Heat transfer Helical coils

Oldshue, J. Y. and A. T. Gretton, Helical Coil Heat Transfer in Mixing Vessels, Chem. Eng. Prog. 50, 1954, 615. 

Helical coils, heat transfer in 496 -- cooling coils 496... 

Cummings and West (Cll) extended the earlier work of Chilton et al. to a larger vessel and some different impellers. They obtained essentially the same correlations and also showed that their correlation for helical coil heat transfer was adequate to correlate the data of Rushton et al. (R15) for vertical baffle-coils. With a few scattered data, Cummings and West also indicate that changing the direction of rotation of their pitched-blade turbine had no significant effect on the heat-transfer coefficients. Data by Kraussold (K9), from a vessel in which a paddle with a very high ratio of blade width to diameter was used, also confirm the correlations of Chilton et al. 

Oldshue J.Y., Gretton A.T., Helical coil heat transfer in mixing vessels, Chem. Engng. Progr. 50 (1954) 12, p. 615-621... 

Helical Coils Heat transfer coefficients for fluids flowing inside helical coils can be calculated with modifications of the equations for straight tubes. The equations for straight tubes should be corrected as below ... 

Steam generator Integrated once-through type with helical coil heat transfer tubes... 

Jayakumar JS, et al. Experimental and CFD estimation of heat transfer in helically coiled heat exchangers. Chem Eng Res Des 2008 86 221-32. 

Description These exchangers are typically a series of stacked helical-coiled tubes connected to manifolds, then inserted into a casing or shell. They have many advantages hke spiral-plate designs, such as avoiding differential expansion problems, acceleration effects of the helical flow increasing the heat transfer coefficient, and compactness of plot area. They are typically selected because of their economical design. 

The fluidfoil impellers (shown in Fig. 18-2) usually give more flow for a given power level than the traditional axial- or radial-flow turbines. This is also thought to be an advantage since the heat-transfer surface itself generates the turbulence to provide the film coefficient and more flow should be helpful. This is true to a limited degree in jacketed tanks (Fig. 18-34), but in helical coils (Fig. 18-35), the... 

A wide variety of configurations exists for coils in agitated vessels. Correlations of data for heat transfer to helical coils have been of two forms, of which the following are representative ... 

In heat transfer applications, this jacket is considered a helical coil if certain factors are used for calculating outside film coefficients. The equivalent heat transfer diameter, D, for a rectangular cross-section is equal to 4 w (w being the width of the annular space). Velocities are calculated from the actual cross-section of the flow area, pw (p being die pitch of die spiral baffle), and die effective mass flowrate W dirough die passage. The effective mass flowrate is approximately 60% of die total mass flowrate of die jacket. 

The pardcular work of Oldshue and Gretton [13] on heat transfer outside helical coils is of considerable general application. Refer to Equation 5-74. 

This design is not well adapted to free-convection heat transfer outside a tube or coil therefore, for this discussion only agitation is considered using a submerged helical coil, Oldshue and Kern . 

A related but somewhat more recent work by Oldshue presents heat transfer to and from helical coils in a baffled tank, using standard baffling of T/12 located either inside the coil diameter or outside ... 

In the case of a storage tank with liquor of mass m and specific heat C heated by steam condensing in a helical coil, it may be assumed that the overall transfer coefficient U is constant. If 7 is the temperature of the condensing steam, Tt and To the initial and final temperatures of the liquor, and A the area of heat transfer surface, and T k the temperature of the liquor at any time t, then the rate of transfer of heat is given by ... 

A stirred reactor contains a batch of 700 kg reactants of specific heat 3.8 kJ/kg K initially at 290 K, which is heated by dry saturated steam at 170 kN/m2 fed to a helical coil. During the heating period the steam supply rate is constant at 0.1 kg/s and condensate leaves at the temperature of the steam. If heat losses arc neglected, calculate the true temperature of the reactants when a thermometer immersed in the material reads 360 K. The bulb of the thermometer is approximately cylindrical and is 100 mm long by 10 mm diameter with a water equivalent of 15 g, and the overall heat transfer coefficient to the thermometer is 300 W/m2 K. What would a thermometer with a similar bulb of half the length and half the heat capacity indicate under these conditions ... 

The simplest and cheapest form of heat transfer surface for installation inside a vessel is a helical coil see Figure 12.73. The pitch and diameter of the coil can be made to suit the... 

For very long, helically coiled steam generator tubes, and for conditions typical of liquid-metal fast breeder reactors (LMFBRs), where steam is generated on the tube side, an overall heat transfer correlation for the whole boiling length (from X = 0 to X = 1.0) has been deduced experimentally (Campolunghi et al., 1977b) ... 

Celata, G. P, M. Cumo, and A. Mariani, 1994b, Enhancement of CHF for Water Subcooled Flow Boiling in Tubes Using Helically Coiled Wires, Int. J. Heat Mass Transfer 37(l) 53-67. (5)... 

Case 1 Data on heat transfer between liquid and the vessel wall and between liquid and the surface of helical coil in the vessels stirred with flat-blade paddle stirrers were correlated as [4] ... 

Heat transfer is normally much more demanding on a large scale. The introduction of helical coils, vertical tubes, or other heat transfer devices causes an increased tendency for areas of low recirculation to exist. 

FIGURE 33 Practical heat transfer coefficients for use in estimating with helical coils and vertical tubes. 

Janssen, L.A.M. and Hoogendoom, C.J., Laminar Convective Heat Transfer in Helically Coiled Tubes , Int. J. Heat Mass Transfer, Vol. 21, pp. 1197-1206,1978. 

HEAT-TRANSFER COEFFICIENTS FOR FLUIDS FLOWING INSIDE HELICAL COILS 7.28... 

Calculate the heat-transfer coefficient for a fluid with a flow rate of 100 lb/h (45.36 kg/h) and the physical properties outlined in Example 7.18. The inside diameter of the tube is 0.62 in (0.016 m), and the tube is fabricated into a helical coil with a helix diameter of 24 in (0.61 m). 

Select the appropriate heat-transfer coefficient equation. Heat-transfer coefficients for fluids flowing inside helical coils can be calculated with modifications of the equations for straight tubes. The equations presented in Example 7.18 should be multiplied by the factor 1 + 3.5/1, /D,. where Di is the inside diameter and Dc is the diameter of the helix or coil. In addition, for laminar flow, the term (Dc/Dj)1/6 should be substituted for the term (L/Zl)1 3. The Reynolds number required for turbulent flow is 2100[1 + I2(/1,//1C)I/2. ... 

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