A shell and tube heat exchanger has at least one baffle to support the tubes within the casing of the heat exchanger, wherein the baffle intersects the inner casing wall along a substantial portion of the arc. The baffle has a bypass through which flows at least a portion of the fluid flowing into the casing and around the baffle. At least a portion of the bypass is outside of the casing. This flow of fluid through the bypass reduces pressure drop through the heat exchanger and also reduces to some extent, points adjacent to the baffles where fluid flow may stagnate.