High-speed Airflow Research Articles

Investigation of Water Film Dynamics on the Surface of an Airfoil in a High-Speed Flow and Subsequent Ligament Formation and Breakup from the Trailing Edge

Abstract In this work, the dynamics of a liquid film on the surface of NACA 0012 airfoil placed in a high-speed air flow is investigated. Experimental studies were carried out to assess the film thickness, droplet shedding, and the dynamics of the sheet. In the present work, air velocities up to 175 m/s were used with water films flowing between 1.4 and 2.6 cm2/s. The water was introduced on the airfoil via 26 holes each measuring of 0.5 mm holes separated by 1mm at 35 mm downstream of the leading edge of the vane. The results were obtained using four experimental tools. The first is a point measurement of the time-resolved film thickness using a confocal laser induced fluorescence method. Second is time averaged images of the film thickness on the entire vane surface. Third, high speed videos are obtained to study the accumulation and breakup of the liquid at the trailing edge of vane. Finally, laser diffraction and Phase Doppler interferometry were used to document the spray dynamics. The results illustrate that the average film thickness decreases with air velocity and increases with the water flow rate. Also, the dominant frequency of liquid film wave, ligament breakup length, drop size and spray concentration increase with the air velocity and is modestly affected by water flow rate. Finally, design tools are provided to predict the average film thickness and dominant frequencies of the film thickness, ligament breakup, spray concentration and droplet average size.

Study on Atomization Mechanism of Oil Injection Lubrication for Rolling Bearing Based on Stratified Method

The atomization mechanism of lubrication fluid in rolling bearings under high-speed airflow between the rings was investigated. A simulation model of gas–liquid two-phase flow in angular contact ball bearings was developed, and the jet lubrication process between the bearing rings was simulated using FLUENT computational fluid dynamics software (Ansys 19.2). The complex motion boundary conditions of the rolling elements were addressed through a layered approach. We can obtain more accurate boundary layer flow field changes and statistics of the diameter of oil particles in lubricating oil atomization, which lays the foundation for analyzing the law of influence on lubricating oil atomization. The results show that as the number of boundary layer layers increases, the influence of the boundary layer flow field on the lubricating oil is more obvious. The oil particle size is excessively flat, and the concentration of large particles of oil appears to decrease. As the speed increases, the amount of oil in the cavity decreases, but the oil droplets are also fragmented, which intensifies the atomization and reduces the particle diameter. This reduces the Sauter Mean Diameter (SMD), which is not conducive to the lubrication of the bearing. Under different injection pressures, when the injection pressure is large, it is beneficial to the lubrication of the bearing.

High-speed airflow influence on adhesion performance of fibrillar adhesive

High-speed airflow influence on adhesion performance of fibrillar adhesive

New intraoral digital impression with pneumatic gingival retraction used in the restoration of crown for posterior teeth: a case report

In fixed prosthodontics, clear exposure of the preparation margin is the prerequisite for obtaining accurate digital impressions and improving the marginal fit of restorations. To resolve the issues associated with the cord retraction technique, such as pain, acute injury, and prolonged procedural time, this study proposes a new technology for intraoral digital impression taking with pneumatic gingival retraction. The new scanning head blows a high-speed airflow that instantaneously separates the free gingiva, locally exposing the subgingival preparation margin. Combined with the farthest point preservation stitching algorithm based on the distance from the normal vector and high-speed laser scanning photography, it achieves global preparation edge data and gingival reconstruction, realizing painless, non-invasive, and efficient precise acquisition of the preparation margin. Using this new technique, a patient with a full porcelain crown restoration on a posterior tooth was treated. The digital impression revealed a clear margin of the preparation, and the crown made from this data has a good marginal fit.

Numerical Simulation and Parameter Optimization of a New Slant Insertion-Opening Combination Sand Fence

This paper presents a new slant insertion-opening combination sand fence designed to reduce the hazards of traditional railway sand damage along the line. This new fence aims to decrease the disturbance caused by lateral wind on the high-speed railway and minimize the deposition of track sand particles. Numerical modeling and wind tunnel testing were employed to examine the structure’s defensive capabilities. Using the computational fluid dynamics (CFD) method and the Eulerian–Eulerian two-fluid model, the wind protection effect and airflow characteristics of the new sand fence with different slant insertion angles and spacings were simulated, and the optimal configuration parameters were selected. The study found that the new mechanical sand fence exhibits similar performance to the traditional sand fence. Since there is a “narrow tube effect”, the leeward side of the inclined plate generates a local high-speed airflow zone. In the top acceleration zone, the new mechanical sand fence efficiently lowers air velocity, thereby enhancing its protective capabilities. Moreover, the optimal protective performance of the new mechanical sand fence is achieved with an inclination angle of 15°, with improved protection observed as the angle increases. Additionally, the protective performance of double rows of these fences is influenced by the spacing between them. Increasing the distance between the two rows enhances protective performance, with the optimal protection achieved at a spacing of 25H. Beyond this distance, protective performance decreases.

