Units and Their Conversion

Table A2 Some common non-SI units and their conversion factors...

Table 2-4 Magnetic systems of units and their conversions...

In fluid mechanics, most often we deal with dimensioned quantities, such as 12ft/s( = 3.66m/s), rather than with pure numbers, such as 12 or 3.66. To become competent at sblving fluid mechanics problems, you must become virtually infallible in the handling of such units and their conversion factors. For most engineers the major sources of difficulties with units and conversion factors are carelessness and the simultaneous appearance of force and mass in the same equation. j... 

Pressure together with temperature, flow rate, and concentration are the essential macroscopic properties required to operate chemical processes. Various units are frequently used to report pressure and some common units and their conversions are reported in Table 4.2. 

TABLE 4.2 Common Pressure Units and Their Conversions... 

Mullin, J.W. (1973) Solution concentration and supersaturation units and their conversion factors. The Chemical Engineer, No. 274, 316-317. 

A variety of units for P have been used by different investigators. Some of these units and their conversion factors are listed in Table 61.1. 

Solving problems requires practice. You can solve many of the problems in this book by paying close attention to units and their conversions (as outlined in Section 2.6). However, sometimes getting started is difficult. How do you interpret a written problem and get started solving it Many (but not all) problems can be solved with the following strategy ... 

The mostly used units and their conversion factors are listed in Table B. 

Table A1.3 Non-SI units and their factors for conversion to the SI system...

Conductivity of a solution is usually expressed as pmhos/cm. The SI units for conductivity and their conversion are as follows ... 

Many of the difficulties in converting units between different systems are associated either with the electromagnetic units, or with atomic units and their relationship to the electromagnetic units. In sections 7.3 and 7.4 the relations involving electromagnetic and atomic units are developed in greater detail to provide a background for the conversion factors presented in the table in section 7.2. 

The first thing you need in order to convert between units is the equivalence between the units you want and the units you have. To do this use a conversion table. See w Conversion of units for a fairly extensive (but not exhaustive) list of common units and their equivalences. 

Table 5.1 summarizes the relationship of commonly used corrosion rate units and their expressions. The conversion factors are given in Table 5.2 and Table 5.3 [16]. The current density equivalent to a corrosion rate of 1 g/m day is given in Table 5.4 [16].

When using measured quantities, you often have to convert a quantity expressed in one unit into another unit. You probably make simple conversions between commonly used units every day. For example, you might have converted 2 feet to 24 inches, or 1.5 hours to 90 minutes. To perform these calculations, you need to know the numerical relationships between units. For example, to convert feet to inches, you must know that 12 inches = 1 foot. To convert hours to minutes, you must know that 60 minutes = 1 hour. Table 2-3 shows some common units and their equivalents in other units. 

Careful tracking of units and their cancellation can be a valuable tool in checking your work. If we had accidentally used the reciprocal of one of the conversion factors, the resulting units would have been something other than meters. Unexpected or nonsensical units can reveal an error in your problem-solving strategy. 

Faust R, Weber Ch (1997) One-step synthesis of dialkynyl-l,2-diones and their conversion to fused pyrazines bearing enediyne units. Tetrahedron 53(43) 14655-14670. doi 10.1016/S0040-4020(97)01007-7... 

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