The Investigation of Heat Transfer Deterioration in Supercritical Water Heating Systems

Abstract The object of this study is to investigate the heat transfer deterioration (HTD) in the supercritical water (SCW) heating systems. The present study develops a new empirical correlation for predicting the onset heat flux of HTD in SCW and are compared with the existing ones in literature. The predicted values are adopted as the basis for judging the occurrence of HTD and verified against 108 independent operating conditions of SCW collected from the literature. The results reveal that the judgment accuracy can reach 95.37%. This study also employs the ratio (RHTD) of heat transfer coefficient to a reference value, based on different methods in literature, as an indicator for distinguishing HTD and non-HTD. Through the analyses among 312 points of HTD and 135 points of non-HTD extracted from the experimental results of SCW in literature, the results illustrate that the judgment accuracy by the threshold of RHTD = 1 can be over 85%. Furthermore, this study introduces the new definition of RHTD by using the film temperature as the reference state. Through the analyses of the same data points for SCW, the setting of RHTD = 1 based on the film temperature may be appropriate as the classification criteria between HTD and non-HTD.