Closed cycle

A hypothetical moving-bed system and a Hquid-phase composition profile are shown in Figure 7. The adsorbent circulates continuously as a dense bed in a closed cycle and moves up the adsorbent chamber from bottom to top. Liquid streams flow down through the bed countercurrently to the soHd. The feed is assumed to be a binary mixture of A and B, with component A being adsorbed selectively. Feed is introduced to the bed as shown. 

Dehumidification. Dehumidification may be accompHshed in several ways (see Drying). Moderate changes in humidity can be made by exposing the air stream to a surface whose temperature is below the dew point of the air. The air is cooled and releases a portion of its moisture. Closed cycle air conditioning systems normally effect dehumidification also. The cooled air may require reheating to attain the desired dry-bulb temperature if there is insufficient sensible load in the space. 

Gaseous helium is commonly used as the working fluid ia closed-cycle cryogenic refrigerators because of chemical iaertness, nearly ideal behavior at all but the lowest temperatures, high heat capacity per unit mass, low viscosity, and high thermal conductivity. 

The quantity of breathing gas consumed in deep dives is of both economical and logistical concern at depths of 300 m, a reasonably active diver requites ca 1.8 m (64 fT at STP) of breathing gas per minute. In closed-cycle breathing systems, of both the self-contained and umbiHcal types, the helium is recitculated after carbon dioxide is removed and the oxygen replenished (147). 

Eig. 8. Cost of electricity (COE) comparison where represents capital charges, Hoperation and maintenance charges, and D fuel charges for the reference cycles. A, steam, light water reactor (LWR), uranium B, steam, conventional furnace, scmbber coal C, gas turbine combined cycle, semiclean hquid D, gas turbine, semiclean Hquid, and advanced cycles E, steam atmospheric fluidized bed, coal E, gas turbine (water-cooled) combined low heating value (LHV) gas G, open cycle MHD coal H, steam, pressurized fluidized bed, coal I, closed cycle helium gas turbine, atmospheric fluidized bed (AEB), coal J, metal vapor topping cycle, pressurized fluidized bed (PEB), coal K, gas turbine (water-cooled) combined, semiclean Hquid L, gas turbine... 

Japan Tokyo Institute of Tech Yokohama FUJI-1 2-3 closed cycle disk facihty 30% enthalpy extraction achieved... 

An unusual appHcation is the use of KO2 in a closed-cycle diesel system. Oxygen is suppHed and CO2 is removed in a KO2 bed, through which the... 

In addition to the distinction between open- and closed-cycle systems, refrigeration processes are also described as simple cycles, compound cycles. 

Flooded refrigeration systems are a version of the closed-cycle design that may reduce operating problems in some appHcations. In flooded systems, the refrigerant is circulated to heat exchangers or evaporators by a pump. Figure 11 shows the flooded cycle, which can employ any of the simple or compound closed-refrigeration cycles. 

Fig. 1. The energy cycle of a thermal electric generating station having two alternative cooling systems (—) the open-circuit or once-through system and (-------------------------------------) a representative closed-cycle, cooling-tower system. Reproduced by permission (3).

Closed-cycle liquefier systems. In this design the superconductor resides in a bath of liquid helium and boil-off gas is recirculated through a helium liquefier. The installation of such a system is quite complex but these installations have proved good reliability pro-... 

Indirectly fired gas turbines open cycles and closed cycles... 

Specimen Location Closed-cycle service water heat exchanger (turbine cooling)... 

Infrared radiation or closed cycle convection curing furnace... 

The wash water mixed with paint which is a strong waste can be transferred (periodically, if the water curtain system is a closed cycle rather than a continuous running water system) to the effluent treatment plant for further treatment, as shown in Figure A13.12. 

Determine the discharge device for the discharge of a three-phase 6.6 kV, 50 Hz, 1000 kVAr, yconnected capacitor bank, connected in units of 10 x 100 kVAr each, through an automatic p.f. correction relay, having a closing cycle of 10 seconds. Data available from the capacitor manufacturer,... 

The theory is initially presented in the context of small deformations in Section 5.2. A set of internal state variables are introduced as primitive quantities, collectively represented by the symbol k. Qualitative concepts of inelastic deformation are rendered into precise mathematical statements regarding an elastic range bounded by an elastic limit surface, a stress-strain relation, and an evolution equation for the internal state variables. While these qualitative ideas lead in a natural way to the formulation of an elastic limit surface in strain space, an elastic limit surface in stress space arises as a consequence. An assumption that the external work done in small closed cycles of deformation should be nonnegative leads to the existence of an elastic potential and a normality condition. 

Consider a body undergoing a smooth homogeneous admissible motion. In the closed time interval [fj, fj] with < fj, let the motion be such that the material particle velocity v(t) and deformation gradient /"(t), and hence (r), and p(r), have the same values at times tj and tj. Such a finite smooth closed cycle of homogeneous deformation will be denoted by tj). Consider an arbitrary region in the body of volume which has a smooth closed boundary of surface area with outward unit normal vector n. The work W done by the stress s on and by the body force A in during... 

The following work assumption is now made. The external work done on any arbitrarily chosen region of a body undergoing a finite smooth closed cycle of homogeneous deformation %(ti, f ) is nonnegative... 

The velocity and density have the same values at the end of the closed cycle as at the beginning. Thus, the kinetic energy is the same at the beginning and the end, and the first term in (5.36) vanishes. The work assumption (5.34) is expected to hold for any arbitrary region of the body and must therefore hold locally at every material particle, so that (5.36) reduces to... 

Figure 5.4. Elastic finite closed cycle of homogeneous deformation in strain space.

This implies that, at constant k, the line integral of the differential form s de, parametrized by time t, taken over the closed curve h) zero. This is the integrability condition for the existence of a scalar function tj/ e) such that s = d j//de (see, e.g., Courant and John [13], Vol. 2, 1.10). This holds for an elastic closed cycle at any constant values of the internal state variables k. Therefore, in general, there exists a function ij/... 

A third consequence of the work assumption may be deduced from (5.51). Consider a finite smooth closed cycle of homogeneous deformation %(ti, r ) which begins on the elastic limit surface with inelastic loading, so that = t, as shown in Fig. 5.6. The smoothness assumptions imply that -> as r approaches from above so that in (5.51) approaches zero smoothly... 

If the work assumption is made, i.e., if it is assumed that the external work done by surface and body forces on a finite region in the reference configuration of a body undergoing homogeneous closed cycles of deformation is nonnegative, then an inequality may be deduced paralleling (5.37) by arguments essentially the same as those of Section 5.2.4. 

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