Design and Manufacturing of High Performance, Reduced Charge Heat Exchangers

Technical Report · Mon Feb 12 04:00:00 EST 2024

DOI:https://doi.org/10.2172/2293536· OSTI ID:2293536

Radermacher, Reinhard ^[1]; Aute, Vikrant ^[2]; Hwang, Yunho ^[2]; Muehlbauer, Jan ^[2]; Tancabel, James ^[2]; Klein, Ellery ^[2]; Lee, Cheng-Yi ^[2]; Shabtay, Yoram ^[3]; Black, John ^[3]; Carmeli-Shabtay, Naomi ^[3]; Zhang, Mingkan ^[4]; Shen, Zhenglai ^[4]

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1. Univ. of Maryland, College Park, MD (United States); University of Maryland
2. Univ. of Maryland, College Park, MD (United States)
3. Heat Transfer Technologies, LLC, Prospect Heights, IL (United States)
4. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Air-to-fluid heat exchangers (HXs) play a critical role as the main heat transfer component in Heating, Ventilation, Air-Conditioning, and Refrigeration (HVAC&R) systems. However, their airside thermal resistance significantly inhibits their overall performance. Furthermore, these HXs must be continually more compact to meet the latest refrigerant charge limits to reduce emissions. Recent literature suggests that traditional HX geometries (e.g., round or flat tubes with fins), have reached their limits, and more sophisticated shape- and topology-optimized designs are required to achieve the next jump in performance. This research sheds light on the next generation of air-to-refrigerant HXs and aims to address several practical issues to commercialization such as novelty challenges (improved performance for significant charge reduction; modeling expertise & time investment), manufacturing challenges (non-round tube manufacturing; tube-header integration; product qualification, e.g., burst pressure testing, extreme operational environment, etc.), and operational challenges (flow maldistribution, fouling & wetting, noise & vibration). For example, a >20% improvement on one (or more) HX-level performance metrics (e.g., envelope volume, airside pressure drop, face area, capacity, refrigerant charge, weight, cost, etc.) must be achieved before a HX design is considered for commercialization. We present a new, comprehensive and experimentally validated air-to-refrigerant HX optimization framework with simultaneous thermal-hydraulic performance and mechanical strength considerations for novel, non-round, shape- and topology-optimized tubes capable of optimizing single and two-phase HX designs for any refrigerant choice and performance requirement with significant engineering time savings compared to conventional design practices. The framework was exercised for a wide range of applications and refrigerants, resulting in HXs which achieved greater than 20% improved performance, 20% reductions in size, and 25% reductions in refrigerant charge. To enable non-round tube bundle use in next generation HVAC&R equipment, novel manufacturing techniques were investigated, including the development of conventional manufacturing methods for small diameter, non-round tubes and novel tube-header integration strategies. In total, ten HX prototypes were manufactured, nine using conventional methods directly attributed to this project and one using advanced additive manufacturing methods. The five-year manufacturing feasibility of the proposed HXs was found to have a good outlook. The non-round tube HX simulated performance was validated through comprehensive experimental testing, including nine in-house component-level tests, one independent component-level test at an industry partner laboratory, and in-house system-level tests of using a commercially-available, residential packaged A/C unit which was retrofitted with a non-round tube prototype HX. It was found that HX designs proposed by the new framework can successfully predict experimental thermal-hydraulic performance within ±10-20% the first time with no manual design changes, eliminating the need for time-consuming and expensive prototyping efforts. This work will accelerate design and time to market for next generation HXs while simultaneously facilitating industry transition to new refrigerants at lower charge.

• Research Organization: Univ. of Maryland, College Park, MD (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Building Technologies Office
• DOE Contract Number: EE0008221
• OSTI ID: 2293536
• Report Number(s): DOEBTO-UMD--8221-24-FTR-01
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
CFD
FEA
HVAC
aeroacoustics
air-to-refrigerant
approximation
condenser
dehumidification
evaporator
fatigue analysis
genetic algorithm
heat exchanger
internal flow
manufacturing
mechanical
multi-physics
multiscale
optimization
refrigerant
shape optimization
system-level analysis
thermal-hydraulic performance