Thermodynamic power cycle

The thermodynamic power cycles most commonly used today are the vapor Rankine cycle and the gas Brayton cycle (see Chapter 4). Both are characterized by two isobaric and two isentropic processes. The vapor... 

A numerical example of the carbon dioxide supercritical cycle has been made by Feher (Feher, E.G., The super-critical thermodynamic power cycle. Energy Conversion, vol. 8, pp. 85-90, 1968). The reasons for the neglect of the supercritical cycle until now are not known. 

The maximum achievable efficiency for a thermodynamic power cycle is that of the Carnot cycle, which adds and removes heat from the working fluid at constant temperatures, Th and respectively ... 

Microturbines, pumps, and compressors are key components used to implement thermodynamic cycles for power generation, propulsion, or cooling. Thermodynamic power cycles use a working fluid that changes state (pressure and temperature) in order to convert heat into mechanical work. To achieve high power density, the pressures and temperatures of the fluid in the cycle should be kept to the high levels common at large scale. Common cycles are the Brayton gas power cycle and the Rankine vapor power cycle, described next. 

In the mid 1980s, a new thermodynamic power cycle using a multicomponent working fluid as ammonia-water with a different composition in the boiler and condenser was proposed (known as the Kalina cycle). The use of a non-azeotropic mixture decreases the loss of availability in a heat recovery boiler when the heat source is a sensible heat source, and in a condenser when the temperature decreases with heat exchange. Most heat input to a plant s working fluid is from variable temperature heat sources. 

Ts diagrams for two reversible thermodynamic power cycles are shown in the following figure. Both cycles operate between a high temperature reservoir at 500 K and a low temperature reservoir at 300 K. The process on the left is the Carnot cycle described in Section 2.9. The process on the right is a Brayton cycle, which is similar to a Carnot cycle, except that the two steps (state 1 to state 2) and (state 3 to state 4) are at constant pressure. Which cycle, if either, has a greater efficiency Explain. 

Plots of the properties of various substances as well as tables and charts are extremely useful in solving engineering thermodynamic problems. Two-dimensional representations of processes on P-V, T-S, or H-S diagrams are especially useful in analyzing cyclical processes. The use of the P-V diagram was illustrated earlier. A typical T-S diagram for a Rankine vapor power cycle is depicted in Figure 2-36. 

Blank, D.A. and Wu, C., Performance potential of a terrestrial solar-radiant Ericsson power cycle from finite-time thermodynamics. International Power and Energy Systems, 15(2), 78-84, 1995. 

The evolution of photosynthetic oxidation of sulfur compounds permitted the development of the full microbial sulfur cycle in sulfureta. In this cycle, some bacteria and archaea reduce oxidized sulfur compounds, pumping them downward in the microbial mat, while other bacteria reoxidize them photosynthetically. The development of this cycle, coupled with the use of stored sulfur as a redox bank balance that could be exploited either way the redox budget swung during tidal and diurnal cycles, would have greatly expanded the thermodynamic power of the biosphere. 

The existence of a finite heat transfer in the isothermal processes is affected with the assumption of a non-endoreversible cycle with ideal gas as working substance. Power output and ecological function have also an issue that shows direct dependence on the temperature of the working substance. Expressions obtained with the changes of variables have the virtue of leading directly to the shape of the efficiency through Z, function. Thus, in classical equilibrium thermodynamics, the Stirling cycle has its efficiency like the Carnot cycle efficiency in finite time thermodynamics, this cycle has an efficiency in their limit cases as the Curzon-Ahlborn cycle efficiency. 

A nuclear power plant produces 1000 MW of electricity with a power cycle thermodynamic efficiency of 30%. The heat rejected is removed by cooling water that enters the condenser at 293 K and is heated to 313 K. The hot water flows to two identical natural-draft cooling towers, where it is recooled to 293 K, and makeup water is added as necessary. The available air is at 298 K with a wet-bulb temperature of 285 K, and it will flow at a rate 1.2 times the minimum. Specialized packing will be used for which Kya is expected to be 1.0 kg/m3-s if the liquid mass velocity is at least 3.4 kg/m2-s and the gas mass velocity is at least 2.75 kg/m2-s. Compute the dimensions of the packed sections of the cooling towers and the makeup water requirement due to evaporation. 

Perform thermodynamic analysis and preliminary design of power cycles and refrigeration units. 

Chapter 22 "Heat Transfer, Thermal Hydraulic, and Safety Analysis" and Chapter 23 "Thermodynamics and Power Cycles" are analytical tools used by engineers to evaluate reactor and power-producing systems. Heat transfer and thermal hydraulics are not only important in the operation of nuclear reactors, they are also critical in the evaluation of how the systems will respond under upset conditions. The chapter on thermodynamics is included to show how the energy generated by the reactor is transferred by the reactor cooling system to the turbine power generating system used to produce electricity. 

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