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ObjectivesThe high-efficiency internal cooling technology of turbine blade is crucial for improving the thermal efficiency of gas turbine. As an important component of the gas turbine, it is essential to conduct research on the cooling performance of rotor blade. Due to significant effect of Coriolis force, buoyancy force, and channel structure on the cooling performance of rotating internal channel of turbine blade, this paper summarized the research status and development trends of rotating internal cooling channel based on these effect factors.MethodsA new structural design of rotating internal cooling channels was introduced, and a new rotating internal cooling channel structure suitable for double-walled blade configurations was proposed.ConclusionsDouble-sided enhanced U-shaped channels can utilize the enhanced heat transfer effect of Coriolis force, resulting in better cooling performance than traditional rotating U-shaped channels. There is a broad room for improvement in the internal cooling of gas turbine rotor blades.

One of the challenges in the transfer of heat during the mechanical machining process is the coolant substance used in the internal cooling method which is generally liquid water or a water-based coolant. This limits the heat transfer capacity insofar as the thermal conductivity of liquid water is concerned. The other difficulty is the requirement for an external mechanical system to pump the coolant around the internal channel, providing efficient transfer of the accumulated thermal energy. This study proposes a novel method to address this issue by using liquid gallium which provides the means to transfer the excess heat generated during the cutting process by integrating the design into an aluminium oxide insert. Combining this with a magnetohydrodynamic drive, the coolant system operates without the need for mechanical input. Liquid gallium is nontoxic and has a much higher thermal conductivity over liquid water. Investigations of the novel cooling system is performance compared against liquid water through numerical modelling, followed by an experimental machining test to ascertain the difference in heat transfer effectiveness, tool wear rates and workpiece surface finish when compared to dry machining and external cooling conditions on stainless steel 316L. Without cooling, experimental machining tests employing a cutting speed of Vc = 250 m min−1 resulted in a corner wear VBc rate of 75 μm, and with the magnetohydrodynamic-based coolant on, produced a VBc rate of 48 μm, indicating a difference of 36% in relative tool wear under the same cutting conditions. Increasing the cutting speed Vc to 900 m min−1, produced a corner wear VBc rate of 357 μm without the active coolant and a VBc rate of 246 μm with the magnetohydrodynamic-based coolant on, representing a decrease of 31% in relative tool wear. Further tests comparing external liquid water cooling against the liquid gallium coolant showed at Vc = 250 m min−1, a difference of 29% in relative tool wear rate reduction was obtained with the internal liquid gallium coolant. Increasing the cutting speed to Vc = 900 m min−1, the data indicated a difference of 16% relative tool wear reduction with the internal liquid gallium. The results support the feasibility of using liquid gallium as an internal coolant in cutting inserts to effectively remove thermal energy. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Xi'an Jiaotong University is the property of Editorial Office of Journal of Xi'an Jiaotong University 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.)

AbstractIn this paper, a plasma actuator (PA), treated by the Suzen model, is introduced into film cooling, and four rows of rectangular ribs are employed in internal cooling. Combined action and individual action of film cooling and internal cooling are then investigated at four blowing ratios (M = 0.25; 0.5; 0.75; 1.0). Results show that (no PA, no ribs) the coolant is ejected from the film hole in a spiral form under the action of internal crossflow, and its distributions are inclined to crossflow direction. When the plasma actuator is opened (no ribs), the strength and scale of the counter-rotating vortex pairs are weakened, and the motion of coolant is accelerated, the average cooling effectiveness shows an increase of 82.4% (M = 0.25), 98.9% (M = 0.5), 33.4% (M = 0.75) and a decrease of 2.1% (M = 1.0), the spanwise cooling effectiveness is raised by 57.3–143.3% for each streamwise position, the flow coefficient is lowered by 1.8–3.2%. Ribs (no PA) interfere with the coolant flow in the internal channel, reducing the rotation degree and exit momentum of the coolant, and greatly eliminate the uneven distribution of coolant along the spanwise direction, resulting in an enhancement of 50.4–162.8% in the spanwise cooling effectiveness and of 59.2% (M = 0.25) and 79.5% (M = 0.5) in average film cooling effectiveness. The effect of combined action (PA plus ribs) is lower than those effects of individual factors, and wall average film cooling effectiveness with PA and ribs exhibits a 62.4% (M = 0.25) and 49.4% (M = 0.5) higher to PA off a case (no PA, no ribs); however, a local or global heat transfer deterioration appears at M = 0.75 and 1.0. [ABSTRACT FROM AUTHOR]

The trailing edge of turbine blades poses a significant challenge for research in internal cooling technology. In previously published studies on heat transfer coefficient (HTC), the limitations of experimental testing techniques have hindered the ability to scale up the rotational radius ratio in a similar manner, resulting in significantly lower Buoyancy number (Buo) values tested compared to the actual operating conditions of turbine blades, leading to biased HTC results.This article delves into experimental studies to explore the HTC of a pin-fin channel. The experimental testing encompassed a broad spectrum of conditions, including varying inlet Reynolds numbers ranging from 5000 to 70,000, rotation numbers (Ro) from 0 to 1.0, temperature ratio from 0.04 to 0.22, rotational radius ratio (r/D) from 20 to 52.33, and Buo from 0 to 2.55. For the same Buo, there is a significant difference in HTC, with the high Ro and low TR scenario demonstrating a distinct advantage in HTC compared to the low Ro and high TR condition. Furthermore, heat transfer enhancement was observed at approximately 30 % of the dimensionless positions. Therefore, to achieve more accurate HTC results, it is necessary to precisely match the values of Re, Ro, Buo, TR, and r/D.

