Pool Boiling Heat Transfer Characteristics of Propylene Glycol, Glycerol, and Their Mixtures

Abstract Boiling phase change phenomena of propylene glycol (PG), glycerol (Gl), and their mixtures are of great interest in many engineering and industrial applications dealing with high heat flux systems. Examples include heating, ventilation, and air conditioning systems, corrosion controls, and food, pharmaceutical, entertainment, and vape industries. However, a systematic assessment of their heat transfer performance from a heating element to surrounding fluids remains obscure. In this study, heat transfer characteristics of pure PG, Gl, and three different PG–Gl mixtures, i.e., 30PG/70Gl, 50PG/50Gl, and 70PG/30Gl, are investigated by conducting pool boiling experiments. Pure PG and Gl show up to about 49% lower critical heat flux (CHF) than de-ionized water (DW). Gl has a higher heat transfer coefficient compared to PG or DW in the nucleate boiling regime, indicating an enhanced heat transfer performance. Mixing of PG and Gl significantly affects the solution's CHF and heat transfer coefficient due to changes in characteristic properties of a binary mixture. The boiling mechanism is further examined by high-speed imaging of bubble formation. This study provides comprehensive data, which are useful to operate PG- and/or Gl-based boiling equipment or processes more efficiently.