The Mass and Heat Transfer Characteristics Study of the Natural Convection Evaporation of an LNG Droplet in BOG

The evaporation process of LNG droplets in BOG is closely related to the cooling down process of the LNG tank, but there isn’t an available droplet evaporation model at present. Been prepared based on the conservation of mass, momentum, and energy, a CFD model of natural convection evaporation of a single LNG saturated droplet in the BOG was developed and applied. The results show that:①There are two distinguished zones around the droplet surface, where the local temperature boundary layer of the droplet gradually thickens and rapidly thickens with the increase of the angle of inflow from 0 ° to 90 ° and from 90 ° to 180 °, respectively; ② With the increase of droplet size, the average thickness of temperature boundary layer increases gradually, which leads to the decrease of relative evaporation rate;③“blowing effect” remains almost unchanged with the increase of droplet size.

Investigation of Heat Transfer Efficiency of Improved Intermig Impellers in a Stirred Tank Equipped with Vertical Tubes

The heat transfer of a reactor with improved Intermig impellers was numerically investigated by the finite element method (FEM) simulation software Fluent (V.19). A turbulence model utilized the standard k-ε model, and the turbulent flows in two large vortexes between vertical tubes were collided to form a strong convection. The influence of heat and mass transfer developing from the impeller diameters, the distance between the two impellers (C1), the rotational speed and the installation height of the bottom impeller (C2) were studied. The reactor was equipped with special structure vertical tubes to increase the heat exchange areas. The rate of heat transfer, including criteria such as the convective heat transfer coefficient, the Nusselt number of outside vertical tubes, and the temperature boundary layer thickness, assured the accurate control of the heat exchange mixing state. The experimental testing platform was designed to validate the simulated results, which revealed the influence order of related factors. The Nusselt number Nu was affected by various related factors, resulting in the rotation and diameter of impellers extending far beyond the distance between the two impellers (C1) and the installation height of the impeller (C2). The average temperature boundary layer thicknesses of the symmetrical and middle sections were 3.24 mm and 3.48 mm, respectively. Adjusting the appropriate parameters can accurately control the heat exchange process in such a reactor, and the conclusions provide a significant reference for engineering applications.

Experimental Study of a Boundary Layer on a Heated Flat Plate

Boundary layer on a uniformly heated flat plate was studied experimentally. Both, the velocity boundary layer and the temperature boundary layer, was investigated by means of hot-wire anemometry. A probe with parallel wires was used for velocity-temperature measurement. Experiment was performed in the closed-circuit wind tunnel with several levels of heat flux at the wall. The wall temperature was set up in the interval from 20 ºC to 200 ºC.

Dual Solutions for Unsteady Stagnation-Point Flow of Prandtl Nanofluid Past a Stretching/shrinking Plate

Dual solutions for the time-dependent flow of a Prandtl fluid containing nanoparticles along a stretching/shrinking surface are presented. The nano Prandtl fluid fills the porous stretching/shrinking surface. The Buongiorno model is employed by accounting Brownian motion and thermophoresis slip mechanisms in the analysis. The relevant nonlinear problem is treated numerically via Runge-Kutta-Fehlberg scheme. The flow profiles are scrutinized with respect to the different governing parameters. Results of this study indicate that the temperature boundary layer thickness increased due to the influence of nanoparticles.

Temperature boundary layer on a rotating surface - the problem of the constant temperature wall

Introducing the group of Loitskanskii [1] form-parameters and transformations of Saljnikov [2], the set of governing equations of the in compressible laminar temperature boundary layer was transformed in the universal form, with Prandtl number as parameter, for the case of the constant wall temperature. Using the universal results for air (Pr=0.72) the procedure for calculation of the Nusselt number (dimensionless heat transfer coefficient) on the particular contour (airfoil NACA 0010-34) was developed. The dimensionless temperature profiles within the boundary layer were presented also. The parameter of rotation ?0, as well as Eckert number, was varied, and their influences on the heat transfer from the surface to the working fluid were presented and analyzed. .