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By R. W. Raymond

The death of Mr. Stetefeldt, which occurred at Oakland, Cal., March 17, 1896, was a surprise, as well as a sorrow, to many of his friends and professional colleagues. In the Engineering and Mining Journal of March 28th, I published an obituary article, the substance of which, modified and enlarged by later information, forms the basis of the present biographical notice. I am indebted to Mr. Albert Arents, Alameda, Cal., and Mr. 0. H. Hahn, Monterey, Mex., life-long friends, and to Miss Pauline Anacker, of Gotha, Germany, a cousin of the deceased, for details which I could not have obtained elsewhere. Carl August Stetefeldt was born September 28, 1838, in the village of Holzhausen, in the duchy of Gotha, Germany, where his father was a Lutheran pastor. He was an only son, and (after the early death of a sister) an only child. In his boyhood he is reported to have been physically delicate, but mentally precocious. In 1847 his father was transferred to Hörselgau, near Waltershausen, where, besides discharging his pastoral duties, he kept a select private boarding-school, in which a few pupils received a training preliminary to the " gymnasial" course. Among these pupils (one of whom was the now famous Dr. Knorr, the discoverer of antipyrine) he included his own son, who, thus carefully prepared, entered in 1852, at the age of fourteen, the gymnasium at Gotha. The records of the gymnasium bear witness that his conduct in and out of school was " blameless," and his attention to study good." But his career as a "gymnasiast" was marked by an act of rebellion probably more startling then than it would be now. Being much more strongly attracted by the natural sciences than by the dead languages, he conceived a special aversion to Hebrew, and engaged in a conflict with the professor in that department, out of which he seems to have come victorious. At all events, he was not obliged to pursue further

Jan 1, 1897

By Harry H. Nowlan

A heavy development campaign progressed during the year 1936 in South Texas1, following up important discoveries made in 1935. Oil and gas wells completed during the year were 1473 against 704 in 1935. The drilling program reached its peak of operations in June in consequence of offset requirements made necessary principally in Duval County in the Seven Sisters, Loma Novio, Lopez and Cole fields. There were six new fields discovered during 1936 as follows: Rhode in McMullen County; Peters, El Mesquite and North Kohler in Duval County; Wood in Starr County and Colorado in Jim Hogg County. No discovery of unusual consequence was made during the year. The pools mentioned above are simply in the primary stages of development. The most intensive exploratory work during the year was in Duval, Webb and Zapata Counties. Considerable activity also prevailed in Starr and Brooks Counties. Much significance is attached to the California Company's discovery in the Alta Mesa field in Brooks County, which is considered to be a deep-seated salt dome. The Comitas field, in Zapata County, developed some surprisingly good production in a shallow sand at 900 ft. and is being followed by a heavy wildcat campaign throughout that area in search of like production. In Starr County an active wildcat campaign is in progress in a continued effort to find new fields northwest of the Sam Fordyce field, in Hidalgo County. This play continues in a northerly direction through Starr and Jim Hogg Counties. New Fields Rhode.—The Rhode field, in southeastern McMullen County, was opened in May by the Magnolia Petroleum Co. with a gas well in the Whitsett (Upper Jackson) sand at a depth of 1810 to 1822 ft., this test is located in the southeast corner of sec. 86 on the Rhode ranch. Four gas wells have been completed, proving up a gas area of 1000 acres, more or less. Development will be slow because of lack of market for the gas.

Jan 1, 1937

By D. C. Anderson

Utah Construction & Mining Co.'s Lucky Mc mine is one of the major uranium producers in the United States. It is located near the geographic center of Wyoming in Fremont County. The climate is middle-latitude steppe, with an average annual precipitation amount of 10 in.; the temperature varies from 40º below zero to 100º above. The land surface is moundlike, rolling terrain, with sparse grass and sagebrush. The northern slopes of the higher ridges support a scattering of juniper and pi[n]ion growth. DISCOVERY The discovery was made by Neil E. McNeice, of Riverton, Wyo., on Sept. 13, 1953. After prospecting the area and staking a few claims, McNeice reported his findings to geologists of the Atomic Energy Commission (AEC), who immediately began preliminary studies of the numerous surface uranium exposures of the district. The discovery received widespread publicity, resulting in an intensive search for uranium throughout the region ; thousands of claims were staked. The AEC drilled several shallow holes near the discovery outcrop. Assays of cuttings from these holes confirmed the presence of a low-grade, oxidized uranium deposit. McNeice and his partner, L. A. Morfeld, tried to start a mining operation but were plagued by a lack of capital and technical know-how. They sought assistance from a Salt-Lake-City-based mining firm, the New Park Mining Co., engaged in underground base-metal mining in the Park City district of Utah. After a period of negotiations, New Park initiated activities that led to the forming of the original Lucky Mc Uranium Corp. The company started limited development drilling and mining operations in the summer of 1954, with the first ore production being shipped by truck to the Vitro mill in Salt Lake City. The mining

