Thermal characteristics and nozzle structural optimization of gelled waxy crude oil subjected to jet heating

Jet heating is a widely employed technique for waxy crude oil storage tanks. To enhance heating efficiency and promote efficient gel-sol transition of gelled crude oil, this study optimizes jet heater nozzle structures, taking a 1000 m 3 floating roof crude oil tank as the research object. First, wide-temperature-range mathematical characterization of waxy crude oil's physical property changes during gel-sol transition is conducted. Then, the finite volume method is adopted to numerically simulate the heat transfer, flow behavior and phase transition during jet heating with four nozzle structures (conical, baffle-type, double-head, multi-orifice) under uniform and non-uniform initial temperature fields. Results indicate that the high-speed low-temperature jet outperforms high-temperature low-speed condition, with the double-head nozzle achieving the highest in-tank average temperature rise rate of 0.97 °C/h. Under non-uniform initial field (initial gelled oil 15.2 m 3 , 2.7% of tank volume), the baffle-type nozzle reaches 86.1% gelled oil melting rate within 30 s, the fastest among all nozzles. In terms of energy efficiency and low-carbon performance, however, the double-head nozzle presents the highest heating efficiency (89.8%) and the lowest carbon emission per unit effective temperature rise (110.88 kg/°C).Comprehensive evaluation indicates that the double-head nozzle is the optimal scheme, realizing uniform tank heating while reducing operation energy consumption and carbon emissions.