Number of operation units

Fixed Capital Investment Raw Material Cost Chemistry, Processes, and Number of Operating Units Required Equipment Selection Utilities and Offsite Costs Labor Content... 

A recent publication of the International Iron and Steel Institute (IISI) lists the total number of operating units in the Western world at the end of 1987 as 100 with a combined effective capacity of 163 million metric tons per... 

Even if the extent of coverage is stated, it will be important to know whether this has been measured by production tonnage, turnover, number of operating units or some other means. 

Vendors best designs show lower angular velocities at larger diameters. The rotational speed is not quite inversely proportional to the diameter, so that the peripheral speed increases slowly with diameter. A review of a number of operating units showed that the number of revolutions per hour is related to the diameter (in meters) hy the equation... 

General regulatory and structural integrity (Si) method(s) foiiowed Light-water reactor type Country (number of operating units)... 

This ratio of characteristic times represents, in fact, a classical feature used in chemical engineering the number of transfer units (NTU) in heat-transfer processes and Damkohler number in a reactor. Here, this number is generalized as a number of operation units (NOU), including operations such as heat/mass transfer, reactions, physical phenomena or their combination ... 

Figure 2.1 Evolution ofthe operation efficiency T as a function of the number of operation units NOU for system orders ranging from —1 to 2 in batch and plug-flow reactors (a) and in continuously stirred tank reactors (b).

To maintain the system efficiency T], the number of operation units is constant ... 

Amplifier complex. A number of operational amplifiers configured for a specific function, packaged and used as a single unit. 

To estimate the number of transfer units for design, the following empirical correlations which were derived from efficiency measurements employing a variety of trays and operating conditions under the aforementioned assumptions are recommended (111) ... 

The resistance units, when used only for starting purpose, are in the circuit for only a short time and are thus short-time rated. However, when they are employed for speed control, braking or plugging operations, in addition to the starting duty, they may be rated for continuous duty. The resistance units are thus classified according to their duty demand, i.e. number of operations per hour (c/h). See Chapter 3 on the duty cycle. 

For comparison, note the relative increase in the number of transfer units if the operation were at a higher pressure as shown by the dotted line for 500 psig. 

Because the heat load, L, Ga and temperatures are known for an operating tower, its performance as represented by the number of transfer units, or tower characteristics can be determined. Solve Equation 9-129 for Ka V/L, or use the modified Merkel diagram, Figure 9-127. This is the number of transfer units operating in the tower. For relative comparison of Ka values see Figure 9-128. 

To understand the mathematics, consider a large empty space into which a number of production units are to be placed, and assume that the major variable to be optimized is the cost of transporting materials between them. If the manufacturing process is essentially a flow-line operation, then the order in which units should be placed is clear (from the point of view of transport costs), and the problem is simply to fit them into the space available. In a job-shop, where materials are flowing between many or all the production units, the decision is more difficult. All the potential combinations of units and locations... 

On many installations, it is normal to plan the number of compressor units and their output so that there is a standby capacity to permit one unit to be shut down for servicing. Where a constant supply of air is essential to operations, standby compressors are a necessity. 

In terms of downstream processes, the flow-rates, compositions, and so on, dictate the size and number of each unit operation for example, while a batch distillation may be used to separate a single feed into a number of different product streams, a continuous distillation train would in general require N columns for N different product streams. The fact that a high degree of modeling is used in the design of each MPI, results in the generally held belief that continuous processes... 

Table 1.5 Dependence of the number of micro channels N, their length L, the cross-sectional area of the reactor S and the pressure drop AP on the micro-channel diameter, when the efficiency (i.e. a fixed number of transfer units) and at least one specific characteristic quantity are kept fixed in each line. Three cases with operation time-scales varying as (c/m)°. are considered [114],...

Where the operating and equilibrium lines are straight, and they can usually be considered to be so for dilute systems, the number of transfer units is given by ... 

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