Jan 1, 1969

By V. P. Yashin

Modern trends in the use of autogenous grinding of minerals have been investigated by Mekhanobr Institute. The conclusions drawn are based on experimental and theoretical investigations by the author and his coworkers. A method is suggested for determining the efficiency of converting from ball milling to autogenous grinding. A qualitative interpretation is given for comminution theory using both methods. This interpretation is used as a basis for considering both the principal trends in increasing use of primary autogenous grinding and the results of such in industrial application. Data are given from testing some ores from USSR deposits for the effect of the ore Preparation step on subsequent metallurgical treatment. Autogenous grinding is shown to be widely used in various USSR industries.

Jan 1, 1980

By W. N. Logan

A survey of geological conditions, production and prices in Indiana oil fields. Shows no production and indefinite prospects from the sub-Trenton formation; good production and much untested territory in Trenton formation; and fair production from the Pennsylvanian with fair prospects for the future in both the Pennsylvanian and Mississip-pian formations. THE petroleum industry of Indiana made somewhat notable progress during the year 1923, considering the number of handicaps it encountered. The price of labor and materials continued to have an upward slant while the price of crude oil took a decidedly downward course. In spite of these adverse conditions, the quantity production will closely approximate that of 1922, when it passed the million-barrel mark. The progress of the industry in Indiana should be considered fairly satisfactory as long as the present production is maintained. In other words, if the loss of production from the waning old wells can be offset by the production from the new for a period of 10 or 15 years longer, the industry may have cause for congratulation.

Jan 3, 1924

By John A. Wolfe, James A. Niederjohn

Applications of mathematical statistics to the field of exploration are still relatively new. There are two primary reasons why little has been published in this field. First, if one discovers an effective technique for exploration, he does not like to disclose it. Second, the geologist needs to work closely with a mathematical statistician, and the communications barrier between the disciplines is formidable. The authors, one a geologist and the other a statistician, were interested in the economic benefit which appeared to be possible in the inter-disciplinary area they call "geostatistics."

Jan 11, 1962

By H. J. Beattie, G. C. Gould

J. B. Seabrook' recently published properties of a low-alloy Ni-A1 age-hardening steel known commercially as "Nitralloy-N". He mentioned three possible mechanisms of age hardening, viz. order-disorder in the matrix, order -disorder in a precipitate, and a precipitate that goes in and out of solution reversibly without losing coherency. The following results indicate that the last - mentioned of these mechanisms is the cause of age hardening in Nitralloy-N. The reversibility of the age hardening with a sub-critical solution temperature was demonstrated strikingly by Seabrook, whose results are reproduced in Fig. 1. Aging for 22 hr at 975°F (525°C) can reharden the fully-tempered martensite to its original as-quenched hardness of R, 45. A Nitralloy steel was obtained from Seabrook' with the following analysis:

Jan 1, 1962

By C. R. McClure

The objective of this papef is to summarize briefly the practical use of rock mechanics in design and construction of various types of structures. These range from foundation for industrial facilities, nuclear power plants, bridges and dams to tunnels and underground caverns. The use of rock mechanics has varied from performing a few laboratory unconfined compressive tests on core samples to complete field and laboratory tests for underground power caverns. The primary difference between the rock mechanics studies we hare for construction projects and those most commonly found in the literature is that our tests must provide immediate answers to specific questions facing a design or construction engineer. For example, when we make a plate-bearing test we arrive at a load-deformation relationship. We realize that this is not a true modulus of elasticity. Yet, when considering the resistance the rock will provide against forces occurring in a pressure tunnel it is a far more useful value than the true modulus of elasticity of the rock. Another example of this difference in interest is in the use of flat jacks. Many people criticize the use of flat jacks because they measure the stresses in the disturbed zone very near the surface and do not represent the undisturbed stress condition in the rock. However, in actual construction it is frequently those near-surface stresses with which we must cope. We are interested in both the stress conditions present prior to excavation and those as modified by construction of an exploratory adit or drift. Fundamentally, we are interested in the practical application of rock mechanics in the solution of problems of design and construction of civil engineering works.

