Real-world case studies highlight copper’s role in meeting HVAC/R system efficiency goals.
Market demand and global sustainability goals are encouraging HVAC/R manufacturers to innovate with more energy-efficient and environmentally responsible systems. To meet these evolving standards, engineers are rethinking heat exchanger design from the inside out, starting with the tubes that manage heat transfer and refrigerant flow.
An important focus is on minimizing the amount of refrigerant used, which contributes to lower emissions and enhances system safety. Small-diameter copper tubes are proving to be a powerful solution. Their reduced internal volume significantly cuts refrigerant charge while maintaining strong thermal performance. With excellent conductivity, mechanical strength, and long-term reliability, copper is a smart choice for high-efficiency HVAC/R systems.
Thermal Performance and System Efficiency
Copper offers thermal performance, reliability, and sustainability, making it desirable for modern heat exchanger design. With one of the highest thermal conductivities of any engineering metal, copper allows efficient heat transfer even at reduced refrigerant charge levels.
Image Courtesy of Super Radiator Coils
Based on performance comparisons, 5 mm inner-grooved small-diameter copper tubes consistently outperform larger 9.52 mm tubes (see Figure 1). These tubes can increase local heat transfer coefficients by 15 to 20 percent compared to traditional 9.52mm tubes across a range of flow conditions. The inner micro-grooves promote refrigerant mixing and boiling initiation, improving internal heat transfer while reducing the thickness of thermal boundary layers. The result is improved system efficiency in a smaller footprint, achieving optimal performance with less refrigerant.
Figure 1. Local heat exchange coefficients for 9.52mm and 5mm inner-grooved copper tubes for different mass flow, indicating 15 – 20 percent improvement with 5mm tube.
Additionally, 5mm copper tubes contribute to lower system pressure drop, improving flow characteristics and reducing compressor load. Their compact size also enables lighter, more flexible system designs with less airside resistance, improving airflow efficiency and supporting lower-energy fans, thus improving overall system COP (Coefficient of Performance).
Durability, Sustainability, and Design Flexibility
In addition to thermal advantages, copper’s mechanical strength and natural corrosion resistance contribute to its long-term durability. These properties reduce the risk of leaks, lower maintenance requirements, and extend equipment lifespan. Copper’s resistance to fatigue and degradation is significant in systems using low-GWP refrigerants, which may operate at higher pressures or require tighter tolerances.
This size and surface enhancement also directly support sustainability goals. Reducing internal volume leads to lower refrigerant charge requirements of up to 50 to 60 percent compared to standard configurations without forfeiting capacity. This is most valuable when using low-GWP refrigerants, many of which are A2L (mildly flammable) or A3 (flammable). Smaller tubes help limit total refrigerant volume, which improves safety and simplifies compliance with flammability and toxicity thresholds under emerging regulations.
Copper is also fully recyclable without degradation, supporting sustainable material use and contributing to circular economy strategies. Its established supply chain and material stability further enhance its long-term viability for manufacturers and end users.
Beyond its material properties, copper allows for design flexibility. It can be manufactured in precise, small-diameter tubes while maintaining structural integrity. These compact dimensions allow for the creation of smaller, lighter coils that fit within tight spatial constraints without compromising performance. Unlike aluminum microchannel heat exchangers, which often require large batch fabrication, copper tube systems offer more adaptability for customized or variable production scales.
Case Studies
The Copper Development Association partners with OEMs to prototype and optimize copper-based solutions by providing access to technical consultants, simulation tools, and performance testing resources. Through partnerships with research organizations, such as Optimized Thermal Solutions (OTS), CDA helps evaluate heat exchanger configurations, improve manufacturability, and refine copper tube designs to meet specific performance goals.
LU-VE
In collaboration with Optimized Thermal Systems (OTS R&D), LU-VE conducted a comprehensive analysis comparing traditional ⅜ inch small-diameter copper tubes, 5 mm copper tubes, and aluminum microchannel configurations. The goal was to maintain performance while maintaining refrigerant charge. The 5 mm small-diameter tube configuration stood out by reducing internal volume by approximately 50% compared to the baseline and outperforming microchannel alternatives (when factoring in the required larger headers for aluminum designs. This design improved refrigerant efficiency, system weight, and environmental impact, offering a holistic improvement in heat exchanger design.
Whirlpool
In response to refrigerant transition challenges, Whirlpool partnered with OTS R&D and the Copper Development Association to reevaluate and redesign evaporator and condenser coils. Their analysis of over 55,000 design variations led to the adoption of small-diameter copper tubes, which demonstrated superior heat transfer performance across all critical metrics. The optimized copper coils allowed for enhanced efficiency and better system performance while aligning with changing environmental standards and refrigerant regulations. This further demonstrated copper’s adaptability and high-performance potential in HVAC applications.
GE Appliances
In another study, GE Appliances partnered with OTS R&D and explored using small-diameter copper tube heat exchangers in their packaged terminal air conditioner (PTAC) systems. Using CoilDesigner® simulation software, the team aimed to reduce material costs and airside pressure drop while maintaining thermal performance within strict geometric constraints. The redesigned copper coils demonstrated up to 47% material cost savings, 15% reduction in airside pressure drop, and an outstanding 58% decrease in internal volume compared to the baseline designs. A second optimization phase, exploring new fin geometries, achieved up to 50% cost savings and 62% internal volume reduction. These improvements were achieved without compromising refrigerant pressure drop, and even validated that high-performance designs could be implemented using existing manufacturing equipment.
Moving Forward with Proven Benefits
Advancements in HVAC/R design are increasingly focusing on materials that balance efficiency, safety, and sustainability, making small-diameter copper tubes a leading choice for high-performance, regulation-ready heat exchanger solutions. As case studies continue to validate their benefits across real-world applications, copper remains a proven, adaptable solution for engineers and manufacturers facing tightening regulations and rising expectations.
CDA is helping OEMs, engineers, and product teams navigate this shift with technical support, material expertise, and real-world data on 5mm and 7mm copper coil performance.
CDA also offers tailored support for your projects. To learn more about what it means to partner with CDA, visit https://info.copper.org/how-to-partner-with-cda.