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The finite element method was taken to simulate the heat transfer characteristics and capacity of the online cooling equipment of a 3500 mm medium thickness plate production line. The cooling field on the steel plate surface could be divided into the impact zone and the wall jet zone after cooling water was sprayed on the surface of the steel plate. The impact zone had an intense heat transfer capacity because of the static pressure and the high radial velocity of cooling water. The maximum heat transfer coefficient (HTC) in the impact zone of spray and laminar cooling equipment could reach 20,334 and 10,096 W/(m2 °C), respectively. In the wall jet zone, the radial velocity of cooling water was the main factor affecting the heat transfer capacity. With the decrease in velocity, the HTC decreased gradually. There is a linear relationship between the average HTC and the water flow. The average HTCs of spray and laminar cooling equipment in the common range of water flow were 5904–7255 W/(m2 °C) and 3012–3369 W/(m2 °C), respectively. The HTCs were verified in the 3500 mm medium thickness plate production line. [ABSTRACT FROM AUTHOR]

Electrospray deposition (ESD) is a technique with emerging relevance for applications requiring micro‐/nano‐scaled coatings. Self‐limiting electrospray deposition (SLED) is a regime of ESD where upon satisfying the criteria for self‐limiting behavior, the charge buildup of the material will eventually begin to repel itself until an asymptotic thickness is achieved, based primarily on the properties of the spray solution and deposited material. This work focuses on controlling the coating thickness further to achieve sub‐micron thicknesses. By applying a voltage bias of the same polarity of the spray onto the target substrate while providing a secondary grounded surface, the thickness of a payload can be manipulated for thinner and more precise thicknesses. The magnitude of the voltage bias is varied to show the effect of voltage bias on thickness, and 2‐D and 3‐D structures are used to demonstrate the generality of this technique for complex substrates. The results show how SLED can be included as a potential alternative for conformal coatings deposited at ambient conditions at the sub‐micron scale. [ABSTRACT FROM AUTHOR]

Industrial growth has led to increased electronic component integration, resulting in higher working temperatures and technological failures. Cryogen spray cooling (CSC) could reach cryogenic temperatures with fast-responding, but its heat transfer limitation due to liquid film deposition is potentially challenging. In this study, CSC cooling is incorporated with either a cold air jet (CAJ) or a sweeping jet (SWJ) to enhance heat and fluid flow. A K-type thermocouple is used for measuring the surface temperature, while the improved Duhamel theorem is used to estimate the heat flux. The spray and film intensities are recorded through the Mie-scattering methodology via high-speed camera. The results demonstrated that the CAJ/SWJ exhibited a significant reduction in surface temperature and film intensity, enhanced heat dissipation and spray efficiency compared to CSC cooling. More precisely, it demonstrated a 26%–36% heat transfer coefficient improvement, along with a 52% increase in the corresponding time of the critical heat flux. Meanwhile, the CAJ/SWJ intensifies heat transfer during film and transition boiling, inspired by the fast liquid film evaporations. In contrast, the SWJ is much preferred due to its wider and stable coolant coverage throughout film evaporation, as seen by its greater heat transfer coefficient. The combined results demonstrated the need to promptly eliminate the deposited film, as it holds the potential to serve as a pivotal resolution for the advancement of thermal management technology. [ABSTRACT FROM AUTHOR]

Regeneratively cooled scramjets are successfully used as propulsion devices in hypersonic vehicles. During operation, scramjets experience acceleration. This special process causes a dynamic flow process, and heat transfer in the cooling channel commonly occurs, which may cause hazards and control difficulties for scramjets. A dynamic numerical model with a modified heat transfer coefficient calculation method was established to study the transient flow and heat transfer processes in a cooling channel. The dynamic characteristics of the flow and heat transfer under different conditions were calculated and are discussed, including the changes in the inlet fuel mass flow, heat flux, and pressure working conditions. The results indicate that the stable time of the cooling channel outlet fuel temperature is related to the rate of change in the inlet mass flow and heat flux. The stable time of the outlet fuel temperature under decreasing heat flux working conditions was approximately 12.5 s. These results summarize the dynamic flow and heat transfer characteristics, which are significant for designing cooling channels in scramjets. [ABSTRACT FROM AUTHOR]

Light Emitting Diodes (LEDs) is one of the newest ways to light up outdoor areas such as streets, stadiums, airports, military bases, harbors, and high mast towers. The main reason for the high focus is power consumption with better brightness. Even though LEDs have so many benefits, researchers should focus on better managing temperatures as the main reason behind the failure of LEDs is overheating. In this article, modern research trends like using heat pipes filled with nanofluids, ionic winds, spray cooling, use of fins, refrigerants, and oil cooling are focused on and discussed concerning LEDs, solar stills, electric vehicle batteries, and different heat transfer devices to develop a new way to handle the heat from higher-wattage LEDs. There is a research thrust in the field of more than one nanoparticle in the base fluid, and its proportions are not analyzed during LEDs cooling study using a heat pipe. It is necessary to control the heat using a more effective technique. Heat pipe with nanofluid is a more efficient, compact, and cost-effective cooling device o reduce LED failure due to higher heat flux. Hence, it is promising to use nanofluid-filled heat pipes to serve the purpose of the life span enhancement of LEDs. [ABSTRACT FROM AUTHOR]

The continuously increasing energy density of electric motors to match the performance of electric vehicles with internal-combustion-engine vehicles demands an advanced cooling strategy. Direct dripping/spray cooling is one of such potential cooling strategies to replace the conventional cooling method for achieving the desired thermal management of next-generation electric motors. In the present work, the heat transfer characteristics of an electric motor with oil-dripping cooling were experimentally investigated considering overload operating conditions. An experimental set-up comprising a 15 kW electric motor and an oil-dripping cooling system was developed. The experimental data were used to evaluate the maximum temperature, heat transfer coefficient and power consumption under the influence of a dripping hole diameter (2 mm, 3 mm, 4 mm), oil flow rate (8 LPM, 12 LPM, 16 LPM) and overload operating power (8.28 kW, 12.05 kW, 14.21 kW). The symmetrical oil distribution over the electric motor and the superior heat transfer from the electric motor to the oil was achieved when the oil-dripping cooling system was designed with the combination of a 4 mm dripping hole diameter and a 12 LPM oil flow rate. The combination of the 4 mm dripping hole diameter and 12 LPM oil flow rate showed the lowest maximum temperatures of 31.9 °C and 46.3 °C for electric motor under overload operating powers of 8.28 kW and 14.21 kW, respectively. In addition, the highest heat transfer coefficient of 7528.61 W/m2-K and lowest power consumption of 18.07 W were achieved for the oil-dripping cooling system with the combination of a 4 mm dripping hole diameter and 12 LPM oil flow rate. The best combination of the operating parameters is proposed for developing the oil-dripping cooling system that enables superior heat transfer characteristics and, thus, an enhanced thermal management of electric motors under overload conditions. [ABSTRACT FROM AUTHOR]

