English system

The density of a substance is its weight per unit of volume. The unit of volume in the English system of measurement is 1 cubic foot or 1 f. To find the density of a substance, you must know its weight and volume. You then divide its weight by its volume to find the weight per unit volume. 

The English system of units is complicated compared to the metric system. In the English system, the units of mass are pounds-mass (Ibm) and the units of weight are pounds-force (Ibf). By definition, a weight (i.e., force) of one Ibf equals the force produced by one Ibm under the acceleration of gravity. Therefore, the constant, g, which has the same numerical value as g (32.17) and units of Ibm-ft/lbf-sec, is used in the definition of weight ... 

The constant of proportionality in the English system of units, g, which causes one pound of mass produces one pound of force under the acceleration of gravity, equal to 32.17 Ibm-ft/lbf-sec. ... 

The unit of land measure in the English system is the acre, while that in the metric system is the hectare. An acre is 4.356 X 104 ft2. A hectare is ten thousand square meters. The town of Willington in Connecticut requires a minimum area of 2.0 acres of land for a single-family dwelling. How many hectares are required ... 

A lap in most tracks that use the English system is 0.25 mi (English lap). In countries that use the metric system, a metric lap is 0.50 km. A champion marathon runner covers a mile in about 5.0 min. How many minutes will the runner take to run an English lap at that speed A metric lap ... 

The metric system was designed to make calculations easier than using the English system in the following ways ... 

Beginning students often regard the metric system as difficult because it is new to them and because they think they must learn all the English-metric conversion factors (Table 2-3). Engineers do have to work in both systems in the United States, but scientists generally do not work in the English system at all. Once you familiarize yourself with the metric system, it is much easier to work with than the English system is. 

Sometimes it is necessary to convert from a measurement in the English system to a measurement in the SI system. (The English system is sometimes referred to as the U.S. Customary system of units.) There are numerous SI/English conversions. Consult your book and check with your instructor to see which they recommend. We will be using the following in many of our examples ... 

The system of units used in chemistry is the SI system (Systeme International), which is related to the metric system. There are base units for length, mass, etc. and decimal prefixes that modify the base unit. Since most of us do not tend to think in these units, it is important to be able to convert back and forth from the English system to the SI system. These three conversions are useful ones, although knowing the others might allow you to simplify your calculations ... 

In the English system the depth of the coke in the generator is considerable, consequently the carbon dioxide formed at the base of the fire tends to be reduced in the upper part of the fire by the hot coke, in accordance with equation (2), therefore in the English system during the air blast a combustible gas is produced. 

Meter a unit of measurement of length in the metric system. One meter equals approximately 39.37 inches in the English system. 

Specific gravity appears to be nondimensional since the units of the density of the liquid are the same as the units of the density of water however, this is not strictly true. Actually, in the English system the units are... 

In the cgs system, power has the units of ergs per second in the mks system, units of joules per second lor watts) and in the English system, units of foot-pounds per second. A common engineering unit is the horsepower, defined as 550 foot-pounds per second or 33.000 footpounds per minute. The SI unit of power is the wall. I watt = I joule per second. < I joule is the work done by I newton acting through a distance of I meler.l I joule = watt-second = I07 ergs= I07 dyne-centimeters. The SI unil of force is the newton. (I newton = 10s dynes). See also entry on Units and Standards. 

The example just given illustrates how. on a macroscopic scale, heat can he considered a form of energy. Regardless of the material involved, any amount of heat absorbed or released may be quantitatively expressed as an amount of energy. A grum-calorie or heal is equivalent to 4.19 joules, and in the English system, a British thermal unit (Btu) is equivalent to 778 foot-pounds. 

With the selection of water as the standard with cp = I. the left side of Equation (2) clearly becomes of unil value when m and (/ - t,) are each of unit value. In Ihe English system, we accordingly have the British thermal-unit (or Btu) as the heat required lo warm I pound of pure water through an interval of I E. In the metric system, the corresponding unit is the calorie. Ihe heat required to warm 1 gram of water l°C. A large unit or kilocalorie corresponding to 1.000 ordinary calorics is also frequently used in scientific work. 

Calorie or Calory. In metric system it is the heat required to raise the temp of lg of water from t° (such as 15,18 or 20°) to (t+l)°. This is called "small or "gram-calorie (abbr cal). There is also "large or "kilogram-calorie (abr Cal or kcal) which is equal to lOOOcals. In English system, the so- called BTU or btu (British Thermal Unit), is the heat required to raise the temp of lib of w from 39.1 to 40.1°F. One BTU is equal to 0.252kcal... 

