SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
1.0
INTRODUCTION
The SOLTEQ® Marcet Boiler (Model: HE169) is a bench top unit designed for the
demonstration of the basic principal in Thermodynamics studies which is the boiling
phenomenon. Students will be able to study the relationship between the pressure and
temperature of saturated steam in equilibrium with water. The saturation pressure curve
can be determined at the pressure within 10 bar (150 lb/in2).
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
2.0
GENERAL DESCRIPTION
The unit consists of a stainless steel pressure vessel fitted with high pressure immersion
electrical heater. The unit also comes together with a safety relief valve, temperature and
pressure measuring devices. Water feed port is installed to allow water charging.
The unit comes with comes with temperature and pressure transducers so that students
will be able to read the respective values on the digital indicators easily. The water heater
is protected from burnout by setting the maximum operating temperature with a
temperature controller.
2.1
Unit Construction
6
1
2
7
8
3
4
9
10
5
Figure 1: Unit Construction for Marcet Boiler (Model: HE169)
1.
2.
3.
4.
5.
Pressure Transducer
Pressure Indicator
Temperature Controller/Indicator
Control Panel
Bench
2
6.
7.
8.
9.
10.
Bourdon Tube Pressure Gauge
Temperature Sensor
Pressure Relief Valve
Heater
Water Inlet Port & Valve
SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
2.2
Description and Assembly
The SOLTEQ® Marcet Boiler (Model: HE169) consists of mainly the following
items:
a) Pressure Vessel
Capacity
Material
Design Pressure
Operating Pressure
Certification
: 3 Liters
: Stainless Steel 304
: 30 bar
: 10 bar
: DOSH certified
b) Pressure Gauge
Type : Bourdon Tube
Range : 0 – 20 bar (g)
c) Pressure Transducer
Wetted Material : Stainless Steel
Case Material : Stainless Steel
Range
: 0 – 16 bar (abs)
d) Electrical Heater
Power: 2000W
Type: Immersion Type
Safety: High temp cut-off by means of a temperature controller
e) Temperature Sensor
Type: RTD (Class A)
Range: 0 – 200°C
f) Safety Features
Pressure Relief Valve (Set at 15 bar), Temperature Controller (Set at 185.0°C)
2.3
Experimental Capabilities
a) Demonstration of relationship between the pressure and temperature of
saturated steam in equilibrium with water
b) Demonstration of the vapour pressure curve
2.4
Overall Dimensions
Height :
Width :
Depth :
2.5
1.15 m
1.00 m
0.60 m
General Requirements
Electrical
Water Supply
:
:
240VAC/1-phs/50Hz
Distilled water
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
3.0
INSTALLATION AND COMMISSIONING
3.1
Installation Requirements
The equipment should be installed on a firm, level work surface. A single phase
electrical supply will be required.
No other services are necessary.
3.2
Commissioning
1. Connect the mains input power supply plug to a nearest single-phase electrical
supply of 230VAC/50Hz.
2. Push the reset button of the Earth Leakage Circuit Breaker (ELCB) inside the
control panel after the main power supply is switched on. The ELCB should be
kicked off, indicating that the ELCB is functioning properly. If not, have a
trained wireman to inspect the equipment for any electrical leakage. The ELCB
should be tested in a regular basis.
3. Open the valves at the feed port, V1, V2, & V3 and level sight tube.
4. Fill the boiler with distilled water through the feed port and make sure that the
water level is at about the half of the boiler’s height. Then, close the valves, V1
& V2 at the level sight tube.
5. Leave the vent valve, V3 at open position.
6. Turn on the power switch. All indicators on the front panel should lit-up.
7. Check the temperature and the pressure readings. The temperature reading
should be close to the surrounding temperature and the pressure reading
should be 1 absolute bar.
8. Switch on the heater and observe the temperature in the boiler. The steam
temperature rise as the water boils.
9. Allow steam to come out from the vent valve, V3 for about 30 seconds, and
then close the valve. This step is important to remove air from the boiler as the
accuracy of the experimental results will be significantly affected when air is
present.
10. Then observe the pressure reading in the vessel. The pressure should rise
when the temperature further increases.
