Evaporation heat transfer of thin liquid film and meniscus in narrow and circumferential crevices of micro scale

This study experimentally investigated the flow pattern, void fraction, and evaporation heat transfer characteristic of R134a upward flow in a vertical narrow rectangular channel having a hydraulic diameter of 0.99[Formula: see text]mm, resembling a plate heat exchanger. Experiments were performed with mass velocities and vapor quality ranging between 30–200[Formula: see text]kgm[Formula: see text]s[Formula: see text] and 0.05–0.9, respectively, at a saturation temperature of 15[Formula: see text]C. Flow patterns were classified into bubble, slug, churn, and annular flows. The void fraction increased with increasing quality, and decreased with decreasing mass velocity in the low-quality region. Further, the influence of flow inlet/outlet positions remarkably appeared when the superficial gas velocity was low. The observed flow patterns and the measured void fraction were compared to that in previous studies. The effects of mass velocity and heat flux on the evaporation heat transfer coefficient were small, and the heat transfer through the thin liquid film was dominant.

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Molecular dynamics simulations of the liquid film evaporation heat transfer on different wettability hybrid surfaces at the nanoscale

Journal of Molecular Liquids ◽

10.1016/j.molliq.2020.113610 ◽

2020 ◽

Vol 314 ◽

pp. 113610 ◽

Cited By ~ 2

Author(s):

Qun Cao ◽

Wei Shao ◽

Xiaohan Ren ◽

Xiaoteng Ma ◽

Kun Shao ◽

...

Keyword(s):

Heat Transfer ◽

Molecular Dynamics ◽

Liquid Film ◽

Molecular Dynamics Simulations ◽

Film Evaporation ◽

Evaporation Heat ◽

Evaporation Heat Transfer ◽

Dynamics Simulations

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Experimental Study of Tube Row Effects on Evaporation Heat Transfer Using a Micro-Scale, Porous-Layer Coating on a Horizontal-Tube, Falling-Film Heat Exchanger

ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2012-75333 ◽

2012 ◽

Cited By ~ 1

Author(s):

Batikan Köroğlu ◽

Nicholas Bogan ◽

Chanwoo Park

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Porous Layer ◽

Horizontal Tube ◽

Falling Film ◽

Solution Flow ◽

Micro Scale ◽

Evaporation Heat ◽

Evaporation Heat Transfer ◽

Layer Coating

An experimental study was conducted to investigate the effects of tube row and a micro-scale porous-layer coating on solution fluid wetting and heat transfer of a horizontal-tube, falling-film heat exchanger using an inline tube arrangement. A uniform layer of micro-scale copper particles was directly bonded onto plain copper tubes by sintering to create a porous-layer coating on the tubes. Distilled water was used as solution and heating fluids. The visual observation performed in open ambient condition revealed that when the solution was dripped onto horizontal tubes from a solution dispenser, the conventional plain tubes were always partially wetted while the porous-layer coated tubes were completely wetted due to capillary action, even at low solution flow rates. It was shown from the comparison of the evaporation heat transfer results of the plain and porous-layer coated tubes tested in a closed chamber under saturated conditions that the porous-layer coated tubes exhibited a superior evaporation heat transfer rate (around 70% overall improvement at low solution flow rates) due to the complete solution wetting and thin solution liquid film on the evaporator tubes. It was also observed that the heat transfer and surface wetting of the horizontal-tube, falling-film heat exchanger are greatly affected by both the flow mode of the solution fluid between the tubes and tube wall superheats. The effect of the tube row of the falling-film heat exchanger on the solution wetting and heat transfer was significant.

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