EXP 7 Body

EXP 7: CALIBRATION OF WATER TANK AND WATER METER

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EXPERIMENT 7

CALIBRATION OF WATER TANK AND WATER METER

OBJECTIVES:

To be able to compare the volume of the water by measurement and by weight.

To be able to exercise and enhance knowledge on measuring and computing

pressure including its relation with the other parameters such as height density

and gravitational acceleration guided by the equation P=𝜌𝑔ℎ.

To learn how to read the readings on the water meter.

THEORY/HYPOTHESIS:

Volume tank for liquids ranges in sizes from the large cylindrical steel tanks

holding several thousand gallons down to the calibrated “cubic-foot bottles” and the

chemist’s burettes and graduates. Many types of gages and devices are used to

indicate the liquid level, such as floats, linkages, gage-glass scales, and hook gages.

Physical tank calibration or “wet” calibrating involves the measuring of the actual

volumetric capacity of the vessel. This measurement must be precisely correlated to

depth so that a pressure/depth/volume table can be generated for the specific tank

geometry.

A weighted-water calibration is usually the most accurate, and this is done by

introducing water into the tank to be calibrated in carefully weighted amounts, observing

the water temperature. Critical to this procedure is the accuracy of the measuring

devices employed. A precision volume container or calibrator (calibration can) is

recommended. This volume measure should be certified and traceable to NIST

(formerly NBS) standards or through state bureau of weights and measures (USA).

The volume of most liquids, including water, is dynamic with temperature. Since

the objective of the calibration procedure is to determine a precise volume profile of the

tank, volume must be standardized to temperature; this requires a fairly accurate

temperature measurement of the water being used in the calibration process.

Temperature should be measured both at the beginning and at the end of the process.

Cool water (40-60°F) is best used in calibration, never use hot water for a tank

calibration.

Measurements of fluid-flow quantities, both rates and velocities, are frequently

required in engineering. Many methods are available for such measurements, and the

engineer should know the advantages and limitations of several common methods. A

flow meter can also be used for tank calibrations. However, it should be noted that flow

meters are most accurate when flow rates remain relatively constant. In some

instances, a throttling valve should be employed to help maintain this constant flow rate.

Flow-measuring devices generally fall into one of two categories: quantity meters

and rate meters. The distinction between the two is based on the character of the

primary element, i.e., the element that interacts with the fluid. The secondary element

translates the interaction into numbers and indicates or records the values. Quantity


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measurements, by mass or volume, are usually accomplished by counting successive

isolated portions, whereas rate measurements are inferred from the effects of flow rate

on pressure, force, heat transfer, flow area, etc. it is frequently possible to obtain the

rate of flow from a quantity meter by a suitable choice of the secondary element.

Orifices, nozzles, and venturis are by far the most common flowmeters for use in

closed conduits. The measured differential pressure results from a conversion between

static and velocity pressure, for the most part, and can be calculated by the steady-flow

energy equation.

For ease of analysis, the fluid properties, system geometry, and flow

characteristics are simplified by assumption and the actual deviations are accounted for

with correction factors. In particular, the fluid is assumed to be incompressible (constant

density); the flow area upstream from the metering element is assumed to be large

enough so that the velocity is negligible; the effect of elevation changes are assumed to

be negligible; and the flow is assumed to be steady, one-dimensional (uniform velocity

profiles, adiabatic, and to have no shaft work exchange with its surroundings.

Figure 1: Sample Set up

The following equations may be used in this experiment:

1. Mass Density of water, w

ww

V

m

2. Weight Density or Specific Weight of water, w

ww

V

W


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3. Specific Volume of water,w

ww

m

V , (can also be determined from the steam table

using the temperature.

LIST OF APPARATUS

1. Water tank / drum – Used for

storing water and other related

liquid.

2. Platform Balance - a platform

balance is a form of equal-arm

balance in which two flat

platforms are attached to the top

side of the beam, one at each

end. The weight of an object is

found using the equilibrium of

forces.

3. Set of Counter Weights- A

counterweight is an equivalent

counterbalancing weight that

balances a load. Counterweights

are often used in traction lifts

(elevators), cranes and funfair

rides.

https://www.google.com.ph/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCPPS4LLW6McCFQwKjgod3asJPg&url=http://www.qualityamust.com.au/water-tanks.html&bvm=bv.102022582,d.c2E&psig=AFQjCNHs4FXaitszubMxZXd_MFxWmABP9g&ust=1441844181686139

http://www.wisegeek.org/what-is-a-platform-balance.htm


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4. Water Meter- Used for measuring

the volume of water flowing

across a specific fluid flow path.

5. Steel Tape/Meter Stick- A meter

stick is a large ruler used for

measuring size or distance using

the metric scale.

PROCEDURE

Volume Measurement

1. Measure the tare weight of the steel drum as well as its diameter and height.

2. Get the initial reading of the water meter connected from the water supply line.

3. For trial 1, fill up the drum at a certain level and get the final reading of the

water meter.

4. Measure the height of water inside the drum and get the weight using the

platform balance.

5. Calculate the volume by measurement and volume by weight and compare

them with that of the water meter reading.

6. For trial 2, repeat the procedure no. 2 and add water to the drum up to the

desired second level.

7. Obtain the final reading of the water meter.

https://www.google.com.ph/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCIK7vf3W6McCFYdzjgod_vwDQQ&url=http://www.omega.com/pptst/FTB8000B.html&bvm=bv.102022582,d.c2E&psig=AFQjCNGgDl1Y6aFUxdfY99D-a5--mIBvog&ust=1441844354248418

https://www.google.com.ph/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCLDSt7rX6McCFQwajgodt8IErA&url=http://www.enasco.com/product/SB12163M/&bvm=bv.102022582,d.c2E&psig=AFQjCNGSBTD4ImW-LQArHycoOXMqAx8hSQ&ust=1441844495268563


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8. For the rest of the trials, repeat the above procedures as indicated in the data

sheet.

SET-UP OF APPARATUS

A. Determination of Volume by Water Meter

The volume of water was set to 36L by recording the initial reading on the meter.

The flow of water was stopped when the difference between the final and initial reading

is already 36.

B. Determination of Volume by Weight

The weight of the tank was first recorded. The volume of water was computed by

dividing its mass by its density.

C. Determination of Volume by Measurement

The diameter of the tank and height of the water at a reference point were

recorded. The volume of the water in the tank was computed using these dimensions.


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FINAL DATA SHEET

By Meter By Weight By Measurement

TRIAL I.R F.R Volume(L) I.R F.R Volume(L) % Difference I.R F.R Volume(L) % Difference

1 525 561 36 17.2 52.8 33.1 8.06 0 0.13 32.6 9.44

2 561 597 36 52.8 86.6 33.8 6.11 0.13 0.265 33.84 6

3 597 633 36 86.6 119.8 33.2 7.78 0.265 0.4 33.85 5.97

4 633 669 36 119.8 156.6 36.8 2.22 0.4 0.535 33.84 6

5 669 705 36 156.6 191.4 34.8 3.33 0.535 0.675 35.11 2.47

Tare Weight = __17.2 kg___ Diameter of Drum = __0.565 m__

Tank Calibration:

1 inch = 6.37 L

1 cm = 2.52 L

1 inch = 6.37 kg

1 cm = 2.52 kg


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SAMPLE COMPUTATION:

BY METER (TRIAL 1):

𝑉𝑜𝑙𝑢𝑚𝑒 = 𝐹𝑖𝑛𝑎𝑙 𝑅𝑒𝑎𝑑𝑖𝑛𝑔 − 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑅𝑒𝑎𝑑𝑖𝑛𝑔

𝑉𝑜𝑙𝑢𝑚𝑒 = 561 𝐿 − 525 𝐿

𝑽𝒐𝒍𝒖𝒎𝒆 = 𝟑𝟔 𝑳

BY WEIGHT (TRIAL 1):

Volume

𝑚𝑤𝑎𝑡𝑒𝑟 = 𝐹𝑖𝑛𝑎𝑙 𝑅𝑒𝑎𝑑𝑖𝑛𝑔 − 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑅𝑒𝑎𝑑𝑖𝑛𝑔

