Reynolds Number Group2

REYNOLD’S NUMBER

DETERMINATION

Caraan, Zaila Marie R. Cruzat, Jayrick V.

Magpantay, Vanessa M.

Submitted to:

Engr. Rejie C.Magnaye (Instructor)

I.Introduction

In fluid mechanics, a criterion of whether fluid (liquid or gas) flow is absolutely steady (streamlined, or laminar) or on the average steady with small unsteady fluctuations (turbulent). Whenever the Reynolds number is less than about 2,000, flow in a pipe is generally laminar, whereas, at values greater than 2,000, flow is usually turbulent. Actually, the transition between laminar and turbulent flow occurs not at a specific value of the Reynolds number but in a range usually beginning between 1,000 to 2,000 and extending upward to between 3,000 and 5,000.

In 1883 Osborne Reynolds, a British engineer and physicist, demonstrated that the transition from laminar to turbulent flow in a pipe depends upon the value of a mathematical quantity equal to the average velocity of flow times the diameter of the tube times the mass density of the fluid divided by its absolute viscosity. This mathematical quantity, a pure number without dimensions, became known as the Reynolds number and was subsequently applied to other types of flow that are completely enclosed or that involve a moving object completely immersed in a fluid. Studies have shown that the transition from laminar to turbulent flow in tubes is not only a function of velocity but also of density and viscosity of the fluid flow in the tube. These variables are combined into the Reynolds number, which is dimensionless. Reynolds number can be calculated by the equation,

Where:

is the density of the fluid (kg/m3) is a characteristic linear dimension,

(travelled length of the fluid; hydraulic diameter when dealing with river systems) (m)

is the mean velocity of the object relative to the fluid (SI units: m/s) is the dynamic viscosity of the fluid (Pa•s or N•s/m² or kg/(m•s)) is the kinematic viscosity (ν = μ / ρ) (m²/s)

II.Objectives:

1.) To determine the Reynolds’ number for the different types of flow of fluids.

2.) To describe the operation of Reynold’s Number Determination setup and the importance of its application.

3.) To describe the effect of pressure on volumetric flow rate, the type of flow regime manifested and the Reynold’s number.

4.) To determine what pressure can achieve laminar, transition and turbulent type of flow regime.

5.) To distinguish if the Reynold’s number computed tally to the flow regime manifested on dye behavior.

III.Materials and Equipment

Stopwatch Dye solution

Graduated Cylinder (1L) Reynold’s Apparatus

Receiving Basin with Volume Measurement Gradient on the Side IV.Methodology and Procedure

1.) Prepare the dye solution and the manometer fluid solution composed of tinge of iodine in chloroform.

2.) Fill with water the overhead tank and receiving tank together with the glass tube. Make sure no bubbles formed.

3.) Calibrate the fluid inside the manometer to a pressure of 2inHg By adjusting the metal gradients.

4.) Open the plug cock for the discharge of pipe. Observe and Note the nature of flow from the filament.

5.) Collect the water from the discharge pipe in a 1L graduated cylinder. Record the time till the graduated cylinder was filled with water. Then close the valve

afterwards.

6.) Repeat procedure four and five for three trials.

7.) Repeat procedure three to six with pressure of 4inHg, 6inHg, and 8inHg. V.Presentation of Results

Pressure (inHg)

Trials (Duration in sec) Averag e Volumetric Flowrate (m3_/sec) 10-5 Velocity (m/s) Reynold’s Number (NRe) Type of Flow 1 2 3 2 20.72 20.53 20.82 20.69 4.8333 0.0385 1716.44 Laminar 4 14.59 15.11 14.81 14.84 6.7385 0.0536 2393.06 Transition 6 12.57 12.10 11.98 12.22 8.1833 0.0651 2906.14 Transition 8 11.10 10.68 10.98 10.92 9.1575 0.0729 3252.11 Transition Computations @ 250_C

= 0.8937x10-3 _{Pa-sec Diameter= 40mm (0.04m)}

VI. Analysis and Evaluation

VII. Conclusion and Recommendation.

The major factors affecting the fluid flow is fluid velocity and viscosity. At low velocities fluid flow is laminar, and the fluid can be pictured as a series of parallel layers, or lamina, moving at different velocities. The fluid friction between these layers gives rise to viscosity. The viscous stresses within a fluid tend to stabilize and organize the flow. Thus, as the fluid becomes viscous, the flow becomes laminar. On the other hand, as the fluid flows more rapidly, it reaches a velocity, known as the critical velocity, at which the motion changes from laminar to turbulent, with the formation of eddy currents and vortices that disturb the flow. This

is due to the fluid inertia that tends to disrupt organized flow leading to chaotic turbulent behavior.

The behavior of the fluid flow is quantified by the Reynolds number.

Reynolds number is defined as the ratio of inertial and viscous force to characterize the types off low patterns. With increase in flow velocity, the initial forces increase so as the Reynolds Number. The Reynolds number is significant in the design of a model of any system in which the effect of viscosity is important in controlling the velocities or the flow pattern.

VIII. References

Foust, Alan s. et.al. (1980), Principles in Unit Operations, 2nd edition, Canada: John Wiley and Sons.

Geankoplis, Christi J. (1995), Transport Processes and Unit Operations, 3rd edition, Singapore: Prentice Hall International Inc.

McCabe, Warren L.; Julian C. Smith, and Peter Harriot (1993), Unit Operations of

Chemical Engineering, 5th edition, New York: McGraw Hill Inc.

Perry, Robert H. and Don W. Green (1997), Perry’s Chemical Engineer’s

Handbook, 7th edition, USA: McGraw Hill Co., Inc.

Reynolds number (physics) -- Britannica Online Encyclopedia. 2012. Reynolds

number (physics) -- Britannica Online Encyclopedia. [ONLINE] Available at: