Bicol University College of Engineering DEPARTMENT OF CHEMICAL ENGINEERING ENGINEERING A.Y. 2016-2017
FOR FROM FROM SUBJECT SUBJECT DATE
: Engr. John Raymond B. Barajas Professor, Department of Chemical Engineering : Neil Domi nic ni c D. Careo, Glanell e Ivy S. Cea BSChE 4 : Momentum Transfer : March : March 31, 2017
Transition al, and and Improvised Reynold’s Apparatus f or Laminar, Transition Turbulent Flow Determination Determination of Fluids I. Introduction The flow of real fluids can basically basicall y occur under two very different regimes, namely name ly laminar and turbulent flow. The laminar flow is characterized by fluid particles moving in the form of lamina sliding over each other, such that at any instant the velocity at all the points in particular lamina is the same. The lamina near the flow boundary move at a slower rate as compared to those near the center of the flow passage. This type of flow occurs in viscous fluids, fluids moving at slow velocity and fluids flowing through narrow passages. The turbulent flow, on the other hand is characterized by constant agitation and intermixing of fluid particles such that their velocity changes from point to point and even at the same point from time to time. This type of flow occurs in low density fluids, flow through wide passage and in high velocity flows. Reynolds conducted an experiment for observation and determination of these regimes of flow. By introducing a fine filament of dye in to the flow of water through the glass tube, at its entrance he studied the different types of flow. At low velocities, the dye filament appeared as straight line through the length of the tube and parallel to its axis, characterizing laminar flow. As the velocity is increased the dye filament becomes wavy throughout indicating transition transit ion flow. On further increasing the velocity the filament breaks up and diffuses completely in the water in the glass tube indicating the turbulent flow.
Reynolds concluded that the parameters which were involved in the flow characteristics were: ρ v d μ
the density of the fluid the velocity of the flow of the fluid Diameter of pipe the coefficient of viscosity of the fluid
kg/m 3 m/s m Ns/m 2
He arrived at a dimensionless constant (Reynolds number) =
The value of which was concerned with the fluid motion. Fluid motion was found to be laminar for Re numbers below 2100, turbulent flows for Re greater than 4000, and transitional for Reynold’s number in between.
II. Objecti ves The main objective of this study is to determine the characteristic flow of the liquid, whether it is laminar, turbulent or transitional fluid flow, in the improvised Reynold’s apparatus which is also used to determine the Reynold ’s number for each state of flow.
III. Methodology A. Appar Ap paratu atus s Osbourne Reynolds Apparatus consisting of: •
Dye Injection Vessel
•
Water Inlet
•
Dye Injector
•
Clear Glass Tube
Baffles
•
•
Overflow pipe
•
Discharge Valve
•
Head Height measurement
•
Water Storage tank
B. Materials: Name Na me Beaker Beaker Thermometer Dye Stop Watch
Specifi Spe cifi cations 500 ml 1L -
Quantit y Quantit 2 2 1 500 ml 1
C. Procedure Setting Setting up t he apparatus apparatus The tank in the apparatus was filled with water while keeping the discharge valve closed first. After the tank was full, a purple liquid dye was then mounted into the dye injector to start the experiment.
Measuring Measuring the Volumetric Flow Rate Rate and Veloci Veloci ty The flow rate of water was measured through the apparatus and achieved by collecting a sample of discharged water after an interval of 10 seconds and measured using 1 L beakers. The recorded volume of water was then divided by the time of 10 seconds. The resulting volumetric flow rate was divided by the crosssectional area of the glass pipe. Thus, the fluid’s velocity was calculated.
Viscosit y and and Densit Densit y of Fluid The temperature of the water used was measured by a thermometer. The recorded temperature was used to determine the viscosity and density of the fluid.
Demonst Demonst ration of the difference between between laminar laminar and turb ulent This experiment demonstrated the visually laminar (streamline) flow and its transition to turbulent flow at a particular velocity.
1. The apparatus is set up with the dye transparent tube and filled, and with a steady flow of water through the inner tube.
2. A needle connected to the transparent tube was used to permit permit dye to flow from the nozzle at the entrance to the channel. The colored dye will be visible along the passage. If the dye accumulates around the nozzle, the velocity of the water flow in the passage has to be increased or regulate the flow from the dye reservoir. T he adjustments of the dye flow are made up by using the tube outlet tap.
3. The stream will be visible along the whole length of the passage under laminar flow conditions. If it not so, the water flow is reduced unti l continuous stream of dye is visible along the passage.
4. The water flow rate is increased by raising the height of the variable head tank and the condition of the fluid in the channel carefully note, for example, the streamline and turbulent. The height of head tank is increased until instability of water flow leading to the breakup of the dye system is occurred.
5. The break up position in the passage is noted and the corresponding value of the flow rate is measured by timing the collection of known amount of water in the volumetric measuring tank.
