TY - JOUR

T1 - Boiling regimes of HFE-7100 and water droplets at impact on a superheated surface

AU - Gatapova, Elizaveta Ya

AU - Sitnikov, Vadim O.

N1 - The study was supported by Russian Science Foundation (project no. 22-19-00581), https://rscf.ru/en/project/22-19-00581/.

PY - 2024/12

Y1 - 2024/12

N2 - Dielectric liquid cooling represents a highly desirable solution for the cooling of electronics. One of the most effective cooling methods is spray cooling systems, which involve the droplet impact process. The methoxynonafluorobutane (HFE-7100) liquid exhibits a low latent heat of vaporization and a boiling point of 61 °C. The data on the interaction of HFE-7100 droplets with a hot surface are presented in detail for the sapphire plate temperature range of 50 to 160 °C and Weber number varying from 50 to 160 for the first time. Comparative experiments were conducted for water with substrate temperatures ranging from 120 to 240 °C and Weber numbers of 20 to 83. The various modes of droplet interaction dynamics were described and classified using top-view and side-view visualization by a high-speed camera enhanced with a stereomicroscope. The temperature of the droplet surface and substrate is measured from the top using an infrared camera with special calibration. The results are presented in a combined map of droplet dynamics and boiling regimes. The distinctive properties of HFE-7100 liquid permit the observation of all boiling regimes with significantly lower superheat than that of water. The rebound regime is observed in a wider range of Weber numbers (up to 150) than for water (up to 50). For a high Weber number and high superheat, the HFE-7100 droplet is observed to spread over the vapor layer and levitate as a very thin liquid film without bubbles, which then ruptures and atomizes into small-scale levitating droplets. For We>150, the maximum spreading diameter is found to be greater in the film boiling regime at levitation than in all other boiling regimes. A modified formula for maximum spreading diameter dependent on surface temperature is proposed. A comparison with data from the literature is also presented. The droplet surface temperature was measured using an IR camera from above. A qualitative analysis of heat transfer was conducted based on a semi-analytical model for a spreading droplet, and the results were compared with the measured droplet surface temperature.

AB - Dielectric liquid cooling represents a highly desirable solution for the cooling of electronics. One of the most effective cooling methods is spray cooling systems, which involve the droplet impact process. The methoxynonafluorobutane (HFE-7100) liquid exhibits a low latent heat of vaporization and a boiling point of 61 °C. The data on the interaction of HFE-7100 droplets with a hot surface are presented in detail for the sapphire plate temperature range of 50 to 160 °C and Weber number varying from 50 to 160 for the first time. Comparative experiments were conducted for water with substrate temperatures ranging from 120 to 240 °C and Weber numbers of 20 to 83. The various modes of droplet interaction dynamics were described and classified using top-view and side-view visualization by a high-speed camera enhanced with a stereomicroscope. The temperature of the droplet surface and substrate is measured from the top using an infrared camera with special calibration. The results are presented in a combined map of droplet dynamics and boiling regimes. The distinctive properties of HFE-7100 liquid permit the observation of all boiling regimes with significantly lower superheat than that of water. The rebound regime is observed in a wider range of Weber numbers (up to 150) than for water (up to 50). For a high Weber number and high superheat, the HFE-7100 droplet is observed to spread over the vapor layer and levitate as a very thin liquid film without bubbles, which then ruptures and atomizes into small-scale levitating droplets. For We>150, the maximum spreading diameter is found to be greater in the film boiling regime at levitation than in all other boiling regimes. A modified formula for maximum spreading diameter dependent on surface temperature is proposed. A comparison with data from the literature is also presented. The droplet surface temperature was measured using an IR camera from above. A qualitative analysis of heat transfer was conducted based on a semi-analytical model for a spreading droplet, and the results were compared with the measured droplet surface temperature.

KW - Boiling

KW - Bubbles

KW - Droplet impact

KW - Droplet spreading

KW - HFE-7100

KW - Hot surface

KW - Regime map

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85200813386&origin=inward&txGid=f2d059851bb0f034332dc95fba417ac0

UR - https://www.mendeley.com/catalogue/d86d44a9-e923-339f-8c74-1ffe6aaad9a9/

U2 - 10.1016/j.ijthermalsci.2024.109317

DO - 10.1016/j.ijthermalsci.2024.109317

M3 - Article

VL - 206

JO - International Journal of Thermal Sciences

JF - International Journal of Thermal Sciences

SN - 1290-0729

M1 - 109317

ER -