Spray cooling is an effective heat dissipation technology and is widely used in the heat dissipation of encapsulated structures, but most of the research has only focused on the heat transfer performance itself and has lacked the analysis of surface stress and deformation. In this paper, a thermal stress coupling model was established under spray conditions, and the influence of spray parameters such as the spray height, spray flow, and nozzle inclination on heat transfer, surface stress, and deformation were studied. The result indicated that the lower the surface temperature, the smaller the stress and deformation. What is more, there was an optimal spray height (15 mm) to achieve the best heat transfer, and the surface stress and deformation were also minimal at the same time which the values were 28.97 MPa and 4.24 × 10−3 mm, respectively. The larger the spray flow rate, the better the heat transfer effect and the smaller the surface stress and deformation. When the spray flow rate was 24.480 L/h, the minimum values of surface stress and deformation were 25.42 MPa and 3.89 × 10−3 mm, respectively. The uniformity of surface stress distribution could be effectively improved with the increase in flow rate. Compared to 10 and 15 degree nozzle inclination, when the nozzle was perpendicular to the cooling surface, the surface stress and deformation were minimal. [ABSTRACT FROM AUTHOR]

BACKGROUND Patients frequently seek laser treatment for vascular conditions. More recently, a novel 532 and 1,064nm laser was developed to offer greater flexibility. OBJECTIVE A prospective clinical trial evaluated the safety and efficacy of a novel, variable-sequenced, long-pulsed, 532 and 1,064 nm laser with cryogen spray cooling (DermaV, Lutronic, South Korea). MATERIALS AND METHODS Subjects with vascular conditions were enrolled for laser treatments. Clinical evaluations and optical coherence tomography (OCT) imaging were performed. RESULTS Thirteen subjects were enrolled. The mean age was 51.3 years, and 92.3% were women. Fitzpatrick skin types I--IV were included. Treatment indications included broken blood vessels, rosacea, port-wine birthmark, and spider angioma. For physician investigator grading, all subjects were graded as improved at both 30-day and 90-day follow-up. Blinded photographic review by 3 independent, blinded physicians had a mean of 89.7% of cases selected correctly with at least 2 of 3 in agreement for 100.0% of cases. Optical coherence tomography imaging showed significant reductions in vessel density (p = .018) and diameter (p = .003) of the superficial vascular plexus. No serious adverse events occurred. CONCLUSION A novel, variable-sequenced, long-pulsed, 532 and 1,064 nm laser with cryogen spray cooling can safely and effectively improve vascular conditions and lesions as determined by both clinical and OCT evaluation. [ABSTRACT FROM AUTHOR]

Recently, the thermal management of power electronic converters has gained significant attention due to the continuous trend of developing very compact power electronic converters with high power density. With the evolution of power semiconductor devices, high operating temperatures and large thermal cycles have become possible, necessitating a significant improvement in thermal system designs. Researchers have made significant efforts to develop effective thermal management systems to improve the reliability and lifetime of power electronic converters. This article intends to present a thorough review of thermal management systems employed in power electronics cooling. The applied thermal management techniques have been reviewed from the perspective of electrical parameter regulation and heat dissipation control. Regulation of electrical parameters involves active thermal control, which is a method for controlling junction temperature and thermal cycling of power semiconductor devices. The active thermal control implementation processes reviewed in this article consist of increasing overload capacity, manipulating switching and conduction losses, employing modified modulation processes, balancing thermal stress at the converter level, and controlling thermal stress at the system level. Control of heat dissipation can be achieved through direct and indirect cooling of power electronic converters with air or liquid as the coolant. The effectiveness and implementation methods of these cooling techniques, such as channel cooling, phase change material-based cooling, immersion cooling, jet impingement and spray cooling, are reviewed in this paper. Moreover, performance-enhancing ideas and challenges for these techniques are discussed. The primary objective of this review paper is to bridge the existing gap in the literature by offering a comprehensive comparison of commonly employed thermal management techniques.

Cis-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(Z)) has emerged as an exceptionally promising low-global-warming-potential (GWP) refrigerant, ideal for spray cooling systems in the thermal management of electronic components. Research on the evaporation characteristics of an individual isolated cryogen droplet excludes uncertainties caused by droplet collisions and fusion, thereby laying the foundation for spray cooling. In this paper, a theoretical model for single R1336mzz (Z) droplet evaporation considering the effect of natural convection in a high pressure and temperature environment is proposed. The newly proposed model is validated by comparing the predicted results of the R1336mzz(Z) droplet evaporation with experimental data. Then, the effects of environmental temperature (323–523 K) and pressure (1–20 bar) on the R1336mzz(Z) droplet evaporation are investigated. The results reveal that the effect of increasing the ambient pressure on the droplet lifetime of R1336mzz(Z) undergoes a transition from deceleration to acceleration. Elevated temperature can promote droplet evaporation; however, the promoting effect of increasing the ambient temperature on droplet evaporation will be weakened in high-pressure cases. Increasing the ambient pressure and temperature both can enhance the heat transfer from the environment to the droplet through natural convection, while increasing the pressure greatly inhibits the molecular diffusion during droplet evaporation. Thus, the total evaporation rate depends on the competing effects of these two factors. In addition, the trend of the droplet temperature variation could differ based on droplet initial temperatures, ambient temperatures, and pressures. An increase in the ambient temperature or pressure corresponds to an increase in the droplet equilibrium temperature (Tequ). However, Tequ is almost independent of the droplet initial size and temperature. [ABSTRACT FROM AUTHOR]

Laser dermatology has become a convenient technique for medical treatment. However, the epidermal temperature could be increased, leading to intolerable side effects. Cryogen spray cooling (CSC) is implemented to decrease epidermal damage, but the current CSC could increase cryogen wastage. In this study, the CSC is coupled with a cold air jet (CAJ) and is further subjected to intermittent strategy (ICSC) to mitigate film deposition, enhance heat transfer, and save cryogen consumption, through CAJ-to-spray interaction. The surface temperature is measured by a thin film type-T thermocouple, while the heat transfer is estimated by enhanced Duhamel theorem. The film intensity is captured by a digital single-lens reflex camera through the scattering-illumination technique. The results affirmed the benefits of using ICSC/ICSC-CAJ for laser dermatology. It demonstrated lower surface temperature, film intensity, and film resistance as well as higher convection and efficiency compared with CSC. ICSC-CAJ showed the lowest minimum temperature (1.8%–4.9% decrement) and film resistance (3.8%–17.5% decrement), the highest average convective coefficient (84%–92% increment) and efficiency (7%–9% increment) compared with ICSC. Lower frequency and moderate duties would be preferable for ICSC, while higher frequency and lower duties would be preferable for ICSC-CAJ. The efficiency increased with the saving (110% increment), which insights into our understanding of alternative enhancement toward cryogen saving strategy. [ABSTRACT FROM AUTHOR]

