Pressure-recovery

If the flow process is an isentropic change, the total pressure poa remains unchanged throughout the nozzle flow. However, the process of the generation of a shock wave in the divergent part increases the entropy and the total pressure becomes Pq2- It is evident that the inlet performance increases as po2 approaches Po.  

When the compression process in the diffuser involves heat loss, the total enthalpy decreases from hoa to ho2- The enthalpy recovery factor, r, j, is defined as 

The specific heat ratio of the air, y, is considered to remain unchanged during the compression process in the diffuser. 

The results of the analysis indicate that the pressure recovery factor is increased by the combination of several oblique shock waves and one weak normal shock wave in order to minimize the entropy increase at the air-intake. 

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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 resulting overall energy balance for the plant at nominal load conditions is shown in Table 3. The primary combustor operates at 760 kPa (7.5 atm) pressure the equivalence ratio is 0.9 the heat loss is about 3.5%. The channel operates in the subsonic mode, in a peak magnetic field of 6 T. AH critical electrical and gas dynamic operating parameters of the channel are within prescribed constraints the magnetic field and electrical loading are tailored to limit the maximum axial electrical field to 2 kV/m, the transverse current density to 0.9 A/cm , and the Hall parameter to 4. The diffuser pressure recovery factor is 0.6. 

Environmental Impact. The volume of waste remover from these products is remarkably increased when compared to methylene chloride, petroleum, and oxygenate removers, since both /V-methy1pyrro1idinone and dibasic esters have low vapor pressures. Recovery of the remover after use is difficult because the finish is tesolubili2ed by the remover. A representative dibasic ester formula appears below for a thickened water rinse finish remover. 

The orifice coefficient deviates from its value for sharp-edged orifices when the orifice wall thickness exceeds about 75 percent of the orifice diameter. Some pressure recovery occurs within the orifice and the orifice coefficient increases. Pressure drop across segmental ori-fiees is roughly 10 percent greater than that for concentric circular orifices of the same open area. 

For turbulent flow, with roughly uniform distribution, assuming a constant fricdion factor, the combined effect of friction and inerrtal (momentum) pressure recovery is given by... 

The hest answer is an exhaust designed for 2 inHg and equipped with exhaust-hlade diffuser. This will protect at 1 inHg and give some pressure recovery at 3 inHg hy virtue of its venturi action. 

For any control valve design be sure to use one of the modem methods, such as that given here, that takes into account such things as control valve pressure recovery factors and gas transition to incompressible flow at critical pressure drop. 

The most frequently encountered flashing problems are in control valves. Downstream from the control valve a point of lowest pressure is reached, followed by pressure recovery. A liquid will flash if the low pressure point is below its vapor pressure. Subsequent pressure recovery can collapse the vapor bubbles or cavities, causing noise, vibration, and physical damage. 

Static pressure recovery method. The diameters are selected in such a way that the same static pressure is available before every connection. The duct reduction is selected in such a way that the gain of static pressure is in balance with the friction losses up to the next connection point. This method may result in fewer control devices at connection points or outlets. Low velocities and large diameters at the end of the system may be the result of this design approach. 

Moholkar et al. [11] studied the effect of operating parameters, viz. recovery pressure and time of recovery in the case of hydrodynamic cavitation reactors and the frequency and intensity of irradiation in the case of acoustic cavitation reactors, on the cavity behavior. From their study, it can be seen that the increase in the frequency of irradiation and reduction in the time of the pressure recovery result in an increment in the lifetime of the cavity, whereas amplitude of cavity oscillations increases with an increase in the intensity of ultrasonic irradiation and the recovery pressure and the rate of pressure recovery. Thus, it can be said that the intensity of ultrasound in the case of acoustic cavitation and the recovery pressure in the case of hydrodynamic cavitation are analogous to each other. Similarly, the frequency of the ultrasound and the time or rate of pressure recovery, are analogous to each other. Thus, it is clear that hydrodynamic cavitation can also be used for carrying out so called sonochemical transformations and the desired/sufficient cavitation intensities can be obtained using proper geometric and operating conditions. 

One of the simplest approaches to quantify the pressure field downstream of the constriction used to generate cavitation is to assume linear pressure recovery profile. Yan et al. [8] have used similar approach also considering a single bubble to be existing independent of the other bubbles. Such an approach may be adequate when the intensity of turbulence is quite low i.e. for a venturi type constriction or any other constriction with a smooth variation in the cross-sectional flow area. The pressure recovery from the point at which cavitation starts to any downstream pipe position can be approximated by a linear expression with respect to the distance downstream of the constriction. In such a case, the local pressure at any downstream position can be estimated as ... 

Increasing pipe size downstream of the orifice (which offers a faster pressure recovery) is another option to intensify cavitation effects, but using pipes of larger size would require higher volumetric flow rates in order to carry out operation at the same cavitation number and this, results in an increase in the processing cost. 

Because A < A2 and the losses are small, this shows that P2> Px, i.e., the pressure increases downstream. This occurs because the decrease in kinetic energy is transformed into an increase in pressure energy. The diffuser is said to have a high pressure recovery. ... 

The pressure recovery is reduced by the friction loss, which is relatively high for the sudden expansion. The pressure recovery is therefore relatively low. 

The total friction loss in an orifice meter, after all pressure recovery has occurred, can be expressed in terms of a loss coefficient, ATr, as follows. With reference to Fig. 10-12, the total friction loss is P — P3. By taking the system to be the fluid in the region from a point just upstream of the orifice plate (Pj) to a downstream position where the stream has filled the pipe (P3), the momentum balance becomes... 

The flow coefficient Cv is determined by calibration with water, and it is not entirely satisfactory for predicting the flow rate of compressible fluids under choked flow conditions. This has to do with the fact that different valves exhibit different pressure recovery characteristics with gases and hence will choke at different pressure ratios, which does not apply to liquids. For this reason, another flow coefficient, Cg, is often used for gases. Cg is determined by calibration with air under critical flow conditions (Fisher Controls, 1977). The corresponding flow equation for gas flow is... 

In some cases, one or more of the terms on the right hand side of equation 1.16 will be zero, or may be negative. For downward flow the hydrostatic pressure increases in the direction of flow and for decelerating flow the loss of kinetic energy produces an increase in pressure (pressure recovery). 

Reference Feed Water Temperature Pressure Recovery 3.52 NacI Soln. 25 C. 55 Kg/cm G 302 ... 

Figure D-3. Pressure recovery with isentropic and non-isentropic changes.

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