Flow and Heat Transfer Characteristics of Hydrophobic and Hydrophilic Microchannel Flow

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 16560174
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Thermal engineering
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: SUZUKI Yuji Tokyo Institute of Technology, Graduate School of Science and Eng., Assist.Professor, 大学院・理工学研究科, 助手 (20242274)
• Project Period (FY): 2004 – 2005
• Keywords: Microchannel / Functional Solid Interface / Hydrophobic and Hydrophilic Wall / Two Phase Flow / Flow Characteristics / Bursting of Liquid Film

Research Abstract

Characteristics of single and two-phase flow in hydrophobic and hydrophilic microchannels were investigated in the laminar flow range. The hydrophobic microchannel was made by a glass tube coated with a silicone. Drag reduction did not occur in degassed tap water flowing in pipes with the smooth hydrophobic surface by measuring the pressure drop. Experiments in two-phase flow (nitrogen and tap water) were carried out to measure the total pressure drop and the flow pattern by using a microscope and a high-speed VTR system. For small liquid flow rate, total pressure drop in the hydrophobic microchannel was much higher as compared with the normal channel. That flow pattern was small liquid and gas segments flowing in the pipe without liquid film. The separation and adhesion of the liquid on the solid wall at both ends of liquid slug, caused larger drag than the slug flow with liquid film. Meanwhile, in the hydrophilic surface, a bursting of liquid film is expected to be hard to arise. The hydrophilic microchannel two-phase flow is more expectative for a drag reduction than the hydrophobic channel. However, it was too difficult to make a hard photocatalytic TiO_2 coating inside of a microchannel for a hydrophilic surface.