Suscripción a Biblioteca: Guest

ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

EXPERIMENTAL STUDY ON HEAT TRANSFER OF 5X5 HEATER ROD BUNDLE WITH HFC-134A FLUID NEAR THE CRITICAL PRESSURE

Get access (open in a dialog) DOI: 10.1615/IHTC13.p18.320
10 pages

Sinopsis

A supercritical-pressure water cooled reactor (SCWR) is currently investigated as the next generation nuclear reactors. When the SCWRs are operated with the sliding pressure start-up scheme, a critical heat flux (CHF) should be avoided during the power increasing phase under the sub-critical pressure conditions. An experimental study of heat transfer characteristics near the critical pressure has been performed with a vertical 5x5 heater rod bundle cooled by HFC-134a fluid. The outer diameter, heated length and pitch of heater rods are 9.5, 2000 and 12.85 mm, respectively. The CHF has been measured in a range of the pressure of 2.47∼4.03 MPa (the critical pressure of HFC-134a is 4.059 MPa), the mass flux 50∼2000 kg/m2s, and the inlet subcooling 40∼84 kJ/kg. The critical power decreases sharply with the system pressure near the critical pressure and shows a trend towards converging to zero as the pressure approaches the critical point. For the low mass fluxes of 50 to 250 kg/m2, the sharp decreasing trend of CHF near the critical pressure is not observed. The CHF phenomenon near the critical pressure no longer leads to an inordinate increase in the heated wall temperature such as the case of the DNB (departure from nucleate boiling) at normal pressure conditions. The existence of a threshold pressure at which the CHF phenomenon disappears has been observed near the critical pressure. In the region where the pressure passes across the threshold pressure, CHF does not occur and the wall temperature variations increase monotonously according to the power level applied to the heater rod.