A Study on Enhancement of Critical Heat Flux in Pool Boiling by Marangoni Effect
Project/Area Number |
18560187
|
Research Category |
Grant-in-Aid for Scientific Research (C)
|
Allocation Type | Single-year Grants |
Section | 一般 |
Research Field |
Thermal engineering
|
Research Institution | Hokkaido University |
Principal Investigator |
SAKASHITA Hiroto Hokkaido University, Grad. School of Eng, Associate Professor (00142696)
|
Project Period (FY) |
2006 – 2007
|
Project Status |
Completed (Fiscal Year 2007)
|
Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥1,600,000 (Direct Cost: ¥1,600,000)
|
Keywords | Boiling / Critical heat flux / Aqueous binary solution / Marangoni effect / Conductance Probe / Macrolayer / Liquid-capor structure / 2成分混合液 / プール沸騰 / ミクロ液膜 / 低圧 |
Research Abstract |
A purpose of the present study is to develop an effective method to drastically enhance the critical heat flux (CHF) in pool boiling. The present study focused on the method by using positive mixtures; binary aqueous solutions where less volatile component has lower surface tension. In the boiling of the positive mixtures, liquid motion may be induced at the liquid-vapor interface due to surface tension gradient: it is known as the Marangoni effect. This method will be potentially attractive since it is simple and passive requiring no active equipments. However, the reason why the Marangoni effect is able to enhance the CHF has not been clarified. This research selected 2-propanol-water mixture as the positive mixture and measured the CHF with a 12mm diameter horizontal disk at pressures 5kPa to 100kPa. It was found that the CHF of the mixture was 1.7 to 2.2 times greater than that of water in the whole range of pressures. To clarify the mechanism for the CHF enhancement with the mixture, liquid-vapor structures close to the heating surface were measured using high accurate conductance probe of which tip diameter is less than 5μm. It was found that for boiling of the mixture vapor generation was suppressed in the central area and activated in the periphery of the heating surface. As a result, the liquid macrolayer of the mixture formed in the central area of the heating surface was considerably thicker than those of water. This thicker macrolayer is one of the causes to enhance the CHF of the mixture. The difference of boiling activation between the center and periphery of the heating surface is most likely to be caused by the Marangoni convection induced around the large vapor mass.
|
Report
(3 results)
Research Products
(5 results)