Diagrams reduced pressure

Figure 10.1 presents the part of the refining diagram that includes the atmospheric and reduced pressure distillations. 

An interesting application of this method is the preparation of diamond films which may be obtained from a precursor such as CH4, C2H2 and H2 activated by heating, microwaves, etc. typically at 600-1000°C at a reduced pressure. The direct deposition from the gas to the surface results in the formation of metastable diamond whereas, according to the phase diagram (see Fig. 5.37), the production of stable bulk diamond requires very high pressure and temperature. Kinetically, the... 

Figu re .2 Schematic diagram of a packed-bed solid gas bioreactor working at reduced pressure based on the flash vaporization of liquid substrates in an inert carrier gas. 

According to the experiments of Andress [6] the composition of the Knecht compound after being kept under reduced pressure for some time should be denoted by the formula 2C6H10O5 HN03. Andress has demonstrated that the compound produces a characteristic X-ray fibre diagram. 

As seen in fii, x is, as a first approximation, a universal function of B and x it is evident, therefore, that for a definite reduced temperature and reduced pressure, the right-hand side of equation (20.2fi) has the same value for all gases. It is consequently, possible to construct a generalized diagram giving the (approximate) value of (II — H)/T for any gas with the reduced pressure as coordinate and the reduced temperature as parameter. Such a diagram is represented in Eig. 14. ... 

Figure 2.1. The phase diagram of the hard-sphere system as a plot of reduced pressure versus reduced density based on the results of Hoover and Ree [24],...

Vacuum distillation can be thought of as fractional distillation under reduced pressure. Figure 6-2 shows a block diagram of the equipment needed for distillation down to about 0.1 torr (0.0133 kPa). 

The vacuum pumps discussed in Chapter 6 are capable of reducing the pressure to about 0.1 torr when they are new, are well trapped, and have clean oil in them. This is not a sufficiently low pressure to permit a high efficiency molecular distillation. A previous example calculation indicated that 10" torr or less is necessary. The most common method for reducing pressures from 10" to 10" torr (13.3 - 0.013 Pa) is the diffusion pump. Multiple stage diffusion pumps are capable of reducing pressures to 1 O torr. A diagram of a down jet diffusion pump is shown in Figure 7-11, p. 79. 

In practically all modem apparatus for laboratory distillation certain functions are now automatic. Heating is often controlled by contact thermometers, and the rate of evaporation of the charge with differential manometers. Reduced pressures are also frequently kept constant with automatic units. In fact, the present trend is towards fully automatic control of the conditions of distillation and simultaneous recording of the data measured, an object that has already been reached in many industrial installations. The ideal procedure is for the mixture to be merely introduced into the apparatus and the latter switched on it then automatically yields the required products of distillation and at the same time prepares a diagram of the top and bottom temperatures and other data that may be needed. 

When the values of thermal conductivity of some simple compounds cannot be determined at the operating conditions desired, it is always possible to refer to the diagram in Figure 7.4. This diagram reports the reduced thermal conductivity, kr = k/kc, as a function of a reduced pressure, Pr = P jPc, and reduced temperature Ty = T/Tc, which represent the operating pressure and temperature divided by the critical pressure and temperature, respectively. 

FIGURE7.11 Diagram of Reduced Viscosity as a Function of Reduced Pressure and Temperature (Bird et al., 1960, p. 16)... 

A cause and effect diagram shows logic for a function where two valves will be closed and a pump will be de-energized when either of two pressure sensors senses that pressure in a vessel goes too high. Valve 1 cuts off inlet feed to reduce pressure in the vessel. Valve 2 closes the outlet to prevent process disturbance downstream. De-energizing motor contactors turn off the pump in order to prevent pump failure. What equipment is part of the safety instrumented function ... 

Table 23.3 summarizes the conditions at each state point. (Points 2s and 4s represent points the conditions for isentropic processes input properties in the table are underlined.) Point a is at atmospheric conditions (the dead state). Point 1, the compressor inlet, is reached after the atmospheric air undergoes a throttling process (constant enthalpy) and experiences a 0.2 psi pressure drop, and point 2s would be achieved in an isentropic compressor. The ratio of the reduced pressure equals the ratio of the actual pressures for an isentropic process. In point 2, the enthalpy is calculated from the compressor isentropic efficiency. In the combustion chamber, the pressure drops 2 psi and the temperature is increased to 1800°F. Point 4s and 4 are analyzed similarly to 2s and 2. Finally, the pressure drops to point 5 where the air enters the atmosphere. The accompanying h-s (or T-s) diagram shows the cycle and includes all of the pressure drops and turbine and compressor inefficiencies. 

Figure 8.49. Schematic diagram of the ultra-high vacuum (UHV) equipment. The equipment comprises a sample chamber and a main chamber (for the deposition). In the former chamber, the substrate can be baked, if necessary, under a moderately reduced pressure (approximately 10 Torr) the material deposition is carried out in the latter chamber at high vacuum (approximately 10 Torr). TMP denotes a turbo-molecular pump.

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