Part 2_marcet Boiler

Equipment for Engineering Education

Experiment Instructions WL 204

G.U.N.T. Gerätebau GmbH Fahrenberg 14 D-22885 Barsbüttel Germany Phone:

++49 (40) 670854.0

Fax:

++49 (40) 670854.42

E-mail:

[email protected]

Web:

http://www.gunt.de

Marcet Boiler

03/2001

WL 204

MARCET BOILER

15

20

5

10

0

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

25

Experiment Instructions Please read and follow the instructions before the first installation!

Publication-no.: 916.000 00 A 204 12 (A)

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WL 204

MARCET BOILER

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

Inhaltsverzeichnis 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2

Unit Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1 Unit Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3

2.2.1

Filling the Boiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2.2

Unit Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2.3

Shutting down the Boiler. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1 Health Hazards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Hazards for Unit and Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4

Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1 Theoretical Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2 Performing the Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.1 Working Sheets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.2 Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5.3 Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.4 Items Supplied. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

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WL 204 1

Introduction The experiment WL 204 Steam pressure curve of saturated steam demonstrates the correlation between steam pressure and heating temperature on an enclosed model steam boiler.

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

An insulated steel vessel is filled with a defined quantity of water and sealed pressure-tight. The water is heated by an electric heater and brought to the boil. To record the heating and steam temperature the unit has a temperature sensor element with an electronic evaluation unit and a digital display. The steam pressure occurring in the boiler during the experiments is calculated and indicated by a mechanical manometer. A safety valve prevents excess pressure build-up in the boiler. The setup of this benchtop unit permits the saturated steam pressure curve of water to be determined steplessly up to a pressure of 18 bar. The measurement can be compared against the tabulated values from the relevant literature. The experiment is executed as a user-friendly benchtop unit. However, for safety reasons it should only be run under the supervision of trained personnel, as experimenting with hot steam by nature involves a certain risk. It is designed only for educational and training purposes.

1 Introduction

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2

Unit Description

2.1

Unit Layout

15

20

5

10

5

25

0

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

6

7

4

8

3

2 11

10

9

1

1 Drain Valve

6 Temperature sensor

2 Heater

7 Manometer

3 Overflow

8 Boiler with insulating jacket

4 Filler opening

9 Temperature gauge

5 Savety valve

10 Heater switch 11 Master switch

Fig. 2.1

WL 204 general view

The main element of the WL 204 unit is the stainless steel steam boiler (8). It has a mineral wool insulating jacket. The filler opening (4) is used to pour water into the boiler. The overflow valve

2 Unit Description

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WL 204

MARCET BOILER (3), closed off by means of a handwheel, is used to ensure the vessel is filled to the correct level.

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

The drain valve (1) can be used to drain the vessel. An electric heater (2) is bolted into the floor of the boiler in such a way that the heating filament protrudes from below into the boiler. A manometer (7) is fitted in the lid of the boiler to provide a direct indication of the boiler pressure. There is also a Pt-100 temperature sensor (6) to measure the boiler temperature, and a safety valve (5) to prevent excess pressure build-up in the boiler. If the safety valve is activated, the excess pressure is discharged to the rear of the unit via a drain pipe. The boiler temperature can be read from the digital display (9) fitted into the switch cupboard. The unit is switched on at the master switch (11). The additional heater switch (10) can be used to switch the heater on and off as required during the experiment.

2.2

Commissioning

2.2.1

Filling the Boiler

4 3

1

Fig. 2.2

Filling the boiler

2 Unit Description

The boiler need only be filled once before the unit is run for the first time. The level should subsequently be routinely checked at regular intervals after a certain number of experiments have been performed. −

Place the benchtop unit on a flat surface.

−

Fit the enclosed section of tubing to the overflow and open the valve (3).

−

Fit the enclosed section of tubing to the drain (1) and close the valve.

3

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WL 204

MARCET BOILER −

Remove the plug from the filler opening and pour water into the boiler until it emerges at the overflow.

ATTENTION!

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

Only ever remove the seal plug when the boiler is fully depressurised !

2.2.2

−

Close off the overflow valve again.

−

Close off the filler opening again with the plug. Make sure the seal is in perfect working order ! The seal of the plug should be inspected approximately every five times when the plug is removed, and should be replaced depending on its condition.

−

It is essential that the drain pipe of the pressure relief valve (5) should be connected to an additional fabric hose to discharge the hot steam into the open. The hose must be laid with no kinks or bends, and must be fixed to prevent it moving.

Unit Connections

ATTENTION! The safety valve may suddenly activate Loud noise ! Large quantities of hot steam will be emitted !

2 Unit Description

−

Connect the unit to the mains electricity supply.

−

Switch on unit at the master switch (11).

−

Press the heater switch (10) to start the experiment. The heater control is limited to a temperature of 200°C in order to prevent excess pressure build-up !

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WL 204

Shutting down the Boiler −

After the experiment switch off the unit at the master switch.

−

Disconnect the unit from the mains power.

−

Leave the boiler to cool down.

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

2.2.3

MARCET BOILER

2 Unit Description

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WL 204

MARCET BOILER

3

Safety

3.1

Health Hazards DANGER OF EXPLOSION! Only remove the seal plug of the filler opening when the boiler is fully depressurised !