Research on tribological properties of new Ni-based single crystal alloy containing Re

Abstract The particles in high-temperature and high-speed airflow in the battlefield environment will form sliding friction and wear on the aeroengine turbine blades, thus reducing the service performance of the blades. However, few studies has been reported on the tribological properties of Ni-based single crystal alloy. Accordingly, the tribological properties of Ni-based single crystal alloys with different contents of Re (0 wt%, 1.5 wt%, 2.5 wt%, 3.5 wt%, 4.5 wt% and 5.5 wt%) are investigated by tribological experiments and molecular dynamics simulations in this paper. The results of tribological experiments show that Ni-based single crystal alloy without Re exhibits the characteristics of abrasive wear and adhesive wear, while the wear state is significantly improved after adding Re element. In particular, the worn surface of Ni-based single crystal alloy containing 5.5% Re (NSCA5) is the smoothest and only a few minor defects are observed. In addition, the micro-tribological characteristics of Ni-based single crystal alloy are analyzed by molecular dynamics simulations, the results show that Re atoms can inhibit the dislocation movement and reduce the system potential energy, which enhance the stability and hardness of Ni-based single crystal alloy, thereby the wear resistance of the material are improved.

Alterations in nasal airflow and air conditioning after endoscopic nasopharyngectomy for recurrent nasopharyngeal carcinoma: a pilot computational fluid dynamics study

Endoscopic nasopharyngectomy represents a significant intervention for recurrent nasopharyngeal carcinoma (NPC). Various surgical techniques, including transnasal and transoral approaches, are employed. However, the impact of these procedures on nasal airflow dynamics is not well understood. This computational fluid dynamics (CFD) study aimed to investigate alterations in nasal airflow and air conditioning following endoscopic nasopharyngectomy. A 55-year-old male patient with recurrent NPC was selected, whose CT data were utilized for image reconstruction. A preoperative model and two postoperative models, including the transnasal and transoral approach models, were established. The airflow patterns and various CFD parameters were analyzed. In the postoperative models, the high-speed airflow went along the soft palate and into the nasopharyngeal outlet, and there was the low-speed turbulence in the expanded nasopharyngeal cavity. Compared to the preoperative model, the postoperative models exhibited reductions in surface-to-volume ratio, nasal resistance, airflow velocity and proportion of high wall shear stress regions in nasopharynx. The changing trends of nasopharyngeal air temperature and humidity in the preoperative and transoral models were consistent. The heating and humidification efficiency decreased in the transnasal model compared to the transoral model. The endoscopic nasopharyngectomy for recurrent NPC affects the nasal airflow and warming and humidification function. The transoral approach has less influence on aerodynamics of the upper airway compared to the transnasal approach. From a CFD perspective, the endoscopic nasopharyngectomy does not increase the risk of postoperative complications, including the empty nose syndrome and the carotid blowout syndrome.

Numerical investigation on the interaction characteristics between the gaseous detonation wave and the water droplet

In this paper, the interaction characteristics between the gaseous detonation and the water droplet are numerically investigated, utilizing a modified compressible two-phase flow model coupling with detailed hydrogen-oxygen chemistry. Firstly, an analysis is conducted on the propagation behaviors of the cellular detonation obstructed by the droplet. It is found that the cellular detonation undergoes reflection, diffraction, local extinction, and re-ignition upon the obstruction, and these behaviors vary with the droplet relative positioning with multi-dimensional structures of the cellular detonation, particularly in terms of the extinction degree caused by the diffraction and the relative positioning of the re-ignition region. Further, the droplet deformation characteristics are detailly analyzed. It has been revealed that the deformation behavior of the shocked droplet under planar detonation is consistent with that under high-speed airflow. However, for the droplet shocked by the cellular detonation, several windward surface pits are induced due to impaction from transverse shocks and direct hitting of the triple-point. The emergence of these pits notably precedes the onset of surface instabilities caused by high-speed airflow erosion. Further investigation has revealed that post-detonation flow, through the entrainment effect of the central pit, progressively penetrates and segregates the droplet into upper and lower segments, and this penetrating effect heavily depends on the droplet relative positioning. Moreover, the side pit, whose presence is significantly determined by whether there is direct impaction of the triple-point on the droplet windward side, is crucial for the deformation around the droplet equator and the subsequent shedding of smaller droplets.

