CHF is the maximal limit of heat flux in boiling heat transfer, therefore, it is a crucial parameter that has a fundamental impact on the security and economy of the nuclear system. An experimental investigation was carried out in the present study to identify the dominant CHF mechanism in a narrow rectangular channel at different gap sizes (2 mm and 3 mm). The visualization experiments were performed

The maldistribution in the parallel multiple channels commonly leads to a reduction in the efficiency of heat exchangers and even causes the equipment to suffer the risk of failure. The distribution of gas–liquid two-phase slug flow when moving through the parallel multiple channels is still an unresolved problem and limited by the lack of experimental data. This work presents an experimental study

The magnitude of surface heat flux and its accurate estimation are very crucial owing to their applicability in impulsive thermal loads for high-speed flights. The correctness of such heat flux is associated with the implications from highly responsive thermal sensors in ground-based aerodynamic studies. In the present study, the performance effectiveness of an indigenous, in-house-made coaxial thermal

Condensation of steam at a low mass flux inside an inclined tube was experimentally investigated to aid the optimal design of air-cooled passive heat exchangers for advanced LWRs. While varying downward inclination angle from 0 to 90°, the heat transfer coefficient monotonically improved by more than 15% while previous studies that have used refrigerants have reported that the optimal angle is between

The denoising of Lagrangian trajectories based on regularized B-spline is investigated. The aim is to find systematic criteria for optimization of algorithms used in 4D-PTV in order to optimize the quality of 4D-PTV measurements of turbulent flows as well as high-order of turbulence statistics. We introduce and adapt to this context two innovative tuning strategies which are commonly used in the Tikhonov

Natural convection heat transfer from three isothermally heated horizontal cylinders submerged in water in a triangular arrangement is investigated. Two configurations, named here as one over two and two over one, are characterised for three cylinder spacings (S = 2, 3 and 4 cylinder diameters) and Rayleigh number conditions (Ra = 2×106, 4 × 106 and 6 × 106). Combined local heat flux measurements and

The current work presents a study of qualitative relationships between the flow unsteadiness, induced by nozzle geometry variation, and non-equilibrium condensation behavior at high temporal scales for supercritical carbon dioxide (sCO2) flow. A closed sCO2 loop facility is used to drive a supercritical carbon dioxide flow through a rectangular converging–diverging channel. As the flow traverses through

The combustion of an oxygen/paraffin hybrid rocket motor was experimentally characterized. Firing tests were conducted for different oxidizer mass fluxes ranging from 2.47 to 3.40 g/ (cm2·s). Variations in temperature and H2O partial pressure at the nozzle exit were diagnosed using mid-infrared tunable diode laser absorption spectroscopy (TDLAS) based on H2O absorption near 2.5 μm. Three H2O absorption

Coupling structures of buoyancy induced thermal convection in two immiscible layers with and without weak background rotation were investigated in laboratory experiments using a glycerol solution and a silicon oil as the test fluids. A cylindrical vessel was employed to yield three-dimensional (3D) development of the two-layer convection, and the influence of background rotation on convective motion

In this study, the placement of a micro-vortex generator (VG) upstream of the film cooling hole is proposed to improve the film cooling performance. The film cooling effectiveness and flow characteristics at three blowing ratios (M = 0.2, 0.4, and 0.8) are measured by using pressure-sensitive paint (PSP) and particle image velocimetry (PIV), respectively. The results indicate that the VG upstream of

Two-phase pressure drop is studied in a transparent cross-corrugated channel for uniform and non-uniform gas–liquid distribution. Both uniform and non-uniform distribution are created by injecting air and water through different numbers of nozzles directly into the channel. The frictional pressure drop clearly indicates the impact of maldistribution. The single channel is pivot-mounted to allow horizontal

Variations in fluid temperature are the most important error source in hot-wire anemometer measurements and must sometimes be compensated for. Although many temperature compensation schemes have been proposed over the years, no consensus seems to be reached regarding correction methods. In this paper new precision measurements on heat transfer from heated wires have confirmed that, provided the fluid

Hydraulic jumps occur commonly in natural channels and energy dissipation systems of hydraulic structures in the violent transition from supercritical to subcritical flows. They are characterised by large flow aeration, high turbulence and strong fluctuations of the free surface and the jump toe. For free surface measurements, fast-sampling, fixed-point instruments such as acoustic displacement meters

Multiple orifice synthetic jet devices are becoming widely utilized for active flow control and jet impingement cooling, due to its mixing performance resulting from the vortices and jet interaction. Therefore, understanding the flow interaction between multiple synthetic jets is crucial in maximizing the potential for many industrial applications. In the present study, an experimental investigation

The boundary layer detachment limits compact power plants' operation at moderate Reynolds number in adverse pressure conditions. Flow detachment is promoted by the lack of momentum in the near-wall region when exposed to adverse pressure gradients. Transient flows or periodic flow perturbations may delay or prevent the flow detachment. The present investigation experimentally analyzes the behavior

Experiments were conducted to explore the droplet generation process when an ascending liquid spray impacts on a downward-facing solid surface. The droplets generated in the present experiments were classified into the two types: one is the splashing droplets generated by the impacts of droplets in spray and the other is the falling droplets produced from a liquid film formed on the solid surface.

