Lab Manual - B48BB Process Engineering A_september 2015

B48BB Process Engineering A

Semester 1

Year 1 Laboratory Handbook

Heriot-Watt University Malaysia

This material is prepared to support the degree programs in Chemical and Petroleum Engineering.

Overview

Laboratory exercises serve two purposes: • To re-enforce material covered in lectures by focusing on specific objectives

concerning the fundamental topics of fluid mechanics and physical properties. • To experience taking, analyzing and reporting physical measurements where

there are clear connections between each variable. One of the key drivers behind Heriot-Watt engineering programs are the inclusion

of practical elements that expose students to dealing with physical phenomena in a

way no text book or video or on-line system can. What better way to learn that air

contains condensable and non-condensable gases, what better way to learn that

heat flows from hot to cold that pressure increases when flowrate will increases.

2.0 Safety Safety should be a major part of the laboratory – students should be required to

conduct themselves in a safe manner and all staff need to demonstrate good

practice. Risk Assessment – Supervisors and demonstrators need to complete and maintain

risk assessments for each experimental activity. The laboratory supervisor should

manage this and advise staff accordingly. A signature sheet should be provided for

each laboratory experiment for students to sign to say they have read and

understood the risks of the activity. PPE – students will be told to bring their own PPE (lab coat, glasses, gloves) For reasons of safety, laboratory work may only be carried out during the specified

periods. No experiment should be carried out without the laboratory supervisor

present. Majority of experiments use water, air and have electrical power connection.

Occasionally some will use substances that are flammable, irritant and come under

the Control of Substances Hazardous to Health (COSHH). When completing their

risk assessment, supervisors should carry out a separate COSHH assessment

where it is needed. The roles of demonstrators are defined elsewhere but in summary, your role is to

first demonstrate the experiment (turn on, operate, switch off), and to watch the

students when they operate the experiment. Both students and demonstrators need

to understand the equipment, what it does before switching the unit on.

3.0 Report Format There are formal guidelines on how the report should be set out but essentially

this will follow from the reports in 1st year: • Introduction • Theory • Results • Discussion • Conclusion

Marks can be awarded to each section but greater emphasis should be placed on

the treatment of the experimental results and quality of the discussion section. Other points to watch for are: • Copying sections of text from standard reference books – students should

interpret the text and form their own version, bringing in other aspects of theory

if necessary. You may want to ask the student which textbook they are going

to use to satisfy yourself that they will be using text book references. • Copying text from the laboratory sheets should not be tolerated. Students have

a tendency to use screen capture, to write experimental procedures in exactly

the same way as the laboratory sheet. From 2014, we have asked that

experimental procedures should document any changes that were done, rather

than the exact experimental procedure. • Clear presentation of results - both raw collected data, and processed data

presented in graphical and tabular format. Graphs should be clearly marked

(title, labels) and tables should have meaningful headings with the appropriate units. Unexplained spreadsheet printouts should be discouraged. Large

spreadsheet printouts without adequate documentation either in the text or on

the actual sheet can make the whole sheet very difficult to understand. A

sample calculation should be shown so that correct application of theory is

tested. • Use of appendices - students often place all their data and results in

appendices. While this may be convenient for organizing the report, it might be

better to put graphs which show key findings and which are used in the

discussion, close to the discussion. There should always be some sort of

summary of the results in the text of the report before any discussion. The students have a format to follow for written reports (you should also have a

copy of this) and they should be encouraged to follow it.

Consistency between different assessors causes students concern and may

actually be detrimental to the student’s self-confidence. Some students claim to

have spent considerable time over reports and receive little reward with

improvements in grade. Although this may be a fault of inappropriate feedback,

there could be some degree of inconsistency between assessors.

3.1 Returning Reports Please try to be prompt handing back work. Ideally this should be done at some

point in the next lab session personally or into the tray/box for marked reports,

rather than having the students trying to look for you. If you are unable to see the student during the next lab, then make an appointment (e- mail might be a better

way to organize a meeting, copy the e-mail to the appropriate director of study). In case there’s a dispute you can always produce the e-mail messages. If you think

the student is asking too much, then contact the academic supervisor and the year

director of studies. Feedback to the academic teaching the material helps the academic – so please do this if you can. Reports should in any case be returned within 14 days of the submission date,

whatever the lab. Equally important is to record marks given and any comments you feel you should

make and pass this on to the appropriate member of staff or laboratory supervisor.

