Nozzle pressure recovery

Flow Nozzles. A flow nozzle is a constriction having an eUiptical or nearly eUiptical inlet section that blends into a cylindrical throat section as shown in Figure 8. Nozzle pressure differential is normally measured between taps located 1 pipe diameter upstream and 0.5 pipe diameters downstream of the nozzle inlet face. A nozzle has the approximate discharge coefficient of an equivalent venturi and the pressure drop of an equivalent orifice plate although venturi nozzles, which add a diffuser cone to proprietary nozzle shapes, are available to provide better pressure recovery. 

The same research group also introduced a microfabricated digital wall attachment amplifier [11] for bistable control of flow. An SEM image of a microscale digital wall attachment amplifier formed on PMMA is illustrated in Fig. 6a. The pressure in one of the output ports (opposite to the control port used) is shown in Fig. 6b for various values of the control port pressure. The output pressures were measured at output 2, while the input control pressure was varied at inlet 1. In the experiment, a jet of 330 hPa pressure was supplied through the main nozzle, while the pressures at the control ports were varied from 0 to 12 hPa. The experimental results showed that if the jet was attached to the wall next to a control port, then temporary application of pressure (12 hPa) to that control port guided the jet to the opposite wall. The jet continued to flow along that wall after the removal of the control jet. A minimum supply pressure was needed for the action of this amplifier. The experimental results also showed that the supply pressure had no effect on the pressure recovery (ratio of maximum output to input pressure) and flow recovery (ratio of maximum output to input flow) in this amplifier. 

Better yet, just measure the pressure at Pi and forget about the corrections for nozzle losses. On the other hand, the fluid flowing from a nozzle into a vessel will usually gain in pressure (pressure recovery). 

The vapor flow in a heat pipe is analogous to the compressible fluid flow in a converging-diverging nozzle (see Figure 13.10). In curve A of Figure 13.10, at back pressure (PJ, the pressure decreases in the converging section with an increase in velocity up to the throat. In the divergent section, a pressure recovery occurs with a decrease in velocity. In curve B, at back pressure (Fj), the velocity becomes sonic at the throat, and the maximum mass flow rate... 

The vapor flow in the heat pipe vapor case is quite similar to the flow characteristics encountered in a converging-diverging nozzle. Very high velocity, choked flow, and pressure recovery are evident in the operation of heat pipes, which are functions of the heat input and rejection rates. 

Potential hydrocarbon losses from the overpressuring of operating vessels are controlled first by staged computer alerts and/or manual alarms to provide for correction of the condition. If the overpressure exceeds a second set point, pressure relief valves vent the vessel contents to a flare release system. The flare system provides a means of controlled burning of hydrocarbon vapors at a nonhazardous point to avoid fire or explosion risks. Smoke problems from flares are avoided by more efficient designs that use multiple nozzles and low pressure operation to promote clean combustion [57]. Greenhouse gas concerns should more frequently stimulate an interest in energy recovery options from flared hydrocarbons. 

This is really an extension of the transfer proover concept to a broad range of flow. With the new speed of soimd data the critical flow nozzle may have application. With recovery sections they have low pressure loss and multiple nozzles can provide for a wide range of flow and pressrue. 

General purpose screws can be used, for example, with an L D ratio of about 18 1 and a constant pitch of ID. The feed zone should be approximately 0.5L, the compression zone 0.3L and the metering zone 0.2L a compression ratio of about 2 1 should be sufficient. The screw is usually fitted with a nonreturn valve but valves are not essential on the nozzle unless high back pressures are involved. The best results have been obtained by using spring loaded or hydraulically operated types decompression or suck-back is also used. High speed low torque screw motors are often preferred to achieve short screw recovery times. 

Steam condensers (after turbo generator sets) are used to maintain the low pressure of turbine exhausts as well as to recover condensate for recycle to the boiler feedwater tank. Here it is necessary not to subcool the condensed hquid, so that the maximum heat recovery can be done (by obtaining condensate at as high a temperature as possible. The configuration of steam inlet nozzle and cooling water inlet/ outlet nozzles etc should be designed accordingly. 

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