In this study, two types of water flow, turbulent single-phase flow and low-pressure subcooled boiling flow, in straight and curved horizontal annuli are investigated numerically. The control volume technique is used for discretizing governing equations, the SIMPLEC algorithm for pressure-velocity coupling, and the shear stress transport k-ω model for turbulent flow. A three-dimensional two-fluid model is used for the subcooled boiling flow, the results of which are compared with those of the single-phase flow. The available water boiling experiment results at low pressure are used to validate the numerical results and were found to have good agreement. The inner cylinder surface temperature of the curved annulus in almost all angles is less than that of the straight annulus in both single-phase and subcooled boiling flow. The maxmum and minimum temperatures in the curved annulus occur at defferent points compared to straight annulus ones due to effects of the centrifugal force.