The behaviors of droplets impinging on superhydrophobic surfaces have received much attention from industry and academia due to potential applications such as anti-icing, spray cooling, and self-cleaning. Previous studies have shown that the superhydrophobic surfaces can significantly reduce contact time and thus effectively suppress surface icing and condensation phenomena. In this paper, the bouncing behaviors of droplets on superhydrophobic surfaces decorated with cross ridges were investigated using numerical simulations and theoretical analysis. The effect of cross-ridge structures with different pinch angles and droplets with different Weber numbers on droplet bouncing behaviors was investigated using the volume-of-fluid method. The results showed that the solid–liquid contact time was shortest when the angle between the two ridges was 75°. Compared to droplet bouncing on a smooth surface, the contact time was reduced by up to 30% for complete bouncing behaviors and up to 68% for broken bouncing behaviors. As the angle decreased, the ratio of spreading areas between child droplet sizes increased exponentially. The momentum of the smaller child droplet decreased until it was no longer generated. A theoretical analysis based on energy conservation was also performed. A theoretical equation was proposed to predict the maximum spreading coefficient. The maximum error was less than 10% for the experimental and numerical results compared to the predicted results. [ABSTRACT FROM AUTHOR]

In the present study, two nanofluids namely Multi-walled carbon nanotubes and Titanium dioxide dispersed in distilled water, have been used with three different concentrations; 0.1%, 0.2%, and 0.3% by volume, to investigate heat transfer enhancement in spray cooling applications. A square copper specimen of 10 mm2 has been spray cooled with a volumetric flux of 2.5 cm3/cm2s using a 0.4 mm diameter pressure nozzle. The results revealed that the average heat transfer coefficient and corresponding critical heat flux enhanced significantly at 0.2 vol% for both nanofluids in contrast to distilled water. The results showed an improvement of 21.9% and 26.3% in heat transfer coefficient for Multi-walled carbon nanotubes and Titanium dioxide nanofluid, respectively. The effect of hybrid nanofluid in various concentrations has also been investigated on heat transfer performance. The results obtained showed a maximum value of 425 W/cm2 for critical heat flux and 4.42 W/cm2K for heat transfer coefficient, with a heat transfer coefficient improvement of nearly 40.31% in comparison to distilled water. This results in an enhancement ratio of 1.6 for critical heat flux and 1.4 for heat transfer coefficient. In contrast to single nanoparticle nanofluid, the hybrid nanofluid indicated a moderate improvement in heat transfer coefficient of 11.7% and 7.8% for Multi-walled carbon nanotube and Titanium dioxide nanofluids, respectively. It has been observed that heat transfer performance was first enhanced and then declined as the volume fraction increased from 0.1% to 0.3% for all the nanofluids. [ABSTRACT FROM AUTHOR]

The present study emphasizes the spray-cooling enhancement of a copper heater block of 10 mm2 cross-sectional area with binary mixed surfactant based fluid and hybrid nanofluid using a pressure swirl nozzle with an orifice size of 0.51 mm. The experiments have been carried out at two distinct fluid input temperatures of 27 °C and 42 °C, with a volumetric flux of 3.50 cm3/cm2s. Polyvinyl pyrrolidone (polymer surfactant), Sodium dodecyl sulfate (an anionic surfactant), Tween-20 (a nonionic surfactant) have been used as binary mixed surfactant systems in distilled water. The best performance has been obtained with SDS:Tween-20, which resulted in a maximum heat flux of 264 W/cm2 and a heat transfer coefficient of 3.59 W/cm2K. When compared to distilled water, the heat transfer coefficient increased by 32.2%, but only by 25.2% and 18.1% with PVP:Tween-20 and SDS:PVP surfactant solutions. Further, the effect of a hybrid nanofluid, which is a colloidal mixture of Titanium dioxide (TiO2) and MWCNTs (multi-walled carbon nanotubes) in distilled water, has been studied to better understand spray cooling heat transfer enhancement. Heat transfer was first enhanced by the hybrid nanofluid and then decreased as the volume concentration was increased from 0.1% to 0.3%. A maximum heat flux of 234 W/cm2 and a heat transfer coefficient of 3.15 W/cm2K has been achieved, with a heat transfer coefficient improvement of nearly 27.3% compared to distilled water. However, the mixed surfactant system outperformed, giving nearly 12.8% improvement in heat flux values. It has been observed that low surface tension resulted in high heat transfer rates. Furthermore, the effect of 15 °C subcooling on heat transfer performance has been investigated. A new correlation to find Nusselt number is proposed in terms of Reynolds number, Weber number and Prandtl number with a mean absolute error of 7.16%. [ABSTRACT FROM AUTHOR]

To investigate the spray cooling characteristics and the impact of spray parameters such as chamber pressure, spray height, and spray tilt angle on heat transfer efficiency, a mathematical model based on the Eulerian–Lagrangian frame was established for an R410A closed-loop spray cooling system. The results revealed that the spray pattern is conical, with the center velocity significantly higher than the edge velocity. The temperature distribution of the cooling surface and liquid film height both exhibit a "W" shape, and the surface temperature is lower where the liquid film is thin. There is an optimal liquid film height of approximately 5 μm, at which the cooling surface temperature is the lowest. The surface temperature increases with an increase in the spray chamber pressure. Considering average cooling surface temperature, the optimal tilt angle is 40° with an average surface temperature of 330.1 K. When considering wall temperature and wall heat transfer coefficient uniformity, however, the optimal tilt angle is 10°, leading to the average surface temperature of 332.6 K. When increasing the optimal spray height to 70 mm, the average surface temperature is 313.4 K. [ABSTRACT FROM AUTHOR]

The efficiency of replacing traditional quenching in a bath by spray quenching to manufacture grinding balls ∅120 mm made of 70SiMnCr steel to reduce stresses and control the phase composition is investigated. A process of forging grinding balls with the use of water spray cooling is suggested, which ensures bainite transformation under isothermal conditions and formation of the specified structure. The W70A45W20 process, implemented at 200°C for 4.5 h, yields balls with a final volume hardness of 56 HRC and a toughness of 73 J. After this mode of heat treatment, the steel balls have a high wear resistance, and the main mechanism of their surface wear is plastic deformation and micro-cutting. [ABSTRACT FROM AUTHOR]

