Fundamental understanding of flow distribution control in parallel multi-channel heat transfer devices with electrohydrodynamic conduction pumping

Flow maldistribution in heat transfer devices such as parallel tube heat exchangers is an undesirable phenomenon that results from uneven pressure drops among the channels. Factors like non-uniform heating, geometric configuration, and system orientation can contribute to these imbalances in pressure drop, which can significantly diminish the overall energy performance of the system. In this study, Electrohydrodynamic (EHD) conduction pumping has been fundamentally studied as an active method to control the distribution of the flow in multi-channel heat exchangers. EHD conduction pumping is based on a net Coulomb force applied to a dielectric fluid. This force arises due to the formation of heterocharge layers, layers of opposite polarity, near asymmetric submerged electrodes, which are caused by enhanced dissociation of impurities in the fluid under a strong electric field. In this work, a two-dimensional domain representing a mesoscale heat exchanger using HFE-7100 as the working fluid was numerically investigated. The device comprises two parallel channels (each 7 cm long and 0.5 cm high), with electrohydrodynamic (EHD) conduction pumps embedded at the inlet. After establishing a foundational understanding of the influence of EHD conduction-driven flow distribution control on the system’s thermal performance under uneven heating loads at steady-state, an emphasis is placed on transient processes that govern the system’s response to sudden changes in operating conditions, as commonly encountered during flow distribution adjustment, going beyond the earlier work in this domain. Results show that transient charge accumulation takes 5.5 ms to reach a steady-state magnitude of (0.000826–0.000829) C/m, depending on the applied potential. This time is in the order of charge relaxation time. Additionally, the novel effect of pulsation on EHD-driven flow distribution control is investigated in detail to fundamentally understand its impact through the transient formation of the heterocharge layers. The contribution of pulsation is shown to depend strongly on the operating conditions and the applied frequency. • Electrohydrodynamic (EHD) conduction pumping is fundamentally studied as an active method to control flow distribution and overcome heat-induced flow maldistribution in parallel multi-channel heat transfer devices such as heat exchangers. • Transient development of heterocharge layers is investigated during flow adjustment. • The effect of pulsation on EHD-driven flow distribution control is explored.