Vertical combined feed/effluent heat exchanger with variable baffle angle

Abstract

A shell and tube heat exchanger, such as a vertical combined feed / effluent heat exchanger (VCFE), including: a shell having a fluid inlet and a fluid outlet; a plurality of baffles mounted in the shell to guide the fluid into a helical flow pattern through the shell; wherein a helix angle α of a baffle proximate the inlet is different than a helix angle β of a baffle proximate the outlet.

Description

FIELD OF THE DISCLOSURE[0001]Embodiments disclosed herein relate generally to a heat exchanger. More specifically, embodiments disclosed herein relate to a heat exchanger, such as a shell and tube heat exchanger, configured to efficiently process two-phase flow.BACKGROUND[0002]Numerous configurations for heat exchangers are known and used for a variety of applications. One of the widely used configurations, a shell and tube heat exchanger, as illustrated in FIG. 1, includes a cylindrical shell 10 housing a bundle of parallel pipes 12, which extend between two end plates 14 so that a first fluid 16 can pass through the pipes 12. Meanwhile, a second fluid 18 flows in and through the space between the two end plates so as to come into contact with the pipes. To provide an improved heat exchange between the two fluids, the flow path of the second fluid 18 is defined by intermediate baffles 20 forming respective passages, which are arranged so that the second fluid flow changes its direc...

AI Technical Summary

Problems solved by technology

This causes a reduction in the dynamic pressure of the second fluid and non-uniform flow velocity thereof, which, in combination, adversely affect the performance of the heat exchanger.

For example, a perpendicular position of the baffles relative to the longitudinal axis of the shell results in a relatively inefficient heat transfer rate / pressure drop ratio.

Additionally, such baffle arrangements produce flow bypass through baffle-to-shell and pipe-to-baffle clearances, resulting in flow maldistribution, eddies, back-flow, and higher rates of fouling, among other undesired consequences.

Increasing unit design capacities (economy of scale) requires large volumetric throughput with a resultant impact on the number of shells required to transfer the heat at the limited temperature differentials.

However, due to the flow hydraulics issues, i.e., two phase inlet flow, varying composition and molecular weight of the vapor and liquid phases, and variable volumetric flow and pressure drop resulting from phase change, the arrangement of conventional exchanger shells in several parallel and series arrangements is problematic.

Symmetrical piping is an unreliable means to effect partitioning of two phase flow.

A drawback of the shellside boiling arrangement is considered at partial load or turndown operation, where the shellside velocities may not be sufficient to prevent phase separation and backflow of the liquid fraction back down to the inlet.

Such buildup of heavy liquid fraction at high residence time can result in fouling.

The main drawback of any tubeside boiling arrangement is that the vapor and liquid fractions must be evenly distributed in each of a multiplicity of tube inlets, in order to maintain the expected boiling characteristics in each tube, and an inexpensive and low pressure drop method to achieve this distribution has not been found.

Images