R&D Evaporator

Function: Provide flash steam from warm seawater under vacuum conditions.

What do we know?

Operating temperature and pressure well known from systems analysis and resource assessment.
Extensive single-spout, deaerated freshwater experimental performance data available; limited seawater data exists.
Single-phase liquid pressure drop known from analytical hydrodynamics.
Mist eliminator pressure drop well characterized in freshwater tests for chevron and wire-mesh geometries. Semi-quantitative data on droplet removal efficiency available.
Spouts and mist eliminators can be made from plastic; costs well known. Containment material and cost is less well established (steel/concrete options explored).
Macrofouling problems anticipated to be minimal.
Parametric studies of leak rate have bracketed system performance effects.
Simple low-cost enhancements (screens placed in downward flow) can increase evaporator effectiveness to near the theoretical limit in freshwater.
Evaporator geometry options including trays, falling films, and falling jets have been evaluated both analytically and experimentally (jets and films). Spout evaporators show significant performance, cost and layout advantages over these other options.

Operating conditions of evaporator (temperature, pressure, noncondensible gas contents, droplet generation, and carryover).
Chemical composition and quantity of noncondensibles in evaporator inlet, outlet, and steam, and their effects on component and system performance.
Spout evaporator, performance (effectiveness and pressure drop as a function of spout geometry and operating conditions, including multiple spouts).
Mist eliminator performance (pressure drop and droplet removal).
Materials selection and component costs.
Corrosion and bio/macro fouling control needs and methods.
Leak rate of air into vacuum system.
Dynamic performance and stability.
System interactions, integration, and operation control.
Performance and costs of various evaporator geometries.

Determine effect of pre-deaeration on component performance (effectiveness, liquid pressure drop, droplet generation).
Verify spout and mist eliminator performance in seawater (both single and multiple spouts).
Determine multiple spout interaction effects and possible interactions with mist eliminator in seawater.
Determine effects of multiphase flow on liquid pressure drop.
Determine spout stability and dynamic performance of prototypical evaporator, including seawater induced effects (tides, waves).
Determine macrofouling effects, if any, in seawater.
Reduce uncertainty in containment costs/materials and leak rates through prototypical designs and estimates.
Determine system interactions, integration, and control through construction of test facilities and the net power producing experiment.
Determine mist eliminator droplet removable efficiency in seawater operations.
Determine long-term reliability.
Obtain operational data for commercial environments.