Abstract
Microchannel heat exchangers find widespread use in household and automotive air conditioning due to their compact structure and high efficiency. However, two-phase refrigerant flow mal-distribution in microchannels limits their application. For the CO2 heat pump, the performance reduction by flow mal-distribution could be as large as 20%. This study proposed an approach to mitigate flow mal-distribution by inserting a perforated tube into the header of a microchannel evaporator in CO2 heat pump. Numerical simulations were carried out to investigate the impact of perforated tube parameters and CO2 inlet conditions on flow distribution. Results show a 24.4% increase in total non-uniformity (S) of flow distribution with a perforated tube. A higher number of openings and smaller diameters enhance uniformity, with the 10-hole, 2 mm diameter perforated tube proving most effective. Additionally, the most uniform flow distribution was achieved at an inlet CO2 mass flow rate of 30 g/s and a vapor quality of 0.2. And the flat tubes with an insertion depth of 5 mm and a cross-section of 16 × 2 mm is the most beneficial for uniform flow distribution.
Disclosure statement
No potential conflict of interest was reported by the author(s).