Students should keep their reports in case staff ask for these in some way. 3.2 Plagiarism Plagiarism in laboratory work takes two forms 3.2.1 Inappropriate use of reference material Where students cut and paste what they think are sections from web sites and text books. Markers need to be aware of this a challenge the tell-tale signs that students

have done this without really referencing the original source. In some cases,

students will attempt to duplicate large sections of text (5-10 lines) but include the

reference. In this case they are satisfying the letter of the law, but not the intent –

copying 10 lines of text means they have not really understood what is being said. For all stage 2 experiments, there should be no reason for students to go to these

lengths – the focus is on results, the data processing and explaining the results. 3.2.1 From Other Students This can be the more significant challenge to detect especially if reports are

handed back to some students. If demonstrators believe there is copying between

students, then they should look through the electronic submissions on Vision. If

they think something is wrong then report this to the academic supervisor, the

laboratory supervisor for further advice.

Penalties for plagiarism are clearly documented in the programed handbook.

4.0 Laboratory Details This section contains a summary of each experiment, together with learning

objectives. Since BHOS and Malaysia will be the first to use GUNT laboratory kit,

there are no examples of data that can be collected. Demonstrators are therefore

asked to keep records of how well individual kit items perform. GUNT manuals contain examples of theory, data plots and physical property data.

Our preferred way of working is not to use manufacturer’s manuals, but give

alternative documentation that focuses on specific tasks. The fluid mechanics and heat transfer experiments by GUNT need a BASE UNIT

to provide the water flowrate, and source of heating & cooling. Laboratory

Supervisor and demonstrators should be trained up using the base units. Fluid Mechanics Base Unit: HM150 This has a pump, main flow control valve, water holding tank and volume

measuring tank. Normally, the volumetric flowrate from the pump will be affected

by the downstream pressure drop of the experiment under test. GUNT have

provided a classical “bucket and stopwatch” approach to calibrating the flowrate

for a particular valve setting. Demonstrators – We suggest that when varying the flowrate on HM150 main

control valve, that you measure the volumetric flowrate using the standard

procedure. You should get the students to do this as a matter of course so that

they become used to calibrating systems. At some stage, you may like to look at

installing a flow measuring device onto this unit.

4.1 Experiment 1: Friction Losses in Bends

Objective: To find out relationship in pressure losses across elbows and fittings Notes 1. This experiment is similar to experiment 3 and should only

be done by the same group in special circumstances.

2. Students should measure the pressure loss across all or a number of fittings, for a range of volumetric flowrates. They need to set the flowrate using valve 10, measure the pressure

drop

3. The GUNT manual lists several experiments that can be done and you may wish to start with the simple pressure drop

vs

3. Calculate what the pressure loss across each fitting would be using theory and compare with the measured values from the experiment.

4.2 Experiment 2: Bernoulli’s Principle Objective: To show that as the cross sectional area reduces, the pressure

measured through the reduction decreases as the velocity increases. Notes 1. This is a rather simpler experiment to do than others but the

level of post experiment analysis is greater.

2. Students should measure the pressure profile for up to 2

different flowrates. They should repeat the measurements in

order to test the accuracy and repeatability.

3. The GUNT manual covers the theory very well and gives

examples of data

4.3 Experiment 4: Flowmetering Devices Objective: To show how differential pressure can be used as a measure

of average velocity and hence volumetric flowrate for a number of meter types. Notes 1. Key finding will be the discharge coefficient as a function of

Reynolds number.

2. Students can derive expression for flowrate from first

principles – starting from Bernoulli’s equation.

3. The rig used is one of the more complex rigs that has flexibility in the type of experiments to perform.

4.6 Experiment 5: Centrifugal Pump

Objective: To familiarization with operating behavior and characteristics of a centrifugal pump through experiment

Notes 1. Pump characteristics of a centrifugal pump are important as they are used to select the pump for the appropriate job. 2. Plot head curves vs flow rate for the pump that’s installed.

