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Manufacturing & testing of air-to-refrigerant heat exchangers based on 0.8mm diameter tubes.

Number: pap. 2289

Author(s) : SHABTAY Y., HUANG Z., AUTE V., et al.

Summary

Recent research has shown that moving towards small tubes with diameters less than 5 mm brings significant advantages in air-to-refrigerant heat exchangers (HX). These advantages include compactness, high airside heat transfer coefficient, reduced refrigerant charge and reduced weight. Tubes with outer diameter (OD) of 0.8 mm were shown to provide very high heat transfer coefficient resulting in heat exchanger with a high degree of compactness. However, using such small tube diameter comes with manufacturing and field performance challenges. Those include the management of many hundreds of small tubes, developing a method to ensure that a specific gap between the tubes at any given point is kept, maintaining the desired geometrical shape of the complete heat exchanger and sealing the tube to header joints, which is the biggest challenge. Field challenges include areas such as fouling and water drainage. This paper presents the lessons learned from manufacturing and testing of air-to-refrigerant heat exchangers that use such 0.8 mm OD tubes. Three prototypes were manufactured, the first one was made of stainless steel (SSHX), the second one was made of copper (CuHX) and the third one was a larger version of the second prototype (CuHX-10kW). The first and second HX were designed to have the same pressure drop and heat transfer performance. These prototypes were fabricated using different manufacturing techniques and lessons learned were discussed. One of the observations is that the uncertainty in tube spacing due to manufacturing has a significant impact on the performance. This points to the need for robust optimization methods in design of such heat exchangers for which the manufacturing technologies are still being developed. Hydrostatic tests as well as performance tests in a closed loop wind tunnel were conducted. Test results for the three heat exchangers using air and water are discussed. The energy balances were within ±5% and uncertainties in averaged capacity were within ±3% for the three prototypes.

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Pages: 8

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Details

  • Original title: Manufacturing & testing of air-to-refrigerant heat exchangers based on 0.8mm diameter tubes.
  • Record ID : 30018859
  • Languages: English
  • Source: 2016 Purdue Conferences. 16th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2016/07/11

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