Tube bundles boiling

Kettle 10-lF Tube bundle removable as Boiling fluid on shell side, as For horizontal installation. 1.2-1.4... 

If the tube bundle is to be large in diameter, it is possible that the liquid head will suppress the boiling in the lower portion of the horizontal bundle thereby actually creating a liquid heating in this region, with boiling above this. Under such situations, the boiling in the unit cannot be considered for the full volume hence, there should be two shell-side coefficients calculated and the resultant areas added for the total. 

Palen and Taborek proposed as the best choice for circular tube bundles (as compared to square) the following film boiling coefficient after analyzing available data (their... 

The following is a calculation procedure suggested by Paien and SmalP for the required boiling coefficient for a horizontal tube bundle ... 

Calculate the correction to the nucleate boiling film coefficient for the tube bundle number of tubes in vertical row, hi,. See previous discussion. 

The vapor composition at the top of the condenser (Y,i) is different from that at the bottom (Y, ). The condenser may be compared to a fractional distillation problem in reverse. Butane, having a higher boiling point, will condense out faster than the propane, although both are condensing at the same time. Thus, the vapor and liquid mol fractions from the top to the bottom of the condenser tube bundle are always changing. Proceed as follows The vapor at the top has the same composition as the gas leaving the evaporator. Therefore, Y,. = Y,. 

Chen s method was developed from experimental data on forced convective boiling in vertical tubes. It can be applied, with caution, to forced convective boiling in horizontal tubes, and annular conduits (concentric pipes). Butterworth (1977) suggests that, in the absence of more reliable methods, it may be used to estimate the heat-transfer coefficient for forced convective boiling in cross-flow over tube bundles using a suitable cross-flow correlation to predict the forced-convection coefficient. Shah s method was based on data for flow in horizontal and vertical tubes and annuli. 

The maximum heat flux for stable nucleate boiling will, however, be less for a tube bundle than for a single tube. Palen and Small (1964) suggest modifying the Zuber equation for single tubes (equation 12.64) with a tube density factor. This approach was supported by Palen et al. (1972). 

Caira, M., E. Cipollone, M. Cumo, and A. Naviglio, 1985, Heat Transfer in Forced Convective Boiling in a Tube Bundle, 3rd Int. Topic Meeting on Reactor Thermohydraulics, ANS, Saratoga, New York. (4)... 

Translate the heat-transfer area determined above into corresponding tube bundle dimensions. If different from those assumed in step (2), repeat steps (2) through (8) until satisfactory agreement is reached. The s-IVm method cannot be appHed to cases in which U varies along the tube length or the stream temperature profile is not smooth, ie, boiling or condensation is included. 

The multitubular fixed-bed reactor (Fig. IB) constitutes the oldest and still predominant representative of this class. The catalyst packing is located in the individual tubes of the tube bundle. The heat-transfer medium is circulated around the tube bundle and through an external heat exchanger, in which the heat of reaction is supplied or removed ( Fig. 16). Whereas with endothermic reactions circulating gas can be used as heat transfer medium, for strongly exothermic reactions exclusively liquid or boiling heat transfer media are used. Only in this way can the catalyst temperature (c.g., in the case of partial oxidations) be held in the narrow temperature range necessary for selective reaction control. 

The kettle reboiler is shown in Fig. 11-35K When nucleate boiling is to be done on the shell-side, this common design provides adequate dome space for separation of vapor and hquid above the tube bundle and surge capacity beyond the weir near the shell cover. 

Heat-transfer coefficient in condensation Mean condensation heat-transfer coefficient for a single tube Heat-transfer coefficient for condensation on a horizontal tube bundle Mean condensation heat-transfer coefficient for a tube in a row of tubes Heat-transfer coefficient for condensation on a vertical tube Condensation coefficient from Boko-Kruzhilin correlation Condensation heat transfer coefficient for stratified flow in tubes Local condensing film coefficient, partial condenser Convective boiling-heat transfer coefficient... 

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. 

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