Flow　maldistribution　causes　declining　plate-fin　heat　exchanger　thermal-hydraulic　performance.　A　first-of-its　kind　experimental　facility　and　the　related　data　acquisition　system　were　constructed　for　studying　liquid　gas　flow　distribution　in　a　plate-fin　heat　exchanger.　The　gas　Reynolds　numbers　ranged　from　1880　to　about　2600　and　the　inlet　dryness　(i.e.,　quality)　from　12%　to　41%.　Two-phase　flow　maldistribution　among　the　heat　exchanger　passages　was　more　widespread　compared　to　that　of　single-phase　flow.　More　specifically,　the　liquid-phase　distribution　was　more　uneven　compared　to　the　gas-phase　distribution.　The　inlet　flow　rate　and　dryness　were　identified　as　the　chief　factors　affecting　the　distribution　of　phases　in　the　heat　exchanger.　For　a　given　inlet　dryness,　the　two-phase　flow　distribution　became　increasingly　non-uniform　with　the　inlet　gas　flow　rate,　consistent　with　the　behavior　observed　for　singlephase　flow.　Additionally,　the　non-uniformity　in　the　gas　flow　distribution　decreased　and　that　in　the　liquid　flow　non-uniformity　increased　with　increasing　inlet　dryness　fraction.　A　novel　distributor　design,　with　a　complementary　fluid　cavity　was　also　built　and　tested.　Experimental　results　show　that　improving　the　distributor　design　is　very　effective　in　improving　the　two-phase　flow　distribution　in　plate-fin　heat　exchangers.　Based　on　heat　transfer　studies　conducted　at　a　single　Reynolds　number　of　about　1500　and　a　dryness　of　29.2%,　the　heat　exchanger　effectiveness　was　also　correlated　as　a　function　of　the　dryness　distribution　non　uniformity　parameter　S.　The　effectiveness　was　found　to　reduce　as　the　flow　distribution　became　more　uneven,　highlighting　the　importance　of　accounting　for　and　controlling　the　flow　maldistribution　through　proper　distributor　design.　(C)　2017　Institution　of　Chemical　Engineers.　Published　by　Elsevier　B.V.　All　rights　reserved.