ABSTRACT
Two-phase heat transfer is an important aspect of power plant design. Sometimes two-phase heat transfer is also referred to as boiling heat transfer. Two-phase flow has much greater convective heat transfer coefficients than single-phase flow, and boiling heat transfer coefficients are two to ten times higher than the single-phase heat transfer coefficients for the same mass flow rate. Boiling heat transfer coefficients are sensitive to the temperature difference between the surface of the fuel rods and the coolant. Flat plates have different expressions for the convective heat transfer coefficient than vertical plates, and cylindrical surfaces have different expressions for the convective heat transfer coefficient than flat surfaces do. The heat transfer coefficients increase until the critical heat flux point or departure from nucleate boiling point is reached. The behavior of the heat transfer coefficient during flow boiling is entirely different for nucleate boiling that it is for bulk boiling.
