Control liquid flow

Figure 5 shows a sketch of the experimental apparatus. It consists of a bench scale internal loop airlift, gas and liquid flow control units and a gas humidifier. 

Fig. 5 Experimental apparatus (A) airlift bioreactor (B) gas flow control unit (C) humidifier (Dj) medium tank (D2) dye solution tank (D3) wastewater tank (E) liquid flow control unit...

Liquid fertilizers, potassium orthophosphates in, 20 637 Liquid-film coefficient, 15 695 Liquid filtration, 11 322-323 Liquid flavor forms, 11 576-577 Liquid flow control, in variable-conductance heat pipes, 13 233 Liquid fluidization, 11 791-792 Liquid food ingredients, encapsulated,... 

Almost all kinds of actuators described above have been applied to fabricate gas flow control microvalves [1, 25]. However, for liquid flow control only a few microvalves have been developed. 

Control of liquid flow does not seem to be a problem. There are two versions of liquid flow control one is to use a micro-pump or double cylinder to pressurize the liquid and the other is to use a liquid mass flow controller. In either case, the control of liquid flow seems to be accurate enough for CVD. One design precaution is to minimize the volume of the liquid lines, otherwise changing the source composition takes a long time with a large waste of expensive precursors. 

The reactions were carried out in a TEOM reactor where the weight of the catalyst bed is continuously recorded. The setup is similar to that described previously [8]. The methanol flow was controlled by a liquid flow controller while DME and propene were fed using gas flow controller. The MTO and DTO reactions were carried out at 425°C, WHSV=417h" and a methanol or DME partial pressure of 8 kPa, with helium as diluent. One DTO experiment was also performed at WHSV=600 h" to keep the residence time identical to those from the MTC) experiments. Such high space velocity and low partial pressure were used to avoid non-uniform coke distribution through the catalyst bed, and to keep the conversion well below 100% to minimize secondary reactions of olefins. 

In a microfluidic chip, there are a number of wells at the ends of the microchannel branches. These wells provide not only reservoirs for samples and reagents, but also the connection of electrodes to liquid in the microchannels. The liquid flow control is realized by applying different voltages to different wells simultaneously. In this way one can control the flow rate, and let one solution flowing through a microchannel in the desired direction while keeping all other solutions stationary in their wells and channels. 

After 24 h on stream, water was introduced to the system by replacing He by an equal flow of water vapor. The steam was generated by feeding water by a liquid flow controller (Hi-Tec) to a vaporizer kept at ca. 573 K. The steam was mixed with the synthesis gas just before the reactor inlet. 

In microfluidic systems, liquid flow control is very challenging because of the large flow resistance. As such, electroosmotic flow (EOF), a surface-driven flow phenomenon, is an alternative to pressure-driven flow (PDF), in order to overcome the flow resistance problem. Since the velocity of EOF depends on the surface charge of the channel wall, the surface-charge patterning technique has thus been developed to control liquid flow in a very confined space. 

Trays with drilling or slits in the base plate. Liquid flow controlled across the base plate or drops downward through the base plate openings where the vapor flows counterflow upward, e.g., sieve tray, turbogrid tray)... 

Figure 5.1 shows three commonly encountered feed flow schemes. When the upstream pressure is higher than the column pressure, then only a letdown valve is required, as shown by Figure 5.1 A. If column pressure is greater than upstream pressure, then a pump is required, as shown by Figure 5.IB. If, however, upstream or downstream pressures can vary significantly, then a cascade level control/liquid flow control system such as that of Figure 5.1C is required. The flow signi should be linear—one should use a linear flowmeter or a square-root extractor with an orifice and AP transmitter. This (Figure 5.1C) is really the preferred overall design it provides the most protection and offers the operator the maximum flexibihty.

Build a simulation in HYSYS using water with a flow of 20 kmol h at 15°C and 1 atm as the oifly conponent and the Peng-Robinson equation of state as the fluid property package. Use the default tank volume of 2 m and specify liquid flow control on the Liquid Valve page of the tank unit operation. Calculate the flow out of the tank using Equation W2.1, which describes a linear valve, and then Equation W2.2, which describes a nonlinear valve. In both cases, the outlet flow rate is a function of the liquid head on the tank oifly. 

Build a new system consisting of two streams, two tanks, and a mixer using the Wilson thermodynamic package. Pick any two components that are liquid phase at ambient temperatures. The first stream should be pure component A at 25°C and 100 kPa. The second stream should be pure component B at the same temperature and pressure. Set the flow of the first stream to 400 kg h and the second stream to 100 kg h These flows are consistent with the desired ratio of 4 1 between components A and B. The tanks are used to simulate dead time in the system, so choose relatively small volumes for the tanks and locate them in series with the first stream. Both tanks should be on level control rather than liquid flow control. Simulate process noise with a sine-wave input to the first stream using an amplitude of 50 kg h and a period of 10 min. The system should resemble the one shown in Figure W6.4. 

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