Rankine vapor power cycle

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. 

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. 

The Carnot cycle is not a practical model for vapor power cycles because of cavitation and corrosion problems. The modified Carnot model for vapor power cycles is the basic Rankine cycle, which consists of two isobaric and two isentropic processes. The basic elements of the basic Rankine cycle are pump, boiler, turbine, and condenser. The Rankine cycle is the most popular heat engine to produce commercial power. The thermal cycle efficiency of the basic Rankine cycle can be improved by adding a superheater, regenerating, and reheater, among other means. 

The hot water from the bottom of the pond is pumped through a boiler, where it boils a working fluid in a Rankine power cycle, as shown in Fig. 2.31. The cooler water from the surface of the pond is used to cool the turbine exhaust vapor in the condenser. This is the same concept that is employed in the OTEC system, except that in the OTEC system the surface waters are warmer than that of the deep ocean water. 

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... 

The Brayton and Rankine power cycles, which are most commonly used in power generation, are identical except that the Rankine cycle employs a vapor with a phase change and the Brayton cycle operates on a single phase gas. In both cases, there is a pressure increase process (using a pump or compressor), a heat addition process, expansion in a turbine, and a heat removal process. Nuclear power generation currently uses the Rankine cycle almost... 

Say we wish to convert a fossil-fuel, nuclear, or solar energy source into net electrical power. To accompftsh this task, we can use a Rankine cycle. The Rankine cycle is an idealized vapor power system that contains the major components foimd in more detailed, practical steam power plants. While hydroelectric and wind are possible alternative sources, the steam power plant is presently the dominant producer of electrical power. 

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... 

Determine the efficiency and power output of a basic Rankine cycle using steam as the working fluid in which the condenser pressure is 80 kPa. The boiler pressure is 3 MPa. The steam leaves the boiler as saturated vapor. The mass rate of steam flow is Ikg/sec. Show the cycle on a T-s diagram. Plot the sensitivity diagram of cycle efficiency versus boiler pressure. 

Water is the working fluid in an ideal Rankine cycle. The condenser pressure is 8kPa and saturated vapor enters the turbine at (1) 15 MPa, (2) 10 MPa, (3) 7 MPa, and (4) 4 MPa. The net power output of the cycle is 100 MW. Determine for each case the mass flow rate of... 

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. 

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 ... 

The thermal efficiency of this cycle is that of a Carnot engine, given by (5.8). As a reversible cycle, it could serve as a standard of comparison for actui steam power plants. However, severe practical difficulties attend the operatk of equipment intended to carry out steps 2 3 and 4 1. Turbines that take i saturated steam produce an exhaust with high liquid content, which causes sevel erosion problems, t Even more difficult is the design of a pump that takes in mixture of liquid and vapor (point 4) and discharges a saturated liquid (poll 1). For these reasons, an alternative model cycle is taken as the standard, at lei for fossil-fuel-buming power plants. It is called the Rankine cycle, and diSei from the cycle of Fig. 8.2 in two major respects. First, the heating step 1 2 ... 

This represents a machine efficiency roughly equal to that of central station electric power production and distribution. Even higher efficiency can be obtained with a new experimental compound engine system. Known as an organic Rankine bottoming cycle, this powerplant derives about 38 hp (at full load) from the waste heat of the truck engine. Organic fluid is vaporized in an... 

Rankine Cycle - The thermodynamic cycle that Is an Ideal standard for comparing performance of heat-engines, steam power plants, steam turbines, and heat pump systems that use a condensable vapor as the working fluid efficiency is measured as work done divided by sensible heat supplied. 

A steam power plant uses natural gas to produce 0.12 MW power. A furnace completely bums the natural gas to CO2 and water vapor with about 25% of excess air. The flue gas leaves the furnace at 465 K. The combustion heat supplied to a boiler produces steam at 9000 kPa and 798.15 K, which is sent to a turbine. The turbine efficiency is 0.7. The discharged steam from the turbine is at 20 kPa, and sent to a condenser. The condensed water is pumped to the boiler. The pump efficiency is 0.70. Assume that the natural gas is pure methane gas, and the surroundings are at 298.15 K. Determine (a) The thermal efficiency of a Rankine cycle (b) The thermal efficiency of an actual cycle (c) The work loss of each unit of boiler, turbine, condenser, and pump. 

Such a thermal engine cycle is shown in Figure l3-9. Evaporation, expansion, condensation, and pressure rise are repeated in a simple Rankine cycle. In the simplest form, "waste heat" is applied to a boiler which provides saturated or superheated vapor to the expander, and the fluid passes on to a condenser, which provides liquid to the pump. The pump raises the pressure and resupplies fluid to the boiler, thereby completing the cycle. The working fluid condenser heat is rejected to a cooling fluid in the condenser, either cooling water or air. The expander shaft work is ultimately used as shaft power to drive compressors or pumps, or to drive a generator to produce electrical power. 

Figure 11.3 is a schematic of a steam power plant and Fig. 11.4 is the P-Fq diagram for the widely used Rankin engine cycle. The pump takes water exiting the condenser at temperature (Zj) and pressure (Pj) and raises the pressure to P at, essentially, a constant temperature [from point (1) to point (2) in Fig. 11.4]. The water is vaporized and, possibly, superheated to temperature (Z2) at, essentially, a constant pressure (P2) [from point (2) to point (3) in Fig. 11.4] in the boiler and superheater...

Refrigeration systems are important in industrial and home use when temperatures less than the ambient environment are required. Of the several types of refrigeration systems, the most widely used is the vapor-compression refrigeration cycle. It is essentially a Rankine cycle operated in reverse, where heat is absorbed from a cold reservoir and rejected to a hot reservoir. Due to the constraints of the second law, this process can be accomplished only with a concomitant consumption of power. 

You are considering building a solar power plant which uses CCI2F2 as its working fluid. It enters the turbine as a saturated vapor at 1.7 MPa and leaves at 0.7 MPa. Based on the ideal Rankine cycle, determine the efficiency. Property data for CCI2F2 may be found at http //webbook.nist. gov/chemistry/fluid/. 

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