Velocity-pressure-transfer point

VCM vinyl chloride monomer VPTP velocity-pressure-transfer point... 

After observing each cycle, the shot size and transfer point will be adjusted frequently to set the process so that the first stage accomplishes 95 to 98% of the fill as measured by shot weight. Once the first stage shot size, transfer, velocity and pressure are set, we can set 2nd stage packing pressure. Adjust pack pressure as needed, but do not... 

Before proceeding with the dilute-phase development, an explanation of the difference between the dilute phase and dense phase is in order. If one considers the vertical transport of soHds by a large quantity of gas, one finds a particular pressure drop. As the gas velocity is reduced at the same rate of transport of solids, the pressure drop decreases. This can be seen in Fig. 4-1 in going from points to point.5 on the curve. At one particular velocity of the gas a minimum pressure drop is experienced. This minimum pressure drop point may be used as the dividing point between dilute- and dense-phase transfer. Lower gas velocities produce higher pressure drops and the... 

For the injection step, two control loops are typically used. The screw will first travel until a transfer point is reached where control switches from ram velocity control to pressure control. Methods to switch from velocity control to pressure control can use the following modes (1) time, (2) screw position, (3) hydraulic pressure, (4) cavity melt pressure, or (5) other cavity event detectors. Time is generally considered to be the worst method since it does not relate to what is happening in the cavity. Monitoring cavity melt pressure has generally been accepted as the best method but new transducers, such as fast response TCs are also gaining acceptance. 

A fluid whose properties are essentially those of o-dichlorobenzene is vaporised in the tubes of a forced convection reboiler. Estimate the local heat-transfer coefficient at a point where 5 per cent of the liquid has been vaporised. The liquid velocity at the tube inlet is 2 m/s and the operating pressure is 0.3 bar. The tube inside diameter is 16 mm and the local wall temperature is estimated to be 120°C. 

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