Fuel concentration information is critical to the development of high-efficiency combustion system of direct-injection natural gas engines. In this study, a one-dimensional (1-D) measurement approach based on laser induced breakdown spectroscopy (LIBS) is developed to quantitatively measure 1-D fuel concentration distributions in gas jets at high ambient pressures. Except for the spectral dimension

Shockwave propagation from focused-laser-induced plasmas was characterized for implementing calibration-free seedless velocimetry. An emission-free probe beam deflection (EF-PBD) technique and short-gated shadowgraph/schlieren imaging were used for the investigation. Nanosecond laser pulses at 532 nm were focused to induce plasmas generating shockwaves from the focal point at atmospheric condition

The effects of hydrogen(H2) on the macroscopic explosion parameters and microscopic chemical kinetics of methane(CH4)-air mixtures were investigated. First, the effect of H2 on the flammable limit of CH4 was studied with a. standard test device. Second, the explosion characteristic parameters of CH4-H2-air mixtures were measured in a standard 20-L spherical chamber, including the maximum explosion

Electrohydrodynamic (EHD) enhancement of water droplet evaporation by non-uniform electric field and the subsequent dynamic characteristics were experimentally investigated in this paper. A pin-to-plate electric field was produced by a needle connected to a high-voltage power supply and the grounded heated surface coated by thin Teflon film with a contact angle of about 100°. The droplet was generated

Diffusers are vital components of vertical wind tunnels. In this experimental study, the velocity distribution, pressure recovery coefficient, turbulence intensity, and flow separation of a 1:13 model of a diffuser with an octagonal inlet and square outlet for use in the skydiving vertical wind tunnel have been investigated. The experiments were carried out both in suction and blowing flow modes. Results

Recent advancement in electrowetting technique has attracted the attention of researchers due to its numerous applications in lab-on-chip microfluidic devices. In the present work, an interdigitated electrode (IDE) configuration is introduced for producing oscillating droplets for heat dissipation in electronic devices. It resolves the problem of interfering wire used as an electrode in conventional

The effect of Reynolds number on turbulent boundary layer under adverse pressure gradient has been barely investigated in the available literature. So far, experimental or numerical research on that issue were performed either for low Re or for low range of Re to capture its clear effect on flow statistics. Hence, the purpose of the present paper is to examine whether the effect of Reynolds number

This study presents a method that can be used to accurately determine the thermal performance of a cylindrical heat pipe. In the method, the heat pipe is placed between two stainless steel 304 cylindrical blocks, configured as radial calorimeters that achieve thermal contact with the evaporator and condenser sections of the pipe. A flexible isothermal electrical heater mat surrounds the evaporator

When the water inventory evaporates during a hypothetical loss of coolant accident in the core of a pressurized water reactor, the fuel rods temperature increases substantially, resulting in the clad ballooning and the formation of blocked sub-channels. During the reflooding phase, where water is injected into the core and a steam-droplets flow is created above the water level, the presence of ballooned

Vertical entry of a 213 mm diameter solid sphere moving with a low speed of 16–40 mm/s onto a shallow liquid layer is investigated experimentally. The focus of the study is on deformation of the free surface before the actual contact between solid and liquid in presence of air cushioning. Owing to local character of air cushioning, the sphere is modeled by a spherical segment. The measurements were

When monitoring wall temperatures in reactors and combustion chambers using infrared cameras, significant measurement errors occur due to the reflection of hot objects such as flames. The radiation received in the camera from the measured wall segment results from the sum of inherent wall radiation and reflected radiation. The reflection depends on the geometrical arrangement of wall, flame and camera

An experimental investigation is conducted to understand the flow behavior near a stack in a hybrid thermoacoustic system including resonator and looped-tube. Time-resolved particle image velocimetry measurement is applied to obtain the evolution of the local oscillating flow. Phase-averaged results show two types of vortices in the flow field due to the stack: the primary vortices attaching at the

