Maintaining Nozzle Efficiency

The velocity of water flowing from the tub through the drain is 20 ft/s. The pressure drop, in psi, of the water as it escapes from the tub, is 

The pressure at Pj is now the 1-psi static head minus the 5-psi nozzle exit loss or negative 4 psig (or positive 10.7 psia). That is, the pressure at the drain is a substantial partial vacuum, or a negative pressure. By the term negative pressure I mean that it is below atmospheric pressure (atmospheric pressure at sea level is 16.7 psia). 

This suggests that the pressure in a water drain can get so low that air could be sucked out of the bathroom and down the drain. Of course, we all see this happen several times a day— typically when we flush a toilet. So much air is drawn into the water drainage piping that we install vents on our roofs to release this air. The only requirement, then, for vapors to be drawn into a flowing nozzle is for the nozzle exit loss to be larger than the static head of liquid above the nozzle. 

Incidentally, if a bird builds its nest on top of one of our roof toilet vents, we find the toilet will no longer flush properly. The experienced 

But how about the liquid at point B Is this liquid also at its boiling or bubble point It is the same liquid, having the same temperature and composition as the liquid at point A. But the pressure at point B is slightly higher than the pressure at point A. 

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In order to maintain high energy efficiency and ensure a long service life of the materials of construction in the combustion chamber, turbine and jet nozzle, a clean burning flame must be obtained that minimizes the heat exchange by radiation and limits the formation of carbon deposits. These qualities are determined by two procedures that determine respectively the smoke point and the luminometer index. 

The temperature is approximately 20°F below the 265°F temperature limit. The sections differ by less than 1 F. This is probably just luck because that good a balance is not really necessary. Also, it should be noted that to maintain simplicity the additional factors were ignored, such as the 10°F temperature pickup in the return stream due to internal wall heat transfer. Also, nozzle pressure drops for the exit and return were not used. Balance piston leakage was not used as it was in Example 5-3. When all the factors are used, the pressures for each section would undoubtedly need additional adjustment as would the efficiency. However, for the actual compression process, the values are quite realistic, and for doing an estimate, this simpler approach may be quite adequate,... 

Turbine efficiency must be maintained over a wide range of Mach numbers and pitching, and efficiency depends in part upon a balance of mgged nozzle construction and the aerodynamic properties of the bucket blade profiles. 

For successful use of such adhesives, not only must the formulation be suitable but the system for application also must be efficient. The molten adhesive must be maintained in a fluid condition and at the correct temperature for application over-heating could cause degradation, and if it is too cold the viscosity of an adhesive might be too high. The hot fluid is pumped to the substrate through a suitable nozzle but if the distance between the reservoir and the nozzle is appreciable there may be cooling and a need for heated hoses. Sometimes, molten adhesive is transferred to a coater of the heated-roller type, where again the control of temperature is important. There is a wide variety of equipment for application and every manufacturer of hot-melt adhesives will advise on systems that are suitable for use with them. 

The DWSA installation can be divided into two main parts. The first part consists of an air preheater, fluidised bed reactor, solid fuel dosing vessel with on-line mass determination system and a hot gas cleaning section, containing a cyclone and a ceramic candle filter (Schumacher type). In the fluidised bed reactor the solid fuel is gasified with air to produce a low calorific value (LCV) gas that is cleaned of fly ash and unreacted solid carbonaceous material. Air and also additional nitrogen can be preheated and is introduced into the reactor by four nozzles just above the distributor plate. The reactor is electrically heated in order to maintain a constant temperature over bed as well as freeboard section. The solid fuel is fed into the bed section in the bottom part Just above the distributor by a screw feeder from beside. The hot gas cleaning section ensures a good gas-solid separation efficiency, with filter temperatures of about 500 C. 

Figure 8.7 shows the droplet size spectra produced by nozzles in the study by Thornhill et al. (1995). They achieved lowest contamination by controlling pressure at 100 kPa, which, like the newer low-drift nozzles such the Turbo Teejet , produce larger spectra than standard flat fan atomisers. However, these settings simply shift the droplet size spectra out of the size range known to be most efficient for pesticides (e.g. Matthews, 1992 Knoche, 1994). The only way to reduce drift and maintain efficient dose transfer is to narrow the droplet spectrum with the optimum range illustrated using nozzles such as the Herbi rotary atomiser. 

The efficiency of the automotive proton exchange membrane (PEM) fuel cell is dependent on many factors, one of which is the humidification of the inlet air. If the inlet air is not sufficiently humid (saturated), then the stack can develop dry spots in the membrane and efficiency and voltage will drop. Therefore, it is necessary to ensure that humid inlet air at the proper elevated temperature is supplied to the stack. Current methods involve utilizing a spray nozzle to atomize water droplets onto a cloth or wire mesh substrate. As the ambient inlet air passes over the cloth it picks up moisture however, the relative humidity drops as the air is heated in the fuel cell. If heat could be supplied to the water efficiently, the system would become independent of the ambient conditions, the inlet air could become more humid at the proper temperatures, and the overall stack could maintain a high level of efficiency. Previous work with power electronic heat sinks and automotive radiators has demonstrated the high efficiency of carbon foam for heat transfer. Utilizing the carbon foam in the PEM fuel cell may reduce the inlet air humidification problems. 

With practically all machines, only the cylinder temperature is directly controlled (see Chapter 1). The actual heat of the melt, within the screw and as it is ejected from the nozzle, can vary considerably, depending on the efficiency of the screw design and the method of operation. Factors affecting melt heat include the time plastic remains in the cylinder the internal surface heating area of the cylinder and the screw, per volume of material being heated the thermal conductivity of cylinder, screw, and plastic (Table 1-6) the heat differential between the cylinder and the melt and the amount of melt turbulence in the cylinder. In designing the screw, a balance must be maintained between the need to provide adequate time for heat exposure and the need to maximize output most economically. 

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