The surface cooler is the core component of a combined air handling unit, where heat exchange occurs between air and refrigerant. A typical surface cooler coil structure consists of aluminum fins expanded to copper tubes using an expander. The wall thickness of the copper tubes and the thickness of the aluminum foil vary slightly depending on the manufacturer, generally ranging from 0.2 to 0.6 mm in wall thickness and 7 to 16 mm in diameter, with aluminum foil thicknesses from 0.15 to 0.20 mm.
It is worth noting that different manufacturers choose significantly different fin spacings when calculating the surface cooler. For example, in a system with a handling air volume of 79,000 m³/h and a cooling capacity of 831 kW, Manufacturer A's solution involves reducing the surface cooler fin spacing (approximately 1.8 mm) to increase the heat exchange area; Manufacturer B's solution uses a conventional fin spacing (approximately 2.5 mm) and employs a two-stage surface cooler section in series to extend the heat exchange time. Both solutions have their own advantages and disadvantages in terms of fan power consumption, water resistance, and cross-sectional dimensions. The former might result in greater wind resistance, thus increasing the power consumption of the fan, while the latter might increase the size of the unit and water flow resistance. After a comprehensive technical comparison and taking cost factors into account, it was decided to use the product from Factory B.
