EXPERIMENTAL STUDY OF NATURAL CONVECTION IN HORIZONTAL AND VERTICAL CYLINDRICAL PIPE WITH DIFFERENT END TEMPERATURES (EFFECTS OF PIPING GEOMETRY AND TEMPERATURE)

摘要

Visualization of natural convection and measurement of temperature of water in horizontal and vertical cylindrical pipe with different end temperatures were carried out. For horizontal system, there exist hot and cold layers in upper and lower region of the horizontal pipe and further intermediate temperature layer exist between hot and cold layers. For vertical system, flow pattern is too much different from that of horizontal system. Cellular convection appears with a pitch of about 1D of the pipe in the vertical pipe. The fluid flow in a cellular convection is random, i.e. there existing upward flow and downward flow, and those flowing paths vary at random. Heat transportation with natural convection is larger than that with conduction. The equivalent thermal conductivity of natural convection is about 1000 times larger than that of water. Further, high temperature experiment was also carried out. In this experiment, the temperature distribution over the horizontal pipe was measured. The evaluation method of temperature over a pipe was developed, and it can temperature distribution over pipe precisely.