Rankine cycles power plant

Fossil Fuel-Fired Plants. In modem, fossil fuel-fired power plants, the Rankine cycle typically operates as a closed loop. In describing the steam—water cycle of a modem Rankine cycle plant, it is easiest to start with the condensate system (see Fig. 1). Condensate is the water that remains after the steam employed by the plant s steam turbines exhausts into the plant s condenser, where it is collected for reuse in the cycle. Many modem power plants employ a series of heat exchangers to boost efficiency. As a first step, the condensate is heated in a series of heat exchangers, usually sheU-and-tube heat exchangers, by steam extracted from strategic locations on the plant s steam turbines (see HeaT-EXCHANGETECHNOLOGy). 

Another advantage is that the IGCC system generates electricity by both combustion (Brayton cycle) and steam (Rankine cycle) turbines. The inclusion of the Brayton topping cycle improves efficiency compared to a conventional power plant s Rankine cycle-only generating wstem. Typically about two-thirds of the power generated comes from the Brayton cycle and one-third from the Rankine cycle. 

Polytropic process, 68-69 Potential energy, 14-17, 22-24, 31-33, 212-213 Power-plant cycles, 247-271 Rankine, 250-253 regenerative, 255-256 thermodynamic analysis of, 556-561 Poynting factor, 329 Pressure, 9-11 critical, 55-56, 571-572 partial, 300... 

Because of the simplicity and reUabiUty of the Rankine cycle, faciUties employing this method have dominated the power industry in the twentieth century and typically play an important role in most modem combined-cycle faciUties. Water is the working fluid of choice in nearly all Rankine cycle power plants because water is nontoxic, abundant, and low cost. 

Power plants based on the Rankine thermodynamic cycle have served the majority of the world s electric power generation needs in the twentieth century. The most common heat sources employed by Rankine cycle power plants are either fossil fuel-fired or nuclear steam generators. The former are the most widely used. 

One form of solar heat does offer interesting possibilities and is refeiTcd to as OTEC (Ocean-Thermal Energy Conversion). The OTEC power plant principle uses the solar heat of ocean surface water to vaporize ammonia as a working fluid in a Rankine cycle. After the fluid is expanded in the turbine, it is condensed by the 22°C colder... 

The most effective cycle is the Brayton-Rankine cycle. This cycle has tremendous potential in power plants and in the process industries where steam turbines are in use in many areas. The initial cost of this system is high however, in most cases where steam turbines are being used this initial cost can be greatly reduced. 

In a Rankine power plant, the steam temperature and pressure at the turbine inlet are 1000°F and 2000 psia. The temperature of the condensing steam in the condenser is maintained at 60° F. The power generated by the turbine is 30,000 hp. Assuming all processes to be ideal, determine (1) the pump power required (hp), (2) the mass flow rate, (3) the heat transfer added in the boiler (Btu/hr), (4) the heat transfer removed from the condenser (Btu/hr), and (5) the cycle thermal efficiency (%). 

Water circulates at a rate of 80kg/sec in an ideal Rankine power plant. The boiler pressure is 6 MPa and the condenser pressure is lOkPa. The steam enters the turbine at 600°C and water leaves the condenser as a saturated liquid. Find (1) the power required to operate the pump, (2) the heat transfer added to the boiler, (3) the power developed by the turbine, (4) the thermal efficiency of the cycle. 

Steam is generated in the boiler of a steam power plant operating on an ideal Rankine cycle at 10 MPa and 500° C at a steady rate of 80 kg/sec. The steam expands in the turbine to a pressure of 7.5 kPa. Determine (1) the quality of the steam at the turbine exit, (2) rate of heat rejection in the condenser, (3) the power delivered by the turbine, and (4) the cycle thermal efficiency (%). 

A steam power plant operates on the Rankine cycle. The steam enters the turbine at 7 MPa and 550°C. It discharges to the condenser at 20 kPa. Determine the quality of the steam at the exit of the turbine, pump work, turbine work, heat added to the boiler, and thermal cycle efficiency. 

COMMENTS The advantage of using reheat is to reduce the moisture content at the exit of the low-pressure turbine and increase the net power of the Rankine power plant. The one reheat Rankine basic cycle shown in Fig. 2.13 can be expanded into more than one reheat if desired. In this fashion it is possible to use higher boiler pressure without having to increase the maximum superheater temperature above the limit of the superheater tubes. 

Consider a steam power plant operating on the ideal reheat Rankine cycle 1 kg/sec of steam flow enters the high-pressure turbine at 15 MPa and 600° C and leaves at 5 MPa. Steam is reheated to 600° C and enters the low-pressure turbine. Exhaust steam from the turbine is condensed in the condenser at lOkPa. Determine ... 

