Falling Film Transitions on Horizontal Enhanced Tubes: Effect of Tube Spacing

Vapor Shear Effects on Falling-Film Mode Transitions Between Horizontal Tubes

A liquid falling between horizontal tubes can take the form of droplets, jets, or a continuous sheet mode, depending on the flow rate. The so-called falling-film flow regime is important to heat and mass transfer, and to maintaining wetted-surface conditions in a falling-film tube bundle, and the performance of such tube bundles is important in many air-conditioning systems. In this paper, we r...

Falling film evaporation on horizontal tubes with smooth and structured surfaces

Flow Patterns and Mode Transitions for Falling-Film on Flat Tubes

The transitional Reynolds numbers for different patterns are available and a proposed transitional map is also provided in this paper. The transition of falling-films on flat tubes is studied in this work. Water and ethylene glycol are used as working fluids, for falling-film experiments conducted under adiabatic conditions, without an imposed vapor flow. The flow patterns are recorded using a ...

Dominant Flow Mechanisms in Falling-Film and Droplet Mode Evaporation Over Horizontal Rectangular Tube Banks

Flow visualization with high-speed video of evaporating water films falling over flat horizontal tubes, representative of the external surfaces of microchannel tubes, is presented. Experiments were conducted with 1.4 mm thick and 27 mm tall tubes over a film Reynolds number range of 23 < Re < 126. In addition to a qualitative description of the flow mechanisms, this work quantifies key droplet ...

Inlet Temperature Effects on Sensible Heat Transfer to Falling Liquid Films on Horizontal Round Tubes

The horizontal-tube, falling film heat exchanger has advantages over flooded bundles and finds widely use in vaporcompression and absorption systems for air-conditioning and refrigeration. The effects of the liquid feeding temperature on inter-tube falling-film heat transfer behavior are investigated experimentally for distilled water, pure ethylene glycol and Dowtherm 4000. It is found that th...