Thermohydraulic processes in a heat pipe with a central circulation insert at low pressure

Results are given of an experimental investigation of thermohydraulic processes occurring in a compact natural-circulation loop (heat pipe with a central circulation insert) at a low pressure of steam-water mixture, including low vacuum $p_{top} = 22$–176 kPa. Consideration is given to axial heat transfer in nonboiling water under conditions of bubbling mode of loop operation; to superheating of water, which rises up the adiabatic region, relative to the saturation temperature; and to true void fraction and hydrodynamic stability of natural circulation.