The present study investigates the influence of liquid properties and port position on draining characteristics from a square tank. Four different liquids, water, kerosene, glycerol 20%, and glycerol 60% are used. Three different port positions of a drainpipe of 9 mm id are used. Bubbly, slug, churn, elongated slug, and annular flow are observed in the drain port. Slug and bubbles never collide and

In this paper, based on the traditional low-frequency self-excited oscillation pulsed jet device, a self-excited aspiration pulsed jet device is designed. For the structural parameters, including the aspiration capacity, impact characteristics, and pulse generation mechanism, the jet impingement is analyzed experimentally under the aspiration and non-aspiration conditions. It was found that, compared

Entrainment of air bubbles into flowing water increases significantly the interfacial area between the two phases hence enhancing the air-water mass transfer. The air bubble characteristics are thus of direct relevance to the waterbody aeration and oxygenation, which should be understood in the context of bubbly-flow turbulence development. In this paper, we studied experimentally a canonical aerated

This study experimentally investigates the dynamic behaviors of water droplets over wide ranges of diameters and velocities (200 μm < D0 < 2600 μm, 50 < We < 3000) impacting on surfaces with various wettability (ranging from hydrophilic to superhydrophobic), and focuses on the effect of surface wettability on water droplet spreading and splashing. The experimental results show that the surface wettability

This paper considers the modes of plasma-stabilized supersonic combustion in a cavity-based flameholding configuration. The testing was performed in the SBR-50 supersonic facility at the University of Notre Dame under the following conditions: Mach number M = 2, stagnation pressure and temperature P0 = 1–3.2 bar, T0 = 295–750 K, and an ethylene injection rate of ṁC2H4 = 0–8 g/s. A rail type electric

A novel metal “endoscopic” two-phase closed thermosyphon (METPCT) which could be used to intuitively investigate the phase-change heat transfer and two-phase flow characteristics were developed. The visualized experimental set-up was established by using a rigid borescope and a high-speed camera. The phase-change heat transfer characteristics of the internal working fluid inside the METPCT under various

In this work, a new comprehensive dataset about bubble sizes in flow boiling of water is presented. The experimental setup basically consists of a lower copper heated plate embedded in a horizontal rectangular channel flow. Several experimental conditions, ranging bulk velocities: 0.1–0.9 [m·s−1]; mass fluxes: 96.9–871.8 [kg·m−2·s−1]; subcooling degrees: 16–36 [°C]; heat fluxes: 200–650 [kW·m−2] and

Reliable and accurate prediction of the transition from spherical cap bubble to slug flow is crucial not only to the operation of industrial facilities such as the crude oil pipelines, bubble column, and nuclear reactors but also for model development for computational fluid dynamics (CFD) studies. The present paper presents a review of the transition mechanics from spherical cap bubble flow to slug

The local dynamics of fluidized pharmaceutical carrier powders in a turbulent channel flow was studied using particle image velocimetry (PIV) and High-speed, long-distance microscopy (HS-LDM). Four different lactose powders which have been used as a drug carrier in dry powder inhalers were used in this study. These powders have median powder particle diameters ranging between 61 and 121 µm. Air flow

Previous work has shown that heat transfer into a plane conducting surface affects shock wave reflection properties. In the more complex reflection case of a curved surface the situation would be different because of the increased number of reflection patterns, with a rapid change in reflection geometry as the wave propagates up the surface. Test pieces of different thermal conductivities (0.19 W/mK

Effects from turbulence levels created by a three-cylinder rotating system on the flow over a dimpled surface of an airfoil are reported. The three-cylinder rotating system effect is tested on the flow over a NACA0015 with leading-edge dimples at various angles of attack at Reynolds numbers of 0.5 × 105 and 1.0 × 105 in a low-speed wind tunnel. To the effect of mimicking free-stream flow perturbations

The results of an experimental study concerning wall boundary effects on the lock-in behavior of the shedding vortex of a circular cylinder, which is forced to oscillate transversely in a uniform flow at moderate Reynolds number Re = 2000, are presented in this paper. A height-adjustable flow channel is designed to study the boundary effect. Two sets of experiments are organized to study the lock-in

Three-dimensional trajectories of gas bubbles were the subject of study in this article. Authors carried out experiments in two glass tanks with dimensions of 300 × 300 × 1500 mm and 300 × 150 × 500 mm, respectively, filled with distilled water with a temperature equal to T = 21 ± 1 °C. The tests were carried out for an air volume flow rate, values from 0.00492 l/min to 0.0645 l/min. Basic characteristics