Innovative configurations for heat sink integrated with piezoelectric fans

Piezoelectric (PE) fans are gradually replacing conventional axial flow fans in the field of heat dissipation for microelectronics due to small size and high efficiency. However, the flow characteristic of PE fans was seldom considered when arranging heat sink fins, which could not utilize the fans’ advantages. Here, the design of fin arrangement based on the transient flow field generated by the vibration of dual PE fans in the channel was calculated and analyzed by CFD simulation and dynamic grid technology. Four zones with different flow field characteristics were found: Zones 1 and 4 which located inlet and outlet of the channel were Parallel flow zone. Zone 2 with vortices corresponds to the area ranges from the waist of blades to middle section of the channel was Multiple vortices flow zone. Zone 3 with high-speed vortices and jet flows corresponds to the area ranges from middle section of the channel to halfway downstream of blades region was Diffuse flow zone. Innovative configurations of heat sinks where fins arranged at the inlet and surrounding blades were designed according to the flow field characteristics: the loss of high-speed airflow to the inlet was prevented effectively and heat dissipation in the downstream heat sinks was dispersed by fins arranging in Parallel flow zone and Multiple vortices flow zone. The development and merging of high-speed vortices were strengthened by the inhomogeneous pin-fins arranging in Diffuse flow zone. The optimal coordination between the velocity field and the temperature gradient field among innovative configurations was found based on the field coordination analysis. Heat transfer performance was enhanced by new designs where the average temperature compared to conventional heat sink with PE fans was reduced by 16.7°. Our work provided a new fins arrangement to achieve uniform temperature distribution and high heat transfer performance for heat sink integrated with PE fans and would benefit the application in thermal management of high power devices integrated with PE fans.

Low-current gliding DC discharge in high-speed flows

Abstract A low-current gliding discharge (current range 1–5 A) in high-speed air flows of 100–250 m s−1 was experimentally studied. A high-voltage direct current source with a maximum voltage of 4.5 kV was used to create the discharge. The average electron concentration n e ∼ 1014 cm−3 and the plasma ionization degree were determined by measuring the Stark broadening of the hydrogen H β line (λ Hβ = 486.1 nm). The estimates of the electric field (E ∼ 100 V cm −1 ÷ 600 V cm−1) in the discharge positive column were found using time-synchronized high-speed video recordings and oscillograms. The gas rotational temperature T g = 7000–9500 K and the vibrational temperature T v = 7000–11 000 K were estimated using optical emission spectroscopy. Time-resolved spectroscopy is used to investigate the effective plasma channel spatial regions from which the N, NH, N2 +, O and OH molecules radiate. The difference of the obtained radii indicates the presence of a radial temperature gradient and inhomogeneous plasma composition in the discharge cross section. The possibility of using of gliding discharge to ignite hydrocarbon-air mixtures in the ramjet engines combustors has been experimentally demonstrated.

Mechanism Analysis of Rock Vitrification by Strip Laser Scanning.

The process of casing the wellbore in oil and gas drilling consumes a significant amount of time and economic resources. High-energy laser rock fracturing, as an efficient and cost-effective new approach, holds the potential to create a glass-like casing by irradiating the rocks as an alternative to traditional casing. The mechanism behind the vitrification of rocks using laser irradiation, a key factor in achieving glassified casings, remains to be studied. This paper, based on experiments involving scanning sandstone with a line laser, investigates the mechanism of rock vitrification using numerical simulations and X-ray diffractometers. The results demonstrate that the sandstone surface is transformed into glass after laser scanning, with multiple scans and the application of high-speed airflow helping to reduce the formation of bubbles and other phenomena. Furthermore, the speed of laser scanning showed a negative correlation with the laser ablation depth, glass thickness, temperature diffusion rate, and temperature gradient. Based on these findings, a groundbreaking method is proposed for creating high-quality glass by moving the laser to scan the rocks multiple times, offering insights for research into laser-manufactured wellbore casings. Furthermore, this approach holds promising prospects for enhancing and embellishing the exterior of structures and for in situ environmental modifications on planetary surfaces and beyond.