The main study objective was to evaluate the influence of the perspective "Internal" (coolant is supplied to the channel inside the indexable insert body) and "Combined" (coolant is supplied to the rake and flank faces through the channel inside the indexable insert body) Cooling Schemes on the temperature of the contact point between the tool and the workpiece, on the heat distribution inside the indexable insert body, and (additionally) on the cutting forces. The contact point temperature and cutting forces were investigated during the non-orthogonal turning of SUS304 Stainless Steel at speeds of 180, 140, and 100 m/min with constant feed and depth of cut. The heat distribution was examined through 2D simulations using DEFORM 2D3D software. The evaluation of the perspective cooling schemes' influence on the selected parameters was performed by comparing the obtained data with the test results of the "traditional" external cooling and dry cutting under similar cutting modes. According to the comparison results, the perspective cooling schemes demonstrated a slight decrease (~3-7%) in the temperature of the contact point between the tool and the workpiece, a significant decrease in the heat distribution (~38-55%) inside the indexable insert body and, in some cases, a decrease of the cutting forces. Based on the study results, the authors confirmed the influence of perspective cooling schemes on the selected parameters and suggested a further positive effect of these schemes' utilization on the cutting tool life.

This numerical study examined the effects of a curved turning vane on the heat transfer and pressure loss of a four-pass internal cooling channel. Three-dimensional omega-based Reynolds stress (RSM-ω) turbulence model equations were used in the computation process. Three different curved turning vane configurations were studied using a simple, without a turning vane under stationary and rotating conditions for Reynolds numbers between 20,000 and 60,000 and a rotation number of 0.042. The numerical results showed good agreement with previous experimental data. Under both stationary and rotating conditions, the curved turning vane in a hub turn reduced the pressure drop significantly compared to the conventional turning vanes. Although a curved turning vane attenuated overall heat transfer, the local heat transfer increased it in particular regions, such as the hub turn and the fourth turn of cooling passages, particularly in cases with smaller radii. Coolant flow through the hub turn of the serpentine channel can reduce recirculation, separation, and flow impingement, which are unfavorable factors of pressure loss, owing to the semi-circular configuration of the curved turning vane. Regarding the rotating conditions, four-pass channels with a smaller radius of a curved turning vane provide better overall cooling performance. [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.)

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.)

A tool life test was performed in the conventional (nonorthogonal) cutting mode to determine the effects of cooling schemes, based on the coolant circulation inside an indexable insert body, on cutting tool wear. Two cooling schemes — a Combined Scheme, in which the coolant enters the cutting zone through a channel inside the insert body, and an Internal Scheme, in which the coolant circulates in the channel inside the insert body without entering the cutting zone — were compared with the traditional external cooling and dry cutting. All schemes were performed by using a special (universal) turning tool prototype. The tests were conducted at cutting speeds of 180 m/min and 100 m/min, with a constant feed and depth of cut. The evaluation criteria were (based on ISO standard 3685:1993) flank wear VBb and crater depth KT at a minimum cutting time of 30 min (if the selected wear limit values had not been reached earlier). Additionally, the values of cutting force components and the parameters of the chips (shape, mass, length, etc.) were obtained for each tested scheme. The test results allowed us to draw conclusions not only about the effects of each proposed cooling scheme on the tool wear parameters, but also about the changes in the shear plane angle and shear strain values due to the use of each proposed scheme. [ABSTRACT FROM AUTHOR]

Drill bits with internal cooling capabilities are still not employed in stone machining practices within shop floor environments. Therefore, a conventional industrial drill bit used in stone machining was subject to a redesign wherein an axial cooling channel was machined throughout its body. A comparison was drawn between the standard drill bit without cooling capabilities and the redesigned drill bit, which used compressed air as a cooling medium. The experiment was performed by drilling three types of stone samples varying in hardness with nine combinations of cutting speed and feed rate. During the machining process, two types of process signals were continuously measured—namely, cutting forces and vibrations. Additionally, the cutting edges of the drill bits were inspected after a specific number of drilling cycles using a vision system. The primary objective of this study was to compare the cutting forces and tool wear dynamics achieved by those two drill bits. Furthermore, the usage of vibration signals in the classification of stone hardness during machining with an internally cooled drill bit was additionally analyzed. The results of this study unveiled improvement in minimizing cutting forces, vibrations, and the intensity of tool wear when utilizing an internally cooled drill bit. Even though the machining system generally exhibited lower vibrations, vibration signals again demonstrated commendable efficacy in classifying stone hardness. [ABSTRACT FROM AUTHOR]

Background: Within professional European competitions, matches can be played in extreme environmental temperatures, ranging from −5 °C to +30 °C in different countries. Furthermore, the World Cups are usually played in the summer months, when temperatures can exceed 35 °C, increasing physiological stress. Practical and cost-effective cooling strategies may be implemented to help players and referees to cope with exercising in the heat. No study has evaluated the effect of non-thermal internal cooling techniques regarding performance responses on elite football referees, so far. This study aims to analyse the effects of a menthol mouth rinse regarding physical, physiological, and perceptual performance in elite male football referees, during a 90-min football protocol in the heat. Methods: At least thirteen male football referees will be recruited to perform two intermittent football protocols, separated by no less than 7 days. After passing the eligibility criteria, the participants will be randomly assigned to 1 of 2 beverages: (1) intervention - menthol solution 0.01% and (2) placebo - noncaloric berry-flavored solution, both at room temperature. The beverages will be given before warm-up (pre-cooling) and at the half-time (per-cooling). The trials will follow a randomized counterbalanced crossover design, single blinded, and will take place in indoor facilities, with Wet Bulb Globe Temperature (WBGT) > 30 °C, at the same time of the day to control for circadian variations. Impact of the project: The results of this study are expected to determine whether mouth rinsing a menthol solution before and during a football exercise protocol performed in the heat will alter perceptual measures and help ease physiological strain and attenuate performance decrements in elite male football referees, comparing to a non-cooling strategy. Thus, we can be closer to defining nutritional strategies of internal cooling that may be an advantage for the performance of the football referees in the heat. Trial registration: www.ClinicalTrials.gov NCT05632692 registered on 20 November 2022.