Jan 1, 1968

By Oswald J. Heinrich

THIS question having been repeatedly raised, and particularly revived in a discussion at the last meeting of the Institute, I beg to submit the following remarks, based partly upon personal experience, partly upon the results of large works in Europe, establishing, years ago, the practicability of certain methods, which may therefore be considered to have passed the stage of mere experiment. Before entering upon the merits of one system or the other, it is indispensable to lay down some recognized principles, which ought to serve as guides, in arriving at fair judgments in questions of this character. In a profession like that of mining, locally so much influenced by combinations of circumstances too various to mention, it is difficult to do more than lay down the main features of a system based upon general laws and recognized facts, leaving the details to the sound judgment and experience of the engineer, who, by virtue of his education, ought to be able to make such choice and such modifications in the plans of a mine as the particular case demands. Mineral resources, in some countries the sole property of the owner of the soil, in others controlled by the strong hand of a government, are nevertheless a gift of nature, in which, indirectly, the whole of the human race has as real an interest as the immediate owner himself. This interest requires, at least, that no unnecessary waste of

Jan 1, 1874

By Cyril Smith

THE method of thermal analysis, so important in the development of metallographic science, has of recent years been falling into disuse owing to the development of other physical methods which give results easier of interpretation and which can be used for the study of either equilibrium or transitional conditions because they do not require a continuously changing temperature. Nevertheless thermal analysis remains useful in the study of reactions that take place rapidly, and the simplicity of the experimental technique and the general availability of the apparatus involved are points in its favor. Theoretically, thermal analysis is capable of giving specific and latent heat measurements and therefore should permit the study of reactions on a more fundamental basis than any other method. It is, however, difficult or impossible to obtain quantitative heat measurements from cooling curves obtained in the usual way. Even if the furnace containing the sample is cooled or heated at a linear rate, or if a gradient furnace is employed to maintain a constant rate over a large range of tempera-ture, the heat flow from or to the specimen depends on its previous his-tory, for the difference of temperature between the specimen and its surroundings varies. The emissivity of the specimen surface, moreover, is unlikely to be constant. The able mathematical analysis by Russell,1 although it prevents misinterpretation of data, has an effect rather the reverse of that intended, and leaves the reader doubtful of the possibility of ever obtaining quantitative results from thermal curves. Nothing can be done to apply thermal analysis to the study of equilib-rium conditions of reactions that are not completed at rates of tempera-ture change below about 1° C. per minute, and this unfortunately excludes most solid transformations in alloys. ? For the determination of liquidus

Jan 1, 1939

By E. B. Thornhill

In this paper on the recovery of mercury as sulphide, from the residues from the amalgamation and cyanide treatment of high-grade ores and concentrates, I will not discuss the many reactions, chemical and other- wise, that take place in the general process, but confine myself more particularly to the methods of recovering the mercury. I submit charts of two amalgamation-barrel charges, Figs. 1 and 2, which are self-explanatory. The flow sheet of the high-grade and the mercury extraction plants is showh in Fig. 3.

Jan 1, 1916

By W. L. Watts

The existence of petroleum in California has been known for many years. From time immemorial the California Indians used this mineral, in the form of asphaltum, for various purposes. In the early history of the State the Catholic fathers utilized it for roofing their missions and other buildings. It is said that in 1855 or 1856 Andreas Pico distilled petroleum on a small scale for the San Fernando Mission. He obtained his crude oil from Pico canon, near Newhall, in Los Angeles county; and he was probably the first refiner of petroleum in this State. In 1856 a company commenced work at the La Brea ranch, in Los Angeles county, and tried to refine the crude oil. In 1857 an attempt was made to produce illuminating-oil from crude petroleum at Carpenteria, in Santa Barbara county; and there are records of similar attempts in other localities previous to 1860; but none of them were successful. The first scientific report on petroleum in California was made by Prof. B. Silliman, who published his researches in 1865. He spoke favorably of the possibility of obtaining petroleum in remunerative quantities in this State, and gave the results of his experiments in the fractional distillation of California petroleum. The next decade was marked by a considerable oil-excitement in California; and a great many companies mere formed for the purpose of petroleum-mining and for distilling crude oil. In most instances these companies did not meet with success; but it must be remembered that the pioneer oil-miners did not