Effect of liquid properties on film behavior on the surface of an airfoil in a high-speed flow and subsequent atomization from the trailing edge

This study examines the behavior of ethanol or water films on the surface of a NACA 0012 airfoil placed in a high-speed air flow. New water film results complement previous measurements of time averaged ligament lengths and droplet sizes generated with the same airfoil. In addition, new data are obtained for ethanol. Air velocities up to 175 m/s are used with liquid flow rates between 1.4 cm2/s and 2.6 cm2/s. The liquid was introduced onto one side of the airfoil via 26 holes, each measuring 0.5 mm in diameter and spaced 1 mm apart. These holes are positioned 35 mm downstream from the leading edge and 65 mm upstream from the trailing edge. Film behavior on the vane is captured with front-lit high-speed video. The accumulation of liquid and breakup of ligaments are captured with backlit highspeed video. Phase Doppler interferometry is used to measure droplet size and simultaneous axial and pitch wise velocity 70 mm downstream of the trailing edge. Finally, laser diffraction is used to measure line averaged droplet sizes. The results indicate notable differences between ethanol and water films. The ethanol film spreads more extensively across the width of airfoil which is attributed due to its lower surface tension. The maximum ligament length for both liquids decrease with higher air velocity and increase with the liquid flow rate. A correlation for maximum ligament length is developed and captures the effect of liquid properties, flow rate, and air velocity. Furthermore, the variation in liquid volume flow rate did not impact droplet size. However, for a given air velocity, the Sauter Mean Diameter is found to depend on surface tension. On the dependency of droplet size on the Weber number, ethanol produced smaller droplet sizes at low values of Weber number. However, at relatively high Weber numbers, the droplet sizes for both water and ethanol were similar. This suggests that droplet size is influenced by factors besides surface tension at low Weber numbers but not at higher Weber numbers. In addition, the Nukiyama-Tanasawa model to fit the volume distribution curves is simplified by fixing p and q terms. Simplification makes the model easier to understand and implement.

Fragmentation of water-coal fuel droplets in the air flow

Relevance. An analysis of the current state of the global energy agenda shows that the problem of anthropogenic impact on the planet’s atmosphere by thermal energy facilities is one of the most important for humanity. At the same time, the growth in electricity consumption stimulates the introduction of ever new power generating capacities. For a long time, it was believed that the solution to this problem was the large-scale introduction of non-traditional renewable energy sources (wind generators and solar panels) into the overall balance of electricity generation. However, it is now becoming obvious that renewable energy sources cannot fully cover all electricity needs. The latter creates incentives for the commissioning of new thermal power plants, usually operating on coal fuel. But the main problem of coal energy – its anthropogenic impact – still remains unresolved. This situation creates the prerequisites for the development of new “clean” coal technologies with a full cycle of sequestration of combustion products. One of the most promising technologies for burning coal with low emissions is the combustion of coal in the composition of coal-water fuel. However, coal-water fuel technology has a number of disadvantages. One of the most significant is the high ignition delays of typical (with a characteristic size of 3–5 mm) droplets of coal-water fuel. One of the most promising methods for solving this problem is spraying coal-water fuel in an ultra-fine state (with a characteristic droplet size of 0.1–1 mm). Aim. Experimental study of the conditions and characteristics of crushing droplets of coal-water fuel in a high-speed air flow. Object. Coal-water fuel prepared on the basis of lean coal. Method. Special experimental stand to establish the main characteristics and conditions of dispersion of coal-water fuel droplets. Results. The results of experimental studies show that for stable fragmentation of typical droplets of coal-water fuel, the speed of the latter (during the spraying process) must be at least 40 m/s.

