Efficiency Practical cycle

Figure 4.2 and also Chapter 2, for theoretical and practical cycles on the Mollier chart and for volumetric efficiency). 

Determine the thermal efficiency of a practical cycle operating at th conditions if the turbine efficiency and pump efficiency are both 75 percent. 

Chromium. Similar chlorosilane-mediated catalytic processes can be envisaged with many other early transition metals. The development of the first Nozaki-Hiyama-Kishi reactions catalyzed by chromium species [13] illustrates how to avoid the use of an excess of a physiologically suspect and rather expensive salt without compromising the efficiency, practicality and scope of the reaction. The tentative catalytic cycle is depicted in Scheme 3. 

What is thd ttermalpfftelettcy of a practical cycle opetStir at tfrcso conditions turbine McMCyaSd pump efficiency are bbffljDlTSf , i-. ... 

In practice the temperatures Ti and T3 are known from the manufacturer or from measuring instruments installed on the machine. The pressure ratio is also known. The ratio of specific heats is also known or can be taken as 1.4 for air. If the compressor and turbine efficiencies are taken into account then the practical cycle efficiency r]p of the gas turbine can be expressed as ... 

Practical cycle efficiency rjp per nnit, with r]c and r], inclnded. 

The process requires (Qup + Qlp) to satisfy its enthalpy imbalance above the pinch. If there were no losses from the boiler, then fuel W would be converted to shaftwork W at 100 percent efficiency. However, the boiler losses Qloss reduce this to below 100 percent conversion. In practice, in addition to the boiler losses, there also can be significant losses from the steam distribution system. Figure 6.336 shows how the grand composite curve can be used to size steam turbine cycles. ... 

Modem practice is to maintain the white water system as closed as possible, ie, as much water as is compatible with efficient machine operation is recycled. The loss of fibers and inert furnish components, particularly clay, has been gready reduced. Eiber losses, however, stiU occur into the white water, and greater economy of operation may be achieved if these fibers could be recovered. Thus, it is common to design a fiber-recovery system into the white water cycle. The three general types of save-all fiber recovery are based on filtration (qv), dotation (qv), and sedimentation (qv). If these are operated efficiendy, the net fiber loss can be less than 1%. 

Rankine Cycle Thermodynamics. Carnot cycles provide the highest theoretical efficiency possible, but these are entirely gas phase. A drawback to a Carnot cycle is the need for gas compression. Producing efficient, large-volume compressors has been such a problem that combustion turbines and jet engines were not practical until the late 1940s. 

The Intercooled Regenerative Reheat Cycle The Carnot cycle is the optimum cycle between two temperatures, and all cycles try to approach this optimum. Maximum thermal efficiency is achieved by approaching the isothermal compression and expansion of the Carnot cycle or by intercoohng in compression and reheating in the expansion process. The intercooled regenerative reheat cycle approaches this optimum cycle in a practical fashion. This cycle achieves the maximum efficiency and work output of any of the cycles described to this point. With the insertion of an intercooler in the compressor, the pressure ratio for maximum efficiency moves to a much higher ratio, as indicated in Fig. 29-36. 

Maintenance practices are being combined more and more with operational practices to ensure that plants have the highest reliability with maximum efficiency. This has led to the importance of performance condition monitoring as a major tool in the operation and maintenance of a plant. Life cycle costs, rightly so, now drive the entire purchasing cycle and thus the... 

It has been emphasised in the earlier chapters that the thermal efficiency of the gas turbine increases with its maximum nominal temperature, which was denoted as T. Within limits this statement is true for all gas turbine-based cycles and can be sustained, although not indefinitely, as long as the optimum pressure ratio is selected for any value of Ty, further the specific power increases with T. However, in practice higher maximum temperature requires improved combustion technology, particularly if an increase in harmful emissions such as NO is to be avoided. 

It was shown in Ref. [5] that the arguments given above for the closed EGT cycles also hold good for open EGT cycles, but this analysis is not repeated here. Some simple parametric calculations were given to illustrate the increased thermal efficiency of practical open EGT cycles, corresponding to Fig. 6.8a-c. It was assumed that water injection was... 

Experience gives values of for various geometries, but St is also a weak function of Reynolds number and so, in practice, there is relatively little variation in cooling efficiency (0.6 < < 0.8). In the cycle calculations described in Chapter 5, tJcqoi was taken as... 

Restructuring will promote the introduction of other advanced technologies and practices as well. For example, the use of combined-cycle, gas turbine power plants are expected to proliferate under restructuring. These plants are generally more efficient and more environmentally benign than many fossil fuel plants currently in use. 

Reheat involves steam-to-steam heat exchange using steam at boiler discharge conditions. In the reheat cycle, after partially expanding through the turbine, steam returns to the reheater section of the boiler, where more heat is added. After leaving the reheater, the steam completes its expansion in the turbine. The number of reheats that are practical from a cycle efficiency and cost colisidcratioli is two. 

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