𝑚𝑤𝑎𝑡𝑒𝑟 = 52.8 𝑘𝑔 − 17.2 𝑘𝑔 = 33.1 𝑘𝑔

𝑉𝑜𝑙𝑢𝑚𝑒 = 𝑚𝑤𝑎𝑡𝑒𝑟

𝜌𝑤𝑎𝑡𝑒𝑟=

33.1 𝑘𝑔

1𝑘𝑔

𝐿

= 𝟑𝟑. 𝟏 𝑳

Percent Difference

BY MEASUREMENT (TRIAL 1):

Volume

𝑉𝑜𝑙𝑢𝑚𝑒 = 𝑉𝑐𝑦𝑙𝑖𝑛𝑑𝑒𝑟 = 𝜋𝑑2

4ℎ = 𝜋

(0.565𝑚)2

4(0.13 𝑚) (

1000 𝐿

𝑚3) = 𝟑𝟐. 𝟔 𝑳

Percent Difference

𝑃𝑒𝑟𝑐𝑒𝑛𝑡 𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 =𝐴𝑐𝑡𝑢𝑎𝑙 − 𝐸𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙

𝐴𝑐𝑡𝑢𝑎𝑙𝑥 100% =

36 − 32.6

36 𝑥 100 % = 𝟗. 𝟒𝟒%

𝑃𝑒𝑟𝑐𝑒𝑛𝑡 𝐷𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 =𝐴𝑐𝑡𝑢𝑎𝑙 − 𝐸𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙

𝐴𝑐𝑡𝑢𝑎𝑙𝑥 100% =

36 − 33.1

36 𝑥 100 % = 𝟖. 𝟎𝟔%


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CALIBRATION

1 inch

𝑚 = 𝑉ρ =𝜋

4𝐷2ℎρ =

𝜋

4(0.565𝑚)2(1 𝑖𝑛𝑐ℎ) (

2.54100 𝑚

1𝑖𝑛𝑐ℎ) (

1000kg

m3) = 𝟔. 𝟑𝟕 𝐤𝐠

BUT: 1 kg water = 1 L water

6.37 kg = 𝟔. 𝟑𝟕 𝐋

1 cm

𝑚 = 𝑉ρ =𝜋

4𝐷2ℎρ =

𝜋

4(0.565𝑚)2(1 𝑐𝑚) (

1𝑚

100𝑐𝑚) (

1000kg

m3) = 𝟐. 𝟓𝟐 𝐤𝐠 = 𝟐. 𝟓𝟐 𝐋


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TEST DATA ANALYSIS

The chart above shows the results for the measurement of the volume of water

added on the water tank per trial. The blue line shows the actual reading of the water

meter (which is 36L per trial). The orange line shows the measured volume using the

change in weight of the water drum and the gray line portrays the result using the

change in height. According to the data, all of the data found in each trial has a lower

result as compared to the actual value. This can be due to the error that the group didn’t

consider the water left on the hose when the water is being poured to the tank. Also,

another possibility is that the meter itself can be inaccurate. This can be proven by the

fact that the data gathered for both measurement by weight and height are almost the

same per trial.

36 36 36 36 36

33.1

33.8

33.2

35.8

34.8

32.6

33.84 33.85 33.84

35.11

30

31

32

33

34

35

36

37

Trial 1 Trial 2 Trial 3 Trial 4 Trial 5

Actual (L)

By Weight (L)

By Measurement (L)


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The figure above shows the computed calibration for the given water tank in the

institute. This implies that per 1 inch change in height of water level, the tank gains 6.37

L and per 1 cm increase in water level, there is an increase of 2.52 L of water in the

tank. For water, 1L = 1 kg, therefore, the calibration is the same.


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DISCUSSION

The experiment is all about calibration of water tanks through measurement of volume

of tanks. This experiment employed the use of various methods in volume

measurement. These methods include measurement of volume by the use of water

meter, measurement of volume by weighing water sample and measurement of volume

of the container. Moreover, we compared and contrast the validity and accuracy of the

yield results of each method.

Initially, we measured the basic dimensions of the tank. We measure the

diameter and then the height of the tank. We place the tank at the platform balance and

filled the tank with sufficient amount of water.