Jan 1, 1900

By Walter S. Weeks

THE subject of the flow of air through a mine under the influence of natural ventilation has proved an elusive one. To my knowledge only cut and try algebraic solutions have been used where multiple paths are involved. The object of this paper is to present a method for the graphical determination of the flow induced by the natural ventilation pressure (N.V.P.) alone or in combination with a fan. The N.V.P., measured in pounds per square foot, induced by two columns of air between two horizontal planes at different elevations, is equal to the difference in weight of the two columns, assuming each to have a cross-sectional area of 1 sq. ft. Pressure in pounds per square foot is converted into inches of water by dividing by 5.19. Methods of calculating the N.V.P. have been discussed in the literature. In this paper, for simplification of exposition, the change in pressure due to the weight of superimposed air will be assumed directly proportional to the length of the column. The actual methods of calculating the N.V.P. do not affect the solutions to be presented. It must be realized that the precision to be obtained from the small- scale, inked diagrams presented is not as great as would be obtained from large-scale, penciled curves that would be used in practice. The accuracy of the curves does not warrant reading "volumes" closer than the nearest thousand cubic feet per minute. CASE I. DUCTS IN SERIES The simplest type of problem is to determine the flow when two shafts are connected by a crosscut, as shown in Fig. 1. In this example, the resistance of the shafts is to be taken as 0.0001 in. of water for a flow of 1000 cu. ft. per minute for a length of 1000 ft. The resistance of a crosscut is to be taken as 0.0005 in. of water for a flow of 1000 cu. ft. per minute. The small pressures necessary to cause changes in velocity will not be considered, because the accuracy of other obtainable data does not warrant their consideration.

Jan 1, 1938

By P. J. Root, J. E. Warren

An idealized model has been developed for the purpose of studying the characteristic behavior of a permeable medium which contains regions which contribute significantly to the pore volume of the system but contribute negligibly to the flow capacity; e.g., a naturally fractured or vugular reservoir. Unsteady-state flow in this model reservoir has been investigated analytically. The pressure build-up performance has been examined in some detail; and, a technique for analyzing the build-up data to evaluate the desired parameters has been suggested. The use of this approach in the interpretation of field data has been discussed. As a result of this study, the following general conclusions can be drawn: 1. Two parameters are sufficient to characterize the deviation of the behavior of a medium with "double porositym from that of a homogeneously porous medium. 2. These parameters can be evaluated by the proper analysis of pressure build-up data obtained from adequately designed tests. 3. Since the build-up curve associated with this type of porous system is similar to that obtained from a stratified reservoir, an unambiguous interpretation is not possible without additional information. 4. Differencing methods which utilize pressure data from the final stages of a build-up test should be used with extreme caution. INTRODUCTION In order to plan a sound exploitation program or a successful secondary-recovery project, sufficient reliable information concerning the nature of the reservoir-fluid system must be available. Since it is evident that an adequate description of the reservoir rock is necessary if this condition is to be fulfilled, the present investigation was undertaken for the purpose of improving the fluid-flow characterization, based on normally available data, of a particular porous medium. DISCUSSION OF THE PROBLEM For many years it was widely assumed that, for the purpose of making engineering studies, two param- eters were sufficient to describe the single-phase flow properties of a producing formation, i.e., the absolute permeability and the effective porosity. It later became evident that the concept of directional permeability was of more than academic interest; consequently, the degree of permeability anisotropy and the orientation of the principal axes of permeability were accepted as basic parameters governing reservoir performance. 1,2 More recently, 3-6 it was recognized that at least one additional parameter was required to depict the behavior of a porous system containing regions which contributed significantly to the pore volume but contributed negligibly to the flow capacity. Microscopically, these regions could be "dead-end" or "storage" pores or, macroscopi-cally, they could be discrete volumes of low-permeability matrix rock combined with natural fissures in a reservoir. It is obvious that some provision for the inclusion of all the indicated parameters, as well as their spatial variations, must be made if a truly useful, conceptual model of a reservoir is to be developed. A dichotomy of the internal voids of reservoir rocks has been suggested.7,8 These two classes of porosity can be described as follows: a. Primary porosity is intergranular and controlled by deposition and lithification. It is highly interconnected and usually can be correlated with permeability since it is largely dependent on the geometry, size distribution and spatial distribution of the grains. The void systems of sands, sandstones and oolitic limestones are typical of this type. b. Secondary porosity is foramenular and is controlled by fracturing, jointing and/or solution in circulating water although it may be modified by infilling as a result of precipitation. It is not highly interconnected and usually cannot be correlated with permeability. Solution channels or vugular voids developed during weathering or burial in sedimentary basins are indigenous to carbonate rocks such as limestones or dolomites. Joints or fissures which occur in massive, extensive formations composed of shale, siltstone, schist, limestone or dolomite are generally vertical, and they are ascribed to tensional failure during mechanical deformation (the permeability associated with this type of void system is often anisotropic). Shrinkage cracks are the result

