Dittus-Boelter correlation (Eq. 1.74) is the first heat transfer correlation for turbulent flow inside smooth pipes , and this correlation is used in pipes with L D ≥ 60 and fluid with 0.7–100 Pr values and Re > 10,000 [5]: (1.74)
What are heat transfer correlations?
This heat transfer correlation takes the form of the piecewise function divided by the value of the Bu number . ... In their work, the dimensionless numbers such as the buoyancy number and the acceleration number were proposed to correct the deviation of the real heat transfer from that of the normal HT regime.
What is the use of dittus-Boelter equation?
The Dittus–Boelter equation (for turbulent flow) is an explicit function for calculating the Nusselt number . The Nusselt number is the ratio of convective to conductive heat transfer across (normal to) the boundary.
What is H in Nusselt number?
h = convective heat transfer coefficient .
What does the Nusselt number represent?
The Nusselt number is defined as the ratio of convection heat transfer to fluid conduction heat transfer under the same conditions .
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 does the Reynolds number represent?
The Reynolds number is the ratio of inertial forces to viscous forces . The Reynolds number is a dimensionless number used to categorize the fluids systems in which the effect of viscosity is important in controlling the velocities or the flow pattern of a fluid.
What does H stand for in heat transfer?
where q = heat transfer rate (W) h = convective heat transfer coefficient (W/(m 2 ·K)) t = wall thickness (m) k = wall thermal conductivity (W/m·K) A = area (m 2 )
How do you calculate heat transfer?
| Q Heat transferred | Delta T Difference in temperature |
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What is M in heat transfer?
Unsteady state heat transfer
we arrive at a general expression for the temperature change: ... The last term m is the relationship between the thermal conductivity (k) and the overall heat transfer coefficient (h) .
Is Nusselt number constant?
The Nusselt number in the fully developed laminar flow is constant and depends on the channel geometry and the wall heat transfer boundary condition.
What is the value of prandtl no?
| Fluid Temp. °C Prandtl number | sodium 100 0.01 | mercury 25 0.03 | air 30 0.72 | carbon disulfide 25 2.36 |
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How do I get a Nusselt number?
- Nusselt Number : Nu = hL/k.
- Convection Heat Transfer Coefficient : k = Nuk/L.
- Characteristic Length : L = Nuk/h.
- Thermal Conductivity of the Fluid : k = hL/Nu.
- Where, Nu = Nusselt Number, h = Convection Heat Transfer Coefficient, L = Characteristic Length, k = Thermal Conductivity of the Fluid.
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.
How does Forced Convection work?
Forced Convection Heat Transfer
In natural convection, any fluid motion is caused by natural means such as the buoyancy effect, i.e. the rise of warmer fluid and fall the cooler fluid. Whereas in forced convection, the fluid is forced to flow over a surface or in a tube by external means such as a pump or fan.
Which number can be used for convective heat transfer?
Nusselt number is the dimensionless heat transfer coefficient and appears when you are dealing with convection. It, therefore, provides a measure of the convection heat transfer at the surface.
