Reactive Recoil and Pressure Pulsations with 1/ f Power Spectrum under Conditions of Explosion Boiling of Jets of Superheated Liquid

The results are given of an experimental investigation of the reactive recoil of jets of boiling up liquids in a thermodynamically highly nonequilibrium mode of efflux. The experimental data are given in the dimensionless form using the thermodynamic similarity methods. The correlation is discussed between the abrupt decrease in the reactive power with a complete disintegration of the jet under conditions of explosion boiling. Local measurements are performed of pressure pulsations in a jet of superheated liquid with different mechanisms of vaporization. It is found that, under conditions of explosion boiling, the power spectrum of pulsations depends inversely proportionally on frequency (1/f or flicker noise). This form of power spectrum implies the possibility of strong low-frequency pulsations of reactive recoil of boiling up flows.     

Features of the breakup of jets of a low-viscosity liquid in a subsonic entraining flow of gas

The results of electrocontact measurements are used as a basis for examining the mechanisms (variants) of the breakup of a liquid jet and a dense atomizing jet. The deformational scheme of breakup in an entraining subsonic gas flow is generalized.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 1, pp. 24–32, January, 1991.     

Heat-transfer coefficients within the cavity formed by the tip of cryosurgical probes

The heat-transfer coefficients between a jet of liquid nitrogen and the inside surface of the tip of three different cryoprobes were measured by a transient method. Forced-convection nucleate boiling and unstable film boiling of liquid nitrogen in the cavity of the tip were investigated. The heat-transfer data was correlated in terms of dimensionless groups: Nusselt, Prandtl and Reynolds numbers, temperature difference and geometrical parameters.     

Performance analysis of no-vent fill process for liquid hydrogen tank in terrestrial and on-orbit environments

Two finite difference computer models, aiming at the process predictions of no-vent fill in normal gravity and microgravity environments respectively, are developed to investigate the filling performance in a liquid hydrogen (LH₂) tank. In the normal gravity case model, the tank/fluid system is divided into five control volume including ullage, bulk liquid, gas–liquid interface, ullage-adjacent wall, and liquid-adjacent wall. In the microgravity case model, vapor–liquid thermal equilibrium state is maintained throughout the process, and only two nodes representing fluid and wall regions are applied. To capture the liquid–wall heat transfer accurately, a series of heat transfer mechanisms are considered and modeled successively, including film boiling, transition boiling, nucleate boiling and liquid natural convection. The two models are validated by comparing their prediction with experimental data, which shows good agreement. Then the two models are used to investigate the performance of no-vent fill in different conditions and several conclusions are obtained. It shows that in the normal gravity environment the no-vent fill experiences a continuous pressure rise during the whole process and the maximum pressure occurs at the end of the operation, while the maximum pressure of the microgravity case occurs at the beginning stage of the process. Moreover, it seems that increasing inlet mass flux has an apparent influence on the pressure evolution of no-vent fill process in normal gravity but a little influence in microgravity. The larger initial wall temperature brings about more significant liquid evaporation during the filling operation, and then causes higher pressure evolution, no matter the filling process occurs under normal gravity or microgravity conditions. Reducing inlet liquid temperature can improve the filling performance in normal gravity, but cannot significantly reduce the maximum pressure in microgravity. The presented work benefits the understanding of the no-vent fill performance and may guide the design of on-orbit no-vent fill system.     

Nucleation and Boiling Near the Gas–Liquid Critical Point

Nucleation near the gas–liquid critical point depends sensitively on whether the pressure or the volume is fixed. We consider near-critical fluids close to the coexistence curve. (i) Upon decompression to a constant pressure with a fixed boundary temperature, bulk nucleation can well be induced from a gas state, whereas from a liquid state boiling is easily triggered in the thermal diffusion layer near the boundary. In this case, bulk nucleation in a metastable gas is described by the classical Lifshitz–Slyozov theory. (ii) Upon cooling of the boundary temperature under the fixed-volume condition, bulk nucleation can be realized in a liquid and a modified Lifshitz–Slyozov theory follows. However, if a gas is cooled from the boundary at a fixed volume, liquid droplets readily appear in the thermal diffusion layer, apparently suggesting no metastability in a gas in agreement with previous experiments. (iii) On the other hand, if a liquid is heated at the boundary wall, boiling readily occurs both at a fixed volume and at a fixed pressure.     

