THERMAL ENGINEERING IN POWER SYSTEMS

Volume 22 in the WIT Press Developments in Heat Transfer series looks at the research and development in thermal engineering for power systems that are of significant importance to many scientists who work in power-related industries and laboratories. To be competitive in today's market, the editors say, power systems need to reduce operating costs, increase capacity, and deal with many other tough issues. Among the topics the book covers are: relevance of heat transfer and heat exchangers for development of sustainable energy systems; advanced technologies for clean and efficient energy conversion in power systems; virtual engineering and the design of power systems; and innovative gas turbine cooling techniques.

Heat Exchangers

Process Heat Exchangers

TEi has incorporated the knowledge and experience from recent acquisitions of EFCO, which included previous Westinghouse and Marley feedwater heater products, to provide our customers with a wide array of quality process heat exchangers. We supply high and low pressure feedwater heaters, oil coolers, component coolers and service water coolers to the petrochemical, petroleum refining, process chemical, electric generation, synthetic fuel processing, natural gas processing, solar and gasification markets.

The combination of TEi’s experience, shop capabilities (Joplin, MO and Sapulpa, OK), financial strength, and field service support, offers the process industry a reliable supplier that is capable of providing exchangers which can meet the most demanding operating service conditions. In order to more effectively service the process industry, TEi has opened a Houston, TX Process Heat Exchanger Division sales office, staffed with experienced employees.

TEi is a member of HTRI and HEI and builds to TEMA standards. TEi is registered with ASME as an ASME Sec VIII Div.1 and 2 Code manufacturer. TEi also holds certifications for ASME “U”, “S”, and “P” Code Stamps, NBIC “R” Stamp, China Safety License and ISO 9001 Certification

Thermal power plant or Steam power plant

A generating station which converts heat energy of coal combustion in to electrical energy is known as Thermal power plant or Steam power plant. Some of its advantages and disadvantages are given below.

Advantages

The fuel used is quite cheap.
Less initial cost as compared to other generating plants.
It can beinstalled at any place iirespective of the existence of coal. The coal can be transported to the site of the plant by rail or road.
It require less space as compared to Hydro power plants.
Cost of generation is less than that of diesel power plants.
Disadvantages

It pollutes the atmosphere due to production of large amount of smoke and fumes.
It is costlier in running cost as compared to Hydro electric plants.

OFFICE SAFETY

Staff who work exclusively in offices should be aware that they have the RIGHT TO KNOW any laboratory hazards in the surrounding area and they should feel free to discuss any questions or concerns with any member of the Department Safety Committee.
It is the responsibility of each employee to perform his or her job in a safe manner. Safety is as important in the office as it is in the laboratory.

Offices should be inspected by the occupants for earthquake hazards. Tall bookshelves and cabinets (including lateral file cabinets) must be anchored to the wall or made secure by other approved means (contact John Souza, 2-3314). There should be no overhead storage that could create a falling hazard.
Extension cords are not to be used. Approved multi-plug strips may be used as long as they have an internal breaker and are not run in series with other cords (daisy-chained). All cords should be inspected for wear, frayed cords are to be replaced.
Use of space heaters has been specifically prohibited by the State Fire Marshal. Problems with room heat should be reported to Physical Plant, 2-1032.
Furniture arrangement in offices should permit a quick exit in an emergency. Quantities of paper or other combustibles must be kept at a minimum.
EH&S (2-3073) has many brochures available regarding display terminals (VDT) and other office machinery.

Thermodynamics process of a perfect gas

Adiabatic process

Polytropic process

Constant Volume Process

Throttling Process

Free Expansion ( Unresisted Expansion ) Process

               The free expansion process is an irreversible non-flow process. A free expansion process occurs when a fluid is allowed to expand suddenly into a vacuum chamber through an orifice of large dimensions.

               Consider two chamber A and B separated by a partition. Since there is no expansion of the boundary of the system, because it is rigid, therefore no work is done. Thus, for a free expansion,
                                    Q1-2 = 0; W1-2 = 0 and dU = 0
                The following points may be noted regarding the free expansion of a gas:
1. Since the system is perfectly insulated so that no heat transfer takes place therefore the expansion of gas may be called as an adiabatic expansion.
2. Since the free expansion of the gas from the equilibrium state 1 to the equilibrium state 2 takes place therefore the intermediate state will not be in equilibrium states.
etc...

Rate of Heat Transfer

                    Heat transfer during a polytropic process
                                        Q1-2 = (segma) - n / (segma) - 1 * W1-2
 where W1-2 is the work done during polytropic process.
                     If dQ is the small quantity of heat transfer during small change of pressure and volume, then
                                                 dQ = (segma) - n / (segma) - 1 * pdv
Rate of heat transfer per unit volume,
                                                dQ / dv = (segma) - n / (segma) - 1 * p

and rate of heat transfer per second,

                                     dQ / dt = dQ / dv * dv / dt = (segma) - n / (segma) -1 * p * dv / dt

where dv / dt is the swept volume of the piston per second.

Constant Tempreture Process (Isothermal Process)

             A process, in which the tempreture of the working substance remains constant during its expansion or compression, is called constant tempreture process or isothermal process. This will happen when the working substance remains in a perfect thermal contact with the surroundings, so th

at the heat "sucked in' or 'squeezed out' is compensated exactly for the work done by the gas or on the gas respectively. It is thus obvious that in an isothermal process:
    1. there is no change in tempreture.
    2. there is no change in internal energy, and
    3. there is no change in enthalpy.
          Now consider m kg of a certain gas being heated at constant tempreture from an intial state 1 to final state 2.
    Let                 p1v1 and T1 = Pressure, volume and tempreture at the intial state 1, and

                          p2v2 and T2 = Pressure, volume and tempreture at the final state 2.

Hyperbolic Process

           A process, in which the gas is heated or expanded in such a way that the product of its pressure and volume (i.e *v ) remains constant, is called a hyperbolic process.

          It may be noted that the hyperbolic process is governed by Boyle,s law i.e p v = constant. If we plot a graph for pressure and volume, during the process as shown in fig we shall get a rectangular hyperbola. Hence, this process is terned as hyperbolic process. It is merely a theoretical case, and has a little importance from the subject point of view. Its practical application is isothermal process, which is discussed below.

General Laws for Expansion and Compression

     The general law of expansion or compression of a perfect gas is pVn = Constant. It gives the relationship between pressure and volume of a given quantity of gas. The value of n depends upon the nature of gas., and condition under which the changes take place. The value of n may be between zero and infinity. But the following values of n are important from the subject point of view.

1. when n = 0. This means pV0 = constant, i.e.p = constant. In other words, for the expansion or constant of a perfect gas at constant pressure, n = 0.

2. when n = 1 ; then pv = constant, i.e the expansion or compression is isothermal or hyperbolic.
3. when n lies between 1 and n, the expension or compression is polytropic, i.e. pVn = Constant.
4. when n = & the expension or compression is adiabatic

5. when n = infinity the expansion or compression is at constant volume, i.e. v - Constant.