Boiling heat transfer and dryout in helically coiled tubes under different pressure conditions

•Heat transfer characteristics and dryout for helically coiled tube are performed.•A boiling heat transfer tends to increase with a pressure increase.•Dryout occurs at high quality test conditions investigated.•Steiner–Taborek’s correlation is predicted well based on the experimental results.

A helically coiled once-through steam generator has been used widely during the past several decades for small nuclear power reactors. The heat transfer characteristics and dryout conditions are important to optimal design a helically coiled steam generator. Various experiments with the helically coiled tubes are performed to investigate the heat transfer characteristics and occurrence condition of a dryout. For the investigated experimental conditions, Steiner–Taborek’s correlation is predicted reasonably based on the experimental results. The pressure effect is important for the boiling heat transfer correlation. A boiling heat transfer tends to increase with a pressure increase. However, it is not affected by the pressure change at a low power and low mass flow rate. Dryout occurs at high quality test conditions investigated because a liquid film on the wall exists owing to a centrifugal force of the helical coil.