Flashing spray occurs when the saturated liquid is discharged into a gaseous environment at an ambient pressure lower than its saturation pressure. Internal flow is a primary determinant on the behavior of external fl...
详细信息
Flashing spray occurs when the saturated liquid is discharged into a gaseous environment at an ambient pressure lower than its saturation pressure. Internal flow is a primary determinant on the behavior of external flashing spray, so its transient effect was investigated with iso-pentane as working medium. The coupled effect of superheat level and injection pressure was comprehensively explored with initial temperature from 30 degrees C to 70 degrees C and injection pressure from 1.2 MPa to 2.4 MPa. Under different injection pressure, the stable spray patterns can still be categorized as non-shattering, partially shattering, completely shattering and flare flashing separated by the shattering index X center dot(P-inj/P-a)(0.5) of 0.21, 0.39 and 0.76, which represents the product of homogeneous nucleation rate and the ratio of injection pressure over ambient pressure. A strong correlation between the spray cone angle and the shattering index is proposed as a piecewise function separated by X center dot(P-inj/P-a)(0.5) = 0.39. High-void -fraction internal two-phase flow is easier to be formed in partially shattering or completely shattering pattern, which would lead to a hysteretic flashing spray with a significant increase of spray cone angle and droplets concentration. Low X center dot(P-inj/P-a)(0.5) yields slower response of external morphological changes but larger enhance-ment of radial expansion.
The spray cooling of moving hot solids is widely performed in the steel industry. Understanding flow and heat transfer when droplets impinge on moving hot solids is important. By simultaneous visualization with flash ...
详细信息
The spray cooling of moving hot solids is widely performed in the steel industry. Understanding flow and heat transfer when droplets impinge on moving hot solids is important. By simultaneous visualization with flash photography and temperature measurement using thermography, the flow and heat transfer of a droplet train obliquely impinging on a moving solid at high temperatures was experimentally investigated. A rectangular test piece (SUS303) was heated to 500 degrees C at a moving velocity,of 0.25-1.5 m/s. The test liquid was water at approximately 25 degrees C. The pre-impact droplet diameter, impact velocity, and inter-spacing between two successive droplets were 0.69 mm, 2.2 m/s, and 2.23 mm, respectively. The tilt and torsional angles were 50 and 30-60, respectively. No coalescence of droplets was observed;the droplets deformed independently on the moving solid, even though the torsional angle generated a velocity component along the width of the solid. The surface temperature of solid after droplet impingements depended on the experimental conditions. Wavy temperature profile was obtained when the moving distance of solid was large during two successive collisions. The temperature changed continuously for the small distances. In this regard, a simple model considering droplet movement, collisional deformation behavior, and solid migration can explain this phenomenon by the overlap of the cooling regions of the droplets. Furthermore, experimental and numerical analyses show that the heat removal rate of individual droplets is constant at approximately 12.5 MW/m(2) and depends on the total contact time when multiple droplets collide.
This paper introduces a new 2-D flow visualization method to produce fast LIC-like images. The method is designed to combine characteristics of three classic flow visualization methods: the time efficiency of streamli...
详细信息
With the development of deep learning(DL)techniques,many tasks in flow visualization that used to rely on complex analysis algorithms now can be replaced by DL *** reviewed the approaches to deep learning technology i...
详细信息
With the development of deep learning(DL)techniques,many tasks in flow visualization that used to rely on complex analysis algorithms now can be replaced by DL *** reviewed the approaches to deep learning technology in flow visualization and discussed the technical benefits of these *** also analyzed the prospects of the development of flow visualization with the help of deep learning.
Results of an experimental study of the supersonic mixing layer are reported, concerning the evolution characteristics of the vortex structures. Experiments are conducted in a supersonic mixing wind tunnel with a conv...
详细信息
Results of an experimental study of the supersonic mixing layer are reported, concerning the evolution characteristics of the vortex structures. Experiments are conducted in a supersonic mixing wind tunnel with a convective Mach number of 0.17. The superhigh frequency Nano-tracer Planar Laser Scattering (NPLS) technique is applied to visualize the flow patterns. The first time the spatial and temporal evolution characteristics of the vortex structures are captured. For the supersonic mixing layer, the initial section is dominated by translation, tension and rotation, while the rear section is dominated by mixing, blending and crushing.
The present study proposes to design, fabricate and investigate a miniature supersonic wind tunnel at an affordable cost, safe to operate, and reliable for education purposes. The configuration consists of a high pres...
详细信息
An experimental study on the traveling crossflow instability over a 60∘swept flat plate was *** Mach number is 6,the angle of attack of the model is 5∘.The traveling crossflow waves and the secondary instability of ...
详细信息
An experimental study on the traveling crossflow instability over a 60∘swept flat plate was *** Mach number is 6,the angle of attack of the model is 5∘.The traveling crossflow waves and the secondary instability of the traveling crossflow waves were visualized by nano-tracer-based planar laser scattering(NPLS)*** the spanwise NPLS images,the traveling crossflow waves appeared as regular strikes,and the secondary instability appeared as small eddies attached to *** wavelet transform was used to study the wavelength contents of the traveling crossflow *** most amplified wavelength is stable before the secondary instability happening,which is around 12 mm at Re_(∞)=3.45×10^(6)m^(−1).Besides,the Reynolds number effects on the boundary layer transition and traveling crossflow instability were discussed.
Experimental flow visualization is a valuable tool for analyzing microfluidics and nanofluidics in a wide variety of applications. Since the late 1990s, considerable advances in optical methods and image postprocessin...
详细信息
Experimental flow visualization is a valuable tool for analyzing microfluidics and nanofluidics in a wide variety of applications. Since the late 1990s, considerable advances in optical methods and image postprocessing techniques have improved direct optical measurements, resulting in an accurate qualitative and quantitative understanding of transport phenomena in lab-on-a-chip capillaries. In this study, a comparison of different optical measurement techniques is presented. The state-of-the-art development of particle image velocimetry (PIV) to date, particularly in microscale applications, is reviewed here in detail. This study reviews novel approaches for estimating velocity field measurements with high precision within interrogation windows. Different regularization terms are discussed to demonstrate their capability for particle displacement optimization. The discussion shows how single- and multi-camera optical techniques provide two-dimensional and three-component velocity fields. The performance of each method is compared by highlighting its advantages and limitations. Finally, the feasibility of micro resolution PIV in bioapplications is overviewed.
This research discusses single-phase fluid flow conditions at low Reynolds number (Re) in the heat exchanger with a dimple structure of the heat plate. flow at 70 = 469, a fully developed turbulent flow was found in t...
详细信息
This research discusses single-phase fluid flow conditions at low Reynolds number (Re) in the heat exchanger with a dimple structure of the heat plate. flow at 70 <= Re <= 469 was investigated with laboratory experiments and computational fluid dynamics. It was found that in such a channel, two flow regimes exist, i.e., dead and live regimes. The volumetric fraction of the deadly regime gets bigger with increasing Re. At Re >= 469, a fully developed turbulent flow was found in the channel. Numerical analysis was made with a laminar flow model and two turbulence models, Realizable k- epsilon with an enhanced wall treatment and k - omega SST. The Realizable k- epsilon turbulent model with an enhanced wall treatment predicts pressure drop and shape of the live and dead regime more consistent with the real conditions in the channel. At the lowest considered Re = 70, computational fluid dynamics solutions deviate from laboratory experiments by - 10.3 %. As the Re increases, the difference increases and reaches - 18.3 % at Re = 141. As Re continues to increase, the result decreases and stabilizes at - 8.3 %.
暂无评论