A state-of-the-art review of horizontal-tube, falling film evaporation is presented; the review is critical, in an attempt to uncover strengths and weaknesses in prior research, with the overall purpose of clearly identifying gaps in our understanding. The review covers flow-pattern studies, and the experimental parameters that affect the heat transfer performance on plain single tubes, enhanced surfaces and tube bundles. In addition, this paper presents a comprehensive review of the significant efforts to develop mathematical models, and empirical correlations for the heat transfer coefficient. Emphasis is placed on studies that are related to refrigeration applications.

Falling-film evaporation on horizontal tubes—a critical review

Film thickness measurement techniques applied to micro-scale two-phase flow systems

Refrigerant falling film evaporation review: Description, fluid dynamics and heat transfer

Review of two-phase flow instabilities in macro- and micro-channel systems

Measurement on falling film thickness distribution around horizontal tube with laser-induced fluorescence technology

Reference LTCM-ARTICLE-2005-029doi:101115/11458017View record in Web of Science Record created on 2005-07-06, modified on 2017-05-10

Falling Film Transitions on Plain and Enhanced Tubes

In tune with the falling film evaporation heat transfer test results described in Part 1, flow visualization of the boiling process and intertube flow mode transitions from droplet to column and sheet flows have been observed, and the onset of dryout results were obtained. A new empirical approach to describe falling film evaporation with a dominance of nucleate boiling that takes into account the onset of dryout has been proposed and is applicable to plain and enhanced tubes. The method predicts most of the current local measurements for R-134a to within ±20% for conditions without dryout (the desired design condition) and has also been extended to cover conditions with partial dryout. Furthermore, a criterion for predicting the onset of dryout as a function of heat flux has also been proposed for the four types of tubes.

Falling Films on Arrays of Horizontal Tubes with R-134a, Part II: Flow Visualization, Onset of Dryout, and Heat Transfer Predictions

A new optical method for the non-intrusive measurement of falling film thickness on the perimeter of horizontal tubes is described. The technique uses a high-speed digital video camera to capture the images of the liquid interface that are illuminated by a laser sheet, with the contrast enhanced by a fluorescent powder in the fluid. The results are compared to those predicted by the Nusselt falling film theory, showing relatively good agreement around the upper perimeter of the tube but much poorer agreement on the lower perimeter. The corresponding effects on heat transfer have also been estimated.

Measurement of Falling Film Thickness Around a Horizontal Tube Using a Laser Measurement Technique

A new falling film heat transfer test facility has been built for the measurement of local heat transfer coefficients on a vertical array of horizontal tubes, including flow visualization capabilities, for use with refrigerants. Presently, the facility has been used for evaporation tests on four types of tubes at three tube pitches and three nominal heat flux levels for R-134a at 5°C. A new method for determining local heat transfer coefficients using hot water heating has been applied, and test results for a wide range of liquid film Reynolds numbers have been measured for arrays made of plain, Turbo-BII HP, Gewa-B, and High-Flux tubes. The results show that there is a transition to partial dryout as the film Reynolds number is reduced, marked by a sharp falloff in heat transfer. Above this transition, the heat transfer coefficients are nearly insensitive to the film Reynolds number, apparently because vigorous nucleate boiling is always seen in the liquid film. The corresponding nucleate pool boiling da...

J. F. Roques

Papers

Falling Film Transitions on Plain and Enhanced Tubes

Falling Films on Arrays of Horizontal Tubes with R-134a, Part II: Flow Visualization, Onset of Dryout, and Heat Transfer Predictions

Measurement of Falling Film Thickness Around a Horizontal Tube Using a Laser Measurement Technique

Falling Films on Arrays of Horizontal Tubes with R-134a, Part I: Boiling Heat Transfer Results for Four Types of Tubes