Liquid desiccant dehumidifiers are useful for simultaneously recovering heat and water from flue gas. Internally cooled dehumidifiers are generally superior to adiabatic dehumidifiers in terms of the consumption of the desiccant and the size of the equipment required. This study examines the performance of a counter-flow dehumidifier through experiments and simulations under different operating conditions, and analyzes the moisture effectiveness and enthalpy effectiveness as performance indices. By applying correlations from the literature, the theoretical model can predict the performance of the dehumidifier within an acceptable range of accuracy. According to the experimental results, droplets were visible at a low desiccant flow rate when the velocity of the gas was above 4.88 m/s. Moreover, a higher cooling ratio and a higher temperature of the solution enhanced the effectiveness of the dehumidification. A temperature cross occurred between the gas and the solution when the mass transfer was sufficiently high, which reflects better heat transfer performance than the conventional convective heat exchanger. [ABSTRACT FROM AUTHOR]

All the studies about pin-fins so far focus on investigating the geometry and configurations of pin-fins to perceive the mechanism of the flow and vortices and maximize the heat transfer efficiency index (HTEI) of the channel. However, questions remained about the effect of the endwall, which can be used to develop and conserve the vortices around the pins. These vortices are typically the key factors influencing the heat transfer capacity of the channel but have not been investigated properly. This work numerically investigates the vortices development and preservation of the channel with three types of endwall-turbulation systems, i.e., the flat endwall, the protruding endwall, and the indented endwall, and the structure of the flow therein. The heat transfer characteristics, which include Nusselt number, friction factor, and HTEI, are studied and compared between all cases with Reynolds numbers ranging from 7400 to 36000. It is reported in the results that, with these new endwall configurations, the high heat transfer regions near the pin-fins are remarkably enlarged compared to the flat endwall. Moreover, in the meantime, both the new endwall configurations enhanced the heat transfer capacity of the channel near the pin-fins, represented by the Nusselt number. The HTEI of these two new designs outperform the baseline case by 37.8 % with the indented endwall and 15.9 % with the protruding endwall. It is discovered that the increase in Nu when applying the trapezoidal endwall to the channel is mainly produced by the combination of the indentations and the protrusions. The protrusions are meant to increase the momentum of the gas passing through it so that the flow will interact more productively with the heated wall. The indentations, on the other hand, enlarge the area of the horseshoe vortices (HV) and preserve it when it is on the verge of collapse. By varying the height of the indentation and the protrusion, it is found that with the small height, both configurations produce a much lower friction factor but much higher heat transfer capacity, leading to a relatively higher HTEI, up to 77.7 % and 41.5 % higher than the flat endwall case of the indented and protruding endwall, respectively. The investigations resulted in diminishing the wake behind the pin-fin with a high-height trapezoidal endwall. For the indented endwall, the deep endwall increases the velocity at the entrance of the indentations and induces more turbulence when the flow exits them. These phenomena result in higher heat transfer of the channel. Besides, the highly elevated protruding endwalls increase heat transfer by creating more turbulence around them and the pin-fins but induce more pressure loss penalty. These results indicated the great potential for improving the heat transfer capability of pin-fins by optimizing endwall con-figurations, which could benefit future designs for industries. [ABSTRACT FROM AUTHOR]

Magnesium alloys have broad applications, including medical implants and the aerospace sector owing to their great density and high strength-to-weight ratio. Dry cutting is a frequent technique for machining this material. However, it always leads to an excessive rise in temperature due to the absence of cooling at the cutting zone, which affects the machined surface integrity and chip morphology. In this study, chip morphology and surface integrity of the AZ31 magnesium alloy were investigated in the turning process using an internal cooling method called submerged convective cooling (SCC) to overcome the absence of cooling in dry cutting. This method can exploit the advantage of the high specific heat capacity of water as a cooling fluid without any reaction between water and magnesium to create a cooling element in the cutting zone. The chip morphologies and surface integrity were analyzed experimentally with varying cutting speeds under SCC and dry cutting. The experimental results revealed that SCC and dry cutting produced saw-tooth or serrated chip formation. The chips produced in dry cutting were continuous, while SCC was short and discontinuous as a result of a severe crack on the back surface of the chip. It was discovered that the grain refinement layer on the machined samples was thinner under SCC turning. SCC machining increased the microhardness of the AZ31 magnesium alloy by 60.5% from 55 HV to 88.3 HV, while dry turning exhibited a 49% increase in microhardness. The result revealed that surface roughness improved by 10.8%, 9.4% and 4.7% for cutting speeds (V) of 120, 180, and 240 m/min, respectively, under the SCC internal cooling. Based on the result obtained, SCC cutting outperformed dry cutting in terms of chip breakability, grain refinement, microhardness, and surface roughness. [ABSTRACT FROM AUTHOR]

