Preliminary evaluation of a novel solar bubble receiver for heating a gas

Abstract

A preliminary assessment of a novel configuration of a solar gas heater is presented that takes advantage of both the high heat transfer rates in the gas-bubbling regime and the outstanding thermo-physical properties of molten metals or their oxides. In this device a gas is injected as bubbles through the submerged nozzles into a bath of heat transfer fluid, into which the cavity is also submerged. This induces turbulence into the molten bath, which augments the rate of heat transfer between the outlet surface of the cavity and the gas. The first-of-a-kind experimental demonstration of this novel concept, using gallium and argon, reports a temperature difference of approximately 10 °C between the cavity and the molten bath. This corresponds to a mean heat transfer rate of more than 3.4 × 103 W/m2 °C. The well-known trade-off between heat transfer and pressure drop overlaps those employed in the highest performing devices reported previously. However, this is expected to be achieved without the same mechanical constraints that can induce high stresses, since the cavity is free to move unconstrained within the bath. Furthermore, many alternative configurations are possible, which offer a different trade-off between heat transfer and pressure drop.