Internally grooved copper tubes are a small diameter coil technology for modern air conditioning and refrigeration systems. Grooved coils facilitate more efficient heat transfer than smooth coils. Small diameter coils have better rates of heat transfer than conventional-sized condenser and evaporator coils with round copper tubes and aluminium or copper fin that have been the standard in the HVAC industry for many years. Small diameter coils can withstand higher pressures required by the new generation of environmentally friendlier refrigerants. They have lower material costs because they require less refrigerant, fin, and coil materials. And they enable the design of smaller and lighter high-efficiency air conditioners and refrigerators because the evaporators and condensers coils are sma