words the conical protrusions are preferably centered on the circular surfaces of the tubesheets 180 and 190 the inclusion of the conical protrusions results in the reduction and or elimination of a small dead zone and low flow area which would otherwise tend to be present in the present heat exchanger adjacent to the center of the interior tubesheet surface facing the heat exchanger cavity the particular low flow area which otherwise would be present in the heat exchanger results from the inclusion of the shell extensions 170 and cone 135 components of the present invention by including the tubesheet protrusions the spaces in heat exchanger 100 which are taken up by the protrusions which would otherwise be u201c dead zones u201d or low flow areas are filled up with solid material so that the low flow areas and u201c dead zones u201d are eliminated with negligible or no loss of heat transfer capability the sizing and detailed shape of the conical protrusions may vary from the examples provided above fluid modeling methodologies as are known in the art may be employed if desired to determine the particular sizes and shapes that meet the desired criteria for the specific design of course the conical protrusion on one tubesheet need not be the same in terms of size or shape as another conical protrusion on another tubesheet within a particular heat exchanger sizing and shaping between and among protrusions on tubesheet surfaces may vary according to expected specific fluid flow velocities and tendencies heat exchanger 100 also includes central pipe 145 which transports tube side fluid from.