OPERATING LIMIT OF A CLOSED TWO-PHASE THERMOSYPHON WITH A BINARY MIXTURE
Operating limit of closed two-phase thermosyphons was experimentally investigated with a mixture of ethanol and water as a working fluid. Even if the heat input was less than the maximum value, two kinds of oscillations of the system pressure p and temperatures of both the heating and cooling walls and fluid were observed; i.e., (1) all the temperatures oscillated in phase with p (oscillation I), and (2) the heating wall temperature at the wall of the liquid pool region oscillated out of phase with p (oscillation II). These oscillations, which did not appear in the case of the pure working fluid, were considered to occur due to the intermittent violent boiling of the pool of the binary liquid in the heating section. At the onset of the operating limit five types of the patterns of the increase in temperatures and p were found. In the three cases of them, dryout of the heating wall in the liquid pool was triggered by the violent oscillation II, which was the unique feature in the case of binary working fluid.