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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

EFFICIENCY AND TWO-PHASE FLOW OF ALKALINE WATER ELECTROLYSIS UNDER FORCED CONVECTION OF ELECTROLYTE

Get access (open in a dialog) DOI: 10.1615/IHTC13.p12.380
11 pages

Abstract

The authors have investigated so far the effects of bubbles between electrodes on efficiency of alkaline water electrolysis under natural convection of electrolyte. It was found that there is the optimum condition of water electrolysis due to bubble effects, and bubble rising velocity was experimentally measured by flow visualization. Further, two-phase flow model of alkaline water electrolysis under natural convection of electrolyte was established. In this paper, the effects of forced convection of electrolyte on efficiency of alkaline water electrolysis were experimentally investigated, and forced convective two-phase flows between electrodes were visualized. Electrode was made of Ni with Pt plating (∼1 μm thickness), with height 100 mm and width 30 mm. KOH solution (8.5 wt%, 20 °C) was used for electrolyte. Pump and flow meter were specific types for alkaline water. The experimental conditions were as follows; electrodes space δ = 1 ∼ 30 mm, current density Φ = 0.1 ∼ 2.0 A/cm2, flow velocity ul = 0.1 ∼ 2.0 m/s. The forced convective two-phase flow between electrodes was successfully visualized except at conditions of large void fraction, i.e. narrow electrodes space or high current density. The obtained experimental results show that flow velocity of forced convection clearly affects the efficiency of water electrolysis, i.e. as flow velocity becomes larger, the efficiency of water electrolysis becomes higher. The optimum condition of water electrolysis in the forced convective system was also found, that was function of current density, electrode space and flow velocity. This tendency was found to be the same qualitatively with two-phase flow model for natural convective system.