1


School of Engineering and Physical Science

Chemical & Petroleum Engineering

Laboratory Experiment Experiment 1: Friction Losses in Bends and Fittings

Contents 1 Introduction ........................................................................................................... 1 2 Basic Theory ......................................................................................................... 1 3 Flow Diagram ........................................................................................................ 2 4 Operational Notes ................................................................................................. 3 5 Safety Note ........................................................................................................... 3 6 References ............................................................................................................ 3

1 Introduction In fluid mechanics, you will learn about how liquids and gases flow from one part of a

process until into another. To move fluid, you need energy to overcome pressure

differences between the inlet side of the pipe and the outlet side. Energy is also needed

to overcome friction caused by the fluid

2 Basic Theory When liquids or gases flow along pipelines and through fittings such as elbows, Tee

junctions, there is a loss of energy due to friction along the pipe wall. We therefore need

to understand the relationship between this pressure loss and the velocity of the fluid.

Another phenomena in fluid flow is the difference between turbulent flow and laminar

flow. Under fully turbulent flow, the relationship between pressure loss and velocity is of

the form: 3 Flow Diagram

2

1 Elbow and Fittings Base frame 4. Pipe Elbow (Test Section 1) 2 Hose connection to water inlet (use the 5. Rounded Pipe Elbow (Test Section 2) Fluids Base Unit or standard water

supply) 3. Hose connection to drain 6. Tight radius pipe bend (Test Section

3) 10 Main flow control valve 7. Large radius pipe bend (Test section VALVE C 4)

11 6 Channel manometer 8. Pipe reducer (Test Section 5)

12 Spring tube manometer 9. Pipe enlarger (Test Section 6)

14 Pressure measurement hose 13 Circular Chamber text section

This unit will normally sit on top of the following Base Unit

Pos. Item Pos. Item

1 Main water storage tank

7 Switch box

TANK A

2 Sliding Valve – VALVE B 8 Overflow pipe

3 Liquid Level Gauge 9 Main Flow control valve

VALVE A

Volumetric measuring tank - for Water supply connection for

4 measuring volumetric flowrate 10

accessories with pump

TANK B

5 Water Connection to Experiment 11 Submersible motor driven pump

6 Water Connection from

12 Drain valve

experiment

3 4 Operational Notes This experiment should be set up for you. Do not attempt to change the connections from

the base unit to the experiment unit unless instructed otherwise.

1. Ensure that the Elbow and Fitting rig is attached to the base unit. 2. Ensure that tank A is filled with water 3. Ensure that the water feed line (line 5) and the water return line (line 6) are

connected to the Elbow and Fitting Rig (line 6) 4. Close VALVE C. 5. Set VALVE A to 50% open, Open VALVE B 6. Connect the pressure measuring hose to across the first elbow. 7. Switch on the pump 8. Bleed the manometer to make sure you are measuring the pressure drop – make

sure there are no air bubbles in the manometer tube. 9. Measure the flowrate from the pump – using the procedure below

a. Make sure the TANK B is empty - open slider VALVE B b. Close VALVE B and record the time taken for the volume to go

BETWEEN 20 to 30 litres. As soon as you are finished, open VALVE B. 10. Record the pressure drop across the fitting. 11. If it is safe to do so, switch the quick release hose lines to another fitting and repeat

steps 10-11.

12. If it is safe to do so, you may increase the flow from feed pump by opening VALVE

A. For your results, you are looking to plot pressure loss vs velocity^2, pressure loss vs

Reynolds number for each fitting. You should also calculate out what the pressure drop

could be from theory – using the head loss or equivalent length values from tables. You

need to repeat some of the measurements to gauge the inherent accuracy and repeatability

of the system.

5 Safety Note This experiment uses water and required electrical power. You should avoid spillages of

water; water spillages should be contained and removed as soon as possible. Activating

electrical switches should only be operated when safe to do so. 6 References Coulson and Richardson Chemical Engineering Volume 1, Elsevier, 1999 JF

Douglas, J Gasiorek Fluid Mechanics, Prentice Hall, 2000

1




Laboratory Experiment Experiment 2: Bernoulli’s Principle

Contents 1 Introduction ....................................................................................................................... 1 2 Basic Theory ..................................................................................................................... 1 3 Key Data ........................................................................................................................... 1 4 Rig Details ........................................................................................................................ 2 5 Operational Notes ............................................................................................................. 3 6 Safety Note ....................................................................................................................... 4 7 References ....................................................................................................................... 4

1 Introduction In fluid mechanics, you will learn about the “Bernoulli” equation, a fundamental relationship

between velocity and pressure for flowing fluids. You will be shown how this equation is derived

and how it can be applied.

