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Condensing reflux designs

Q: Can you recommend some published references that discuss vertical shell-side condensing reflux designs? I have read articles that discussed reflux condensers condensing inside the tubes, but I have not come across any articles that discuss vertical condensing outside the tubes. This type of heat exchangers is common for overhead condensers in distillation columns under vacuums and also for vent condensers in tanks and drums. Even though non-condensibles are present and the vapor flow direction is up while the condensed liquid is down, there should not be any flooding issues since the condensation is outside the tubes. Are the heat transfer coefficients correlations for condensation inside the tubes applicable for this type of heat exchanger designs? What is the approximate overall heat transfer coefficient of this type of reflux condensers assuming some non-condensibles are present?

A: I have not searched the literature for shell side reflux condensation, however the best approach would be to treat it as a normal shell side condensation problem and assure that the mechanism is in the gravity flow regime. Calculation of flooding velocity can be approximated by utilizing the tube side methods with a hydraulic diameter approach of the bundle. The heat transfer coefficient for any condensation unit is going to be highly dependent upon the quantity of inerts present in the mixture being condensed. However, normal shell side methods as described in a variety of references should be adequate. Consider Process Heat Transfer by Hewitt, Shires & Bott.