A novel methodology based on the zero-crossing rate (ZCR) is introduced to diagnose combustion instability (CI) in a combustion system. This method can assess the combustion status by counting the number of points of dynamic pressure (DP) signals crossing zero in a cycle, and quantifies the cyclic variation of the number of crossing points. To validate the feasibility of this method, transition experiments

This study is an experimental investigation into the self-similarity behavior of first and second order statistical quantities derived from a jet flow based on a) the original data and b) its low-order representations derived from the Proper Orthogonal Decomposition (POD) and c) a comparison of both. The flow under investigation is an air-helium turbulent round jet with Re≈15400 emerging from a tube

Ethanol is a renewable, clean fuel and is usually blended with gasoline to be used as an alternative fuel for internal combustion engines. In the present study, the instability development and cellular structure evolution of a spherically expanding flame of E30 (gasoline blended with ethanol of 30% liquid volume) are investigated. By processing the flame images, the equivalent diameters of cells on

An experimental study is conducted on pulsed spray cooling heat transfer on a vertical surface under controlled nozzle pressure. Nozzle flow rate is found to be directly proportional to the duty cycle when the nozzle pressure is maintained constant and hence fixed at 2 bar throughout the investigation. The temperature fluctuates on the heated surface due to the interaction of the injection/non-injection

Experimental results of flow pattern and heat transfer in circular-orifice baffled tubes under pure oscillatory flow and compound flow conditions are presented. The hydrogen bubble visualization technique is employed for describing the unsteady flow structure, and particle image velocimetry is used in order to measure the velocity field during eight different phases of the oscillation cycle. The existence

In a rotating detonation engine, detonation waves propagate in the combustor chamber with one side unconfined which will introduce lateral relief and, therefore, results in deficits of the propagation velocity and the peak pressure. To study the critical mixture height for detonation propagation, a simple combustor without considering the curvature has been used, which provides a planar semi-confined

The gas-liquid cylindrical cyclone (GLCC) is a device used to separate gas from liquid in offshore or subsea oil and gas production systems. The liquid film swirling along the upper cylinder wall in the GLCC is referred to as “upper swirling liquid film” (USLF). The flow patterns of USLF have a great influence on GLCC’s separation performance. However, the dynamics of the gas-liquid flow in a GLCC

The turbulent wake velocity fields around a short wall-mounted square cylinder of aspect ratio 2 fully immersing into a thick turbulent boundary layer are obtained experimentally with PIV and numerically with LES. Comparison between the two sets of data is made on the time-averaged mean velocities, turbulent fluctuating velocities, and the detailed characteristics of energetic large-scale coherent

Turbulence generators such as a 25.4 mm tall, 12.7 mm wide (W) and 0.1 mm thick rectangular flexible strip can provide a robust means of enhancing convective heat transfer. This wind-tunnel study aimed at uncovering the effect of freestream turbulence on heat convection enhancement of a flat surface by a flexible strip. The freestream turbulence was furnished by a 6 mm thick orificed perforated plate

Studying the effect of multiple air bubbles on the collapse strength of a cavitation bubble can aid in understanding the mechanism of air entrainment alleviating the cavitation erosion and enhance the aeration effects in hydraulic engineering. A cavitation bubble is generated by the spark-generated system. Air bubbles are arranged in three manners: two air bubbles on the same side, one air bubble on

The velocity fields of the laminar premixed flames with external acoustic excitation are studied in this work. The velocity fields in both burnt and unburnt regions have been experimentally investigated by PIV methodology. Different acoustic modulations have been applied to the flames. Dynamical mode decomposition (DMD) is adopted to elaborate the interaction mechanisms between flames and acoustics

To understand the mass transfer mechanism of 90° elbows, a comparative study of mass transfer measurements and oil-flow visualization with image analysis is carried out for long and short 90° elbows in the Reynolds numbers Re = 5 × 104 –2 × 105. The mass transfer distributions are evaluated by using the plaster-dissolution method, while the oil-flow fields are quantitatively visualized by oil-flow

Turbine vane leading edge features the highest heat load and is effectively protected by multi-row film-ejections. In present work, time-resolved planar quantitative light sheet (QLS) technique was proposed to acquire unsteady behaviors of film coverage and jet-trajectory caused by fluid-interaction. Under proper calibrations, the uncertainty of transient concentration measurement was controlled below

We experimentally explored the distinct effects induced by the geometry of various axisymmetric orifices in the near and intermediate regions of jets at a Reynolds number of Re≈105 based on the diameter, d=10 mm, of the orifices. The orifices inspected had thicknesses of ∊/d=0.2, 1 and 2 and divergence angles of θ=0∘,20∘ and 45∘. High-speed planar particle image velocimetry (PIV) was used to characterize