The TecEquipment Ltd 1999

The TecEquipment Ltd 1999 (Model H10) is designed to measure flow of an incompressible fluid. From this experiment, we will obtain the flow rate measurement and compare it with measured pressure drop by utilising three basic types of flow measuring techniques; rotameter, venturi meter and an orifice meter.

Actual flow rates for the water were determined by measuring the time taken for water to fill (weigh tank method) to 10L for each experiment. The coefficient of discharge; Cd was calculated for the venturi and orifice and displayed on a graph (the equation of the line will show the Cd. The flowmeters were then compared using the graphical representations of the results.

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The results of head loss against the actual flowrate; Q showed that the venturi meter had a much lower head loss from the flow than the orifice meter and rotameter.

In conclusion, the orifice meter as a device is much simpler to make and use, for it is comparatively easy to manufacture a suitable orifice plate and insert between two existing flanges on a pipe. By contrast, the venturi meter is large, comparatively difficult to manufacture and complicated to fit into an existing pipe network. But, the low head low associated with the controlled expansion occurring in the venturi meter gives it an obvious superiority in applications where power to overcome flow losses may be limiting.

The rotameter is the easiest to determine the discharge requiring only the sighting of the float and reading of the calibration curve. However, the energy losses were significantly higher than the venturi and orifice meters. This high energy loss is due to the large drop in pressure due to friction. It does need to be chosen carefully to make sure that the associated head loss is not excessive.

Our experiment overall was successful as we had achieved the objectives of the task.

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Introduction

The TecEquipment H10 Flow Measurement apparatus is designed to measure the discharge of an incompressible fluid, whilst giving applications of the Steady-Flow Energy Equation and Bernoulli’s equation. The discharge is determined using a venturi meter, an orifice plate meter and a rotameter.
Objective

Experimentation and calculation will be carried out to determine the following:

Determine the flow rate from the rotameter using the value taken from the rotameter in cm and converting it to L/min. A calibration graph will be created and the flow rates manually read.

Determination of Cd for the Venturi and Orifice meters by experimentation and graph creation. Gradient = Cd

A comparison of calculated flow measurement (discharge) Q using venturi, orifice, rotameter against the weigh bench flow rate. This will be displayed graphically.

A comparison of head loss across the venturi, orifice, rotameter against the actual volumetric flowrate as measured by the weigh bench. This will be displayed graphically

A final discussion comparing the 3 meters to highlight the advantages and disadvantages of them all.

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Theory

In this experiment, the ability to operate flow measuring equipment (Rotameter, Venturi and Orifice meters) for Cd comparison from each piece of equipment will be performed. Measuring the flow rate is an important aspect in all industries and there are several ways of measure the flow of fluids in pipework
The steady-flow energy equation

Figure 1: Graphical representation of the steady flow equation.

For steady, adiabatic flow of an incompressible fluid along a stream tube, as shown in Fig. 1 Bernoulli’s equation can be written in the form;
P_1/?g+(¯V_1^2)/2g+z_1=P_2/?g+(¯V_2^2)/2g+z_2+??H?_(Loss(12))

Where,
P/?g = the hydrostatic head.

¯V^2/2g = the kinetic head (¯V is the mean velocity i.e. the ratio of volumetric discharge to cross-sectional area of tube).

z = the potential head

P/?g+¯V^2/2g+z Represents the total head.
The head loss ?H_(Loss(12)) arises because of vortices in the stream caused by the flow being viscous therefore, a wall shear stress exists and pressure forces must be applied to overcome it. The increase in flow work required appears as increased internal energy. Also, because the flow is viscous the velocity profile at any section is non-uniform.
The kinetic energy per unit mass at any section is then greater than V2/2g and Bernoulli’s equation incorrectly assesses this term. The fluid mechanics entailed in all but the very simplest internal flow problems is too complex so, head loss, ?H must be obtained by experimental means.
A contraction of stream boundaries can be shown (incompressible fluids only) to increase flow uniformity and, conversely, as boundaries diverge flow becomes less uniform and so the corresponding, ?H increases. , ?H is typically negligible between the ends of a contracting duct i.e. a venturi meter but, is normally significant when the duct walls diverge as in an orifice meter.
Rotameter

The rotameter is a flow meter in which a rotating free float is the indicating element. The rotameter consists of a transparent tapered vertical tube through which fluid flows upwards. Within the tube is placed a freely suspended “float” of plumb bob shape. When there is no flow, the float rests on a stop at the bottom end. As flow commences, the float rises until upward on it are balanced by its weight. The float rises only a short distance if the flow rate is small and increasing distances with increasing flow. The points of equilibrium can be noted as a function of flow rate. With a well-calibrated marked glass tube, the level of the float becomes a direct measure of flow rate.

