A type of tubing commonly used to form evaporators and is less costly than copper is __________ tubing.

Aluminum tubing is commonly used to form evaporators due to its excellent thermal conductivity, lightweight properties, and resistance to corrosion. Compared to copper, which is often used in similar applications but comes at a higher cost, aluminum offers a more economical alternative while still providing effective heat exchange capabilities. This makes it a popular choice in refrigeration and HVAC (heating, ventilation, and air conditioning) applications where the cost of materials is an important consideration without compromising on performance.

Other materials listed, such as PVC, steel, and rubber, do not possess the same combination of thermal conductivity and lightweight characteristics that aluminum provides for evaporators. While PVC is used in plumbing and electrical applications, it lacks the necessary heat transfer properties. Steel may be more durable but is heavier and prone to rusting. Rubber is not suitable for structural tubing applications, especially where heat transfer is required. Thus, aluminum stands out as the appropriate choice in this context.