Reconstruction of particle distribution for tomographic particle image velocimetry based on unsupervised learning method

The development of deep learning has inspired some new methods to solve the 3D reconstruction problem for Tomographic Particle Image Velocimetry (Tomo-PIV). However, the supervised learning method requires a large number of data with ground truth as training information, which is very difficult to gather from experiments. Although synthetic datasets can be used as alternatives, they are still not exactly the same with the real-world experimental data. In this paper, an Unsupervised Reconstruction Technique based on U-net (UnRTU) is proposed to reconstruct volume particle distribution explicitly. Instead of using ground truth data, a projection function is used as an unsupervised loss function for network training to reconstruct particle distribution. The UnRTU was compared with some traditional algebraic reconstruction algorithms and supervised learning method using synthetic data under different particle density and noise level. The results indicate that UnRTU outperforms these traditional approaches in both reconstruction quality and noise robustness, and is comparable to the supervised learning methods AI-PR. For experimental tests, particles dispersed in cured epoxy resin are moved by an electric rail with a certain speed to obtain the ground truth data of particle velocity. Compared with other algorithms, the reconstructed particle distribution by UnRTU has the best reconstruction fidelity. And the accuracy of the 3D velocity field estimated by UnRTU is 12.9% higher than that from the traditional MLOS-MART algorithm. It demonstrates significant potential and advantages for UnRTU in 3D reconstruction of particle distribution. Finally, UnRTU was successfully applied to the high-speed planar cascade airflow field, demonstrating its applicability for measuring complex fluid flow fields at higher particle density.

Research of dust removal performance and power output characteristics on photovoltaic panels by longitudinal high-speed airflow

Photovoltaic (PV) panels' photoelectric conversion efficiency will decrease as dust deposition on their surface. An approach to dust removal on the PV panel's surface by longitudinal high-speed airflow was investigated to increase the output power. In this paper, commercial CFD software was used to numerically simulate the characteristics of dust removal by longitudinal high-speed airflow. The PV panels' output characteristic model under the action of dust removal by high-speed airflow is established by Simulink software, and the influence of high-speed airflow on the output characteristic is studied. Firstly, the dust removal mechanism of the PV panel under high-speed airflow is studied. Secondly, the impact of different tilt angles of the PV panel, dust particle size, airflow velocity, and blowing time on the dust removal effect of the PV panel surface were studied. The optimal airflow velocity and blowing time were obtained according to the airflow velocity and blowing time and their influence on the dust removal rate. Finally, the effect of high-speed airflow dust removal on PV power generation's efficiency and output characteristics is studied. The findings demonstrate that as the tilt angle increases, so does the dust removal rate increases continuously. In addition, the rate at which dust is removed increases with airflow velocity and blowing time. When the tilt angle is 30°, the best airflow velocity of dust removal is 5 m/s, and the best blowing time is 8 s. When the tilt angle is 45°, the best airflow velocity of dust removal is 10 m/s, and the best blowing time is 5 s. With the increase in airflow velocity and blowing time, the output power of PV panels continues to increase. When the airflow velocity is 10 m/s, and the blowing time is 5 s, 7.5 s, 12.5 s, and 15 s, the maximum output power after dust removal is increased by 15.44 %, 23.05 %, 23.38 %, and 23.39 %. This paper's research results can guide the design of the practical engineering application of longitudinal blowing high-speed airflow in the dust removal of PV panels.

Study on similarity criterion for fluid-thermal coupling responses of metal plate simultaneously exposed to laser irradiation and airflow

Similarity criterion considering the multifield coupling effect is essential for the scaled thermal test under both laser irradiation and airflow. This paper establishes the similarity criterion for the fluid-thermal coupling responses of metal plate simultaneously exposed to the laser irradiation and high-speed airflow by nondimensionalizing the governing equations. The main dimensionless parameters are obtained, and the scaling law when the temperature scaling factor is equal to 1, which means the temperature remains unchanged in the real and scaled model, is firstly established. Moreover, to broaden the applicability, the scaling law when the temperature scaling factor is not equal to 1 is further deduced, and the correction method based on numerical simulation is proposed to eliminate the error caused by the difference of temperature-dependent material properties in the real and scaled model. Numerical cases are conducted and compared to verify the established scaling laws. Results show that errors of the predicted fluid-thermal responses between the real and scaled model are less than 1 %, affirming the reliability of the scaling laws.