Fig. 2 Rotameter – The rotameter’s operating principle is based on a float of given density’s establishing an equilibrium position where, with a given flow rate, the upward force of the flowing fluid equals the downward force of gravity. It does this, for example, by rising in the tapered tube with an increase in flow until the increased annular area around it creates a new equilibrium position. By design, the rotameter operates in accordance with formula for all variable-area meters, directly relating flow rate to area for flow (www.omega.com).

Rotameters must be mounted vertically and as such flow through them experiences a change in height as well as a potential pressure differential. The bottom of the tube is narrow and gets wider as the top is reached. The flow originates from the bottom and moves the rotameter’s float up to the position in which the weight of the float balances the force exerted by the flow. If the flow remains lower than that of the speed of sound, then the incompressible Bernoulli’s equation can be applied as a balance on the rotameter system.
C=V^2/2g+z+p/?g

In this equation:

g = gravitational acceleration
V = velocity of the fluid
z = height above an arbitrary origin
C = constant along any streamline in the flow but varies from streamline to streamline. A streamline is defined as a path in a steady flow field along which a given fluid particle travels

Then equate for points at bottom (h) and top (i) of the float:

1/2 ??V_i?^2-1/2 ??V_h?^2+?gz_i-?gz_h= p_i-p_h

This again, simplifies to:

?p= ?gh_f+1/2 ??V_h?^2 1-V_i/V_h ^2

Where, hf = the height of the float.

The volumetric flow rate; Q is the same at the top and the bottom of the float, the continuity equation can be written as:

Q=V_h A_h=V_i A_i

Where, V = the volumetric flow and,
A = the area

Solving for volumetric flow at b to get:

V_i=V_i (A_i/A_h )=Q/A_i

Substituting this value of simplified Bernoulli’s equation yields:

?p= ?gh_f+1/2 ?(Q/A_i )^2 1-(A_i/A_h )^2

Solving for Q:
?p-?gh_f = 1/2 ?(Q/A_i )^2 1-(A_i/A_h )^2

(?p-?gh_f)/1-(A_i/A_h )^2 = 1/2?(Q/A_i )^2

2(?p-?gh_f )/?1-(A_i/A_h )^2 = ?(Q/A_i )^2

(Q/A_i )^2=2(?p-?gh_f )/?1-(A_i/A_h )^2

Get Q by itself

Q=??(2(?p-?gh_f )/?1-(A_i/A_h )^2 )? A_i

From this a calibration graph can be created so that flow can be determined by reading from the scale on the apparatus itself and reading the flowrate from this data. (www.omega.com)(www.lmnoeng.com)(www.test-and-measurement-world.com, 2016)

NB: This theory is for background only as data for internal dimensions of the rotameter have not been given within the working instructions for the H10 hydraulic bench flowmeter equipment.

Venturi Meter

The venturi meter has a converging cone inlet, a cylindrical throat and a divergent outlet cone. There are no protrusions into the venturi, sharp corners or sudden changes in the contour of the meter as shown in Fig.3.

Fig.3 Venturi tube (www.omega.com) (www.lmnoeng.com) (www.test-and-measurement-world.com, 2016)

The Venturi effect is the reduction in fluid pressure that results when a fluid flows through the converging inlet section the fluid velocity must increase to satisfy the equation of continuity. Therefore, its pressure must decrease due to conservation of energy. The gain in kinetic energy is balanced by a drop in pressure or a pressure gradient force. The low pressure is measured in the centre of the cylindrical throat as the pressure will be at its lowest value, where neither the pressure nor the velocity will be changing. The equation for the drop in pressure due to the venturi effect can be derived from a combination the continuity equation and Bernoulli’s equation (Fig.3). As a fluid enters the diverging section the pressure is largely recovered lowering the velocity of the fluid (www.testandmeasurementworld.com, 2016).

