Objective:

High temperature heat exchangers scale heavily when operated at wall temperatures above 150°F. Scaling results from the reduced solubility of calcareous salts in high temperature water. Since the hot inlet gas causes high tube-wall temperatures on the seawater side of the heat exchanger, dissolved solids in the seawater coolant precipitate and form calcareous deposits on the tube walls. These deposits corrode and erode the walls, causing cracks and holes that eventually lead to failure. As a result, in-situ and shore-based depot chemical cleaning are required to help prevent corrosion and erosion. These costly and manpower-intensive processes use various cleaning chemicals, such as tri-sodium phosphate, sulfamic acid, and sodium carbonate. Shore-based activities then carry excess hazardous materials in support of these cleaning procedures, and this can generate up to 10,000 gallons of hazardous waste per application. The objective of this project is to eliminate acid cleaning by validating a new design for saltwater heat exchangers.

Technology Description:

The project will demonstrate and test a new heat pipe technology in a bleed air heat exchanger (BAHE). This heat exchanger is used on gas turbine-powered ships to cool the gas turbine engine bleed air from 925 to 190°F. To eliminate scaling and the use of hazardous chemicals in main condensers and in the BAHE, a heat pipe (HP) configuration will be substituted for the existing shell-and-tube design. Reproducibility testing and assessments will be conducted, and cost benefit analyses comparing heat pipe coolers to shell and tube coolers are planned.

Expected Benefits:

The successful application of this technology will have a large payback through reductions in hazardous wastes, maintenance, and total ownership costs. In selected applications, the implementation of HP heat exchangers will also increase the longevity of the heat exchangers by eliminating scaling that induces corrosion and erosion and eventually failure of the coolers and other downstream components.
(Anticipated Project Completion - 2006)

Contact:

Mr. Denis Colahan
Naval Sea Systems Command
Naval Surface Warfare Center
Carderock Division, Code 983
5001 South Broad Street
Philadelphia, PA 19112-5083
Telephone: (215) 897-7231
Fax: (215) 897-7564
E-mail: ColahanDJ@nswccd.navy.mil