2103393
Lecture Notes
2103393 ME Lab Non ME, Section 4
Second Semester, Academic Year 2554
Department of Mechanical Engineering
Chulalongkorn University
1
Introduction



2103393 ME Lab Non ME Section 4
Dr Kuntinee Maneeratana (KMN) 905/Eng4
Topic
 Evaluation
 Report
 401 Flow through a Venturi
 406 Refrigeration
 405 Air compressor
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2
Overall Objectives


Introduction to ME tests
Experiments
 For discovery
 Development
 Testing
Experiments for Quality Control & Product Testing
3
3
Evaluation



During experiments
Lab Instructor
Graph of result summary
 Submit to KMN by the end of each lab
15%
Full group report (1 week later)
85%
 Equipment testing technical report
 Submit to supervisors (assume to know engineering
fundamentals))
4
4
Evaluation: Report
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Abstract
Introduction
Theory
Equipment & procedures
Results
Discussion
Conclusions
Appendix
 Appendices
 Work declaration by each member
 Check list
10
5
5
15
25
10
5
10
No more than 7 pages, excluding appendices
5
5
Report: Guideline & Check List


MIT Writing Cooperative Technical Report Checklist
MIT Report Writing Guidelines
6
6
Report: Equipment & Instruments


Equipment
 Rough specification
Instruments
 Measured quantity (Temperature T1)
 Range (10 – 50 °C)
 Resolution (1 °C)
C)
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7
401
FLOW THROUGH A VENTURI
2103393 ME Lab Non ME, Section 4 & 7
Second Semester, Academic Year 2553
Department of Mechanical Engineering
Chulalongkorn University
8
Theory: Flow Meters

Coriolis
 Excitation force causes the tube to twist due to
coriolis acceleration
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9
Theory: Flow Meters

Magnetic
 Changes of induced voltage of the conductive fluid
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10
Theory: Flow Meters

Positive displacement
 Rotating impeller






Nutating disc
Rotating valve
Oscillating piston
Oval gear
Rotating lobe
Birotor
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11
Theory: Flow Meters …

Target
 Measuring drag forces on the target
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12
Theory: Flow Meters

Differential pressure

Flow nozzle

Orifice

Venturi
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13
Theory: Pressure Differences
Continuity eqn
Bernoulli eqn
1  2 , z1  z2 ,
  1A1u1  2 A2u2 1
m
2
1
1
P1  1u12  1gz1  P2  2u22  2gz2
2
2
1
1
1
A2 2 
2
2
2
P1  P2  2u2  1u1  2u2  1  ( ) 
2
2
2
A1 

Flow rate

A2 2 
Q  A2u2  A2  1  ( ) 
A1 

Actural flow

A2 2 
Q  Cd  A2  1  ( ) 
A1 

1/ 2
1/ 2
1/ 2
2

  (P1  P2 ) 


1/ 2
2

  (P1  P2 ) 


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14
Theory: Q – P Relationship
P1  P2   g (H1  H2 )
Q  Cd 
A2 2g
1  (D
2
/ D1 )
4

1/ 2
H1  H2
y  mx  c
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15
Test Rig
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Objectives



Official
 To understand a method of flow measurements
 To obtain the value of Cd for a venturi
Technical Report
 Calibrate the meter
What is wanted from the report
 Determine Cd
 Range of flow rate that you can confidently use the
Cd to measure flow rate.
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17
406
REFRIGERATION
2103393 ME Lab Non ME, Section 4 & 7
Second Semester, Academic Year 2553
Department of Mechanical Engineering
Chulalongkorn University
18
Presentation

Trane Powerpoint
 Refrigeration cycle
 Refrigeration components
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19
Theory: Cycle
C
discharge
line
condenser
liquid
line
expansion
device
compresso
r
B
A
suction
line
D
evaporator
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20
Theory: Status
high
hi
h T,
T high
hi h P
Saturated/subcool
liquid
high T, high P
superheat vapour
condenser
d
presssure
G
expansion
p
device
low T,
T low P
liquid+vapour
A
F
D
E
121..5°F
121
[49
49..7°C]
evaporator
41..2°F
41
[5.1°C]
compressor
B
C
low T, low P
p
Saturated/superheat
vapour
enthalpy
21
21
Theory: Formula
Energy eqn
v2
 gz  h  Q  W  const
2
kinetic  potential  enthalpy  heat  work  const
v  fluid
fl id velocity
elocit
z  altitude
h  enthalpy  U  PV
Q  heat entering the system
W  work leaving the system
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22
Theory: Formula
Compression process 1  2
Heat
Q0
((Isotropic)
p )
Work
W  h1  h2
(  ve work entering)
Condensation process 2  3
Heat
Q  h3  h2
Work
W 0
(  ve heat out)
Expansion process 3  4, h3  h4
Heat
Q0
Work
W 0
Evaporation process 4  1
H t
Heat
Q  h1  h4
Work
W 0
( fi
(refrigerating
ti effect)
ff t)
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23
Theory: Formula
COP 
refrigerating effect what you get

work done
what you loss
h1  h4
COP 
h2  h1
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24
Test Rig
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25
Objectives



Official
 Determine by quantitative measurement how well
the mathematical models (theoretical equations) of
the compressor, condenser, evaporator represent
what actually happens. Draw the actual cycle on the
P – h diagram.
diagram Compute the coefficient of
performance COP.
Technical Report
 Evaluate the performances of the refrigeration cycle
and components
What is wanted from the report
 P – h diagram
 COP
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26
405
AIR COMPRESSOR
2103393 ME Lab Non ME, Section 4 & 7
Second Semester, Academic Year 2553
Department of Mechanical Engineering
Chulalongkorn University
27
Theory: Single Stroke Compressor

http://www.tpub.com/content/doe/h1018v2/css/h1018
v2_85.htm
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28
Theory: Indicator

http://www.oldengine.org/members/diesel/Indicator1.
htm
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29
Theory: Indicator

http://www.oldengine.org/members/diesel/Indicator1.
htm
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30
Theory: Polar Planimeter

http://reckonsurveying.com/page8-10.html
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31
Test Rig
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Objectives



Official
 To learn how to make measurements of indicated
horsepower (Ihp) and brake horsepower (Bhp)
 To investigate the performance of a single stage,
reciprocating air compressor under conditions of
constant speed
Technical Report
 Evaluate the performances of the air compressor
What is wanted from the report
 Bhp & Ihp – pressure ratio at a constant speed
 Mechanical efficiency – pressure ratio at constant
speed
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