Condensation frosting on meter-scale superhydrophobic and superhydrophilic heat exchangers


Boyina K. S. , Mahvi A. J. , Chavan S., Park D., Kumar K., Lira M., ...More

INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, vol.145, 2019 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 145
  • Publication Date: 2019
  • Doi Number: 10.1016/j.ijheatmasstransfer.2019.118694
  • Title of Journal : INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
  • Keywords: Condensation frosting, Defrosting, Water retention, Heat exchangers, Superhydrophobic, Scalable, Nanostructure, Silane, Coatings, Wetting, THERMAL-HYDRAULIC PERFORMANCE, ICE-ADHESION STRENGTH, LOUVERED-FIN, DEFROSTING CHARACTERISTICS, SURFACE, WETTABILITY, GROWTH, PUMP

Abstract

Frost formation on heat transfer equipment such as air-source heat pump evaporators can result in drastic efficiency penalties. The performance reduction is a result of the insulating nature of ice and the increased fan power required to pump air through the constricted channels between frosted fins. Furthermore, the need to defrost adds appreciable energy use to the system. In this study, we develop a nanoengineered coating process that can be scalably applied to meter-scale, fully-assembled, aluminum heat exchangers. We demonstrate the coating on a decimeter-scale copper-tube aluminum-fin commercial heat exchanger having a 25 x 15 cm face area, and 9 corrugated fins per inch. The frosting characteristics on the unaltered heat exchanger are compared to identical components with superhydrophobic and superhydrophilic coatings for a range of inlet coolant temperatures (-5 to -10 degrees C) and ambient humidities (30 to 50%). The results show that a superhydrophobic heat exchanger can decrease frost accumulation, maintain heat transfer rates above half of the maximum capacity three times longer, reduce the required defrosting time and energy by 50%, and reduce the amount of water retained by 75% when compared to its uncoated and superhydrophilic counterparts. (C) 2019 Elsevier Ltd. All rights reserved.