Natural air circulation in an open circuit

The paper presents experimental data on the formation of natural air circulation in an open circuit with the length of 22.4 m and a pipe diameter of 120 mm, which is located in a room connected to the atmosphere, in a case of the emergency cooldown of a lead-cooled reactor. Natural circulation without heating was ensured by the difference between room and atmospheric temperatures, while the air heated to the temperature of 170–470 °C by the electric heater with a power of 7–12 kW circulated due to the reduction in its density at the outlet. A model is proposed for calculating the pressure of natural circulation using generalized experimental data obtained in an open-air circuit under the conditions of a quasi-stationary flow, temperature, and static pressure. The generalization error does not exceed 30% with a total error of 20%. Hydraulic losses in the circuit and heat losses through the circuit insulation were determined. Atmospheric turbulence is demonstrated to cause pressure pulsations in the circuit with an amplitude close to the flow velocity head of 8.5–20 Pa in the duct. When the atmospheric air pressure at the inlet to the circuit exceeds that at the outlet, the amplitude increases to 280 Pa.