Yunus A. Çengel,
University of Nevada, Reno
Michael A. Boles,
North Carolina State University
| Binary vapor cycle | is a vapor cycle in which the condenser of the high-temperature cycle (also called the topping cycle) serves as the boiler of the low-temperature cycle (also called the bottoming cycle). That is, the heat output of the high-temperature cycle is used as the heat input to the low-temperature one.
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| Boiler | is basically a large heat exchanger where the heat originating from combustion gases, nuclear reactors, or other sources is transferred to the water essentially at constant pressure.
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| Bottoming cycle | is a power cycle operating at low average temperatures that receives heat from a power cycle operating at higher average temperatures.
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| Closed feedwater heater | is a feedwater heater in which heat is transferred from the extracted steam to the feedwater without any mixing taking place. The two streams are typically not at the same pressures, since they do not mix. In an ideal closed feedwater heater, the feedwater is heated to the exit temperature of the extracted steam, which ideally leaves the heater as a saturated liquid at the extraction pressure. In actual power plants, the feedwater leaves the heater below the exit temperature of the extracted steam because a temperature difference of at least a few degrees is required for any effective heat transfer to take place.
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| Cogeneration | is the production of more than one useful form of energy (such as process heat and electric power) from the same energy source.
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| Combined gas-vapor cycle, or just the combined cycle | is the gas-turbine (Brayton) cycle topping a steam-turbine (Rankine) cycle, which has a higher thermal efficiency than either of the cycles executed individually.
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| Condenser | is a heat exchanger in which a vapor, such as steam, condenses to the saturated liquid state as the result of heat transfer from the vapor to a cooling medium such as a lake, a river, or the atmosphere.
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| Feedwater heater | is the device where the feedwater is heated by regeneration. This technique is used to raise the temperature of the liquid leaving the pump (called the feedwater) before it enters the boiler. A practical regeneration process in steam power plants is accomplished by extracting, or "bleeding," steam from the turbine at various points. This steam, which could have produced more work by expanding further in the turbine, is used to heat the feedwater instead.
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| Heat rate | is the expression of the conversion efficiency of power plants in the United States and is the amount of heat supplied, in Btu's, to generate 1 kWh of electricity. The smaller the heat rate, the greater the efficiency.
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| Open (or direct-contact) feedwater heater | is basically a mixing chamber, where the steam extracted from the turbine mixes with the feedwater exiting the pump. Ideally, the mixture leaves the heater as a saturated liquid at the heater pressure.
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| Process heat | is required energy input in the form of heat for many industrial processes. The process heat is often obtained as heat transfer from high-pressure, high-temperature steam. Some industries that rely heavily on process heat are chemical, pulp and paper, oil production and refining, steel making, food processing, and textile industries.
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| Pump | is a steady flow device used to increase the pressure of a liquid.
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| Rankine cycle | is the ideal cycle for vapor power plants. The ideal Rankine cycle does not involve any internal irreversibilities and consists of the following four processes: 1-2 Isentropic compression in a pump 2-3 Constant pressure heat addition in a boiler 3-4 Isentropic expansion in a turbine 4-1 Constant pressure heat rejection in a condenser
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| Rankine cycle with reheat | is a modification of the Rankine cycle in which the steam is expanded in the turbine in two stages and reheated in between. Reheating is a practical solution to the excessive moisture problem in the lower-pressure stages of turbines, and it is used frequently in modern steam power plants.
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| Steam generator | is the combination of a boiler and a heat exchanger section (the superheater), where steam is superheated.
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| Topping cycle | is a power cycle operating at high average temperatures that rejects heat to a power cycle operating at lower average temperatures.
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| Trap | is a device that allows condensed steam to be routed to another heater or to the condenser. A trap allows the liquid to be throttled to a lower-pressure region but traps the vapor. The enthalpy of steam remains constant during this throttling process.
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| Utilization factor | is a measure of the energy transferred to the steam in the boiler of a steam power plant that is utilized as either process heat or electric power. Thus the utilization factor is defined for a cogeneration plant as the ratio of the sum of the net work output and the process heat to the total heat input.
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2002 McGraw-Hill Higher Education