Understanding Bubble Growth in Boiling Transfer — Lesson - 2

This lesson covers the process of bubble growth in boiling transfer, a crucial aspect of volumetric transfer. It delves into the stages of bubble growth, starting from nucleation to the final departure from the heated surface. The lesson also discusses the role of pressure and temperature in bubble growth and how these factors vary in different industrial situations. It introduces the pioneering work of Lord Rally on bubble growth and explains the concept of inertia-controlled and heat transfer-controlled growth. The lesson also touches on the importance of nucleation sites in the boiling process.

Video Highlights

00:17 - Introduction to volumetric transfer and the process of boiling, including nucleation and bubble growth
10:28 - Discussion on the role of fluid momentum, pressure difference, and rate of vaporization in bubble growth
24:19 - Discussion on the conditions and characteristics of heat transfer controlled bubble growth
31:18 - Explanation of the intermediate stage of bubble growth, controlled by both inertia and heat transfer
42:43 - Discussion on the role of nucleation sites in the process of boiling

Key Takeaways

- Bubble growth is a significant part of the boiling transfer process, which involves nucleation, growth, and departure from the heated surface.
- The pressure and temperature inside the bubble play a crucial role in its growth and are subject to change in different industrial and natural phenomena.
- Lord Rally's work on bubble growth provides a simplified version of the process, assuming a single bubble in a large bulk of fluid.
- Inertia-controlled growth occurs at the initial stage of bubble growth, where the pressure is at its maximum and the growth rate is dictated by momentum transfer.
- Heat transfer-controlled growth occurs at a much later stage, where the temperature approaches its maximum value and the growth rate is dictated by heat transfer.
- Nucleation sites on a heated surface play a significant role in the boiling process, aiding in the formation of bubble nuclei.