Chapter 3 - Heat exchangers and nanofluids

Abstract

Heat exchangers are used for transferring heat between two or more streams. In renewable energy systems, especially the thermal ones, heat exchangers are widely used. Heat exchangers are employed to transfer the heat, extracted from the inner surface of the Earth or the solar irradiation, to the working fluids of power generation units. In addition to apparatus used for power generation, heat exchangers are applicable in other renewable systems for providing the required thermal energy for desalination, cooling, and heating. Improving the performance of heat exchangers results in higher efficiency of the related energy systems. Different approaches are introduced for enhancing the performance of heat exchangers such as inserting fins, geometry modification, and using operating fluids with improved thermophysical properties. Nanofluids are among the favorable options for utilization in heat exchangers due to their increased thermal conductivity. Performance enhancement of heat exchangers in the case of employing nanofluids depends on various factors such as the volume fraction of particles in the base fluid, the type of nanofluid, and the operating condition. In this chapter, the mechanism of heat transfer enhancement in heat exchangers by employing nanofluids and the effective factors are presented.