USING LOW-GRADE THERMAL-ENERGY

Low-grade thermal energy is available in such sources as industrial waste streams and tropical oceans heated by the sun. The successful tapping of this reservoir of energy requires heat exchangers specifically designed for the purpose. The most important consideration in the design of a heat exchanger is determining for what it will be used. Service can be classified in several ways, but the authors define it in terms of the amount of thermal energy to be transferred per unit time (heat duty), the heat-transfer mechanisms employed, whether the fluids are liquid or gas (or even solid, as in ice-making machines), and whether a change of state occurs during the heat-transfer process. The authors present various approaches to reducing the cost of removing thermal energy from low-grade sources. The biofouling characteristics of materials are examined along with corrosion tests of titanium and alloy steel.