Performance of evaporators

Carey VP (1992) Liquid-vapour phase-change phenomena. Hemisphere, Washington, DC Collier SP (1981) Convective boiling and condensation. McGraw-Hill, New York Ha JM, Peterson GP (1998) Capillary performance of evaporation flow in micro grooves an analytical approach for very small tilt angles. ASME J Heat Transfer 120 452 57 Hetsroni G, Yarin LP, Pogrebnyak E (2004) Onset of flow instability in a heated capillary tube. Int J Multiphase Flow 30 1424-1449... 

Ha JM, Peterson GP (1998) Capfllary performance of evaporating flow in micro-grooves. An approximate analytical approach for very small tilt angles. Trans ASME J Heat Transfer 120 452-457... 

The performance of evaporation lagoons is necessarily site-specific therefore, the following data are presented on the basis of net annuat evaporation rate that may exist in a certain area ... 

The Z-spray inlet causes ions and neutrals to follow different paths after they have been formed from the electrically charged spray produced from a narrow inlet tube. The ions can be drawn into a mass analyzer after most of the solvent has evaporated away. The inlet derives its name from the Z-shaped trajectory taken by the ions, which ensures that there is little buildup of products on the narrow skimmer entrance into the mass spectrometer analyzer region. Consequently, in contrast to a conventional electrospray source, the skimmer does not need to be cleaned frequently and the sensitivity and performance of the instrument remain constant for long periods of time. 

Condenser performance should be expressed as evaporating effect to enable matching with compressor and evaporator performance. Condenser evaporating effect is the refrigeration capacity of an evaporator served by a particular condenser. It is the function of the cycle, evaporating temperature, and the compressor. The evaporating effect could be calculated from the heat-rejection ratio qc / e -... 

The performance of the condensing-unit (compressor and condenser) subsystem could be developed as shown in Fig. 11-96 by superimposing two graphs, one for compressor performance and the other for condenser evaporating effecl . 

FIG. 11-98 Performance of complete refrigeration system (1), when there is reduction in heat load (2), and when for the same ambient (or inlet in evaporator) evaporation temperature is maintained constant hy reducing capacity of compressor/condenser part (3). 

Performance data on some typical tray and compartment diyers are tabulated in Table 12-10. These indicate that an overall rate of evaporation of 0.0025 to 0.025 kg water/(s m") of tray area may be expected from tray and tray-truck diyers. The thermal efficiency of this type of diyer will vary from 20 to 50 percent, depending on the diying temperature used and the humidity of the exhaust air. In diying to very low moisture contents under temperature restrictions, the thermal efficiency may be in the order of 10 percent. The major operating cost for a tray diyer is the labor involved in loading and unloading the trays. About two labor-hours are required to load and unload a standard two-truck tray diyer. In addition, about one-third to one-fifth of a... 

The other mechanism appears in scrubbers. When water vapor diffuses from a gas stream to a cold surface and condenses, there is a net hydrodynamic flow of the noncondensable gas directed toward the surface. This flow, termed the Stefan flow, carries aerosol particles to the condensing surface (Goldsmith and May, in Davies, Aero.sol Science, Academic, New York, 1966) and can substantially improve the performance of a scrubber. However, there is a corresponding Stefan flow directed away from a surface at which water is evaporating, and this will tend to repel aerosol particles from the surface. 

As initially discussed in Section 3, carbon canisters are used in the automotive emission control system to temporarily store hydrocarbon vapors. The vapors are later purged into the air charge stream of the air induction system, thus regenerating the carbon canister. Carbon canister design is dependent on the characteristics of the vapors sent to the canister and the amount of purge air available. In the following section, factors that affect the performance of the evaporative emission control system will be discussed. 

The reduced adsorption capacity at ORVR vapor generation rates requires increased efficiency in the canister design, in order to limit the effect on cost and performance of the evaporative control system. 

Frutschi and Plancherel [11 not only described the basic EGT cycle, but also a modified version with an intercooler added. Macchi et al. [9] called this intercooled EGT the RWI plant and the simplest version is shown in the top part of Fig. 6.14. Macchi et al. also considered more complex versions (some with evaporative intercooling and aftercooling), the performance of which are discussed in Section 6.6. 

Superheated steam may be needed where steam distribution pipework in a plant is over extended distances, resulting in a loss of heat and increase in wetness of the steam. Another case may be where a process requires a temperature above the working pressure of the plant. The third case is where steam is used for turbines. Here it improves the performance of the turbine, where for every 6°C increase in steam temperature it can produce a saving of about 1 per cent reduction in steam consumption. Superheaters may also be supplied as independently fired units. These may be used when either the amount of superheated steam required is much less than the boiler evaporation or is only needed on an intermittent basis. 

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