By E. P. Pfleide, L. W. Gibbs. J. R. Gross

A method using computer techniques is described for the comparative evaluation of truck performance over any given haul road using readily obtainable manufacturers' data. An additional computer program is utilized to calculate individual cycle times for each truck and shovel combination, fleet requirements for any desired production rate, and to estimate comparative costs. The introduction of a large number of variables into the program permits management to determine the critical system factors having the greatest bearing on costs. Thus, the method described can be used not only for analysis of needs for a new surface mine but for cost improvement in existing mines where changes in truck and shovel operations are contemplated. The systems analysis approach to the solution of problems in the mining industry is gaining in industry acceptance. This is a logical development in view of the fact that a mine constitutes one of the most dynamic systems of production. In contrast with a manufacturing plant, situated in a location selected through choice and utilizing a regulated source of quality controlled raw materials, the miner must go where the ore is and he is faced with ever changing physical conditions. He is subjected to the vagaries of nature, and he can never mine the same ore twice. What is systems engineering? There seems to be no concise and universally accepted definition of the term and its meaning is still fairly local. It deals largely with trade-offs of subsystem characteristics to achieve some desired result in an overall system. This concept of suboptimization can be explained by an example. If the objective of a mining company is to produce a certain quality ore at minimum cost, the optimum operation is not achieved by minimizing all costs, since all phases of mining are interrelated. Reduction of blasting costs might well increase loading, hauling, and crushing costs out of proportion to the resulting saving in explosives. Hence tradeoffs are necessary. It is evident then that an optimum system is achieved through a blending of suboptimal components which taken together yield the desired result. OBJECTIVE For our mathematical model we will assume the existence of a hypothetical new organization called Taconite Mining Co. (TMC). TMC has made an analysis of their orebody, their proposed operation, and

Jan 1, 1968

By I. Iwasaki, K. Adam

The oxidation behaviors of simple and complex chloride systems of copper, iron, nickel, cobalt, and manganese in a stream of oxygen were investigated using a thermogravimetric analysis technique. Their reaction mechanisms are discussed from stoichiometry, thermodynamic feasibility, and X-ray diffraction analysis of reaction products. The results are used to determine an optimum operating temperature of the selective oxidation step in a chlorination process for producing nonferrous metal chlorides, elemental sulfur, and ferric oxide from copper-nickel sulfide flotation concentrates.

Jan 1, 1985

By Richard B. Greenwalt

INTRODUCTION Direct reduction of iron ores has unquestionably become established as an important step in the worldwide steelmaking industry. The history of this development has been long and fraught with difficulty. In 1800, Champlain suggested the direct reduction concept using carbon and a shallow hearth vessel. Roughly 100 years later, Jones attempted a commercial process using carbon and producer gas in a rotary kiln. During the early years of this century, numerous attempts were made to start commercial direct reduction plants using such processes as Hoganas, Wiberg, Krupp-Renn, and others. Most of these were short lived, being abandoned due to a variety of technical and economical factors. Today, however, a new generation of direct reduction processes has emerged. We enter 1977 with at least 40 commercial plants in operation using 15 processes in 14 countries. These plants have combined total annual capacity of roughly 10 million tonnes of direct reduced product. Many articles have been written, and projections made, concerning the future growth potential for direct reduction. As is al- ways the case with projections, the numbers vary, but the outlook does not. Anyone who participated in the years of effort that have gone into this field of endeavor should be excited and justly rewarded by noting the shape of the curve in Figure 1.