• Dry ice particles spray cooling for IGBT of high-speed train is proposed. • The pin-fin heat sink and the straight-fin heat sink are developed. • The cooling characteristics of dry ice particles spray are simulated and tested. • The temperatures of heat transfer substrate of pin fin heat sink are obtained. Aiming at the high efficiency cooling problem of IGBT(Insulated Gate Bipolar Transistor) module of traction converter for high-speed Train, a method of spray cooling with natural dry ice particles was proposed. The heat sinks with pin-fin and straight-fin structure were designed, and the heat sinks with optimum structure size selected by simulation were developed, and the heat sinks were provided with visual shells, as well as single outlet, double outlet and four outlet of the three different ways of outlet. The gas-solid two-phase flow, heat and mass transfer characteristics of dry ice particles in the heat sinks were studied by means of simulation and experiment. By comparison, it is found that the flow and heat transfer in the pin-fin heat sink have a good cooperation, and it is most suitable for the IGBT module with spray cooling of dry ice particles, which can reduce the temperature of IGBT from 70 ℃ to 55 ℃ in 75 s, compared with the fin-free heat sink, the heat transfer performance is improved by 12 %, and the double-outlet pin-fin heat sink has the best effect, the temperature difference of the heat transfer substrate is 19.8 ℃, and the average temperature of the heat transfer substrate is only 22.5 ℃ compared with that of the open type, which is 27.3 ℃ lower. Double outlet dry ice particles spray pin-fin heat sink is an efficient heat sink, thermal resistance is only 0.066 K/W, it can meet the current practical application of high-speed train cooling needs, solve the problem of heat dissipation of IGBT module for high-speed train, it lays a foundation for the development of dry ice particles spray heat sink. [ABSTRACT FROM AUTHOR]

This study focuses on the interactions between cryogen spray cooling (CSC) and cold air jet (CAJ), as well as the heat transfer performance upon CAJ-CSC impingement assisted for laser dermatology. CAJ is found to collapse downstream spray on the windward side, enhancing fluctuations of R1234yf spray width. Standard deviation (SD) distribution identifies that fluctuations at nozzle exit are attributed to ambient-to-spray interactions, which is also confirmed by the proper orthogonal decomposition (POD) analysis. The third POD mode highlights jet-to-spray interactions on the windward side of spray, yielding an enhanced instability by 1.72 times when CAJ flow rate (Q) increases from 4 to 8 m3/h. The closer location to the spray center on the same radial side corresponds to a faster thermal response and a lower temperature drop (ΔT). ΔT on the windward side decreases due to the considerable CAJ-induced droplet swarm drift. The heat transfer degrades on the leeward side due to the thermal gas boundary layer originating from the inclined CAJ sweep. Nevertheless, the CAJ with a small flow rate (4 m3/h) enhances the heat transfer at spray center, yielding a minimum surface temperature of −32.3 °C. Comparative investigation indicates R134a has superior cooling performance but more significant instabilities inside spray plume. R1234yf serves a relatively stable sub-cooling region within a radial distance of ±1 mm from spray center characterized by low spray fluctuations and high temperature drops at Q = 4 m3/h. Substitution of R1234yf for R134a still needs heat transfer enhancement for clinical considerations. [ABSTRACT FROM AUTHOR]

Isothermal compression is the state‐of‐the‐art in compressed air energy storage (CAES) technology. The study of cyclic pressurization unit in isothermal CAES is carried out in this paper. The unit can continuously compress air utilizing double vessels operating alternately. In each vessel, the large heat capacity of water and spray cooling is applied to establish a conducive environment for the air achieving the effect of efficient near‐isothermal compression. The operating mode of the cyclic pressurization unit is divided into sliding‐pressure operation and constant‐pressure operation according to the pressure of its outlet. By adopting the characteristic curves of pump, the dynamic model is built for the unit in this paper. Further, the differences between the cyclic pressurization unit in isentropic process and in variable‐speed process are quantified and compared in four different cases. In isentropic process, the energy‐saving ratio and exergy efficiency of the unit are expected to reach 20.4% and 95.0%, respectively. In variable‐speed process, the energy‐saving ratio and efficiency of the unit can achieve 7.3% and 73.4%, respectively. This gap is mainly determined by the off‐design performance of the pump. Moreover, the vessel volume should be no less than 3 m3 and 5 m3 when there is spraying and when there is no spraying. Furthermore, spraying favors the improvement of the worsened compression performance caused by the change of design parameters. The energy‐saving ratio can be improved via spraying by 1.3% to 11.0% and 1.8% to 25.6% in the isentropic and variable‐speed processes, respectively. Meanwhile, the exergy efficiency can be increased by 1.5% to 9.4% in the isentropic process and 1.4% to 8.4% in the variable‐speed by spraying. [ABSTRACT FROM AUTHOR]

• Twelve spray cases and four media were investigated to pre-cool a MDDCT. • Case studies of 12.5 m-high towers are carried out to compare tower performance. • Spray case 4 and 300 mm CELdek7060 are found with good cooling performance. • The MDDCT's heat rejection rate can be improved by up to 67.11 % though pre-cooling. • Nozzle spray is recommended to pre-cool the MDDCT for performance improvement. Evaporative pre-cooling can improve the cooling performance of a mechanical draft dry cooling tower (MDDCT) during hot periods. MATLAB iterative programs were developed to simulate a MDDCT, MDDCTs pre-cooled with nozzle spray and wet medium, a mechanical draft wet cooling tower (MDWCT). Cooling performance and water evaporation rate of the four cooling towers were studied based on the meteorological data of Hami, Xinjiang in 2020. Results show that: (1) twelve spray cases were studied and spray case 4 performs best to improve MDDCT's heat rejection rate from 2.72 MW to 5.77 MW with 112.13 % improvement; (2) four media were studied including CELdek7060, PVC1200, Trickle125 and Trickle100, and 300 mm CELdek7060 performs best to improve MDDCT's heat rejection rate from 2.72 MW to 4.66 MW with 71.32 % improvement; (3) case studies find that MDDCT pre-cooled with nozzle spray can improve its heat rejection rate all year round while pre-cooled with wet medium is only helpful from April to September; in the hottest month of July, the heat rejection rates of MDDCTs pre-cooled with nozzle spray and wet medium are improved by 67.11 % and 45.30 %, respectively; the water evaporation rate per MW of MDDCT pre-cooled with nozzle spray (i.e., 0.2197 (kg·s−1)·MW−1) is closed to the pre-cooling with wet medium (i.e., 0.2203 (kg·s−1)·MW−1), which is about 59.27 % of the MDWCT (i.e., 0.3707 (kg· s−1)·MW−1). Considering both cooling and water evaporation performances, it is recommended to use nozzle spray to pre-cool the MDDCT for performance improvement during periods of high temperature. [ABSTRACT FROM AUTHOR]

