termpaper-practical application of rankine cycle-thermodynamics
TRANSCRIPT
LOVELY PROFESSIONAL UNIVERSITY
PHAGWARA (PUNJAB)
TERM PAPER
SUB: - MEC-203 (ENGINEERING THERMODYNAICS)
COURSE: - B-TECH MECHANICAL ENGG. (LEET-09)
TOPIC:-PRACTICAL APPLICATION OF RANKINE CYCLE
SUBMITTED TO; SUBMITTED BY;
Mr. SREEDHAR SIR, OMKAR KUMAR JHA
(MECHANICAL ENGG.) RH-4901-A12
10902923
INTRODUCTION
The Rankine cycle, like the Stirling cycle is an external combustion cycle. That is the
combustion process is external to cylinder containing the working gas. The Rankine cycle is
characterized by the working gas undergoing a phase change (from liquid to gas) which can be
utilized to achieve high power densities. The most familiar Rankine engine is the steam engine
in which water is boiled by an external heat source, expands and exerts pressure on a piston or
turbine rotor and hence does useful work. A number of the products below make use of this
concept. However, one of them (the Energetix Genlec formerly known as Baxi Inergen) is an
organic Rankine engine which uses an organic fluid (a refrigerant) and operates at temperatures
and pressures much closer to conventional heating and refrigeration appliances. This has the
significant advantage of allowing the use of conventional, mass produced components and
eliminates many of the technical challenges of steam engines.
Dig.:- PRACTICAL APPLICATION
WHERE: - (may not shown in fig... but abbreviated later)
Q = Heat flow rate to/from the system
M Mass flow rate
W Mechanical power used or provided to the system
thermal = Efficiency (thermodynamic)
turbinepump , = Efficiency of feed pump (in compression) and Efficiency of
turbine (In expansion)
.....,,, 4321 hhhh = Specific enthalpy at different points
21, PP = Pressure after and before the compression process.
PROCESS STEPS
There are four processes in the Rankine cycle; these states are identified by number in the
diagram to the right.
Process 1-2: The working fluid is pumped from low to high pressure, as the fluid is a
liquid at this stage the pump requires little input energy.
Process 2-3: The high pressure liquid enters a boiler where it is heated at constant
pressure by an external heat source to become a dry saturated vapor. The input energy
required can be easily calculated using mollier diagram or h-s chart or enthalpy-entropy
chart
Process 3-4: The dry saturated vapor expands through a turbine, generating power. This
decreases the temperature and pressure of the vapor, and some condensation may occur.
The output in this process can be easily calculated using the Enthalpy-entropy chart
Process 4-1: The wet vapor then enters a condenser where it is condensed at a constant
pressure to become a saturated liquid.
In an ideal Rankine cycle the pump and turbine would be isentropic, i.e., the pump and turbine
would generate no entropy and hence maximize the net work output. Processes 1-2 and 3-4
would be represented by vertical lines on the T-S diagram and more closely resemble that of the
Carnot cycle. The Rankine cycle shown here prevents the vapor ending up in the superheat
region after the expansion in the turbine, which reduces the energy removed by the condensers.
EQUATIONS
23 hhM
Qin pumppump
pump PPPhh
M
W
)( 121112
14 hhM
Qout turbinesturbine hhhhM
W )( 4343
in
turbine
in
pumpturbine
thermalQ
W
Q
WW
These are the equations which are used during different
process and calculations of the cycle and entities…
APPLICATIONS
In general science and day to day uses the efficient cycles and process
are being adapted due to their general and easy uses and high efficiency …
There are some applications in use of Rankin: -
A hybrid power generation system: solar-driven Rankine
Engine } & Hydrogen storage
GENERAL SYSTEM DESCRIPTION
The schematic of the proposed solar power –Rankin-based hybrid power
generation system is shown in fig...
The system is consisted of 2 main parts
1-solar collector rankine cycle power generation system described by kuo -et-al
(1998)
As shown in figure 2 the solar radiation is trapped by the solar collector and
energy is transferred to the working fluid circulating in the rankine based thermodynamic
cycle. A turbine generates the mechanical power from the expansion of the working fluid.
2- Hydrogen production and storage system. In this system the excess energy
from a wind power system can be stored by using electrolysis process with the electricity
from the wind turbine to produce hydrogen…..
