Thermal analysis and optimization of annular fins with simultaneous heat and mass transfer

摘要

Finned tube heat exchangers are widely used in industrial applications. In general, the energy exchange between the fin and surrounding gas stream takes place solely by sensible heat transfer. however, in various applications such as, air conditioning, refrigeration, evaporative air coolers, environmental control system of aircrafts and chemical processing systems, heat transfer between moist air and the fin is accompanied by diffusion mass transfer of water vapor. The prime reason for this simultaneous heat and mass transfer is that the coil surface temperature is below the dew point temperature of air being cooled. So it is important to study the most widely used fins, namely annular or circular fins, under these conditions.;One dimensional fin model is developed and studied for five types of annular fins that is constant cross-section, triangular, concave parabolic, convex parabolic and hyperbolic profiles under fully as well as partially wet conditions. In addition to studying the thermal performance numerically, their optimization is also done in the present work. An analytical solution for hyperbolic profile is introduced and compared with corresponding numerical results. Besides this, a two-dimensional fin model for rectangular profile annular fin is derived and analyzed for constant as well as distinct thermal conductivities in the fundamental directions. Furthermore, the optimum dimension for a given quantity of fin material is also laid out.