The heat transfer simulations of turbine blades with internal cooling are faced with so many uncertainties, of which some originate from the secondary air system, including the inlet hot gas temperature and pressure and the cooling side boundary conditions, and the blade material. The main objective of this work is to carry out a suitable sensitivity analysis on a specific novel turbine vane to improve the thermal performance of its internal cooling system and to quantify how the uncertainties on the designed/calculated values can desirably/undesirably affect the maximum blade surface temperature, which can consequently affect the gas turbine engine efficiency. Furthermore, the sensitivity analysis is carried out to find the effects of uncertainties of a number of key parameters on the resulting blade temperature distribution. To arrive at trustworthy conclusions, the conjugate heat transfer (CHT) method is used to analyze the heat and fluid flow behavior. This work suitably develops a CHT-based method/solver to perform the proposed study. This method/solver uses a segregated iterative procedure, in which the outer hot gas region is simulated using the computational fluid dynamics (CFD) solver, the flow passing through the connected internal cooling passages is calculated using a 1D correlated-based solver, and the vane conduction is predicted using a 3D finite-element solver, which are fully coupled. The results show that the cooling channel wall temperature has a direct impact on the convective coefficient magnitude; especially in lower temperature regions. As a novel contribution, this work takes into account the cooling wall temperature influence on the 1D code calculations. To implement this, an artificial neural network is suitably trained to predict better convective coefficient. The results of this developed CFD-CHT code are validated against experimental data available for a benchmark vane. Eventually, the sensitivity analysis is carried on the present specific novel turbine vane. [ABSTRACT FROM AUTHOR]

Magnesium alloys are lightweight materials which exhibit high specific strength and is broadly used in aerospace, automotive, electronics, and biomedical. Dry cutting is a common practice in machining this material which always results to an excessive rise in temperature due to the absence of cooling at the cutting zone. The low melting point of AZ31 magnesium alloy always puts the process to the inevitable built-up edge (BUE) and built-up layer (BUL) formation. This study implemented a novel work in turning AZ31 magnesium alloy via an internal cooling technique, known as submerged convective cooling (SCC), to compensate for the absence of cooling in dry cutting. The experimental result revealed that SCC outperformed dry cutting in adhesion wear mechanism, cutting force and temperature due to the cooling induced. SCC recorded up to 15% reduction in cutting temperature with 6% and 12% reduction in cutting and feed force, respectively. In addition, SCC significantly reduced BUE and BUL formation, consequently restrained cutting force fluctuation, owing to the cooling effect of SCC. This research provides an insight into the potential of implementing internal cooling in the severe plastic deformation process, especially in cutting ductile materials like magnesium alloy.

Large-eddy simulations (LES) were performed to study the turbulent flow in a channel of height H with a staggered array of pin fins with diameter D = H/2 as a function of heating loads that are relevant to the cooling of turbine blades and vanes. The following three heating loads were investigated—wall-to-coolant temperatures of Tw/Tc = 1.01, 2.0, and 4.0—where the Reynolds number at the channel inlet was 10,000 and the back pressure at the channel outlet was 1 bar. For the LES, two different subgrid-scale models—the dynamic kinetic energy model (DKEM) and the wall-adapting local eddy-viscosity model (WALE)—were examined and compared. This study was validated by comparing with data from direct numerical simulation and experimental measurements. The results obtained show high heating loads to create wall jets next to all heated surfaces that significantly alter the structure of the turbulent flow. Results generated on effects of heat loads on the mean and fluctuating components of velocity and temperature, turbulent kinetic energy, the anisotropy of the Reynolds stresses, and velocity-temperature correlations can be used to improve existing RANS models. [ABSTRACT FROM AUTHOR]

Increases in power density and thermal efficiency of a highly efficient gas turbine engine motivate an ever-mounting turbine entry temperature. The combined metallurgical and cooling advancements ensure the structural integrity of a gas turbine rotor blade that spins at high rotor speeds in a gas stream with temperatures above the melting point of the blade material. The cooling performances promoted by a variety of heat transfer enhancement methods typical of the coolant channels of the leading edge, the mid-chord region, and the trailing edge of a gas turbine rotor blade are reviewed. The manifested rotational effects on the aerothermal performances of impinging jets and swirl chambers for leading-edge cooling, multi-pass ribbed, dimpled, and/or wavy channels over the mid-chord region, as well as pin fin and latticework narrow ducts in the trailing edge of a gas turbine rotor blade, are summarized and cross-examined. Research orientations for future cooling studies aimed at preventing the development of hot spots in a gas turbine rotor blade are recommended. [ABSTRACT FROM AUTHOR]

Triply periodic minimal surfaces (TPMS) have shown better mechanical performance, mass transfer, and thermal conductivity than conventional and strut-based structures, which have been employed in different disciplines. Most of the literature investigates different TPMS topologies in cooling channels to enhance thermal performance due to the smooth curvature and large surface area. However, a deeper investigation of the effects of TPMS design variables and the thermal performance advantages of cooling channels is required. This review details the effects of TPMS design variables, i.e., porosity, wall thickness, and unit cell size, on flow and heat transfer enhancement. It is found that varying the design variables significantly changes the flow and heat transfer characteristics. Also, by comparing TPMS and conventional cooling structures, it is found that most TPMS structures show better thermal performance than other strategies. Moreover, different fabrication methods for TPMS-based cooling channels in recent investigations are collected and discussed. In light of the reviewed literature, recommendations for future research suggest that more experimental and numerical studies on the flow and heat transfer for different cooling applications are needed. Therefore, this review serves as a reference tool to guide future studies on the flow and heat transfer of TPMS-based cooling channels. [ABSTRACT FROM AUTHOR]

For the purpose of solving the problems about grinding heat affecting workpiece surface quality during grinding Inconel 718, a novel internal cooling grinding wheel with phyllotaxis distribution of abrasive grain family is proposed in this paper. The coolant outlet shapes of replaceable abrasive ring are designed into waist-shaped and circular to investigate the influence of the surface structure on grinding performance. Then, CFD method is used to analyze the flow field distribution characteristics in grinding zone under different outlet shapes and rotation speeds. Finally, grinding experiments are carried out on Inconel 718. The simulation results reveal that the flow field distribution of the waist-shaped outlet is smoother and wider. The blind area of coolant is less that the maximum reduction is 54.61% compared with circular outlet. The increased rotation speed accelerates the flow rate of coolant at the outlet under the same outlet shape, without obvious effect on the fluid distribution range. The experimental results demonstrate that compared with the external flood cooling, internal cooling has excellent cooling and heat transfer capacity because of the avoidance of the air barrier effect. With the same internal cooling, the waist-shaped outlet has better grinding performance. When the rotation speed rises from 1000 to 3000 rpm, the maximum reduction of grinding temperature, surface roughness, and surface microhardness are 24.92%, 26.81%, and 4.09%, respectively. The maximum increase of surface residual compressive stress is 13.31% (about 80.73 MPa). [ABSTRACT FROM AUTHOR]

