ANS:B - In steady state heat conduction, the only property of the substance which determines the temperature distribution, is the thermal conductivity.

"In heat transfer by forced convection, the Grashof number is very important." The Grashof number (Gr) is a dimensionless parameter used in forced convection heat transfer to characterize the relative importance of buoyancy forces to viscous forces. It is defined as the ratio of buoyancy forces to viscous forces and is expressed as: Gr=ν2g⋅β⋅(Ts​−T∞​)⋅L3​ where:

• g is the acceleration due to gravity,
• β is the coefficient of thermal expansion,
• Ts​ is the surface temperature,
• T∞​ is the fluid temperature,
• L is a characteristic length,
• ν is the kinematic viscosity of the fluid.

The Grashof number is particularly important in natural convection, where buoyancy forces dominate the heat transfer process. However, it can also be relevant in forced convection, especially in situations where buoyancy effects cannot be neglected, such as when dealing with heated vertical surfaces. So, the correct statement is: "In heat transfer by forced convection, Grashof number is very important."