649 / 2019-02-11 16:50:59

Experimental investigation of heat transfer characteristics of supercritical water in the entrance region of a vertical upward tube

Supercritical water; Entrance effect; Deterioration heat transfer; Enhanced heat transfer

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In order to investigate the special heat transfer characteristics of supercritical water in the entrance region, a series of experiments have been conducted in a 3-m long vertical upward tube with 20.0-mm internal diameter. The experimental parameters cover the pressures from 22.5 to 27 MPa, the mass fluxes from 150 to 600 kg穖-2穝-1, and the heat fluxes from 50 to 500 kW穖-2. Enhanced heat transfer (EHT) was observed at the inlet of the test section which was different from the EHT occurred near the pseudo-critical point. Deteriorated heat transfer (DHT) was also observed at the inlet of the test section under high q/G conditions. It was found that the inlet bulk fluid enthalpy could affect the occurrence and the degree of DHT at the inlet of the test section. DHT disappeared when the inlet bulk fluid enthalpy exceeded the pseudo-critical enthalpy. Finally, the mechanisms of the EHT and DHT occurred at the inlet of test section were analyzed.