Heat transfer and flow behaviors in three-dimensional circular tubes with loose-fit multiple channel twisted tapes were numerically studied. The investigation was examined for Reynolds numbers （Re） ranging from 5000...Heat transfer and flow behaviors in three-dimensional circular tubes with loose-fit multiple channel twisted tapes were numerically studied. The investigation was examined for Reynolds numbers （Re） ranging from 5000 to 15,000, by using air as testing fluid. Effects of the multiple channel number （N = 2, 3, and 4）, clearance ratio （CR = 0.0, 0.025, 0.05, and 0.075） on heat transfer enhancement and flow friction were examined. The numerical results indicate that the tubes with loose-fit multiple channel twisted tapes perform higher heat transfer rates than the plain tube. The enhanced heat transfer rate is escorted with larger pressure drop. Both heat transfer and pressure drop increase with increasing multiple channel number （N） and decreasing clearance ratio （CR）. Heat transfer augmented by the loose-fit multiple channel twisted tape with N = 4 is higher than those enhanced by the ones with N = 2 and 3 by around 9.5-17.8% and 5.8-7.8%, respectively. In addition, the loose-fit multiple channel twisted tapes with clearance ratio of 0.025, 0.05, and 0.075 give lower heat transfer rates than the one with CR = 0.0 by around 8.4%, 17.5%, and 28.8%, respectively.展开更多
下一代数字用户线(NG-DSL,Next Generation Digital Subscriber Line)技术使用高载波数与高正交振幅的OFDM调制方式,这对信号同步提出了更高的要求.提出了一种新的基于数据辅助型的符号定时算法——基于最小能量差的符号定时同步算法....下一代数字用户线(NG-DSL,Next Generation Digital Subscriber Line)技术使用高载波数与高正交振幅的OFDM调制方式,这对信号同步提出了更高的要求.提出了一种新的基于数据辅助型的符号定时算法——基于最小能量差的符号定时同步算法.该算法通过变步长搜索的方法,利用较少的步骤准确快速搜索到最小值,大大降低算法复杂度,最后对算法进行综合性能比较,仿真结果表明,新算法具有复杂度低,在NG-DSL环境下定时准确并且具有抗双绞线信道拖尾干扰能力强的特点,这些特点能够较好地满足NG-DSL对于符号定时同步算法的要求.展开更多
文摘Heat transfer and flow behaviors in three-dimensional circular tubes with loose-fit multiple channel twisted tapes were numerically studied. The investigation was examined for Reynolds numbers （Re） ranging from 5000 to 15,000, by using air as testing fluid. Effects of the multiple channel number （N = 2, 3, and 4）, clearance ratio （CR = 0.0, 0.025, 0.05, and 0.075） on heat transfer enhancement and flow friction were examined. The numerical results indicate that the tubes with loose-fit multiple channel twisted tapes perform higher heat transfer rates than the plain tube. The enhanced heat transfer rate is escorted with larger pressure drop. Both heat transfer and pressure drop increase with increasing multiple channel number （N） and decreasing clearance ratio （CR）. Heat transfer augmented by the loose-fit multiple channel twisted tape with N = 4 is higher than those enhanced by the ones with N = 2 and 3 by around 9.5-17.8% and 5.8-7.8%, respectively. In addition, the loose-fit multiple channel twisted tapes with clearance ratio of 0.025, 0.05, and 0.075 give lower heat transfer rates than the one with CR = 0.0 by around 8.4%, 17.5%, and 28.8%, respectively.
文摘下一代数字用户线(NG-DSL,Next Generation Digital Subscriber Line)技术使用高载波数与高正交振幅的OFDM调制方式,这对信号同步提出了更高的要求.提出了一种新的基于数据辅助型的符号定时算法——基于最小能量差的符号定时同步算法.该算法通过变步长搜索的方法,利用较少的步骤准确快速搜索到最小值,大大降低算法复杂度,最后对算法进行综合性能比较,仿真结果表明,新算法具有复杂度低,在NG-DSL环境下定时准确并且具有抗双绞线信道拖尾干扰能力强的特点,这些特点能够较好地满足NG-DSL对于符号定时同步算法的要求.
