Steam Plant Complete Report

EXPERIMENT 2: PERFORMANCE OF A STEAM PLANT

THERMODYNAMIC (CLB 20704)

-1-

1.0 INTRODUCTION

1.1 OBJECTIVES

The objectives for this experiment are:

i) To determine the performance characteristics of a steam plant.

ii) To demonstrate the conversion of energy from one form to another and the

measurement of mechanical power.

iii) To demonstrate thermodynamic principle as applied to laboratory scale

steam plant.

1.2 GENERAL BACKGROUND

Steam engine is a heat engine which makes use of the potential energy that

exists as pressure in steam, and then converts it to mechanical work that leads to

the students understanding on some principles of thermodynamics using a

laboratory scale steam plant. Here, a steam plant will demonstrate the principles

of thermodynamics.

The steam plant consists of several component include a boiler, a steam

engine, a condenser and a feed pump. In large power plants, steam turbine are

used but for a small scale laboratory set up, a steam engine is used. Steam engines

were usually used in pumps, locomotive, train and steam ships. And some are still

used it for electrical power generation. Basically, steam is a colorless expansive

and invisible gas resulting from the vaporization of water. Below are the classes

of steam:

a) Saturated steam.

b) Dry steam.

c) Wet steam.



-2-

d) Superheated steam.

e) Highly superheated or gaseous steam.

1.3 THEORY

The cycle of operations in a heat engine is based on Rankine Cycle. The

Rankine cycle more closely approximates to the cycle of a real steam engine

compared to the Carnot cycle. It therefore predicts a lower ideal thermal

efficiency than the Carnot cycle. In the Rankine cycle, heat is added at constant

pressure p1, at which water is converted in a boiler to superheated steam causes

the steam expands at constant entropy to a pressure P2 in a condenser; the water

so formed is compressed at constant entropy to pressure P1 by a feed pump.

Figure 1.3(a): The Rankine Cycle System Figure 1.3(b): Diagram of Rankine Cycle

Based on the figures above, the cycle is consists of four processes whereby:

• From 1 to 2: Isentropic expansion (Steam turbine)

• From 2 to 3: Isobaric heat rejection (Condenser)

• From 3 to 4: Isentropic compression (Pump)

• From 4 to 1: Isobaric heat supply (Boiler)



-3-

For this experiment, firstly consider the complete system of boiler, motor

and condenser surrounded by the control surface. The steady flow energy is given

by:

353211 mhmhQQQQW w −+−−−=

• The overall thermal efficiency of the plant is given by

)( 3

1

1

1

hhms

W

Q

W

w

TH−

==η

• The overall boiler efficiency is given by following this formula

1

1 )(

Q

hhm wsB

−=η

• Rankine cycle efficiency

)( 1

1

hhms

W

w

R−

=η

• Quality of steam

x = h [enthalpy after throttling calorimeter] – hf [@boiler pressure ]

hfg [ @boiler pressure]

• Power W :

60

)21(2 NFFRW

−=

π

R= Brake radius (0.056m)

F = spring load (N)

N = Engine speed (rev. min-1)



-4-

1.4 OVERALL PROCESS DESCRIPTION

Laboratory scale steam plant is designed in order to leads student to

understand some of principles of thermodynamic. The main components in the

steam plant are such as a boiler, steam engine, condenser and the feed pump.

Steam engine is use to convert potential energy to mechanical energy. Therefore,

water is supplied from the reservoir to the boiler by an electric pump and is heated

inside it by using two immersion heaters (3 kW each). The boiler is to incorporate

a safety valve a water level gauge and a blow-down cock. Boiler to be rated up to

6 kW and to generate up to 8 kg per hour of steam with maximum pressure of 400

kPa.

