Vertical U-Tube Heat Exchangers

Normally the tubesheet and front head are at the top so the bundle lifts out through the head opening, and the U-bends hang downward into the shell. That puts both tube-side nozzles at the top. With condensing in the tubes, vapor enters at the top and condensate runs down one leg, around the bend and up the other, so the design has to make sure the return leg does not hold a liquid seal. Tubesheet-down mounting is used where the shell side must drain through the head end, but then the bundle comes out downward, which is rarely practical.

Shell-side drainage of a vertical unit is complete only if the bottom nozzle sits at the low point of the shell and nothing in the bundle traps liquid above it. On a U-tube bundle the bends sit at the bottom, so the shell drain must be below the bend tips and the lowest baffle needs drain notches. Without them a ring of liquid stays around the bends after every batch. With product in the tubes this problem does not arise, which is one more reason the product side is the tube side on sanitary units.

The bundle length plus the lifting gear, meaning the spreader or sling, the hook and whatever clearance the hoist needs at the top of its travel. Plan on several feet beyond the bundle rather than inches. The overlooked case is a unit under a mezzanine where the clear height exists but a beam crosses the lift line. If headroom is short, a removable roof panel, a lifting beam installed at build time, or a shorter and larger-diameter bundle are the usual answers. Give the clear height to the lowest obstruction with the inquiry.

On tall vertical units, yes: the support skirt or lugs, the anchor bolts and sometimes the shell thickness near the base are governed by overturning moment rather than by pressure. The pressure parts are unchanged in principle, but the mechanical design has to carry the lateral load into the foundation. This is a site-specific calculation, so the Request a Quote should state the site seismic category and wind exposure, and whether the unit stands alone or is braced to adjacent structure. Horizontal units on saddles almost never raise this issue.

With the shell fixed at one support elevation and free to grow upward or downward from it, so the growth is not pushed into the piping. On a skirt-supported unit the base is fixed and the whole shell grows upward, taking the top nozzles with it, so the top piping needs flexibility. With lug support the lugs sit partway up and the shell grows both ways from them. The mistake is to hard-pipe both ends; the nozzles then crack. Tell us where the rigid piping is and the support can be placed to suit.