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Tube-fin heat exchanger circuitry optimization for multiple airflow maldistribution profiles.

Number: pap. 2657

Author(s) : LI Z., LING J., AUTE V.

Summary

Tube-fin heat exchangers (HXs) are widely used in the HVAC&R industry. Studies have proved that by optimizing the refrigerant circuitry, heat exchanger performance can be significantly improved. Since air-to-refrigerant heat exchangers are typically confined in packaged units along with a fan, the airflow distribution on the face of the HXs is a dominant factor influencing its performance. During the heat exchanger operation as part of an air conditioner, the air flow distribution changes continuously, especially when the fan speed changes during startup and shutdown cycles. This poses a design challenge as heat exchangers are typically designed by assuming a uniform airflow rate or a single known airflow distribution profile. For each airflow profile, a typical circuitry optimization algorithm can generate a completely different optimal refrigerant circuitry. Therefore, a circuitry design that can guarantee an acceptable minimum performance under various airflow distributions is required. In the field of optimization, this is referred to as robust optimization. This paper presents a robust circuitry optimization approach. The optimization problem formulation consists of an upper-level problem and a lower-level problem. In the upper-level optimization problem, an Integer Permutation based Genetic Algorithm (IPGA) developed in previous research is used to search for the optimal circuitry. This circuitry optimization framework can effectively obtain the optimal designs and guarantee good manufacturability. In the lower-level finite search problem, several typical airflow distribution profiles obtained from experimental measurements and CFD simulations are imposed. In addition to this problem formulation with the goal of maximizing the worst case capacity, another two robust optimization problem formulations are also examined. The comparison between the optimal circuitries obtained from the proposed robust optimization approach and the optimal circuitry from single optimization under uniform airflow distribution shows that robust circuitry designs are more resilient to multiple airflow maldistribution profiles. By applying the proposed robust circuitry optimization approach on an A-type indoor unit in a real vapor compression cycle, the robust optimal circuitry can improve evaporator cooling capacity by 5.1%. and system COP by 4.8%.

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Pages: 10

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Details

  • Original title: Tube-fin heat exchanger circuitry optimization for multiple airflow maldistribution profiles.
  • Record ID : 30024705
  • Languages: English
  • Source: 2018 Purdue Conferences. 17th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2018/07/09

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