换热器怎么算Nu和h以及摩擦阻力f

<img style="font-family:宋体, SimSun;font-size:14px;vertical-align: middle; margin-right: 2px;" src="http://www.jishulink.com/platform/static/ueditor/dialogs/attachment/fileTypeImages/icon_pdf.gif"/><a style="font-family:宋体, SimSun;font-size:14px; color:#0066cc;" href="http://oss.jishulink.com/upload/201608/1470276175780_璧面摩擦系数.pdf" title="璧面摩擦系数.pdf">璧面摩擦系数.pdf</a>以及参阅此篇博文：<a href="http://liusuanyatong.blog.163.com/blog/static/215595157201602002452913/" _src="http://liusuanyatong.blog.163.com/blog/static/215595157201602002452913/">http://liusuanyatong.blog.163.com/blog/static/215595157201602002452913/</a> 希望对楼主有所帮助