This work introduces a heat exchanger design approach for units using combined twisted tape and twisted tube heat transfer enhancement technology. In design and retrofit, the use of these systems is characterized by heat transfer enhancement on both sides of the unit. It is shown that the rate of increase of heat transfer is much higher than in single twisted tubes leading to improved designs. Thermal and hydraulic experimental published data on these types of surfaces are employed in developing the design approach. In the case of design, an area reduction of up to 32.2 % with a length reduction of 31.4 % for the same pressure drop levels is achieved. In the case of retrofit, the use of a combined twisted tube and twisted tape led to a heat load increase of 29.2 % with an increment of 40.4 % in pressure drop. The methodology is demonstrated in a case study from the open literature.