An experimental investigation was conducted to examine the effects of nozzle geometry and exit Reynolds number (600≤Re≤1200) on the spatiotemporal evolution of temperature fields in submerged thermal jets. The study employed a three-dimensional laser-induced fluorescence (3D-LIF) system integrating two-color simultaneous imaging and planar laser scanning modules. Measurements were performed on circular and elliptical nozzles with a contraction ratio of 3.19 and equivalent exit diameter of 7mm. High-precision scanning captured planar temperature field distributions at five cross-sections spaced 3mm apart within one cycle, enabling three-dimensional reconstruction of transient temperature fields with a spatial domain of 90×90×12mm and temporal resolution of 8Hz.Results demonstrate that nozzle geometry significantly influences temperature field characteristics: elliptical jets exhibit axis-asymmetric diffusion while circular jets maintain isotropic spreading. The elliptical nozzles induce more intensive fluid mixing than circular nozzles, with geometric variations accelerating heat dissipation. Increasing Reynolds number enhances turbulent mixing while simultaneously suppressing thermal buoyancy, leading to accelerated temperature decay in the central high-temperature region and increased fragmentation of thermal structures. These phenomena provide critical guidance for optimizing thermal management systems via geometric manipulation of nozzle profiles.

3D-LIF, Submerged thermal jets, Temperature field characteristics