Demands for higher energy efficiencies in both residential and commercial refrigeration and air conditioning systems have resulted in a trend toward heat exchanger designs that are more compact with higher capacities for heat transfer. Traditional copper tube/aluminum fin coil manufacturing technology remains prevalent throughout the industry and, when modified for smaller diameter copper tubes of 5mm or less, significant improvements in heat transfer can be achieved. When coupled with internal enhancements to the copper tubes such as microgrooves, coil designs can be smaller, more efficient and less costly. Using a commercially available heat exchanger design and simulation software and CFD modeling, this paper compares optimized 3-ton air conditioning condenser coils manufactured with small-diameter internally enhanced copper tubes against condensers with aluminum microchannel tubes. Simulated operating conditions are held constant, including refrigerant inlet pressure and temperature, as well as air flow rate and inlet temperature. Comparisons of material consumption, refrigerant charge, volume, and heat transfer performance are demonstrated. It was found that using internally enhanced copper tubes with a diameter of 5mm, condenser coils can be designed to operate with less refrigerant charge and have the potential to be lighter and more compact than commercially available, optimized aluminum coil designs with microchannel tubes.
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