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

−

Removing the seal plug under pressure will result in uncontrolled explosive emission of hot steam.

DANGER OF SCALDING! Hot steam may be emitted ! Do not touch surfaces during operation ! −

The safety valve may activate suddenly. Loud noise ! Large quantities of hot steam will then be emitted. Never lean over the boiler while the experiment is in progress. Keep away from the boiler lid and the safety valve drain pipe.

−

Exposed boiler surfaces and fittings become hot during operation!

DANGER OF ELECTRIC SHOCK! Caution: high voltage

3 Safety

−

Prior to opening the switch cupboard, unplug the mains power plug.

−

Work on the electrical system is only to be performed by suitably qualified personnel.

−

Protect the electrical system from damp, splashing water and condensation.

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WL 204

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

3.2

3 Safety

MARCET BOILER Hazards for Unit and Function −

ATTENTION! Do not operate the unit unsupervised.

−

ATTENTION! Do not modify or disable the fitted safety devices.

−

ATTENTION! Use only clean water for the experiment.

−

ATTENTION! Never run the boiler without water. There is a risk of the filament overheating.

−

DANGER OF FIRE! Do not place combustible materials in the vicinity of the unit.

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MARCET BOILER

WL 204 4

Experiments

4.1

Theoretical Introduction

Steam temperature in °C

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

While water boils in an open vessel at a temperature of 100°C, it does not turn to steam in an enclosed vessel, such as a steam boiler, until a higher temperature.

Steam pressure in bar

The heat initially causes water molecules to evaporate. This causes the pressure in the steam chamber, and thus in the water, to rise. As the steam pressure rises the boiling point temperature also increases, because the water molecules encounter increased resistance as they attempt to move from liquid to gas form. Consequently, each steam pressure has an accompanying precisely defined boiling point temperature (cf. Fig. 4.1).

Fig. 4.1

Boiling point curve for water

4.2

Performing the Experiment

4 Experiments

−

Prepare the benchtop unit as described in section 2.2.

−

Switch on the unit at the master switch.

−

Switch on the heater at the heater switch and heat up the boiler.

−

Log the boiler pressure and temperature values in increments of approximately 0.5 bar (table template 5.1).

−

Enter the measured values in the diagram (diagram template 5.2).

−

Compare your own measurements with the values from the literature. Discussion

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MARCET BOILER

WL 204

Temperature in °C

( relative )

measured

According to literature

0,5

111,7

111,37

1

120,6

120,23

1,5

127,1

127,43

2

133,2

133,54

2,5

138,5

138,87

3

143,0

143,62

4

150,5

151,84

5

157,4

158,84

6

163,4

164,96

7

168,9

170,41

8

173,6

175,36

9

178,1

179,88

10

182,2

184,07

11

185,9

187,96

12

189,5

191,61

13

192,9

195,04

14

196,1

198,29

15

199,1

201,37

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

Pressure in bar

Fig. 4.2

Temperatur in °C

Example of a measurement

It is seen that the measured values are lower than the expected values by a virtually constant amount. There are a number of reasons for this systemic error. The primary influence on the deviation is the inertia of the temperature measurement. The temperature sensor probe is not in direct contact with the water in the boiler. The tube in which it is encased

4 Experiments

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WL 204

MARCET BOILER results in a number of heat transfer barriers which impair the transfer of heat and systemically corrupt the measurement.

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

Another influence is the fact that the water in the boiler is converted only by convection, and so the heat distribution may be uneven.

4 Experiments

10

WL 204

MARCET BOILER

5

Appendix

5.1

Working Sheets

Pressure, relative [bar]

Pressure, absolut [bar]

Steam temperature [°C]

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

0,5 1 1,5 2 2,5 3 4 5 6 7 8 9 10 11 12 13 14 15

Fig. 5.1

5 Appendix

Table template for measurement recording

11

Steam pressure in bar

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

DTP_4 03/2001

WL 204

Fig. 5.2

5 Appendix

MARCET BOILER

Boiling point curve for water

12

Steam temperature in °C

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WL 204

5.2

MARCET BOILER

Tables

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

Pressure, relative [bar] 0.0 0.5 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 Fig. 5.3

5 Appendix

Pressure, absolut [bar] 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0

Steam temperature [°C] 99.63 111.37 120.23 133.54 143.62 151.84 158.84 164.96 170.41 175.36 179.88 184.07 187.96 191.61 195.04 198.29 201.37 204.31 207.11 209.8 212.37

Steam pressure/temperature table for saturated steam

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WL 204 5.3

MARCET BOILER Technical Data Dimensions L x W x H:

800 x 500 x 850 mm

Weight:

All Rights Reserved G.U.N.T. Gerätebau GmbH, Barsbüttel, Germany 03/2001

Power supply:

approx. 65 kg 230V, 50 Hz, 3 kW

Fill quantity :

4 l

Tank capacity :

5 l

Max. operating pressure (relative) :

18 bar

Max. test pressure (relative) :

32 bar

Operating temperature range : 0 ... 250 °C Temperature sensor:

Pt- 100

Measuring range of manometer: 0 ... 25 bar Seal of filler opening Copper seal

5.4

1/2"

Items Supplied 1 benchtop experimental unit, complete 1 instruction manual 1 packing list

5 Appendix

14