Vertical forced convective boiling of refrigerant binary mixtures

The present research focused on the forced convective boiling heat transfer of a binary mixture of refrigerant R 12/R 114. The test section is an industrial stainless steel pipe (AISI 316), circular duct, uniformly heated (Joule effect) over a length of 2 300 mm, with an inner diameter of 7.57 mm and a wall thickness of 0.975 mm. The test section instrumentation consists of 0.5 mm, K-type insulated thermocouples distributed along the tube on the wall and inside the channel, and connected to give directly, at each location, the temperature difference between the wall and the bulk fluid. The fluid flow is upwards, with subcooled inlet conditions. The experiments were performed using three different mixture compositions, four different pressures ranging between 1.0 and 2.5 MPa, three specific mass flow rates between 500 and 1500 kg.m⁻².s⁻¹ and three heat fluxes between 18 and 40 kW.m⁻². The experimental results show a relevance of the heat transfer regime identification in the evaluation of mixture heat transfer performance as referred to the pure components.