Spined Tubes in Crossflow Exchangers SIR: A recent article in INDUSTRIAL AKD ENGINEERING CHEMISTRY surprises me in that it is so general in the description of spined tubing [ I / E C > 52, No. 11, 925 (1960)l. Your authors are usually more specific in their descriptions. The fact that you were referred to Thermek Corp. as supplier of the tubing coupled with the fact that Thermek Corp. was dissolved some years ago, leads me to believe that your authors based their conclusions on testS of materials now obsolete and produced by companies who are either out of business, or who no longer produce Thermek. T o be precise, Thermek Corp. itself never produced a foot of Thermek. I t was merely a patent-holding and licensing company. Thermek as now produced by Heatron has many configurations. LVhen one considers that we produce 'e-, l,'4-, 3 e-; 2-, 3,, d-, 1-, and 1' *-inch SPS pipe sizes, it becomes apparent that more specific terms should be used in designating materials under test. Incidently, Thermek has always been produced in standard pipe sizes, not tube sizes. Now, when we multiply the seven pipe sizes available by the number of spine diameters available and again multiply by the number of spines per turn that can be furnished and again multiply that total by the variables in longitudinal pitch available in copper alone, you can see that there are thousands of combinations to be tested. Very recent tests h a w shown that increasing the spine diameter or length of spine on one size by '/B-inch has reduced pressure drop from 14 p.s.i. on a given unit to 8 p.s.i. At the same time, the B.t.u. transfer dropped from 800 to 700 B.t.u.'s. From this example, you can see that variations in design make a big difference. Heatron is prepared to substantiate its claim that on double pipe applications in particular, when properly applied with the proper specifications, Thermek by Heatron will not only hold its o\vn but will surpass conventional surfaces Since Heatron is the sole producer of Thermek in the United States, your article could be interpreted as-we are producing a n inferior product. I do not feel that this is the message that your authors wish to convey. ~
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Il'e ivelcome the opportunity to have tests made on 'Thermek. We wish only that these tests be made on surfaces designed to do the job. We will gladly cooperate by supplying any reasonable quantities of present-day Thermek for test. C. KENNETH SHANAMAS General Manager Heatron. Inc. York. Pa. SIR: 'The spined surfaces used in the recent investigation were described and illustrated in a previous article to which \ 1951, on an application filed in the U. S. Patent Office on February 20, 1948; and to Tawney, P. O., U. S. Patent 2,626,252, granted January 20: 1953, on an ap-
DUSTRIAL A N D
plication filed in the V. S. Patcnt Office on Sovember 12. 1948. Ladd described the preparation of 3,3,3,-trichloro-l-propene, giving physical constants which agree closely with those reported by Freidlina and Skinner, and assigning the same structurc to the compound. Tawney described many copolymers of 3,3,3,-trichloro-l-propene,including a copolymer with vinyl acetate, this being one of the copolymers described by Skinner. E. C. LADDAND P. 0 . TALVSEY Research Center U. S. Rubber Co. LVayne, Y. Y.
