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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

Frosting behavior on a superhydrophobic heat exchanger

Hisuk Kim
School of Mechanical Engineering, Hanyang University, Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea

Jaehwan Lee
School of Mechanical Engineering, Hanyang University, Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea

Kwan-Soo Lee
School of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul, 133-791, Korea

Abstract

Superhydrophobic surfaces are effective for delaying and limiting ice formation. However, most experiments are carried out in small size of metal surface, applicable unit experiment has not been studied. Thus, the experiment is conducted in heat exchanger unit applied in refrigerant cycle. A wide fin pitch heat exchanger was chosen to maintain uniform hydrophobicity and the superhydrophobic surface was formed by the etching method. The experiment was lasted for 2 hours with the heat pump operating condition. The frosting behavior was observed with a CCD camera and endoscope. Frosting was triggered by condensation at the tube. The condensation droplets on the superhydrophobic tube tended to remain liquid longer than on the bare surface. This produced ice via the phase change and the ice started spreading to the fin. On bare surfaces, the spreading speed was very fast in the fin area which was quickly covered with frost. In comparison, the fin surface of the superhydrophobic heat exchanger was not covered with ice. In addition, the frosting behavior in the tube and fin area was analyzed along refrigerant temperature. Bare and superhydrophobic surfaces were compared under each operating conditions (−9, −15, and −25°C). The superhydrophobic effects were noticeable when the refrigerant temperature was high (at -9°C). The superhydrophobic effect disappeared as the refrigerant temperature decreased. It is recommended that temperatures over -10 °C are appropriate when using superhydrophobic surfaces on heat exchanger.

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