Abstract
The hydrofluorocarbon (HFC) refrigerants used in the current refrigeration systems are facing a phase-down due to
their higher greenhouse effect resulting in global warming, and thus HVAC&R industry has undergone a transition
to low Global Warming Potential (GWP) refrigerants. Refrigerant mixtures are attractive alternatives since their
composition can be tailored to comply with environmental regulations while preserving favorable thermophysical
properties. However, the new low-GWP zeotropic mixture refrigerants have two or more components with different
saturation temperatures at the same pressure level, known as temperature glide, which can cause the degradation of
the overall heat transfer performance. The brazed plate heat exchangers (BPHX) provide excellent heat transfer
performance due to a compact design and are used in several air-conditioning and refrigeration applications. In this
study, flow boiling heat transfer and the associated pressure drop of the refrigerant mixture in a vertical BPHX were
experimentally investigated. The single-phase water-to-water experiments were conducted in the tested heat
exchanger with a counter-flow configuration. The flow boiling experiments charged with R-134a and R-454C were
then performed in a pumped refrigerant loop to evaluate its thermal-hydraulic performance. Furthermore, parametric
studies of various heat fluxes, mass fluxes, vapor qualities, and saturation temperatures were also conducted.