In the measurement of volume by the use of water meter, we observed the

following, the water meter continuously register reading as the water flows. The

difference in the reading between the final and initial registered reading is the volume of

the tank water. This method is the most accurate method of measuring the volume of

tanks since the water is directly routed to a device which directly measures the volume

of water passing. Knowledge of how to read the water meter is important. The last red

digits indicate volumes in liters while the first black digits represent the measurement in

cubic meters. When the reading is in between the two numbers, choose the number that

already passed the indicator. As what our professor have said, the encoder of the water

companies that visit our homes every month only reads the values that passed already

the indicator.

(LEFT) Measuring the

diameter. (RIGHT) Measure

the height of the tank.


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In the measurement of volume by weight, I realized that the result of the readings

is inconsistent since the platform balance deviates in reading as the load applied is

increased. The level of the platform balance should also be observed because the

weight of the tank may not be leveled and not on the center that causes the percent

difference. As we have learned in the previous experiment, the analog or the

conventional platform balance is not very accurate but we use this because it can carry

and measure heavier load than the digital platform balance. Moreover, the calculations

are also inconsistent since the temperature factor was not applied in the experiment.

This inconsideration accounted for a slight difference from the conventional reading.

Remember, the density of water changes with temperature. In the calculations I used 1

kg/L.

In the volume measurement by dimension, we noted

the following observations. The accuracy of the

measurement is the basis for acceptable results. The height

reading is taken by measuring the distance from the bottom

of the drum to the surface of the water. I realized that the

procedure that we did causes an error on the data that we

have gathered. This is because when we submerge the

meter stick I the water, it occupies space in the water which

adds another volume to the water and causes the water to

rise. There is already an error that acquired.

Tank Calibration is the process of accurately determining the capacity or partial

capacities of a tank and expressing this capacity as a volume for a given linear

increment or height of liquid. In other words tank calibration also means measuring

storage tanks, horizontal bullets, spherical tanks, vats, casks, barges, ship tanks and

liquid bulk containers. These measurements provide the necessary dimensions for

calculation of calibration charts.

Submerging the meter stick

in the water gave a

difference in the values.


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At its simplest, a calibration of any vessel requires knowledge of the nominal

dimensions of the vessel from which the volume may be calculated. For a water tank

this may be enough and you probably will not need to call in a specialist tank calibrator.

At the other end of the scale, if you are selling a product on the basis of tank

levels, a tank can be measured precisely and calculations can be made to take into

account factors such as hydrostatic expansion of the tank during filling and thermal

expansion of the tank shell in service.

A flow meter can also be used for tank calibrations. However, it should be noted

that flow meters are most accurate when flow rates remain relatively constant. In some

instances, a throttling valve should be employed to help maintain this constant flow rate.

Generally, water should only be metered out of the tank. This avoids any

problems that can occur with fluctuations in supply pressure during tank filling. The

changing differential between water supply pressure and backpressure due to

increasing depth will cause the effective flow rate to vary. This relationship is difficult to

predict if water supply pressure fluctuates during the procedure.

A throttle valve (if used) would be used to gently restrict the flow of water out of

the tank when beginning the process. As depth in the tank decreased, the valve could

be slowly opened more fully to maintain relatively constant flow. (Because the

hydrostatic pressure pushing water out of the tank is reduced as depth decreases, the

throttle valve helps to equalize the flow rate.)

It will still be helpful to utilize some type of volumetric standard even when

metering is employed. It can be used to prove the meter’s functional accuracy. A

calibrator or volume standard is especially

recommended for measuring the final draw-offs

from the tank or for a fill-back procedure.

Water metering is the process of

measuring water use. In many developed

countries water meters are used to measure the

Water meter in residential houses


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volume of water used by residential and commercial building that are supplied with

water by a public water supply system. Water meters can also be used at the water

source, well, or throughout a water system to determine flow through that portion of the

system. In most of the world water meters measure flow in Cubic meters (m3) or litters

but in the USA and some other countries water meters are calibrated in cubic feet (ft.3),

or US gallons on a mechanical or electronic register. Some electronic meter registers

can display rate-of-flow in addition to total usage. There are several types of water

meters in common use. Selection is based on different flow measurement methods, the

type of end user, the required flow rates, and accuracy requirements.

