Two pressure drop

The pressure drop to the reject stream is the most significant h will always be the greater of the two and ultimately determines hydrocydone capacity. The relationship between the two pressure drops is also important and can be used for control purposes For any given reject flow rate, the ratio will be approxi-... 

For each packing, sketch an empirical curve such that (a) its upper end passes through the point Fsf, APF with a slope approaching infinity, and (b) its lower end becomes tangent to the straight, wet-pressure-drop line at an abscissa value of Fsf/2. These two pressure-drop curves for the loading regions are shown by the dashed lines of Fig. 11.1. 

For the turbine there are three pressure drops to consider. One for the compressor discharge AP2, one for the practical throttling effect in the combustion chamber AP23 and one for the turbine exhaust pressure due to ducting AP4. The two pressure drops at the inlet to the turbine can be combined as,... 

Another important design parameter that can be predicting using the models described earlier is pressure drop. The usual [8,10,23,24] simplified assumption rests on the additivity of two pressure drop contributions given by ... 

The main characteristics of the safety valves are determined by the two pressure drops, APi and AP2, given by AP = (P2 - Pi), where Pi is a sodium pressure above the valve, and P2 below the... 

The most common technique for estimating thermal stability is called the Jet Fuel Thermal Oxidation Test (JFTOT). It shows the tendency of the fuel to form deposits on a metallic surface brought to high temperature. The sample passes under a pressure of 34.5 bar through a heated aluminum tube (260°C for Jet Al). After two and one-half hours, the pressure drop across a 17-micron filter placed at the outlet of the heater is measured (ASTM D 3241). 

The initial condition for the dry gas is outside the two-phase envelope, and is to the right of the critical point, confirming that the fluid initially exists as a single phase gas. As the reservoir is produced, the pressure drops under isothermal conditions, as indicated by the vertical line. Since the initial temperature is higher than the maximum temperature of the two-phase envelope (the cricondotherm - typically less than 0°C for a dry gas) the reservoir conditions of temperature and pressure never fall inside the two phase region, indicating that the composition and phase of the fluid in the reservoir remains constant. 

For both volatile oil and blaok oil the initial reservoir temperature is below the critical point, and the fluid is therefore a liquid in the reservoir. As the pressure drops the bubble point is eventually reached, and the first bubble of gas is released from the liquid. The composition of this gas will be made up of the more volatile components of the mixture. Both volatile oils and black oils will liberate gas in the separators, whose conditions of pressure and temperature are well inside the two-phase envelope. 

Pressure Drop. The pressure drop across a two-phase suspension is composed of various terms, such as static head, acceleration, and friction losses for both gas and soflds. For most dense fluid-bed appHcations, outside of entrance or exit regimes where the acceleration pressure drop is appreciable, the pressure drop simply results from the static head of soflds. Therefore, the weight of soflds ia the bed divided by the height of soflds gives the apparent density of the fluidized bed, ie... 

Figure 13 shows two pipe distributors, one in a branched and one in a ring configuration. These distributors minimize weeping, have good turndown, may requite the lowest pressure drop, and avoid the need for a plenum chamber. They are also well suited to multiple-level fluid injection. The disadvantages of these distributors are that there are defluidized soHds beneath the distributor and the mechanical design is more complex. 

When two phases are present the situation is quite complex, especially in beds of fine soHds where interfacial forces can be significant. In coarse beds, eg, packed towers, the effects are often correlated empirically in terms of pressure drops for the single phases taken individually. 

In order to vaUdate this concept, an experiment was performed using an ice-water slurry and it was found that a 25% ice slurry had a two-to-four-times higher thermal capacity than chilled water (44). As the concentration of ice particles in the ice-slurry mixture increased up to 30%, no significant change of pressure drop was reported compared to pure water. 

The pressure drop for gas—Hquid flow is deterrnined by the Lockhart-MartineUi method. It is assumed that the AP for two-phase flow is proportional to that of the single phase times a function of the single-phase pressure drop ratio P. 

Fig. 33. Lockhart-MartineUi plot for two-phase pressure drop.

The catalyst combines two essential ingredients found in eadier catalysts, vanadium oxide and titanium dioxide, which are coated on an inert, nonporous carrier in a layer 0.02- to 2.0-mm thick (13,16). Other elements such as phosphoms are also used. Ring-shaped supports are used instead of spherical supports to give longer catalyst life, less pressure drop though the reactor, and higher yields (17,18). Half rings are even better and allow more catalyst to be loaded (18). 

Heat exchangers use energy two ways as frictional pressure drop, and as the loss in ability to do work when heat is degraded. 

In the macroscopic heat-transfer term of equation 9, the first group in brackets represents the usual Dittus-Boelter equation for heat-transfer coefficients. The second bracket is the ratio of frictional pressure drop per unit length for two-phase flow to that for Hquid phase alone. The Prandd-number function is an empirical correction term. The final bracket is the ratio of the binary macroscopic heat-transfer coefficient to the heat-transfer coefficient that would be calculated for a pure fluid with properties identical to those of the fluid mixture. This term is built on the postulate that mass transfer does not affect the boiling mechanism itself but does affect the driving force. 

---