Inlets, choosing

Step 4 Set the boundary conditions as you did for entry flow slip/symmetry at the centerline and no-slip on the solid wall. However, at the inlet choose the Normal flow/ pressure option and put in the value 2.5 Pa. At the exit choose the Normal flow/pressure option and put in zero. 

To choose a supply inlet as the local ventilation system is not common because it is difficult to design for the specific spreading of contaminants. This is usually easier with an exhaust hood. However, there are moments when large flow rates or specific flow fields are necessary to transport contaminants or for shielding from contaminants. 

When choosing a supply inlet it is always necessary to be very careful, because the influence of the supply air could reach very far. This is most important when using air jets or similar devices to direct the contaminants in an intended direction, since very small changes in direction or momentum could totally destroy the intended flow field and transport the contaminants to, instead of from, the workers. 

Often the inlet device (air supply) in a ventilated room is geometrically complicated. To resolve the flow around such a device would require a very fine grid. Instead of trying to resolve the complex flow near the inlet device, one can choose to use the box method or the prescribed velocity method.Both methods are based on the observation that downstream of the inlet, the flow behaves like a wall jet. Thus it is important that the bound-... 

The affinity of A and B for the solid phase are different, B is more retained than A. Thus, it is possible to choose flowrates in order to make A move upward and B to move downward, leading to a spatial separation. This system requires inlet lines for the feed and eluent and outlet lines for the raffinate A and extract B. 

Before describing the transition prediction methods, it is instructive to describe how a diabatic map is used. One chooses a desired mass flux and sets the heat flux to be dissipated (assumed uniform along and around the circular channel) up to the desired local length from the inlet to find the corresponding local vapor quality (from an energy balance) and thus the location of this process condition on the map. The... 

Effects of Initiator Parameters. Initiator types can best be characterized by the frequency factor (k ) and the activation energy (E ), and the effect of these parameters on the molecular weight-conversion relationship is shown in Figures 7 and 8. The curves shown are the result of choosing the jacket temperature-inlet initiator concentration combination which maximizes the reactor conversion for each initiator type investigated. 

The reactor volume is taken as the volume of the reactor physically occupied by the reacting fluids. It does not include the volume occupied by agitation devices, heat exchange equipment, or head-room above liquids. One may arbitrarily select the temperature, pressure, and even the state of aggregation (gas or liquid) at which the volumetric flow rate to the reactor will be measured. For design calculations it is usually convenient to choose the reference conditions as those that prevail at the the inlet to the reactor. However, it is easy to convert to any other basis if the pressure-volume-temperature behavior of the system is known. Since the reference volumetric flow rate is arbitrary, care must be taken to specify precisely the reference conditions in order to allow for proper interpretation of the resultant space time. Unless an explicit statement is made to the contrary, we will choose our reference state as that prevailing at the reactor inlet and emphasize this choice by the use of the subscript zero. Henceforth,... 

It is particularly convenient to choose the reference conditions at which the volumetric flow rate is measured as the temperature and pressure prevailing at the reactor inlet, because this choice leads to a convenient physical interpretation of the parameters and CA0 and, in many cases, one finds that the latter quantity cancels a similar term appearing in the reaction rate expression. Unless otherwise specified, this choice of reference conditions is used throughout the remainder of this text. For constant density systems and this choice of reference conditions, the space time t then becomes numerically equal to the average residence time of the fluid in the reactor. 

Since enthalpy changes are path-independent quantities, one is at liberty to choose a convenient path for making the calculation. If we carry out the reaction isothermally at the inlet temperature and then heat the products at constant composition to the effluent temperature, we find that... 

Choosing an increment such that the exit liquor stream and inlet gas streams have compositions X = 0.005 and Y, a mass balance taking 1 m2 as a basis gives ... 

A modern gas chromatograph, whether configured for packed or capillary column use, consists of several basic components. All of them must be properly chosen and operated for successful analysis. These are pneumatics and gas-handling systems, an injection device, an inlet, a column oven and column, a detector and a data system. Since the inception of GC in the 1950s, instrumentation has evolved significantly as new techniques and technologies were developed. This section provides an overview of the major components of a modern gas chromatograph, with details about how to choose components based on analytical needs, and applications. 

For each of the analytical problems below, choose the following characteristics of a gas chromatograph that will solve the problem packed or capillary column, inlet, column dimensions and detector. Justify your choice of each. You may need to use additional sources from the bibliography or references. 

For this problem, the choice of which component of 7 to eliminate is arbitrary. However, if more than one linear mixture exists between the initial/inlet conditions, it may be necessary to choose more carefully. We illustrate this problem in an example flow below. 

Any of the columns of d> can be chosen as the reference vector. However, we shall see that there is an advantage in choosing one of the two inlet streams. Thus, letting c(1) be the reference vector, the matrix is easily found to be65... 

The estimate of the fill time shows that a more detailed study of injection strategy and process parameters is necessary because it is difficult to reach an acceptable production economy with a fill time of about 1 h. An obvious action would be to choose a more efficient resin distribution method than a one-point inlet (e.g., peripheral injection or a multipoint injection). In addition, it would be worthwhile to try to lower the viscosity and increase the pressure. 

Choose an inlet air temperature that is high enough to negate weather effects (outside air humidity or inside room conditions). The air temperature should not be detrimental to the product being granulated. (To achieve consistent process year round, a dehumidification/humidification system is necessary, which provides the process air with constant dew point and, hence, constant drying capacity.)... 

Once a solution is computed for a certain flow situation, both velocity gradients can be evaluated. However, they are not necessarily simply related. A finite-gap simulation requires the following trial-and-error procedure to obtain a specific strain rate specify an inlet velocity compute the solution, evaluate the velocity gradient ahead of the flame, choose another inlet velocity, and recompute. 

Chemical reactors are the most important features of a chemical process. A reactor is a piece of equipment in which the feedstock is converted to the desired product. Various factors are considered in selecting chemical reactors for specific tasks. In addition to economic costs, the chemical engineer is required to choose the right reactor that will give the highest yields and purity, minimize pollution, and maximize profit. Generally, reactors are chosen that will meet the requirements imposed by the reaction mechanisms, rate expressions, and the required production capacity. Other pertinent parameters that must be determined to choose the correct type of reactor are reaction heat, reaction rate constant, heat transfer coefficient, and reactor size. Reaction conditions must also be determined including temperature of the heat transfer medium, temperature of the inlet reaction mixture, inlet composition, and instantaneous temperature of the reaction mixture. 

LP-CVD ZnO In contrast to AP-CVD processes, LP-CVD processes are kinetically limited, i.e., the growth rate of the film depends mainly on the rate of reactions at the growing surface. These reactions become the limiting factor, because the transport time necessary to carry the reactant from the gas inlet to the growing surface is strongly reduced by choosing the low pressure regime. 

Compute the total pumping head. The total head, expressed in feet of water, equals static head + friction head + required nozzle head = 10 + 35 + 8(0.434) = 48.5 ft of water (145.0 kPa). A pump having a total head of at least 50 ft of water (15.2 m) would be chosen for this spray pond. If future expansion of the pond is anticipated, compute the probable total head required at a future date and choose a pump to deliver that head. Until the pond is expanded, the pump would operate with a throttled discharge. Normal nozzle inlet pressures range from about 6 to 10 lb/in2 (41.4 to 69.0 kPa). Higher pressures should not be used, because there will be excessive spray loss and rapid wear of the nozzles. 

Therefore we choose the reactor inlet temperature setpoint as the... 

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