Abstract: The feasibility of internally threaded Al round tube coil applied in 4HP outdoor unit (ODU) of in residential Variable Refrigerant Flow (VRF) heat pump was studied by simulation and test, which aims to establish a design methods and improvements for replacing internally threaded copper round tube heat exchanger based on the performance and cost. The simulation and test results show that under the same operating conditions, directly replacing Φ7 mm Cu tube coil by Φ7 mm Al tube coil with the same rows (keeping other structural not be changed, such as the tube spacing, row spacing, fin spacing, flow paths, etc.), the cooling energy efficiency is reduced by 2.2% on average, and the heating energy efficiency is reduced by 1.8% on average, which can be improved by increasing its heat exchanger area, adjusting the flow path design, and improving its expansion tube process or modifying its internal thread profile.

Key words: Internally threaded Al round tube coil, Performance, Cost, Residential VRF