Assume incompressible flow and no frictional losses, from Bernoulli’s Equation

P_1/?+?V_1?^2/2g+Z_1=P_2/?+?V_2?^2/2g+Z_2…………………………………………. (1)
Use of the continuity equation Q = A1V1 = A2V2, equation (1) applied between inlet; a and throat b; becomes
(p_a-p_b)/?+Z_a-Z_b=?V_b?^2/2g 1-(A_b/A_a )^2 …………………………… (2)

For a flow through where there is no change in height Q can be written as
??Q_theoretical=A_a 1-(A_b/A_a )^2 ?^(-1/2) 2g((p_a-p_b)/?)?^(1/2)………….. (3)
Where

Aa = Inlet area – 5.310 x 10-4 m2
Ab = Throat area – 2.011 x 10-4 m2
g = 9.81 m/s2
? = Density of water = 1000 kg/m3
Pa = Inlet pressure
Pb = Throat pressure

In a real system there will be a correction factor Cd included in the equation. Therefore;

Q_actual=?(Q?_theoretical)(C_d)

So therefore, Cd can be determined mathematically by using the equation below:

C_d=Q_act/Q_theo

Cd can be determined graphically using the volumetric flowrate of the weigh bench on the y-axis and the ?H of the tapping b and c of the venturi meter. Another method for determining this will be a graph of Qact on the y-axis and Qtheotetical on the x-axis as per the equation above. (TecEquipment, 2017)(Mott, 2010)(Street, Watters, Vennard. 2012)(www.lmnoeng.com, 2018)

As a part of this experiment Cd will be determined and comparisons made with the orifice meter.
Orifice Meter

The orifice for use as a metering device in a pipeline consists of a concentric square-edged circular hole in a thin plate, which is clamped between the flanges of the pipe as shown in fig. 4 below

Fig. 4 Orifice meter (www.omega.com) (www.lmnoeng.com)

Pressure tap points are placed either side of the orifice plate. The downstream pressure tap is placed at the minimum pressure position, which is assumed to be at the vena contracta. The centre of the inlet pressure tap is located between one-half and two pipe diameters from the upstream side of the orifice plate; usually a distance of one pipe diameter is employed. Equation (4) for the venturi meter can also be employed to the orifice meter
??Q_theoretical=A_f 1-(A_f/A_e )^2 ?^(-1/2) 2g((p_e-p_f)/?)?^(1/2)………………… (4)

The coefficient of discharge, Cd in the case of the orifice meter will be different from that for the case of the venturi meter. Bit, it still holds that:

C_d=Q_act/Q_theo

??Q=C_d A_f 1-(A_f/A_e )^2 ?^(-1/2) 2g(h_e-h_f )?^(1/2)…………………………. (5)
Where

Ae = Orifice area – 3.142 x 10-4 m2
Af = Orifice Upstream area – 2.116 x 10-3 m2
(he – hf) = Pressure difference across the orifice
g = 9.81 m/s2
? = Density of water = 1000 kg/m3

Between tappings e and f on the orifice on the hydraulic bench the kinetic head should be considered as the velocity change is more pronounced than in the venturi so will not be negligible; flow becomes more turbulent. Therefore, Cd will be ?1.

Bernoulli equation (1) can be re-written with no change in height;

?V_f?^2/2g-?V_e?^2/2g=(P_e/?g-P_f/?g)-?H_Loss …………………… (6)

i.e. the effect of the head loss is to make the difference in manometric height (he- hf.) less than it would otherwise be.
An alternative expression is

?V_f?^2/2g-?V_e?^2/2g=?C_d?^2 (P_e/?g-P_f/?g) …………………… (7)
Where, the coefficient of discharge Cd is given for the geometry of the orifice meter available from the laboratory manual; Cd is given as 0.601.
Reducing the expression in the same way as for venturi meter,

Q=A_f ?V_f?^2

Q = C_d A_f 2g/(1-(A_f/A_e )^2 ) (P_e/?g-P_f/?g)^(1/2) …………………… (8)

Cd has to be determined graphically using the volumetric flowrate of the weigh bench on the y-axis and the ?H of the tapping E and F of the orifice plate meter.

Another method for determining this will be a graph of Qact on the y-axis and Qtheotetical on the x-axis as per the equation above. (Esposito, 2007) (Douglas, Gasiorek, Jack etal, 2011)

As a part of this experiment this will be determined and comparisons made.
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Material and Apparatus

Domestic water is the material that is required as the experimental medium.

Apparatus

Flowmeter Measurement Apparatus (Model H10)

Fig 5 Apparatus set up of H10

Water outlet Rotameter
90o Elbow Wide-Area Diffuser
Orifice Venturi
Water Inlet Manometer/ Piezometer Tubes

Hydraulic Bench – To allow water flow by time volume collection to be measured.

Stop watch – determine the flowrate of the water.

