ANS:A - Gilliland

The Gilliland correlation, also known as the Gilliland equation, is a widely used empirical correlation in chemical engineering and fluid dynamics. It provides an estimation for the flooding velocity, which is the velocity at which the gas phase flow in a packed tower becomes so high that it disrupts the liquid flow, causing flooding. The Gilliland correlation is expressed as: 𝑉𝑓=𝑘⋅𝜌𝐿−𝜌𝐺𝜌𝐺Vf​=k⋅ρG​ρL​−ρG​​​ Where:

• 𝑉𝑓Vf​ is the flooding velocity,
• 𝜌𝐿ρL​ is the density of the liquid phase,
• 𝜌𝐺ρG​ is the density of the gas phase, and
• 𝑘k is a dimensionless constant that depends on the properties of the system, such as the packing type and size, and the physical properties of the fluids.

The Gilliland equation is particularly useful in designing and operating packed towers or columns used in chemical processes, such as distillation, absorption, and stripping. By calculating the flooding velocity, engineers can ensure that the gas and liquid flow rates are within acceptable limits to avoid flooding, which can impair the efficiency and performance of the separation process. It's worth noting that while the Gilliland correlation provides a useful estimation for flooding velocity, actual performance may vary depending on factors such as packing geometry, fluid properties, and operating conditions. Therefore, it's often used as a starting point for design calculations, with adjustments made based on empirical data and experimental observations.