• Desiccant-coated adsorbers with thin silica gel coating on metal are fabricated. • Internally-cooled water harvesting promotes the sorption process. • A continuous water harvesting system is assembled with the cooling recovery. • The device produces a productivity of 0.77–3.98 L water /kg sorbent /day. • The cooling and heating operations could be integrated into building sectors. Sorption-based atmospheric water harvesting holds promise for alleviating water scarcity, but current prototypes have not shown significant increases in practical yields despite efforts in the enlarged engineering scale. This is due to weakened heat and mass transfer with a packed sorbent bed. In this work, the desiccant-coated adsorbers were employed to fabricate the water harvesting device that incorporates internal fluid for cooling and heating during sorption and desorption. Featured with an internal cooling effect, practical water productivity could be improved by 1.75–9.96 times with a low desorption temperature (45–62 °C). The continuous water harvesting system could produce 0.77–3.98 L water /kg sorbent /day with a thermal energy consumption of 7.7–30.4 MJ/kg in wide climates from 20 % to 80 % RH, providing a reference for device design in the engineering view. The demonstration revealed that using natural cooling in the sorption stage has great benefits in improving water harvesting performance, which can be integrated into the building sectors or a wider range of scenarios. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Tumescent anesthesia not only prolongs the operation time but also induces postoperative pain, bruising, and swelling. This study investigated the effectiveness and safety of tumescentless RFA using an internal cooling system with a VENISTAR catheter and local hypothermia. Methods: We retrospectively analyzed patients who had undergone RFA for above-knee (AK) great saphenous vein (GSV) between March 2023 and November 2023. We compared the efficacy and safety of tumescentless RFA between group T (conventional tumescent group, n = 50) and group N (non-tumescent group, n = 59). Results: The operative time was shorter in group N than in group T (group N: 31.37 min, group T: 42.31 min, p < .01), with no severe adverse events occurred in either group, such as endovenous heat-induced thrombosis or deep vein thrombosis. Postoperative pain (Group N, 0.53% vs Group T, 0.52%; p = .86), postoperative complications such as bruising (Group N, 6.78% vs Group T, 4%; N= .34) and paresthesia (Group N, 1.7% vs Group T, 6%; p = .27) showed no significant difference between the two groups on postoperative day 10. Conclusion: Tumescentless RFA with internal cooling and local hypothermia shows promising results with minimal complications. This novel approach represents a recent advancement in endovenous RFA that omits additional tumescent anesthesia. [ABSTRACT FROM AUTHOR]

Drill bits with internal cooling capabilities are still not employed in stone machining practices within shop floor environments. Therefore, a conventional industrial drill bit used in stone machining was subject to a redesign wherein an axial cooling channel was machined throughout its body. A comparison was drawn between the standard drill bit without cooling capabilities and the redesigned drill bit, which used compressed air as a cooling medium. The experiment was performed by drilling three types of stone samples varying in hardness with nine combinations of cutting speed and feed rate. During the machining process, two types of process signals were continuously measured—namely, cutting forces and vibrations. Additionally, the cutting edges of the drill bits were inspected after a specific number of drilling cycles using a vision system. The primary objective of this study was to compare the cutting forces and tool wear dynamics achieved by those two drill bits. Furthermore, the usage of vibration signals in the classification of stone hardness during machining with an internally cooled drill bit was additionally analyzed. The results of this study unveiled improvement in minimizing cutting forces, vibrations, and the intensity of tool wear when utilizing an internally cooled drill bit. Even though the machining system generally exhibited lower vibrations, vibration signals again demonstrated commendable efficacy in classifying stone hardness.

Exercise in a hot and humid environment may endanger athlete’s health and affect physical performance. This systematic review aimed to examine whether internal administration of ice, cold beverages or menthol solutions may be beneficial for physical performance when exercising in different environmental conditions and sports backgrounds. A systematic search was performed in PubMed, Web of Science, Scopus and SPORTDiscus databases, from inception to April 2022, to identify studies meeting the following inclusion criteria: healthy male and female physically active individuals or athletes (aged ≥18 years); an intervention consisting in the internal administration (i.e., ingestion or mouth rinse) of ice slush, ice slurry or crushed ice and/or cold beverages and/or menthol solutions before and/or during exercise; a randomized crossover design with a control or placebo condition; the report of at least one physical performance outcome; and to be written in English. Our search retrieved 2,714 articles in total; after selection, 43 studies were considered, including 472 participants, 408 men and 64 women, aged 18-42 years, with a VO2max ranging from 46.2 to 67.2 mL⋅kg–1⋅min–1. Average ambient temperature and relative humidity during the exercise tasks were 32.4 ± 3.5°C (ranging from 22°C to 38°C) and 50.8 ± 13.4% (varying from 20.0% to 80.0%), respectively. Across the 43 studies, 7 exclusively included a menthol solution mouth rinse, 30 exclusively involved ice slurry/ice slush/crushed ice/cold beverages intake, and 6 examined both the effect of thermal and non-thermal internal techniques in the same protocol. Rinsing a menthol solution (0.01%) improved physical performance during continuous endurance exercise in the heat. Conversely, the ingestion of ice or cold beverages did not seem to consistently increase performance, being more likely to improve performance in continuous endurance trials, especially when consumed during exercises. Co-administration of menthol with or within ice beverages seems to exert a synergistic effect by improving physical performance. Even in environmental conditions that are not extreme, internal cooling strategies may have an ergogenic effect. Further studies exploring both intermittent and outdoor exercise protocols, involving elite male and female athletes and performed under not extreme environmental conditions are warranted.Systematic review registration: [https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021268197], identifier [CRD42021268197].

