Maximum thermal efficiency

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. 

By differentiating Eq. (3.13) with respect to x and equating the differential to zero, it may be shown that the isentropic temperature ratio for maximum thermal efficiency (jCe) is given by the equation... 

In this chapter, cycle calculations are made with assumed but realistic estimates of the probable turbine cooling air requirements which include some changes from the uncooled thermal efficiencies. Indeed it is suggested that for modern gas turbines there may be a limit on the combustion temperature for maximum thermal efficiency [2,3]. 

A hypothetical cycle for achieving reversible work, typically consisting of a sequence of operations (1) isothermal expansion of an ideal gas at a temperature T2 (2) adiabatic expansion from T2 to Ti (3) isothermal compression at temperature Ti and (4) adiabatic compression from Ti to T2. This cycle represents the action of an ideal heat engine, one exhibiting maximum thermal efficiency. Inferences drawn from thermodynamic consideration of Carnot cycles have advanced our understanding about the thermodynamics of chemical systems. See Carnot s Theorem Efficiency Thermodynamics... 

A limit on the efficiency of the electrical energy conduction can be obtained by applying the second law of thermodynamics to the secondary loop. The maximum thermal efficiency, s,, is given in terms of the input and output heats ... 

The heating value of a typical biomass is sufficient to produce steam in excess of that required by the activated process if the system has been designed for maximum thermal efficiency. This can be especially important to developing countries who have large supplies of biomass such as rice hulls or coconut shells and who are currently contemplating the manufacture of activated carbon for export or local water treatment. 

Based upon the analysis developed in this paper, the indirectly heated system can obtain approximately 45% PSU with mole percent H20 equal to 40% as shown in Fig. 10. From Fig. 13 we see that this PSU brings the process into the range of minimum energy requirements and therefore maximum thermal efficiency. On this basis we have recommended further research and development of indirectly heated reactors for the production of activated carbon from municipal solid waste and biomass. 

Not all of the heat produced in a nuclear reactor can be used for woilc, i.e. for turning the turbine blades connected to the rotor of an electric generator. According to the second law of thermodynamics, the maximum thermal efficiency (tf) is... 

Use eqn. (19.33) to estimate the maximum thermal efficiency for the Creys-Malville plant. 

Carnot cycle n. A sequence of operations forming the working cycle of an ideal heat engine of maximum thermal efficiency. It consists of isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression to the initial state. 

The Steam turbine is a tandem compound unit, generally consisting of a double-flow, high-pressure turbine and three double-flow, low-pressure turbines, which exhaust to a high vacuum condenser for maximum thermal efficiency. The condenser may be cooled by sea, lake, or river water, or by use of atmospheric cooling towers. 

Using Eq. (2.8) for the reversible work, one can calculate the maximum thermal efficiency (maximum work for given energy input) of a fuel cell or fuel cell hybrid (fuel cell and heat engine) systan for the H2 oxidation reaction, where AH" is... 

For a given firing temperature there is an optimum pressure ratio for achieving maximum thermal efficiency. 

The theoretical maximum thermal efficiency for the conversion of methane into paraffins is 78% (based on lower heating values). The practically attainable efficiency is of course much lower. 

Determine the maximum thermal efficiency 77 of a reversible heat engine which is supplied with heat at 650 °C and releases heat at 10 °C ... 

A heat engine is supplied with pressurized vapour at 0i = 330 °C and releases heat to a condenser at the temperature O2 = 20 °C. Calculate the theoretical maximum thermal efficiency rj that can be obtained on these conditions, and specify the minimum amount of waste heat Q to be released from the engine if it shall be able to perform useful work oiW = 1000 kJ ... 

Thus, a heat engine is limited in thermal efficiency by the Carnot cycle, and an electrochemical reaction engine is not. The thermal efficiency of a Carnot cycle, which is the measure of the maximum thermal efficiency of a chemical reaction heat engine, is... 

We conclude, thus, that as the cycle approaches reversible operation, its thermal efficiency approaches its maximum value. We will demonstrate next that, of all heat engines operating between two specified tempera-tures, the reversible one has the maximum thermal efficiency. 

The maximum thermal efficiency is established by the Carnot cycle, Eq.3.5.3, which indicates that complete conversion of thermal energy into mechanical is not possible. 

Since Qi=vRTyn V2/Vi), the maximum thermal efficiency of the ideal thermal engine is... 

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