Boiling of liquid in the cell of a jet printer

An approximate calculation of the main parameters of boiling of a liquid in the cell of a jet printer — the ejection velocity of a liquid drop and the limiting permissible (critical) heat flow density supplied to the thermoresistor — is carried out. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 2. pp. 218–221, March–April, 1998.     

Stability of boiling shock

This paper studies the stability of boiling shock formed when limiting (near spinodal) superheatliquid superheat is reached in a flow. In these conditions the boiling shock is always accompanied by oscillations specific to problems of this class. Physical analysis of the mechanism of the generation of such oscillations is performed and estimates of pulsations for the reactive force of the outflowing medium are found which are in good agreement with the experiment. A conclusion is made that the mechanism of jet disintegration observed in these conditions may serve as an efficient method for liquid fuel jets atomizing in a number of technical applications.     

Study into the Pattern of Flashing of Liquid in the Vicinity of the Limit of Its Attainable Superheating

The pattern of flashing of liquid in the vicinity of the limit of its attainable superheating is investigated experimentally. The Skripov criterion is used, according to which, in the case of homogeneous boiling, the product of the mean expectation time for boiling by the magnitude of volume being superheated at preassigned temperature and pressure is a constant quantity. The experiments are performed with n-pentane. Thanks to thorough degassing of the liquid being investigated, the temperature of the previously attained superheating is exceeded by 1.0–1.5°C. The mean lifetime is measured in several glass capillaries of substantially different volumes. The data obtained point to the invalidity of the criterion of homogeneity of boiling of liquid in the vicinity of the limit of its attainable superheating. Also studied is the probability density of the expectation times for boiling with respect to magnitude. It is demonstrated experimentally that the probability density curve has a small empty portion at the beginning, an abrupt rise to a maximum, and a close-to-exponential decrease. This form of the probability density function is typical of unsteady-state random processes.     

Initial fuel temperature effects on burning rate of pool fire

The influence of the initial fuel temperature on the burning behavior of n-heptane pool fire was experimentally studied at the State Key Laboratory of Fire Science (SKLFS) large test hall. Circular pool fires with diameters of 100mm, 141 mm, and 200 mm were considered with initial fuel temperatures ranging from 290 K to 363 K. Burning rate and temperature distributions in fuel and vessel wall were recorded during the combustion. The burning rate exhibited five typical stages: initial development, steady burning, transition, bulk boiling burning, and decay. The burning rate during the steady burning stage was observed to be relatively independent of the initial fuel temperature. In contrast, the burning rate of the bulk boiling burning stage increases with increased initial fuel temperature. It was also observed that increased initial fuel temperature decreases the duration of steady burning stage. When the initial temperature approaches the boiling point, the steady burning stage nearly disappears and the burning rate moves directly from the initial development stage to the transition stage. The fuel surface temperature increases to its boiling point at the steady burning stage, shortly after ignition, and the bulk liquid reaches boiling temperature at the bulk boiling burning stage. No distinguished cold zone is formed in the fuel bed. However, boiling zone is observed and the thickness increases to its maximum value when the bulk boiling phenomena occurs.     

