Thermocapillary effect of single and dual plug system in microchannel

• Main Author: Shen, Weijian.
• Other Authors: Wong Teck Neng
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/16812
• Institution: Nanyang Technological University

The project includes the formulation of the equation of motion (EOM) of the single and dual plug train, the designing of the holding fixture to hold the capillary tube, the modification of the MATLAB program which was used to process the experimental data and the investigation of the different parameters which influenced the thermocapillary effect of the single and dual plug train. Based on the derived EOM, the six parameters which affect the velocity of the plug are the contact angle, density of fluid, radius of capillary tube, plug length, difference of the surface tension of the two ends of the plug and the viscosity of fluid. The EOM serves as the governing equation to explain the thermocapillary effect in the experiment result. A holding fixture with adjustable legs was designed to hold the capillary tube parallel to the platform to prevent the plug from moving due to gravitational force. The MATLAB program was modified to process the experimental result for the dual plug train. For the single silicone oil plug system, the effects of power supply, effect of plug length at low power supply of 1.157W, effect of plug length at high power supply of 4.630W and the effect of radius of curvature were being analyzed. The largest displacement and highest average velocity was observed at the highest power supply, shortest plug length at low power supply of 1.157W and smallest radius of curvature. The effect of plug length at high power supply of 4.630W was different from at low power supply of 1.157W and could be divided into two regimes – before and after the “critical plug length”. Before the “critical plug length”, the displacement and average velocity increased with increasing plug length and after the “critical plug length”, the displacement and average velocity decreased with increasing plug length. For the dual silicone oil-DI water plug train system, the effects of encapsulating an extra DI water plug within the silicone oil and the length of the encapsulated DI water plug were being examined. The displacement and average velocity of the dual plug train system was lower than the single oil plug. The length of the DI water plug did not affect the motion of the plug train until a very long DI water plug was being encapsulated.