Semitransparent Liquid Research Articles

The interaction of the complex transfer processes in the phase transformations regimes of a water droplets

In this article the phase transformations of the water droplets in humid air flow are numerically modelled. The air temperature varies from 20°C to 1000°C, and the volume fraction of water vapor reaches up to 0.4. The droplet surface temperature dynamics defined by a numerical scheme which is based on by the fastest descent method. The interaction of complex heat and mass transfer processes has been investigated in the consistently changing water droplets condensation, transit and equilibrium evaporation regimes. Determination of droplets instantaneous temperatures in the iteration cycles is controlled by calculated heat fluxes balance condition, flowing toward and from the droplet surface, which must correspond to 99.95%. The reliability of the numerical method was confirmed when comparing the calculated water droplets equilibrium evaporation temperature in humid air with the wet bulb thermometer temperature, and with the experiments data. In the case of combined heating a calculated water droplets equilibrium evaporation vapor flux correlates well with other author's experimental data and modeling results. The numerical researches are emphasized specially for cases of water vapor condensate spraying in biofuel combustion technologies. The water droplet heat transfer as well as phase transformations transit and equilibrium evaporation processes were modelled in cases of convective and combined convective-radiative heating. In semi-transparent liquid the impact of absorbed radiation flux for water droplet complex transfer processes interaction was evaluated.

Transmission and total internal reflection integrated digital holographic microscopy.

We develop a transmission and total internal reflection (TIR) integrated digital holographic microscopy (DHM) by introducing a home-made Dove prism with a polished short side. With the help of angular and polarization multiplexing techniques, the 2D refractive index distribution of a specimen adhered on the prism surface is determined using TIR-DHM. Meanwhile, the thickness profile is unambiguously calculated from the phase information using transmission DHM. This integrated microscopy is nondestructive and dynamic and can be used to simultaneously measure the index distribution and thickness profile of transparent or semi-transparent liquid or solid samples.

Infrared thermography measurement of two-phase boiling flow heat transfer in a microchannel

In this study, a non-intrusive method to directly measure the fluid temperature and two-phase flow patterns in micro-scale system was developed. To achieve this goal, an adequate calibration process of infrared (IR) thermography measurement and an experimental design of IR transparent convective flow in a microchannel were established. The temperature distribution of the fluid along the microchannel was measured by IR thermography through a germanium window of thickness 5 mm. The transparent germanium window was used to facilitate the transmission of long-wavelength IR rays. The infrared images were obtained at a frame rate of 200 fps, which enabled observation of the transient temperature behavior during flow boiling in the microchannel. A semi-transparent liquid, namely ethanol, was used as the working fluid, with a mass flux of 20.3 kg/m2s and heat flux range of 3.1–244.1 kW/m2. The experimental results confirmed that IR thermography could be used to capture the transient single- and two-phase flow patterns as well as the fluid temperature along the channel. To the best of our knowledge, this paper is the first presentation of IR visualization of two-phase flow patterns in a microchannel. The trends of the local heat transfer coefficients with respect to the two-phase flow patterns are discussed, and the experimentally determined coefficients are compared with those calculated by commonly used equations.

Fixed Grid Simulation of Radiation-Conduction Dominated Solidification Process

In this paper conduction-radiation controlled solidification process of semitransparent materials was numerically analyzed. New approach in this kind of simulations, which is based on the fixed grid front tracking method combined with the immersed boundary technique, was adopted and examined. The presented method enables accurate dealing with solidification processes of semitransparent materials which have different optical and thermophysical properties of solid and liquid phases as well as with absorption, emission, and reflection of the thermal radiation at the solid-liquid interface without applying moving mesh methods. The proposed numerical approach was examined by solving several simplified thermal radiation problems with complex fixed and moving boundaries both in two-dimensional and axisymmetric spaces. For some of them the accuracy of obtained results was proved by comparing with reference works, other showed capabilities of the proposed method. For simplified solidification processes of semitransparent materials three configurations of optical properties, i.e., semitransparent solid phase and opaque liquid phase, opaque solid phase and semitransparent liquid phase, and semitransparent both phases were considered. The interface between solid and liquid phases was treated to be opaque, absorbing, emitting, and reflecting diffusely the thermal radiation. Results of the numerical simulations show that the presented numerical approach works well in this kind of problems and is promising for simulation of real solidification processes of semitransparent materials.

The peculiarities of hot liquid droplets heating and evaporation

The change of the thermal state of a sprayed liquid droplet is calculated using the method of combined analytical and numerical research, which requires the balance of energy flows, incoming to the droplet and outgoing from it. The method evaluates unsteadiness of heat and mass transfer processes and interaction, which occurs under the influence of the Stefan’s hydrodynamic flow, radiant flow absorbed in semitransparent liquid and the Knudsen layer, which surrounds the droplets. The expedience of the thermal state’s evaluation of dispersed liquid is verified using the parameter, expressed by the ratio of liquid’s initial temperature on equilibrium evaporation temperature of droplets. As the above-mentioned parameter is less than 1, liquid is offered to be called “cold”; “warm”, as the parameter equals 1 and “hot”, as it exceeds 1. In each case the peculiarities of the thermal state change of sprayed liquid droplets are individual during an unsteady phase transformation mode. The characteristic curves, representing the change of transfer parameters, are determined for conductively heated droplets and when the Knudsen layer’s influence is neglected. These curves join together variation of the parameters of the thermal state change and phase transformation for droplets of infinitesimal set of diameters, but with the same initial liquid temperature, as the droplets evaporate in gas with constant parameters. Deviations from the characteristic curves allow evaluating the influence of more complicated boundary conditions on the interaction of transfer processes.