Olefins are crucial building blocks for petrochemical industry, serving as raw materials for the production of various products such as plastics, synthetic fibers, detergents, solvents, and other chemicals. In FCC, heavy petroleum feedstocks are injected into a catalytic cracking unit, where they are mixed with a catalyst. The catalyst aids in breaking down the large hydrocarbon molecules into smaller fragments, including olefins like Propylene and Ethylene. These polymerization reactions occur at high temperatures. They demand that heat removal occurs as quickly as possible in order to control the reactor temperature and to avoid "hot spots" in the Regenerator or localized oxidation reactions (and to avoid creep rupture of the regenerator steel cladding). The cooling of the regenerator cladding surface can be achieved by impinging water droplets (spray), ejected from a spray nozzle. Spray cooling can provide uniform cooling and handle high heat fluxes in both a single phase and two phases. This research provides a thermal hydraulic design of regenerator spray cooling systems. In the framework of this research, Fire Dynamics Simulator (FDS) software was applied in order to simulate the temperature field and the water vapor mass fraction. A COMSOL Multiphysics finite element code was used in order to calculate the temperature field inside the regenerator cladding. The calculated surface temperatures and heat transfer convective coefficient, obtained using FDS software, were validated successfully against COMSOL numerical results and previous results in the literature. The numerical simulations were carried out for two cases. The first case was carried out at a distance of 0.5 m, and the second case was carried out at a distance of 0.2 m. A grid sensitivity study was carried out on the FDS model. Numerical integrations were carried out over time in order to calculate the average temperatures. The difference between these four average temperatures, calculated by applying different grids, is less than 7.4%. The calculated surface temperatures and heat transfer convective coefficient were validated successfully against COMSOL numerical results and previous research. It was shown that the calculated temperatures decrease in the second case. The water spray system managed to cool the steel wall more effectively as the water spray system approaches the steel cladding. [ABSTRACT FROM AUTHOR]

In electric vehicles (EVs), battery thermal management system (BTMS) plays an essential role in keeping the battery working within the optimal operating temperature range and preventing thermal runaway. Many cooling mediums have been conducted into BTMS to transfer, absorb, or dissipate the heat generated from the batteries. Thermal conductivity, heat transfer coefficient, cooling performance, cost, poison, environment, system size, and equipment needed are critical factors in choosing the ideal heat transfer coolant for the BTMS. This review paper concentrates on the novel and echo-friendly heat transfer coolant mediums investigated for BTMS and has been rarely documented in the literature. In the scope of this review, traditional BTMS coolant mediums including air, water, phase change material (PCM), and hybrid coolants are considered, and their optimization techniques have been discussed. Additionally, a comprehensive review is provided on novel techniques and novel materials that have the possibility of enhancing the thermal performance of the battery pack on the one hand, as well as the potential of integration into BTMS with higher safety and less (weight, volume, cost, toxicity, and power consumption) compared to the classical heat transfer coolant mediums on the other hand. Finally, evaporative, mist, spray, and nanofluid techniques are found as promising cooling techniques. In terms of environmental, availability, and non-toxicity aspect, jute has the highest possibility of being integrated into BTMS. This study will give the opportunity to see the latest research investigating novel cooling mediums, which will lead to further improvement for BTMS.

The spray cooling is investigated for a high-temperature steel plate using varying temperature coolant for different nozzle-plate orientations. Before experimentation with very-high mass-flux spray, droplet-train impact assessment indicates liquid film breakup intensification down the inclined plane. The heat transfer analysis suggests a significant cooling performance change with an inclination change at high-temperature coolant. For 50°C coolant usage in horizontal-case, cooling rate, average surface heat flux, critical heat flux, and average heat transfer coefficient are 161°C/s, 2.20 MW/m2, 2.62 MW/m2, and 3.28 kW/m2K, respectively. The 40°C coolant has a low-performance factor, while 50°C has high cooling performance. [ABSTRACT FROM AUTHOR]

Infiltration through spray-pyrolysis deposition is a one-step and effective method for enhancing the electrode performance of solid oxide fuel cells (SOFCs) at intermediate temperatures. Among various infiltrated electrodes, Pr 6 O 11 has shown promising electrocatalytic properties for oxygen reduction reaction (ORR), despite its relatively low electrical conductivity. This study focuses on obtaining Pr 6 O 11 -infiltrated cathodes using spray-pyrolysis deposition, with different porous backbone layers that exhibit electronic and/or ionic conductivity: La 0.8 Sr 0.2 MnO 3-δ (LSM), Ce 0.9 Gd 0.1 O 1.95 (CGO), and LSM-CGO composite. The electrochemical properties and the subprocesses involved in the ORR are investigated in symmetrical cells. It is observed that the polarization resistance (R p) decreases when the backbone layer exhibits high ionic conductivity. At 650 °C, the R p values are 0.03, 0.06 and 0.1 Ω cm2 for CGO, LSM-CGO and LSM backbones, respectively. The dependence of R p contributions with pO 2 reveals that the same electrochemical processes are involved regardless of the backbone composition, confirming a less resistive oxide-ion transport from the TPB into the electrolyte with the CGO backbone. In contrast, the CGO backbone exhibits higher series resistance (R s) (44.5 Ω cm), attributed to an increased contribution of ohmic losses compared to the LSM backbone (39.8 Ω cm). This study provides valuable insights into the performance and optimization of Pr 6 O 11 -infiltrated cathodes with different backbone compositions for their implementation in SOFCs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The investigation of the underlying physical processes involved in the impact of droplets has various practical applications in engineering and science. In this research, the spreading velocities within droplet impingement on a sapphire glass were investigated for a wide range of Weber numbers using particle image velocimetry (PIV), which involves tracking the movement of polymeric fluorescent particles (6 µm) within the droplet. The experiments were carried out at room temperature, and the droplets had impact velocities ranging from 0.41 to 2.37 m/s, which corresponded to Weber numbers of 5–183. The results showed that the radial velocity was generally linear over a wide range of spreading radius but the velocity at the exterior radial positions became nonlinear over time due to the influence of capillary and viscous forces. This nonlinearity was more pronounced for lower Weber numbers because the viscosity effects in the droplet were more significant compared to the inertia forces. As the Weber number decreases, the spreading and receding of the droplets are completed faster, leading to different trends in the radial velocity profiles. [ABSTRACT FROM AUTHOR]

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In this study, the wear resistance of micro-textured tools was explored. Micro-textured tools with different morphologies were used in turning GH4169 during spray cooling. The tool wear on the rake face of the different micro-texture morphologies was investigated through simulation and experiments. Firstly, based on the existing research on bionics, micro-textures with five different morphologies were designed on the rake face of carbide tools. A simulation model of cutting GH4169 during spray cooling was established, and the tools with designed micro-textures were used in it. The influence of the different micro-texture morphologies on the tool wear was analyzed. Secondly, the designed micro-textured tools with five different morphologies were produced using a femtosecond laser. Cutting experiments were conducted using the micro-textured tools during spray cooling. The wear area of the rake face was measured based on the infinitesimal method, and the optimal morphology with the best anti-wear ability was obtained. This study provides technical support for the design and development of micro-textured tools with an improved cutting performance, and contribute to the promotion and application of micro-textured tools. [ABSTRACT FROM AUTHOR]

The article describes a technique for setting the boundary conditions in the secondary cooling zone, taking into account the technological features of the continuous-casting machine construction and experimental data on the location and characteristics of the nozzles. This approach makes it possible to consider the uneven distribution of the water-air mixture density along the technological length and the width of the face of the ingot in the mathematical modeling of its formation process. [ABSTRACT FROM AUTHOR]

