[en] Characteristics of one-component critical two-phase flow through a capillary tube are investigated. It is experimentally shown that three kinds of flow patterns exist, which are called steady flow, periodic flow and unsteady flow, and the critical flow rate varies with the flow pattern for the same inlet condition. The dependencies of inlet subcooling and wall heat flux on the critical flow rate are experimentally investigated for the steady and periodic flow patterns. By considering void fraction and velocity distributions in a cross section of the pipe, the critical flow rate are analized for different thermal conditions of the wall and compared with the experimental results. It is clarified that the critical flow rate is controlled by the heat transfer of liquid to bubbles and the position of nucreation site of boiling. (author)