Methodology
Method for determining Q for all equipment tested and for the determination of head loss.

Appendix 1 contains the safe working instructions for the lab and should be adhered to at all times during the experiment.
Once the equipment had been set up as per diagram in Fig. 6 and using the instructions included in Appendix 1the apparatus valve was opened until the rotameter showed a reading of approximately 100mm.
During the period after the flow had settled readings were taken at the meniscus level of the manometers A-I and recorded in results table 1.
Once this had been carried out the plug was fitted to the hydraulic bench and the time taken to re-fill to 10L was recorded using a stop watch in results table 1. This level was determined using the level gauge on the side of the hydraulic weigh bench (Fig. 7)

Fig. 6 Level gauge on the side of the hydraulic tank used to recorded time taken for the tank to re-fill to 10L.

This procedure was carried out again for values of flow rate, Q measured on the rotameter scale down to 10mm reducing in increments of 10mm. This was done by adjusting the bench valve and discharge valve that were located on the side of the tank.
The results were all recorded in results table 1. The time taken to re-fill was also noted on each occasion as described in step 3.
The data obtained from manometer tubes that were used are shown with relevant sizes in Figs 8-10:

Fig. 7 Overall diameters in tabular form.

Fig. 8 Diagram of the dimensions used for the Venturi meter

Fig. 9 Diagram of the dimensions used for the Orifice meter

Where,
Probes A, B and C for the Venturi calculation,
Probes E and F for the Orifice calculation, and
Probes H and I for the rotameter.

With the above as guide the water levels of each probe were recorded in Table 1 at each of the described flow rates.
The height differences between each of the pressure tappings in each meter and the calculations provided in the introductory theory to provide the flow measurement in each element against the weigh tank readings.
The weigh tank reading is also noted against the rotameter which can be read directly from the transparent scale.
Method for determination of the loss coefficient, Cd when fluid flow flows through the venturi, orifice and rotameter.

The values of water level in probes A and B for the venturi and, E and F for the orifice a graph of Head loss in metres against the actual flow rate as per the weigh tank were plotted to determine the discharge co-efficient of both devices.
The rotameter head loss was determined using a transposed calibration graph of the flow rate of the weigh bench against the height in cm of the rotameter.
Head loss calculations were carried out to determine the kinetic head of each device. These results were then used to compare all the flow meters using graphical and calculated means.
Data and Analysis

All data and calculations can be seen in full in Appendix 2

Table 1: Results obtained from experimental analysis of the H10 flow apparatus at 10 different flow rates.

Calculations were carried out to determine the actual flow rate by using the data obtained for time taken for the tank to fill with 10kg of water using the equation below for each experiment:

Q_act=(Mass of water (L))/(Time (mins))

The flow rate Qact was then recorded on Table 2. The value of Q for the rotameter was determined using the calibration graph that was provided in the manual. Unfortunately the copied paperwork was poor so I reproduced this graph using the points were the original crossed at recognizable places (Graph 1)

Graph 1: Calibration graph for the Rotameter.

The flow rates at 100mm down to 10mm in increments of 10mm and recorded in the results table in terms of centimetres. The flowrates were then recorded in table 2 as Qrotator.

The values of Cd were then experimentally determined using the ??h on the x-axis and the volumetric flow rate from the weigh tank; Qact

The value of Cd was also plotted with Qactual v’s Q. This resulted in:

Gradient = Cd
Experiment Qactual w/o Cd
Venturi Orifice Weigh Tank
1 15.28 24.62 15.42
2 13.91 22.97 14.15
3 12.39 20.34 12.47
4 11.26 17.91 11.69
5 10.00 16.02 9.76
6 8.76 13.87 8.28
7 7.53 12.24 7.14
8 6.33 10.34 5.93
9 5.17 8.44 4.73
10 4.08 6.54 3.69
Table 2: Experimental ; calculated data used to allow for the coefficients of discharge to be determined for the venturi and orifice meters.

T

Graph 2: Graph to show the coefficient of discharge where the gradient can be used to determine Cd.

Determining the Flow rates for the Venturi and Orifice meters

To determine the flowrate the cross-sectional areas of the points where the manometers are reading is an essential task. These cross-sectional areas are recorded in table 4.

Table 3: Table showing the calculated cross-sectional areas of the each section where the manometer is reading. This table is used to help determine, volumetric flow, mass flow and subsequently in head loss equations.

Venturi Meter

The flow rates for the venturi were determined using equation 3 from the theory, introducing the coefficient of discharge to account for pressure losses due to friction and the like.