Boiling of the Chemical Elements

The molar boiling entropy, ΔS_boil, has been assumed in the literature to be approximately the same for one‐component systems, which is known as the rule of Pictet‐Trouton. Using experimental data on ΔS_boil of the chemical elements, however, this rule must be questioned. Instead, the increase of the molar entropy upon boiling is estimated from the expansion of the melt to the volume of the vapour under atmospheric pressure. This yields the right order of magnitude for ΔS_boil. The molar boiling entropy depends on the number of electrons in the outermost electron shell of the free atoms of the chemical elements. Thus, the electronic system stores some entropy needed for boiling and seems to cause the phase transition liquid/vapour. This is supported by the correlation between the electron configuration and the molar specific heat capacities in the liquid and the vapour state near the boiling temperature. Accordingly, boiling is induced by electronic transitions into anti‐bonding states at a rate sufficient to increase the partial pressure of the vapour within a melt. This is in contrast to the traditional explanation of boiling by breaking pair bonds between the atomic constituents of a melt which neglects the effect of transitions of the bonding electrons.     

Nonequilibrium phase transitions in a jet of highly superheated water

Results are given of an experimental study into the dependence of integral and local characteristics of hot water flow on the value of superheating and on the kinetics of boiling in this water. Abrupt variations are revealed of parameters of a jet of boiling water such as the reactive force, the jet cone angle, and the rate of nucleation of vapor bubbles in the jet. Abrupt variations of modes of jet flow are treated as nonequilibrium phase transitions. This enables one to invoke model concepts of generation of 1/f fluctuations under conditions of nonequilibrium phase transitions in open systems. The inversely proportional dependence of power spectra of oscillation on frequency (1/f fluctuations) in a jet of highly superheated water is found experimentally both under laboratory conditions and in a commercial-scale steam generator. Characteristic scales are discussed for reducing the experimental results for reactive force to dimensionless form.     

Self-excitation of oscillatory processes when a liquid is injected into a plasma jet

The process of cooling of a wall by a liquid injected into a plasma jet through a circular opening is studied experimentally. Different flow regimes in a vaporliquid system, including self-excited oscillatory regimes associated with the transfer of the region of boiling from the exterior side of the wall into the interior cavity of the casing, were obtained. Self-excited oscillations of the wall temperature are described with the help of approximation formulas.Translated from Inzherno-fizicheskii zhurnal, Vol. 61, No. 4, pp. 650–655, October, 1991.     

The shape of jets during discharge of a superheated liquid (structure of wave formations and the reactive force)

Based on the boiling shock concept, a physical model of discharge from orifices and short nozzles of the flashing liquid with temperatures reaching the critical thermodynamic temperature has been constructed. The mechanism of formation of “daisy-shaped” jets that accompany the discharge modes with the radial jet expansion has been investigated. It has been shown that in the case under consideration the flow separates into two areas not connected with each other, viz., the central core in the vicinity of the flow axis and the peripheral liquid expansion region. The geometry of shock wave formations that occur during discharge of a high-temperature liquid has been studied. Comparison with experimental data shows a good agreement. The effect of a stepwise drop in the reactive force to zero upon onset of discharge modes with a jet radial expantion has been explained.     

Confined jet impingement of liquid nitrogen onto different heat transfer surfaces

Jet impingement of liquid nitrogen owns many applications in the cryogenic cooling aspects, such as, cooling of high-power chips in the electronic devices and cryoprobes in the cryosurgery. In the present study, we systematically investigated the confined jet impingement of liquid nitrogen from a tube of about 2.0 mm in diameter onto the heat transfer surfaces of about 5.0 mm in basement diameter with different heat transfer surface geometries and conditions, i.e., flat surface, hemispherical surface and flat surface with a needle. The effects of many influential factors, such as, the geometry of the heat transfer surface, jet velocity, distance between the nozzle exit and heat transfer surface, heat transfer surface condition, and some other, on the heat transfer were investigated. The heat transfer correlations were also proposed by using the experimental data, and it was found that the heat transfer mechanism of liquid impingement in the confined space was dominated by the convective evaporation rather than the nucleate boiling in the present case. The critical heat flux (CHF) of the confined jet impingement was measured and the visualization of the corresponding flow patterns of the confined jet impingement of liquid nitrogen was also conducted simultaneously to understand the heat transfer phenomena.     

