Identification of condensation flow regime at different orientations using temperature and pressure measurements

• Published in: International journal of heat and mass transfer 2019-06, Vol.135, p.569-590
• Main Authors: O'Neill, Lucas E., Balasubramaniam, R., Nahra, Henry K., Hasan, Mohammad M., Mackey, Jeffrey R., Mudawar, Issam
• Format: Article
• Language: English
• Subjects: Advection; Annular flow; Axisymmetric flow; Condensation; Flooding; Flow condensation; Flow regime determination; Flow regime maps; Horizontal orientation; Orientation effects; Plug flow; Pressure oscillations; Slug flow; Standard deviation; Stratified flow; Thermocouples
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2019.01.133

•Experiments investigate pressure and temperature oscillations in flow condensation.•Amplitude of oscillations evaluated for vertical and horizontal orientations.•Flow regimes identified for the different orientations.•Key differences seen when comparing results across orientations.•Recent flow regime maps evaluated for predictive accuracy. While many prior works in the field relied upon direct optical access to determine condensation flow regimes, the present work outlines a new methodology utilizing temperature and pressure measurements to identify condensation flow regimes. For vertical upflow condensation, amplitude of dynamic temperature and pressure oscillations are shown to clearly indicate transition from counter-current flow regimes (i.e., falling film, oscillating film, flooding) to annular, co-current flow (climbing film flow regime). In horizontal flow condensation, standard deviation between multiple thermocouple measurements distributed around the tube circumference was calculated at all axial (stream-wise) measurement locations. High values of standard deviation are present for stratified flow (stratified flow, wavy-stratified, plug flow), while axisymmetric flow regimes (i.e., slug flow, annular flow) yield significantly lower values. Successful development of this technique represents a valuable contribution to literature as it allows condensation flow regime to be identified without the often-costly restriction of designing a test section to allow optical access. Identified flow regimes in both vertical upflow and horizontal flow orientations are compared to regime maps commonly found in the literature in pursuit of optimum performing maps.