This chapter discusses the procedure followed and the assumptions made while setting up the design point and part load simulation. The NPSS solver uses a set of independent and dependent variables that is declared by the elements and the user. The independents are varied with each solver iteration until the dependent variables satisfy their specified condition [22].
The heat rise element, i.e. nuclear reactor is modeled in such a way that the temperature of helium exiting the reactor and entering the helium turbine is maintained at 1173 K (900 0C). During part load operation of the Brayton cycle, the mass flow rate is reduced. By reducing the reactor power output, the temperature of helium can be maintained at the design point value. Load following
…show more content…
The Brayton cycle is sized based on the quality of the steam that enters the steam turbine. When the heat source is changed from burning coal to the helium turbine exhaust, we must ensure that the turbine exhaust has sufficient thermal energy to generate the required steam.
For the 300 MW steam plant currently under analysis, steam is required at 723 K (450 0C), 10.34 MPa and a mass flow rate of 330 kg/s. The steam turbine extracts 312.5 MW of power at 84 percent adiabatic efficiency. With the generator loss at 4 percent, the electrical output is 300 MWe. A mechanical pump is used to pump the water into the heat exchanger where it absorbs the heat from the helium turbine exhaust before entering the steam turbine. Design point specifications are given in Table 4-1.
Table 4 1 Steam Cycle Design Point
…show more content…
In order to maintain synchronous speeds with the gas turbine while still reducing or increasing power output, the engine must be properly controlled [27]. “The control of the engine depends on where in the part-load curve the engine is operating” [27].
The reduction in mass flow rate causes the compressor pressure ratio and efficiency to drop [27]. As the mass flow rate is reduced, the turbine exhaust gas temperature increases to maintain energy balance [27]. The mass flow rate of helium can be decreased to a limit until either material restrictions at the turbine exit or heat exchanger inlet prohibit the higher temperatures [27] or the efficiency of the turbomachinery falls below an acceptable level.
There is a coupling effect between the two systems when the Brayton cycle is operated at part load. The coupling occurs due to two constraints; helium must be cooled to its design point temperature after passing through the heat exchanger and the temperature of steam entering the turbine must be maintained at its design point temperature. The solver calculates the new mass flow rate of water required to cool the helium. The change in mass flow rate of steam due to the reduction of Brayton cycle mass flow rate causes a change in the Rankine cycle power output.
4.3 Rankine Part Load
A period of 5 years from 2008 to 2013 is considered for combustion instabilities performance evaluation before modifications measures are fully implemented. In the past major changes in the gas turbine exhaust gas temperature distribution as well as reduced margin to the combustion stability were observed in all 5 S1 gas turbines, leading to hot/cold spots events and trips, Acceleration Max 1,Max 2 unload events and Max 3 trips.
31. The pressure and volume of an ideal monatomic gas change from A to B to C, as the drawing shows. The curved line between A and C is an isotherm. (a) Determine the total heat for the process and (b) state whether the flow of heat is into or out of the gas.
Nuclear-fuelled power plants are very similar to fossil fuelled power pants, in which they both turn water into steam in order to control the turbine generators that produce energy; the only difference is the source of heat. At nuclear power plants, a nuclear reactor produces and controls the amount of energy that is released when atoms of Uranium split, which is called fission. The heat that is used to make this steam is created by this form of fission. Uranium fuelled nuclear power plants are a clean and efficient way of boiling water to produce the steam that is used to operate the turbine generators within the power plant.
Due to their low overall thermal efficiencies, gas turbines initially had limited uses. As time has passed, many renovations have been implemented to the gas turbine cycle to make it more efficient. Some modifications include: increasing the turbine inlet temperatures, increasing the efficiencies of turbo machinery components, and adding modifications to the basic cycle. In contrast to the ideal cycle, the actual cycle undergoes unavoidable pressure drops during the heat addition and heat rejection processes. In addition, the actual work input to the compressor is always more than the output and the actual work output of the turbine is less than the work input due to irreversibility. These relationships are displayed in the figures below:
Imagine this, there is a huge rarely used energy source that if tapped can solve the energy needs of entire cities. Nuclear energy is energy produced from the uranium 235 the uranium goes through an extensive system of steps and equipment turning it into nuclear energy. First, water is pumped into a box and uranium is a similar box next to it, but it has control and fuel rods inside to make sure the uranium stays in check. Secondly, it becomes steam from the heat of the Uranium, which also gives it the potential to create energy, and then it goes through a turbine and into a generator. The energy comes from the steam when it makes its way into the generator. The rest of the water that does not turn into steam goes through a circuit to another box with cool pipes and hot pipes. Once there, it is all turned into steam as it enters the hot pipes. The steam goes through the hot pipes and into the cooling tower. At the cooling tower, it cools off and becomes once water again. With the information just stated the reader should now have a little understanding of how nuclear energy works from the inside. In this paper, the reader will learn further about how nuclear energy can be clean, how it takes up a lot of space, and how it can be extremely dangerous.
Changliang Liu, H.W., Jinliang Ding, Chenggang Zhen,, An Overview of Modelling and Simulation of Thermal Power Plant. 2011: p.
engine due to its relatively low working temperature. Results show that this technology can help in
In order to perform this analysis the temperatures at the inlet and outlet of the condenser and evaporator were measured for
19. Determine the COP of a heat pump that supplies energy to a house at a rate of 8000 kJ/h for each kW of electric power it draws. Also, determine the rate of energy absorption from the outdoor air. 20. Refrigerant-134a enters the condenser of a residential heat pump at 800 kPa and 35°C at a rate of 0.018 kg/s and leaves at 800 kPa as a saturated liquid. If the compressor consumes 1.2 kW of power, determine (a) the COP of the heat pump and (b) the rate of heat absorption from the outside
Another primary component of nuclear power’s appeal is its high energy density; that is, the fuel used for nuclear power can generally produce more electricity than can be produced by an equivalent amount of fuel in a different power plant technology. For example, coal-fired plants, which meet the most of the global energy demand, are capable of generating 0.35 megawatt-days of electricity for every metric ton of coal burned. By
With this design the turbo-brake power is matched with the turbine at the design speed, which
This energy produces heat and warms the reactors cooling agent (usually water, liquid metal or molted salt)
The turbine wastes a large amount of energy which is converted into other forms of energy such as heat, friction and sound. In order to keep the cost minimal and efficiency of the power plant high, the steam is then condensed and cooled
Vacant heat in the boiler then turns highly purified water into steam which reaches to temperatures of 1000 degrees Fahrenheit / pressures up to 1587.6kg / per square inch then gets transferred to the turbine.
Flow path I cools the stator winding. This flow path passes through water manifold on the exciter end of the generator and from there to the stator bars via insulated bar is connected to the manifold by a separate hose. Inside the bars the cooling water flows through hollow strands. At the turbine end, the water is passed through the similar hoses to another water manifold and then return to the primary water tank. Since a single pass water flow through the stator is used, only a minimum temperature rise is obtained for both the coolant and the bars. Relatively movements due to the different thermal expansions between the top and the bottom bars are thus minimized.