Experimental studies of direct contact heat transfer in a slurry bubble column at high gas temperature of a helium–water–alumina system

• Direct contact heat transfer is investigated experimentally in a slurry bubble column.
• Empirical equation of direct contact heat transfer Nusselt number is formulated.
• The volumetric heat transfer coefficient increases with superficial gas velocity.
• The volumetric heat transfer coefficient decreases with the static liquid height.
• The volumetric heat transfer coefficient decreases with the solid concentration.

In this paper, the direct contact heat transfer is investigated experimentally for a helium gas at 90 °C injected through a slurry of water at 22 °C and alumina solid particles in a slurry bubble column reactor. This work examines the effects of superficial gas velocity, static liquid height, solid particles concentration and solid particle size, on the volumetric heat transfer coefficient and slurry temperature of the slurry bubble column reactor. These effects are formulated in forms of empirical equations. From the experimental work, it is found that the volumetric heat transfer coefficient and the slurry temperature increase by increasing the superficial gas velocity with a higher rate of increase at lower superficial gas velocity. In addition, the volumetric heat transfer coefficient and the slurry temperature decrease by increasing the static liquid height and/or the solid concentration at any given superficial gas velocity. Furthermore, it is found that the rate of decrease of the volumetric heat transfer coefficient with the solid concentration is approximately the same for different superficial gas velocities, and the decrease of the slurry temperature with the solid concentration is negligible.