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Edwin H. Young Department of Chemical and Metallurgical Engineering, The Uniwrsity of Michigan, Ann Arbor, Mich. 48104
Improvements in overoll heat transfer coefficients of up to 50% were obtained in an experimental study comparing the performance of corrugated tubes with that of plain tubes in condensing steam ot 101” ond 212°F. Water-cooled cupronickel and copper tubes, oriented horizontally ond arrayed in verticol rows, were employed to condense steam on the outside of the tubes. Correlations of the data yielded design equations for the tube side and shell side coefficients of heat transfer and for tube side pressure drop. The recommended equations may be used to calculate the potential of the unique corrugated condenser tubing in distillotion-type desalting plants, in steam ?r plants, or in other steam applications. app power Design studies indicote that improved enoble significant savings in condenser length, tubing coefficients icients for the corrugated tube eno . . and installation . .. cost, with no sacrifice in pumping cost. weight, shell material, I .
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T h e production of fresh water from saline water has grown considerably through the use of distillation techniques. The most common type of water distillation plant utilizes the multistage-flash (MSF) process. Its heart is the horizontal condenser tubing, typically of copper alloy composition and ordinary cylindrical shape. Alteration of the shape of the tubing presents interesting possibilities in the design of such plants; and skillful application of properly shaped tubing should reduce the overall cost of the desalted water. This paper calls attention to a proprietary tubing shape (Andersen, 1964; Rodgers, 19651, which has been tested in the laboratory, and which is commercially available. The special configuration of tubing is referred t o in this paper as “corrugated tube.” Figure 1 shows sections of the corrugated tube. The configuration is attained without thinning the tube wall a t the focus of the corrugation. Dimensions and characteristics of the corrugated tubes, investigated along with corresponding plain hare tubes, are shown in Table I.
Since the design of MSF desalting plants involves steam condensing temperatures ranging from approximately 250” to W F , the experimental program was planned to include condensing studies a t two representative levels of temperature: 212” and 101- F. Other variables of interest were in-tube water velocity, log mean temperature difference, and number of tubes in a vertical row. The range of variables for investigation is shown in Table 11.
Heot Transfer Experiments
The objective of the experimental program was to obtain heat transfer design correlations that would predict the effectiveness of the corrugated tubes in actual steam condensing applications. Two heat transfer rigs were used: a concentric tube water-to-water apparatus was used to acquire the necessary data to characterize the behavior of the inside of the tube; and a multiple-tube horizontal condensing heat exchanger was used to collect the heat transfer data for the condensation of steam. ‘To whom correspondence should be addressed
Figure 1. Section of 1-inch od 18-goge, corrugated 90-10 cupronickel and %-in. od 20-goge, corrugoted copper tubes Ind. Eng. Chem. Process Der. Develop., Vol. 10. No. 1 , 1971
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Table 1. Tube Dimensions and Characteristics of Four Tubes Investigated ?,-In, Tube Type
Bare
Tube outside diameter, in. Tube inside diameter, in. Tube wall thickness, in. Tube length, in. Tube material
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