Multi-Factor Air–Sea Heat Exchange Study on the Thermal Discharge Diffusion at Coastal Nuclear Power Plants: Sensitivity and Contribution Analysis

Solar radiation, longwave radiation, sensible heat flux, and latent heat flux constitute the primary forms of air–sea heat exchange, serving as crucial computational parameters in numerical simulations of thermal discharge. This study investigates a coastal nuclear power plant and employs a modified Morris screening method to quantitatively assess the contribution rates of various air–sea heat exchange processes to the spatial distribution of temperature rise under different operating conditions. The results indicate that the influence of air–sea heat exchange processes on the thermal discharge envelope exhibits a nonlinear pattern. The individual parameter sensitivity of shortwave radiation, sensible heat flux and latent heat flux is higher in the low temperature rise region (∆T ≥ 1 °C) than in the high temperature rise region (∆T ≥ 4 °C), with the individual parameter sensitivities of longwave radiation and latent heat flux displaying distinct threshold effects. The dominant heat exchange mechanisms vary across temperature rise regions: longwave radiation predominates in the high temperature rise region (∆T ≥ 4 °C), contributing approximately 74.71%, whereas latent and sensible heat fluxes dominate in the low temperature rise region (∆T ≥ 1 °C), accounting for a combined contribution of about 88.58%. These findings provide a scientific basis for model simplification and targeted parameterization.