??Q_(act-venturi)=C_d A_c 1-(A_c/A_a )^2 ?^(-1/2) 2g((p_c-p_a)/?)?^(1/2)………….. (3)

The value of 1.07 (graph 2) was used for Cd and this was calculated for all experimental flows from 100mm down to 10mm in increments of 10mm on the rotameter. The cross-sectional areas for the throat and outlet were determined using (?D^2)/4 and this data was used to determine the ratio of the areas squared (Table 3). The readings from manometers a and c were used to determine the pressure differentials. The calculated data for the volumetric flow are recorded in table 4. These figures are in m3/s so were then re-calculated for L/min so that comparisons can be made between actual flow rate and the venturi flow rate Qventuri.
Experiment Volumetric Flowrate Q
(L/min)
Venturi Orifice Rotameter Weigh Tank
1 10.08 26.34 14.19 15.42
2 9.18 24.58 12.77 14.15
3 8.17 21.76 11.35 12.47
4 7.43 19.17 9.93 11.69
5 6.60 17.14 8.51 9.76
6 5.78 14.85 7.10 8.28
7 4.97 13.09 5.68 7.14
8 4.18 11.07 4.26 5.93
9 3.41 9.04 2.84 4.73
10 2.70 7.00 1.42 3.69
Table 4: Table to show the volumetric flowrate for the venturi, orifice, rotameter and the weigh tank.

Orifice Meter
The flow rates for the orifice were determined using the equation 8 below from the theory:

Qact – orifice = C_d A_f 2g/(1-(A_f/A_e )^2 ) (P_e/?g-P_f/?g)^(1/2) ………….. (8)

The value of 0.66 was used for Cd as this was calculated and represented graphically (graph 2) for all experimental flows from 100mm down to 10mm in increments of 10mm on the rotameter. The cross-sectional areas for the throat and inlet were determined using (?D^2)/4 and this data was used to determine the ratio of the areas squared (Table 3). The readings from manometers E and F were used to determine the pressure differentials. The calculated data for the volumetric flow are recorded in table 4. These figures are in m3/s so were then re-calculated for L/min so that comparisons can be made between actual flow rate and the venturi flow rate Qorifice (Appendix 2).
These results were plotted into a graph (Graph 3) with Qact on the x-axis and the value of Q calculated for each meter.

Graph 3: Graph showing the comparison of flow rates between the 3 meters tested with the Weigh bench flow as a datum.

The graph shows the comparison of the flow rates between the meters with the experimentally determined, Cd factor being applied.
The graph shows that as the flow increases in the rotameter so does the flow rate in the venturi and orifice.
It shows that the calculated flowrate of both the venturi and orifice meters is offset from the flow rate recorded for the weigh tank. The venturi measures a lower flow rate and the orifice measures a higher flow rate.
Both the venturi and the orifice meters measures closer to the weigh tank at lower flows than higher flows but the rotameter measures closer as flow rate is increased.

Calculations of Head Loss

Head loss can be calculated by the following equation

H_2-H_1=?H_21

Therefore, the head loss for each meter can be determined as below and inputted into table 6. The data has also been displayed graphically (graph 4).

Venturi Head loss H_c-H_a=?H_ca

Orifice Head Loss H_f-H_e=?H_fe

Rotameter Head Loss H_i-H_h=?H_ih

Experiment Head Loss (m)
Venturi Orifice Rotameter
1 0.018 0.085 0.099
2 0.014 0.074 0.099
3 0.012 0.058 0.098
4 0.008 0.045 0.1
5 0.01 0.036 0.098
6 0.007 0.027 0.1
7 0.005 0.021 0.1
8 0.004 0.015 0.101
9 0.003 0.01 0.103
10 0.002 0.006 0.102
Table 5: Table showing the comparative head loss across the venturi, orifice and rotameters.

Graph 4: A graphical display of the head loss afforded by the venturi, orifice and rotameters over incremental volumetric flowrates from 100L/min down to 10L/min with reductions of 10L/min for each experiment.

