Some of the next generation of small modular reactors have been designed with helically coiled steam generators integrated into the reactor vessel to enhance natural circulation. According to the developers of TASS/SMR, a one-dimensional thermal hydraulic code written to model the Korean Atomic Energy Research Institute's SMART reactor, the Žukauskas correlation, a heat transfer correlation designed for banks of straight tubes in crossflow, accurately models the heat transfer into helical steam generator tubes. Data has been collected using the Oregon State University Multi-Application Small Light Water Reactor (MASLWR) Test Facility to test whether the Žukauskas correlation can accurately predict the helical steam generator heat transfer coefficients for a natural circulation driven reactor.
A one-dimensional, lumped parameter method was devised to use the limited instrumentation of the facility to calculate a temperature profile inside the tubes. From the calculated bulk fluid temperatures, wall temperatures were iteratively solved for and used to generate semi-local heat transfer coefficients. It was found that the instrumentation in the steam generator region of MASLWR Test Facility is too sparse to generate accurate heat transfer coefficients, but the calculated wall temperatures can be averaged over the length of the tubes to ind a good global wall temperature. This global wall temperature was used in a global analysis that found that the Žukauskas correlation works well when both systems are at high flow rates but becomes increasingly worse as the flow rates are lowered