2 Basic Theory When fluids flow through a duct or pipeline, a key property is that the mass flowrate remains

constant. For liquids, or other incompressible fluids (where density is constant), where there is

a change in diameter of pipeline, the velocity must increase. Bernoulli’s equations then tells us

that the pressure at that point must change. This experiment allows you to explore the

relationship between velocity an pressure along a converging/diverging section. Imagine a liquid flowing from point 1 to point 2 which can be at a different elevation than point

1. If the liquid flow is frictionless, and there is no other energy exchange, Bernoulli derived an

expression between the pressure and velocity at point 1 to point 2 as:

The other key equation is the continuity equation which says the mass flow along the pipe

must be constant. Since mass flow is given by , then

In this experiment, you will measure the pressure within water flowing through a section which

reduces in diameter, then increases.

3 Key Data Cross sectional area at the pressure tapping measurement points:

2

4 Rig Details

1. Back panel 6. Compression gland 2. Water pressure measurement point 7. Pressure measuring probe –

measures the TOTAL pressure at each measuring point along the venturi 3. Discharge pipeline 8. Water feed connection 4. Outlet flow control valve – VALVE C 9. Inlet control valve – VALVE D 5. Venturi nozzle 10. Manometer rack – measuring the

STATIC pressure at each measuring point along the venturi This unit will normally sit on top of the following Base Unit

3

Pos. Item Pos. Item


7 Switch box

TANK A



VALVE A


4 measuring volumetric flowrate TANK 10


B


6 Water Connection from experiment 12 Drain valve

5 Operational Notes This experiment should be set up for you. Do not attempt to change the connections from the

base unit to the experiment unit unless instructed otherwise.

1. Ensure that the Bernoulli rig is attached to the fluids base unit (or connected to a water supply),

2. Ensure that tank A is filled with water 3. Ensure that the water feed line (line 5) and the water return line (line 6) are connected

to the Bernoulli rig (line 8) 4. Open VALVE C. Set VALVE D to 50% 5. Set VALVE A to 25% open – this may change to increase the flow through venturi 6. Reset the position of the overall pressure probe 7. Switch on the pump 8. Make sure the manometer tubes have water mid-way between the LL and UL

positions. You may need to balance VALVE C and VALVE D. a. Open the vent valves on both manometers b. Slowly close the exit valve, VALVE C until there is water in each manometers

9. Measure the flowrate from the pump – using the procedure below a. Make sure the TANK B is empty - open slider VALVE B b. Close VALVE B and record the time taken for the volume to go BETWEEN 20

to 30 liters. As soon as you are finished, open VALVE B. 10. Record the manometer pressures along the venturi 11. Use the overall pressure probe to record the total pressure at each measuring

position. 12. Try to change the main feed flowrate to at least 3 values. 13. Make sure you repeat at least one of the flowrates to measure the repeatability and

accuracy of the instruments. 14. Once all elements have been measured, switch off the pump, close valve A, open

valve A. Open valves C and D. For your results, you should calculate the DYNAMIC PRESSURE by:

You need to calculate the actual velocity of liquid at each of the measuring points by:

You need to calculate the theoretical velocity, using Bernoulli’s equation for each of the

measuring positions.

You should also calculate the Reynolds number for each measured point.

Plot the appropriate data together to compare theory with measurements

4

6 Safety Note This experiment uses water and required electrical power. You should avoid spillages of water;

water spillages should be contained and removed as soon as possible. Activating electrical

switches should only be operated when safe to do so. 7 References Coulson and Richardson Chemical Engineering Volume 1, Elsevier, 1999

JF Douglas, J Gasiorek Fluid Mechanics, Prentice Hall, 2000

1 Heriot-Watt University Malaysia



Laboratory Experiment Experiment 3: Flow Measurement

Contents 1 Introduction ........................................................................................................................ 1 2 Basic Theory ...................................................................................................................... 1 3 Key Data ............................................................................................................................ 2 4 Rig Details ......................................................................................................................... 2 5 Operational Notes .............................................................................................................. 3 6 Safety Note ........................................................................................................................ 4 7 References ........................................................................................................................ 4

1 Introduction Measuring the mass flowrate is critically important no matter what industrial sector you are in,

but to measure this directly is not easy. Easier to do is the volumetric flowrate and this

experiment is designed to show you some basic methods that are used. The experiment will

also demonstrate several key features in fluid mechanics. Note that in industry, measuring

flowrate is also done using a variety of electronic devices, which you will see in later stages of

the programme.