SOLAR-RANKINE POWER GENERATION UNIT
The Ts (temperature vs. entropy) diagram describing the Rankine cycle process is shown in
Figure . With numbers of the stages matching that of Figure 2. Normal incident solar radiation is
Collected by the parabolic trough collectors and concentrated on the collector absorber tubes.
The working fluid, with the set flow rate m is evaporated while passing through the collector
Absorber tube (stages 1 and 2). An optional auxiliary heater is placed following the collectors
(stages 3 and 4), powered by back up electricity or, in the current hybrid design, by the hydrogen
Burner. This heater, controlled by the collector outlet temperature, serves as the backup power
source during temporary solar down time (such as cloud passing) to prevent the system from
frequent stop, and as the working fluid temperature regulator during inoperative and start-up
times. Mechanical power is produced by passing the working fluid vapor through a steam
turbine (stages 5 and 6), which then drives a generator to produce electricity. The depressurized
vapour is condensed in an air or water-cooled, constant pressure condenser (stages 7 and 8), and
a circulation pump increases working fluid pressure to complete the working cycle (stages 8, 9
and
1). An electricity power control unit directs and allocates the output electricity toward either the
Application usage or the hydrogen production system. The controller also turns on or o! the
pump and the heater according to the situation arising.
For the proposed solar-Rankine hybrid system, the time transient solar radiation controls the
system dynamics. Since the flow rate m is constant during operation, sometimes the excess solar
radiation input would superheat the working Fluid in the collector absorber tubes. And some
other times, the solar radiation input is not sufficient to completely evaporate the working fluid
to
the saturated vapour state at the collector exit (stage 2). To avoid the wet vapour from entering
the turbine, a control unit is recommended to shut off the circulation pump when the solar
radiation is not sufficient to completely evaporate the working fluid. The control unit is often
connected to a temperature sensor in the collector or a pyrheliometer, and programmed to switch
the circulation pump on and o!, depending on the collector temperature readings or the direct
Normal solar radiation reading .
The optional auxiliary heater allows for the greater system flexibility while operating under
Different conditions. The control unit can be extended to integrate the auxiliary heater into the
overall operating schemes. The control unit can be set to turn on the auxiliary heater during
the temporary solar down time (such as cloud passing) to sustain continuous operations. Also,
the
heater can be used to regulate the temperature of the working fluid, and the turbine entrance
conditions.
For the domestic scale solar Rankine systems, the simple, inexpensive and easy to maintain
control system is strongly recommended over the more complicated systems, which may give
better operating efficiencies, but are harder to install, operate and maintain, and are more
expensive.
The sophisticated control systems are more suitable for larger scale power generation systems.
APPLICATION-2
RACER (Rankine Cycle Energy Recovery)
RACER (Rankine Cycle Energy Recovery) was the Naval Sea Systems Command [NAVSEA]
program to design and develop an advanced, combined gas turbine and steam turbine [COGAS]
power plant. The RACER (Rankine Cycle Energy Recovery) system was planned for
development and application to US combatant and auxiliary ships. The system will use the
exhaust energy from an 18MW gas turbine to produce steam and generate power in excess of
6MW for additional ship propulsion power. The RACER System is expected to provide an
overall propulsion fuel reduction upwards of 25%.
The RACER system provides several advantages to a gas turbine powered ship. one of which is
improved fuel efficiency for significant annual fuel savings. This saving does not come free,
however, since; in general, any additional system installed in the ship will have some
maintenance requirements. In keeping with the US Navy's Current emphasis, a key philosophy in
the design of the RACER system was to minimize this maintenance burden.
Marine and land based power plants can produce exhaust products in a temperature range of 350-
1850.degree. F. In most applications, the exhaust products are released to the environment and
the thermal energy is lost. In some instances, however, the thermal energy is further utilized. For
example, the thermal energy from the exhaust of an industrial gas turbine engine (IGT) has been
used as the energy source to drive a Rankine cycle system.
Rankine cycle based power plants Inside a condensing steam turbine - the steam expands below the atmospheric pressure and then
"condenses" while heating the cooling water in a condenser. After the steam exits the outlet of
the condensing turbine, the steam's pressure is so low, it is no longer available for providing
power for industrial applications.
Condensing steam turbines could be used in industrial power plants as condensing tails
connected to back-pressure turbines. In cases of low demand for process steam the steam surplus
is run through the condensing tail to generate more power.
A condensing steam turbine does not differ much from a back-pressure turbine in respect of its'
overall dimensions, steam values (with the exception of outlet pressure), delivery time and price.
