Effect of Buoyancy on Heat Transfer in Supercritical Water Flow in a Horizontal Round Tube

Abstract

Heat transfer to supercritical water and buoyancy∕natural convection effects are becoming increasingly important areas of research due to current trends in nuclear reactor design and supercritical water oxidation facilities. A pilot-scale supercritical water oxidation loop was constructed at the University of British Columbia. For this work, the facility was used to study the relative importance of buoyancy effects on supercritical water flowing in a horizontal pipe. Local heat transfer coefficients at the top and bottom surfaces of the horizontal test section were systematically measured over a wide range of conditions at supercritical pressures between 23 to 27 MPa, uniform heat fluxes were up to 310kW∕m2, and the mass flux ranged from 330 to 1230kg∕m2s. It was found that neglecting buoyancy effects could cause large discrepancies between the predictions of available empirical correlations and the experimental data. The data was used to assess available criteria for the buoyancy-free region during horizontal supercritical fluid flows. The criterion of Petukhov and Polyakov, which, for the range of parameters in this study, was found to be accurate in predicting the onset of buoyancy effects. The experimental investigation is confined to supercritical flows with heat addition only. Hence, no heat loss conditions at supercritical temperatures were investigated.

Numerical investigation of diameter effect on heat transfer of supercritical water flows in horizontal round tubes

“…In [9] it studied the horizontal tubes compared with the experiments in [6] and found the Speziale non-linear high Reynolds k-ε turbulence model with the Hassid and Poreh near-wall treatment under y + < 1.0 can give good predictions of the heat transfer of SCW using STAR-CD code. In this paper, the mesh partition method (stretched mesh near wall and general structure mesh inside main flow domain), y + value and the Speziale non-linear high…”

“…2 shows the schematic geometry. The computational test parameters are used same as the experiments in [6]. In the geometry sketch, L is the tube length and D is the tube diameter.…”

“…Near the pseudo-critical temperature, SCW has the dramatic variations of the physical properties in [6]. Therefore, it is important for users to understand the behaviors of the heat transfer of SCW affected by these characteristics when SCW is employed.…”

Experimental and Numerical Investigation of Convective Heat Transfer of Supercritical Carbon Dioxide at Low Mass Fluxes

“…During this evolution, buoyancy played an important role in heat transfer at supercritical pressures. A number of research papers [35][36][37][38] discussed the effect of buoyancy on heat transfer in supercritical fluids.…”

“…evolution, buoyancy played an important role in heat transfer at supercritical pressures. A number of research papers [35][36][37][38] discussed the effect of buoyancy on heat transfer in supercritical fluids. From the above literature review, it can be observed that mixed convection heat transfer in supercritical CO2, flowing vertically in a uniformly-heated circular tube at low mass flux, has not received much research attention.…”