The processes of interaction of liquid droplets with solid surfaces have become of interest to many researchers. The achievements of world science should be used for the development of technologies for spray cooling, metal hardening, inkjet printing, anti-icing surfaces, fire extinguishing, fuel spraying, etc. Collisions of drops with surfaces significantly affect the conditions and characteristics of heat transfer. One of the main areas of research into the interaction of drops with solid surfaces is the modification of the latter. Changes in the hydrophilic and hydrophobic properties of surfaces give the materials various functional properties—increased heat transfer, resistance to corrosion and biofouling, anti-icing, etc. This review paper describes methods for obtaining hydrophilic and hydrophobic surfaces. The features of the interaction of liquid droplets with such surfaces are considered. The existing and possible applications of modified surfaces are discussed, as well as topical areas of research. [ABSTRACT FROM AUTHOR]

In the realm of photovoltaic-thermal (PVT) systems, optimizing operating temperatures for photovoltaic (PV) panels is a challenge. This study introduces a novel solution: a sprayed water PVT system that simultaneously harnesses energy and electricity. The aim is twofold: generate electricity through PV panels and produce hot water via a flat plate collector, using an innovative cooling mechanism. Water sprayed onto the PV panel's surface flows to a collector for storage. With varied flow rates, optimal panel efficiency occurs at a 45⁰ tilt angle, accompanied by lower collector outlet temperatures at higher flow rates. The collector achieves a peak thermal efficiency of 70.6 %, producing hot water at 84.6 °C. Notably, a significant PV panel efficiency enhancement, up to 16.78 %, especially at 1.56 L/min flow rate, is observed. The cooling technique consistently reduces panel temperatures from 45.08 °C to 34.12 °C. A self-cleaning spray mechanism improves efficiency by 2.53 %, resulting in an overall system efficiency of 83.3 %. This research offers an innovative approach to enhance energy generation and electricity in PVT systems, promising sustainable energy optimization.

Evaporative cooling is an efficient approach for removing heat from nuclear reactors, solar power plants, solar panels, and energy storage devices, such as lithium-ion batteries and fuel cells. Nanotextured surfaces can provide improved evaporative cooling by increasing the total surface area to enhance the heat transfer rate and reducing the temperatures of local hotspots. In this study, we introduced rhombic dodecahedral zeolitic imidazolate framework-8 (ZIF8), a class of metal-organic frameworks, via impregnation to create nanotextured surfaces. The impregnation time was varied to obtain various thicknesses of ZIF8. We found that the increased surface area of ZIF8 improved convection cooling, which considerably reduced the temperature of the heated substrate. Air, mist (buoyant aerosols), and spray (inertial droplets) were independently used as coolants to compare the cooling performance of noncoated (bare) and ZIF8-coated substrates. Compared to the noncoated substrate, the optimal ZIF8 film yielded temperature reductions of Δ T = 13 °C and 10°C for air and spray cooling, respectively. [ABSTRACT FROM AUTHOR]

The analysis of interactions between micro-particles and carrier gas is a critical aspect in the study of micro-particle behavior, particularly in fuel spray and spray cooling. However, optical imaging techniques face inherent limitations that pose challenges to existing testing methods in achieving high capturing capability for micro-particles and a large field of view simultaneously. The current study proposes a Dual-view Wide-field High-precision Particle Sizing Technique that integrates hardware (dual-view lenses) and software (cGAN-ResNet joint algorithm). It aims to achieve accurate measurements of micro-particles in a large field of view. Our innovative approach involves simultaneous capture using dual-view lenses, where the smaller view lens aims to achieve high-resolution images. By employing machine learning techniques, we establish correspondences between droplets within the overlapping region of the two different-resolution images. This allows us to reconstruct the droplet information with high resolution for all droplets within the larger field of view, enabling accurate measurement of droplet characteristics across a wide field. We created synthetic datasets using the microSIG program to emulate real-world scenarios and validate our algorithm's accuracy and generalization. The results indicate that our method outperformed traditional adaptive threshold methods and significantly increased the field of view by several folds. Our algorithm has a key feature of real-time learning, thereby allowing it to be adaptable to datasets other than those used in this study and their derivatives. Our study shows that the fusion of multiple deep learning techniques is promising for accurately reconstructing and rapidly measuring micro-particles with a large field of view. [ABSTRACT FROM AUTHOR]

By altering the thermophysical properties of the coolant in the favourable direction of heat transfer, augmentation is achieved in the case of spray cooling in transition boiling. The above-stated thermophysical properties were varied, and the critical limit of maximum heat transfer was determined. In the current work, using various additives, the above stated is achieved, and the maximum enhancement limit is determined. Initially, dropwise experiments are conducted in a transition boiling temperature regime to determine the heat transfer coefficient variation mechanism. Thereafter, spray cooling experiments were performed. In the current work, three independent variables, which are part of Weber, Reynold and Prandtl numbers, are formed: ρ/µ, ρ/σ and cpµ/k. The basis of selection was to identify only the role of thermophysical properties of the heat transfer coefficient. From the variation in HTC with ρ/σ, it is concluded that HTC shows a decreasing trend in the ρ/σ range of 10.2–14, and then again, HTC increases with the rising value of ρ/σ. Finally, after ρ/σ = 20 s2m−3, the HTC does not change significantly, or it can be said that it reaches the plateau region. To check the suitability of the used coolants in fast quenching operations, the cooling parameters such as AHF, CHF and IHFs are compared. From this, it is concluded that the maximum CHF, AHF and IHF are achieved in the case of benzene (1600 ppm)-added water. The analysis of the developed correlations using various techniques shows that the design expert model produces the minimum error. [ABSTRACT FROM AUTHOR]