2 Basic Theory When fluids flow through a duct or pipeline, a key property is that the mass flowrate remains

constant. For liquids, or other incompressible fluids (where density is constant), where there is

a change in diameter of pipeline, the velocity must increase. Bernoulli’s equation then tells us

that the pressure at that point must change. Imagine a liquid flowing from point 1 to point 2 which can be at a different elevation than point

1. If the liquid flow is frictionless, and there is no other energy exchange, Bernoulli derived an

expression between the pressure and velocity at point 1 to point 2 as:

The other key equation is the continuity equation which says the mass flow along the pipe

must be constant. Since mass flow is given by, then

These three equations are applied to each of the measuring systems available in this

experiment. For frictionless, inviscid flow, the relationship between the volumetric flowrate,

velocity and the pressure difference between the pipeline and the minimum cross sectional

area is given by: Where A is the cross sectional area of the upstream pipe, a is the cross sectional area of the

minimum point. For real cases where there is friction involved, the volumetric flowrate is given

by:

2

Refer to C&R Volume 1, or any standard fluid mechanics details for exact details on the

theory. A rotameter is a constant pressure type of device, where the position of the float gives a

direct indication of the volumetric flowrate.

3 Key Data Approximate sizes of key sections. You are advised to measure these yourselves. Orifice Plate: Hole diameter 18.5mm Nozzle Meter: Hole diameter 14mm Pitot Tube: Inner diameter 2.1mm, outer diameter 3mm

4 Rig Details

1. Water Outlet pipe 6. Manometer bank 2. Water outlet valve – VALVE C 7. Water Inlet Connection 3. Rotameter section 8. Removable flowmeter section –

variations include orifice, nozzle and pitot tube.

4. Pressure tapping – top of rotameter 9. Venturi flowmeter 5. Support frame


3

Pos. Item Pos. Item


7 Switch box

TANK A



VALVE A




B



5 Operational Notes This experiment should be set up for you. Do not attempt to change the connections from the base unit to the experiment unit unless instructed otherwise. The flowmeter rig should have

been attached to the pump base unit, and primed with water already in the manometer bank. Pressure tappings to the following instruments should have been ready:

• Differential pressure across the orifice or nozzle meter • Differential pressure across the rotameter • Two pressure tappings on the venturi meter – an upstream value and one at the

throat position. To start a flowrate measurement:

1. Open VALVE C 100% 2. Open VALVE B 3. Set VALVE B to 50% open – this will change depending on the manometer readings. 4. Switch on the pump 5. If the rotameter reads low (with the float below the 50% marker) increase the flow

from the pump by opening VALVE A until the float is at the top of the tube. 6. Record the differential pressures from the manometer. 7. Measure the flowrate from the pump – using the procedure below

a. Make sure the TANK B is empty - open slider VALVE B

4

b. Close VALVE B and record the time taken for the volume to go BETWEEN 20 to 30 litres. As soon as you are finished, open VALVE B.

8. Close outlet VALVE C to reduce the flowrate 9. Repeat steps 6 to 8 until the flowrate is small, or the pressures in the manometer are

high. 10. Work backwards and open VALVE C in successive stages, taking all measurements

for a second time. This will give you an idea on the repeatability and accuracy of the system.

