The tubular thermosyphon is a very simple idea for transferring heat. Fluid inside a tube is circulated by buoyancy forces and thus carries thermal energy from the hot end to the cold end with great efficiency. The device has many uses: freezing ground, cooling equipment and machinery, waste heat recovery, and energy conservation. The operating details of the thermosyphon are, however, very complex and change dramatically with the circumstances. The length and diameter of the tube, the nature and state of the fluid, the strength and variation of the body force field, etc., all influence the internal circulation pattern and thus create different operating characteristics - variations on a basic theme. The book deals with each of these variations thoroughly and systematically. Emphasis is placed on the physical principles underlying thermal behaviour: under single-phase or evaporative conditions; whether the tube is stationary or rotating; and whether it is straight or bent. Consideration is also given to other devices having a similar purpose.