Numerical Investigation of the Thermal Disturbance Effect on Heat Transfer Performance in Printed Circuit Heat Exchangers

Printed circuit heat exchangers (PCHE) are increasingly vital in high-efficiency applications such as liquefied natural gas production, yet their performance is influenced by thermal disturbance effects. This study numerically investigates the thermal disturbance impact on heat transfer performance in PCHEs with varying the number of heat exchange units (1, 9, and 25). Simulations were conducted under turbulent flow conditions (Reynolds numbers, Re = 8,000–30,000) using water as the working fluid in both counter-flow and parallel-flow configurations. Results demonstrate that increasing the number of heat exchange units significantly enhances heat transfer performance, particularly at higher Re. Under counter-flow condition, the 25-unit model achieved a Nusselt number up to 17.60% higher than the single-unit model at Re ≈ 16,000, driven by lateral heat conduction between channels. This effect fosters a more uniform temperature distribution within the solid body of the PCHE model, reducing the standard deviation of overall temperature by up to 24.7% in multi-unit models compared to the single-unit model. The improvement of effectiveness between 25-unit model and the single-unit model increases as Re increased and it reaches the maximum value of 33.32% at Re ≈ 30,000. A predictive correlation was developed, incorporating dimensionless parameters (Re, number of units, and Prandtl number), to quantify heat transfer enhancement due to thermal disturbance and achieving an average deviation of 2.21% from simulation results. These findings highlight the role of thermal disturbance in enhancing PCHE performance and provide actionable insights for optimizing design parameters to improve thermal efficiency in compact heat exchanger applications.