System_Integration

System integration is the act of combining multiple subsystems in order to make up one complete system where each subsystem complements the other. The common goal is for the system to be able to effectively perform its job (http://www.stsc.hill.af.mil/resources/tech_docs). Vapor power plants operate off of vapor power systems. Vapor power systems are one example of system integration. The working fluid in these systems is typically water. The water alternatively vaporizes and condenses. Vapor power systems can include multiple parts. They may contain a turbine, condenser, pump, or boiler. Also, other components may be added to the system if the engineer believes it will make the system more efficient and improve system performance (http://www.u.arizona.edu/~jmcgrath/ln.ch8.notes1.pdf). Vapor power systems can contain a turbine. A turbine is simply an engine that converts energy from a fluid into useful work. The simplest turbines contain one rotating rotor with a drum attached. The drum contains blades pick up certain amounts of the fluid that will be used for energy conversion. The blades also add rotational kinetic energy to the fluid. This energy is then converted to static pressure through the process of diffusion, thus producing work. The exact amount of work produced can be estimated by using the P-V diagram. This in turn provides a measure of power of produced. The diagram will show the pressure of steam versus the volume of steam in the system. The area under the curve will be equivalent to work (http://library.thinkquest.org/C006011/english/sites/dampfturbine.php3'v=2). Many vapor systems also contain compressors. Compressors work much like turbines; however, it operates in reverse. One compressor in particular, the axial compressor, continually produces a flow of compresses gas. These compressors allow large capacities of mass flow, which increase efficiency. The downside of the axial compressor is the fact that it is very complex, thus expensive. Another type of turbine is the contra-rotating turbine. Similar to a compressor, parts rotate in the opposite direction around the axis. This turbine is generally very efficient because the reverse rotation strongly reduces torque. The shroudless turbine can also be used to increase efficiency in vapor water systems. This turbine can be very efficient because in most parts, the rotor covering is eliminated. This reduces the centrifugal load on the blade as well as the temperature the blade will reach while working. Vapor power systems also contain condensers. A condenser is simply a mechanism used to convert a gaseous substance into its liquid state. This is done by cooling the gas. Many use cool water while others use air when water is in short supply. In general, condensers are heat exchangers. They take heat from one area and release it into another area. A refrigerator contains a condenser. If one ever feels behind the refrigerator, the air will be warm. The refrigerator is taking heat from the inside of the unit and releasing it into the surroundings. In vapor power systems, the steam is the substance being condensed. This is referred to as the Rankine cycle. One type of condenser is the surface condenser. This condenser contains a shell and a tube. It is installed outlets in many power stations (http://www.engineersedge.com/heat_exchanger/large). Pumps are also crucial subsystems to the water vapor system. Pumps are devices used to move fluids such as liquid or even gas. There are several different types of pumps. Generally, only three types of pumps are found in vapor power systems. They are radial, axial, and mixed flow pumps. Radial flow pumps or centrifugal pumps allow a fluid to enter along and axial plane. The same fluid is pushed through by the impeller and exits the pump at right angles to the shaft. Radial pumps operate at a higher pressure and lower flow rate than the other two pumps. Axial flow pumps differ from radial flow in that the fluid enters and exits along the same direction parallel to the rotating shaft. The fluid is not accelerated through, but it is lifted by the impeller. The axial pump’s pressure is much lower than radial, and the flow rate is much higher. The last pump, mixed flow pumps, is the same as its name implies. The fluid is both accelerated and lifted, thus providing higher pressures than axial flow pumps while delivering higher discharges than radial flow pumps (http://www.swe.org/iac/lp/pumps_04.html). Vapor power systems can also contain boilers. A boiler is a closed vessel in which water or other fluid is heated so that it can be used in various processes. Vapor boilers are usually made of copper or brass. The use of stainless steel is prohibited by the ASME boiler code. The first type of boiler is the “pot boiler”. In this boiler, a fire heats a partially-filled water container from underneath. There is also a fire-tube boiler. This boiler allows water to enter to a certain volume. It is never filled with water because the steam needs to have room in the boiler also. This is the boiler used in most vapor power systems. This boiler uses a furnace to heat the water. However, the boiler must be surrounded by water. The water allows the outside surface of the boiler to remain at a temperature just below boiling point. This prevents the boiler from overheating, which will cause many problems. There is also a water-tube boiler where the water tubes are arranged inside a furnace. The tubes connect large drums. Those drums contain water and steam (http://www.energyquest.ca.gov/story/chapter06.html). Superheater can also be used in vapor power systems. Superheaters are devices that convert wet steam into the dry steam that is used to generate power. These devices can increase the efficiency of the system. They reduce the amount of water that is needed to create power. They also heat the steam generated by the boiler again thus increasing its thermal energy. This will prevent the steam from condensing during the process of creating energy. The three types of superheaters are radiant, convection, and separately fired. A radiant superheater sits in the combustion chamber while a convection superheater is located in the path of the gases. The last type of superheater, separately fired, is completely detached from the boiler (http://www.slideshare.net/foxycrow/layout-of-thermal-power-plant). System integration is something that we should all be proud of. It simplifies many processes, such as vapor power systems. Simplification is very important in this process because there are more important things to be concerned with such as temperature and entropy changes during the process; however, this job can also be simplified by using a T-s diagram. Theses diagrams allow users to see the heat transfer during a process. For reversible or ideal processes, the area under the curve indicated the amount of heat transferred. If the devices and processes used are very efficient, more heat will be transferred during the system (http://www.grc.nasa.gov/WWW/K-12/airplane/pvtsplot.html). Reference Page • http://www.stsc.hill.af.mil/resources/tech_docs/gsam4/chap14.pdf • http://www.u.arizona.edu/~jmcgrath/ln.ch8.notes1.pdf • http://library.thinkquest.org/C006011/english/sites/dampfturbine.php3'v=2 • http://www.swe.org/iac/lp/pumps_04.html • http://www.energyquest.ca.gov/story/chapter06.html • http://www.slideshare.net/foxycrow/layout-of-thermal-power-plant • http://www.grc.nasa.gov/WWW/K-12/airplane/pvtsplot.html