CHF characteristics of downward flow are quite different from that of upward flow due to complicated two-phase flow structure caused by the influence of buoyancy. In this investigation, CHF experiment was carried out on the forced convective boiling system with a
stainless steel tube of 15 mm in inner diameter and 400 mm in heating length. As the experimental results on the basis of the axial location of CHF occurrence, the inlet fluid temperature and the pressure drop of test section, CHF could be classified into three modes i.e., the dryout of falling liquid film at high quality condition, the CHF due to flooding at low quality condition and the CHF caused by the instability of two-phase flow structure at near subcooled condition.