In this case, the water should be always clean and free from minerals to

prevent any errors or contamination occurs inside it. Here, the steam pressure in

the boiler will rises until it reaches to 4 bars. Then, it will undergo the steam

engine, which by steam engine is a prime mover, and the engine has a totally

enclosed crank case, 2 cast iron trunk pistons and overhead piston valve made of

stainless steel. A simple band brake will absorb this engine power form by steam

engine. This steam is expanded in the steam engine to produce a useful work.

Then, the condenser will condense the exhaust steam from the steam engine from

saturated steam to water. This water is then returned back to the reservoir and

pump back into the boiler and the cycle continues.

Furthermore, this apparatus is also consists of a tachometer to measure

speed, an electrical power meter for measuring the heater power input,

thermocouples with read-outs for steam and cooling water temperatures, and

pressure gauges for boiler and engine inlet pressures. This compressive

instrumentation will provide the user with all the reading necessary to perform

experiment in thermodynamics and efficiency.



-5-

2.0 METHODOLOGY

2.1 APPARATUS

Figure 2.1: Steam Motor and Energy Conservation Test Set

2.2 OPERATIONS

2.2.1 SETUP & CHECKS

1. The cooling water supply was supplied to the inlet pipe of the

condenser and the outlet pipe was connected to a suitable drain.

The outlet from the condensate collector was connected to a

suitable drain or container.

2. The unit was connected to the electrical supply.

3. The filter on the end of the boiler pump suction pipe was checked

in place and clean. The end of the pipe was placed into the

reservoir tank supplied. The tank was filled with the clean soft



-6-

water to at least half way. The reservoir was kept half full to ensure

no air is drain in to the pump

4. The upper and lower valves on the boiler sight gauge and the steam

outlet valve on the boiler was opened.

5. The temperature display was switched on.

6. The red emergency stop button was pulled out. The mains supply

and the boiler feed pump was switched on.

7. The pump bleed valve was opened and the pump was operated.

When there is a steady flow of water, with no air bubbles, the

bleed valve was closed and begins to fill the boiler to the upper

mark on the sight gauge. The boiler should fill in 8 to 10 minutes.

When the boiler is full, the boiler steam valve was closed.

8. The band brake was slackening to ensure that the engine is not

loaded. The spring balances was zero.

9. The both heaters was switched on, the indicator lamps will light up

to show the heaters are working. The boiler pressure will rise as

indicated on the boiler pressure gauge. The calorimeter valve was

closed.

2.2.2 START UP

1. When the boiler pressure has reached approximately 60 kN/m2 (0.6

bar), the boiler steam valve was opened until the engine inlet

pressure has reached 40 kN/m2 to 50 kN/m

2 (0.4 bar to 0.5 bar)

2. In one swift movement, the starting knob was pulled upward and

let go. The engine was started to turn. If the engine does not turn:

• Try the starting knob again

• Check the inlet pressure is correct

• Check that the band brake is not too tight



-7-

• Check that the steam engine is not seized- the pulley was watch

at the front of the engine and see if it turns as you pull the

starting knob upwards.

3. The condenser cooling water was turned on and a flow rate for

about 100 liters/hour was adjusted. As the steam pressure rises, the

engine speed will increase, the steam valve was used to keep

engine ticking over at a pressure of between 40kN/m2 and

50kN/m2

4. The heater was switched on in order to keep the boiler pressure up

to sufficient level. The boiler safety valve will begin to operate at

approximately 340kN/m2 (3.4 bars) but will not be fully open until

400kN/m2. The steam at higher boiler pressure was vented through

the safety valve.

5. The apparatus was run for at least 10 minutes to stabilize before

the reading is taken. The level of water in the boiler was checked

regularly. The feed pump was switched on when necessary so that

the level lies between the permitted limits.

2.2.3 EXPERIMENT PROCEDURES

1. The engine was run at the constant speed 2000 rev per min-1 at

varying engine load with:

a) The right hand spring balance was loaded with 2N stages to

20 N.

b) The boiler pressure was varied to achieve constant speed.

