Engineering Calculations

One similarity is that all of the systems described involve processes designed to transform raw materials into desired products. Many of the problems that arise in connection with the design of a new process or the analysis of an existing one are of a certain type given amounts and properties of the raw materials, calculate amounts and properties of the products, or vice versa. 

52 If one travels at 55 miles per hour in a car with a fuel tank capacity of 30.4 liters and a fuel efficiency of 23 miles per gallon, how many minutes can one travel before the fiiel tank is empty Calculate the answer in one line, starting with 30.4 liters on the left and ending with your answer on the right. 

53 On January 4, 1994 a storm deposited 18 inches of snow on the 200 scenic acres of the Cornell campus. An article in the Cornell Chronicle, January 13, 1994, claimed that the storm dumped what seemed like tons of the stuff on Cornell. Use the rule of thumb that 12 inches of snow melts to 1 inch of water to assess the Chronicle s claim. Did the Chronicle exaggerate or understate the snowfall on the Cornell campus  

54 Optical fibers are fine threads of silica drawn from a rod of quartz, called a boule. One end of the boule is heated to its melting point and a thread of silica 0.125 mm in diameter is drawn from the melt. By careful control of the boule temperature and the drawing tension, long fibers of uniform diameter can be drawn. 

55 Optical fibers are silica threads with a protective polymer coating. Given that the silica fiber diameter is 0.125 mm and the coating is 0.050 mm thick, how many kilograms of polymer are needed to coat 26 km of fiber (Density of polymer = 1,740. kg/m. ) 

56 In the preparation of integrated circuits (chips) silicon wafers are coated with a photolithographic polymer. The wafers are 8 inches in diameter and the coating is 1,000 A thick. Each day of a five-day work week 4,000 wafers are coated. How many liters of polymer are needed to coat wafers for a year  

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Since the accuracy of experimental data is frequently not high, and since experimental data are hardly ever plentiful, it is important to reduce the available data with care using a suitable statistical method and using a model for the excess Gibbs energy which contains only a minimum of binary parameters. Rarely are experimental data of sufficient quality and quantity to justify more than three binary parameters and, all too often, the data justify no more than two such parameters. When data sources (5) or (6) or (7) are used alone, it is not possible to use a three- (or more)-parameter model without making additional arbitrary assumptions. For typical engineering calculations, therefore, it is desirable to use a two-parameter model such as UNIQUAC. 

A container full of hydrocarbons can be described in a number of ways, from a simple measurement of the dimensions of the container to a detailed compositional analysis. The most appropriate method is usually determined by what you want to do with the hydrocarbons. If for example hydrocarbon products are stored in a warehouse prior to sale the dimensions of the container are very important, and the hydrocarbon quality may be completely irrelevant for the store keeper. However, a process engineer calculating yields of oil and gas from a reservoir oil sample will require a detailed breakdown of hydrocarbon composition, i.e. what components are present and in what quantities. 

The terminal velocity in the case of fine particles is approached so quickly that in practical engineering calculations the settling is taken as a constant velocity motion and the acceleration period is neglected. Equation 7 can also be appHed to nonspherical particles if the particle size x is the equivalent Stokes diameter as deterrnined by sedimentation or elutriation methods of particle-size measurement. 

Transport Properties. Viscosity, themial conductivity, the speed of sound, and various combinations of these with other properties are called steam transport properties, which are important in engineering calculations. The speed of sound (Fig. 6) is important to choking phenomena, where the flow of steam is no longer simply related to the difference in pressure. Thermal conductivity (Fig. 7) is important to the design of heat-transfer apparatus (see HeaT-EXCHANGETECHNOLOGy). The viscosity, ie, the resistance to flow under pressure, is shown in Figure 8. The sharp declines evident in each of these properties occur at the transition from Hquid to gas phase, ie, from water to steam. The surface tension between water and steam is shown in Figure 9. 

A. Berman, l amum Engineering Calculations, formulas, and SolvedExercises, Academic Press, Inc., New York, 1992. 

Figure 2 depicts the entire process of computer-aided engineering (CAE). A part of this process is the software for computer-aided engineering, which, as shown in Figure 1, consists of modeling systems, stand-alone programs, and Hbraries of utihties for engineering calculations. 

Data compilations, the first recourse for an engineering calculation requiring physical property or parameter data, are often incomplete or do not contain data within the appropriate range of temperature or pressure (6—9). For this reason, correlation and estimation methods play an important role in apphed thermodynamics. 

It is equivalent to say that entropy of vaporization is a constant value for non-associating Hquids. Associating Hquids, eg, ammonia, water, methanol, and ethanol, do not obey the rule of Pictet and Trouton. Despite its simplicity, the Pictet-Trouton view of Hquid vaporization (19) is an exceUent example of the many rules of thumb that have been useful aids in engineering calculations for decades (5,7,8,9,21). However, proper appHcation requires an understanding of the physical reasoning behind each rule. 

CHOPEY Handbook of Chemical Engineering Calculations, Second Edition... 

Experiment diffusion coefficients are scarce and not highly accurate, especially in the liquid phase, leading to prediction methods with marginal accuracy. However, use of the v ues predicted are generally suit le for engineering calculations. At concentrations above about 10 mole percent, predicted values should be used with caution. Diffu-sivities in liquids are lO -lO times lower than those in gases. 

Blackbody Radiation Engineering calculations of thermal radiation from surfaces are best keyed to the radiation characteristics of the blackbody, or ideal radiator. The characteristic properties of a blackbody are that it absorbs all the radiation incident on its surface and that the quality and intensity of the radiation it emits are completely determined by its temperature. The total radiative fliix throughout a hemisphere from a black surface of area A and absolute temperature T is given by the Stefan-Boltzmann law ... 

