Transition boiling of a fluid is characterized by a stochastic change between liquid and vapour contact on the heated wall. A control system for electrically heated test sections, the so-called dither technique, is applied to carry out steady state temperature controlled experiments in the transition region. As a test fluid refrigerant R114 is used flowing upward in a vertical nickel tube with 14 mm inside diameter. Experimental parameters are: pressure, 2.5 ≤p (bar)≤20(0.076 ≤ p/pc≤ 0.061); mass flux, 500 ≤ dot m (kg m-2s-1) ≤ 3000 and quality:≤ dot x ≤0.2. The pressure is the relevant parameter for the heat flux in the transition region, whereas the mass flux and the quality are of minor importance. Hence, transition boiling can be calculated in a similar way as nucleate boiling, namely by a simple exponential law: α=C dot qn. Based on a comparison of the present results with data from the literature, two universal methods to predict heat transfer in transition boiling are proposed. The two methods are, in most practical cases, applicable to natural and forced convection conditions. © 1988.
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