(+ 100 rev. min-1)

2. The parameter was recorded in the data sheet

(The volume of condensate was collected in a measuring cylinder

with 1 minute’s interval for the condensate flow rate.)

3. The results were analyzed.



-8-

4. After used:

a) The electrical and water supplies were disconnected.

b) The boiler was allowed to cool down and the boiler drain

valve was opened.

c) The water from the apparatus was drained.

d) The temperature display was switched off.



-9-

3.0 DATA & RESULTS

Table 1: Data for Operating Parameters

*Condenser Cooling Water flowrate, mw = 0.0284 kg/s

Spring

Load

Boiler

Pressure

Boiler

Temp

Engine

Inlet

Pressure

Engine

Speed

Calorimeter

Temp

Condenser

Cooling

H2O inlet

Condenser

Cooling

H2O outlet

Condensate

Flow Rate

Electrical

Power

Condensate

Temp

F1

(N)

F2

(N) P1 (bar) T1 (°C) P2 (bar)

N

(rev/min) T2 (°C) T3 (°C) T4 (°C) Ms (kg/s) Q1 (kW) T5 (°C)

1 0.5 238 139.5 180 1800 101.0 28.8 42.9 161 5.8 41

1 1.0 180 132.6 150 1560 100.8 28.4 40.9 138 5.8 39

1 1.5 200 135.2 180 1480 100.7 28.4 41.4 142 5.8 40

1 2.0 210 136.5 190 1320 100.8 28.4 41.6 142 5.8 40

1 2.5 220 137.8 200 1260 100.8 28.5 41.9 146 5.8 40

1 3.0 230 138.8 210 1230 100.8 28.7 42.4 152 5.8 40.1

1 3.5 240 139.7 220 1160 100.9 28.7 42.6 154.2 5.8 40.1

1 4.0 180 135.7 170 840 100.8 28.7 40.5 130 3.0 40

1 4.5 160 131.3 140 520 100.5 28.7 38.6 112 3.0 39



-10-

Table 2: Calculated Result based on Data Obtained from the Experiment

Quality of steam in

boiler, X

Boiler efficiency, η Power output of the

engine,W1

Rankine cycle efficiency,

ηR

Thermal efficiency, ηTh

0.9752 96.6878 5.2779 0.0941 0.07633

0.9792 103.8674 9.1483 0.001877 0.1364

0.9776 86.0308 13.0187 0.2609 0.1929

0.7933 69.6215 15.4818 0.3834 0.2289

0.9762 87.9649 18.4726 0.3621 0.2716

0.9755 91.3915 21.6393 0.4082 0.3157

0.9749 92.5617 23.8091 0.4435 0.3461

0.9792 150.8869 19.7041 0.4318 0.5086

0.9806 132.2042 13.7225 0.3459 0.3683



-11-

Figure 1: Graph of Condensate Flowrate, kg/s vs. Power Output of the Engine, W1

Figure 2: The reliable result for this experiment

Condensate FlowRate, kg/s vs Power Output of the Engine, W1

0

50

100

150

200

0 5 10 15 20 25

Power Output of the Engine, W1

Con

den

sate

Flo

wR

ate

, k

g/s

Efficiency vs. Power Output

0

0.2

0.4

0.6

0.8

1

1.2

0 5 10 15 20 25

Power Output of engine, W1

Ra

nk

ine E

ffic

ien

cy

, T

herm

al

Eff

icie

ncy

, S

tea

m Q

ua

lity

0

20

40

60

80

100

120

Bo

iler

Eff

icie

ncy

Quality of steam in boiler, X Rankine cycle efficiency, ηR Thermal efficiency, ηTh Boiler Efficiency



-12-

4.0 DISCUSSION

The experiment purposely conducted to make a study on the steam plant operation

and performance in terms of thermodynamic and heat transfer concept. There are 2

different spring loads that we need to adjust in order to observed the significant on the

power output of the engine. For this experiment, F1 is maintaining at 1.0N while the F2

adjusted accordingly by the increment of 0.5N in intervals. The Boiler Pressure and

Temperature readings were taken throughout the experiment for the steam quality and

boiler efficiency calculation. There are others parameters that being recorded like Engine

Inlet Pressure and speed, Calorimeter Temperature, Condenser Cooling Water Inlet

Temperature, Condensate Flowrate and Temperature as well as the Electrical Power

supply to the unit. The experiment carried out until the engine stop running when the load

increases.