The investigation of the problem of internal cooling system inside a vented cavity utilizing P, PI, and PID controllers are carried out in this paper. The cavity consists of an outlet, an airflow inlet, a temperature sensor, and an isothermal heat source. The remaining walls are kept at ambient temperature. A temperature probe at a central location is used to measure the internal cooling condition and hence, to control the inlet air velocity via three different types of controller arrangements. The governing Navier-Stokes and energy equations along with appropriate boundary conditions are solved using Galerkin finite element technique. Parametric simulation is conducted by considering different values of proportional (0.01, 0.05, 0.1 ms−1K−1), integral (0.1, 0.2, 0.5 ms−2K−1), and derivative (0.001, 0.0001, 0.00001 mK−1) gains for three different types of controllers. The velocity and temperature contours are used to visualize the thermo-fluid behaviors of airflow inside the cavity. Besides, non-dimensional fluid temperature of the cavity at the set point is monitored closely to determine and compare the performance of the controllers.

Purpose: To compare the physiological and performance effects of ad libitum cold-fluid (CF) and ice-slurry (IS) ingestion on cycling time-trial (TT) performance in the heat. Methods: Seven well-trained male triathletes and cyclists completed 2 maximal-effort 40-km cycling TTs in hot (35°C) and humid (60% relative humidity) conditions. In randomized order, participants ingested CF or IS (initial temperatures 4°C and -1 °C, respectively) ad libitum during exercise. At each 5-km interval, time elapsed, power output, rectal and skin temperature, heart rate, and perceptual measures were recorded. The actual CF and IS temperatures during the 40-km TT were determined post hoc. Results: Performance time (2.5% ± 2.6%, ES = 0.27) and mean power (-2.2% ± 3.2%, ES = -0.15) were likely worse in the IS trial. Differences in thermoregulatory and cardiovascular measures were largely unclear between trials, while feeling state was worse in the later stages of the IS trial (ES = -0.31 to -0.95). Fluid-ingestion volume was very likely lower in the IS trial (-29.7% ± 19.4%, ES = -0.97). The temperatures of CF and IS increased by 0.37°C/min and 0.02°C/min, respectively, over the mean TT duration. Conclusions: Ad libitum ingestion of CF resulted in improved 40-km cycling TT performance compared with IS. Participants chose greater fluid-ingestion rates in the CF trial than in the IS trial and had improved feeling state. These findings suggest that ad libitum CF ingestion is preferable to IS during cycling TTs under conditions of environmental heat stress. [ABSTRACT FROM AUTHOR]

• New structures based on NACA00XX fins are proposed. • The NSGA-II algorithm is employed to conduct multi-objective optimization with two objective functions and ten design variables. • The optimal solutions greatly improve the flow performance. This paper presents the design of new internal cooling structures basing on NACA00XX fins in the cooling channel of a sensor probe. Numerical simulations are conducted to compare the flow and heat transfer performance of each fin structure under different working conditions. The Nusselt number Nu and friction factor f are used as objective functions, considering the flow and heat transfer performance. The arrangement angles of eight fin structures at the bottom of the channel, the inlet velocity of the channel, and the thickness of the fin structures are considered as design variables. The NSGA-II algorithm is employed for multi-objective optimization with two objective functions and ten design variables. The optimized arrangement greatly improves the flow performance. For the two optimal solutions A and B of the Pareto front, the Nusselt number Nu decreases by 3.08% and increases by 0.84% respectively, the friction factor f decreases by 24.73% and 21.04% respectively. [ABSTRACT FROM AUTHOR]

Magnesium alloys have broad applications, including medical implants and the aerospace sector owing to their great density and high strength-to-weight ratio. Dry cutting is a frequent technique for machining this material. However, it always leads to an excessive rise in temperature due to the absence of cooling at the cutting zone, which affects the machined surface integrity and chip morphology. In this study, chip morphology and surface integrity of the AZ31 magnesium alloy were investigated in the turning process using an internal cooling method called submerged convective cooling (SCC) to overcome the absence of cooling in dry cutting. This method can exploit the advantage of the high specific heat capacity of water as a cooling fluid without any reaction between water and magnesium to create a cooling element in the cutting zone. The chip morphologies and surface integrity were analyzed experimentally with varying cutting speeds under SCC and dry cutting. The experimental results revealed that SCC and dry cutting produced saw-tooth or serrated chip formation. The chips produced in dry cutting were continuous, while SCC was short and discontinuous as a result of a severe crack on the back surface of the chip. It was discovered that the grain refinement layer on the machined samples was thinner under SCC turning. SCC machining increased the microhardness of the AZ31 magnesium alloy by 60.5% from 55 HV to 88.3 HV, while dry turning exhibited a 49% increase in microhardness. The result revealed that surface roughness improved by 10.8%, 9.4% and 4.7% for cutting speeds (V) of 120, 180, and 240 m/min, respectively, under the SCC internal cooling. Based on the result obtained, SCC cutting outperformed dry cutting in terms of chip breakability, grain refinement, microhardness, and surface roughness.

