Condensation outside vertical tubes

Condensation Outside Vertical Tubes. This arrangement requires careful distribution of coolant to each tube, and requires a sump and a pump for return to a cooling tower or other source of coolant. Advantages are the high coolant side heat transfer... 

Table V. Effect of Vibration on Steam Condensation outside Vertical Tubes...

The condensation inside vertical tubes is similar as to mechanisms for condensation outside each tube. As the condensate flows down the tube (inside), the liquid film... 

For condensation inside and outside vertical tubes the Nusselt model gives ... 

Figure 8.14. Some arrangements of shell-and-tube condensers, (a) Condensate inside tubes, vertical upflow. (b) Inside tubes, vertical downflow, (c) Outside tubes, vertical downflow, (d) Condensate outside horizontal tubes. (HEDH, 1983, 3.4.3).

Condensation Outside Horizontal Tubes. Figure 8.14(d) shows a condenser with two tube passes and a shell side provided with vertically cut baffles that promote side to side flow of vapor. The tubes may be controlled partially flooded to ensure desired subcooling of the condensate or for control of upstream pressure by regulating the rate of condensation. Low-fin tubes often are advantageous, except when the surface tension of the condensates... 

A vertical, short-tube evaporator is shown in Fig. 2. A bundle of short tubes (A), 4-8 ft long and 2-A in. in diameter is placed in a vertical shell (B) in which the evaporating liquor is introduced. Steam condenses outside the tubes causing boiling of the liquor. The liquor spouts upward inside the tubes and returns through the downtake. Concentrated liquor is removed from the bottom of the evaporator (C) and liquid vapor is removed at (D). The cross-sectional area of the downtake is 25% of the total cross-sectional area of the tubes. 

These equations are strictly valid only for a plane vertical surface. However, they can be used for inside or outside vertical tubes with small error because the condensate film is thin compared with the diameter of a typical tube. Because of rippling and other nonidealities, the predicted coefficients are about 10-20% below experimental values. 

For shell-and-tube condensation related topics include evaporation (Section 16.11.4.1) and distillation (Section 16.11.4.2). Prefer condensation outside horizontal tubes use vertical tubes when condensing immiscible liquids to subcool the condensate. Assume pressure drop of 0.5 of the pressure drop calculated for the vapor at the inlet conditions. Baffle spacing is 0.2 to 1 times the shell diameter with the baffle window about 25%. Limit pressure drop for steam to 7 kPa on the shell side. U = 0.5 to 0.85 kW/m °C. 

Vertical-type natural circulation evaporator. In this type of evaporator, vertical rather than horizontal tubes are used, and the liquid is inside the tubes and the steam condenses outside the tubes. Because of boiling and decreases in density, the liquid rises in the tubes by natural circulation as shown in Fig. 8.2-lb and flows downward through a large central open space or downcomer. This natural circulation increases the heat-transfer coefficient. It is not used with viscous liquids. This type is often called the short-tube evaporator. A variation of this is the basket type, where vertical tubes are used, but the heating element is held suspended in the body so there is an annular open space as the downcomer. The basket type differs from the vertical natural circulation evaporator, which has a central instead of annular open space as the downcomer. This type is widely used in the sugar, salt, and caustic soda industries. 

Vertical In-Shell Condensers Condensers are often designed so that condensation occurs on the outside of vertical tubes. Equation (5-88) is valid as long as the condensate film is laminar. When it becomes turbulent. Fig. 5-10 or Colburns equation [Tran.s. Am. Jn.st. Chem. Ertg., 30, 187 (1933-1934) maybe used. 

McAdams and Kem bodi suggest the same relationship for condensation on the outside of vertical tubes ... 

Figure 10-67A. Condensing film coefficients outside horizontal or vertical tubes. (Used by permission Kern, D.Q. Process Heat Transfer, Ed., 1950. McGraw-Hill, Inc. All rights reserved.)...

Figure 10-67B. Correlation of McAdams representing the condensing film coefficient on the outside of vertical tubes, integrated for the entire tube length. This represents the streamline transition and turbulent flow conditions for Prandtl numbers 1 and 5. Do not extrapolate Prandtl numbers, Pr beyond 5. (Used by permission Engineering Data Book II 1984, Wolverine Tube, Inc.)...

Figure 10-71. Condensing steam film coefficients for vertical surfaces or horizontal tubes. G 7n,/ restricted to < 1,090. For theoretical h , for horizontal tubes, use and multiply results by 0.8. G = condensate mass flow per unit tube outside circumference, vertical tubes, lb/(hr) (ft). (Used by permission Devore, A. Petroleum Refiner, V. 38, No. 6, 1959. Gulf Publishing Company, Houston, Texas. All rights reserved.)...

In horizontal condensers (outside tubes), for N tubes in a vertical row, with the condensate flowing uniformly from one tube to the one below without extensive splashing, the mean condensing coefficient, h j, for the entire row of N tubes (per Knudsen in reference 94A) is related to a film coefficient for the top, h, single tube by ... 

Go = condensate mass flow per unit tube outside circumference, vertical tubes, lb./(hr) (ft)... 

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