Pulsating combustion

Book Reviews In our test at a heat flux of 25,000 B.Th.U./(hr)(ft)z, types 1 and 4 flow averaged 1.05 cm/set while type 2 flow averaged 0.3 cm/set. Transient dynamic effects due to the necessity of establishing flow where no flow existed were short-lived and in no case were visible more than 0.8 set after the strip was suddenly heated. There is also an apparent close similarity between the phenomenon shown and the development of thermal updrafts

P. VALLET: Tables Num&iques permettant l’Int&ration des Con&antes de Vitesse par rapport g la Temphture. GauthierVillars, Paris, 1961. (paperbound). 114 pp. $2.50. MANY chemical processes can be characterized by a rate equation --du/dt = kf(x)where x is the fraction unconverted, t the time, f (x) some function of x that does not depend on temperature, and k a rate constant, i.e. a function of temperature only : k(T). Suppose now that the temperature which is equal to TO at t = 0 is increased at a linear rate: T = ut + TO. Then integration of the rate equation yields:

s 1

dx -=-

0 f(x)

1 u

T s

To

k(T) dT

What Professor VALLEThas done is to calculate the integral on the right-hand side for two different forms of the rate constant : the classical form of Arrhenius k = A exp (-E/RT) and the form dictated by the old collision theory of reaction rates k = aTt exp (-E/RT). This was done for all values of z = E/RT likely to be of importance in the applications. This is an important piece of work. The author, with considerable modesty, mentions only casually one possible example where his extensive numerical tables might be useful : thermogravimetry. But there are many more possibilities. Indeed, the study of reaction rates in a system that is not isothermal but where the temperature is increased at a linear rate is a powerful attractive technique that has been used only too little in the past. The reason why it has not been used more extensively is the labour involved in the interpretation of the data. With the numerical tables now available, this objection no longer holds. This little book is written in three languages: French, English and Spanish. The English text consists of 20 pp. The tables are spread over 30 pp. This is not very long and this reviewer wonders why the author has not used the traditional vehicle for publishing his novel and interesting work, namely a scientific journal. Is it perhaps that he was discouraged by the obsession for brevity that is shared by most editors of scientific journals ? These tables are recommended to all who deal with applied chemical kinetics. M. B~UDART

in the atmosphere. Kappears to us the analogy should be quite complete up to the point of cloud formation in the atmosphere where, of course, transfer of the latent heat of vaporization to clouds makes the analogy break down. Department of Mechanical Engineering Vanderbilt University Nashville 5, Tennessee

W. SUMMER: Ultra-Violet and I&a-Red Pitman, London, 1962, xx + 300 pp.. 42s.

D. JACOBS

Engineering.

ALTHOUGH radiation methods have not yet found wide applications in chemical processing, the uses of ultra-violet and infra-red frequencies for sterilization, drying and other purposes are we11 known. Dr. SUMMERargues that the techniques and applications of these radiations, lying just outside the visible spectrum, have now developed to the stage where they constitute a separate branch of engineering, which he has named paraphotic engineering. l%s book begins with a theoretical introduction which considers radiation sources, detectors and filters. Other sections describe ancillary equipment and health hazards, but the greater part is devoted to a discussion of several different engineering applications which are drawn from fields as diverse as photochemistry, photocopying, infra-red heating and artificial satellites. It would appear that the author has attempted to provide both a textbook and a handbook, but in this he has been only partly successful. The accounts of the methods of oroducing, detecting and filtering these radiations are usefui but much of the subsequent text is highly discursive and in parts of little relevance. The purpdse of including a tsible of hydrogen diffusion coefficients through metals is by no means clear, and a section on the Leather and Shoe industry is almost entirely concerned with a discussion of polymerization reactions. As a whole, the book does succeed in giving a largely descriptive account of the applications and techniques employed, and contains many references. Most of the information is easy to find but an index of the numerous tables would have been desirable. C. N. KENNEY

F. H. REYNST: Pulsating Oxford, 310 pp. 100s.

Combustion. Pergamon

Press,

PROFESSORTHIUNG, in editing this collection of papers by REYNST,hopes to cast the ,seeds for industrial development: they might, however, fall on stony ground since it will he said that some of the ideas have been examined in Germany and France. 50

