Ideal power plant

Another important point that should be made is this it is misleading to imply that the value of a fuel lies in its heating value. The true measure of a fuel s potential to cause useful change for us is its content of available energy. This fact leads to interesting "discrepancies." For instance, if an ideal power plant were used in the boiler problem, so that the available energy in it were turned completely into electricity, that plant s "thermal efficiency" (nj) would be... 

Presently, designs for radial inflow turboexpanders in sizes up to 70 MW are available for use in geothermal power plants. Following are some of the most important features that make turboexpanders ideal for the reeovery of power from the vast available resourees of pressurized gas streams. 

In the past, for many air pollution control situations, a change to a less polluting fuel offered the ideal solution to the problem. If a power plant was emitting large quantities of SO2 and fly ash, conversion to natural gas was cheaper than instaUing the necessary control equipment to reduce the pollutant emissions to the permitted values. If the drier at an asphalt plant was emitting 350 mg of particulate matter per standard cubic meter of effluent when fired with heavy oil of 4% ash, it was probable that a switch to either oil of a lower ash content or natural gas would allow the operation to meet an emission standard of 250 mg per standard cubic meter. 

Consider a combined power plant made up of two cyclic plants (H, L) in series (Fig. 7.1). In this ideal plant, heat that is rejected from the higher (topping) plant, of thermal efficiency tjh, is used to supply the lower (bottoming) plant, of thermal efficiency tjl, with no intermediate heat loss and supplementary heating. 

Fhosphoric acid does not have all the properties of an ideal fuel cell electrolyte. Because it is chemically stable, relatively nonvolatile at temperatures above 200 C, and rejects carbon dioxide, it is useful in electric utility fuel cell power plants that use fuel cell waste heat to raise steam for reforming natural gas and liquid fuels. Although phosphoric acid is the only common acid combining the above properties, it does exhibit a deleterious effect on air electrode kinetics when compared with other electrolytes ( ) including such materials as sulfuric and perchloric acids, whose chemical instability at T > 120 C render them unsuitable for utility fuel cell use. In the second part of this paper, we will review progress towards the development of new acid electrolytes for fuel cells. 

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 (%). 

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. 

The maximum and minimum temperatures and pressures of a 40 MW turbine shaft output power ideal air Brayton power plant are 1200 K (Ta), 0.38 MPa (P3), 290 K (TO, and 0.095 MPa (Pi), respectively. Determine the temperature at the exit of the compressor Tj), the temperature at the exit of the turbine (P4), the compressor work, the turbine work, the heat added, the mass rate of flow of air, the back-work ratio (the ratio of compressor work to the turbine work), and the thermal efficiency of the cycle. 

Official Properties. The International Association for Properties of Water and Steam (IAPWS), an association of national committees that maintains the official standard properties of steam and water for power cycle use, maintains two formulations of the properties of water and steam. The first is an industrial formulation, the official properties for the calculation of steam power plant cycles. This formulation is appropriate from 0.001 to 100 MPa (0.12-1450 psia) and from 0 to 800 C (32-1472 F) and also from 0.001 to 10 MPa (0.12-145 psia) between 800 and 2000°C (1472 3632 F). This formulation is used in the design of steam turbines and power cycles. IAPWS maintains a second formulation of the properties of water and steam for scientific and general use from 0.01 MPa (extrapolating to ideal gas) at O C (1.45 psia at 32 F) to the highest temperatures and pressures for which reliable information is available. 

On the positive side, fuel cells are ideally suited to mass production. If demand for such power plants increases, we believe that mass production has the potential to reduce costs considerably. Nevertheless, given the continued high costs associated with this type of energy, we believe that the best potential for growth in the short-term lies with stationary systems that provide back-up power for offices and other commercial properties. We anticipate that demand for such systems is likely to continue to grow, but, these are likely to remain the only commercially viable systems—at least in the short-term. 

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