Two-phase flow distribution of saturated refrigerants in microchannel heat exchanger headers

Abstract

Mini- and microchannel heat exchangers have the potential to drastically decrease the size and cost of thermal systems, but they often underperform because of flow maldistribution. Maldistribution can be particularly acute when a two-phase mixture enters a heat exchanger header, which is difficult to address because the flow phenomena in these situations are poorly understood. In the present study, flow distribution in microchannel heat exchanger manifolds is investigated. The work focuses on two-phase flow regimes and distribution characteristics of saturated R134a in heat exchanger headers. The results quantify the effects of inlet mass flux (23.9 < Gin < 95.7 kg m−2 s−1), inlet quality (0.10 < xin < 0.90), header flow regime and header pressure drop on distribution. Additionally, several header geometries (rectangular, triangular, and vane) are investigated to identify pathways to mitigate maldistribution in heat exchangers.