Due to the excellent heat transfer performance, spray cooling is widely used for heat removal of high-heat-flux electronic devices. In this study, the influence of spray characteristics on spray cooling heat transfer is tested experimentally, where both water and 4% ethanol-water mixture are used as the working fluid. The Sauter mean diameter and droplet number distributions are measured by the Particle/Droplet Imaging Analysis system, and the fluid volumetric flux distributions are measured by the self-designed Precision Mobile Experiment Bench. The results show that the heat transfer efficiency of the 4% ethanol-water mixture is superior to that of water. Especially, the critical heat flux is about twofold that of water for the Spray A nozzle. For a fixed nozzle, the Sauter mean diameter of the 4% ethanol-water mixture is smaller, while the fluid volumetric flux shows an increase under the same conditions. Small Sauter mean diameter and large fluid volumetric flux can induce more droplets to entrain bubbles. Then the mechanisms of improved spray cooling heat transfer are analyzed based on the spray characteristics measurement results. It is revealed that the Sauter mean diameter and mean fluid volumetric flux exert joint influence on the heat transfer efficiency, and the mean fluid volumetric flux has an obvious effect between different nozzles. Two dimensionless heat flux correlations are proposed for the single-phase and nucleate boiling regimes with mean absolute errors of 15.56% and 14.68%, respectively. Highlights: Sauter mean diameter of 4 vol.% ethanol-water is smaller than water, but the fluid volumetric flux is higher than water. Small Sauter mean diameter and large fluid volumetric flux induce more droplets generating entrained bubbles, which can enhance the heat transfer performance. Fluid volumetric flux is predominant in improving heat transfer performance, especially in the nucleate boiling regime. Spray characteristics have an obvious influence on the critical heat flux. Dimensionless heat flux is correlated with characteristic numbers integrating Sauter mean diameter and fluid volumetric flux. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) are an essential tool for the development of diesel engine aftertreatment systems using selective catalytic reduction (SCR) to reduce nitrous oxides ( NO x ). In urea-based SCR, liquid urea–water solution (UWS) is injected into the hot exhaust gas, where it transforms into gaseous ammonia. This ammonia serves as a reducing agent for NO x . CFD simulations are used to predict the ammonia distribution in the exhaust gas at the catalyst inlet. The goal is to achieve the highest possible uniformity to realize homogeneous NO x reduction across the catalyst cross section. The current work focuses on the interaction of UWS droplets with the hot walls of the exhaust system. This is a crucial part of the preparation of gaseous ammonia from the injected liquid UWS. Following experimental investigations, a new impingement model is described based on the superposition of four basic impingement behaviors, each featuring individual secondary droplet characteristics. The droplet–wall heat transfer, depending on surface temperature and impingement behavior, is also calculated using a newly parameterized model. Applying the presented approach, the cooling of a steel plate from intermittent spray impingement is simulated and compared to measurements. The second validation case is the distribution of ammonia at the catalyst inlet of an automotive SCR system. Both applications show good agreement and demonstrate the quality of the new model. [ABSTRACT FROM AUTHOR]

Spray cooling technology offers high levels of uniform heat removal with very low fluid volumes and has found recent application in relatively small-scale use cases. Since it is a complex process, research can enable spray cooling to be applied more widely and at larger scales, such as in HVAC, as a means to operate more efficiently. Weather conditions are one of the main parameters that directly affect the effectiveness of spray cooling. This study investigates the spray cooling performance for temperature and humidity conditions in six Australian cities. ANSYS Fluent (2021 R1) software is applied for the numerical simulation. The numerical model is first validated with the available literature before a numerical simulation is conducted to assess each city throughout the year. These include Adelaide, Brisbane, Darwin, Melbourne, Perth, and Sydney. The spray cooling pattern, temperature, and humidity distribution, as well as the evaporation effect on different regions in Australia, is simulated and analysed based on the CFD technique. The results from this study indicate that weather conditions influence spray cooling for all cities, especially in summer. Along the wind tunnel, the temperature significantly drops at the spray cooling area, while the humidity increases. Due to the effect of spray cooling inside the wind tunnel, the temperature at the outlet is still lower than the inlet for all cases. However, the humidity at the outlet is higher than the inlet for all cases. [ABSTRACT FROM AUTHOR]

A simulation study of droplet impingement on a moving film at different incidence angles in spray cooling application was conducted, and the following results were found: the variation of the angle leads to alternating changes in the neck pressure difference, flow field, and maximum shear which directly causes the transition of the coronal morphology from asymmetric to symmetric and finally back to an asymmetric shape, with corresponding changes in the order of appearance of the left and right jets and secondary droplets. After focusing on temperature distribution and heat flux variation, the temperature distribution is found to be related to horizontal and vertical component velocities of the droplet; the angle affects the heat flux variation at the impact point, and the maximum heat flux decreases with the interaction of the liquid film and droplet, which tends to move downstream. Therefore, the morphological characteristics and temperature distribution are asymmetric when a difference is found between the horizontal velocity of the droplet and the film velocity, and the larger the difference, the more evident the asymmetry is. Therefore, the cooling effect is best, and the shear stress is most significant when the liquid film's and droplets' horizontal velocities are equal. • Variations in the angle of incidence lead to alternating changes in left and right crown height, neck pressure difference, flow field, and heat flux distribution. • Analysis of the shear stress of the liquid film after the impact, and reveals many interesting features. • For spray cooling applications, the effect of nozzle angle on cooling efficiency is clearly explained. • The incidence angle and moving liquid film interact together to achieve optimal cooling compared to single factor conditions. [ABSTRACT FROM AUTHOR]

BACKGROUND: Patients frequently seek treatment for vascular and pigmented lesions. More recently, a novel, variable-sequenced, long-pulsed, 532-nm and 1,064-nm laser with cryogen spray cooling was developed to offer greater flexibility in treatments. OBJECTIVE: A prospective clinical trial evaluated the safety and efficacy of a novel, variable-sequenced, long-pulsed, 532-nm and 1,064-nm laser with cryogen spray cooling (DermaV, Lutronic, South Korea). MATERIALS AND METHODS: Subjects with vascular and/or pigmented lesions were enrolled and underwent laser treatments. RESULTS: Twenty-three subjects were enrolled with vascular lesions (39.1%), pigmented lesions (17.4%), and both (43.5%). Mean age was 53.1 years, and 91.3% were women. Fitzpatrick skin types II–IV were included. All subjects were treated with 532 nm, and 4 were also treated with 1,064 nm. According to 4 blinded physician reviewers, correct before and after photographs were selected in 94.7%, 92.1%, 84.2%, and 76.3% of cases. Overall, 86.8% were responders, meaning that at least 3 of 4 reviewers agreed. For Global Aesthetic Improvement Scale, improvement occurred in 81.6%, 81.6%, 81.6%, and 76.3% of cases. No serious adverse events occurred. Overall, 87.0% of subjects reported being very satisfied or satisfied. CONCLUSION: A novel, variable-sequenced, long-pulsed, 532-nm and 1,064-nm laser with cryogen spray cooling can safely and effectively improve vascular and pigmented lesions. [ABSTRACT FROM AUTHOR]

Spray cooling is a highly effective method of heat removal that has broad practical applications, including use in modern cooling systems designed for microelectronics and microchips. It is known that spray cooling performance is influenced by a huge number of factors. This experimental research is devoted to the study of the influence of a liquid flow rate in the range of 15.1–24.2 cm3/s, heat flux up to 6.4 MW/m2, and nozzle-to-surface distance on the heat transfer rate in non-boiling mode and the distribution of the local temperature of the heat exchange surface during spray cooling. It is shown that the heat transfer coefficient weakly depends on the heat flux for all studied nozzle-to-surface distances. It is demonstrated that the nozzle-to-surface distance has a significant influence on the heat transfer and the temperature distributionon the heating surface during spray cooling in non-boiling mode. At the same time, there is an optimal distance at which the maximum heat transfer rate and uniformity of the temperature are achieved. Criteria and a ratio for determining the optimal distance from the spray nozzle to the heated surface are proposed. [ABSTRACT FROM AUTHOR]