Discussion

Discussion of meter characteristics
There is little to choose in the accuracy of discharge between the venturi meter, the orifice meter and the rotameter. All are dependent on same principle. Discharge coefficients and the rotameter calibration are largely dependent on the way the stream forms a ‘vena contracta’ or actual throat of smaller cross-sectional area than that of a constraining tube. This effect is negligibly small where a controlled contraction takes place in a venturi meter but is significant in the orifice meter (Graph 1 for the rotameter and graph 2 for the venturi and orifice meters). The orifice meter Cd is also dependent on the precise location of the pressure tappings (e) and (f). Such data is given in the literature available in BS 1042-1.4:1992 (British standards institution, 2013) which also emphasizes the dependence of the meter’s behaviour on the uniformity of the flow upstream and downstream of the meter.
Graph 1

Graph 2

To keep the apparatus as compact as possible, the dimensions of the equipment in the near the orifice meter have been reduced to their limit. Consequently, some inaccuracy in the assumed value of its Cd may be anticipated. The assumed values from the manual were 0.98 for the venturi and 0.601 for the orifice. The values obtained by experimentation were 1.07 for the venturi and 0.66 for the orifice, both values are higher than the manual by a small margin but, the error is Qactual>Qventuri>Qorifice.

The graph shows that compared to the orifice the venturi is more accurate since the flow rate achieved is closer to Qactual. His is owing to it streamlined design, gradual contraction and expansion that prevent flow separation and swirling, and therefore only suffers frictional losses on the inner wall surface. The streamlined nature of the venturi almost eliminates boundary – layer separation and as a result drag is assumed to be negligible. The diameter of the apparatus changes gradually and as such the flow stays streamlined and does not have to change direction as in the orifice and rotameter. It also has no obstructions to flow as in the rotameter by its float.

The orifice meter has the simplest design and occupies minimal space but the sudden change in the flow area causes considerable swirl and the velocity increase as the vena contracta deceases. It therefore follows that the smaller the vena contracta the greater the pressure difference thus, higher energy resulting in higher head loss. The considerable difference in head loss between the orifice and the venturi should be noted from graph 4.

Graph 4: A graphical display of the head loss afforded by the venturi, orifice and rotameters over incremental volumetric flowrates from 100L/min down to 10L/min with reductions of 10L/min for each experiment.

Rotameters and other flow measuring instruments which depend on the displacement of floats in tapered tubes may be selected from a very wide range of specifications. It is unfair to compare the rotameter with the venturi meter from the standpoint of head loss (Graph 4) due to the orientation change but, provided the discharge range is not extreme, the ease of reading the instrument may well compensate for the somewhat higher head loss associated with it.
Conclusion

In this experiment, flowrate was measured by using venturi meter, orifice meter and rotameters. This measuring technique operation and characteristics are to be determined by comparing pressure drop that will be calculated using the Bernoulli and continuity equations.

The most direct measurement of fluid discharge is by the weigh tank principle. Where this is impossible to achieve often due to the size of the tank and/or gaseous fluid flow one of the three discharge meters described should be used instead.

From the data obtained, the values obtained for the venturi meter were closer to the actual flow rate. This is due to the lower pressure drop resulting from its streamlined shape and almost eliminates boundary-layer separation and thus the drag is assumed to be negligible. It has converging and diverging part. Although there may be pressure loss in the converging part of the venturi but it can often be recovered in the diverging part. This meter is good for high pressure and energy recovery.

The orifice meter has a high pressure drop and this is unrecovered because the flow rate is increases at the opening of the orifice plate and not much energy is lost but as it flows through and starts to slow down, much of the energy is lost.

The rotameter is the easiest to determine the discharge requiring only the sighting of the float and reading of the calibration curve. However, the energy losses were significantly higher than the venturi and orifice meters. This high energy loss is due to the large drop in pressure due to friction. It does need to be chosen carefully to make sure that the associated head loss is not excessive.

In conclusion, the orifice meter as a device is much simpler to make and use, for it is comparatively easy to manufacture a suitable orifice plate and insert between two existing flanges on a pipe. By contrast, the venturi meter is large, comparatively difficult to manufacture and complicated to fit into an existing pipe network. But, the low head low associated with the controlled expansion occurring in the venturi meter gives it an obvious superiority in applications where power to overcome flow losses may be limiting.

Recommendations

Based on this experiment there are many ways this could be made better.

We must take greater care with the experiment and read the experimental manual before use to ensure we are carrying out correctly.
We must check that no air bubbles are present for better accuracy and help avoid reading errors. A pen or other implement could be used to depress the valve on the top of the manometer board to allow fluid and trapped air to escape out.
When we take readings from the manometer board we should make sure that it is at eye-level every time to avoid parallax error. This will allow for the date we gather to be more accurate and consequently the results.
The experiment should be carried repeatedly at least three times to get average readings. This will reduce the deviation with theoretical results.

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