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Fluid Mechanics Lab
 Experiment no 2 |
2. Viscometer.pptx
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To Determine The Viscosity of Fluid Using Viscometer (Find The Viscosity of SAE-30 Lubrication Oil)
Viscometer:A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid.It is used for those fluids whose viscosity does not change under varying flow conditions.
Rheometers must be used when the viscosity does change with flow conditions.
Viscometers usually work by comparing a stationary object and a fluid flow, or vice versa. Hence, a viscometer could be placed in a fluid flow or moved through a stationary fluid.
The flow must have a Reynolds number in the laminar region in order to record accurate values. The measure of the resistance is taken by measuring the drag resistance during relative motion through the fluid
ØThe viscometer consists of a rotating inner cylinder mounted on a vertical spindle at the top and free at the bottom.
ØThis inner cylinder is hollow and rotates inside another fixed outer cylinder of a larger diameter as shown in Fig.
ØThe space between the outer and inner cylinders is filled with the liquid for which the viscosity is to be measured.
ØThe inner cylinder is rotated by means of a vertically falling weight, which imparts rotational motion to the cylinder by using a pulley and a cord arrangement.
For a given weight, W, the speed of rotation of the inner cylinder is higher when the viscosity of the fluid is lower and vice versa.
Apparatus: Viscometer
Procedure: 1. Insert the fluid in the outer cylinder of unknown viscosity.
2. Attach the first weight (W = 100 grams) to the cord. This weight is the sum of the weight of the pan and the weight in the pan.
3. Release the brake and measure the time elapsed to hit the ground.
4. Note the distance covered by the pan.
5. Repeat the above procedure for the other four weights.
6. The viscosity of the fluid is now the average of the five values obtained from the above steps.
2. Attach the first weight (W = 100 grams) to the cord. This weight is the sum of the weight of the pan and the weight in the pan.
3. Release the brake and measure the time elapsed to hit the ground.
4. Note the distance covered by the pan.
5. Repeat the above procedure for the other four weights.
6. The viscosity of the fluid is now the average of the five values obtained from the above steps.
Fluid Mechanics Lab
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| Bourden Tube Experiment |
1. Dead Weight Calibrator.pptx
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To Calibrate a Bourdon Type Pressure Gauge Using a Dead Weight Pressure Gauge Calibrator
Theoretical Background
1. Calibration: To check error with comparison to some standard device is called calibration.
2. Absolute Pressure (Pabs): The pressure that is taken with reference to absolute zero is called absolute pressure, and at absolute zero there is a perfect vacuum.
3. Gauge Pressure (Pg): The pressure that is taken with reference to atmospheric pressure is called gauge pressure. It may be positive or negative depending upon whether we take (Pg) above the atmospheric pressure or below the atmospheric pressure. Gauge pressure is always measured with atmospheric pressure, that is why when gauge pressure is at atmospheric pressure it results zero.
Pabs = Patm + Pgau
Bourdon Tube Pressure Gauge:
uThe bourdon tube pressure gauge is the most common type used to measure fluid pressure because it is reliable, inexpensive and relatively simple.
uThe bourdon tube is a curved tube closed at one end, which is attached to a spring-loaded mechanism that is itself attached to the gauge’s needle.
uThe port of the gauge is attached to the location in the system where you’re measuring pressure.
As pressure increases within the bourdon tube, the metal tube starts to straighten, and as it does, it tugs on the lever attached to the needle.
Apparatus: Dead Weight Tester
Procedure:
1. Remove the piston from unit.2. Close valve V1 and open valve V2.
3. Fill cylinder with oil.
4. Now close valve V2.
5. Put piston back in position with V1 and V2 in close position.
6. Read out pressure value on gauge and compare it with theoretical results.
7. Repeat the experiment by adding weights.
Hitec Mechanical Engineering
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