Overall cooling effectiveness

Where hot ambient temperatures are expected, overall turbine efficiency and horsepower output can be increased by installing an evaporative cooler in the inlet. Inlet air flows through a spray of cold water. The temperature of the water and the cooling effect caused by the inlet air evaporating some of the water cools the inlet air. In desert areas where the inlet air is dry and thus able to evaporate more water before becoming saturated with water vapor, this process is particularly effective at increasing turbine efficiency. 

Reaction is first order in gas reactant. 3. Gas and liquid stream are in plug flow. 4. Reactor is isothermal. 5. Gaseous reactant concentration in the gas phase is constant throughout the reactor. 6. A fraction of the catalyst external surface (tice) is covered by a flowing liquid film while the rest is exposed to a thin stagnant liquid film. Assumption 2 was verified by already reported kinetic studies. A water cooled reactor with low feed concentrations of a-methylstyrene operated between 15°C and 20°C satisfies assumptions 1 and 4 due to low volatility of the liquid reactant and due to small overall heat effects, respectively. 

Perhaps the most firmly established indicator of global change is increasing CO. concentrations. Carbon dioxide exerts an effect on stratospheric ozone as follows. While in the troposphere infrared radiation from CO. tends to be trapped in the stratosphere infrared radiation from CO2 tends to escape, leading to a cooling effect. One can then ask what effect an overall cooling of the stratosphere would have on the distribution of ozone. 

If the coolant entered at 13°C, T would equal 8-0 and the heat-cooling effect. The overall heat transfer coefficient H) is made up of the sum of the reciprocals of the heat resistances including those of (/) the thin liquid layer dragging on the surface of the plate, because the Reynolds number is low or the surface is rough, (h) the plate itself, and Hi) any scale deposited on the plate and derived from protein or water hardness. Very significant reductions in the coefficient arise from (/) and more so from Hi). Therefore, from this standpoint, it is desirable to have very turbulent flow and clean plates. 

Another explanation could be linked to the fact that the hydrocarbon fractions (essentially methane) are not totally converted in the reforming boards. Therefore, part of the reforming reactions occurs at the beginning of the tubes, that is at the bottom plane. This causes a local cooling effect. A variation of the overall FC factor determines a modification of the chemical equilibrium inside the reformer boards, and as a consequence a modification of the cooling effect at the bottom plane when increasing the overall fuel consumption, there is a decrease... 

Other more subtle heating and cooling effects may also play an important role. For example, when a mass of crystallizable polymer is cooled from its melt, the inner regions of the mass tend to cool more slowly than the other surfaces because of a slow overall heat-transfer process. This leads to a more highly crystalline, and hence brittle, inner core. This cooling-induced morphology may be beneficial or detrimental, depending on the use of the product. 

Thermoplastic polymers are also prone to recrystallisation processes, particularly after rapid cooling employed in many manufacturing processes. Sometimes these are very evident as with PET (Figure 2.5), though sometimes the overall annealing effect does not show an overall exothermic event. The kinetics of recrystallisation processes are usually described by the Avrami equation discussed below. 

Analogous effects are caused by the inappropriate use of utilities. Utilities are appropriate if they are necessary to satisfy the enthalpy imbalance in that part of the process. Above the pinch in Fig. 6.7a, steam is needed to satisfy the enthalpy imbalance. Figure 6.86 illustrates what happens if inappropriate use of utilities is made and some cooling water is used to cool hot streams above the pinch, say, XP. To satisfy the enthalpy imbalance above the pinch, an import of (Q mjj,+XP) is needed from steam. Overall, (Qcmin+AP) of cooling water is used. ... 

It might be thought that the small number of molecules in a typical supersonic jet or beam would seriously limit the sensitivity of observation of the spectra. Flowever, the severe rotational cooling which may be produced results in a collapsing of the overall intensity of a band into many fewer rotational transitions. Vibrational cooling, which greatly increases the population of the zero-point level, concentrates the intensity in few vibrational transitions, and these two effects tend to compensate for the small number of molecules. 

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