Influence Of Liquid Temperature Research Articles

Течение гелия-II в канале с пористой вставкой при безвихревом сверхтекучем движении

The heat and mass transfer processes associated with flow of superfluid helium (He-II) in a channel filled with porous medium in a certain part of its length are analyzed. The heat flux is directed along the channel axis so that a vapor plug is generated near the heater. The steady-state heat-and-mass transfer processes at the interfaces are calculated using the molecular kinetic theory methods. The motion of He-II in pores is described by equations that take into account the specific features of heat and mass transfer in a quantum fluid. A map of flow modes for normal and superfluid components for a monodisperse porous fill is plotted. The normal component’s laminar and turbulent flow modes for nonvortex superfluid motion are considered. Formulas correlating the porous insert length with the fluid velocity are derived for these modes. It is found that He-II flow toward the heater is possible when the porous insert length exceeds a certain value. The dependences of this reversible length on the porous fill structural features and heat flux density are presented. For the laminar mode of normal motion, the reversible length is determined by the diameter of monodisperse fill particles at a given temperature, whereas in the turbulent mode this length also depends on the heat flux. The influence of liquid temperature is studied. Reversible length calculation examples are given. The results of the performed calculations are analyzed by comparing them with the previously obtained data for He-II flow in a single capillary.

Spray of gelled propellants from an impinging-jet injector under different temperatures

This paper presents the results of an experimental study on the spray characteristics of gelled propellant from an impinging jet injector under different liquid temperatures. A high-speed camera was used to record detailed information about the liquid sheet breakup process and spray development. The rheological characteristics of the gel simulant under different temperatures were tested. It was found that the consistency coefficient decreases and the flow index increases as the liquid temperature increases. The flow characteristics and spray patterns for injectors with tapered orifices and straight orifices were tested, respectively. Because the injection of fluid through tapered orifices can decrease the viscosity of the fluid, the mass flow rate is increased and the liquid sheet behaves more unstably for injector with tapered orifices. The influence of liquid temperature on the mass flow rate for both injectors is minor. The spray photos showed that the liquid sheet is more unstable and easier to break up at higher temperature for both injectors. Generally, the liquid sheet breakup length decreases and the disturbance wavelength increases as the liquid temperature increases.

Temperature effect on the impact of a liquid-jet against a rigid boundary

An experimental study concerning the influence of liquid temperature on the collapse of cavitation bubble near a rigid boundary is presented. The impact loading induced by high-speed liquid-jet during the final stage of the bubble collapse in distilled water at different temperatures is investigated by focusing a Q-switched laser pulse. In addition, based on the modified Rayleigh theory, some characteristic parameters, such as the maximum bubble radius, and liquid-jet impact pressure, are also obtained as a function of temperature. The results show that liquid-jet impact pressure increases with liquid temperature and reaches a peak, followed by a decrease. The increase is due to the change in physical properties of distilled water, and the decrease is due to the thermodynamic effect of a bubble collapse and the change of material mechanical properties in high temperature. The peak appears at the approximate average of freezing and boiling temperatures. The mechanism of liquid temperature influence on cavitation erosion also has been discussed.

Removal of Nitrogen Dioxide and Sulfur Dioxide from Air Streams by Absorption in Urea Solution

The study focuses on the absorption rates of NO2, SO2 and a mixture of these two acid gases into urea solution in packed bed column. The absorption rate was studied as a function of absorbent temperature, urea concentration and acid gas concentration. The influence of liquid temperature between 10 - 40?C, urea concentration between 0.1 - 0.5 M and acid gas concentration NO2 between 100 - 1000 ppm (191 - 1910 mg/m3), SO2 between 500 - 2500 ppm (1310 - 6530 mg/m3) were investigated. The mass gas flow rate of 20.646 (kg/m2.min) at 25?C and the absorption rate were determined by measuring the NO2 and SO2 concentrations in the inlet and outlet streams of the absorptioncolumn. The absorption rate of SO2 increases with the decrease of temperature of absorbent (urea solution) and with the increase of the urea concentration. The presence of NO2 in the effluent gas stream lowers the absorption rate of SO2 in urea solution due to the fast reaction of NO2 with urea as compared with SO2. The absorption rate of NO2 decreases as the urea concentration exceeds 0.4 mol/l and for NO2 gas concentration of 100 ppm due to the decrease the diffusivity of the gas. The experimental data were analyzed using dimensionless analysis to find the correlation of mass transfer coefficient in the packed column Sh (H / dp)1.2 = 4.19*10–2 *(G' dp / μg)0.87 (μg / ρg DAB)0.60 The results confirmed the hypothesis that the absorption is accompanied with chemical reaction. Also it is found the increasing the temperature of absorbent solution the absorption rate of two gases is decreases. The mass transfer coefficient models are in good agreements with the Kramer’s equation.