Low melting point and material adhesion are associated challenges of magnesium alloy, leading to extreme built-up edge (BUE) and built-up layer (BUL) formations during machining process. Dry machining is favorable for machining magnesium alloy. However, this strategy inflicts excessive adhesive wear on the cutting tool. Therefore, this current work focuses on application of an innovative cooling technique, known as submerged convective cooling (SCC) for the turning of AZ31 magnesium alloy. Prior to cutting experiment, a computational fluid dynamics (CFD) simulation was conducted to evaluate internal structure of cooling module. Based on the CFD simulation, a small inlet/outlet diameter of 3 mm significantly contributed to the reduction of the tool temperature, due to high heat transfer coefficient of cooling fluid in the SCC. From the experimental results obtained, it was evident that SCC at high cooling water flow rate of 130 mL/min effectively reduced the tool temperature, chip temperature, and tool-chip contact length by approximately 50, 8, and 28%, respectively. Consequently, it improved the surface roughness by 37%, when compared with the dry cutting condition. Finally, both BUE and BUL were observed in dry and SCC conditions, but the severity of these wear mechanisms improved or decreased remarkably under SCC conditions. [ABSTRACT FROM AUTHOR]

During the cutting process of superalloy, intense heat will be generated. Traditional external flood cooling methods require a large amount of coolant, bringing high cutting costs, serious environmental pollution, and other adverse effects. In this paper, a method combining minimum quantity lubrication (MQL) and internal cooling is proposed to accurately spray the cutting fluid into the cutting area in turning nickel-based superalloy. The heat source model for micro-lubrication cutting was established, and the heat transfer coefficient and friction coefficient under different cooling methods were calculated. Hereafter, a two-dimensional cutting finite element model was established to analyze the nickel-based superalloy turning process under different cooling conditions. Subsequently, the turning experiment of nickel-based superalloy GH4169 was carried out on the self-built turning experimental platform. The influence of different cooling methods and cutting parameters on cutting force, cutting temperature, surface roughness, chip morphology, and surface morphology of the processed workpiece was systematically studied. Furthermore, the surface roughness prediction model is obtained through the experiment results. The simulation and experiment results show that under the same cutting parameters, the cutting temperature of MQL with internal cooling is significantly lower than that of dry cutting, indicating a better cooling effect of MQL with internal cooling. Moreover, the surface morphology quality of micro-lubrication cutting is prominent compared with dry cutting. Also, the larger the cutting fluid flow, the better the surface quality. Therefore, the proposed MQL turning with internal cooling method is an environmental-friendly technology with promising application prospects. [ABSTRACT FROM AUTHOR]

Increases in power density and thermal efficiency of a highly efficient gas turbine engine motivate an ever-mounting turbine entry temperature. The combined metallurgical and cooling advancements ensure the structural integrity of a gas turbine rotor blade that spins at high rotor speeds in a gas stream with temperatures above the melting point of the blade material. The cooling performances promoted by a variety of heat transfer enhancement methods typical of the coolant channels of the leading edge, the mid-chord region, and the trailing edge of a gas turbine rotor blade are reviewed. The manifested rotational effects on the aerothermal performances of impinging jets and swirl chambers for leading-edge cooling, multi-pass ribbed, dimpled, and/or wavy channels over the mid-chord region, as well as pin fin and latticework narrow ducts in the trailing edge of a gas turbine rotor blade, are summarized and cross-examined. Research orientations for future cooling studies aimed at preventing the development of hot spots in a gas turbine rotor blade are recommended.

Large-eddy simulations (LES) were performed to study the turbulent flow in a channel of height H with a staggered array of pin fins with diameter D = H/2 as a function of heating loads that are relevant to the cooling of turbine blades and vanes. The following three heating loads were investigated—wall-to-coolant temperatures of Tw/Tc = 1.01, 2.0, and 4.0—where the Reynolds number at the channel inlet was 10,000 and the back pressure at the channel outlet was 1 bar. For the LES, two different subgrid-scale models—the dynamic kinetic energy model (DKEM) and the wall-adapting local eddy-viscosity model (WALE)—were examined and compared. This study was validated by comparing with data from direct numerical simulation and experimental measurements. The results obtained show high heating loads to create wall jets next to all heated surfaces that significantly alter the structure of the turbulent flow. Results generated on effects of heat loads on the mean and fluctuating components of velocity and temperature, turbulent kinetic energy, the anisotropy of the Reynolds stresses, and velocity-temperature correlations can be used to improve existing RANS models.

In view of the serious problem of milling heat in milling nickel-based superalloys Inconel 718, this paper investigates the heat transfer performance of internal cooling in end milling Inconel 718, and the superiority of internal cooling milling cutter's heat exchange ability during processing is explored. The flow field characteristics of cutting fluid and milling temperature are studied by Computational Fluid Dynamics (CFD) and Finite Element Method (FEM). Compared with external flood cooling, the principle of internal cooling with excellent heat transfer performance is explained and the influence of coolant pressure on lubrication performance is analyzed. Experiments for end milling of Inconel 718 under different cutting speeds and cooling conditions have been carried out. The results indicate that the simulated and measured temperatures showed an acceptable agreement. The internal cooling has better heat transfer performance compared with flood cooling. With the increase of coolant pressure, the heat exchange efficiency is gradually enhanced. When the coolant pressure rises from 2 bar to 10 bar, the milling temperature at the measured point inside the workpiece reduces by 27.55 °C, the surface roughness reduces by 12.0%, the surface residual compressive stress increases by 68.37 MPa and better surface morphology is obtained. Besides, in the experimental range, with the increase of cutting speed, milling temperature increased, the pile-up effect on the sides of scratching was weakened and better machined surface integrity was found. • Pressurized internal cooling condition benefits the milling cutter performance. • Heat transfer characteristics of coolant in internal cooling milling cutter were numerically studied. • Higher coolant pressure leads to lower temperature and more excellent surface quality. [ABSTRACT FROM AUTHOR]