For the first trial, the F2 load was set at 0.5N and the Boiler operating condition

recorded at 238 kPa and 139.5oC. By calculation, the steam quality produced was

observed at 0.9752 with the boiler efficiency of about 96.6878%. The power delivered by

the engine calculated to be 5.2779W with the Rankine cycle efficiency observed at

0.0941% with the thermal efficiency indicated at 0.07633%. By referring to the steam

quality produced, there is almost a perfect water vapor phase existence.

The spring load of F2 was set at 1.0N and the steam quality produced was

calculated to be 0.9792 at 180 kPa and 132.6oC of boiler condition. The boiler efficiency

was above than perfect condition in operation, which calculated at 103.8674%. However,

the power generated from the engine observed at 9.1483 W with the Rankine efficiency

of 0.001877% and the thermal efficiency of 0.1364% Eventhough the steam quality

produced was higher compared to the first trial but the possibility of getting the boiler

efficiency greater than 100% is impossible. Thus, this trial was considered failed.

The third trial observed the steam quality produced at 0.9776 with the boiler

efficiency calculated at 86.0308% and the Rankine efficiency observed at 0.2609%. The



-13-

engine power output measured at 13.0187 W with the thermal efficiency recorded at

0.1929%. The fourth trial with the F2 load set at 2.0 N measured the boiler efficiency at

69.6215% with the steam quality produced monitored at 0.7933. This trial also was not a

desired operation since the steam produced was low. However, the power generated by

the engine recorded at 15.4818 W with the thermal efficiency calculated at 0.2289% and

the Rankine efficiency of 0.3834%.

The steam quality recorded at 0.9762 with the boiler efficiency calculated at

87.9649% at F2 set to 2.5 N. The power output of the engine measured at 18.4726 W

while the efficiency of thermal observed at 0.2716% and the Rankine was at 0.3834%.

The boiler efficiency measured at 91.3915% and the steam produced was calculated at

0.9755 when the F2 set at 3.0 N. This resultant in the engine power to produced 21.6393

W with the thermal efficiency measured at 0.3157% together with the Rankine cycle of

0.4082% efficient. The seventh trial was observed with the F2 set at 3.5 N. The efficiency

of the boiler measured at 92.5617% with the Rankine recorded at 0.4435% and the

thermal was calculated at 0.3461%. For this trial, the steam quality generated was

calculated at 0.9749 with the power of the engine recorded at 23.8091 W.

The eight trial was conducted with the F2 set at 3.5 N with the steam produced

observed at 0.9792 and the boiler efficiency recorded higher than expected which is

almost 150.8869%. The last trial carried out with the F2 load was set at 4.5 N. The steam

produced was calculated at 0.9806 with the power delivered from the engine measured at

13.7225. This experiment recorded the efficiency of boiler at 132.2042%, the Rankine

efficiency at 0.3459% and the thermal efficiency at 0.3683%.

From the data and results obtained, the power output from the engine is increasing

by the increment of the spring load difference. Higher load also lead to higher boiler

efficiency with a direct relation to the Rankine and thermal efficiency as well. From the

results, there is clearly indication on the relationship of all this and can best represented

by Figure 2 above which second, eighth and ninth trial was excluded from the graph since

the efficiency of the boiler was impossible.



