Power-plant cycle

Since the oceans comprise over 70% of the earth s surface area, the absorbed solar energy that is stored as latent heat of the oceans represents a very large potential source of energy. As a result of variation in the density of ocean water with temperature, the ocean water temperature is not uniform with depth. Warm surface ocean water with low density tends to stay on the surface and cold water with high density within a few degree of 4°C tends to settle to the depths of the ocean. In the tropics, ocean surface temperatures in excess of 25° C occur. The combination of the warmed surface water and cold deep water provides two different temperature thermal reservoirs needed to operate a heat engine called OTEC (ocean thermal energy conversion). Since the temperature difference of the OTEC between the heat source and the heat sink is small, the OTEC power plant cycle efficiency... 

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. 

Dry Towers and Wet-Dry Towers for the Indirect Power Plant Cycle Hansen, E. P. 

Power Plant Cycles for Dry Cooling Towers Leung, P. Moore, R. E. 

In order to determine the costs of essergy A for each interconnecting stream between components, it was found necessary to assign a principal purpose of function to each component (or device, unit, etc.) which would be paid for by a principal product, measured by its essergy content. This scheme which we now call essergetic functional analysis (25), worked fairly well for direct sea water conversion (11,12,13,14,23,24), but it seemed to fail for a simple steam power plant cycle (which was... 

Figure 1. An abbreviated representation of a steam power plant cycle. The numbers 1,2,3,4,5,6, and 7 correspond respectively to the boiler, first turbine stage, second turbine stage, condenser, first feedwater pump, feedwater heater, and second feedwater pump. This first and second turbine stages may both lie inside a single-turbine (viewed as a single piece of equipment) with steam being tapped from a point near the middle of the turbine.

More efficient coal utilization can be realized with combined power plant cycles. For instance, the post combustion gases of a conventional combustor or an advanced MHD system can be further utilized to drive a gas or steam turbine. However, the sustained durability of downstream turbine or heat exchanger components requires minimal transport of corrosive fuel impurities. Control of mineral-derived impurities is also required for environmental protection. For the special case of open cycle-coal fired MHD systems, the thermodynamic activity of potassium is much higher in the seeded combustion gas (plasma) than in common coal minerals and slags. This results in the loss of plasma seed by slag absorption and is of critical concern to the economic feasibility of MHD. 

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... 

Figure (4) shows the scheme of the reference scenario where the fuel oil is used in steam power plant cycle. The substitution of the namral gas with the... 

Ammonia 0.2-3 mg of N per liter Water in power plant cycles Spectrophotometry... 

Kumar, N., Besuner, P.M., Lefton, S.A., Agan, D.D., Douglas, D.H., 2012. Power Plant Cycling Costs. AES 12047831-2-1. Aptertek Aptech, National Renewable Energy Laboratory. http //wind.rtrel.gov/public/WWIS/APTECHfinalv2.pdf. 

Discussion of the conversion of heat to work with a reversible heat engine - the Carnot cycle - essential for the development of an analytical statement of the second law (and, to bring this ideal engine closer to reality, the very real power plant cycle - for the production of electricity from fuels - is described briefly). 

To relate the somewhat abstract Carnot cycle to the real world, we consider - after the Examples 3.2 and 3.3 - the very real power plant cycle, used for the production of electricity from thermal energy. 

Most, by far, electric energy is produced by the combustion of fossil fuels. The resulting thermal energy is converted in part into mechanical energy - which is then converted into electrical one - while the remaining is discarded or, on occasion, used for process heating purposes. The process is carried out in what is referred to as a power plant cycle. 

We are now ready to calculate the thermal efficiency, and some other pertinent quantities, of a power plant cycle. To this purpose let us assume that the simple power plant of Section 3.6 operates as follows ... 

A close examination of the amounts of heats involved in these steps, 629, 1752 and 536 (all in kJ/kg) respectively for the power plant cycle of Example 3.12, suggests that the most important one, with respect to efficiency, is the temperature at which water is vaporized which, in turn, is determined by the boiler pressure. 

Note. The water used in power plant cycles must be very pure to avoid corrosion of the turbine blades. In practice, therefore, the exhaust steam is used to generate the process steam through a heat exchanger, not directly (see Chapter 5). 

An inventor claims that he can avoid the condenser in a power plant cycle -and the resulting loss of energy there - by compressing the exhaust from the turbine vapor directly into the boiler. Identify the problems you see with this approach. 

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