Chapter 7 Natural (Free) Convection

This chapter delves into the fascinating realm of natural (free) convection, a mode of heat and mass transfer driven by density differences in a fluid due to temperature variations. The document provides a comprehensive exploration of the fundamental principles, theories, and mathematical models governing natural convection phenomena. The chapter covers the governing equations for natural convection, including the Boussinesq approximation, which simplifies the Navier-Stokes equations. It explains the role of Grashof number and Rayleigh number in characterizing the strength of natural convection in different scenarios. In addition to theoretical aspects, the document explores various geometries and configurations where natural convection is prominent, such as vertical and inclined surfaces, enclosures, and heat sinks. It provides insights into heat transfer correlations and empirical correlations used for practical engineering calculations. The chapter also highlights the significance of natural convection in engineering applications, including cooling of electronic devices, solar energy utilization, and building ventilation. It discusses strategies for enhancing or suppressing natural convection for specific engineering needs. Moreover, the document covers experimental techniques and numerical simulations used to investigate and validate natural convection behaviors. It also explores advanced topics such as transient and turbulent natural convection, offering a comprehensive understanding of this complex phenomenon. Researchers, engineers, and students will find this chapter a valuable resource for comprehending the principles and applications of natural convection, enabling them to address challenges and optimize designs across various industries and scientific fields.