A survey of modeling techniques for consequence analysis of accidental chemical releases to the atmosphere

This paper surveys techniques for estimating the consequences of accidental chemical releases to the atmosphere. The first section is devoted to a discussion of the characterization of gas, liquid and two-phase releases. In addition to the mass release rate, parameters such as phase composition, density and velocity are shown to be of critical importance in the subsequent dispersion of the release. Emissions due to boiling and evaporation from liquid spill pools are also treated. The second part of the paper describes the techniques for calculating the spatial and temporal variation of chemical concentrations due to jet and heavy gas dispersion. Methods are also presented for estimating the damage resulting from the ignition of a flammable plume or liquid spill pool. Finally, the paper deals with model prediction uncertainty and its impact upon the process of emergency response planning.     

Saturated Liquid Densities for 33 Binary Refrigerant Mixtures Based on the ISM Equation of State

In this work, the ISM equation of state based on statistical-mechanical perturbation theory has been extended to liquid refrigerant mixtures by using correlations of Boushehri and Mason. Three temperature-dependent parameters are needed to use the equation of state: the second virial coefficient, B₂(T), an effective van der Waals covolume, b(T), and a scaling factor, α (T). The second virial coefficients are calculated from a correlation based on the heat of vaporization, ΔH_vap, and the liquid density at the normal boiling point, ρ_nb. α(T) and b(T) can also be calculated from second virial coefficients by a scaling rule. The theory has considerable predictive power, since it permits the construction of the PVT surface from the heat of vaporization and the liquid density at the normal boiling point. The equation of state was tested on 33 liquid mixtures from 12 refrigerants. The results indicate that the liquid densities can be predicted to at most 2.8% over a wide range of temperatures, 170–369 K.     

An analysis of the equilibrium configurations of charged cylindrical jets of a conducting liquid

A region of physical parameters is found where the equilibrium configurations of charged cylindrical jets of a conducting liquid can exist; these configurations correspond to the azimuthal mode n=2 of the surface deformations of a round jet. A critical value of the jet linear charge is determined for which the jet splits into two. It is shown that such instability is excited in a soft regime.     

Formation and properties of copper film on Tl-(Pb,Bi)-Sr-Ca-Cu-O superconductor by electrodeposition from aqueous solution

A new process of electrodeposition in saturated cupric sulphate aqueous solution was successfully developed for the formation of copper film on a high-T_c, three Cu-O layered Tl-(Bi, Pb)-Sr-Ca-Cu-O superconductor substrate surface for the first time. Scanning electron microscopy and electron micro-probe analysis were used to investigate the morphology of the substrate surface and the composition of the copper superconductor interface. After the electrodeposition process, no evident changes in the temperature dependence of electrical resistivity were found by four-point probe measurement. The difference of magnetic properties before and after electrodeposition was investigated from magnetization measurements. Almost no degradation of the bulk properties was observed from the susceptibility data. The copper-superconductor contact was confirmed to show Ohmic behaviour by two-pointI–V characterization at liquid nitrogen boiling temperature.     

Equation of State for Nonpolar Fluids: Prediction from Boiling Point Constants

A new corresponding states correlation for the second virial coefficient of nonpolar fluids in terms of the boiling point constants is presented. The scaling constants are the normal boiling point temperature, T _bp, which is used to form a dimensionless temperature and the liquid density at the normal boiling point, _bp, which is used to form a dimensionless second virial coefficient. The procedure has been examined for a large number of substances including noble gases, diatomic molecules, saturated hydrocarbons up to C₈, and a number of aliphatic, aromatic, and cyclic hydrocarbons. The resulting correlation has been applied to predict the equation of state of fluids over the range from the vapor-pressure curve to the freezing curve at various temperatures from the triple point up to the nonanalytical critical region. The equation of state has been applied to reproduce the liquid density of a great number of compounds both in the saturation and compressed states, at temperatures up to 2000 K and pressures up to 10000 bar, within an accuracy of a few percent. In particular we have shown that knowledge of two readily measurable constants is sufficient to determine the pvT surface of pure normal fluids having a variety of structural complexities.