Effect of the Flow Velocity of Gas on Liquid Film Flow in a Vertical Tube

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216305%3A26210%2F20%3APU137019" target="_blank" >RIV/00216305:26210/20:PU137019 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.aidic.it/cet/20/81/136.pdf" target="_blank" >https://www.aidic.it/cet/20/81/136.pdf</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.3303/CET2081136" target="_blank" >10.3303/CET2081136</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Effect of the Flow Velocity of Gas on Liquid Film Flow in a Vertical Tube

Popis výsledku v původním jazyce

When gas flows inside a vertical tube in which a thin liquid film runs down its wall, interfacial shear stress occurs at the gas-liquid interface. This stress is caused by the imperfectly smooth surface of the film running down. For intensification of heat transfer in heat exchangers where the vapour condenses, it is necessary to pay attention not only to the thickness of the liquid film on heat exchange surface, but also the character of the liquid film. This paper describes the influence of a gas flow velocity on a liquid film flow. The gas velocity effect is examined for a constant thickness of the liquid film. When the velocity of the gaseous medium changes, it is necessary to increase or decrease the liquid flow in order to keep the film thickness constant. The effect of shear stress is described for three different inner tube diameters (15.0, 20.0, and 25.0 mm) and for three different theoretical film thicknesses derived from the Nusselt criterion. The results are compared with theoretical, analytical relationships. In all the three tube diameters tested, the influence of the gas velocity is the most significant at low speeds, where the deviation from the theoretical course is the greatest. As the tube diameter decreases, the shear stress effect increases. At higher speeds of the gas and liquid film flow, pulsations start to occur, the film flow stops increasing, and the trend follows the theoretical, analytical relationships published in the professional literature.

Název v anglickém jazyce

Effect of the Flow Velocity of Gas on Liquid Film Flow in a Vertical Tube

Popis výsledku anglicky

When gas flows inside a vertical tube in which a thin liquid film runs down its wall, interfacial shear stress occurs at the gas-liquid interface. This stress is caused by the imperfectly smooth surface of the film running down. For intensification of heat transfer in heat exchangers where the vapour condenses, it is necessary to pay attention not only to the thickness of the liquid film on heat exchange surface, but also the character of the liquid film. This paper describes the influence of a gas flow velocity on a liquid film flow. The gas velocity effect is examined for a constant thickness of the liquid film. When the velocity of the gaseous medium changes, it is necessary to increase or decrease the liquid flow in order to keep the film thickness constant. The effect of shear stress is described for three different inner tube diameters (15.0, 20.0, and 25.0 mm) and for three different theoretical film thicknesses derived from the Nusselt criterion. The results are compared with theoretical, analytical relationships. In all the three tube diameters tested, the influence of the gas velocity is the most significant at low speeds, where the deviation from the theoretical course is the greatest. As the tube diameter decreases, the shear stress effect increases. At higher speeds of the gas and liquid film flow, pulsations start to occur, the film flow stops increasing, and the trend follows the theoretical, analytical relationships published in the professional literature.

Druh

J_SC - Článek v periodiku v databázi SCOPUS

CEP obor

—

OECD FORD obor

20704 - Energy and fuels

Projekt

<a href="/cs/project/EF16_026%2F0008392" target="_blank" >EF16_026/0008392: Výpočtové simulace pro efektivní nízkoemisní energetiku</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2020

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Chemical Engineering Transactions

ISSN

2283-9216

e-ISSN

—

Svazek periodika

81

Číslo periodika v rámci svazku

2020

Stát vydavatele periodika

IT - Italská republika

Počet stran výsledku

6

Strana od-do

811-816

Kód UT WoS článku

—

EID výsledku v databázi Scopus

2-s2.0-85092019388