Circulating power

Although these units find initial application in areas of limited water, they have not been limited to this situation. In many instances they are more economical than cooling tower systems and have been successfully applied in combination with cooling towers (see Figure 10-184). Economic comparisons should include such items as tower costs, basin, make-up facilities, water treatment, pumps for circulation, power supply, blow down, piping, etc. For small installations of air-cooled units, they should be compared... 

Circulating power, 14 669, 670 Circulation control, 9 23-24 Circulation effects, in liquid-liquid extraction, 10 763... 

The pumping power for a water-based versus helium-based loop was calculated at the full power condition. The fluid properties in the respective loops were used to calculate the friction loss power per unit megawatt of thermal power transported for the water-based loop as a fraction of the same in the helium-based loop. The result derived in Vilim (2009) shows that the power in the water loop is insignificant to the power in the helium loop. In the helium loop the circulating power needed is about 7 MWe or 14 MWt out of a reactor thermal capacity of 600 MWt. Thus an advantage of a water-based loop is that the pumping power to overcome frictional losses is significantly less and results in an efficiency increase. 

Absorption refrigeration utilizes low grade heat and may be employed to chill compressor suction and hence reduce compressor horsepower. Similarly it may be used to chill the loop circulating gas and increase the conversion per pass. This would lead to a reduction in the circulator power of up to 10%. 

AQ = Carnot cycle power, kW ACf = Circulator power, kW AG = Fuel cell power, kW y = Specific heat ratio = C /C, ... 

In the MCFC there must be carbon dioxide recirculation from anode to cathode, as per Figure 5.3. The recirculation of anode gas as a means of getting at the carbon dioxide represents an irreversibility, since additional circulator power must be committed, and additional pressure drop losses encountered. 

As the electrical work of the electrochemical reaction in Figure A.2 declines with increasing temperature, there is a corresponding increase of Carnot work and a change of the substantial circulator power. At standard conditions the isentropic circulators are redundant, as is the Carnot cycle. 

A.2.15 Circulator Power and Chemical Exergy Calculated at Standard Conditions... 

The three isothermal circulators in Figure A.l are clearly all expanders, producing power. The isentropic circulators and the Carnot cycle are redundant, having zero temperature difference. The circulator power added to the standard conditions AG of Table A.2 will give the chemical exergy of the two fuels, CO and H2. 

Table A.l Isothermal circulator power, CO fuel, standard conditions...

Table A.3 Isothermal Circulator Power - Hydrogen Fuel- PqTq...

In order to tackle the pressurised, high-temperature, equilibrium systems, the AS and the AG must be taken from the JANAF thermochemical tables (Chase etal., 1986 1998). The AS determines the reversible heat input to the Carnot cycle. Pressure affects the equilibrium constant for hydrogen, but not for carbon monoxide. Pressure moves the equilibrium concentrations in the direction of the product, affecting circulator power. 

The circulator power now has isentropic and isothermal components. For the isentropic machines,... 

The total circulator power is —63.82kWsmor, which is less than at standard conditions because of greater dissociation. 

The example in the next section demonstrates that the full fuel chemical exergy is obtainable at standard conditions only. The equivalent calculations for hydrogen, and for both fuels at 10 bar, are left as exercises for the reader. Without the unachievable circulator power , the combined electrical - - Carnot powers are fairly evenly matched (Table A.4). 

At 1 bar and 1300K, AGf = —175.8 and A = —56.81, and for the Faradaic reformer AG = —103.3/3 = —34.43 and A = 254.6/3 X (1002/1000) = 85.04. The Faradaic reformer is now somewhat awkward. It needs a large supply of reversible heat at 1300 K from a heat pump or from the fuel cell, and provides an electrical output. Current from the fuel cell would have two functions. Firstly to generate shaft power to supply the missing part of the Carnot input of the reformer, 85.04 — 56.81, and secondly to power a motor generator, with the correct potential difference, to back off the current output of the reformer. Circulator power is not required to complete the transaction. 

Table A.6 The circulator power for Figure A.4 is given in Table A.6.

By the direct oxidation route below, the result is —889.5 — 817.9 = — 1707.4Wsmor Both results are approximations, the errors being in concentrations and circulator powers. The direct oxidation route error, due to two-phase water production (See Section A.3.11), is larger than in the reformer route, so that the reformer route answer —1807.8 W smol is the more accurate. 

Hence, the two routes, with and without reformer, have the same overall equilihrium thermodynamics at standard conditions, the same electrical power, zero Carnot power, and the same net circulator power. However, both the equilibrium constant calculation routes are approximate. The concentrations are in error as a result. See Section A.3.9. 

The reformer route gives —990 — 817.9 = —1807.9 above (Section A.3.9). The mismatch in circulator powers is acceptable for two disparate calculations involving approximate equilibrium constants approximate concentrations and logs of very large pressure ratios. 

The numbers 890 and 990 are relatively doubtful circulator powers, while 818 is electrochemical power. 

Ammonia Hot pot absorber On many occassions, plastic packing melted upon solution circulation (power) failiue. Absorber feed was cooled by the regenerator rdboiler. This cooling was intemqjted when circulation ceased, causing hot feed to enter the column. Either avoid plastic packing in ammonia hot pot absorbers or instrument absorbers to avoid hot feed entrance upon power failure. 

The attack tank is cooled by circulating the slurry through a low-level flash cooler, in which the reaction slurry is cooled by evaporation of water under vacuum. Circulating power requirements are kept to a minimum by using an axial-flow circulation pump and by the low elevation of the flash cooler above the attack tank. The temperature in the attack tank is controlled by varying the vacuum applied to the flash cooler. 

Jurdik et al. (2002)). It should be noted that, for a number of fixed-wavelength lasers (such as NdrYAG lasers), frequency doubling is implemented in intra-cavity configurations, which exhibit the benefit of automatic resonator-enhanced circulating power of the pump wave conversion efficiencies of more than 50 per cent are routinely achieved in commercial green CW Nd YAG laser systems, and values of close to 90 per cent are not uncommon (e.g. see Schneider et al. (1996)). 

A common goal of 1000 MWe plant output was adopted for all designs, although it was not feasible to exactly meet this goal since the circulating power fraction and its effect on total plant output differed for the different concepts, and was impossible to accurately determine ahead of time. Actual electrical outputs varied from 843 MWe (E-Beam Solenoid) to 1253 MWe (EBT). 

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