The document discusses forced convection in laminar and turbulent flow in flat plates and pipes. It defines key concepts such as laminar vs turbulent flow, Reynolds number, Nusselt number, Prandtl number, and boundary layers. It explains that laminar flow occurs at low velocities while turbulent flow occurs at higher velocities. The transition from laminar to turbulent flow depends on factors like surface geometry and roughness, upstream velocity, and fluid type. It also discusses temperature profiles that develop in forced convection situations and laminar/turbulent flow over flat plates.

2. Forced Convection In Laminar
And Turbulent Flow In Flat
Plated Tubes And Pipes
Presented To:
Mam. Aisha kousar

3. Group Members:
 13CH03 13CH10 13CH101
 13CH18 13CH146 13CH110
 13CH128 13CH156 13CH138
13CH126 13CH137

4. In order to understand the presentation
,following concepts should be clear
Forced Convection
Turbulent Flow
Laminar Flow
Nusselt Number
Prandtl number
Boundary Layer
Friction Factor

5. Turbulent And laminar flow
 Laminar flow:
 Where the fluid moves slowly in layers in a pipe, without much
 mixing among the layers.
 Turbulent flow
 Opposite of laminar, where considerable mixing occurs,
 velocities are high.

6. Reynolds Number:
 The Reynolds number is defined as the ratio of inertial forces
to viscous forces and consequently quantifies the relative
importance of these two types of forces for given flow conditions .
 They are also used to characterize different flow regimes within a similar fluid,
such as laminar or turbulent flow:
 laminar flow occurs at low Reynolds numbers, where viscous forces are
dominant, and is characterized by smooth, constant fluid motion;
 turbulent flow occurs at high Reynolds numbers and is dominated by inertial
forces, which tend to produce eddies, vortices and other flow instabilities.
 where:
 is the mean velocity of the object relative to the fluid (SI units: m/s)
 is a characteristic linear dimension, (travelled length of the fluid; hydraulic
diameter when dealing with river systems) (m)
 is the dynamic viscosity of the fluid (Pa·s or N·s/m² or kg/(m·s))
 is the kinematics viscosity ( ) (m²/s)
 is the density of the fluid (kg/m³).

7. Nusselt Number:
 In heat transfer at a boundary (surface) within a fluid, the Nusselt
number (Nu) is the ratio of convective to conductive heat transfer
across (normal to) the boundary.
 A Nusselt number close to one, namely convection and conduction of
similar magnitude, 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.

8.  Prandtl Number
 The Prandtl number is a dimensionless number, named after the German
physicist Ludwig Prandtl, defined as the ratio of momentum diffusivity
(kinematics viscosity) to thermal diffusivity. That is, the Prandtl number is given
as:
where:
 : kinematics viscosity, , (SI units : m2/s)
 : thermal diffusivity, , (SI units : m2/s)
 : dynamic viscosity, (SI units : Pa s = N s/m2)
 : thermal conductivity, (SI units : W/(m K) )
 : specific heat, (SI units : J/(kg K) )
 : density, (SI units : kg/m3 )
Pr<1 means thermal diffusivity dominates., Pr>1momentum diffusivity
dominates

9. Dependence Of transition and laminar
flow
The transition from laminar to turbulent
flow depends on the surface geometry,
surface roughness, upstream velocity,
surface temperature, and the type of fluid,
among other things, and is best
characterized by the Reynolds number

10.  Laminar and Turbulent Flow In Tubes
 Flow in a tube can be laminar or turbulent, depending on
the flow conditions.
 Fluid flow is streamlined and thus laminar at low
velocities, but turns turbulent as the velocity is increased
beyond a critical value.
 Transition from laminar to turbulent flow does not occur
suddenly; rather, it occurs over some range of velocity
where the flow fluctuates between laminar and turbulent
flows before it becomes fully turbulent.
 Most pipe flows encountered in practice are turbulent.
 Laminar flow is encountered when highly viscous fluids
such as oils flow in small diameter tubes or narrow
passages.

11. Temperature profile in forced
convection

12. Now consider a fluid at a uniform temperature entering a circular tube
whose surface is maintained at a different temperature. This time, the fluid
particles in the layer in contact with the surface of the tube will assume the
surface temperature. This will initiate convection heat transfer in the tube and
the development of a thermal boundary layer along the tube. The thickness of
this boundary layer also increases in the flow direction until the boundary
layer reaches the tube center and thus fills the entire tube, as shown in
Figure

13. Laminar And
Turbulent Flow
over Flat plates

14. PARALLEL FLOW OVER FLAT
PLATES
Consider the parallel flow of a fluid over a flat plate of length L in the
flow direction, as shown in Fig. 7–6. The x-coordinate is measured along
the plate surface from the leading edge in the direction of the flow. The fluid
approaches the plate in the x-direction with a uniform velocity V and
temperature T`.
The flow in the velocity boundary layers starts out as laminar,
but if the plate is sufficiently long, the flow becomes turbulent at a distance
xcr from the leading edge where the Reynolds number reaches its critical
value for transition.
The transition from laminar to turbulent flow depends on the surface geometry,
surface roughness, upstream velocity, surface temperature, and the type of
fluid, among other things, and is best characterized by the Reynolds number.

23. Forced Convection
In Laminar And
Turbulent Flow In
Pipes

26. For forced convection in pipes: