GAS PRESSURE AND FLOW RATE

While gas flow rates vary between the different systems, ranging from 20 to 300,000 sccm, film quality and to a lesser extent, deposition rates are relatively insensitive to gas flow rates.f  

Gas pressures may range from 10 mtorr in ECR MW PACVDl to atmospheric pressure in flame depending on deposition 

A relatively low gas pressure favors a high nucleation density and a small crystal size,l l while a relatively high gas pressure fosters ahigh linear growth rate (Fig. A low gas pressure also lowers the rate of atomic hydrogen recombination in the gas phase. 

A recent study on DC thermal plasma CVD of diamondf demonstrated the existence of an optimum pressure at 270 torr, at which the 

In another HFCVD experiment, the influence of gas pressure on diamond film coverage and crystal size was studied. As shown in Fig. 6, the crystal size and surface coverage attain a maximum at 1.3 kPa ( 10 torr). Crystal quality and phase purity are both optimized around a pressure value of 4 kPa (30 torr). At 665 Pa ( 5 torr) an amorphous film covers the substrate and ball-like particles form. 

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Blowers, fans, and vacuum pumps can be used as gas movers to provide necessary energy to transport the solids. In a negative-pressure conveying system, the vacuum pump is located downstream of the material collection device. In the positive-pressure conveying systems, the blowers or fans are installed upstream of the solids feeding equipment. The selection of a gas mover is primarily based on gas flow rate and pressure drop requirements for the successful transport of solids. 

Figure 14 Effect of temperature on the overall reaction rate at different fixed liquid and gas flow rates and pressures. (From Ref. 41.)...

The influence of other, minor variables can also be adjusted in order to improve performance. Thus, in addition to the typical parameters [viz. rf power, power density, plasma gas flow-rate and pressure, ion sampling distance, anode orifice diameter, and sample size, thickness and shape (pin-like or planar)], the efficiency of GD sampling as regards analytical stability, reproducibility, and quantitation and detection limits, also depends on cell configuration — which has strong effects on radial diffusion processes. 

This component generates and supplies the vapor precursors that will be delivered to the reactor chamber. The delivery of precursors depends on the source temperature, carrier gas flow rate, and pressure of the reaction chamber. 

The scrubbing vessel contains only two internals a gas sparger at the bottom and a mist eliminator at the top. The vessel size is determined by the feed gas flow rate and pressure, the hydrogen sulfide content of the gas, and the desired turnaround time. Design guidelines include... 

Based on the above fundamental studies, an intermediate-temperature alkaline methanol fuel has been developed and its performance is measured using a single-cell system with temperature control, gas flow rate and pressure control, and liquid flow rate and pressure control. 

Process Gas flow rate and velocity Pollutant concentration Variability of gas and pollutant flow rates, temperature, etc. Allowable pressure drop... 

Parameter studies have shown that single-layer nanotubes can be produced by the arc method under a wide range of conditions, with large variations in variables such as the buffer gas pressure (100-500 Torr), gas flow rate, and metal concentration in the... 

The thesis of Steward indicates that the overall liquid film and mass transfer coefficients were functions of the gas flow rate and the column pressure and are independent of the liquid flow rate and inlet air temperature. The gas film heat transfer coefficient was found to be a function only of the air flow rate. 

An interesting and practically valuable result was obtained in [21] for PE + N2 melts, and in [43] for PS + N2 melts. The authors classified upper critical volumetric flow rate and pressure with reference to channel dimensions x Pfrerim y Qf"im-Depending on volume gas content

channel entrance (pressure of 1 stm., experimental temperature), x and y fall, in accordance with Eq. (24), to tp 0.85. At cp 0.80, in a very narrow interval of gas concentrations, x and y fall by several orders. The area of bubble flow is removed entirely. It appears that at this concentration of free gas, a phase reversal takes place as the polymer melt ceases to be a continuous phase (fails to form a continuous cluster , in flow theory terminology). The theoretical value of the critical concentration at which the continuous cluster is formed equals 16 vol. % (cf., for instance, Table 9.1 in [79] and [80]). An important practical conclusion ensues it is impossible to obtain extrudate with over 80 % of cells without special techniques. In other words, technology should be based on a volume con-... 

A stripper operating at a high pressure drop will require a smaller volume than a similar stripper at a lower pressure drop. This reduces the capital cost for the tower, but increases the blower cost. Towers designed and built to operate at a low pressure drop have the flexibility to increase the gas flow rate and hence the air/water ratio, should the future influent concentration increase or the effluent limitation decrease. Towers designed for high pressure drops do not have this flexibility in operation and would need to decrease the liquid loading to increase the air/water ratio. 

To sum up, the gas-liquid interfacial area, a, increases with liquid and gas flow rates and liquid viscosity a for non-coalescing liquids exceeds that for coalescing ones a for organic liquids does not differ significantly from that for ionic liquids a is higher for non-spherical packings and a improves at elevated pressures. 

This CCS technology with its intrinsic laminar flow condition enables uniform deposition for a wide range of deposition pressure, carrier gas flow rate, and substrate temperature. The deposition rates and layer composition such as co-hosting or doping are adjusted by means of mass flow rate of the carrier gas at constant source temperature using individual electronic MFCs for each source. No recircu-... 

The rate o oxidation o ammonia at atmospheric pressure on single wires and ribbons has been determined as a function of a gas flow rate and catalyst size. In agreement with boundary layer diffusion theory the function rx, where r is the average rate of reaction/unit area, and x is the length of the surface measured in the direction of gas flow, is directly proportional to gas velocity. 

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