-14-

Eventhough the experiment completed without any major concern, but there are a

few problems encountered during the experiment, which may influence the result. The

first problem that influenced a lot on the calculation is the Boiler Pressure. In this

experiment, the Boiler Pressure fluctuates and not really constant thus affects on the

enthalpy in the steam quality calculation. Second problem faced by the team is on the

water level control in the boiler. Initial start-up of the steam plant observed at zero level

of the steam since the boiler was empty. Thus, the steam generates might takes a few

minutes to complete and the purity of the steam is a concern for this case.

The spring load also can be one of the contributors to the misleading on the result.

The spring was vibrated throughout the experiment and impacted on the actual delta load.

Since the scale on the spring also was a bit unclear, the exact measurement during setting

up the load was not accurate. The last problem that may influence the result is on the

water volume measurement. Since the condensate collected in the beaker, the accuracy on

the actual volume may impact on the efficiency calculation.



-15-

5.0 CONCLUSION

Based on the result, there is a proven that the steam plant can produced a high

quality of water vapor mixture, which is around 97%. From the relationship, there is

significant increment on the power input of the engine when the load is increasing. Thus,

we can conclude that the higher the load, the higher the power output from the engine.

This direct relationship also linked to the boiler, Rankine and thermal efficiency which

the higher the load, the better the efficiency.



-16-

6.0 TUTORIAL

1. Based on the Figure 2, derive

a. Engine work, W1

Energy Balance for the system:

( ) ( )3543211

3154321

hhmQQQQQW

mhmhWQQQQQ

EWQ

w

w

−+−−−−=

−=−−−−−

∆=−

b. Thermal efficiency, ηTh

General Equation:

in

out

THQ

W=η

Thus, based on Figure 2

32

121

1

:

:

:

mhmhCondenseratBalanceEnergy

WmhmhEngineatBalanceEnergy

mhmhBoileratBalanceEnergy w

=

+=

=

( )

( )

1

3

1

21

1

1

Q

hhm

Q

hhm

Q

W

wTH

TH

TH

−=

−=

=

η

η

η

c. Boiler efficiency, η

( )

1

1

11 )(

Q

hhm

hhmW

EW

wB

w

−=

−=

∆=

η



-17-

2. How to increase the efficiency of the Rankine Cycle? Please explain.

• The basic idea to increase the efficiency of the Rankine Cycle is increase the

average temperature at which heat is transferred to the working fluid in the

boiler or decrease the average temperature at which heat is rejected from the

working fluid in the condenser.

• There have three ways to increase efficiency based in simple ideal Rankine

Cycle:-

� Lowering the Condenser Pressure (Lower T low,avg)

� Lowering the operating pressure of the condenser automatically lowers

the temperature of the steam and thus the temperature at which heat is

rejected.

� Superheating the Steam to High Temperatures (Increase T high,avg )

� The average temperature at which heat is transferred to steam can be

increased without increasing the boiler pressure by superheating the

steam to high temperature.

� Increasing the Boiler Pressure (Increases T high,avg)

� Increase the operating pressure of the boiler, thus automatically raises

the temperature at which boiling takes place.



-18-

3. What are the differences between the actual vapor cycle and the ideal

Rankine Cycle?

Actual Vapor Cycle

Figure 1: Deviation of Actual Vapor Cycle from the Ideal Rankine Cycle

The actual vapor power cycle differs from the ideal Rankine cycle as a result of

irreversiblities in various components. The two common sources of irreversiblities are the

friction and undesired heat loss to the surroundings. Fluid friction causes pressure drops

in the boiler, the condenser, and the connecting pipes. To compensate for these pressure

drops, the water needs to be pumped to a higher pressure. Heat loss from steam to

surroundings takes place when steam flows through the connecting pipes and the various

components. To maintain the same work output, more heat needs to be transferred to the

steam in the boiler. The deviation of actual pumps and turbines from the isentropic ones

can be accounted for by utilizing adiabatic efficiencies



-19-

Ideal Rankine Cycle

Figure 2: T-s Diagram of an Ideal Rankine Cycle

The Rankine cycle is an ideal cycle if water passes through the four components without

irreversibilities and pressure drops. The ideal Rankine cycle consists of the following

four processes, as shown on the T-s diagram above:

