Filter units, filtration systems, and methods of using

A filter unit comprising:

• a heat exchanger having headers and a plurality of conduits between and fluidically connecting the headers to define fluid flow passages within the heat exchanger, the headers comprising at least first and second headers that each have oppositely-disposed first and second ends, at least the first header having a port disposed at the first end thereof that is fluidically connected to the fluid flow passage within the first header;
• and
• a housing having an upstream wall disposed at an upstream side of the housing, a downstream wall disposed at a downstream side of the housing, and a cavity therebetween in which the heat exchanger is disposed, the upstream wall having a first entrance opening therein and first and second upstream wall portions separated by the first entrance opening, the downstream wall having first and second exit openings therein and a downstream wall portion between the first and second exit openings, the upstream and downstream walls defining first and second pairs of partial enclosures that partially enclose, respectively, the first and second ends of the first and second headers of the heat exchanger at oppositely-disposed first and second lateral ends of the filter unit, each of the partial enclosures having an opening through which a corresponding one of the first and second ends of the first and second headers is exposed, the first pair of the partial enclosures facing each other across a first access opening at the first lateral end of the filter unit, the second pair of the partial enclosures facing each other across a second access opening at the second lateral end of the filter unit, the first and second access openings defining therebetween a lateral narrowed section of the filter unit, the first and second access openings providing access to, respectively, the first and second ends of the headers through the openings in the first and second pairs of partial enclosures, the first access opening providing access to the port of the first header through the opening in a first of the partial enclosures of the first pair of partial enclosures.