An experimental study on the critical heat flux (CHF) of flow boiling in a highly viscous fluid in vertical tubes

The critical heat flux (CHF) of flow boiling heat transfer in the vertical downward flow of a highly viscous fluid has been investigated for a consistency index η0 = 1.49–20.88 Pa sn, a tube diameter D = 5.34, 7.71 and 10.27 mm, a mass velocity G = 4.57–53.4 kg mm−2 s−1, an inlet quality XIN = −1.3% to 20% and a critical heat flux qC = 20.1–69.2 kW m−2. A correlation based on the CHF data has been developed which takes account of the effects of Re, Pr, Bo, 1/D and PR on CHF.