A distillation column based air separation unit comprising: a lower pressure column; a higher pressure column; one or more condenser-reboiler modules having a housing defining a top, a bottom, one or more lateral sides, an upper portion, and a lower portion, the one or more condenser-reboiler modules disposed within the lower pressure column, coupled to the lower pressure column and the higher pressure column, and configured to receive nitrogen-rich vapour as a condensing medium from the higher pressure column at a condensing inlet centrally disposed at the top of the housing, an oxygen-rich liquid from the lower pressure column at an oxygen-rich liquid inlet, and further defining a condensate outlet proximate the bottom of the housing and an oxygen-rich effluent outlet; a shell and tube heat exchanger (30A, 30B) disposed in the one or more condenser-reboiler modules and comprising two opposed tube sheets (36, 38) corresponding to the top and bottom of the housing, a cylindrical shell corresponding to the one or more lateral sides of the housing connecting the two opposed tube sheets (36, 38), an inlet conduit centrally and vertically disposed within the shell configured to direct the condensing medium from the condensing inlet to a location proximate a bottom of the cylindrical shell and a plurality of vertical tubes extending between the two opposed tube sheets 36, 38), the shell and tube heat exchanger configured to partially vaporize the oxygen-rich liquid flowing within the plurality of tubes thereby forming an oxygen-rich effluent and condense the condensing medium within the cylindrical shell forming a condensate; wherein the condensing medium enters the one or more condenser-reboiler modules at the condensing inlet, traverses through the inlet conduit and is released within the shell and tube heat exchanger (30A, 30B) in the one or more condenser-reboiler modules at the bottom of the cylindrical shell and flows in an upward and radially outward direction within the cylindrical shell and non-condensables present in the condensing medium accumulate proximate the upper portion or top of the one or more condenser-reboiler modules; and one or more vents disposed proximate the upper portion or top of the housing for the one or more condenser-reboiler modules and configured to remove the accumulated non-condensables from within the one or more condenser-reboiler modules. a lower pressure column; a higher pressure column; one or more condenser-reboiler modules having a housing defining a top, a bottom, one or more lateral sides, an upper portion, and a lower portion, the one or more condenser-reboiler modules disposed within the lower pressure column, coupled to the lower pressure column and the higher pressure column, and configured to receive nitrogen-rich vapour as a condensing medium from the higher pressure column at a condensing inlet centrally disposed at the top of the housing, an oxygen-rich liquid from the lower pressure column at an oxygen-rich liquid inlet, and further defining a condensate outlet proximate the bottom of the housing and an oxygen-rich effluent outlet; a shell and tube heat exchanger (30A, 30B) disposed in the one or more condenser-reboiler modules and comprising two opposed tube sheets (36, 38) corresponding to the top and bottom of the housing, a cylindrical shell corresponding to the one or more lateral sides of the housing connecting the two opposed tube sheets (36, 38), an inlet conduit centrally and vertically disposed within the shell configured to direct the condensing medium from the condensing inlet to a location proximate a bottom of the cylindrical shell and a plurality of vertical tubes extending between the two opposed tube sheets 36, 38), the shell and tube heat exchanger configured to partially vaporize the oxygen-rich liquid flowing within the plurality of tubes thereby forming an oxygen-rich effluent and condense the condensing medium within the cylindrical shell forming a condensate; wherein the condensing medium enters the one or more condenser-reboiler modules at the condensing inlet, traverses through the inlet conduit and is released within the shell and tube heat exchanger (30A, 30B) in the one or more condenser-reboiler modules at the bottom of the cylindrical shell and flows in an upward and radially outward direction within the cylindrical shell and non-condensables present in the condensing medium accumulate proximate the upper portion or top of the one or more condenser-reboiler modules; and one or more vents disposed proximate the upper portion or top of the housing for the one or more condenser-reboiler modules and configured to remove the accumulated non-condensables from within the one or more condenser-reboiler modules.