Analysis of zonal shrinkage in alloy steels

Thermal behaviour of the solidifying steel structure is important for understanding of the defects during ingot solidification. During solidification and cooling, most metals shrink. As a consequence in upper part of solid ingot, pores and pipes of typical shapes and size are formed. Forming of pipes is closely related to the casting and solidification processing parameters. In the present paper the influence of liquid temperature, chemical composition and temperature gradient on the shrinkage intensity are investigated. The ratio of the pipe depth to total ingot height as a criterion of the pipe size is used. The values of the temperature gradients on the base of the numerical model solidification are obtained. The experimental measurements of temperature change have been carried out on laboratory steel ingot. The results by numerical model are compared with the experimental ones and showed a good agreement.

On the effect of liquid temperature upon bubble coalescence

An experimental study concerning the influence of liquid temperature on bubble coalescence is presented. Bubble collisions in two different liquids (water and ethanol) were analysed at four distinct temperatures ( 10 ⩽ T ⩽ 40 ∘ C ) , using air as the dispersed phase in all cases. A quantitative criterion was developed to compute the critical velocity for bubble coalescence based on the relative velocities and the outcome (coalescence or bouncing) of the recorded collisions. The critical velocity, and consequently bubble coalescence, was shown to increase as the liquid temperature was raised, an effect whose intensity depended on the kind of liquid employed. Using some simplifying assumptions, a comparison between the experimentally observed trends and the predictions of literature models for the film drainage was drawn. The experimental data were used together with available literature data in the development of a dimensionless correlation for predicting the critical velocity as a function of the liquid properties.

Influence of liquid temperature and flow rate on enamel erosion and surface softening.

Enamel erosion and softening are based on chemical processes which could be influenced by many factors including temperature and acid flow rate. Knowledge of the influence of these variables could have relevance to research experiments and clinical outcomes. Both parameters were investigated using an ultrasonication and profilometry method to assess erosion depth and surface softening of enamel. The influence of temperature was studied by eroding polished human enamel samples at 4, 20, 35 or 50 degrees C for 2 h. Secondly, different liquid flow conditions were established by varying acid agitation. Additionally, a slow laminar flow and a jet of citric acid, to simulate drinking through a straw, were applied to specimens. Erosion depth increased significantly with acid temperature from 11.0 microm at 4 degrees C to 35.8 microm at 50 degrees C. Surface softening increased much more slowly and plateaued at 2.9 microm to 3.5 microm after 35 degrees C. A strong dependence of erosion on liquid flow was revealed. In unstirred conditions only 8.6 microm erosion occurred, which increased to 22.2 microm with slow stirring and 40.9 microm with fast stirring. Surface softening did not increase correspondingly with its largest extent at slow stirring at 3.4 microm.The implication of these data are: first, the conditions for erosion experiments in vitro or in situ need to be specified for reliable comparisons between studies. Secondly, erosion of teeth by soft drinks are likely to be influenced both by the temperature of the drink and individual drinking habits.

Multibubble sonoluminescence intensity dependence on liquid temperature at different ultrasound intensities

It is shown that the influence of liquid temperature on the sonoluminescence (SL) intensity is different depending on the ultrasound intensity. At the ultrasound intensities not much higher than the cavitation appearance threshold the SL intensity increases with the temperature. At the ultrasound intensities considerably exceeding the cavitation threshold the SL intensity decreases with an increase of the temperature. At intermediate ultrasound intensities the SL intensity temperature dependence is extreme: the cavitation activity at first increases with temperature, reaches a maximum and then decreases. Continuous and pulsed modes of irradiation at frequencies 880 and 21.9 kHz were used in experiments.

Influence of liquid temperature and electrode size on insulated breakdown characteristics in saturated superfluid helium

Influence of liquid temperature and electrode size on insulated breakdown characteristics in saturated superfluid helium

The influence of liquid temperature on the sonoluminescence hot spot

An explanation is provided for the influence of relatively small changes in liquid temperature on the hot spot within a sonoluminescence bubble. This influence derives from a change in the (stable) equilibrium mass of the bubble due to a variation of the gas solubility in the liquid with temperature. If the acoustic drive amplitude is held constant, a change in the liquid temperature has a large or small effect depending on the variability of the solubility with temperature. For a gas like xenon, which has rapidly decreasing solubility in water with increasing temperature, a decrease in water temperature shifts the stable mass exchange equilibrium to a smaller bubble size. This increases the ratio of maximum to minimum bubble radius over an acoustic cycle, resulting in a much higher hot spot temperature. In contrast helium has very little variation of solubility with temperature near room temperature; therefore the hot spot temperature is relatively insensitive to variations in the liquid temperature outside a helium bubble.