Measurement of Subcooled Boiling Pressure Drop and Local Heat Transfer Coefficient in Horizontal Channels Under LPLF Conditions

Abstract

Horizontal flow is commonly encountered in boiler tubes, refrigerating equipments and nuclear reactor fuel channels of pressurized heavy water reactors (PHWR). Study of horizontal flow under low pressure and low flow (LPLF) conditions is important in understanding the nuclear core behavior during situations like LOCA (Loss of coolant accidents). In the present work, experimental measurements of local heat transfer coefficient and pressure drop are carried out in a horizontal channel under LPLF conditions of sub-cooled boiling. Infrared thermography is used for the measurement of local wall temperature to estimate the heat transfer coefficient in single phase and two phase flows with water as the working medium at atmospheric pressure. Correlation for single phase diabatic pressure drop ratio (diabatic to adiabatic) as a function of viscosity ratio (wall temperature to fluid temperature) is presented. Correlation for pressure drop under sub-cooled boiling conditions as a function of Bo (Boiling number) and Ja (Jacob number) is obtained. Correlation for single phase heat transfer coefficient in the developing region is presented as a function of z/d (ratio of axial length of the test section to diameter). Correlation for two-phase heat transfer coefficient under sub-cooled boiling condition is presented as a function of Bo, Ja and Pr (Prandtl number). Correlation between heat transfer coefficient and friction factor is obtained by applying Reynolds analogy.