Consider a steam power plant operating on the ideal regenerating Rankine cycle 1 kg/sec of steam flow enters the turbine at 15 MPa and 600°C and is condensed in the condenser at lOkPa. Some steam leaves the high-pressure turbine at 1.2 MPa and enters the open feed-water heater. If the steam at the exit of the open feed-water heater is saturated liquid, determine (1) the fraction of steam not extracted from the high-pressure turbine, (2) the rate of heat added to the boiler, (3) the rate of heat removed from the condenser, (4) the turbine power produced by the high-pressure turbine, (5) the turbine power produced by the low-pressure turbine, (6) the power required by the low-pressure pump, (7) the power required by the high-pressure pump, and (8) the thermal cycle efficiency. 

Determine the power required by the compressor, power required by pumps 1 and 2, power produced by turbines 1, 2, and 3, rate of heat added by the nuclear reactor, net power produced by the Brayton gas turbine plant, net power produced by the Rankine plant, rate of heat removed by coolers 1 and 2, rate of heat exchanged in the heat exchanger, rate of heat added in the gas burner, mass rate flow of helium in the Brayton cycle, mass rate flow of steam extracted to the feed-water heater (mixing chamber), cycle efficiency of the Brayton plant, cycle efficiency of the Rankine plant, and cycle efficiency of the combined Brayton-Rankine plant. 

A Rankine/Rankine combined cycle is shown in Fig. 5.16. The exhaust from the top steam turbine (TURl) is hot enough to generate freon vapor in a waste-heat boiler. The freon vapor generated can power a freon turbine, thus increasing the total work produced. The Rankine/Rankine combined cycle has a thermal efficiency greater than either a steam or freon cycle may have by itself. The power plant occupies less area, and the fuel requirements are less. 

The cycles considered so far in this chapter are power cycles. However, there are applications in which Rankine cycles are used for the combined supply of power and process heat. The heat may be used as process steam for industrial processes, or steam to heat water for central or district heating. This type of combined heat and power plant is called cogeneration. A schematic cogeneration plant is illustrated in Fig. 5.19. A different schematic cogeneration plant is illustrated in Fig. 5.20. 

Hungary). The cost of the project is estimated at 3.7 million, and the depth of the wells is from 2,900 to 3,200 m. In Connecticut, UTC Power signed agreements with Raser Technology, UT for 30 mW Rankine cycle-based geothermal power plants. 

In a combined-cycle power plant, electricity is produced by two turbines, a gas and a steam turbine. The term combined cycle comes from the fact that the combustion gas turbine operates according to the Brayton cycle and the steam system operates according to the Rankine cycle. As shown in Figure 2.115, the dual-shaft combined-cycle plant consists of a gas turbine (GT)... 

Most modem power plants operate on a modification of the Rankine cycle that incorporates feedwater heaters. Water from the condenser, rather than being pumped directly back to the boiler, is first heated by steam extracted from the turbine. This is normally done in several stages, with steam taken from the turbine at several intermediate states of expansion. An arrangement with four feedwater heaters is shown in Fig. 8.5. The operating conditions indicated on this figure and described in the following paragraphs are typical, and are the basis for the illustrative calculations of Example 8.2. 

A power plant operating on heat recovered from the exhaust gases of internal-combustion < uses isobutane as the working medium in a modified Rankine cycle in which the upper pressure I is above the critical pressure of isobutane. Thus the isobutane does not undergo a change of p" as it absorbs heat prior to its entry into the turbine. Isobutane vapor is heated at 4,800 kPa to 2 and enters the turbine as a supercritical fluid at these conditions. Isentropic expansion in the turh produces superheated vapor at 450 kPa, which is cooled and condensed at constant pressure, resulting saturated liquid enters the pump for return to the heater. If the power output of the modi Rankine cycle is 1,000 kW, what is the isobutane flow rate, the heat-transfer rates in the heater condenser, and the thermal efficiency of the cycle ... 

Power plants can be built to operate on a cycle that departs from the Rankine cycle only to the extent that the work-producing and work-requiring steps are irreversible. We show in Fig. 8.4 the effects of these irreversibilities on steps 2 - 3 and 4 -> 1. The paths are no longer vertical, but tend in the direction of increasing entropy. The turbine exhaust is normally still wet, but as long as the moisture... 

Steam enters the turbine of a power plant operating on the Rankine cycle (Fig. 8.3) at 3,500 kPa and exhausts at 20 kPa. To show the effect of superheating on the performance of the cycle, calculate the thermal efficiency of the cycle and the quality of the exhaust steam from the turbine for turbine-inlet... 

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