Title:
Investigation into the efficiencies of a steam plant, heat pump and diesel engine
Symbols:
Symbol
BP
c
Units
W
𝐽
𝑘𝑔𝐾
𝐶𝑂𝑃𝐻𝑃
n/a
𝐶𝑂𝑃𝑅
n/a
𝐶𝑉
𝐶𝑉𝑜
g
ℎ3
ℎ4
M
𝑚̇
𝑚𝑐
𝑚𝑒
𝑚̇𝑓
𝑚̇𝑤
N
𝑄
𝐽
𝑘𝑔
𝐽
𝑘𝑔
𝑚
𝑠2
𝐽
𝑘𝑔
𝐽
𝑘𝑔
𝑘𝑔
𝑘𝑔
𝑠
𝑘𝑔
𝑠
𝑘𝑔
𝑠
𝑘𝑔
𝑠
𝑘𝑔
𝑠
Rpm
𝑚3
𝑠
𝑄𝑐
W
𝑄𝑒
W
𝑄24
r
𝐽
𝑠
𝑚
Meaning
Brake Power
Specific Heat of Water
Coefficient of Performance of
heat pump
Coefficient of Performance of
refigerant
Calorific Value of fuel
Calorific Value of Oil
Acceleration due to gravity
Enthalpy of Saturated Liquid
Enthalpy of Saturated Vapour
Mass
Mass flow
Condensed water flow rate
Evaporator water flow rate
Mass flow of oil
Mass flow of water
Speed
Volume flow rate
Heat
extracted
condensed water
Heat
extracted
evaporated water
Heat Added by boiler
Torque arm radius
1
from
from
Dynamometer Load
S
𝑁
s
T
N
𝑘𝑔
ℎ
𝑊
𝑁𝑚
𝑡
𝑠
𝑇𝐷
𝑁𝑚
Dynamometer Torque
𝑇𝑖
°𝐶
Condenser inlet temp
𝑇𝑜
°𝐶
Condenser outlet temp
𝑡1
𝑠
Time
𝑡2
𝑠
Time
W
W
Compressor Power
𝑊𝑥
W
Torque Power
𝑥1
𝑚
3
𝑥2
𝑚3
∆𝑡𝑐
°𝐶
∆𝑡𝑒
°𝐶
𝜂𝐵
n/a
Volume of condensate
Change in temperature of
condensed water
Change in temperature of
evaporated water
Boiler Efficiency
𝜂𝑏
n/a
Brake Thermal Efficiency
𝜂𝐶
n/a
Cycle Efficiency
𝜂𝐺
n/a
𝑘𝑔
𝑚3
𝑘𝑔
𝑚3
𝑘𝑔
𝑚3
Generator Efficiency
S.F.C
𝜌
𝜌𝑜
𝜌𝑤
Spring Force
Specific Fuel Consumption
Torque
time
Volume of oil used
Density of fuel
Density of oil
Density of Water
2
Contents
1.
2.
3.
page
Investigation into a boiler, turbine and steam plant efficiency ...................................................... 4
1.1
Introduction ............................................................................................................................ 4
1.2
Objectives................................................................................................................................ 4
1.3
Theoretical Analysis ................................................................................................................ 4
1.4
Experimental Work ................................................................................................................. 5
1.4.1
Apparatus ........................................................................................................................ 6
1.4.2
Procedure ........................................................................................................................ 6
1.5
Results ..................................................................................................................................... 6
1.6
Discussion................................................................................................................................ 6
1.7
Conclusions ............................................................................................................................. 6
Determining the Coefficient of performance for a refrigerator and heat pump system ............... 7
2.1
Introduction ............................................................................................................................ 7
2.2
Objectives................................................................................................................................ 7
2.3
Theoretical Analysis ................................................................................................................ 7
2.4
Experimental Work ................................................................................................................. 8
2.4.1
Apparatus ........................................................................................................................ 8
2.4.2
Procedure ........................................................................................................................ 8
2.5
Results ..................................................................................................................................... 8
2.6
Discussion................................................................................................................................ 9
2.7
Conclusions ............................................................................................................................. 9
Measuring the brake thermal efficiency of a diesel engine.......................................................... 10
3.1
Procedure .............................................................................................................................. 10
3.2
Results ................................................................................................................................... 10
3.3
Discussion.............................................................................................................................. 11
4.