Research on the explosion vent external composite disaster induced by dust explosion inside the dust collector

With the help of computational fluid dynamics (CFD) technology, this research focuses on the quantitative effects of the explosion venting area (S), static opening pressure of the vent (Pstat) and dust cloud concentration (CD) on the explosion overpressure, high-speed airflow and high-temperature flame in the explosion venting zone. The results show that the explosion disaster along the explosion venting zone in general shows an oscillating fluctuating trend of attenuation, and the closer to the explosion vent explosion disaster is more serious. The increase of S will enhance the nonlinear change of explosion disaster, and the change law of explosion overpressure is completely opposite to that of high-speed airflow and high-temperature flame. With the increase of Pstat, the coupling effect of air intake pipe and dust collector is strengthened, which further aggravates the spread of explosion disaster. The change of CD has both promoting and restraining effects on the spread of explosion disaster. The maximum overpressure (P), maximum wind speed (V), maximum flame speed (Fs) and maximum flame distance (Fd) in the explosion venting zone are 0.022 MPa, 494.5 m/s, 112.9 m/s and 10.9 m, respectively, and the venting safety distance is more than 11 m. In addition, the degree of impact on explosion disaster is in the following order: Pstat > A > CD. This research can provide a reference basis for the effective prevention and control of the composite disaster external the explosion vent induced by dust explosion inside the dust collector.

Research on the cooling mechanism of low-temperature liquid jet mixing in high-temperature and high-speed airflow

The multi-stage water spray cooling system of the space launch site involves a complex gas–liquid two-phase mixed cooling problem in the process of spraying water onto the rocket engine gas jet. To investigate the complex multiphase flow field of the interaction between the airflow and liquid water jet, the Mixture multiphase flow model is adopted, which is coupled with the vaporization equation and component transport model of liquid water. The computational fluid dynamics method is used to numerically analyze the mixing and cooling mechanism of low-temperature liquid jet in high-temperature and high-speed gas flow. The results show that mixing low-temperature liquid jets in high-temperature and high-speed airflow can cause the exchange of momentum and energy, resulting in pressure loss and temperature reduction in the gas phase flow field. Due to the acceleration of transverse airflow, the diffusion flow range of the jet is significantly increased, and violent vaporization occurs, which further consume a large amount of airflow energy. The mixing cooling effect of transverse airflow and liquid water jet is directly related to the mass flow rate ratio of the jet to airflow. In addition, directly designing liquid water jet orifices on the solid wall of the guiding device can achieve the effect of improving the gas flow field environment. This conclusion can provide theoretical reference for the thermal protection design of ground launch devices in space launch site.

ANALISIS ALIRAN UDARA PADA PIPA KOMPOR BURNER

A used oil burner stove is a type of stove that uses used oil as fuel to produce fire and heat which is used in the cooking process. This concept is more commonly found in areas with limited access to conventional energy sources such as electricity or gas. Apart from that, there is a blower which has an important function to maintain sufficient and high-speed air flow towards the combustion axis, thereby helping to increase oil burning efficiency. This test was carried out using Solidworks software with the CFD or Computational Fluid Dynamic feature which has the function of analyzing fluid flow on an object by entering the required parameters. In this paper, a burner stove pipe with an initial cross-sectional area of 2" inches and a final cross-sectional area of 1/2" inches is used where an initial velocity input is given with independent variables of 2 m/s, 4 m/s and 6 m/s and the output is obtained or The results on the stove burner pipe were 17.9 m/s, 37.3 m/s and 54.6 m/s.

Effects of airflow direction on the thermal-hydraulic performance of louvered fin-common flow up vortex generator

To improve the thermal-hydraulic performance of the louvered fin and flat tube heat exchangers (LFHEs), this paper innovatively proposes the louvered fin-common flow up vortex generator (LF-CFUVG). Then, numerical simulations are conducted to study the effects of airflow direction γ on the thermal-hydraulic performance of the LF-CFUVG. The corresponding results indicate that the flow resistance of the LF-CFUVG is always greater than the Baseline (the LFHE without CFUVGs), as the CFUVGs reduce the minimum free flow area while forming low-speed wake zones behind them. The heat transfer capacity of the LF-CFUVG exceeds the Baseline as well, this is attributed to the longitudinal vortices induced by the CFUVGs, which is helpful to homogenize the temperature field and transport the high-speed and low-temperature airflow. And the thermal-hydraulic performance of LF-CFUVG also outperforms the Baseline. In comparison to the working condition of γ is 0°, the pressure drop Δp for the LF-CFUVG declines with increase of γ from 0° to 30°, thus a larger angle helps to reduce flow resistance. However, the heat transfer coefficients hLF and performance evaluation criteria (PEC) of the LF-CFUVG deteriorate with the increasing γ, so a smaller angle is recommended to obtain an intenser heat transfer and better PEC.