1.0 OBJECTIVES The objectives of this experiment are: 1) To understand the effect of the static pressure by demonstrating demonstrating the various items of pressure measuring equipment. 2) To understand the effect of static pressure press ure by studying the relationship between intensity of liquid pressure and depth. 3) To understand the effect of static pressure press ure by measuring changes in liquid level.
2.0 THEORITICAL BACKGROUND Using the HM 115 hydrostatic bench, many type of experiment in the field of hydrostatics of liquid and gases can be performed. It was designed to demonstrate the properties and behaviour of fluid under hydrostatic condition(At rest). This allowed the understanding of a wide range of fundamental principle and technique to student before studying fluid in motion.
If a force F presses evenly on a surface A, the pressure acting on that s urface is:
P=
Pressure p is always measured in bar:
1 bar= 10
The unit Pa (Pascal) is frequently used due to reason of mathematical simplification reasons. Example 1 bar = 100000 Pa or 1mBar = 1hPa In a vessel filled with liquid the pressure rise evenly from the top to the bottom that also the side pressure. The highest pressure prevails at the bottom. It is dependent on the height, h of
the liquid of the level above the bottom of the vessel and the density, ρ of the liquid. Thus hydrostatic pressure are not constant is can varies The hydrostatic pressure is calculated as :P= h.ρ.g
(g= 9.81
Liquid ( such as water ) cannot normally can be compressed vice versa to gasses that can be compressed Boyle-Mariotte’s Law state that as volume increase when the pressure is decrease with constant temperature P . V = constant
(1)
The law applies at constant temperature. Accordingly, for two different states in the measurement vessel: Pi . Vi= Pf . Vf
(2)
For this experiment V iis the residual volume of air in the small measuring vessel (diameter, d) at any two point in time I = 2 and I = 2. Thus: Vi=
(3)
Applied in (1) consequently:P1 . Z1= P1 . Z2 It should be noted that the pressure
displayed on the measured values. When these
pressure are plotted over the height of the air column , a hyperbola is produced, with semi-logarithmic sealing a straight line.
The application of hydrostatic force: 1-Use in pipe line as is use to testing and determine the integrity of pipe line 2-Use as trigger mechanism in Depth Charge a underwater explosion, as the bomb sink in the water the pressure of water trigger the bom to explode due to pressure The application of Boyle-Mariotte’s Law: 1-Use in calculating the volume and pressure of internal combustion of engine and steam engine to know how much the power produce 2-Action of a syringe when fluid draws out from syringe the volume increase as the pressure is decrease
3.0 APPARATUS
4.0 EXPERIMENTAL PROCEDURE
Part A: Experimental to measure the measure the hydrostatic pressure of water
The diameter (d) = 133mm measuring vessel (9) was used for measured, to which at the bottom were attached to pressure sensor. The switch box (3) (unit:mbar) were displayed the reading of hydrostatic pressure Preparing the water circuit:-
1. Cocks (20),(22),(24) was opened, cocks (21) was opened 2. The upper vent valve on measuring vessel (9) was opened 3. The immersion pump was switched on by pressed the green knob on the switch
box(3). 4. The inlet cock (20) was opened carefully so that water can be let into the
measuring vessel. 5. The pressure indicated on the switch box was compared with the water level on
the measuring cylinder.
Draining the system:
The measuring pump was switched off by pressing the red knob on switch box (3)
Inlet cock (20) was closed, all other cocks and vent valves was opened. The water runs back into the tank.
Part B: Experiment Relating to Boyle-Mariotte’s Law.
Preparing the system: 1. Cocks (20) and (22) was opened, cocks (21), (23) and (24) were closed. 2. The vent valve on the small measuring cylinder were closed, the vent valve on the
larger vessel (13) were opened. 3. The immersion was switched on by pressing the green knob on the switch box (3).
Water was flow into larger measuring cylinder. 4. A cock (22) was closed when the water level had reached a height of approximated
15-20 cm. The immersion pump was closed by pressing the red knob on the switch box. 5. Cocks (23) was open the water flows into the small measuring cylinder. Because there
is still air in small measuring the water level were not equal. 6.
The compressor was connected via a connecting horse to large measuring (25).
7. The compressor was switch on. The pressure in the small vessel was rising
(manometer 15), at the sane times water level in the small vessel was rises, as the air was compressed 8. Measurement was taken while its happening
= Height of the air column in small vessel. = Air pressure on manometer (15)
Draining the system:- Vent valve was closed on the large measuring vessel (13) and all
other cocks and vent valve were opened.
5.0 DATA AND CALCULATION
Water Level(cm)
Pressure(mbar)
Theoretical Pressure(mbar)
5
5.6
4.91
10
10.2
9.81
15
15.3
14.72
20
20.2
19.62
25
25.2
24.53
30
30.1
29.43
35
34.9
34.34
40
40
39.24
Diagram 5.0: Table shows the water level and pressure that been obtained and recorded.
i
Pim (bar)
Pi (bar)
Zi(cm)
Pi.Zi(cm.bar)
1 2 3 4 5 6 7
40.60 36.00 31.60 27.40 23.20 19.40 17.40
41.60 37.00 32.60 28.40 24.20 20.40 18.40
0.10 0.25 0.40 0.60 0.90 1.25 1.50
4.16 9.25 13.04 17.04 21.78 25.50 27.60
Diagram 5.1:Table shows the height of air column in small vessel,Zi and Air pressure on manometer,Pim that been obtained.
Result:
45.0
Graph Of Pressure of air,Pi against Height of air column,Zi
40.0
35.0
30.0
25.0
Pi(bar) 20.0
15.0 y = -16.029x + 40.392 10.0
5.0
0.0 0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Zi (cm)
Diagram 5.2: Curves Pressure of air(Pi) in bar a gainst Height of air column,Zi(cm)
1.6
Sample Calculation
(For Part A) mbar
pa
-To calculate hydrostatic pressure (theoretical): 1 mbar = 100 pa
P= ρgh
(g= 9.81 / ) (ρ= 1000⁄) ᵐ
When water level = 5cm Pressure = 5.5 mbar
P=
(((
P = 4.91 mbar #
-To calculate Percentage Error
%
(For Part B)
Pi = Pim + Pamb Pi = Pressure of air in bar Pim = Air pressure on manometer Pamb = atmospheric pressure (1 bar)
When Pim = 40.6bar
Pi = 40.6 + 1 Pi = 41.6 bar
Pi.Zi Pi = Pressure of air in bar Zi = Height of air column
When Pi = 41.6 bar, Zi = 0.10 cm Pi.Zi = (41.6) × ( 0.10) Pi.Zi = 4.16 cm.bar
