Analysis of heat transfer in horizontal tube falling film evaporators

Technical Report · Wed Mar 01 04:00:00 EST 1978

DOI:https://doi.org/10.2172/6882148· OSTI ID:6882148

Lorenz, J. J.; Yung, D.

A model of combined boiling and evaporation of liquid films on horizontal tubes was developed. Specifically, this work was directed toward developing a heat transfer model applicable to the design of horizontal tube falling film evaportors for OTEC. The heat transfer process is modelled as combined boiling and evaporation of the liquid film. In modelling the behavior of single tubes special account is taken of heat transfer in the initial thermal developing region of the film. Predictions were found to agree favorably with the published experimental data for boiling and evaporation of thin water films on single horizontal tubes. The predicted upper and lower limits of heat transfer for ammonia on a vertical bank of plain horizontal tubes are 5.4 kW/m/sup 2/-K and 3.1 kW/m/sup 2/-K, respectively. The upper limit will be approached when the influence of between-tube evaporation and turbulence created by the liquid falling from one tube to the next are important. For an OTEC evaporator with plain tubes, the upper and lower limits of the overall U are 2.33 kW/m/sup 2/-K and 1.82 kW/m/sup 2/-K, respectively. With ammonia-side boiling enhancement, the overall U can be increased to about 3.8 kW/m/sup 2/-K.

• Research Organization: Argonne National Lab., Ill. (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6882148
• Report Number(s): ANL-OTEC-78-1
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
140800* -- Solar Energy-- Ocean Energy Systems
AMMONIA
BOILING
CONVERSION
ENERGY CONVERSION
ENERGY TRANSFER
EVAPORATION
EVAPORATORS
HEAT TRANSFER
HYDRIDES
HYDROGEN COMPOUNDS
MATHEMATICAL MODELS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NUCLEATE BOILING
OCEAN THERMAL ENERGY CONVERSION
ORIENTATION
PHASE TRANSFORMATIONS
SOLAR ENERGY CONVERSION
TUBES
TURBULENCE