Reheating is a method of improving Rankine cycle efficiency which consists of
inter-stage heating of the expanding steam
. After the first stage of expansion which typically reduces initial steam pressure by one-fourth, the steam is heated up (or close) to the maximum heat source temperature.
What is the effect of reheat on Rankine cycle?
The Rankine cycle performance and efficiency can be improved with the reheat cycle as well as by regenerative cycle. It can be improved by
increasing the thermodynamic properties of the steam entering into the turbine
. At the initial stage, increased pressure results in increased expansion ratio.
What is reheating in power plant?
Reheating
increases the efficiency by raising the mean temperature of the heat addition process
, by increasing the steam temperature at the turbine inlet and also by increasing the efficiency of the expansion process in the steam turbine.
What is the advantage of reheating over superheating in the Rankine cycle?
The main practical advantage of reheat (and of superheating) is
the decrease in moisture content in the turbine
because most of the heat addition in the cycle occurs in the vaporization part of the heat addition process. around the cycle, is increased.
What is effect of reheating and regeneration on Rankine cycle?
Reheating of
steam improved the thermal efficiency of the plant
, net work output of turbine, reduction in blade erosion (or quality of steam improve). By regeneration thermal efficiency of the plant can be increased but it does not affect work output from turbine.
Why both reheating and regeneration is used together?
Explanation: When vaporization pressure is high, the reheating of steam is adopted. 2. Why both reheating and regeneration is used together? Explanation: Thus
a modern steam power plant has both reheating
and regeneration.
What is critical point in Rankine cycle?
The critical point is
where the temper- ature and pressure are such that the fluid is no longer classified exclusive- ly as liquid or gas
. It is thought of as a fluid above the critical point. The criti- cal point for water is slightly above 3200 psi.
Why the reheating is needed?
The main purpose of reheating is
to avoid excess moisture in steam at the end of expansion to protect the turbine
. But it need not improve the cycle efficiency. That will depend (as Dmitri said) upon whether the mean temperature of reheat addition is > or < the mean temperature of heat addition before reheat.
What is the efficiency of Rankine cycle?
In modern nuclear power plants, which operate the Rankine cycle, the overall thermal efficiency is
about one-third (33%)
, so 3000 MWth of thermal power from the fission reaction is needed to generate 1000 MWe of electrical power.
What is purpose of reheat cycle?
The purpose of a reheating cycle is
to remove the moisture carried by the steam at the final stages of the expansion process
. In this variation, two turbines work in series. The first accepts vapor from the boiler at high pressure.
How can you increase the efficiency of a 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.
Is one of the advantage of reheat cycle?
Advantages: The advantages of using a reheat cycle are
higher thermal efficiency
, reduced feed water pump power, smaller condenser, smaller boiler, long life of the turbine and less handling of the fuel and firing requirement.
What is the difference between the Brayton cycle and the Rankine cycle?
Rankine cycle is a steam engine, the water is boiled, evaporated, used for work and then condensed for re-use, thus making it a closed cycle. …
The working fluid undergoes a phase change in
the Rankine cycle whereas in Brayton cycle there is no phase change the working fluid always remains in the gaseous phase.
Which is the basic principle of regeneration?
1. What is the basic principle of regeneration? Explanation: In
regeneration steam from condenser is circulated through turbine to increase steam temperature before it enters boiler
. Explanation: Feedwater is preheated so as to decrease the fuel consumption which increases efficiency.
What is regenerating cycle?
This method is called
regenerative feed heating
and the cycle is called the regenerative cycle. This is implemented by extracting or bleeding small quantities of steam from suitable points throughout the turbine stages utilizing the heat contents of an extracted or bled steam.
Why do we regenerate in Rankine cycle?
Regeneration
improves the cycle efficiency by increasing the initial feed water temperature before the water
, water enters the boiler and also helps in controlling the large the large flow rate of steam at the turbine exhaust.
