Multi-step cooling

The nomenclature introduced by Hawthorne and Davis [4] is adopted and gas turbine cycles are referred to as follows CHT, CBT, CHTX, CBTX, where C denotes compressor H, air heater B, burner (combustion) T, turbine X, heat exchanger. R and I indicate reversible and irreversible. The subscripts U and C refer to uncooled and cooled turbines in a cycle, and subscripts 1,2, M indicate the number of cooling steps (one, two or multi-step cooling). Thus, for example, [CHT] C2 indicates an irreversible cooled simple cycle with two steps of turbine cooling. The subscript T is also used to indicate that the cooling air has been throttled from the compressor delivery pres.sure. 

The argument developed in Section 4.2.1.2 can be extended for three or more steps of cooling, to give the same efficiency as the uncooled cycle. Indeed the efficiency will be the same for multi-step cooling, with infinitesimal amounts of air abstracted at an infinite number of points along the compressor to cool each infinitesimal turbine stage at the required pressures. 

But another approach to multi-step cooling [8, 9] involves dealing with the turbine expansion in a manner similar to that of analysing a polytropic expansion. Fig. 4.4 shows gas flow (1 + ijj) at (p,T) entering an elementary process made up of a mixing process at constant pressure p, in which the specific temperature drops from temperature T to temperature T, followed by an isentropic expansion in which the pressure changes to (p dp) and the temperature changes from T to (7 - - dT). 

Fig. 4.4. Temperature-entropy diagram for multi-step cooling—reversible cycle 1CHT]r< m (after Ref. [5 ).

Cycle with multi-step cooling [CHTJicm... 

The two step cooling example given above can in theory be extended to multi-step cooling of the turbine. It is more convenient to treat the turbine expansion as a modification of normal polytropic expansion the analysis is essentially an adaptation of that given in Section 4.2.1.3 for the multi-step cooled turbine cycle. 

Fig 3, The sand is used as fluidized medium and steam preheated to 400 to 500 C acts as a fluidizing gas. The fluid bed reactor is externally heated by propane burners. The gas/steam mixture passes through a multi - step cooling / separation process. First, solids such as soot and dust are precipitated in a cyclone. Next, water is condensed in a... 

The cycle calculations for this multi-cooling then proceeded in a similar fashion to those for the single-.step cooling calculations of Section 5.4 (full details are given in Ref. [2]). 

Deodorization is a multi-step process comprising de-aeration, heating, deodoriza-tion-deacidification, and cooling of the oil (Figure 9). 

The ability to scale up the abc deformation approach to form SMC structure in a large-scale Ti-64 billets was demonstrated via prototype production. The billets (150 mm in diameter and 200 mm in length) solution treated at 1010°C for 0.5 hr followed water cooling were subjected to near-isothermal multi-step forging comprising of specific combination of multiple upset/drawing operations [3] at the thermo-mechanical conditions provided formation of submicron-sized microstructure. 

Cosford and coworkers presented a simple microreador setup for enabling multi-step synthesis of bis-substituted 1,2,4-oxadiazoles that required differential and controlled thermal treatments (between 0 and 200 °C) (Scheme 5.24) [34]. A base-assisted reaction between arylnitrile and hydroxylamine hydrochloride at 150°C in the first reactor produced amidoxime, which was quickly cooled to 0 °C before it was mixed with the add chloride. This mixture was then warmed and maintained at room temperature for 2 min in the connected tube before it entered a superheated chip-microreador where the high temperature (200 °C) and pressure (7.5-9.0 bar) accelerated the reaction leading to 40-63% of differently functionalized oxadiazoles within 30 min of total process time. Relativdy inferior yields were obtained from over three-day-long reaction in a sealed tube for the same products. 

A mixture of dry Pb-tetraacetate and Ga-carbonate refluxed briefly in abs. benzene, cooled, 3,17-dioxo-19-hydroxy-Zl -androslene added, and refluxed 14 hrs. 3,17-dioxo-10j -aceloxy-zj -estrene. Y 77%. based on startg. m. consumed.—The reaction is critically influenced by the choice of the solvent and independent of steric factors. It makes available by straightforward synthesis compounds which otherwise can be obtained only by multi-step procedures. F. e. s. M. Amorosa et al., Helv. 45, 2674 (1962) without CaCOg cf. F. Alvarez, Steroids 3, 13 (1964). 

This chapter deals mainly with (multi)hyphenated techniques comprising wet sample preparation steps (e.g. SFE, SPE) and/or separation techniques (GC, SFC, HPLC, SEC, TLC, CE). Other hyphenated techniques involve thermal-spectroscopic and gas or heat extraction methods (TG, TD, HS, Py, LD, etc.). Also, spectroscopic couplings (e.g. LIBS-LIF) are of interest. Hyphenation of UV spectroscopy and mass spectrometry forms the family of laser mass-spectrometric (LAMS) methods, such as REMPI-ToFMS and MALDI-ToFMS. In REMPI-ToFMS the connecting element between UV spectroscopy and mass spectrometry is laser-induced REMPI ionisation. An intermediate state of the molecule of interest is selectively excited by absorption of a laser photon (the wavelength of a tuneable laser is set in resonance with the transition). The excited molecules are subsequently ionised by absorption of an additional laser photon. Therefore the ionisation selectivity is introduced by the resonance absorption of the first photon, i.e. by UV spectroscopy. However, conventional UV spectra of polyatomic molecules exhibit relatively broad and continuous spectral features, allowing only a medium selectivity. Supersonic jet cooling of the sample molecules (to 5-50 K) reduces the line width of their... 

Overall, EGR and combustion/injection systems constitute the key factors to comply with the EuroIV standards (applied in January, 2005). The EuroIV step exhibits EuroIII NO and soot particles limits divided by 2. Besides, vehicle s weight is always increasing due to the introduction of new safety systems and equipment. Therefore, pollutants emissions increase and a supplementary effort to reach the normative threshold is to be made. To comply with this target, some evolutions have been introduced, as for example multi-injection or water-cooling of the EGR system. The NO,/particle compromise adjustment remains possible for most of the applications without any after-treatment system like the Diesel particle filter (DPF). 

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