11. Wait for sufficient time to heat up the water up to 10 bar and make sure that
there is no leakage as the pressure increases. If any leakage is observed, fix it
and repeat the above procedure.
12. Switch off the heater after the commissioning and allow the temperature to
cool down.
13. Commissioning of the equipment is now complete.
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
4.0
SUMMARY OF THEORY
Marcet Boiler (Model: HE169) has been developed for investigating the relationship
between the pressure and temperature of saturated steam, in equilibrium with water, at all
pressures between atmospheric and 10 bar (abs) (150 lb/in²).
Thermodynamics is a branch of physics, which deals with the energy, and work of a
system. Thermodynamics deals only with the large-scale response of a system that we can
observe and measure in experiments. Small-scale gas interactions are described by the
kinetic theory of gasses, which is a compliment to thermodynamics.
An ideal gas can be characterized by three state variables: absolute pressure (P), volume
(V), and absolute temperature (T). The relationship between them may be deduced from
kinetic theory and is called the Ideal Gas law. The ideal gas law was originally determined
empirically and is simply.
PV=nRT
Where,
P = Absolute pressure
V = Volume
n = Amount of substance (moles)
R = Ideal gas constant
T = Absolute temperature (K)
If a gas behaves exactly as the ideal gas laws would predict it to behave in terms of
volume, pressure, moles, and temperature, then the gas is said to be an ideal gas. On the
other hand, the gas deviates from Ideal Gas behavior, then the gas is said to be acting like
a "real gas".
When energy increases within water, the increasing of activities among the molecules
enables the increase in the number of molecule escape from the surface until an
equilibrium state is reached. The state of equilibrium depends on the pressure between the
water surface and steam. At lower pressure, the molecules become easier leaving the
water surface while less energy required in achieving the state of equilibrium (boiling point).
The temperature where equilibrium occurs at a given pressure level is called saturated
temperature.
The measured value of the slope of the graph (dT/dP) SAT obtained from the practical
results can be compared with corresponding values calculated from the data in steam
tables. Clausius-Clapeyron states:
Tv fg
 dT 
  
 dP  SAT hfg
T (v f  v g )
 dT 
  
hf  h g
 dP  SAT
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
And hf + hfg = hg
Hence, hfg = hg - hf
T (v f  v g ) Tv g
 dT 

  
hfg
hfg
 dP SAT
As vg >> vf
in which,
vf = specific volume of saturated liquid
vg = specific volume of saturated vapor
hf = enthalpy of saturated liquid
hg = enthalpy of saturated vapor
hfg = latent heat of vaporization
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
5.0
GENERAL OPERATING PROCEDURES
5.1
General Start-up Procedures
1. Perform a quick inspection to ensure that the unit is in proper operating
condition.
2. Connect the unit to the nearest power supply.
3. Check whether water is already filled in boiler. If already filled skip step 4 and
5 below.
4. Open the valves at the feed port and the level sight tube (V1, V2, & V3).
5. Fill the boiler with distilled water through the feed port and make sure that the
water level is at about the half of the boiler’s height. Then, close the valves, V1
& V2 at the level sight tube.
6. Turn on the power supply switch.
7. Now you are ready to carry on with the experiment.
5.2
General Shut-down Procedures
1. Switch off the heater and allow the boiler temperature to drop until room
temperature.
Note:
Do not open the valve at the water inlet port as it is highly pressurized at high
temperature.
2. When it has dropped to room temperature, switch off the main switch and the
main power supply.
3. Retain the water next use.
4. To drain the water open the upper part of the level sight tube, V3 and then
open V1 and V2 to drain off the water.
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
6.0
EXPERIMENTAL PROCEDURE
6.1
Experiment: The Fundamental Pressure-Temperature Relationship of
Saturated Steam in Equilibrium
Objectives:
1. To demonstrate the relationship between the pressure and temperature of
saturated steam in equilibrium
2. To demonstrate of the vapour pressure curve
Procedures:
1. Perform the general start-up procedures as described in Section 5.1.
2. If the boiler is initially filled with water, open the valves at the level side tube
(V2 & V3) to check the water level. Pour in additional distilled water if
necessary. Then, close the valves.