Humid heat c, is the heat capacity of 1 lb of diy air and the moisture it contains. For most engineering calculations, c, = 0.24 + 0.45H, where 0.24 and 0.45 are the heat capacities of diy air and water vapor, respec tively, and both are assumed constant. 

Experimentally it has been shown that for air-water systems the value of Tj /Zc c, the psychrometric ratio, is approximately equal to 1. Under these conditions the wet-bulb temperatures and adiabatic-saturation temperatures are substantially equal and can be used interchangeably. The difference between adiabatic-saturation temperature and wet-bulb temperature increases with increasing humidity, but this effect is unimportant for most engineering calculations. An empirical formula for wet-bulb temperature determination of moist air at atmospheric pressure is presented by Liley [Jnt. J. of Mechanical Engineering Education, vol. 21, No. 2 (1993)]. 

The preceding equations, which have assumed that both the air and the water vapor benave as ideal gases, are sufficiently accurate for most engineering calculations. If it is desired to remove the restriction that water vapor oehave as an ideal gas, the aclual density ratio should be used in place of the molecular-weight ratio in Eqs. (12-5) and (12-6). 

At high velocities where turbulence dominates, the main body of flowing fluid is well mixed in the direction normal to the flow, minor differences in temperature and concentration can be neglected, and the film concept can be applied. This describes the flow as if all gradients for temperature and concentration are in a narrow film along the interface with the solid (Nernst 1904), and inside the film conduction and diffusion are the transfer mechanisms. This film concept greatly simplifies the engineering calculation of heat and mass transfer. 

Particle diameter is a primary variable important to many chemical engineering calculations, including settling, slurry flow, fluidized beds, packed reactors, and packed distillation towers. Unfortunately, this dimension is usually difficult or impossible to measure, because the particles are small or irregular. Consequently, chemical engineers have become familiar with the notion of equivalent diameter of a partiele, which is the diameter of a sphere that has a volume equal to that of the particle. 

Chopey, Nicholas P., and Tyler G. Hicks, editors. Handbook of Chemical Engineering Calculations. New York McGraw-Hill Book Co., 1984. 

This chapter provides a compendium of short engineering calculation methods and formulas for select process operations and equipment. The formulas and procedures provided in this chapter offer simple, rapid estimates of key parameters important to specifying and obtaining various engineering parameters. The information is derived from the open literature, and is believed to be accurate for obtaining better than an order of magnitude estimate for each calculation. 

When relevant monitoring data or emission measurements are not readily available, reasonable estimates of the amounts released must be made using published emission factors, material balance calculations, or engineering calculations. You may not use emission factors or calculations to estimate releases if more accurate data are available. 

If the monitoring data, mass balance, or omission factor used to estimate the release Is not specific to the toxic chemical being reported, the form should identify the estimate as based on engineering calculations or best engineering judgment. 

O - Estimate is based on other approaches such as engineering calculations (e.g., estimating volatilization using published mathematical formulas) or best engineering judgment. This would Include applying an estimated removal efficiency to a wastestream, even if the composition of the stream before treatment was fully characterized by monitoring data. 

Source Chopey, N. P. and Hicks, T G., Handbook of Chemical Engineering Calculations,... 

There are four methods dial can be used to delcrmine a chemical health hazard. These methods are emission factors, mass baliuice considerations, engineering calculations, and direct emission measnrenienls. Describe each of diese approaches. 

Engineering calculations predict emission rates without tlie use of emission factors. These calculations use basic science and engineering principles, chemical property data, and operating conditions to provide a detailed analysis of the emissions for a specific process. Tliis is a more sophisticated approach tluui emission factors, and is useful for evaluating various operational and control alteniatives. 

Direct emission measurements involve the direct measurement of emission rates from specific sources. Direct emission measurements provide tlie data for emission factor and engineering calculations. This is tlie only method tliat provides emission rates for a given source for a given set of conditions. 

Gravitational acceleration. Every body falling in a vacuum at a given position above and near the surface of the earth will have the same acceleration, g. While this acceleration varies slightly over the earth s surface due to local variations in its shape and density, it is sufficiently accurate for most engineering calculations to assume that g = 32.2 ft/s or 9.81 m/s at the surface of the earth. 

AV is the net change in elastic energy stored in a massless spring, due to extension or compression (no spring is massless, but this assumption is reasonably accurate for most engineering calculations). 

For practical engineering calculations, the minimum yield strength is usually used however, for some calculations, the average yield strength is used. 

The actual engineering calculations to determine the required volumetric flowrate and various pressure calculations will be discussed later in this section. 

Pertinent engineering calculations can be made for air and gas drilling operations and for unstable foam drilling operations. 

Thus the primary compressors will have sufficient pressure capability to drill the interval from 8,500 to 10,000 ft. A third primary compressor should be on site and hooked up for immediate service in the event of downhole problems or the necessity to shut down one of the operating compressors. Also, the booster should be hooked up for immediate service in the event of downhole problems. For more information and engineering calculations pertaining to compressors and boosters see reference 64. 

Once the performance and environmental conditions have been defined, the selection of a suitable material can be made, and this in turn can be followed, if necessary, with the necessary engineering calculations to establish strength requirements. The basic data needed for calculations have to be collected and have to pertain to the specific grade of the selected material. The pertinent information required for making determinations for longevity of the product and obtaining a general concept of the character and behavior of the selected material should be supplied by the manufacturer of the raw material and/or obtained in-house or via a contractor. 

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