Abstract
In this study, a novel, thorn-shaped, containing, hydrophilic, and hydrophobic surface is proposed to have a better condensate drainage characteristic and to delay the required time for frosting. By using a hydrophilic and hydrophobic mixed thorn-shaped surface created by screen printing, the design makes use of the differences in the wettability gradient to achieve rapid condensate drainage and to lengthen the time for frosting. The results of a frosting experiment indicated that the droplet adsorption and combination and discharge effect in the thorn sample were substantial. The drainage effect increased the surface renewal rate and inhibited ice layer growth on the thorn sample by 52.4% compared with that on pure copper surface. The heat transfer coefficient of the thorn sample during frosting was approximately 16.2% higher than that of pure copper surface. In addition, the defrosting results indicated that the defrosting time of the thorn sample was almost equal to that of the pure copper sample. However, large droplets were easily stagnated at the structural junction due to contact angle hysteresis after defrosting.
Highlights
Heat exchangers have been widely used in modern industrial and mechanical equipment and play a key role in processing and manufacturing
Due to concerns regarding environmental pollution and energy utilization, improving the energy efficiency, the fin frosting phenomenon of finned tube heat exchangers used in air conditioning and refrigeration systems, has become a crucial issue
The results indicated that compared with the pure copper surface, the superhydrophobic modified surface delayed the freezing time by approximately 55 min
Summary
Heat exchangers have been widely used in modern industrial and mechanical equipment and play a key role in processing and manufacturing. Due to concerns regarding environmental pollution and energy utilization, improving the energy efficiency, the fin frosting phenomenon of finned tube heat exchangers used in air conditioning and refrigeration systems, has become a crucial issue. In addition to reducing system efficiency, accumulation of a frost layer causes an increase in the air-side pressure drop and fan power consumption [1]. Melted frost water can reduce heat transfer and cause refrosting, which reduces energy efficiency appreciably. To solve the aforementioned problems, many scholars have studied defrosting technology for heat exchangers. The defrosting-related technologies can be classified into active and passive designs [2]. Active designs increase the defrosting capacity through the energy input method. Active designs can considerably improve the defrosting capacity, they increase system complexity and consume additional energy
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