3. Set the temperature controller to 185.0 °C which is slightly above the expected
boiling point of the water at 10.0 bar (abs).
4. Open the vent valve, V3 and turn on the heater.
Important:
Always make sure that the valves at the level sight tube are closed
before turning on the heater as the sight tube is not designed to
withstand high pressure and temperature.
5. Observe the steam temperature rise as the water boils.
6. Allow steam to come out from the valve, V3 for about 30 seconds, and then
close the valve. This step is important to remove air from the boiler as the
accuracy of the experimental results will be significantly affected when air is
present.
7. Record the steam temperature and pressure when the boiler is heated until the
steam pressure reaches 10.0 bar (abs). (Make the intervals of pressure data
for 0.1 initially, followed by 0.2 and 0.5 for the following data)
Warning!
Never open the valve when the boiler is heated as pressurized steam can
cause severe injury.
8. Then, turn off the heater and the steam temperature and pressure will begin to
drop. Start to record steam temperature when the boiler is cooled until the
steam pressure reaches atmospheric pressure.
9. Allow the boiler cool down to room temperature.
10. Record the steam temperatures at different pressure readings when the boiler
is heated and cooled.
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
RESULTS:
1. Complete experimental data sheet.
2. Plot the graph of average temperature, T, against absolute pressure, P.
3. Plot the graph measured and calculated slope as a function of absolute
pressure.
4. Measure/calculate the slope of the graph using certain points of pressure and
average temperature. Report these values in result section.
Note:
Tv fg
 dT 
  
hfg
 dP  SAT
Tv
 dT 
Plot   versus P and fg versus P on a same graph.
hfg
 dP SAT
Discussion:
1. Why is it necessary to remove air from the boiler at the beginning of the
experiment?
2. Compare the graph plotted from measured data to that of the calculated data.
3. Discuss any discrepancy and sources of error of the experiment.
4. Discuss the liquid and vapor behavior observed through the experiment
5. Discuss 4 applications of boilers in industries. Elaborate you answer in detail.
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
7.0
EQUIPMENT MAINTENANCE
1.
2.
3.
4.
5.
6.
8.0
SAFETY AND PRECAUTIONS
1.
2.
3.
4.
5.
6.
9.0
Use only distilled water for the test to prolong the boiler’s life.
It is not necessary to drain the water from the boiler as there is no rusting
component in the boiler. In case of draining is necessary, incline the bench to a
side and open the heater flange slowly. Be extremely careful when draining; never
allow water to contact with the heater terminals.
Always check and rectify any leaks.
Always make sure that the boiler vessel is filled with sufficient water to cover the
heater element. Water level at half of the boiler’s height is sufficient to cover the
heating element.
Restore the system to operating conditions after any repair job. Replace a new
seal if necessary.
The unit requires no major maintenance. To prevent unnecessary damage to the
unit, always consult the manufacturer for any maintenance or repair works.
Maintenance and repair must be done by well trained technician. Consult the
manufacturer for any replacement parts.
The unit must be operated under the supervision of trained personnel.
All operating instructions supplied with the unit must be carefully read and
understood before attempting to operate the unit.
Do not open the valves on the level sight tube when the vessel is in operation. The
sight tube is not design to withstand high pressure and high temperature.
Always check and rectify any leaks.
Always make sure that the boiler vessel is filled with sufficient water to cover the
heater element. Water level at half of the boiler’s height is sufficient to cover the
heating element.
Do not touch the hot components of the unit. Be extremely careful when handling
liquid at high temperature.
REFERENCES
Yunus A. Cengal & Michael A. Boles, “Thermodynamics – An Engineering Approach”, 3rd
Edition, 4th Edition, McGraw Hill, 2002.
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SOLTEQ® MARCET BOILER (Model: HE169) ________________________________________________________
Appendix
Pressure, P
(bar)
Gauge
Absolute
Temperature, T
Increase
(0C)
Decrease
(0C)
Average
Tavc (0C)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
1.30
1.40
1.50
1.60
1.70
1.80
1.90
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
6.00
6.50
7.00
7.50
8.00
8.5
9.00
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Average
Tavc (K)
Measured
Slope,
dT/dP
Calculated
Slope,
Tvg/hfg