Development and feasibility demonstration of a capacitance-based sensor for liquid film thickness measurement on a heated rod surface under falling-film conditions

• A capacitance-based sensor measures the liquid film thickness on a heated heater rod surface. • The sensor enables non-intrusive, multipoint film measurement in complex high-temperature, high-pressure rod bundles. • Experimental validation shows consistency with laser focus displacement meter data. • The sensor accurately measures liquid film thickness on both heated and unheated rods. • Findings expand multidimensional measurement options in simulated nuclear fuel assemblies and thermal-hydraulic tests.