Narrowing Copper Tube Diameter to 4 mm: Xi'an Research Confirms 17% Cost Reduction Without Efficiency Loss
Professor Qian Suxin's team at Xi'an Jiaotong University presented findings at the 2026 China Home Appliance Technology Conference showing that optimizing a 1.5 HP outdoor heat exchanger from 5 mm to 4 mm tubes reduces copper cost by 17% and refrigerant charge by 95 g while maintaining heat exchange capacity and APF. The authors estimate that the 3–3.5 mm range may become the next critical threshold, though design and manufacturing complexity increases.
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