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CORRESPONDENCE Comments on “Comments on Recent Publications on ‘Minimum Fluidization Velocity at High Temperatures”’ Sir: We are happy to realize how much attention has been given to our work on incipient fluidization at high temperatures (Lucas et al., 1986). But, certainly, we are not that happy about certain comments by some investigators which seem to attribute as their own some of the original results of our investigations. To be specific, in a recent communication, Saxena and Mathur (1987) indicate that “...two recent i n d e p e n d e n t [italics are used for emphasis by present authors only] researchers (Lucas et al., 1986; Saxena et al., 1987,received for publication February 4,1986) have found that emf varies with temperature and have reported the same for sand beds of different sizes.” This statement is quite surprising since the same authors, in another article which was received for publication April 25,1985 (Mathur and Saxena, 1986), already mentioned the work by Lucas et al. (1986). We find hard to qualify as “independent” the results presented 10 months later from those quoted as already known. It is even more astonishing that reference to Lucas et al. (1986) (which had been already received for publication April 30, 1984) is made as a “private communication” and, as such, that we had never released a single preprint but the manuscript itself which was already submitted and not yet published. We are even more apalled to see that additional contributions of our work (Lucas et al., 1986)-which were also presented at the JournEes EuropEennes sur la Fluidisation (Lucas et al., 1983)-like our first attempt to explain the variation of emf with temperature in terms of the flow field configuration around the particle, have also been presented as theirs by these authors: In the last part of one of their recent communications (Mathur et al. (1986);received for publication March 10, 1986), they conclude “...As the Reynolds number is further increased, the separation point moves towards the downstream side of the particle equatorial plane, and the wake size decreases. This will reduce
the size of the wake and hence the magnitude of the inter-particle forces. As a result, emf increases ...” (there is an obvious printing error-which can be detected in Figure 7 of the same article-in the quoted paragraph where “decreases”appears instead of “increases”). Nevertheless, they do not mention that in our communication (Lucas et al., 1986) we stated “...Asthe Reynolds number is further increased, the separation point moves toward the rear of the particle (downstream), and the wake shrinks. Both friction and drag decrease, as well as the suction of the wake. Cohesive forces between particles will therefore decrease, and at incipient fluidization particles will rearrange themselves in a looser packing (higher emf).” Fluidization, like any other subject of research, offers an immense potential for creativeness, and we believe that it is with this approach that every researcher should work in an endeavour to achieve original results.
Literature Cited Lucas, A,; Arnaldos, J.; Casal, J.; Puigjaner, L. Communication presented at the JournCes EuropCennes sur la Fluidisation, Compiegne, France, 1983. Lucas, A.; Amaldos, J.; C a d , J.; Puigjaner, L. Chem. Eng. Commun. 1986,41, 121-132. Mathur, A.; Saxena, S. C. Powder Technol. 1986,45,281-289. Mathur, A.; Saxena, S. C.; Zhang, Z. F. Powder Technol. 1986,47, 241-256. Saxena, S. C.;Mathur, A. Znd. Eng. Chem. Res. 1987,26,859-860. Saxena, S.C.;Mathur, A.; Zhang, Z. F. AZChE J. 1987,33,5W502.
A. Lucas, J. Arnaldos J. Casal,* L. Puigjaner Chemical Engineering Department Uniuersitat Politecnica de Catalunya Diagonal 647 08028 Barcelona, Spain
Response to Comments on “Comments on Recent Publications on ‘Minimum Fluidization Velocity at High Temperatures’ ”
Sir: I am surprised and shocked to note the concern expressed by Lucus et al. in their preceding letter. Let me first put the true perspective of the research on the dependence of emf on temperature. Lucas et al., in their letter, give the impression that they were the first ones to propose it. Several years ago, Botterill and Teoman (1980) proposed it, and since then it has been confirmed by Botterill et al. (1982a,b). Lucas et al. might like to note the comments made by Saxena and Grewal(1981) when their work on the dependence of emf on temperature was begun. I feel that many others have made earlier similar comments, though somewhat implicitly in some cases, and these were referenced by Mathur and Saxena (1986a). I realize that the chronological development of any research topic cannot 0888-5885/88/2627-0367$01.50/0
be given in every article, but it has to be recognized if even an impression of claim to a scientific discovery is implied in an historical perspective. Lucas et al., in particular, seem to be concerned about the use of the word independent in relation to Saxena and Mathur’s (1987) reference to the works of Lucas et al. (1986) and Saxena et al. (1987). I do not see the basis of their objection. The works of Saxena et al. (1987) and Mathur et al. (1986) were conducted on separate equipment, in a different laboratory, and using different procedures from those of Lucas et al. (1986). This obviously makes them independent. Maybe Lucas et al. are confusing the meaning of independent with simultaneous in time. They should note that if our intention was to claim 0 1988 American Chemical Society
