Model for condensation heat transfer inside horizontal tubes

摘要

A model for calculation of condensation heat transfer coefficients inside horizontal tubes was developed. The analysis takes into account the effects of the gravity force acting upon the condensate, the interfacial shear on the condensate film, saturation temperature level, the development of the stratified angle associated with the accumulated condensate layer at the bottom of the tube and the entrainment rate in two-phase flow. The influence of these parameters is evaluated with respect to the condensate film heat transfer inside horizontal tube performance both for the laminar and for the turbulent flow range of operating conditions of water - vapor flow. A theoretical predictive method is developed to obtain the local heat transfer coefficients along the tube length. The developed model was implemented in the thermohydraulic system code ATHLET to improve the modeling precision by ATHLET of the condensation processes performed in the heater tubes of VVER's horizontal steam generators in the case of a typical postulated small break loss of coolant accident. The ATHLET code model was applied in the analysis of loss of coolant accidents in pressurized water reactors at a single effect test facility.