Observation and Assessment of Heat Transfer Coefficient of Thermal Discharge for Coastal Nuclear Power Plants

The heat transfer coefficient of the water surface is an important parameter in the design of thermal discharge in nuclear power plant engineering. In this study, in situ observations were performed in the northwestern South China Sea near a coastal nuclear power plant to evaluate the applicability of heat transfer coefficient calculation algorithms commonly used in marine thermal discharge engineering in China. The results show that the Regulation for Hydraulic and Thermal Model in Cooling Water Projects (SL 160-2012) is not applicable in calculating the heat transfer coefficient in offshore areas. SL 160-2012 significantly overestimates the heat loss at the sea surface. However, Code for Design of Cooling for Industrial Recirculating Water (GB/T 50102-2014) performs well, and its estimation coefficient is roughly consistent with the estimations of the COARE 3.6 bulk algorithm, which is extensively used in physical oceanography for calculating air-sea heat fluxes, and the Gunneberg formula. In a 3-day observation, the average heat transfer coefficients estimated using these three algorithms were 50.4, 48.5, and 48.8 W m⁻² ℃⁻¹, respectively, with a deviation of less than 4% among them, whereas that estimated using SL 160-2012 was as high as 176.3 W m⁻² ℃⁻¹. The abnormally large value of SL 160-2012 is due to its additional cooling term, which is artificially increased by 100 times because of the incorrect unit conversion used when developing the regulation. If this error is corrected, the value will decrease to 50.5 W m⁻² ℃⁻¹, which is very close to the estimation of GB/T 50102-2014.