Heat exchanger with helical baffles

A heat exchanger, comprising:

• a shell;
• a plurality of baffles inside the shell;
• a plurality of holes in the plurality of baffles;
• a plurality of tubes received in the plurality of holes in the plurality of baffles;
• a first clearance between each of first holes of the plurality of holes and corresponding ones of the plurality of tubes;
• and
• a second clearance between each of second holes of the plurality of holes and corresponding ones of the plurality of tubes, wherein the second clearances are greater than the first clearances and configured to increase a leakage stream through the second clearances relative to the leakage stream through the first clearances.

A heat exchanger, comprising:

• a shell;
• a plurality of baffles inside the shell;
• a plurality of first holes in the plurality of baffles;
• a plurality of tubes received in the plurality of first holes in the plurality of baffles;
• and
• a plurality of second holes in the plurality of baffles between at least some of the plurality of first holes.