- The work is concerned with a stirred tank in which water is cooled batchwise by a continuous stream of bubbling air. The work is experimental, and the phenomena are simulated by an analytical model. The experiments include direct contact of air bubbles with the stirred water, heat transfer to the ambient air through the interface, and heat transfer through the walls to cooling water in a jacket by natural or forced convection, or to ambient air by natural convection. Heat-transfer coefficients are calculated in all the cases studied, starting with free convection and proceeding systematically to a complex interaction of mechanical stirring and agitation caused by dispersed air bubbles. Special attention is given to such phenomena as enhanced heat transfer through the liquid-air interface as a result of mixing and bubbly flow. Theoretical considerations lead to a mathematical model that takes into account the heat-transfer mechanisms studied. The model simulations compare well with the experimental measurements.