Today, compact PHEs produced by additive manufacturing method have emerged when high heat transfer and low-pressure drop are required from PHEs under high temperature and pressure operating conditions. This has resulted in attention to the design of the plate surface geometry. In this study, a PHE of compact class of which plate surface has a lung pattern was fabricated by additive manufacturing method for their purpose of pressure drop reduction and improvement of heat transfer. The novel compact PHE was tested under single-phase water flow conditions. In addition, the thermal performance of the designed PHE was investigated numerically. As a result of the study, the hot side heat transfer rate of the lung patterned PHE was reported as 3206.06W and 2891.36W, with a 10% deviation according to the experimental and numerical results, respectively. For a water-to-water PHE, a good performance and pressure drop has been achieved by using the geometric features of the existing commercial PHEs, such as the minimum plate thickness (0.5mm) and the distance between two plates (1.5mm), in the developed design. Thus, the number of plates and the volume of the PHE can be reduced for the same amount of heat transfer in commercial PHEs. In addition, this study provides indications of the importance of plate surface geometry design for compact PHEs produced by additive manufacturing. (c) 2022 Elsevier Ltd. All rights reserved.