ANS:A - Stanton number

The Stanton number (St) is a dimensionless group used in heat transfer analysis to characterize the ratio of heat transfer into a fluid to the thermal capacity of that fluid. It's particularly useful in problems where convective heat transfer is dominant. Mathematically, the Stanton number (St) is defined as: St=Heat transfer coefficient×AreaFluid mass flow rate×Specific heat capacitySt=Fluid mass flow rate×Specific heat capacityHeat transfer coefficient×Area​ Where:

• Heat transfer coefficient represents the rate of heat transfer per unit area between the fluid and the surface.
• Area is the surface area across which the heat transfer is occurring.
• Fluid mass flow rate represents the amount of fluid passing through the system.
• Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of the fluid by one degree.

Key points about the Stanton number:

1. Interpretation: The Stanton number represents the ratio of the convective heat transfer to the fluid to the fluid's thermal inertia or capacity to absorb heat. It characterizes the efficiency of heat transfer from a solid surface to a fluid stream.
2. Applications: The Stanton number is commonly used in the analysis and design of heat exchangers, where it helps engineers understand the effectiveness of the heat transfer process between the hot and cold fluids flowing through the exchanger.
3. Relationship with Other Parameters: The Stanton number is related to the Nusselt number (Nu) and Reynolds number (Re) in convective heat transfer problems. It's often used in conjunction with these parameters to analyze and predict heat transfer rates.
4. Influence on Heat Transfer Rates: A higher Stanton number indicates a more efficient heat transfer process, meaning that a larger amount of heat is transferred into the fluid for a given temperature difference or surface area.

In summary, the Stanton number is a dimensionless parameter used to quantify the efficiency of convective heat transfer between a solid surface and a fluid. It provides valuable information for engineers in designing and optimizing heat transfer systems.