在第三类边界条件下，管内强制对流换热实验装置相对较为简单。由于实验避免了对管壁多点温度的直接测量，使实验相对简化。但在实验数据处理时，需利用已有的管外传热实验结果，即外部的传热条件必须是能够计算得到的。此外，本实验结果用于各类管状换热器的设计计算时，管外的介质温度往往是已知的，所以利于推广。 In the third type of boundary conditions, the tube forced convection heat transfer experimental device is relatively simple. As the experiment avoids the direct measurement of the tube wall temperature, the experiment is relatively simplified. However, in the experimental data processing, it is necessary to use the existing experimental results of heat transfer outside the tube, that is, the external heat transfer conditions must be able to be calculated. In addition, the experimental results for the design and calculation of various types of tubular heat exchanger, the media temperature outside the tube is often known, it is conducive to the promotion.