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MIXED CONVECTION HEAT TRANSFER TO SUPERCRITICAL PRESSURE WATER

M.J. Watts
University of Manchester,Manchester,England

C.T. Chou
Nanking Institute of Technology,China (currently at the University of Manchester).

Abstract

This report presents the results of mixed convection heat transfer tests using supercritical pressure water at 250 bar, flowing either vertically upwards or downwards in two test sections, respectively 2 000 mm long × 25 mm bore and 2000 mm long × 32.2 mm bore. Mass fluxes of 106-1060 kg/(sm2) and heat fluxes from 175-440 kW/m2 were used; bulk fluid temperatures were between 150 and 310°C with wall temperatures from 260- 520°C. A regime of deteriorated heat transfer was found in vertical upflow, commencing as the 'buoyancy parameter' Gτb/Reb2·7b0·5 was increased above 10−5; heat transfer coefficients reached a minimum at a value of this buoyancy parameter of 4.5.10−5 and then recovered steadily into the free convection region. With vertical downflow heat transfer coefficients improved steadily as the buoyancy parameter increased from 5.10−6 to 5.10−4. Equations correlating upflow and downflow results are presented.

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