3 Types of Water Meters Explained

Among the types of water meters are those that differ in the method used to

measure water volume, and the flow control and measurement devices in the water

meter itself. Learn more about the 4 most common types of water meters below.

Type 1 - Displacement Water Meters

Displacement water meters measure how much water occupies a given space

over a preset time. The water flow displaces the measuring device according to the

volume of water in either gallons or cubic feet that passes through the meter. A piston or

a mutating disk controls the movement of a magnet that activates the water volume

register.

Type 2 - Positive Displacement Meters

Positive displacement meters or PD meters are the most common water meters

for homes and small businesses. They can measure small volumes of water at low flow

rates to a high degree of accuracy. The water pipes in displacement water meters range

from as small as 5/8 inch up to 2 inches in diameter. A displacement meter is made of

brass, high-impact plastic and stainless steel. The measurement register consists of a

clear plastic bubble over the odometer-type or LCD display gauge. For measurements

of less than 1/10 of a gallon, a sweep hand is also used on the measurement register.


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These meters can also be installed in separate units of a condominium or apartment to

track individual water usage.

Type 3 - Velocity Meters

The speed at which the water moves is measured by velocity water meters. The

velocity through the meter's specific volume is measured and converted to units of

volume, either gallons or cubic feet. These meters can be calibrated to adjust the

accuracy of their measurement.

Types of Velocity-Based Water Meters

1. Single and Multiple-Jet Water Meters

Single and multiple-jet water meters use velocity to measure water volume. The

water flow turns an impeller which rotates at a known speed compared to the water

speed. These meters have internal strainer grids to prevent the jets from clogging with

particles in the water. They are used for low-volume applications as the impellers

cannot withstand high flow rates.

2. Turbine Water Meters

Turbine meters are used for water pipe diameters up to 12 inches across. They

are used for high-volume commercial sites such as factories and large office

complexes, and as control meters for sections of a town or city. Fire hydrant water

meters are also of this type.

3. Compound Water Meters

In circumstances where water flow can vary from high velocity to low, a

compound meter can accurately measure water usage. These have two measuring

components and a valve to control the flow rate to each. The turbine meter handles high

flow rates and a multi-jet meter gauges the lowest flow. The utility reader adds the totals

indicated on both meters to determine total water usage.

4. Electromagnetic and Ultrasonic Meters


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A pair of electromagnets can measure water flow in or out of the system in a

"mag meter", based on fluid induction principles. Ultrasonic meters send sound waves

through water to measure its speed, and derive a water volume reading. These are

used in large-volume applications and for fluids other than water.


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QUESTIONS AND ANSWERS:

1. What is the significance of the term “inferential” as applied to flowmeters?

Inferential in flowmeters is associated with the flow of fluid such as a drop

in static pressure at a restriction in a pipe, or the rotation of an impeller or rotor,

rather than measurement of the actual mass flow. Inferential flowmeters do not

measure volume, velocity or mass, but rather measure flow by inferring its value

from other measured parameters. Examples of flowmeter technologies that

measure inferentially include differential pressure (orifices, venturi, nozzles),

target and variable area flowmeters

2. Certain flowmeters are known as “variable head” meters. Explain clearly what is

meant by the designation “variable head”.

The variable head meters work on the principle that a variation of the flow

rate through a constriction with a constant cross-sectional area causes a

pressure drop suffered by the fluid as it flows through the constriction. The

pressure drop is related to the flow rate, and hence variations of the pressure

drop can be used to measure variations in the flow rate. The most common

examples of variable head meters used in industry are the venturi meter and the

orifice meter.

3. What is meant by the “primary element” of certain types of flowmeters?

A primary element is the element of a flow meter that serves to indicate

the quantity or velocity of flow. For example, in the case of an orifice flow meter,

the differential pressure across the orifice plate is the primary flow element. A

turbine meter is equipped with a magnetic pickup that senses the proximity of the

turbine blades as the fluid motion causes the turbine to spin; this pickup is the

primary flow element for a turbine meter. Diaphragm meters and other positive

displacement meters are equipped with a crank shaft, the rotation of which acts

as the primary flow element

4. What is meant by the term “discharge coefficient” of a flowmeter?


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The discharge coefficient is the ratio of the mass flow rate at the discharge

end of the nozzle to that of an ideal nozzle which expands an identical working

fluid from the same initial conditions to the same exit pressures.

