Development of a novel two-zone model for the heating of an evaporating liquid droplet

Thielens, Martin; Merci, Bart; Beji, Tarek

doi:10.1016/j.firesaf.2020.103019

Cited by 2 publications

(2 citation statements)

References 18 publications

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“…The literature is replete with studies on the heating and evaporation of water from single droplets suspended in high-temperature environments [6][7][8][9][10]. Strizhak et al [8] conducted a series of experiments to investigate the heating and evaporation of suspended water droplets with diameters varying from 1.8 to 3 mm in a hot air flow with temperatures up to 800 • C. Volkov and Strizhak [7] performed experiments on water droplets suspended in the air with the size ranging from 1 to 2 mm at high air temperature varying from 100 to 800 • C, and measured the evaporation rate and profile of droplet size, and recorded the time of their existence.…”

Section: Introductionmentioning

confidence: 99%

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The Behaviour of Water-Mists in Hot Air Induced by a Room Fire: Effect of the Initial Size of Droplets

Mahmud

Thorpe

Moinuddin

2022

Fire

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This paper presents work on investigating the effect of the initial size of water mist droplets on the evaporation and removal of heat from the fire-induced hot gas layer while travelling through the air in a compartment. The histories of the temperature, diameter and position of droplets with different initial diameters (varied from 100 µm to 1000 µm) are determined considering surrounding air temperatures of 75 °C and 150 °C and a room height of 3.0 m. A water droplet evaporation model (WDEM) developed in a previous study (Fire and Materials 2016; 40:190–205) is employed to navigate this work. The study reveals that tiny droplets (for example, 100 µm) have disappeared within a very short time due to evaporation and travelled a very small distance from the spray nozzle because of their tiny size. In contrast, droplets with a larger diameter (for example, 1000 µm) reached the floor with much less evaporation. In the case of this study, the relative tiny droplets (≤200 µm) have absorbed the highest amount of energy from their surroundings due to their complete evaporation, whereas the larger droplets have extracted less energy due to their smaller area/volume ratios, and their traverse times are shorter. One of the key findings of this study is that the smaller droplets of spray effectively cool the environment due to their rapid evaporation and extraction of heat from the surroundings, and the larger droplets are effective in traversing the hot air or smoke layer and reaching the floor of the compartment in a fire environment. The findings of this study might help in understanding the behaviour of water-mist droplets with different initial diameters in designing a water-mist nozzle.

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Section: Introductionmentioning

confidence: 99%

“…Sobac et al [9] developed a quasi-steady model to analyse the evaporation process of a suspended water droplet in air. Thielens et al [10] developed a two-zone model for heating an evaporating water droplet suspended and exposed to hot airflow. They used the model to predict the lifetime and saturation temperatures of droplets.…”

Section: Introductionmentioning

confidence: 99%

The Behaviour of Water-Mists in Hot Air Induced by a Room Fire: Effect of the Initial Size of Droplets

Mahmud

Thorpe

Moinuddin

2022

Fire

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An Engineering Model for Water Spray Cooling: Application to a Mechanically-Ventilated Enclosure Fire

Beji

2022

Fire Technol

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The paper presents a simplified engineering model for the prediction of the rate of heat absorption by heat-up and evaporation of water droplets interacting with fire-induced smoke.The algorithm can be easily implemented in the framework of one-zone or two-zone fire models. The general methodology is based on a decoupled time scale analysis for the heating, evaporation and motion of a single droplet. Such analysis allows to determine the heat absorbed by a droplet during its residence time in the smoke layer. Under the assumption of a monodisperse spray, the injected number of droplets per second is calculated and used to estimate the rate of heat absorption (i.e., cooling) by a full spray. The assessment of the model, for single droplet as well as full spray calculations, has been carried out against results obtained with the Fire Dynamics Simulator (FDS 6.7.0). The results show that the model predicts the rate of heat absorption within 15 % for droplet diameters between 0.4 mm and 0.8 mm and a surrounding gas temperature below 150°C. Larger deviations are observed under other conditions. The application of the model to a well-confined and mechanically-ventilated compartment fire (a scenario of relevance to nuclear installations and passive houses) allowed to provide a good estimate of the cooling rate of the water spray system and the subsequent average gas temperature and pressure profile within the room.

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Development of a novel two-zone model for the heating of an evaporating liquid droplet

Cited by 2 publications

References 18 publications

The Behaviour of Water-Mists in Hot Air Induced by a Room Fire: Effect of the Initial Size of Droplets

The Behaviour of Water-Mists in Hot Air Induced by a Room Fire: Effect of the Initial Size of Droplets

An Engineering Model for Water Spray Cooling: Application to a Mechanically-Ventilated Enclosure Fire

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