References .................................................................................................................................... 11
5.
Appendices .................................................................................................................................... 11
3
1. Investigation into a boiler, turbine and steam plant efficiency
1.1 Introduction
Steam plants such as moneypoint power station, require a boiler efficiency,
generator efficiency and cycle efficiency as close to ideal values for optimal usage.
This section aims to determine experimentally the boiler efficiency, turbine
efficiency and steam plant efficiency. The full set of results is included in appendix 1.
1.2 Objectives

To calculate the boiler efficiency of the boiler in the University of Limerick

To determine the generator efficiency of the steam plant in the University of
Limerick

To determine the cycle efficiency of the steam plant in the University of Limerick
1.3 Theoretical Analysis
The mass flow rate of oil can be calculated using
𝑚̇𝑓 =
𝑥1
𝜌
𝑡1 𝑜
Eqn. 1
The mass flow rate of water can be calculated using
𝑚̇𝑤 =
𝑥2
𝜌
𝑡2 𝑤
Eqn. 2
The heat added by the boiler
𝑄24 = 𝑚𝑤 [(ℎ4 − ℎ3 ) + 𝑐(𝑇𝑜 − 𝑇𝑖 )]
Eqn. 3
The boiler efficiency can then be calculated
𝜂𝐵 =
𝑄24
(𝐶𝑉𝑜 )𝑚̇𝑓
Eqn. 4
4
The dynamometer torque is obtained using
𝑇𝐷 = 𝑆𝑟
Eqn. 5
Turbine power in kW is
𝑊𝑥 =
2𝜋𝑁𝑇𝐷
60
Eqn. 6
The generator efficiency is
𝜂𝐺 =
𝑉𝐼
𝑄24
Eqn. 7
The cycle efficiency is
𝜂𝐶 =
𝑊𝑥
𝑄24
Eqn. 8
1.4 Experimental Work
Fig. 1 Power Plant efficiency set up
5
1.4.1
Apparatus
Pump, boiler, turbine, generator, condenser, cooling water, thermometer.
1.4.2
Procedure
The power plant (fig. 1) was turned on and allowed to reach equilibrium. The atmospheric
pressure was measured using a barometer. Once the power plant was at equilibrium the
dynamometer load was measured. The temperature was recorded for the inlet and outlet of
the steam and the water. The flow rate of oil and water was measured using a flow meter.
The pressure inside the boiler was measured using a barometer. The turbine speed was
measured using a tachometer. The time it took the excess condensate to fill 30L was
measured. The voltage and current for the system were recorded.
1.5 Results
Table 1 The boiler efficiency, generator efficiency and cycle efficiency of the power plant.
Generator efficiency 𝜼𝑮
Cycle efficiency 𝜼𝑪
Boiler Efficiency 𝜼𝑩
0.850813
0.011688
0.735808
1.6 Discussion
Appendix 1 shows the values obtained experimentally in the power plant and the
various values obtained. The boiler efficiency was 73.5%, 1.16% for cycle efficiency
and 85% for the generator efficiency. The cycle efficiency is extremely low and would
require an improved steam plant set up to increase the cycle efficiency
1.7 Conclusions
The power plant has numerous losses and would require significant changes to
improve cycle efficiency.
6
2. Determining the Coefficient of performance for a refrigerator
and heat pump system
2.1 Introduction
The coefficient of performance for a refrigeration and heap pump systems are
essential in knowing the amount of heat moved for the amount of work put in. The
experiment was carried out twice at two different condenser water flow rates and
plotted on a P-h graph. The full set of data is included in appendix 2.
2.2 Objectives

To find the coefficient of performance of a heat pump

To find the coefficient of performance of refrigeration

To plot the results on a p-h graph
2.3 Theoretical Analysis
𝑊=
3600
166.7𝑡
Eqn. 9
𝑄𝑒 = 𝑚𝑒 𝑐∆𝑡𝑒
Eqn. 10
𝑄𝑐 = 𝑚𝑐 𝑐∆𝑡𝑐
Eqn. 11
𝐶𝑂𝑃𝑅 =
𝑄𝑒
𝑊
Eqn. 12
𝐶𝑂𝑃𝐻𝑃 =
𝑄𝑐
𝑊
Eqn. 13
𝐶𝑂𝑃𝑅 + 1 = 𝐶𝑂𝑃𝐻𝑃
Eqn. 14
7
2.4 Experimental Work
Fig. 2 Schematic of Hilton mechanical heat pump
2.4.1
Apparatus
Flow meter, pressure guage, flow control valve, cooling fan, watt hour meter, thermometer.
