The Dittus–Boelter equation (for turbulent flow) is an explicit function for calculating the Nusselt number. The Nusselt number is proportional to the Prandtl number for heat transfer to the heating exponent times the Reynolds number to the four-fifths power.
What is dittus-Boelter equation write its importance?
The Dittus-Boelter equation (for turbulent flow) is an explicit function for calculating the Nusselt number. It is easy to solve but is less accurate when there is a large temperature difference across the fluid. It is tailored to smooth tubes, so use for rough tubes (most commercial applications) is cautioned.
Where did the dittus and Boelter equation come from?
The following note further investigates Winterton’s claim and finds conclusive evidence that the Dittus and Boelter equation did indeed originate with McAdams.
What is the famous dittus-Boelter correlation for?
The Dittus-Boelter correlation may be used for small to moderate temperature differences, Twall – Tavg, with all properties evaluated at an averaged temperature Tavg.
What does Grashof number represent?
The Grashof number (Gr) is a dimensionless number in fluid dynamics and heat transfer which approximates the ratio of the buoyancy to viscous force acting on a fluid. It frequently arises in the study of situations involving natural convection and is analogous to the Reynolds number.
What is meant by fouling factor?
The fouling factor represents the theoretical resistance to heat flow due to a build-up of a layer of dirt or other fouling substance on the tube surfaces of the heat exchanger, but they are often overstated by the end user in an attempt to minimise the frequency of cleaning.
How is Grashof number calculated?
GRASHOF NUMBER
- g = acceleration due to gravity, m s−2
- l = representative dimension, m.
- ξ = coefficient of expansion of the fluid, K−1
- ΔT = temperature difference between the surface and the bulk of the fluid, K.
- ν = kinematic viscosity of the fluid, m2s−1 .
What is Grashof number used for?
What does Stanton number tell us?
Stanton number indicates the degree of amount of heat delivered by fluid when there is heat transfer between solid surface and fluid. The greater Stanton number is, the more effectively heat is transferred.
What is the significance of Grashof number?
The significance of the Grashof number is that it represents the ratio between the buoyancy force due to spatial variation in fluid density (caused by temperature differences) to the restraining force due to the viscosisty of the fluid.
What do you mean by Boussinesq approximation What is the physical significance of Grashof number with reference to heat transfer by natural convection?
The Grashof number is the ratio of buoyancy to viscous forces. A value below indicates that the flow is laminar, while a value above indicates that the flow is turbulent. In this case, the Grashof number is around , meaning that the flow is laminar.