Internal cooling of the gas turbine blade is critical for the durability of the blade material. One of the ways to accomplish this is by passing coolant through serpentine passages roughened with surface elements to enhance the heat transfer. In the present study, the traditional square rib (SQ-rib) placed normal to the flow direction is modified to a backward-facing step rib (BS-rib) and a forward-facing step rib (FS-rib). Large-eddy simulation (LES) is carried out for a square duct at Reb"="20000. Results show that the modified rib shapes result in substantial increase in heat transfer over the square rib with only a marginal increase in flow losses. The BS-rib shape produces the highest heat transfer augmentation followed by the FS-rib. The overall heat transfer augmentation for the BS-rib and FS-rib is 18% and 10% larger than the SQ-rib, respectively. Thermal-hydraulic performance is enhanced by 15%. [ABSTRACT FROM AUTHOR]

The cooling efficiency of blade is growing demand with increasing turbine inlet temperature in gas turbine development. Ribs used in cooling channels is a common cooling structure, therefore, many configurations were studied by previous literatures, including angle, spacing, shape etc. However, there are less research about the dislocation ribs structure. In this paper, the 45-deg parallel ribs, crossed ribs and dislocation ribs were investigated by numerical simulation, in order to reveal the heat transfer performance and flow mechanism. Refer to the experiment, SST k-ω model was applied in steady simulation, at Re from 20000 to 50000. Due to the angled ribs can induce the secondary flow and generate small helical vortices at front corner, heat transfer performance was elevated. The large rotating vortices influenced by the ribs arrangement occupy the center channel, thence the dislocation caused different flow and heat transfer results. The results shown that parallel rib has higher heat transfer enhancement than crossed ribs, but pressure loss possess considerable level. At Re=21587, the averaged turbulent kinetic energy of Case2.2 with dislocation ribs is 22.4% lower than parallel ribs. The all 45-deg crossed ribs present higher level of overall thermal performance, and Case2.2 is optimal for the range of Re investigated. [ABSTRACT FROM AUTHOR]

Triply periodic minimal surfaces (TPMS) have shown better mechanical performance, mass transfer, and thermal conductivity than conventional and strut-based structures, which have been employed in different disciplines. Most of the literature investigates different TPMS topologies in cooling channels to enhance thermal performance due to the smooth curvature and large surface area. However, a deeper investigation of the effects of TPMS design variables and the thermal performance advantages of cooling channels is required. This review details the effects of TPMS design variables, i.e., porosity, wall thickness, and unit cell size, on flow and heat transfer enhancement. It is found that varying the design variables significantly changes the flow and heat transfer characteristics. Also, by comparing TPMS and conventional cooling structures, it is found that most TPMS structures show better thermal performance than other strategies. Moreover, different fabrication methods for TPMS-based cooling channels in recent investigations are collected and discussed. In light of the reviewed literature, recommendations for future research suggest that more experimental and numerical studies on the flow and heat transfer for different cooling applications are needed. Therefore, this review serves as a reference tool to guide future studies on the flow and heat transfer of TPMS-based cooling channels.

Purpose: To determine the effect of thermal state and thermal comfort on cycling performance in the heat. Methods: Seven well-trained male triathletes completed 3 performance trials consisting of 60 min cycling at a fixed rating of perceived exertion (14) followed immediately by a 20-km time trial in hot (30°C) and humid (80% relative humidity) conditions. In a randomized order, cyclists either drank ambient-temperature (30°C) fluid ad libitum during exercise (CON), drank ice slurry (-1°C) ad libitum during exercise (ICE), or precooled with iced towels and ice slurry ingestion (15g/kg) before drinking ice slurry ad libitum during exercise (PC+ICE). Power output, rectal temperature, and ratings of thermal comfort were measured. Results: Overall mean power output was possibly higher in ICE (+1.4% ± 1.8% [90% confidence limit]; 0.4 > smallest worthwhile change [SWC]) and likely higher PC+ICE (+2.5% ± 1.9%; 1.5 > SWC) than in CON; however, no substantial differences were shown between PC+ICE and ICE (unclear). Time-trial performance was likely enhanced in ICE compared with CON (+2.4% ± 2.7%; 1.4 > SWC) and PC+ICE (+2.9% ± 3.2%; 1.9 > SWC). Differences in mean rectal temperature during exercise were unclear between trials. Ratings of thermal comfort were likely and very likely lower during exercise in ICE and PC+ICE, respectively, than in CON. Conclusions: While PC+ICE had a stronger effect on mean power output compared with CON than ICE did, the ICE strategy enhanced late-stage time-trial performance the most. Findings suggest that thermal comfort may be as important as thermal state for maximizing performance in the heat. [ABSTRACT FROM AUTHOR]

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In the present work, heat transfer analysis of a gas turbine blade consisting of 5, 7, and 10 holes, coolant flowing with suitable velocities 40 m/s, 75 m/s, and 110 m/s. From the results of several investigations, the suitable velocity ranges of coolant fluid have been taken. The coolant fluid used in this work is air, as it is suitable for aircraft engines working on open cycle gas turbines, and of course, it is cheaply available, and the blade material used is Inconel 718. Simulations are carried out using Computational Fluid Dynamics (CFD) software, ANSYS FLUENT 14.5. An analysis is being done on how the temperature is varying in blade with different configurations. Temperature distribution in the blade is studied and variation of different parameters like velocity, Nusselt number, heat transfer coefficient is observed. It is found that the blade cooling is maximum in the case of a blade with 10 holes and coolant inlet velocity 110 m/s. The average Nusselt number with the coolant inlet velocity of 40 m/s, 75 m/s, and 110 m/s is around 11, 19, and 21, respectively. The lowest temperature attained by the blade on the coolant inlet surface is 1152 K and the coolant exit surface is 1334 K. These two temperatures are observed when the blade has 10 cooling holes and coolant inlet velocity is 110 m/s. [ABSTRACT FROM AUTHOR]