Flow pattern and experimental investigation of heat transfer coefficients during the condensation of r134a at low mass fluxes in a smooth horizontal tube.

Show simple item record

dc.contributor.author Ewim, D.R.E. en
dc.contributor.author Kombo, R. en
dc.contributor.author Meyer, Josua P. en
dc.date.accessioned 2017-08-28T07:07:20Z
dc.date.available 2017-08-28T07:07:20Z
dc.date.issued 2016 en
dc.description Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016. en
dc.description.abstract An experimental study of heat transfer and flow pattern visualisation during the condensation of R134a was conducted in a smooth horizontal tube at low mass fluxes. Most previous experimental and analytical studies on in-tube condensation were conducted at high mass fluxes. In these studies, it was found that the heat transfer coefficient was not a function of the temperature difference between the tube wall temperature and condensation temperature. In addition, most heat transfer models developed were for high mass fluxes and failed to predict heat transfer coefficients at low mass fluxes properly. However, the most recent predictive heat transfer models have been based on studying and analysing the flow patterns. In all of these, only very few experimental studies have been coupled with flow pattern identification at different controlled temperature differences and mean vapour qualities at low mass fluxes. Therefore, the purpose of this study was the investigation of R134a condensing at low mass fluxes (20 –100 kg/m2s) and the identification and analysis of the flow patterns observed. The experiments were conducted in a smooth horizontal tube 8.38 mm in internal diameter with a length of 1.5 m at different mean vapour qualities and controlled temperature differences. The average saturation temperature was maintained at 40°C. The flow patterns were recorded simultaneously with a high speed video camera at the inlet and outlet of the test section through transparent sight glasses. The results showed that stratified flow and stratified-wavy were the dominant flow patterns. Stratification would differ with decreasing flow rate of the refrigerant. As the flow rate decreased, the liquid layer at the bottom of the tube increased. The study also revealed the effect of temperature difference between the tube wall and the saturation temperatures with respect to the heat transfer coefficient at low mass flow rates of the refrigerant. The higher the temperature difference, the lower the heat transfer coefficient. en
dc.format.extent 6 pages en
dc.format.medium PDF en
dc.identifier.uri http://hdl.handle.net/2263/61820
dc.language.iso en en
dc.publisher HEFAT en
dc.rights University of Pretoria en
dc.subject Heat transfer en
dc.title Flow pattern and experimental investigation of heat transfer coefficients during the condensation of r134a at low mass fluxes in a smooth horizontal tube. en
dc.type Presentation en


Files in this item

This item appears in the following Collection(s)

Show simple item record