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3 and 5mm copper tube fin heat exchangers: continued testing and frost developing characteristics.

Number: 2159

Author(s) : NASUTA D., LI S., HONG R.

Summary

The inverse relationship between tube diameter and compactness is well-established in tube-fin heat exchangers. For multiple decades, designers have implemented smaller-diameter tubes in heat exchangers (HXs) as a solution to improve performance, reduce refrigerant charge, and reduce cost. While products with 5mm OD tubes have become prevalent in the industry, diameters less than 5mm remain uncommon. A question remains: are further reductions in tube diameter worthwhile? Past work has demonstrated that 3mm copper tube and aluminum fin designs are capable of considerable improvements in thermal-hydraulic performance, compactness, and material utilization. These optimized designs were verified with first-in-kind 3mm tube-fin prototypes that were tested experimentally and compared with equivalent 5mm designs. While the findings confirmed the optimality of 3mm designs, the prototypes were not built exactly within specifications for FPI. In this work, new prototypes with slightly different dimensions were constructed and tested. The results again validate the accuracy of CFD-based correlations developed for 3-5mm OD tube-fin heat exchangers and demonstrate further performance advantage for the 3mm relative to 5mm baseline.
In addition to this validation, sample heat exchangers were tested in wet (dehumidification) conditions as well as lower temperature tests where frost formation occurred. Two copies of each 3 and 5mm coil were tested: an original baseline heat exchanger and an identical copy with a hydrophobic coating applied. This work compares differences in behaviors in wet and frosting conditions for the two tube diameter samples with and without coatings. Frosting test results showed more rapid frost formation of 3mm samples due primarily to the fact that they use a higher fin density than their 5mm counterparts. While this disadvantaged performance in frost-forming conditions may preclude their use in some refrigeration and heat pumping applications, test results also indicated that a coating may significantly extend the operating time of 3 and 5mm heat exchangers alike.

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  • Original title: 3 and 5mm copper tube fin heat exchangers: continued testing and frost developing characteristics.
  • Record ID : 30030500
  • Languages: English
  • Subject: Technology
  • Source: 2022 Purdue Conferences. 19th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2022/07/10

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