Abstract:To address various challenges associated with conventional laminar flowmeters (LFM), such as inadequate linearity, significant length-diameter, inconvenient processing and use, and susceptibility to fluid-induced effects, a novel annular-gap laminar element structure is proposed, drawing inspiration from the double-cone flowmeter. This innovative design is accompanied by a comprehensive elucidation of its measurement principles and an analysis of the sources contributing to non-linear pressure losses within the flow conduit. Central to this design is the maintenance of coaxial alignment between the outer jacket cylinder and the cone and circular cylindrical, resulting in a flow channel characterized by concentric circular annual. Computational fluid dynamics (CFD) simulations were leveraged to ascertain the optimal cone angle of the conical guiding structure and establish the dimensional parameters of the laminar element. Furthermore, pressure taps were strategically positioned within the fully developed laminar segment of the flow channel, thereby theoretically mitigating localized losses at the inlet and outlet typical of conventional capillary-type LFM, as well as kinetic energy dissipation within the laminar development region. Experimental validation involved the fabrication of three distinct test specimens with varying gap dimensions, followed by rigorous testing. Results revealed that for flow rates below 53 mL/min, the measurement error of the laminar element remained within an acceptable margin of 3%. Likewise, within the flow rate range at (130~6 189) mL/min, the measurement error was constrained within the range of ±2%. Notably, a robust linear relationship between pressure drop and flow rate was observed, affirming the efficacy of the proposed design in circumventing the non-linear influences inherent in traditional LFM. The elucidation asserts the structural efficacy of annular gap laminar flow elements in effectively mitigating the nonlinear influences characteristic of traditional LFM. Simultaneously, it highlights the adaptability of the measured flow range, which can vary with alterations in gap size.