The Propagation of Infrared Radiation in a Semitransparent Liquid Containing Gas Bubbles

A theoretical model is suggested of the propagation of infrared radiation in a semitransparent liquid containing gas bubbles, which includes an approximate description of the radiation characteristics and radiation transfer in a disperse system. Calculations are performed for a layer of water containing vapor bubbles illuminated by the thermal radiation of an external source. It is demonstrated that, for real values of the parameters, the scattering of radiation by bubbles may lead to the absorption of thermal radiation in a much thinner layer of water. The possible application of the obtained results to the solution of a conjugate problem is discussed.

Interaction of the transfer processes in semitransparent liquid droplets

The study presents the mathematical model of unsteady heat transfer in evaporating semitransparent droplets of non-isothermal initial state and the numerical research method, evaluating selective radiation absorption and its influence on the interaction of transfer processes. The relation of the transfer processes inside droplets and in their surroundings and the necessity of thorough research of these processes are substantiated. When modeling the combined energy transfer in water droplets, the evaluation of thermoconvective stability in evaporating semitransparent liquid droplets is presented; the influence of the droplet initial state on its heating and evaporation process is investigated. The influence of heat transfer peculiarities on the change of the evaporating droplet state is indicated. Main parameters, which decide the peculiarities of the interaction of unsteady transfer processes in droplets and their surroundings, are discussed. The results of the numerical research are compared to the known results of the experimental studies of water droplet temperature and evaporation rate.

Regularities of unsteady radiative–conductive heat transfer in evaporating semitransparent liquid droplets

The numerical investigation method of unsteady transfer processes in evaporating droplets in radiating media is introduced, evaluating the dependence of optical spectral properties of material upon temperature. The distribution of temperature and heat fluxes regularities in heating and simultaneously evaporating water droplets has been investigated. It is shown that as a cause of interaction of radiation and conduction processes, the profile of the temperature field inside the droplet is distorted, and the magnitude and direction of heat conductivity flux vector changes. According to the maximum place in the instant temperature field of the droplet, it is suggested to distinguish three periods of state change for an evaporating droplet: initial, transient and final. The results of the unsteady radiative–conductive heat transfer are generalized by using similarity theory methods.

Measurement of emittance of metal interface in molten salt

A new technique for measuring the total normal emittance of a metal in a semi-transparent liquid has been proposed and this technique has been applied to measure the emittance of stainless steel (SUS304), nickel, and gold in molten potassium nitrate KNO3. These emittance data are indispensable to analyzing the radiative heat transfer between a metal and a semitransparent liquid, such as a molten salt.

New gelling properties of Alaska pollack frozen mince induced by urea.

A mixture of finely chopped Alaska pollack frozen mince (100g) and 8M urea (300ml) was heated until it dissolved. The solution was dialyzed against 10l of water, first at 4°C overnight and next at 60°C for several hours. The dialyzate (urea-treated mince, water content 95-97%) was a grayish, semi-transparent liquid at room temperature, but set to a brittle gel on cooling. The molten, urea-treated mince was poured into a glass tube and frozen into a suitable shape at -20°C. By immersing the shaped frozen mince in CaCl2, CaSO4, MgCl2 or MgSO4 (0.1-1.0M), or in CH3COOH-NaOH or HCl-NH4OH (pH 4-5), an elastic, whitish gel (water content 80-97%) was obtained. If the molten, urea-treated mince was injected into these solutions with a syringe, a noodle-like, long and slender gel was formed. If the mince was poured into a hot salt solution and the resulting suspension was wrung with a thick cloth, the residue coagulated on cooling in the wrung from. The gels formed by the reaction with salt or buffer did not melt on heating. The elasticity of the flesh gel, Kamaboko, from Alaska pollack frozen mince was not improved by the addition of the urea-treated mince.

Unsteady Heat Transfer in an Optically Thick Semitransparent Liquid Layer Heated by a Radiant Heat Source

Unsteady Heat Transfer in an Optically Thick Semitransparent Liquid Layer Heated by a Radiant Heat Source

Simultaneous Heat and Mass Transfer on the Surface of Optically Thick Semitransparent Liquid Heated by a Radiant Heat Source

Simultaneous Heat and Mass Transfer on the Surface of Optically Thick Semitransparent Liquid Heated by a Radiant Heat Source

On the Blood of the Invertebrata

The blood of the Invertebrata, like that of the Vertebrata, is not homogeneous. It consists of a transparent or semitransparent liquid, and a number of small, solid corpuscles which float in it.In the higher animals the corpuscles are of two kinds—red and colourless; but in the Invertebrata there are, as a rule, only colourless corpuscles. The red blood of Annelids is different from the red blood of Vertebrates, inasmuch as the plasma is coloured, and the corpuscles are colourless in the former, while in the latter the plasma is colourless, and there are present coloured and colourless corpuscles.