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historical priority, we could have ignored their work altogether. In fact, we are the ones who have brought their work into the limelight, and in the right perspective (as should be noted by the comments made toward the end of this letter) of which they are apparently quite happy, as indicated in the opening sentence of their letter. I did receive a copy of their paper (Lucas et al., 1986) as a preprint, and Lucas et al. should appreciate that Mathur and Saxena (1986a) gave them their rightful credit and continued to reference them in all subsequent publications. In fact, reference to Lucas et al.’s (1983) work came to our notice at a later date, and consequently, Saxena et al. (1987) referred to this work also, though with some degree of reluctance as they had not seen this paper. The reference to Lucas et al. (1986) was originally made as a private communication but later was changed to Chem. Eng. Commun., in press, as confirmed by the office of the journal’s editor. Lucas et al. misunderstand the implications of independent works. Many colleagues in the fluidization research community have reservations in accepting this notion of the dependence of emf on temperature, and investigations by different researchers will bring persuasive evidence to popularize this concept. Lucas et al. may like to note that Mathur and Saxena (1986a) emphasized this concept and its consequences in terms of the powder classification scheme earlier proposed by Saxena and Ganzha (1984), in a basic way. The implications of the dependence of emf on temperature have been analyzed on heat-transfer research in two recent publications; viz., Mathur and Saxena (198613,1987). The latter work and the hydrodynamic works of Mathur et al. (1986) and Saxena et al. (1987)referred to above were done in the same sequence. Lucas et al. again express their concern about Mathur et al.’s (1986) work and misquote out of context their statements. In the very paper of Mathur et al. (1986), in the very beginning, reference is made in great detail to the work of Lucas et al. (1986), and all their findings are reported, as well as those of other investigators. Any reader can assess for himself what credit is to be given to the individual investigators, and this was certainly not our goal while writing the paper. Lucas et al. (1986) were unfair in writing their paper and not referencing many other previous investigators who have done similar work. They
seem to reconfirm their unfair practice further when they quote extracts from the two works; viz., Mathur et al. (1986) and Lucas et al. (1986). Why won’t our conclusions have similarities with theirs when our experiments have led to similar qualitative results in many respects? Our statement was made in reference to a particular range of Reynolds numbers and refer to group IIB of Saxena and Ganzha’s (1984) powder classification scheme. They should be happy, as we are, that our independent experiments led to similar conclusions, which to some extent were imbedded in many earlier works. Saxena and coworkers have shown that the conclusions of these hydrodynamic studies, which were received by some researchers with reservations, are consistent with the heat-transfer investigations and are thus of potential value. The concluding statement of Lucas et al. has been the goal of researchers from ages, and they should not carry the impression of monopolizing on it. Literature Cited Botterill, J. S. M.; Teoman, Y. In Fluidization; Grace, J. R., Matsen, J. M., Eds.; Plenum: New York, 1980; pp 93-100. Botterill, J. S. M.; Teoman, Y.; Yuregir, K. R. Ind. Eng. Chem. Process Des. Dev. 1982a, 21, 704. Botterill, J. S. M.; Teoman, Y.; kuregir, K. R. Powder Technol. 198213, 31, 101.
Lucas, A.; Arnaldos, J.; Casal, J.; Puigjaner, L. Communication presented a t the Journees Europeennes sur la Fluidisation, Compiegne, France, 1983. Lucas, A.; Arnaldos, J.; Casal, J.; Puigjaner, L. Chem. Eng. Commun. 1986, 41, 121. Mathur, A.; Saxena, S. C. Powder Technol. 1986a, 45,287. Mathur, A.; Saxena, S. C. Energy 198613, 11, 843. Mathur, A.; Saxena, S. C. AIChE J. 1987,33, 1124. Mathur, A.; Saxena, S. C.; Zhang, Z. F. Powder Technol. 1986, 47, 247. Saxena, S. C.; Ganzha, V. L. Powder Technol. 1984, 39, 199. Saxena, S. C.; Grewal, N. S. Powder Technol. 1981, 30,96. Saxena, S. C.; Mathur, A. Ind. Eng. Chem. Res. 1987, 26, 859. Saxena, S. C.; Mathur, A.; Zhang, Z. F. AIChE J . 1987, 33, 500.
S . C. Saxena Department of Chemical Engineering T h e University of Illinois at Chicago Chicago, Illinois 60680
ADDITIONS AND CORRECTIONS Design Calculations for Multiple-Effect Evaporators. 1. Linear Method [Volume 26, Number 1, page 1001. Richard N. Lambert, Donald D. Joye,* and Frank W. Koko
Page 103. In Table I, the entries under the column labeled area should be divided by 3.6. Design Calculations for Multiple-Effect Evaporators. 2. Comparison of Linear and Nonlinear Methods [Volume 26, Number 1, page 1041. Frank W. Koko and Donald D. Joye*
Page 105. In Tables I and 11, the entries under the columns labeled area should be divided by 3.6. Page 106. In Table V, the entries under the column labeled area should be divided by 3.6.