6. The dose is maintained and the observation of the passage is continued further increasing the flow rate until the whole system is turbulent with no visible dye stream at any point. IV. IV. Results Results and Discussio n Trial # 1 2 3 4 5 6
Reynolds Re ynolds Number 1,015.18 1,487.45 2,379.60 3,849.58 8,223.02 11,199.51
Calculations: Diameter of the glass tube: 0.0760 m 1
1
4
4
Therefore, = 2 = (0.0760) 2 = 2.268x10 -3 m2 Reynolds number (dimensionless constant) ѵ
Q = (m³/s)
Ѵ= volume
Q = volumetric flowrate flowrate V=
V=Velocity A=Area of the the pipe NRe =
Where, = density (kg/m³)
d = diameter (m)
V = velocity (m/s)
µ = viscosity viscosity (kg/ms)
The temperature reading is 22 degrees Celsius. Thus, Water density, ρ = 997.8 = 997.8 kg/m³ Water viscosity, µ = 9.554 x10 -4 Pa-s
s= time
Type of flow Laminar Laminar Transitional Transitional Turbulent Turbulent
Trial No. 1
Velocity (m/s)
Re =
Type of flow
99.8(. )( .129)
V(ml)= 290 ml
Re=
V(m³) = 2.9 x 10 -4 m³
9.554 x1
= 1,015.18
Q = (2.9 x 10 -4 m³)/10s
Laminar
= 2.9 x 10 -5 m³/s Velocity =
2.9 x 1 m /s 2.28x1
= 0.01279 m/s 2
99.8(. )( .184 )
V(ml)= 425 ml
Re=
V(m³) = 4.25x10 -4 m3 Q=
9.554 x1
= 1,487.45
4.25x1−4 m
Laminar
1
= 4.25x10-5 m3/s Velocity =
4.25x1−5 m /s 2.28x1
=0.01874 m/s 3
99.8(. )(.2998 )
V(ml)= 680 ml
Re=
V(m³) =6.8x10 -4 m3 Q=
.8x1−4 m3 1
9.554 x1
= 2,379.60
= 6.8x10 -5
Transitional
m3/s Velocity =
.8x1−5 m /s 2.28x1
=0.02998 m/s 4
99.8(. )(.485 )
V(ml)= 1100 ml
Re=
V(m³) = 1.1x10 -3 m3 Q=
1.1x1−3 m 1
Velocity =
3
= 1.1x10 m /s
1.1x1−4 m /s 2.28x1
=0.0485 m/s
-4
9.554 x1
= 3,849.58
Transitional
Trial No. 5
Velocity (m/s) V(ml)= 2350 ml V(m³) = 2.35x10 -3 m3 Q=
2.35x1−3 m
Re =
Type of flow
99.8(. )(.13 )
Re=
9.554 x1
= 8,223.02
Turbulent
1
= 2.35x10 -4 m3/s Velocity =
2.35x1−4 m3/s 2.28x1
=0.1036 m/s 6
V(ml)= 3,200ml V(m³) = 3.2x10 -3 m3 Q=
3.2x1−3 m
99.8(. )(.1411m )
Re=
9.554 x1−4
= 11,199.51
Turbulent
1
= 3.2x10 -4 m3/s Velocity =
3.2x1−4 m /s 2.28x1
=0.1411m/s
Discussion The experiment was carried out to determine the characteristic flow of the fluid in the improvised Reynold’s apparatus which is also used to determine the Reynold’ Reynold ’s number for each state of flow.
The above calculations show that the slower the velocity of the fluid is, the lesser is its corresponding Reynold ’s number.
For trial 1, during a 10-second interval of liquid drop off from the apparatus, 290 mL of water-dye solution was collected. This volume was used to calculate the velocity of the fluid. Guided by the equation on how to compute for the Reynold ’s number, a value of 1,015.18 was obtained. Since the value is less than 2,100, the flow is considered laminar. The same applies to trial 2.
For trials 3 and 4, the obtained volumes from the 10-second liquid drop off from the apparatus were relatively higher compared to trials 1 and 2. These volumes indicate faster velocity thus resulting to a higher Reynold ’s number. The calculated N Re values for trials 3 and 4 were 2,379.60 and 3,849.58 respectively. Since both values ranges from 2,100 and 4,000, the fluid flow is considered to be transitional. For trials 5 and 6, the velocities of the fluid were much higher compared to the first four set-ups. A Reynold’ Reynold ’s number of 8,223.02 and 11,199.51 were calculated from trials 5 and 6 respectively. Since the values are over 4,000, the fluid flow is considered to be turbulent. V. Conclusio n Laminar flow is the type of fluid flow in which particles move in a straight line in the form of thin parallel sheets. This flow denotes a steady condition where all stream lines follow parallel paths. The dye under this condition remains identifiable as a solid core. The calculated Reynold’ Reynold ’s number for laminar flow is always less than 2,100.
As the velocity is increased, increased, a disturbance disturbance in the flow is created in which the resulting Reynold’ Reynold ’s number may range from 2,100
Gradual increase in volumetric flowrates gradually influences the Reynold ’s number as well. Fluids with Reynold ’s number greater than 4,000 is considered turbulent. Turbulent flow denotes unsteady conditions where streamlines interact causing shear plans to collapse and mixing occurs. VI. Recommendation To further enhance the study, it is recommended for future researchers to install a functional pump which will regulate the volumetric flow rate of fluid in the apparatus. The amount of water and dye should also be controlled and continuously supplied to obtain accurate results for all set-ups.
VII. VII. Appendix
A. Reynol Reyn ol d ’s Apparatus
B. Laminar Flow
C. Turbulent Flow
D. Transiti Transiti onal Flow Flow
