Heat transfer performance comparison of printed circuit heat exchangers with straight, zigzag and serpentine flow channels for waste heat recovery

Abstract

In the present study, a printed circuit heat exchanger (PCHE) is investigated numerically by solving the steady-state Navier–Stokes equations and energy equation. The PCHE is equipped with straight, wavy, and serpentine flow channels, allowing us to investigate the PCHE performance on a systematic basis of effectiveness and pressure drop between the inlet and outlet of the flow channels. Liquid water is utilized as a working fluid at temperatures of 30°C to 90°C, with geothermal heating rarely targeted for using water from hot springs. The numerical results are validated with experimental data, confirming that the shear stress transport (SST) turbulence model is suited for providing adequate accuracy. This study is intended to delve into several possible designs of PCHE's flow channels to reduce the pressure drop while increasing the effectiveness. Given the PCHE with 13 zigzag flow channels of the bending angle of 150°, the results show that the PCHE with the zigzag flow channels at a mass flow rate of 0.113 kg/s possesses significant heat transfer enhancement. When compared to the other two tested PCHEs (straight flow and serpentine flow passages), a 65% increase in effectiveness and a 39% rise in pressure drop are exhibited. The PCHE can be regarded as a recuperator of the Organic Rankine Cycle (ORC) and is generally thought to be an important part of maximizing the efficiency of the cycle. The favorable features of the zigzag PCHE make it possible to seamlessly integrate the zigzag PCHE into ORC as part of a waste heat recovery system in a feasible way to improve the ORC efficiency.