A heat transfer apparatus for processing a liquid continuously has a positive mechanical drive for a set of vertical whip rods each disposed in a vertical heat transfer tube. Each whip rod is free-standing on its lower end and is sufficiently flexible to conform closely to the inner surface of the tube as it orbits. The orbital drive propels the whip rod directly through a pair of horizontal, vertically spaced plates that engage the rods in loose openings that serve as fluid inlets from the drive plate. A motor rotates a drive shaft coupled to at least one of the drive plates through at least one eccentric crank. Each plate can be an opposed pair of plates with a separate eccentric drives 180.degree. out of phase with one another for a self balancing. Another form of drive plate uses a rigid circular ring that mounts rod-engaging sleeves via a network of wires supported by the ring. Fluid distribution can also be from a water supply held between a fixed plate and the upper drive plate with gravity feed to each tube through a properly sized inlet opening in the upper tube end. To isolate the heat transfer process, various seals are used to transmit rotary power through a housing without conventional rotary seals.

A machine for freezing or chilling a liquid continuously to produce a slurry of the liquid and frozen crystals feeds the liquid into a vertically oriented heat transfer tube at its upper end. A refrigerant flow at the outer tube surface evaporates in a vapor/foam stream causing the liquid to freeze at the inner tube surface. A whip rod, preferably one that is free-standing, revolves over the inner surface to dislodge the frozen crystals mechanically and to distribute the liquid. An additive to the liquid such as ethylene glycol (in water) aids the dislodging. In one form, a mechanical flow guide surrounding the outer surface produces a thin, high velocity upward flow of the boiling refrigerant to increase the heat transfer. An orbital drive propels the whip rod. In one form the orbital drive includes a pair of horizontal plates coupled between the whip rod and at least one eccentric crank. In another form, the drive includes a pair of counterweights coupled rigidly to the heat transfer tube that rotate in phase synchronization by independent motors through the dynamic design characteristics of the system.

An orbital evaporator has a vertical heat transfer tube or tubes mounted in a container driven in an orbital motion. A stiff whip rod is freely movable within the tube. Its lower end rests on a horizontal plate. The orbital motion causes the rod to roll over the interior surface of the tube to distribute the liquid in a thin film and to control fouling. A set of fins is mounted on the exterior of the tube to collect and channel the condensate to improve heat transfer through the tube. The fins are preferably longitudinal and the whip rod is preferably hydrophobic. Operating the evaporator with boiling temperatures substantially below 100.degree. C. in combination with the fins and a rolling whip rod allows operation as a desalinization unit for an indefinite period of time with a high total heat transfer coefficient. The evaporator preferably also includes a degasser to control the formation of a gas barrier at the exterior surface of the tube.