Rectangle-gap-type laminar flow meter with inward pressure taps

Abstract

The entrance/exit effects in the current traditional LFMs (Laminar Flow Meter) are unavoidable. LFMs are often designed with a large length-diameter ratio l/d and the consequence is a large pressure loss. A rectangle-gap-type LFM with a laminar flow channel made from the groove between two cubes is proposed and investigated experimentally. The pressure taps located inward the inlet/outlet of the channel replace the original pressure taps that located at the inlet/outlet of channel, so that the rectangle-gap-type LFM can measure the pressure drop from the developed laminar flow to avoid the entrance/exit effects. The results show that the linearity of the rectangle-gap-type LFM is 0.35% for the length-diameter ratio l/dh=93.5. The deviations are −0.35%~+1.30% in the pressure range 100–500 kPa. The estimated pressure loss coefficients (ζent+ζexit) of rectangle-gap-type LFM are only 0.15–0.2, which of traditional LFMs are used to be 1.5. The inward pressure taps allow rectangle-gap-type LFM to adopt a small l/dh design to achieve low pressure loss measurement. The investigation is of positive significance for improving the performance of LFM.