Cycle performance of air conditioning system based on finned tube heat exchangers with different helix angles

The cycle performance of the novel 5 mm outer diameter (OD) finned tube heat exchangers (FTHX) with different helix angles (1°, 6°) were investigated as indoor unit in split air conditioning systems to be compared with those of the conventional indoor ones (5 mm and 7 mm FTHX with helix angle of 18°). Conventional T-splitter of the outdoor heat exchanger (HX) was afterward replaced by a Y-splitter and numbers of U-tubes in the two bypasses were adjusted to balance the heat exchange amount of two different bypasses. At first, experimental results showed that the 5 mm system with helix angle of 6° was superior to those 5 mm systems with helix angles of 1° and 18° but still inferior to the conventional 7 mm system, in aspects of capacity and coefficient of performance (COP) both in cooling and heating mode. But after the adjustments, performance of the 5 mm system with helix angle of 6° experienced a 1.5% and 0.7% higher capacity both in cooling and heating mode, respectively, and a 1.7% higher heating COP in spite of a 0.7% lower cooling COP. The system adopting the 5 mm tubes with the helix angle of 6° after adjustments is demonstrated that it can commendably ease material pressure and meanwhile promote the cycle performance.