2.4.2
Procedure
The flow rate of the condenser was started at 50kg/hr and the system (fig. 2) was allowed to
reach equilibrium. Once equilibrium was reached, the flow rate of the evaporator was
recorded. The temperature and the pressure of the condenser, evaporator and refrigerant
were also recorded. The time for 1 revolution of the wattmeter was recorded. The flow rate
of the condenser was changed to 100kg/hr and the process was repeated.
2.5 Results
Figure 3 is a P-h graph for the heat pump and refrigeration systems, test 1 is the blue line
with test 2 being the red line. Test 1 was carried out at 50 kg/hr of condensed steam with
the second test carried out at 100kg/hr.
8
Fig. 3 P-h graph for 50kg/hr and 100kg/hr condenser flow rate (Bar – kJ/kg plot)
Table 2 Coefficient of performance for a refrigerator and heat pump under two different
condensate flow rates.
condenser flow rate (kg/hr)
𝑪𝑶𝑷𝑹
𝑪𝑶𝑷𝑯𝑷
Test 1
Test 2
50
100
2.385219 1.898336
2.653347 2.337852
2.6 Discussion
Appendix 2 shows the results obtained for the two different condensate flow rates
The theoretical coefficient of performance for the heat pump should be higher than
the coefficient of performance of the refrigeration system (Eqn. X). The heat being
moved from the refrigerant is not 100% efficient therefore the heat pump has a
lower COPHP .
2.7 Conclusions
The process has a higher coefficient of performance when the condenser is going at
a slower speed to allow more heat to be transferred from the steam to the
refrigerant.
9
3. Measuring the brake thermal efficiency of a diesel engine
3.1 Procedure
A load is applied to the diesel engine. The speed was reduced to the lowest stable speed
(1005 RPM). The speed and torque were recorded. Fuel consumption was recorded by using
a graduated cylinder filled with fuel. Engine speed was increased. The process was repeated
for 6 different speeds (1204 RPM, 1407 RPM, 1626 RPM, 1792 RPM and 2078 RPM).
3.2 Results
Figure 4 shows the brake power plotted against engine speed for a diesel engine,
BP
Brake Power (kW)
14
12
10
8
6
BP
4
2
0
0
500
1000
1500
2000
2500
Engine Speed (RPM)
Fig. 4 Brake power of a diesel engine plotted against engine speed (kW-RPM plot)
Figure 5 shows the specific fuel consumption and the brake thermal efficiency plotted
Specific Steam Consumprtion(Kg/kW
h)
Brake Thermal Efficiency (unitless)
separately against varying engine speeds for a diesel engine.
0.4
0.35
0.3
0.25
0.2
S.F.C
0.15
B.T.E
0.1
0.05
0
1005
1204
1407
1626
1792
Engine Speed (RPM)
10
2078
Fig. 5 Specific fuel consumption versus engine speed (Kg/kW h – RPM plot) and
Brake thermal efficiency versus engine speed (n/a – RPM plot) for a diesel engine
3.3 Discussion
The brake thermal efficiency increases as the speed increases until it reaches
1792RPM when it starts decreasing. The brake thermal efficiency was the highest
when the engine speed is at 1792 RPM, meaning the engine is more efficient when
operating at this speed as less fuel is required to create 1kW h. The specific fuel
consumption decreases after 1792RPM which can be caused due to lack of air being
available for the combustion, a turbocharger could be installed to increase the
efficiency of the engine.
4. References
Eason, D. C. (2010). Thermodynamic 2 Spring 2010. Limerick: Universtiy of Limerick.
Eastop, T., & mcConkey, A. (1996). Applied Thermodynamics for Engineering Technologists. New
Jersey: Prentice Hall.
Rogers, G., & Mayhew, Y. (1992). Engineering thermodynamics : work and heat transfer. Essex:
Harlow : Longman Scientific & Technical.
5. Appendices
Appendix 1 the results obtained from the power plant.
