Steam　condensation　in　the　presence　of　nitrogen　is　experimentally　performed　in　a　horizontal　rectangular　channel　with　cross　sectional　dimension　of　5　x　6　mm.　Steam　mass　flux　varies　from　203.7　to　431.3　kg　m(-2)　s(-1),　while　the　nitrogen　mass　fraction　from　is　0%　to　15%.　Coolant　water　flows　countercurrent　in　a　rectangular　channel　as　well,　which　is　the　same　size　with　the　steam　side.　The　steam　channel　is　on　top　of　the　coolant　channel,　and　the　released　heat　from　the　steam　is　transferred　to　the　coolant　water　by　heat　conduction　only　through　the　connecting　part　of　each　channel,　the　thickness　of　which　is　3　mm.　The　coolant　mass　flow　rate　is　from　500　to　1100　kg　h(-1),　while　the　corresponding　coolant　side　Reynolds　number　is　from　2.2　x　10(4)　to　5.1　x　10(4)　and　the　coolant　side　heat　transfer　coefficient　is　from　20.2　to　40.1　kW　m(-2)　K-1.　The　results　show　that　higher　coolant　Reynolds　number　results　in　significant　promotion　of　the　overall　heat　transfer　coefficient,　while　the　condensation　heat　transfer　coefficient　is　reduced.　In　addition,　larger　steam　mass　flux　leads　to　greater　overall　heat　transfer　coefficient　and　condensation　heat　transfer　coefficient.　However,　the　influence　of　nitrogen　on　condensation　is　not　significant,　especially　for　condensation　with　higher　steam　mass　flux.　(C)　2016　Elsevier　Inc.　All　rights　reserved.