5. What is meant by the term “vena contracta”?

It is the area of the contraction of the flow of the water when it is

discharged from an orifice.

6. Give the classification of flow meters.

Flowmeters are classified into many types:

a. Positive Displacement or Vollumetric Flowmeter - measures the volume of the

passing fluid directly by impellers, vanes and gears.

b. Differential pressure Flowmeter – inferentially measures the volume of a

passing fluid by analyzing the pressures and forces acting over the devices.

c. Variable area flow meter – measures the pressure of the fluid by constriction of

the flow area of the fluid.

d. Target or Momentum Flowmeter– measures the internal forces of the fluid

particles by pacing a target plate where fluid forces will act.

h. Ultrasonic Flowmeter – uses the effect of motion of a sound source and its

effect on the frequency of the sound to determine the fluid properties.

h. Thermal Flowmeter - thermal mass flowmeter operates independent of

density, pressure, and viscosity. It obtains thermal reception of the fluid through

receptors.

i. Mass Flow Meter - measure the mass flow rate directly.

7. All volumetric flowmeters that are subjected to high head pressure should be

protected by what type of valve?


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Check valves are one of the best suitable valves that can be used to

protect volumetric flowmeters. A check valve or one-way valve is a mechanical

device, a valve, which normally allows fluid (liquid or gas) to flow through it in

only one direction.

8. Why is it necessary to blow steam after each run when the liquid metered is hot?

Yes. In order to prevent thermal deformation on the meter (which will

cause error in reading the flow of hot liquid), blowing of steam is required. This

ensures that the meter is cool and its components are not thermally stressed.

9. Why is a draw-off connection needed in the piping manifold when installing

volumetric flow meters?

In order to prevent unnecessary wastage of water and interruption of

water supply during the installation of a flowmeter, a draw-off connection is used.

It is simply an alternate route to where flowing water can pass.

10. What is the difference between an orifice and a nozzle?

An orifice is simply a bore or a hole on a fluid reservoir where fluids can

flow out. It is commonly situated below the water level. Meanwhile a nozzle is an

extension with an orifice on its mouth, to where the fluids can flow out. It can be

situated below the fluid level, or above the fluid level (which will require a pump

to operate).


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CONCLUSION For this experiment, the group was given 3 objectives, namely: to compare the

volume of the water by measurement and by weight; to be able to exercise and

enhance knowledge on measuring and computing pressure including its relation with

the other parameters such as height density and gravitational acceleration guided by

the equation P=𝜌𝑔ℎ and to learn how to read the readings on the water meter.

During the course of the activity, the group used to test in order to measure the

volume of water flowing into the tank. It was observed that the results for both

measurement and weight are almost coherent with one another, proving the validity of

the results. Also, the group compared the readings of the water meter with the data

gathered through the tests. According to the data, the reading on the water meter is

much higher compared to what the group has recorded for the first part. Possible

sources of error for this are the inaccuracy on the tests and the flaw of the water meter

itself.

To know the calibration for the water tank, the group made use of the concept

that pressure is dependent on the height of the fluid and gravitational acceleration or P

= 𝜌𝑔ℎ. It was noticed, that when considering water, 1 kg = 1L.


21

RECOMMENDATION

Since the main source of error for this experiment is the inaccuracy of the

students while conducting the test, it is recommended that the procedure to be carefully

instructed by the facilitator.


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REFERENCE

http://www.doityourself.com/stry/3-types-of-water-meters-explained#b

http://www.engineeringtoolbox.com/flow-meters-d_493.html

http://en.wikipedia.org/wiki/Water_metering

https://srac.tamu.edu/index.cfm/event/getFactSheet/whichfactsheet/4/


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PRELIMINARY DATA SHEET

Documents

EXP 7 Body