Falling Liquid Film Evaporation in Subcooled and Saturated Water Over Horizontal Heated Tubes

ABSTRACT

This paper presents an experimental study of heat transfer and film thickness behavior in falling liquid water film evaporation technology over horizontal tubes. Liquid distribution systems have also been evaluated. The experimental setup consisted of two horizontal 0.019-m OD stainless-steel tubes, 0.194 m in length. Reynolds numbers in the 160–940 range were tested in both subcooled and saturated liquid regimes. For the liquid distribution system study, several distributor geometries were tested in order to develop the least disturbed film over the tubes. An intrusive method was used for measuring the liquid film thickness in the laminar regime and the measured values were compared with the theoretical prediction computed from the Nusselt equation. An experimental heat transfer correlation was obtained and compared with previous ones obtained by other authors. In addition, the local heat transfer coefficient was observed to be always higher at the horizontal tube top region for all operational conditions (on the order of 14 kW/m²-°C). Finally, the use of a liquid storage distribution system along with the installation of a wire mesh to obtain an uniform liquid distribution for all Reynolds numbers tested.

Funding

The authors thank FAPESP (project grant 2010/10858-4), CNPq, and CAPES for the financial support.

Additional information

Notes on contributors

Beethoven Narváez-Romo

Beethoven Narváez-Romo is currently a Ph.D. candidate in the mechanical engineering program in the Mechanical Engineering Department at Escola Politécnica, University of São Paulo, Brazil. He received his M.Sc. degree in mechanical engineering (2014), and his M.B.A. in renewable energy, distributed generation and energy efficiency (2014) from the University of São Paulo, Brazil. He is currently working in heat and mass transfer processes for an experimental ammonia–water refrigeration system at SISEA, Alternative Energy Systems Laboratory.

José R. Simões-Moreira

José R. Simões-Moreira is an associate professor of mechanical engineering in the Mechanical Engineering Department at Escola Politécnica of the University of São Paulo, São Paulo, Brazil. He is the coordinator of SISEA, Alternative Energy Systems Laboratory, in the same department. His current research interests include absorption refrigeration cycles technology, solar fuel production, and alternative energy sources and usage.