Heat exchanger having tubular members concentric with fluid carrying tubes to prevent mixing of the heat exchange fluids and method of construction thereof

A heat exchanger comprising

• a shell having an inlet means and an outlet means for the flow of a first fluid therethrough,
• a plurality of tubes within the shell to provide a path for flow of a second fluid in heat exchange relation to the first fluid, and inlet means and outlet means disposed on respectively opposite ends of the heat exchanger for flow of the second fluid to and from said tubes respectively,
• a tubular member concentric with at least a portion of the length of at least one of said tubes, defining a space between said tube and said tubular member which is closed to flow of both the first fluid and the second fluid,
• a plurality of tube support means spaced apart and disposed generally perpendicular to the tube axes, having said tubular member fixedly attached at one end to one of said tube support means and at the other end to an adjacent one of said tube support means, wherein two of said tube support means comprise a pair of outer tube sheets for sealing attachment of said tubes at each of the ends respectively thereof to provide partitions against fluid flow between said space and the spaces for second fluid flow,
• said shell comprising an inner wall and an outer wall defining a space between said inner and outer walls which is closed to both the first and second fluid and in fluid flow communication with said space between said tube and said tubular member for flow of a third fluid therebetween,
• partitions between said third fluid flow spaces and the spaces for first fluid flow comprising two of said tube support means formed as tube sheets which are disposed inwardly of said outer tube sheets and sealingly attached to said tubular members and said outer shell wall, and
• means including at least one radially outwardly projecting longitudinally extending portion on said tubular member for flexing said tubular member for expanding thereof radially outwardly.