This paper describes a new design method for constructing a heat exchanger computational model comprising TPMS (Triply Periodic Minimal Surface) core structures. These TPMS-Based core structures cannot be designed using the existing CAD systems, especially for heat exchangers with a high level of geometric complexity. This paper introduces a new implicit design algorithm based on the VDF (Volumetric Distance Field) calculation. All geometric components, including the TPMS-based core structures, heat exchanger exterior shapes, a set of parts for inlets and outlets, are represented by the VDF in a given design area. This enables the efficient design of computational models for the arbitrary-complex heat exchangers. The proposed design method extends the 2D flow pattern of the existing CHE into the 3D flow pattern, providing high heat transfer efficiency and low-pressure drop. Investigation of the design results and manufactured prototypes using the AM (Additive Manufacturing) technology showed that the proposed TPMS CHE design method can open a new paradigm for generating high-performance next-generation CHEs which cannot be designed and manufactured with the existing CAD and CAM technologies.