Translated

Abstracts

Dr. HATFIELDonce reported that few of the world’s outstanding inventions have been developed by large corporations; the latter mainly preferring the safe investment of research to improve materials. REYNST’Sinvention of a unique pulsating combustor may thus be frustrated by the lack of the necessary large development funds. However, professional engineers, through ad hoc Panels of their Institutions, may wish to demonstrate their desire to bring new ideas to fruition. One might visualize a joint panel of specialists from the Institutions, Industry and Government obtaining the technical and financial data necessary to judge the collaborative development potential of REYNST’Sideas. The first application for pulsating combustors was the low cost but low efficiency V-l resonant pulse-jet. Study of the valveless but elaborate 1936 REYNSTpatent here gave place to P. SCHMIDT’Singenuity in devising a “ mouth-organ ” reed valve for the air supply. Since valves are unsuitable for high frequencies, development of ~YNST’S system for aircraft propulsion occurred in France, until overtaken by the efficient turboprop and turbojet engines. REYNST,however, believed from his observations that some of the chemical energy of the fuel was converted directly into the organized kinetic energy and vacuum of the vortex in his combustdr and, provided that research could substantiate his claim, he forecast a big step forward in aircraft propulsion by using this high efficiency process to accelerate backwards the boundary layer of the wings. REYNST’Sideas ‘included the use of combustion pressure rise and combustion jet reaction to gain efficiency in gas turbine cycles but, curiously, he did not consider the application of his pulsating system to chemical reactors or M.H.D. generation. In applying pulsating combustion to pulverized coal fired boilers, REYNSTlooked for higher heat transfer rates, the elimination of fans and a 10 per cent gain in coverting heat to mechanical energy: the latter by using the vacuum periodically created in the combustion chamber to draw air through a turbine. Duplex “ push-pull ” burners were envisaged to avoid atmospheric noise. Ruhrgas A. G. in 1954/5 carried out some development work and THIUNGhas included a paper by SOMMERS on this. The style and SQUID translation make this book clear to read but, due to addressing many different audiences, there is repetition in the papers. THEUNG, however, gives useful reading guidance. The few misprints are fairly obvious. This book should disseminate REYNST’Sideas to a number of specialists but if THRING has faith in the applicability of

REYNST’Swork, a future much shorter text would serve to stimulate the considerably wider audience who are concerned with industrial innovation. M. E. PEPLOW Four-Language Dictionary of Chemistry and Chemical Te&KBlOgy. Editor Mgr. inz. Z. SOBECKA,English Editors Professor H. STEPHEN and Dr. T. STEPHEN. Pergamon Press, Oxford 1962, E10. THIS dictionary originated in Poland, but this edition is designed for English-speaking users. The three other languages are German, Polish and Russian. The main body of the book consists of an alphabetical list of some 12,000 words or terms in English, each followed by its three foreign equivalents. For each foreign language there is an alphabetical list of the terms in that language, referring by number to the corresponding English terms. There is also an index of English synonyms to chemical compounds. The Editor’s Note states that the dictionary is based on exact terminology as found in the current literature. This is an admirable principle to adopt in such a compilation, even though exactness sometimes calls for the inclusion of terms which sometimes differ only slightly in meaning. The names of chemical compounds have been restricted to group names and to particular compounds of practical importance. Many scientific names similarly expressed in each of the four languages have not been included. Many terms in use by industrial chemists are included in the dictionary. Its probable utility to the chemical engineer may be judged from the following randomlyselected inclusions and omissions. Included : Heat exchanger, pressure-head, Reynolds number, humidity, relative humidity, wet-bulb and dry-bulb temperature, hygrometer, enthalpy, mass-transfer, bubble-cap, bubble-cap plate, sieve-plate, reflux and reflux-ratio, reboiler, heads, bottoms, theoretical, plate, fluidization, fluidized bed, packing, Raschig rings. Omitted: heat-transfer and mass-transfer coefficient, pressure-drop, friction factor, Prandtl, P&let and Schmidt numbers, absolute humidity, hygrometry, total heat, tray (as in distillation column), boil-up, partial condenser, transfer unit, residence time. The price will no doubt deter many potential users of this dictionary, in spite of its high standard. P. V. DANCKWERTS

TRANSLATED

ABSTRACTS

The publishers regret that owing to the shortened production schedule necessary to achieve publication of manuscripts within four months of acceptance, the following translated abstracts were not received in time to be published with the article concerned. Mass transfer

in a catalyst pellet during regeneration: 17 323.

J. M. AUSMAN and C. C. WATSON 1962

R&sum&-Les auteurs d&ivent le transfert de masse asso& g la rkgknkration de simples pastilles de catalyseur poreux. La vitesse de combustion locale du carbone est considkrke comme &ant du premier ordre par rapport g la fraction molaire locale d’oxygkne: les profils de concentration d’oxyg&e et de carbone dans la pastille sont obtenues en fonction du temps pour une pastille de catalyseur sphkrique, entour& par un film de gaz. Les r&hats ont permis d’obtenir les huations de vitesse globales de combustion du carbone pour des pastilles. 51