Cooling characteristics of ultrafine cryoprobe utilizing convective boiling heat transfer in microchannel

Junnosuke Okajima, Shigenao Maruyama, Hiroki Takeda, Atsuki Komiya, Sangkwon Jeong

研究成果: Conference contribution

8 被引用数 (Scopus)

抄録

This paper describes a novel cooling system to be applied in cryosurgery. An ultrafine cryoprobe has been developed to treat small lesions which cannot be treated by conventional cryoprobes. The main problem of the ultrafine cryoprobe is the reduction of the heat transfer rate by the small flow rate due to the large pressure drop in a microchannel and the large ratio of the surface area to the volume. In order to overcome these problems, we utilized boiling heat transfer in a microchannel as the heat transfer mechanism in the ultrafine cryoprobe. The objectives of this paper are to develop an ultrafine cryoprobe and evaluate its cooling characteristics. The ultrafine cryoprobe has a co-axial double tube structure which consists of inner and outer stainless steel tubes. The outer and inner diameters of the outer tube are 0.55mm and 0.3mm, respectively. The outer and inner diameters of the inner tube are 0.15mm and 0.07mm, respectively. The inner tube serves as a capillary tube to change the refrigerant from liquid state to two-phase flow. Furthermore, two-phase flow passes through the annular passage between the inner and out tube. The hydraulic diameter of the annular passage is 0.15mm. Furthermore, HFC-23 (Boiling point is -82.1°C at 1atm) is used as the refrigerants. The temperature of the ultrafine cryoprobe was measured. The lowest temperatures were -45°C in the insulated condition and -35°C in the agar at 37°C (which simulates in vivo condition). Furthermore, the frozen region which is generated around the ultrafine cryoprobe was measured 5mm from the tip of cryoprobe at 120s, and resulted to be 3mm in diameter. Moreover, the change of the refrigerant state is calculated by using the energy conservation equation and the empirical correlations of two-phase pressure drop and boiling heat transfer. As a result, the refrigerant state in the ultrafine cryoprobe depends on the external heat flux. Finally, the required geometry of the ultrafine cryoprobe to make high cooling performance is evaluated.

本文言語English
ホスト出版物のタイトル2010 14th International Heat Transfer Conference, IHTC 14
ページ297-306
ページ数10
DOI
出版ステータスPublished - 2010 12 1
イベント2010 14th International Heat Transfer Conference, IHTC 14 - Washington, DC, United States
継続期間: 2010 8 82010 8 13

出版物シリーズ

名前2010 14th International Heat Transfer Conference, IHTC 14
1

Other

Other2010 14th International Heat Transfer Conference, IHTC 14
国/地域United States
CityWashington, DC
Period10/8/810/8/13

ASJC Scopus subject areas

  • 流体および伝熱

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