The Kinetic Water Pump

ADIABATIC EXPANSION

 This document proposes a novel method that allows adiabatic expansion of the steam (or other vapor) and yet pumps high-pressure water (or other liquid) in an energy efficient manner. In Figure 2, the boiler is heated by solar energy (or other energy). During times of cloudiness or at night, the boiler can be heated by other means. Valve 1 opens to allow a small amount of steam (or other working vapor) to flow into Chamber A in the Acceleration Tube. As the steam enters, it begins to accelerate the water in the Tube at constant steam pressure. Valve 1 is then closed, and the steam above the water expands adiabatically and continues to accelerate the water in the Tube. It should be noted that the work done on the water, both during the initial displacement and during the adiabatic expansion, is converted into kinetic energy of the body of water. The water continues to accelerate until the “front end” of the water in the Acceleration Tube reaches the other end of the tube and forces the check valve open in the Compressed-Air Surge Tank. The high pressure begins to decelerate the water, but it will continue to flow until its kinetic energy is exhausted. Simply stated, the kinetic energy of the water in the Acceleration Tube is converted into potential energy of high-pressure water in the Surge Tank.

Note that there is a free run in Chamber B as the water body flows into a partial vacuum (water vapor only), and this allows the water to increase in kinetic energy as it efficiently uses the heat energy in the steam. The pressure of the pumped water (in the Compressed Air Surge Tank) can be much higher than the boiler pressure.

Only a small part of the water in the Acceleration Tube enters the Compressed-Air Surge Tank, but the kinetic energy of all the water in the Tube provides the “ram” that forces the water into a higher-pressure region. As the water in the front encounters the high-pressure air in the Surge Tank, the momentum of the rest of the water continues to push. This is similar to the old hydraulic ram in which a low head of water was used to pump water to a higher head.

After this part of the cycle has ended, Valve 2 opens and allows the steam from Chamber A to flow through a Heat Exchanger, where it pre-heats the feed water flowing to the Boiler. Then it flows into the Condenser where it is condensed to a liquid by cool

Figure 2. Schematic drawing of a steam-driven Kinetic Pump. Kinetic energy of the water in the Acceleration Tube provides the energy needed to force the water into a higher-pressure chamber.

seawater. This heats the incoming seawater that then flows to the RO unit via the Kinetic

Pump. Having the seawater warmer makes the RO process more efficient. The condensed feed water is pumped back to the boiler. This feed pump could actually be a small steam-powered Kinetic Pump.

As the steam is condensed, the Acceleration Tube is left with a partial vacuum above the water in both chambers A and B. Replacement water is drawn into the Acceleration Tube through Valve 3. The cycle is then repeated.

The reason for having the Compressed-Air Surge Tank at the point where the water enters the high-pressure region is to prevent the incoming water from immediately colliding with water already present in the high-pressure region. Without the air cushion, the incoming water would have to accelerate the local water, and that can be difficult if there is a long outlet pipe filled with water, since water is essentially incompressible at the pressures involved (about 0.1% compression in going from atmospheric pressure to 1,500 psi). With the air present, the incoming water can collide with low-density air and compress the air. The volume of the Surge Tank should be sufficiently large so that the air pressure does not rise significantly during the inflow of water. After the incoming water enters the high-pressure region, it drains to the outlet pipe and then flows to the RO unit (or to other end use) at high pressure.

The some of the steam entering the Acceleration Tube condenses on the Tube wall and represents a loss in energy. The wall should be lined by an insulating material to minimize this effect. An insulating float is placed on top of the water to reduce condensation on the water surface. Without this float, steam would begin to condense on the water surface and quickly heat a thin layer of water on the surface to reach equilibrium. The float also eliminates the effect of Taylor instability of the interface between the water and the steam.

Introduction | Part 1 | Part 2 | Part 3 | Part 4