Jan 1, 1977

By Arthur Knapp

The petroleum industry is confronted with the problem of conservalion. This is not a simple problem in view of a wide difference of opinion among authorities as to whether conservation is necessary and the specific direction that it should take. Many writers accuse the petroleum industry of wasting the natural resources of the country. Others link the consuming public with the industry in this waste. Let us define our terms; agree, if possible, on where and when waste occurs in connection with either the recovery or use of petroleum and select such plans for conservation as appear most practical. A plan for conserv3tion which appears to be logical today may not meet the problem tomorrow. The conservation of petroleum is closely linked with the advancement of marly arts and sciences and as these advance, the plan of conservation has to change. The need for conservation does not necessarily rest upon the elimination of waste. There is not necessarily a fixed connection between waste and conservation. Conservation may be necessary or desirable although there is no waste. Definitions Waste: Useless or unnecessary expenditure. Conservation: The preservation of the natural resources for economical use. Both definitions contain adjectives the interpretation of which is extremely difficult. It is the determination of what expenditures are "unnecessary" or what uses are "economical" that will require study and agreement. If one lets his automobile engine run in cold weather in order to keep it hot, it is difficult to measure that necessity. If an automobile is driven two blocks, when the driver is physically capable of walking, what is the measure of necessity. This question is in the realm of one of the oldest of sociological problems, "What is a luxury?"—a problem which has not been solved. The history of society indicates that the measure of a man's wealth has been the measure of necessity. What he can afford to buy without stinting himself in some other direction, is not a luxury to him and, if it fulfills his desires, may be considered his necessity.

Jan 1, 1927

By John Birkinbine

The early history of the mining and metallurgical industries of Pennsylvania is so intimately associated with the section of the State in which we meet, that a brief resume of a few of the important historical facts, and a reference to some of the more modern enterprises, in which members of the Institute have been largely concerned, seem appropriate to this occasion. It is just two hundred years since the publication of the earliest mention of the manufacture of iron in Pennsylvania. What kind of iron this was, or where or by whom it was produced, is uncertain. The only record of it is the following verse, quoted in the admirable work of Mr. James M. Swank,* from a poem published in 1692: " A certain place here is, where some begun To try some Mettle, and have made it run, Wherein was Iron absolutely found, At once was known about some Forty Pound." One who stood one hundred and seventy years ago on the summit of this Neversink Mountain † (had the atmospheric conditions been favorable, and the timber somewhat removed) might have noticed in the daytime the smoke, or at night the reflection, from the fires of the first successful Pennsylvania iron enterprises, scarcely 15 miles to the south, viz.: Rutter's bloomary forge, built in 1716, and the Colebrookdale blast-furnace erected in 1720, respectively 3 and 8 miles distant from Pottstown. Here the pioneers of iron production in the State which has so long led, and still leads all others in this manufacture, had their trials and successes ; and it may be a satisfaction to some who bewail a present depression in trade, and the low prices now ruling, to recall the fact that in 1731 pig-iron is reported to have been sold ''in large quantities" at the Colebrook-

Jan 1, 1893

By Walter S. Weeks, Vitaly S. Grishkevich

Considerable difference of opinion seems to exist as to whether the rate of air flow when a fan is placed on a given duct should be determined by the use of static pressure or total pressure characteristics. A little study will show that both methods are correct. Assume that a fan is connected to a duct by an expansion piece as shown in Fig. 1, and that steady flow is established. Considering the atmospheric pressure as zero pressure, let the static head at the outlet of the fan be h and the velocity at this point be vl. The total head at the outlet is then h + „"• The total head at this point must be equal to the total head at the end of the duct plus the losses that have occurred between the two points. Left be the friction loss in the straight duct, s the shock loss in the dif- fuser, and v2 the velocity at the end of the duct. Then ig. 1.—Fan on duct. A curve showing the value of the left-hand side of the equation for different rates of flow is the total pressure characteristic of the fan, while a curve showing the value of the right-hand side is the total pressure characteristic of the duct. If these two curves are plotted on the same chart, the intersection indicates the rate of flow when steady flow is established. We may look at this problem in another way. The static pressure at the outlet of the fan is the static pressure of the fan and it is also the static resistance of the duct from that point to the end. The friction in the straight duct is f. If the duct were the same area as the fan outlet, would be the static resistance of the whole duct system. In the present case, however, this resistance is decreased by the change of velocity head into static head in the expansion piece. If conversion were perfect, the static pressure recovered would be

Jan 1, 1931