Prandtl number signifies the thickness of thermal boundary layer and thickness of hydrodyanamic boundary layer , depending on whether it is equal to one, or more than one or less than one. If it is equal to one, it signifies that thickness of thermal boundary layer is equal to that of velocity boundary layer.
What is the physical significance of the Reynolds number and Prandtl numbers?
This is proportional to the ratio of inertial forces and viscous forces (forces resistant to change and heavy and gluey forces) in a fluid flow. The Reynolds number is used to study fluids as they flow . The Reynolds number determines whether a fluid flow is laminar or turbulent.
What is the physical significance of the Prandtl number does the value of the Prandtl number depend on the type of flow or the flow geometry?
The Prandtl number is a fluid property that does not depend on the type of flow or flow geometry. The values of , c p and k are known to change with temperature so the Prandtl number will change with temperature.
What is the physical significance of Nusselt number?
Nusselt number represents the ratio of heat flux by fluid when heat is transferred through fluid layer by convection when fluid involves some motion to heat flux by fluid when heat is transferred through fluid layer by conduction when fluid is motionless.
What is the physical significance of Fourier number?
What is physical significance of these numbers? Fourier number is a measure of heat conducted through a body relative to heat stored . Thus, a large value of the Fourier number indicates faster propagation of heat through a body.
What is the physical significance of Nusselt number and Prandtl number?
A Nusselt number of value one represents heat transfer by pure conduction . A value between one and 10 is characteristic of slug flow or laminar flow. A larger Nusselt number corresponds to more active convection, with turbulent flow typically in the 100–1000 range.
Why do we use Reynolds number?
The purpose of the Reynolds number is to get some sense of the relationship in fluid flow between inertial forces (that is those that keep going by Newton’s first law – an object in motion remains in motion) and viscous forces, that is those that cause the fluid to come to a stop because of the viscosity of the fluid.
What does Prandtl number depend on?
The Prandtl Number is a dimensionless number approximating the ratio of momentum diffusivity to thermal diffusivity. The Prandtl Number is often used in heat transfer and free and forced convection calculations. It depends on the fluid properties .
Is Prandtl number a physical property?
Prandtl number is a physical property of fluids .
What is Nusselt number formula?
the Nusselt number, which is Nu Dh = 890 . the hydraulic diameter of the fuel channel is: D h = 13,85 mm. the thermal conductivity of reactor coolant (300°C) is: k H2O = 0.545 W/m.K. the bulk temperature of reactor coolant at this axial coordinate is: T bulk = 296°C. the linear heat rate of the fuel is: q L = 300 W/cm (F Q ≈ ...
Why is Nusselt number used?
Nusselt number on the other hand is a non-dimensional heat transfer coefficient . It is used to determine whether the heat transfer is conduction or convection.
What is the physical significance of the Sherwood number?
The Sherwood number (Sh) (also called the mass transfer Nusselt number) is a dimensionless number used in mass-transfer operation. It represents the ratio of the convective mass transfer to the rate of diffusive mass transport , and is named in honor of Thomas Kilgore Sherwood.
Can Nusselt number be less than 1?
Nu can not be less than one since it gives relation between conduction and convection of the liquid.
What is Fourier number and its significance?
The Fourier Number (Fo) is a dimensionless group which arises naturally from the nondimensionalization of the conduction equation . It is very widely used in the description and prediction of the temperature response of materials undergoing transient conductive heating or cooling.
What is the significance of Biot number and Fourier number?
The Fourier number is the dimensionless time for a temperature change to occur . The Biot number represents the ratio of heat transfer resistance in the interior of the system (L/k) to the resistance between the surroundings and the system surface (1/h).
What is the difference between natural and forced convection?
The key difference between natural and forced convection is that in natural convection, the motion of the fluid is influenced by natural means whereas, in forced convection, the motion of fluids is influenced by external means.
