Two-phase flow distribution in a refrigerant distributor having four indoor-unit connections of a variable refrigerant flow system

Abstract

Abstract In a variable refrigerant flow (VRF) system, the refrigerant is supplied from one outdoor unit to multiple indoor units through a header or refrigerant distributor. When the two-phase refrigerant flows into the distributor, uneven distribution occurs and deteriorate system performance. An experimental apparatus simulating the refrigerant distributor of a VRF system was constructed and air-water two-phase flow distribution characteristics were investigated. The air-water two-phase flow was more mal-distributed as the void fraction increased. A change in void fraction affected the distribution more than a change in mass flow rate in the experimental range. The flow distribution in the header was little affected by variation of the downstream flow resistance. Previous empirical correlations were investigated to predict the air-water two-phase flow distribution measured in this experiment, but performance was poor. To estimate the refrigerant two-phase flow distribution, computational fluid dynamics (CFD) simulations were performed using R410A as a working fluid. The mal-distribution of R410A appeared to be mitigated compared with air-water flow due to the large vapor phase density of R410A.