The Rankine cycle is the ideal cycle for vapor power plants
; it includes the following four reversible processes: 1-2: Isentropic compression Water enters the pump as state 1 as saturated liquid and is compressed isentropically to the operating pressure of the boiler.
What are differences between ideal and actual Rankine cycle?
| Rankine Cycle Representation is as follows on P-v and T-s diagrams: | Ideal Rankine Cycle 1-2 ‘ -b-3 ‘ -4 ‘ -1 | Actual Rankine Cycle 1-2-b-3-4-1 |
|---|
What is a simple ideal Rankine cycle?
The ideal cycle for vapor power plants is the Rankine cycle. The simple ideal Rankine cycle does not involve any internal irreversibilities and consists of the following four processes: 1-2 Isentropic compression in a pump: Water is pumped from low pressure to high pressure, which is the boiler’s operating pressure.
Why is an actual Rankine cycle not same as the ideal Rankine cycle?
Processes of an actual Rankine cycle will be slightly different with the processes of an ideal Rankine cycle, because
in practice there will be various irreversibilities in various components of Rankine cycle
.
Is the ideal Rankine cycle reversible?
Rankine cycle is a heat engine comprised of
four internally reversible processes
. and reversible (isentropic), the pump and the turbine, the only energy interaction with surroundings is work.
How does an ideal Rankine cycle work?
The Rankine cycle or Rankine Vapor Cycle is the process widely used by power plants such as coal-fired power plants or nuclear reactors. In this mechanism,
a fuel is used to produce heat within a boiler, converting water into steam which then expands through a turbine producing useful work
.
What is the advantage of Reheat Rankine cycle over the ideal Rankine cycle?
The reheat cycle has more benefit in the LP turbine due to the decrease in the wetness that causes
reduction of last-stage blade erosion
which occurs by high-speed water droplets in the saturated steam hitting on the blade.
What is ideal Reheat Rankine cycle?
An ideal reheat Rankine cycle
operates between the pressure limits of 10 kPa and 8 MPa, with reheat being done at 4 MPa
. The temperature of steam at the inlets of both turbines is 500°C and the enthalpy of steam is 3185 kJ/kg at the exit of the high-pressure turbine and 2247 kJ/kg at the exit of low-pressure turbine.
What is the difference between Rankine cycle and Brayton cycle?
The key difference between Rankine cycle and Brayton cycle is that
the Rankine cycle is a vapour cycle, whereas the Brayton cycle is a cycle between liquid and vapour phases
. Both the Rankine cycle and Brayton cycle are thermodynamic cycles.
What is ideal regenerative cycle?
In an ideal regenerative Rankine cycle,
steam enters the turbine at the boiler pressure and expands isentropically to an intermediate pressure
. Some steam is extracted at this state and routed to the feedwater heater, while the remaining steam continues to expand isentropically to the condenser pressure.
What do you understand by ideal regenerative cycle Why is it not possible in practice also give actual regenerative cycle?
The ideal regenerative cycle is not practically possible because
a heat exchanger cannot be installed inside the turbine as there are more chances for the erosion of the turbine blade
(last stage). The thermal efficiency of the ideal regenerative cycle is equal to that of the Carnot cycle.
How can I improve my Rankine cycle?
- Decreasing the condenser pressure. The effect of lowering the condenser pressure on the Rankine cycle efficiency is illustrated on a T-s diagram on the left. …
- Superheating the steam to a high temperature. …
- Increasing the boiler pressure.
What are different factors that makes Rankine cycle internally and externally irreversible?
Concept: Internal irreversibility of Rankine cycle is caused by
fluid friction, throttling, and mixing
. Due to fluid friction the expansion and compression process are not reversible and entropy of the fluid in both increases.
Is the Rankine cycle irreversible?
Although
the ideal Rankine cycle is internally reversible
, there are still external irreversibilities because of the temperature change in the heat addition process.
What four processes make up the simple ideal Rankine cycle?
The ideal Rankine cycle consists of the following four processes, as shown on the T-s diagram on the left:
1-2: Isentropic compression in a pump
.
2-3: Constant pressure heat addition in a boiler
.
3-4: Isentropic expansion in a turbine
.
Why the Rankine cycle is preferred over the Carnot cycle in steam power plants?
Carnot cycle is a theoretical cycle whereas the Rankine cycle is a practical one. Carnot cycle ensures the maximum efficiency under ideal conditions, but the Rankine cycle
ensures the operation in real conditions
. The efficiency obtained by the Rankine cycle is always lower than that of the Carnot cycle.
Which ideal process is carried out at the turbine in vapour power cycle?
Q3. Which ideal process is carried out at the turbine in vapour power cycle? Q5. In the following T-s diagram of Rankine cycle, process (1-2) is heat addition in boiler, process (2-3) is an expansion at turbine, process (3-4) is a condensation process and process (4-1) is a pumping process at feed pump.
Which ideal process is carried out at the turbine in vapour power cycle *?
| Q. Which ideal process is carried out at the turbine in vapour power cycle? | A. reversible adiabatic compression | B. reversible adiabatic expansion | C. reversible constant pressure heat addition | D. reversible constant pressure heat rejection |
|---|
How does an organic Rankine cycle work?
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, passed through an expansion device (turbine, screw, scroll, or other expander), and then through a condenser heat exchanger where it is finally re-condensed.
Why is the Rankine cycle used?
Rankine cycle, in heat engines, ideal cyclical sequence of changes of pressure and temperature of a fluid, such as water, used in an engine, such as a steam engine. It is used
as a thermodynamic standard for rating the performance of steam power plants
.
Which process does Rankine cycle contain?
Explanation: Working fluid in Rankine cycle undergoes 4 processes,
expansion in turbine, heat addition in Boiler, heat rejection in Condenser and compression in pump
.
Which is more efficient reheat cycle or the regenerative cycle?
Analysis shows that
regenerative cycle
is more efficient compare to reheat cycle for a given set of operating conditions.
Why reheat system improves efficiency?
A high reheat pressure increases the the moisture content at turbine exhaust which results in scaling and it should be optimised
. Thus the work produced is increased ,thereby efficiency increases.
How can the efficiency of Rankine cycle be improved Mcq?
The thermal efficiency of the Rankine cycle can be increased by the
use of regenerative heat exchange
.
What is supercritical Rankine cycle?
Technical options for Organic Rankine Cycle systems
A supercritical or transcritical cycle is
a cycle with a maximum pressure higher than the critical one
. Working fluid is heated up from subcooled liquid to superheated vapor with a smooth transition above the critical point.
Why is the Rankine cycle modified?
This cycle is known as modified Rankine cycle. The reason for the early release is that
at the lower pressure the specific volume of steam is high
. In order to accommodate such rapidly expanding steam, large cylinder volume is necessary and the extra work obtained is very small.
What is the purpose of reheat cycle Mcq?
The main advantage of the reheat cycle is that it
increases the dryness fractions of steam at condenser inlet thus making it possible to use higher boiler pressure
. It also increases the net-work output thus decreasing the mass flow rate of steam required for the same power output.
