Cooling open circuit

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).

Make up water for these refrigeration units is at 80°F, and feed water for the gas cooler unit is available at 90°F. Barometric water is 90°F. Items 1 and 2 are for a closed-circuit operation with return water at 68°F and total 175 gpm. Note that in order to consolidate the temperature levels of water, it is economical to establish a temperature, such as 55°F, which satisfies the bulk of the requirement, and then design the other phases of the plant process to also use this water temperature. Item 3 is an open-circuit operation because the water is sent to waste after absorbing certain corrosive vapors and cooling the bulk of the gas. 

SPRAY-COOLING CIRCUIT - An open cooling-water circuit which sprays water and cools by evaporation, for example, a cooling tower, all evaporative condenser, an air washer, or a spray-coil unit. 

The first application of discotic liquid crystal to organic thin film solar cells is of a binary blend of liquid crystalline phthalocyanine (Pc) as p-type of semiconductor and non- mesogenic PTCDI derivative as n-type [45], where the active layer was not a BHJ type, but had a p-i-n junction (Fig. 8.11). The Pc layer was fabricated by spin-coating and heated up to the isotropic phase followed by cooling to obtain a spontaneously formed homeotoropic alignment on ITO-coated substrate. The n-type layer was deposited by sublimation on Pc layer and finally the counter A1 electrode was deposited in vacuo. The performance was shown simply as short circuit current, Isc = 0.4 mA cm , open circuit voltage, Vqc = 0.3 V and external quantum efficiency, EQE 0.5 %. 

Consider first the simple extrinsic photoconductor. Here the sample is a semiconductor containing a single impurity level, the source of the free electrons (or holes) present in the sample. Thus the fluctuation in the number of the free carriers arises from the fluctuation in the generation and recombination rates through that level. If it is assumed that the temperature is so low that very few of the extrinsic centers are thermally ionized (which is valid for most extrinsic cooled photoconductive infrared detectors), then the short circuit g—r noise current and the open circuit g — r noise voltage which appear only in the presence of a bias current Ig, are given by... 

T. In a wet or open circuit cooling tower, a fan draws ambient air past (usually countercurrent to) a flow of water. Depending upon e inlet humidity (water content) of the ambient air, more (low humidity) or less (high humidity) water can be evaporated into this air. When the water evaporates, the heat of vaporization required by that portion of the water which is evaporated is taken from the remaining mass of water, thereby reducing its temperature. 

Within the 5,500 operational hours of automotive PEMFC systems, the stack could sit for a long time at idle condition, i.e., when no power is supplied to the propulsion system, and the only power drawn from the fuel cell stack is that required to support the fuel cell system andllaries (e.g., cooling pumps). This results in cathode potentials of approximately 0.90V (Mathias et al. 2005). This idle time could total over several thousand hours depending on the particular usage profile. The stack could also be at open circuit voltage (OCV) condition, where no current is drawn from the stack and the eathode potential increases to approximately 0.95 V. This can occur just before fuel ceU system shutdown, immediately after startup, as weU as in the case of battery/fuel ceU hybrid systems in which the battery provides the electrical load under low power or idle conditions. The accumulated time at OCV condition for 38,500 start/stop cycles could be over lOOh (38,500 cycles x 10 s per cycle). Figure 8 shows the predicted carbon weight loss as a function of time at these two potentials, based on the carbon corrosion... 

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