Experimental study of radiation attenuation using water curtains in a reduced-scale deck a ro-ro ship (original) (raw)
Related papers
2021
Experiments have been conducted at LEMTA to evaluate the containment of thermal radiation using water curtains in a model setup of a ro-ro ship's cargo deck with a scale of 1 to 12.5, providing data for future numerical simulations. The water curtains are created with one or two rows of water mist nozzles at pressures ranging from 3 to 8 bar, while the radiation source is an electric black body at 550ºC. The containment effect in terms of radiative attenuation is evaluated by comparing the radiation levels with and without water curtains measured using a multispectral infrared camera.
Experimental study on radiation attenuation by a water film
Journal of Quantitative Spectroscopy and Radiative Transfer, 2014
Radiative transfer through a water film was investigated. Films with average thicknesses between 100 and 380 μm were studied. The film thickness was measured using an optical method based on the attenuation of a near infrared laser beam. The attenuation of infrared radiation on a wide spectral range was determined simultaneously by using a FTIR spectrometer. A high attenuation efficiency was observed even for such small film thicknesses, which demonstrated the shielding effect of water films. Extension of present observations to high temperature sources allows the evaluation of the film absorption, which was predicted in the range 60-95% for films between 100 μm and 1 mm and for incident radiation from blackbodies up to 1473 K.
Computational Thermal Sciences, 2022
An improved theoretical model for shielding of thermal radiation from large-scale fires using pure water or seawater mists is presented. It is a continuation of a recent study and takes into account both the reabsorption of radiation in the absorption bands of gases and the variations of the radiative flux along the flame. The combined heat transfer problem consists of the radiative transfer, droplet evaporation kinetics, and convective heat transfer along the curtain. Previously suggested spectral models for the optical properties of water droplets and salt particles are used in the calculations. Radiative heat losses to the nozzle head and the floor below the curtain, as well as a decrease in the downward velocity near the floor, are taken into account for the first time. It is shown that these heat losses are insignificant even for thick curtains. The use of smaller droplets in the second layer of the mist curtain has been confirmed to reduce the required total water supply flow rate. It is also shown that the protection provided by a seawater curtain is almost the same as that obtained with pure water. Seawater is even preferable for better protection against fire radiation in the lower part of the curtain, where pure water droplets evaporate completely, whereas hollow sea salt particles remain in the lower part of the seawater mist curtain. The study confirms that seawater can be used in coastal areas, offshore platforms, and maritime transportation ships.
2021
An improved theoretical model for the shielding of radiation from large-scale fires by the mists of pure water or sea water is presented. This is a continuation of a recent study by accounting for both the partial re-absorption of radiation in the absorption bands of gases and the variation of the incident radiative flux along the flame. As before, the solution to a combined problem of heat transfer consists of the spectral radiative transfer in a mist curtain, the kinetics of droplet evaporation, and convective heat transfer along the curtain. The previously suggested spectral models for optical properties of water droplets and salt particles formed by evaporation of sea water droplets are used in the calculations. Unlike in our previous study, the radiative heat losses to the nozzle head and the floor under the curtain and the decrease in the downward velocity near the floor are accounted for the first time using the 2-D radiative transfer calculations. It is shown that heat losses towards the floor and nozzle head are insignificant even for thick water curtains. Some recommendations on correct choice of parameters of two-layered mist curtains with relatively low total flow rate of supplied water are given. In particular, it is confirmed that the use of smaller droplets of water in the second layer of mist curtains reduces the required total flow rate of supplied water. It is also shown that the protection offered by seawater curtain is almost the same as that of pure water. Moreover, the use of sea water is potentially preferable for better protection from the fire radiation in the lower part of the curtain. The latter statement is correct in the case of high protective mist curtains, when the droplets of pure water evaporate completely before reaching the floor, whereas the hollow particles of sea salt are there in the lower part of the seawater mist curtain. The study confirms that seawater curtains can be used in coastal areas, offshore platforms or maritime transportation ships for shielding fire thermal radiation.
Calculate Thermal Infrared Intensity of the Hull’s Military Ship
Journal of Geographic Information System, 2014
Stealth technology emphasizes on the reduction in reflection and radiation energies, the surface of target's body in the range of visual, radar, thermal and near IR and so on. Providing solutions to reduce thermal IR intensity radiation is one of the appropriate actions in passive defense for identifying power and targeting enemy. Therefore, questions are brought up: How much is the thermal IR intensity radiation of surface of the hall's vessel? How much is the effect of each parameter? This thesis tries to provide the software to answer these questions. The provided software measures thermal IR intensity radiation of the surface of the hall's vessel by the material substance, the temperature of the surface of the hall's vessel, the situation and characteristic of the thermal detector, noticing the coefficient of environment atmospheric transmittal. This software by changing the effective parameters on thermal IR radiation calculates the thermal radiation on thermal detector in different situations.
Radiation characteristics of heat protective materials of the buran orbital spacecraft
Journal of Engineering Physics and Thermophysics, 2000
Some features of investigations of the temperature dependence of the integrated and spectral emissivi~ of erosion-resistant coatings on a low-thermal conductivi~ fibrous heat insulation are discussed. Results are provided for the standard "black" and "white" coatings. A study is made of the influence of repeated attacks of the high-temperature dissociated air on the integrated emissivity of the "hlack" coating. Data are obtained on the radiation characteristics of this coating after fidl-scale tests during the Buran orbital spacecraft flight.
Heat transfer through a water spray curtain under the effect of a strong radiative source
Fire Safety Journal, 2006
Heat transfer inside a participating medium, made of droplets flowing in gas, receiving a strong irradiation on one side has been studied. Conditions investigated are similar to applications of water spray curtains as fire protection systems. The radiative part has been treated using a Discrete Ordinates Method combined with a c-K model in order to accurately deal with the problem of acute anisotropic scattering and strong wavelength dependence of absorption in gas. Coupling with the energy balance has been introduced using an iterative numerical solution. Various and combined effects due to radiative transfer, conduction, convection, turbulent diffusion and vaporization have been taken into account. This has been achieved introducing realistic dynamic data available in the literature and simultaneously solving a supplementary balance for the moisture inside the spray. Both diffuse and collimated irradiation have been considered. Various configurations have been studied from single sprays to multiple nozzle devices. The temperature level has been found to remain close to the one of the surrounding medium despite the large radiation absorption, as a consequence of competing effects between vaporization, convection and radiative transfer. The role of each term in the balance has been investigated indicating the need for further developments aimed at the accurate simulation of combined mass, momentum and heat transfer in the spray.