<p>A heat exchanger comprising a shell and core (6) and a shell side medium inlet/outlet (3) arranged on the shell; the shell also comprises a cylinder (1) and a convex sealing head (2); a reducing pipe (4) having two ends of unequal diameter is arranged between said cylinder and said convex sealing head the large diameter end (43) of said reducing pipe being fixed to said convex sealing head and the small diameter end (42) of said reducing pipe being fixed to said cylinder; the shell side medium inlet/outlet arranged on the convex sealing head. Using the described structure allows the ends of the heat exchanger ample space to accommodate workers creating the conditions for double sided welding testing and maintenance and effectively reducing manufacturing costs and expanding the range of selection of materials; said structure also provides a buffer zone for the flow of the shell side medium making heat exchange more uniform and complete and facilitating the arrangement of deflectors and other auxiliary bodies improving the heat exchange efficiency of the heat exchanger and lowering operation costs.</p>
