Abstract: An enclosure containing rotating blades for mechanical stirring of gaseous fluids may be a heat exchanger, flue gas energy recovery device, gas generator or combustion device. A high rotational stirring velocity increases the convective heat transfer rate, rendering it independent of the lower throughput velocity of primary fluid which can be controlled independently of the stirring speed. Primary fluid is isolated from a secondary fluid by a thermal transfer surface which is continuously swept by the swirling primary fluid and which may be the peripheral wall of the enclosure or a flow tube located proximate the peripheral wall. In one embodiment, swirling is achieved by radially-extending blade assemblies secured to a rotatable shaft at longitudinally spaced locations to establish discrete swirling zones in which fluid recirculates from the shaft outwardly, along the wall, and back toward the shaft.

Abstract: Method and apparatus for improving convective heat transfer by mechanically stirring fluid over the outer surface of a heat exchanger. A stirring mechanism is described which revolves rapidly around a heat exchanger surface in a stream undergoing heat transfer. During rotation, the stirring mechanism is supported near an end of the stirred heat exchanger by a central bearing and drive means. It is also supported over an extended length of the stirred heat exchanger surface by the hydrodynamic action of the stirring mechanism relative to the heat exchange surface without need for an additional central support bearing. The stirring mechanism uniformly turbulates the fluid film over the outer surface of the heat exchanger where heat transfer resistance normally occurs without imposing a pressure drop in the fluid stream undergoing augmented heat transfer. Compact and inexpensive heat exchangers are described which may be used in refrigeration, heating-cooling, and energy conservation systems.