Numerical analysis for jet flow field on cleaning the outer wall of the double-layer injection needle

Abstract

To avoid cross-contamination between different samples, improve the cleaning effect of the outer wall of the inner needle of the digital PCR detector, and reduce the cost of cleaning solution, the cleaning jet was simulated by FLUENT software using VOF gas-liquid two-phase flow model and PISO algorithm. In a certain range, the inlet velocity, cleaning solution viscosity, interfacial tension, and contact angle are changed to simulate the theoretical cleaning of the outer wall of the injection probe and the selection of various parameters under the best cleaning conditions is determined. The results show that the increase of inlet velocity has no significant effect on the increase of wall static pressure and the decrease of velocity increases; the increase of viscosity will greatly reduce the flow rate; higher interfacial tension requires higher inlet velocity to form a continuous jet; increasing the contact angle will not significantly reduce the static pressure and flow rate, and the residual sample is easier to clean. When the inlet velocity of 200mm /s is selected, the fluorine oil with a viscosity of 0.00124Paꞏs and interfacial tension of 16.2dyn/cm is used and the wall is coated with Teflon, the cleaning effect, and economy are excellent.