Figure 44-2. Thermodynamic properties of water Irom 0 to 375 C (English system)...

All systems of measurement / V I are based on arbitrary standards. The SI system is as arbitrary as the English system, but the relationship of one unit to another is more systematic and easier to remember in the metric system. 

John Guy Feggis Francis, English systems engineer, Oct. 10, 1934 -... 

English system measurements into metric equivalents quickly enlightens the instructor to the abhorrence that the non-scientist has towards mathematical manipulations. No prior knowledge of scientific principles can be assumed. In our opinion, those subjects which have not been found to be easily integrated with chemical and biological principles are best omitted from the first course of study. Hence, forensic photography, the polygraph, document examination and speed detection devices are topics that are not included in the curriculum. 

This system of units is the English-system equivalent of SI. Thus,... 

Water hardness was important long before modern methods of measuring it were established and for this reason it is reported in rather parochial ways. Thus the English system records it as grains of calcium carbonate per litre, and this Medieval unit of weight is 65 mg. The Ameri-... 

The metric system is the system of choice for chemistry, as well as for other physical sciences such as physics and astronomy. You may not feel comfortable with this system, but two aspects of its usage should relieve your concerns. First, the most troublesome mathematical manipulation, changing back and forth between the metric system and the English system (pounds, miles, gallons, and so on), is rarely required and is not included here. Second, less frequently used metric units, such as decimeters, need not be part of what you need to learn. 

The units of specific impulse are seconds. There is some confusion with respect to these units when the English system is used. As stated above the specific impulse is defined as the thrust divided by the weight flow rate ... 

In all of the equations written here, the energy unit is presumed to be the joule, in accord with the SI system of units. For the English system of units, the kinetic- and potential-energy terms, wherever they appear, require division by the dimensional constant gc (see Secs. 1.3 and 1.8). However, in many applications, the kinetic- and potential-energy terms are omitted, because they are negligible compared with oth r terms. Exceptions are applications to nozzles, metering devices, wind tunnels, and hydroelectric power stations. 

In the English system of units heat flow is expressed in British thermal units per hour (Btu/h), area in square feet, and temperature in degrees Fahrenheit. Thermal conductivity will then have units of Btu/h ft °F. 

In the SI system a typical set of units for the parameters would be p. in kilograms per second per meter, cp in kilojoules per kilogram per Celsius degree, and k in kilowatts per meter per Celsius degree. In the English system one would typically employ p. in pound mass per hour per foot, cp in Btu per pound mass per Fahrenheit degree, and k in Btu per hour per foot per Fahrenheit degree. 

In these equations q is the heat flux per unit area and will have the units of watts per square meter (W/m2) in SI units or British thermal units per hour per square foot (Btu/h ft2) in the English system. 

The common unit of measurement for natural gas is the standard cubic foot in the English system and the standard cubic meter in the metric system. Each of these standards is expressed at pressures and temperatures commonly used as standard to the system in the geographical area of concern. In the United States, where standards frequently vary from state to state, the cubic foot is frequently expressed in the English system at standard conditions of 14.73 pounds per square inch absolute (psia) and 60 degrees Fahrenheit (60°F), although there are a number... 

Another common unit of measurement for natural gas is by use of its heating value, expressed in British thermal units (BTU) per standard cubic foot in the English system, and in Joules (or calories) per unit volume in the metric system. Commercially used natural gas, after processing, yields the equivalent of about 950-1050 BTU/ft3. Also used as a unit of measurement is the therm, equivalent to 100,000 BTU, or the nominal heat content of 100 standard cubic feet of lean, processed natural gas. 

The most common unit of measurement in the English system is the mcf or thousand (103) cubic feet. Larger volumes, used to express production or pipeline volumes, are noted as bcf, or billion (109) cubic feet. Even larger volumes, such as reserve figures, usually are expressed as tcf, or trillion (1012) cubic feet. 

In the literature, information is found using different systems of units metric, SI, and the English system. Quotations from the literature are presented in their original form. It would be difficult to change all these units in the book to one system. To assist the reader in converting these units, an appendix is provided with conversion factors for all units found in the text. 

FPS. The system of units based on the fundamental units of the English system foot, pound and second. 

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