The lightweight, precision and high integration of modern electronic devices lead to a sharp increase in local heat flux, which poses a severe challenge to the traditional cooling technology. There is an urgent need to find a cooling method with high heat dissipation capacity and high efficiency to meet the requirements of today's thermal management systems. Based on the Joule Thomson effect of carbon dioxide, a dry-ice spray cooling experimental system was established, and two types of array nozzles were designed and processed. The changing laws of cooling characteristics of tapered array nozzle and Laval array nozzle under different mass flow rates and different spray heights were discussed. The experimental results show that the heat transfer effect is the best when the spray mass flow rate is 36.29 g s−1 and the spray height is 2.5 cm, the corresponding critical heat flux is 452.03 W cm−2, the heat transfer coefficient is 36939.21 W m−2 °C−1, and the surface temperature of the simulated heat source is 37.64 °C. For Laval array nozzles and tapered array nozzles, the cooling performance of the former is better under the same experimental conditions, so the production of Laval array nozzles should be given priority in the selection of array nozzles with different parameters. [ABSTRACT FROM AUTHOR]

This paper investigates an alternative cooling method for photovoltaic (PV) solar panels by using water spray. For the assessment of the cooling process, the experimental setup of water spray cooling of the PV panel was established at Sultanpur (India). This setup was tested in a geographical location with different climate conditions. It was found that the temperature of the panel decreased from 53 to 23 °C and the total power was increased by 15.3% by the water spray cooling. The effectiveness of the system is also increased by its cleaning effects. The efficiency of this solar PV is reduced with the increase of panel temperature. The experiments showed that the PV cell efficiency was dropped by 0.5% with an increase of 1 °C in panel temperature. However, the electrical efficiency of the panel was increased by 0.28%/0.2 °C of temperature drop by the single nozzle spray cooling. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effects of multiwalled carbon nanotubes (MWCNTs) on the spalling and cracking behavior of concrete exposed to high temperatures, and also consider the mechanism of different cooling methods (including natural air cooling, spray cooling, and quench cooling) on its performance after high temperature. Meanwhile, the change rules of mechanical properties and pore structure of MWCNTs reinforced concrete during high temperature and cooling were explored by x‐ray computed tomography. The results demonstrated that spalling and cracking behavior of the concrete specimens exposed to high temperatures was effectively controlled by adding MWCNTs. Consequently, the thermal resistance and residual mechanical properties of concrete exposed to high temperatures were significantly improved. Moreover, the mesoscopic and microscopic observation showed that the MWCNTs have a favorable impact on reducing the porosity of the concrete specimens below 600°C. However, when the temperature exceeded 600°C, MWCNTs reached the burning point and lost the bridging effect. No trace of MWCNTs was observed in the concrete specimen, but the cumulative mitigation decreased the possibility of cracking and spalling of concrete at 800°C. Additionally, considering the influence of cooling methods, it is found that the spalling and cracking of the concrete specimens after high temperature caused by quench cooling were the most serious, while that of caused by spray cooling were the least. [ABSTRACT FROM AUTHOR]

The GH4169 superalloy has the characteristics of high strength, strong thermal stability, large specific heat capacity, small thermal conductivity, etc., but it is also a typical hard-to-cut material. When cutting this material with ordinary cutting tools, the cutting force is large, and the cutting temperature is high, which leads to severe tool wear and short service life. In order to improve the performance of tools when cutting GH4169, reduce the cutting temperature, and extend the service life of the tool, micro-textured tools were used to cut GH4169 in spray cooling. The effects of micro-texture morphology and dimensional parameters on cutting temperature were analyzed. Firstly, tools with micro-textures of five different morphologies were designed near the nose on the rake face of the cemented carbide tools. The three-dimensional cutting models of the micro-textured tools with different morphologies were established by using ABAQUS, and a simulation analysis was carried out. Compared with the non-textured tools, the micro-texture morphology with the lowest cutting temperature was selected according to the simulation results of the cutting temperature. Secondly, based on the optimized morphology, tools with micro-textures of different size parameters were designed. When cutting GH4169, the cutting temperature of the tools was simulated and analyzed, and the size parameters of the micro-textured tools with the lowest cutting temperature were selected as well. Finally, the designed micro-textured tools were processed and applied in cutting experiments. The simulation model was verified in the experiments, and the influence of size parameters of micro-textures on the cutting temperature was analyzed. This paper provides a theoretical reference and basis for cutting GH4169 and the design and application of micro-textured tools. [ABSTRACT FROM AUTHOR]

This study explores the performance of micro-textured tools when cutting GH4169 during spray cooling. First, the morphologies of the micro-textures were selected according to the simulation and experiments. Secondly, cutting experiments were carried out during spray cooling. As appropriate for each experiment, regression models of cutting force, cutting temperature, or tool wear area were established, and variance analysis was conducted. The cutting force, cutting temperature, and tool wear area functions were obtained from the respective regression models. Based on these functions, the micro-texture parameters were optimized using the response surface method with the cutting force, cutting temperature, and rake face wear area as the objectives. Finally, a full factor experiment on the micro-texture parameters was designed using Minitab, and cutting experiments were conducted using micro-textured tools with these parameters. Taking a relatively low cutting force, cutting temperature, and tool wear as the objectives, a genetic algorithm multi-objective optimization model for the micro-texture parameters of the tools was established, and the model was solved using the NSGA-II algorithm to obtain a Pareto solution set and micro-texture parameters with a good, comprehensive cutting performance. The micro-texture morphology and parameters obtained in this study can also be used for cutting other high-temperature alloy materials with similar properties to GH4169. This research method can also be used to optimize micro-textured tools for cutting other materials. [ABSTRACT FROM AUTHOR]

Vibrations profoundly influence the liquid film formed by spray droplets in spray cooling applications. However, understanding heat transfer mechanisms in the non-boiling region under vibrating conditions is limited in the existing literature. This study aims to bridge this gap by numerically investigating the heat transfer performance of spray cooling in non-boiling regions under vibration using the Lagrange-Euler method. To validate the computational fluid dynamics (CFD) model, experimental measurements of spray heat transfer were conducted on a heated vibrating surface test rig. The results demonstrate that the average film thickness (AFT) and average film velocity (AFV) increase at lower frequencies, leading to a decrease in the heat transfer coefficient. Conversely, the AFT decreases at higher frequencies while the AFV remains relatively constant. This reduction in AFT enhances the heat transfer coefficient, resulting in an up to 12% improvement in heat transfer performance. When a larger vibration amplitude is introduced, a higher inertial force acts on the liquid film, causing it to converge towards the centre. Generally, the heat transfer coefficient of spray cooling in the non-boiling region decreases as the vibration amplitude increases.