Performance comparison of refrigerators integrated with superhydrophobic and superhydrophilic freezer evaporators

Micro and nanostructures can delay frost and ice buildup, improve defrosting efficiency, and reduce water retention. Here, we examine the impact of nanostructures on aluminum evaporators during frosting and defrosting inside of a 20.5 ft3 commercial food refrigerator. We use scalable manufacturing methods to generate structures on the external surfaces of the heat exchangers using bohemitization and chemical vapor deposition, rendering them superhydrophilic or superhydrophobic. Our results demonstrate a 93% reduction in water retention for the superhydrophobic heat exchanger compared to its uncoated and superhydrophilic counterparts. We conduct frosting and defrosting visualization experiments in the refrigerator to show frost pattern growth and droplet distributions on the heat exchangers. Frost was fluffier and less dense on the superhydrophobic heat exchanger compared to its counterparts which resulted in sparse droplets that are easily removed during defrosting. Furthermore, we show that the superhydrophobic heat exchanger can decrease energy consumption by 13.6% during defrosting when compared to its uncoated and superhydrophilic counterparts. We also comment on the durability of the applied coating on the heat exchangers. This study provides guidelines for the broader integration of micro and nanostructured surfaces with refrigeration and cooling appliances to create energy savings.