Abstract: A heat transfer tube for use in a refrigeration evaporator. This tube includes an outer surface with axially spaced bent fins which form and enclose annular tunnels. The bent fins have top edge portions which have peripherally spaced sets of notches of different sizes on the same fin convolution and refill gaps for fluid flow to the tunnels for heat transfer through the annular wall. The concept of placing different pore sizes next to each other on the same fin allows a more efficient use of the tube's surface area for evaporative heat transfer.