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ABSTRACT
Demands for higher energy efficiencies in both residential and commercial refrigeration and air conditioning systems have resulted in a trend toward coil 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 (0.20 inches) or less, significant improvements in heat transfer can be achieved. Coupled with internal enhancements to the copper tubes such as microgrooves, condenser and evaporator designs can be smaller, more efficient and operate at higher pressures to accommodate new refrigerants. Higher efficiency coils require less space and can help lower costs related to the overall packaging of a refrigeration or air conditioning system.
This paper demonstrates the impact of smaller diameter copper tubes and compares heat transfer results with common tube diameters of 7mm and above. Both simulated and actual performance data is shown as well as energy-efficient design options that are available with smaller diameter copper tubes.
Copper components also offer antimicrobial properties and these advantages are discussed. In many air conditioning and refrigeration applications, the growth of bacteria and microbes is a concern. Data from bacteria studies is shown that supports the use of copper components where antimicrobial properties are required. Recent registration of copper alloys with the U.S. Environmental Protection Agency is discussed as well.
INTRODUCTION
This paper discusses round copper tube, flat fin coils. These coils can be seen in a number of applications that cover residential, commercial and industrial settings. Typical components are condensers, evaporators and water heating coils. The histoiy of round tube, flat fin coils dates back over 100 years and today, they are being successfully modified to fit modern demands.
Heat transfer engineers face increasing requirements for energy efficiency and a push to use refrigerants that are less damaging to the atmosphere. In an effort to lower costs, there are demands for smaller, more compact systems that save on materials and refrigerants. Smaller diameter, internally enhanced copper tubing referred to as "MicroGroove(TM)" tubes, can meet these demands with minimal investment or change to well established manufacturing practices.
Recent studies and documented trials show that reducing the diameter of copper tubes improves heat transfer resulting in more energy...