Abstract:
This paper is devoted to the thermally activated dynamics of the capillary condensation. We present a simple model which enables us to identify the critical nucleus involved in the transition mechanism. This simple model is then applied to calculate the nucleation barrier from which we can obtain informations on the nucleation time. These results are compared to the numerical simulation of a Landau-Ginzburg model for the liquid-vapor interface combined with a Langevin dynamics.

Abstract:
Helium excimers generated by a corona discharge were investigated in the gas and normal liquid phases of helium as a function of temperature and pressure between 3.8 and 5.0 K and 0.2 and 5.6 bar. Intense fluorescence in the visible region showed the rotationally resolved $d^3\Sigma_u^+ \rightarrow b^3\Pi_g$ transition of He$_2^*$. With increasing pressure, the rotational lines merged into single features. The observed pressure dependence of linewidths, shapes and lineshifts established phases of coexistence and separation of excimer-helium mixtures, providing detailed insight into nucleation, solvation and boiling of He$_2^*$-He$_n$ clusters.

Abstract:
Molecular dynamics (MD) simulation is carried out for the bubble nucleation of liquid nitrogen in explosive boiling. The heat is transferred into the simulation system by rescaling the velocity of the molecules. The results indicate that the initial equilibrium temperature of liquid and molecular cluster size affect the energy conversion in the process of bubble nucleation. The potential energy of the system violently varies at the beginning of the bubble nucleation, and then varies around a fixed value. At the end of bubble nucleation, the potential energy of the system slowly increases. In the bubble nucleation of explosive boiling, the lower the initial equilibrium temperature, the larger the size of the molecular cluster, and the more the heat transferred into the system of the simulation cell, causing the increase potential energy in a larger range.

Abstract:
An analytn model for working fluids flowing through capillary tubes has been established with the approximate integral method. All the possible flow regimes in the capillary tubes, including subcooled, two-phase and superheated regimes, are covered in the model, and different analytic solutions are given respectively for each flow regime. As examples, the mass flow rates of refrigerants R12, R134a and R600a through capillary tubes are predicted by the model, and compared with those evaluated by a general distributed-parameter model. The mean bias falls into 1% and the maximum bias is 2.2%, while the computation speed of the new model is more than one order of magnitude higher than that of the distributed-parameter one.

Abstract:
The excitation of plasma waves over a length of up to 8 centimeters is, for the first time, demon- strated using laser guiding of intense laser pulses through hydrogen filled glass capillary tubes. The plasma waves are diagnosed by spectral analysis of the transmitted laser radiation. The dependence of the spectral redshift, measured as a function of filling pressure, capillary tube length and incident laser energy, is in excellent agreement with simulation results. The longitudinal accelerating field inferred from the simulations is in the range 1 -10 GV/m.

Abstract:
The experiments of the onset of nucleate boiling using R134a as working fluid were conducted in vertical helically-coiled tubes. The experiments were carried out with a range of pressure from 450 to 850 kPa, inlet subcooling from 4.7 to 15.0 ℃, heat flux from 0.11 to 8.9 kW/m2 and mass flux from 218.2 to 443.7 kg/(m2·s). The heat flux, superheat and temperature undershoot at the ONB are analyzed in vertical helically-coiled tubes. Also, the effects of mass flux, system pressure, inlet subcooling and geometric parameters on the ONB are studied. The results demonstrate that the inception heat flux and superheat increase with increasing mass flux and inlet subcooling, but decrease with increasing system pressure and helix diameter. The pitch of the helical coil has a slight effect on the wall superheat and heat flux at the ONB. The correlation of heat flux at the ONB of subcooled flow boiling in helical coil is developed based on the experimental data, and it shows a good agreement with the experimental data.

Abstract:
Liquid in grooved capillaries, made by e.g. inserting a plate in a cylindrical tube, exhibits unusual spreading and flow properties. One example is capillary rise, where a long, upward tongue on top of the usual meniscus has been observed along the groove. We attribute the underlying mechanism to a thermodynamic instability against spreading for a (partial or complete wetting) liquid in a sharp groove whose opening angle $\alpha$ is less than a critical value $\alpha_c=\pi-2\theta$. The equilibrium shape of the tongue is determined analytically. The dynamics of liquid rising is studied in the viscous regime. When the diameter of the tube is smaller than the capillary length, the center part of the meniscus rises with time $t$ following a $t^{1/2}$-law, while the tongue is truncated at a height which grows following a $t^{1/3}$-law. Sharp groove also facilitates release of gas bubbles trapped inside a capillary under the action of gravity.

Abstract:
This paper reviews the factors affecting the distribution of the nucleation site density in nucleate boiling and then uses the fractal theory to discuss the relationship between boiling surface microstructure information and the nucleation site density and study the data of the nucleation site density in two boiling experiments: one is to investigate the change of nucleation site density during the course of aging process,and the other is to investigate the difference of the nucleation site density on two boiling surfaces made of different materials.The result of experimental data analysis shows that the relationship between the nucleation site density and the minimum nucleation radius is fractal.Fractal dimensions are calculated and different fractal dimensions correspond to different boiling surfaces.The fractal dimension is a quantitative parameter describing the boiling surface character.

Abstract:
An analytic model for working fluids flowing through capillary tubes has been established with the approximate integral method. All the possible flow regimes in the capillary tubes, including subcooled, two-phase and superheated regimes, are covered in the model, and different analytic solutions are given respectively for each flow regime. As examples, the mass flow rates of refrigerants R12, Rl34a and R600a through capillary tubes are predicted by the model, and compared with those evaluated by a general distributed-parameter model. The mean bias falls into 1% and the maximum bias is 2.2%, while the computation speed of the new model is more than one order of magnitude higher than that of the distributed-parameter one.

Abstract:
We consider chromatic dispersion of capillary tubes and photonic crystal fibers infiltrated with liquid crystals. A perturbative scheme for inclusion of material dispersion of both liquid crystal and the surrounding waveguide material is derived. The method is used to calculate the chromatic dispersion at different temperatures.