Dual-cycle system

System Type. The three basic types of SCF cleaning systems are the direct system, in which supercritical carbon dioxide (SCCO2) is the only cleaning solvent, the single-cycle system, in which the SCCO2 is mixed with a cosolvent and the dual-cycle system in which the parts are exposed separately to cosolvent and supercritical carbon dioxide. 

In the dual-cycle system, all steps take place in a single vessel. The cosolvent is first introduced from a separate module into the cleaning vessel at a selected temperature and atmospheric pressure and circulated around the work to dissolve the contaminant. Then the... 

The dual-cycle system is favored over the single cycle system if the cleaning process requires the use of cosolvent. Although the cosolvent reclaim system adds to initial capital costs, it yields a net gain by lowering material costs and improving consistency and operating efficiency. 

This energy would be added to the electrical energy supplied directly by the fuel cell, so the total electrical energy available from the dual cycle system would be given by the equation... 

In a similar way, electrochemistry may provide an atomic level control over the deposit, using electric potential (rather than temperature) to restrict deposition of elements. A surface electrochemical reaction limited in this manner is merely underpotential deposition (UPD see Sect. 4.3 for a detailed discussion). In ECALE, thin films of chemical compounds are formed, an atomic layer at a time, by using UPD, in a cycle thus, the formation of a binary compound involves the oxidative UPD of one element and the reductive UPD of another. The potential for the former should be negative of that used for the latter in order for the deposit to remain stable while the other component elements are being deposited. Practically, this sequential deposition is implemented by using a dual bath system or a flow cell, so as to alternately expose an electrode surface to different electrolytes. When conditions are well defined, the electrolytic layers are prone to grow two dimensionally rather than three dimensionally. ECALE requires the definition of precise experimental conditions, such as potentials, reactants, concentration, pH, charge-time, which are strictly dependent on the particular compound one wants to form, and the substrate as well. The problems with this technique are that the electrode is required to be rinsed after each UPD deposition, which may result in loss of potential control, deposit reproducibility problems, and waste of time and solution. Automated deposition systems have been developed as an attempt to overcome these problems. 

The operation of the reciprocating internal combustion engines represents a compromise between the Otto and the Diesel cycles, and can be described as a dual combustion cycle. Heat transfer to the system may be considered to occur first at constant volume and then at constant pressure. Such a cycle is called a dual cycle. 

Heat engines that use gases as the working fluid in a closed-system model were discussed in this chapter. The Otto, Diesel, Miller, and dual cycles... 

Wu, C. and Blank, D.A., The effect of combustion on a power optimized endo-reversible Dual cycle. International Journal of Power and Energy Systems, 14(3), 98-103, 1994. 

A dual catalyst system for ARDS units processing heavy stock, i.e. combination of HDM and HDS catalysts gives a more stable and longer catalyst cycle length, more suited to refiner s over-all operational plan. 

Softeners can be a microbial concern. A dark and moist column interior can provide a growth environment. The regeneration cycle which uses concentrated brine solution and a backwash cycle aids in reducing the bioburden. Softeners should be regenerated based on a time clock set for twice weekly regenerations and on a volumetric flow of water, whichever is shorter. Since the regeneration cycle removes the softener bed from operation, a dual bed system is often specified. 

Pig. 2. A dual-cycle homogeneous catalytic system with two common intermediates and one common elementary step. 

Thermal cycle experiments are t5tpicaUy performed in single-chamber ovens. Dual-chamber systems are sometimes employed, but single-chamber equipment tends to dominate the test space. The main drawback of a dual-chamber oven is the lack of control over the thermal loading profile when transferring from one chamber (or thermal zone) to the other. Regardless of whether a single or dual chamber is used, temperature is cycled from a maximum to a minimum (T in) value. Temperature is ramped from one temperature extreme to another at a controlled rate, referred to as the ramp rate. Temperature is also held at the maximum and minimum values for a predetermined time known as the dwell time. Table 59.1 lists typical... 

It has been demonstrated that a loop whose gain varies inversely with amplitude is prone to limit-cycle. Any controller with similar characteristics can promote limit cycling in an otherwise linear loop. On-off controllers are in this categoiy. So any nonlinear device that is purpose inserted into a loop for the sake of engendering stability must have the opposite characteristic gain increasing with amplitude. The only stabilizing nonlinear devices discussed up to this point have this property -it was manifested as a dead zone in the three-state controller and as the linear mode in the dual mode system. 

Another modification of the basic Claude cycle is the dual-pressure Claude cycle, similar in principle to the Linde dual-pressure system presented in Fig. 4.8. In this dual-pressure cycle, shown in Fig. 4.17, only the gas that is sent through the expansion valve is compressed from the low pressure to the high pressure this reduces the w ork requirement per unit mass of gas liquefied. To illustrate the advantage of the Claude dual-pressure cycle over the Linde dual-pressure cycle, Barron has shown that, in the liquefaction of air, the liquid yield can be doubled while the work per unit mass liquefied can... 

It is believed that monofunctional imidazolidinones are optimal for iminium catalysis but without the necessary structural features to participate in bifunctional enamine catalysis (e.g., activation of electrophiles via electrostatic interaction). Conversely, proline has proved to be an enamine catalyst for which bifunctional activation is a standard mode of operation aCTOss a variety of transformation types, yet it is generally ineffective as an iminium catalyst with enals or enones. Therefore, a combination of imidazoUdinone and proline may provide a dual-catalyst system that could fully satisfy the chemoselectivify requirements for cycle-specific catalysis [136]. 

---