11. Once all elements have been measured, switch off the pump, close valve A, open

VALVE B. Open Valve C You should process your results to

a) Calculate the discharge coefficient for the orifice/nozzle meter and the venturi meter for each flowrate tested. Comment on how the discharge coefficient changes or does not change

b) Compare the pressure drop across the orifice meter, the venturi meter and the

rotameter for each flowrate tested. Comment on why the orifice/nozzle meter gives the

highest pressure drop You should also remember to calculate out Reynolds numbers to support arguments you make

in your discussion.



switches should only be operated when safe to do so. 7 References Coulson and Richardson Chemical Engineering Volume 1, Elsevier, 1999

JF Douglas, J Gasiorek Fluid Mechanics, Prentice Hall, 2000

1 Heriot-Watt University Malaysia



Laboratory Experiment Experiment 4: Centrifugal Pump

Contents 1 Introduction ....................................................................................................................... 1 2 Basic Theory ..................................................................................................................... 1 3 Key Data ........................................................................................................................... 2 4 Rig Details ........................................................................................................................ 2 5 Operational Notes ............................................................................................................. 3 6 Safety Note ....................................................................................................................... 4 7 References ....................................................................................................................... 4

1 Introduction Centrifugal pumps are one type of general purpose pump that’s found in the industrial and

domestic sectors. These pumps have well defined characteristics and one of the jobs of the

process engineer is to select the appropriate pump for the anticipated duty. The objective of

this experiment is to measure the typical characteristics of centrifugal pumps (the relation

between developed head and flowrate, efficiency and flowrate) and to investigate the effect of

running pumps at different speeds.

2 Basic Theory Pump characteristics are usually quoted in the form of graphs of head vs. flowrate and

efficiency vs. flowrate. Using these, the correct pump can be selected for the desired flowrate

wanted against the pressure that’s needed. Once the pump’s required head and flowrate has

been determined, the overall efficiency is calculated from:

The percentage efficiency =

where power input

power output

Power Output x100

Power Input

= electrical power input to pump = Volts x Amps (watts) = work done by pump on fluid = volumetric flowrate x differential pressure across the

pump (watts)

Therefore the % efficiency = Q.∆P x100

V.I

Now ∆P = g.ρ.h

Therefore head = ∆P

g.ρ

Where ∆P = differential pressure N/m2

g = acc. due to gravity m/s2

ρ = fluid density kg/m3

h = head m

2

In this experiment, you will measure the pump’s delivery pressure for a range of flowrates. You

will then change the speed of the pump motor and repeat these to see what affect this has on

the pump’s characteristics. You will also investigate the condition known as cavitation.

3 Key Data Cross sectional area at the pressure tapping measurement points: Maximum pump head 36.9m Maximum flowrate: 3000 l/hr

4 Rig Details

1. Electric motor drive 8. Switch to change displayed variable 2. Back panel support 9. On/Off switch 3. Discharge Valve – VALVE C 10. Motor Speed indicator 4. Discharge pressure gauge 11. Master on/off switch 5. Suction pressure gauge 12. Emergency shut off 6. LED indicators 12. Centrifugal pump 7. Power display 12. Base frame


3

Pos. Item Pos. Item


7 Switch box

TANK A



VALVE A




B



5 Operational Notes This experiment should be set up for you. Do not attempt to change the connections from

the base unit to the experiment unit unless instructed otherwise.

1. Ensure that the pump rig is primed and ready for use. Do not attempt to adjust the connections to the base unit yourselves.

2. Open Valve C to 50% - the pump discharge valve 3. Set VALVE A to 100% open 4. Set the pump speed to 100% full and switch on the motor. 5. Measure the flowrate through the pump using the procedure

a. Make sure the TANK B is empty - open slider VALVE B b. Close VALVE B and record the time taken for the volume to go BETWEEN

20 to 30 liters. As soon as you are finished, open VALVE B. 6. Repeat 4 to 5 for different positions of the discharge valve – try at least 10

different flowrates. 7. Change the pump speed and repeat 2 to 6 – try for at least 2 different pump speeds. 8. Open Valve C to 50%, switch the pump to 50% speed 9. Partially close the main flow control valve – valve A to 50%. 10. Repeat a flowrate/pump head data set for Valve A set to 50%. 11. Switch off and reset the controls to where you found them.

4

For your results, you should calculate pump efficiency, the pump head in m of water. You

should plot the pump characteristic curves for the three speed settings. You should also plot

the efficiency curves. You also need to plot the pump curve when the main water feed valve

was partially closed.



switches should only be operated when safe to do so.

7 References Coulson and Richardson Chemical Engineering Volume 1, Elsevier,

1999 JF Douglas, J Gasiorek Fluid Mechanics, Prentice Hall, 2000

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Lab Manual - B48BB Process Engineering A_september 2015

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