Typical designs and liquid flow models in the flow paths of axisymmetrical DHSs of a cylindrical type with side supply of liquid to the header: a, b. constricted DHSs with the displaced tube sheet in a shell and with free and constricted inlet sections respectively; c, d. constricted DHSs with a constricted inlet section, the displaced tube sheet in a shell and inserts of relatively large and small diameters respectively; e, f. superconstricted DHSs with a header constricted by the inlet section, with no lattice displacement in a shell with no and with inserts respectively; 1 – annulus; 2 – header; 3 – shell; 4 – lattice; 5 – bottom; 6 – insert; 7 – housing.