• 1-2: Isentropic compression in a pump

• 2-3: Constant pressure heat addition in a boiler

• 3-4: Isentropic expansion in a turbine

• 4-1: Constant pressure heat rejection in a condenser



-20-

7.0 APPENDIX

Steam Quality Calculation

CT

kPa

kPakPaP

01012

325.339

325.1012381

=

=

+=

( )( )

kgkJh

kgkJ

kgkJh

C

C

TableSteamfromerpolationonBased

Cathh

o

o

o

g

/16.2677

/)6.26754.2683(

/)6.2675(

100105

100101

:int

101

=

−

−=

−

−

=

( )( )

( )( )

kgkJh

kgkJ

kgkJh

kPa

kPa

erpolationguBy

kPaath

f

f

f

/53311.579

/19.57326.584

/19.573

325350

325325.339

:intsin

325.339

=

−

−=

−

−

( )( )

( )( )

kgkJh

kgkJ

kgkJh

kPa

kPa

erpolationguBy

kPaath

g

g

g

/9879.2150

/4.21557.2147

/4.2155

325350

325325.339

:intsin

325.339

=

−

−=

−

−

( )

9752.0

/9879.2150

/53311.57916.2677

=

−=

−=

x

kgkJ

kgkJx

h

hhx

fg

fg



-21-

Boiler Efficiency

kgkJh

kgkJkgkJh

xhhh fgf

/17651.2677

)/9879.2150(9752.0/53311.579

1

1

1

=

+=

+=

( )( )

( )( )kgkJh

kgkJ

kgkJh

C

C

Cathh

f

f

o

o

o

fw

/019.587

/75.56716.589

/75.567

135140

1355.139

5.139

=

−

−=

−

−

=

s

kgm

sm

kg

L

m

ml

Lmlm

s

s

002683.0

60

min11000

1000

1

1000

1

min

1613

3

=

××××=

( )

%6878.96

100

8.5

019.58717651.2677002683.0

100)( 1

=

×

−

=

×−

=

B

B

fs

B

kg

kJ

kg

kJ

s

kg

Q

hhm

η

η

η

Power Output of the Engine, W

WW

rpmNmW

NFRW

2779.5

60

)1800()5.0()056.0(2

60

)(2

=

=

∆=

π

π



-22-

Rankine Cycle Efficiency

%0941.0

100

)17651.2677019.587(002683.0

2779.5

100)( 1

=

×

−

=

×−

=

R

R

ws

R

kg

kJ

s

kg

W

hhm

W

η

η

η

Thermal Efficiency

( )( )

( )( )

kgkJh

kgkJ

kgkJh

C

C

Cathh

CT

o

o

o

f

o

/712.171

/53.16744.188

/53.167

4045

4041

41

415

3

3

3

=

−

−=

−

−

=

=

%07633.0

100

)712.171019.587(002683.08.5

2779.5

100)( 3

=

×

−+

=

×−+

=

th

th

ws

th

kg

kJ

s

kg

s

kJ

W

hhmQ

W

η

η

η



-23-

8.0 REFERENCES

1. http://en.wikipedia.org/wiki/Steam_power

2. http://en.wikipedia.org/wiki/Heat_engine

3. http://electron9.phys.utk.edu/phys136d/modules/m3/heatpump.htm

4. http://en.wikipedia.org/wiki/Thermodynamics

5. http://en.wikipedia.org/wiki/Rankine_cycle

6. http://www.taftan.com/thermodynamics/RANKINE.HTM

Steam Plant Complete Report

Documents

Transcript of Steam Plant Complete Report