CFD based correlation development for air side performance of finned and finless tube heat exchangers with small diameter tubes.

Number: pap. 2240



Air-to-refrigerant heat exchangers are a key component in air-conditioning and heat pump systems. A great deal of effort is spent on the design and optimization of these heat exchangers. One path towards improving their performance is the transition to smaller hydraulic diameter flow channels. This is evident by the recent introduction of microchannel heat exchangers in the stationary HVAC&R sector. Systematic analyses demonstrates a great potential for improvement in terms of size, weight, refrigerant charge and heat transfer performance by employing small diameter tubes in tube-fin heat exchangers. In particular, tube diameters below 5mm need to be investigated. The in-tube refrigerant flow characteristics are well understood for small diameter tubes and accurate heat transfer and pressure drop correlations are available in the literature. On the air side, however, most of what is available in the literature has none or very limited applicability to small tube diameter tubes. In these situations numerical methods such as CFD are commonly employed in the performance evaluation of tube and fin surfaces. Although CFD is a powerful and reliable tool, it is still computationally expensive if used for evaluating a large number of parameterized geometries. This work presents new CFD-based correlations for finned and finless tube heat exchangers for tube diameter ranging from 2mm to 5mm. The methodology implemented in this work consists of analyzing air-side heat transfer and pressure drop characteristics by using a method called Parallel Parameterized CFD (PPCFD). Maximum Entropy Design (MED) method was used to generate 500 samples to efficiently fill the design space. Multiple non-linear regression is performed to correlate the Colburn j factor and the Darcy friction f factor to the data obtained from the CFD simulations. The new correlations for bare tube heat exchangers reproduce 98.5% of the points within 10% of CFD heat transfer coefficient data and 91.9% of the points for pressure drop. Similarly, for plain fin-and-tube heat exchangers, 82.5% of the points are predicted within 15% for heat transfer coefficient and 93.2% for pressure drop.

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  • Original title: CFD based correlation development for air side performance of finned and finless tube heat exchangers with small diameter tubes.
  • Record ID : 30013259
  • Languages: English
  • Source: 2014 Purdue Conferences. 15th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2014/07/14


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