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Experiments were carried out for the manufactured a printed circuit heat exchanger (PCHE) using nitrogen on the super-critical state. For the core of the PCHE, ‘N’ and reverse N, ‘RN’ shape microchannels were etched on stainless steel 316L plates, and total 120 plates were diffusion bonded. Then, for the PCHE evaluation in which the headers were welded, liquid nitrogen of below -170 °C and about 0.8 MPa was pressurized to about 3.42 ∼4.59 MPa, then was injected to the inlet on the cold side, and nitrogen gas of 72.7 ∼75.1 °C and about 0.6 ∼0.75 MPa was flowed through channels on the hot side. The flow rates were 2401 ∼3211 kg/h and 1592 ∼2357 kg/h on the hot and cold sides, respectively. In particular, the nitrogen on the cold side was pressurized by a pump, and state changes occurred over pseudo critical point. In order to evaluate performance of the PCHE with the super critical state nitrogen, the channels were simplified and discretized, then, effectiveness-number of transfer units (e-NTU) method was applied. Then, a new correlation expecting the thermal-hydraulic performance of PCHE was developed as Nu = 0.023Re0.78Pr0.4.

The present study aims to improve the mean extracted power of a Wave Energy Converter (WEC) by mapping the parameters of its ballast weight and position, wave frequency, viscosity, and Power Take-Off (PTO) damping using an Artificial Neural Network (ANN) model. A total of 25 types of WEC rotors are designed with varying ballast weights and positions. The hydrodynamic coefficient and response of each rotor are determined using linear potential theory and viscous damping is estimated using computational fluid dynamics. The optimal design parameters are obtained by applying the trained model to a large randomly generated input dataset and the prediction output is evaluated to determine the best design parameters. According to the findings of the study, a well-trained model can predict and adopt to the nonlinear behavior of the given dataset as well as provide the optimal design parameters for the selected pitch-type WEC rotor.