due to the poor thermal conductivity of the materials.The recent phenomenal advancement in nano technology provides an opportunity for an appreciable enhancement in the thermal conductivity of the phase change materials.In order to explore the possibilities of using nano technology for various applications,a detailed parametric study is carried out,to analyse the heat transfer enhancement potential with the thermal conductivity of the conventional phase change materials and nano enhanced phase change materials under various flow conditions of the heat transfer fluid.Initially,the theoretical equation,used to determine the time for outward cylindrical solidification of the phase change material,is validated with the experimental results.It is inferred from the parametric studies,that for paraffinic phase change materials with air as the heat transfer fluid,the first step should be to increase the heat transfer coefficient to the maximum extent,before making any attempt to increase the thermal conductivity of the phase change materials,with the addition of nano particles.When water is used as the phase change material,the addition of nano particles is recommended to achieve better heat transfer,when a liquid is used as the heat transfer fluid.
文摘为解决伪随机二相编码雷达高度表回波信号在波形匹配滤波处理时存在的多普勒失配问题,在深入分析雷达高度表回波信号功率分布特征的基础上,提出了基于天底点的回波多普勒检测和补偿算法。该算法首先对回波中的脉间多普勒信息进行检测、精细估计和补偿,再对补偿后回波中的脉内多普勒信息进行检测和补偿,从而解决匹配滤波中多普勒失配问题。仿真和实验表明:当信噪比大于-6 d B时,该算法最大检测误差小于50 Hz,可有效对回波多普勒信息进行检测和补偿。
