Intermittent heat transportation by discharge of accumulated vapor

A heat transporting cycle already proposed by the authors was composed of the following processes: (A) accumulation of high-pressure vapor in an evaporator vessel, (B) discharge of the accumulated vapor from the evaporator followed by the condensation of a part of the vapor in the downstream condenser and the returning vapor–liquid two-phase flow from the condenser toward the evaporator, (C) return of the liquid to the evaporator after stopping of the flow through a check valve. In the present study, the flow and heat transport performances of a downward heat transport closed loop utilizing the above-mentioned cycle was investigated experimentally by using a setup of 3 and 5 m in height. The inner tube diameter was 10 mm. In the riser tube, high-speed upward two-phase flow with disturbance waves appeared. Experimental flow conditions and pressure drop for this annular flow were compared with the correlations of Fukano and Lockhart–Martinelli. In some cases the operation ceased due to the blockage of this two-phase flow by the tall condensate liquid column formed in the riser. A precise investigation showed that the vapor generation by flash evaporation in the evaporator during the period (B) played a very important role in avoiding this blockage effect.