Time 𝒕𝟏 to us 𝒙𝟏 of oil
Mass flow of oil 𝒎̇𝒇
Time 𝒕𝟏 to us 𝒙𝟏 of condensate
mass flow of water, 𝒎̇𝒘
Boiler Pressure (bar)
Steam main temp (°𝑪)
Inlet water temp (°𝑪)
h3 (kJ/kg)
c(T3-T1) (kJ/kg)
h4 (kJ/kg)
(h4-h3)xc(T3-T1) (kJ/kg)
Heat added by boiler (kW)
Heat energy in fuel (kW)
Boiler Efficiency 𝜼𝑩
Condenser water flow rate 𝒎̇𝑪
Condenser inlet temp (°𝑪)
Condenser outlet temp (°𝑪)
Heat loss - McC(To-Ti)
Dynamometer load (N)
Torque arm radius (r)
Dynamometer torque (Nm)
Turbine speed (RPM)
Turbine power (kW)
Volts (V)
Current (A)
Electrical power (kW)
Generator efficiency 𝜼𝑮
Cycle efficiency 𝜼𝑪
15 in 3600 s
0.003417
30 in 634 s
0.047319
7
163
10
697
642.6
2764
2709.6
128.2145
0.000174
0.735808
11
3.333333
9.5
19
133
39
0.162
6.318
2265
1.498567
150
8.5
1.275
0.850813
0.011688
Appendix 2 the results obtained from the refrigeration and heat pump system
Test 1
Test 2
refrigerant entry temp evap (°𝑪)
-7
-11
refrigerant exit temp evap (°𝑪)
0
-6
refrigerant entry temp cond (°𝑪)
64
59
refrigerant exit temp cond (°𝑪)
14
12
water entry temp evap (°𝑪)
10
10
water exit temp evap (°𝑪)
3
3
water entry temp cond (°𝑪)
10
10
water exit temp cond (°𝑪)
29
17.5
Compressor power(kW)
condenser flow rate
(kg/hr)
𝒎𝒄 (kg/s)
evaporator flow rate
(kg/hr)
𝒎𝒆 (kg/s)
refrigerant flow rate
(kg/hr)
𝒎𝒇 (kg/s)
Atmospheric pressure
(𝑵/𝒎𝟐 )
Evaporator guage
pressure (𝑵/𝒎𝟐 )
Actual evaporator
pressure (𝑵/𝒎𝟐 )
Condenser guage
pressure (𝑵/𝒎𝟐 )
Actual condenser
pressure (𝑵/𝒎𝟐 )
time for 1 rev of
wattmeter (s)
Refrigerant used
0.417711 0.374275
Heat extracted from evap water (kW)
0.996333
0.7105
Heat extracted from cond water (kW)
1.108333
0.875
𝑪𝑶𝑷𝑹
2.385219 1.898336
𝑪𝑶𝑷𝑯𝑷
2.653347 2.337852
Test 1
Test 2
50
100
0.013889 0.027778
122
87
0.033889 0.024167
4.8
4.1
0.001333 0.001139
102000
102000
138000
100000
240000
202000
930000
730000
1032000
832000
51.7
57.7
134a
134a
Appendix 3. Results obtained during the diesel engine test
CV (MJ/kg)
Test No.
Test Speed N (rpm)
Mg (N)
Spring force s (rpm)
Mg – s (N)
T = (Mg - s)r (Nm)
BP (kW)
t (s)
Q (𝒎𝟑 /𝒔)
𝒎̇ (kg/hr)
S.F.C (kg/kW hr)
Fuel Power (kW)
B.T.E 𝜼𝒃
45
1
1005
88.29
6
82.29
32.916
3.464187311
51
3.92157E-07
1.157647059
0.334175654
14.47058824
0.239395058
𝝆 (𝒌𝒈/𝒎𝟑 )
2
1204
98.1
2.5
95.6
38.24
4.821394
37
5.41E-07
1.595676
0.330957
19.94595
0.241723
12
820
3
1407
117.72
6
111.72
44.688
6.584355
30
6.67E-07
1.968
0.29889
24.600
0.267657
r (m)
4
1626
127.53
5
122.53
49.012
8.345478
24
8.33E-07
2.46
0.29477
30.750
0.271398
0.4
5
1792
137.34
5
132.34
52.936
9.933845
21
9.52E-07
2.811429
0.283015
35.14286
0.28267
6
2078
147.15
0
147.15
58.86
12.80838
16
1.25E-06
3.69
0.288093
46.125
0.277688