Cycle absorption

In some appHcations, large quantities of waste or low cost heat are generated. The absorption cycle can be directly powered from such heat. It employs two intermediate heat sinks. Its theoretical coefficient of performance is described by... 

Do not regenerate molecular sieves by steaming water typically very strongly adsorbed and may not be easily displaced by adsorbent in next absorption cycle. 

Coefficient of performance of the absorption cycle is defined on the same principle as for the mechanical refrigeration ... 

The ammonia-water absorption system was extensively used until the fifties when the LiBr-water combination became popular. Figure 11-103 shows a simplified ammonia-water absorption cycle. The refrigerant is ammonia, and the absorbent is dilute aqueous solution of ammonia. Ammonia-water systems differ from water-lithium bromide equipment to accommodate major differences Water (here absorbent) is also volatile, so the regeneration of weak water solution to strong water solution is a fractional distillation. Different refrigerant (ammonia) causes different, much higher pressures about 1100-2100 kPa absolute in condenser. 

The term refrigeration refers to the gas coming into contact with evaporator coils on a dx vapor-compression cycle, coils on an absorption cycle, vortex... 

A description of the absorption cycle of Figure 11-19 is used by permission from Carrier Corporation, Bui. 521-606 ... 

Absorption cycle, (a) Basic circuit, (b) Circuit with heat... 

The absorption system can be used to advantage where there is a cheap source of low-grade heat or where there are severe limits to the electrical power available. A modified system of the ammonia-water absorption cycle has been developed for small domestic refrigerators. 

The solid sorbent material must also be heated and cooled for regeneration and absorption cycles. Because the solid C02 sorbents operate at higher temperatures than the liquid absorption systems, they provide opportunities for simultaneous WGS reaction with C02 removal improving the CO conversion in sorbent-enhanced reaction process (SERP). A number of studies have been reported on the SERP concept and are currently underway as discussed in later sections. 

In our laboratory, absorption experiments were carried out on an unmiUed but activated ABCR MgHj powder. In the preliminary stage, the powder was heated up to 350°C in a volumetric Sieverts-type apparatus (Sect. 1.4.2) under a preventing pressure of 3.5 MPa (so as not to allow desorption), held for about 30-45 min to stabilize temperatnre, and then snbjected to the following desorption/absorption cycles ... 

Thermal aetivation by desorption/absorption cycling at elevated temperatures of premilled MgH reverts some of the microstructural changes induced by milling. ABCR powders initially milled, as shown in Fig. 2.13, were subjeeted to the following eyeling heating to 325°C for 15 min under 3.4 MPa to prevent desorp-... 

A cycling behavior of the MgH mixture with n-Ni was also studied. The cycling process consisted of live desorption/absorption cycles at 300°C. Desorption was carried out at the atmospheric pressure of hydrogen, and absorption was realized under 4.0 MPa pressure of hydrogen for 15 min. XRD after cycling showed formation of a... 

The absorption cycle efficiency can be improved by placing a heat exchanger between the generator and the absorber as a regenerator, as shown in Fig. 6.25. 

The catalyst, used in the form of a ceramic honeycomb monolith, is constituted, as in mobile applications, by a noble metal and an absorber element, such as potassium, deposited on a Y-AI2O3 wash-coat layer. In the oxidation and absorption cycle, the SCON Ox catalyst works by simultaneously oxidizing CO and UHCs to CO2 and H2O, while NOj, are captured on the adsorber compound. Catalyst regeneration is accomplished by passing a controlled mixture of regeneration gases across the surface of the catalyst in the absence of oxygen. 

Figure 5.12 Interfering pathways from Et) to the continuum associated with the scenario in Figure 5.11. The frequency and phase of the lasers are co, and (a) Bichromatic control, (b) One-photon absorption, (c) Three-photon process in which initially unpopulated state Ej) is coupled to the continuum at energy E and interferes with one-photon absorption from state ] ,). (d) Same as in (c) but for a five-photon process. Notice that in processes depicted in (c) and (d) the phase

The output current behavior observed by analyzing many absorption cycles shows that in the same day both the initial and the saturation levels are restored within an accuracy of less than 3% (short-time stability). A comparison of measurements made on different days separated by a week (long-time stability) shows that the accuracy decreases to about 8-12% when 0.5% H2 is used and to about 5 -9% for 100 ppm of H2. 

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