Abstract: A multi-pass tubeside shell and tube heat exchanger comprises: a shell having flanged ends; a removable tube bundle having a fixed tubesheet at one end and a floating tube sheet at the opposite end; a false tube sheet bolted to the floating tubesheet and having a passage hole aligned with each tube in the floating tubesheet to direct the flow of tube fluid; and a bonnet having a flange bolted to the outer portion of the false tubesheet. The use of the false tubesheet and attachment of the bonnet to the outer portion thereof maximizes available tube space. With the removal of the bonnet, and the false tubesheet, the bundle can be conveniently removed.