The Nutrient Megapump


Mixing deep ocean nutrient depends on being able to use the heat energy from hydrothermal vents on the ocen floor to raise cold, dense, nutrient-rich sea water from 1000m depth into the sunlit surface layer at, say, 20 m depth. To do this we designed a nutrient megapump. The megapump is a bubble pump in which the "bubbles" comprise slugs of steam. The steam is very "wet" meaning that it still contains a good deal of unevaporated water.





Pumps need valves to control flow. The Nutrient Megapump utilizes the strange properties of wet steam to create a valve. The speed of sound in wet steam is extremely low which means that sonic shock fronts form readily. It is impossible to force fluid through a pipe at speeds greater than the speed of sound. In the diagram on the right superheated water flows through a short "injector" pipe and flashes to steam once it has passed through the pipe. In the diagram on the left, wet steam is inhibited from flowing through the injector pipe by the formation of a sonic shock.


Injectors blocked. Rising fat pipe slug.


Injectors blocked. Slug dispersed.


Injectors open. New slug forming

Injectors blocked. New slug rising


The Nutrient Megapump consists of two pipes: a long, thin, thermally insulated pipe sealed at the top end which brings superheated vent fluid up from a cowling placed over a hydrothermal vent on the sea floor, and a shorter "fat" pipe which has the lower end in the nutrient layer and the upper end in the sunlit mixed layer of the ocean.

The hydrostatic pressure at the top end of the thin pipe is low enough for the vent fluid (at 360 C) to boil and form wet steam. Wet steam is elastic and acts like a spring so that the fluid in the thin pipe oscillates. Superheated water is expelled from the injectors near the top of the thin pipe during each oscillation. The above diagrms show the four phases of this oscillation.

The expelled superheated water creates a slug of wet steam in the fat pipe. This slug has much lower density than the surrounding sea water and rises toward the surface carrying nutrient-rich sea water with it. When the nutrients reach sunlight, a bloom of phytoplankton forms. This bloom will grow as more nutrient is pumped up and so forms the basis of a marine ecosystem supporting higher life forms such as fish and dolphins.

The Nutrient Megapump is a gigantic bubble pump operating on a similar principle to the pump inside a kerosine refrigerator. The fat pipe can be constructed from plastic sheet and poly-pipe, i.e. fish farm technology. The thin pipe will be teflon-coated aluminium at the top end and a special concrete called calsil at the lower, hot end.

The pump has no moving parts so reducing maintenance and fouling problems. It will be the largest pump ever constructed.

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