Helical pipe coils

A theoretically derived equation for laminar flow in helical pipe coils by Ruthven (Chem. Eng. Sci, 26, 1113-1121 [1971] 33, 628-629 [1978]) is given by... 

Jackets, internal helical pipe coils, tube baffles, and plate coil baffles are used to provide heat-transfer surface area. The only surface area effective for heat transfer is that portion that is wetted by both service and process fluids. The effective heat-transfer area for some items may be determined as follows ... 

Helical pipe coils can be manufactured by various means ... 

Recommended methods for assessing the corrosivity of waters, including flowing potable waters, are described in ASTM 02688 1983. Three procedures are described in which test specimens in the form of wires, sheets or tubes are placed in pipes, tanks or other equipment. The test assembly for the first of these consists of three helical wire coils mounted in series on, and electrically insulated from, a supporting frame. The assembly must be installed so that flow is not disturbed and turbulence and high velocities, e.g. of more than 1 -53 ms , are avoided. A minimum test period of 30 days is recommended. Procedures for the other specimen forms are given in the standard. 

B - Cast iron vessel with integral steel tubes C - Welded helical coil with intercolated copper plates D - Welded half pipe coil... 

If only small amounts of heat need to be transferred, the tank wall is a satisfactory heat transfer surface, when appropriately jacketed (Fig. 1.2). The wall surface often is inadequate for heat transfer, particularly in the case of industrial tanks, because upon scale-up the liquid volume increases according to D whereas the surface area only increases according to D. Additional heat transfer surfaces have then to be installed in the form of differently designed pipe coils or pipe bundles (helical coils, meander coils (cooling basket) tube bundles see Fig. 1.3). 

Heat transfer Batch Internal helical-coil, jacket—agitated conventional, baffled conventional, conventional, dimple, half-pipe coils... 

Rhodes, and Scott Can. j. Chem. Eng., 47,445 53 [1969]) and Aka-gawa, Sakaguchi, and Ueda Bull JSME, 14, 564-571 [1971]). Correlations for flow patterns in downflow in vertical pipe are given by Oshinowo and Charles Can. ]. Chem. Eng., 52, 25-35 [1974]) and Barnea, Shoham, and Taitel Chem. Eng. Sci, 37, 741-744 [1982]). Use of drift flux theoiy for void fraction modeling in downflow is presented by Clark anci Flemmer Chem. Eng. Set., 39, 170-173 [1984]). Downward inclined two-phase flow data and modeling are given by Barnea, Shoham, and Taitel Chem. Eng. Set., 37, 735-740 [1982]). Data for downflow in helically coiled tubes are presented by Casper Chem. Ins. Tech., 42, 349-354 [1970]). 

The process for manufacturing helical seam line pipe (previously called spiral weld) is shown schematically in Figure 5.9. As in ERW pipe, steel strip in coil form is used, but the coil is formed into a spiral. The seams are welded by the DSAW process as in UOE pipe. Some early prejudice against helical... 

Pipe diameter of internal helical or harp coil and particle diameter, ft... 

The simplest and cheapest form of heat transfer surface for installation inside a vessel is a helical coil see Figure 12.75. The pitch and diameter of the coil can be made to suit the application and the area required. The diameter of the pipe used for the coil is typically equal to Dj,/30, where Dj, is the vessel diameter. The coil pitch is usually around twice the pipe diameter. Small coils can be self-supporting, but for large coils some form of supporting structure will be necessary. Single- or multiple-turn coils are used. 

Tank Coils Pipe tank coils are made in a wide variety of configurations, depending upon the application and shape of the vessel. Helical and spiral coils are most commonly shop-fabricated, while the hairpin pattern is generally field-fabricated. The helical coils are used principally in process tanks and pressure vessels when large areas... 

The experimental data, which were obtained for flow velocities of continuous phases of v = 0.4 to 6 m/s, have been evaluated according to expression (8.27). An excellent agreement was found between the measured maximum droplet size and the calculated one, independently of whether a straight pipe or a helical coil was used. 

Another method of applying the advantages of film evaporation is exhibited in Wetzel s evaporator, one form of which was a horizontal helical coil of copper steam piping, revolving so that the lower part dipped into the juice contained in a trough, and in its revolution carried up a thin layer which rapidly evaporated. 

It can be seen by comparing T ables 1 and 2 that if mechanical agitation is used and a jacket is desired, then additional internal coils are required. The internal coils can be vertical, like baffles, or helical. Agitation experts state that helical coils can be used with radial turbines if the spaces between the coil loops are 1 to 1.5 pipe diameters, Once helical coils are accepted. Why use ajacket at all Reasons in favor of coils (in addition to the better heat transfer coefficient) are ... 

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