The steam condensing equipment requires some additional "balance of plant" investments plus
the availability of cooling water. A 1 MW condensing steam turbine plant needs about 0.1 m3/s
of cooling water.
Organic rankine cycle
The Organic Rankine cycle (ORC) is named for its use of an organic, high molecular mass fluid
with a liquid-vapor phase change, or boiling point, occurring at a lower temperature than the
water-steam phase change. The fluid allows Rankine cycle heat recovery from lower temperature
sources such as industrial waste heat, geothermal heat, solar ponds etc. The low-temperature heat
is converted into useful work, that can itself be converted into electricity. A prototype was first
developed and exhibited in 1961 by Israeli solar engineers Harry Zvi Tabor and Lucien Bronicki.
The working principle of the organic Rankine cycle is the same as that of the Rankine cycle : the
working fluid is pumped to a boiler where it is evaporated, passes through a turbine and is finally
re-condensed.
In the ideal cycle, the expansion is isentropic and the evaporation and condensation processes are
isobaric.
In the real cycle, the presence of irreversibilities lowers the cycle efficiency. Those
irreversibilities mainly occur :
During the expansion : Only a part of the energy recoverable from the pressure difference
is transformed into useful work. The other part is converted into heat and is lost. The
efficiency of the expander is defined by comparison with an isentropic expansion.
In the heat exchangers : The working fluid takes a long and sinuous path which ensures
good heat exchange but causes pressure drops that lower the amount of power
recoverable from the
cycle.
Improvement of the organic Rankine cycle
In the case of a "dry fluid", the cycle can be improved by the use of a regenerator : Since the
fluid has not reached the two-phase state at the end of the expansion, its temperature at this point
is higher than the condensing temperature. This higher temperature fluid can be used to preheat
the liquid before it enters the evaporator.
A counter-current heat exchanger is thus installed between the expander outlet and the
evaporator inlet. The power required from the heat source is therefore reduced and the efficiency
is increased
Applications for the ORC
The organic Rankine cycle technology has many possible applications. Among them, the most
widespread and promising fields are the following:
Waste heat recovery
Waste heat recovery is the most important development field for the Organic Rankine Cycle
(ORC). It can be applied to heat and power plants (for example a small scale cogeneration plant
on a domestic water heater), or to industrial and farming processes such as organic products
fermentation, hot exhausts from ovens or furnaces, flue gas condensation, exhaust gases from
vehicles, intercooling of a compressor, condenser of a power cycle, etc.
Biomass power plant
Biomass is available all over the world and can be used for the production of electricity on small
to medium size scaled power plants. The problem of high specific investment costs for
machinery such as steam boilers are overcome due to the low working pressures in ORC power
plants. The ORC process also helps to overcome the relatively small amount of input fuel
available in many regions because an efficient ORC power plant is possible for smaller sized
plants.
Geothermal plants
Geothermic heat sources vary in temperature from 50 to 350°C. The ORC is therefore perfectly
adapted for this kind of application. However, it is important to keep in mind that for low-
temperature geothermal sources (typically less than 100°C), the efficiency is very low and
depends strongly on heat sink temperature (defined by the ambient temperature).
Solar thermal power
The organic Rankine cycle can be used in the solar parabolic trough technology in place of the
usual steam Rankine cycle. The ORC allows a lower collector temperature, a better collecting
efficiency (reduced ambient losses) and hence the possibility of reducing the size of the solar
field.
CONCLUSION
So according to above all the examples the rankine have a major drawback that it losses the
steam and the heat energy form the boiler or condenser surface….
But overall ,the efficiency of the rankine is good and many of its application is energy efficient
and the highly cost reductive in nature,,,
REFRENCES
1. http://wapedia.mobi/en/Organic_Rankine_cycle
2. http://www.crazyengineers.com/forum/mechanical-civil-engineering/21507-rankine-
cycle-based-power-plants.html
3. http://nptel.iitm.ac.in/courses/IIT-
MADRAS/Applied_Thermodynamics/Module_5/2_%20Rankinecycle.pdf
4. http://www.taftan.com/thermodynamics/RANKINE.HTM
5. http://www.answers.com/topic/rankine-cycle
6. http://en.wikipedia.org/wiki/Rankine_cycle
7. http://www.rankinecycle.com/
8. BOOKS OF THERMOYNAMICS
JOURNALS
http://saeeng.saejournals.org/content/2/1/67.abstract
http://www.waset.org/journals/ijcee/v2/v2-1-3.pdf