Effects of Bubble Injection on Heat Transfer from a Volumetrically Heated Water Pool

The fissioning of uranium in an aqueous solution creates ⁹⁹Mo, the precursor to ^99mTc, but also generates large amounts of hydrogen and oxygen from the radiolysis of the water. When the dissolved gases reach a critical concentration, bubbles will form in the solution, affecting both the fission power and the heat transfer out of the solution. A high aspect ratio tank was constructed to measure heat transfer from a liquid pool with internal gas and heat generation. Different air injection manifolds allowed the exploration of various bubble characteristics and bubble patterns on heat transfer from the pool to the cold walls. Experimental data analysis provided heat transfer coefficient values as a function of axial position, power density, and the superficial gas velocity in the pool. Results, including a recommended correlation for average heat transfer coefficients, are provided for superficial gas velocities between 0 and 0.3 cm/s and power densities between 115 and 400 W/ℓ in water.