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AbstractActive cooling is a technique for expanding the upper temperature limit of drilling measurement instruments. An innovative active cooling system, where a cooling device and a circuit compartment that requires cooling are located at the drill string central water eye, is proposed in this paper. The structure of three types thermal conductors that quickly transfers the heat of the chip to the refrigerator, is designed. The thermal conductivity of different structures is studied using numerical simulation methods. The research results indicate that the point-point cooling scheme that uses four small heat transfer arms to transfer heat separately is more optimal. The overall temperature inside the cabin increases, except for the chip. The environmental heat leakage is reduced by 1.2W, the cold end temperature is reduced by 23.4K, compared to the other two solutions. When the total thickness of the four heat transfer arms remains unchanged, increasing the thickness of the long heat transfer arm and decreasing the thickness of the short heat transfer arm slightly reduces the heat load of the refrigeration machine, but the temperature on the cold end of the refrigeration machine increases by 5K, and the temperature difference on the four chips narrows by 8.5K. Therefore, the use of a four claw heat transfer structure with variable thickness is the optimal choice. [ABSTRACT FROM AUTHOR]

There is a paradox involved in the operation of photovoltaic (PV) systems; although sunlight is critical for PV systems to produce electricity, it also elevates the operating temperature of the panels. This excess heat reduces both the lifespan and efficiency of the system. The temperature rise of the PV system can be curbed by the implementation of various cooling strategies. These strategies fall under three categories: passive, active, and hybrid cooling, with similar objectives of regulating excess heat generation. Employing heat pipes can be an example of the passive method, while the use of forced circulation of water flow can represent an active method. A combination of energy storage and forced convection represents an example of hybrid cooling. Most of the research has two objectives, one to obtain higher PV efficiency and another to enhance the life span of the system. This review explores various cooling strategies employed by the researchers i.e., heat pipes, heat sink, air or water channels, water spray, use of phase change material, microchannel for coolant passage, thermoelectric (Peltier) modules. In general, for passive cooling techniques, efficiency enhancement of up to 44.12 % was obtained due to the temperature reduction of around 11 °C. In the case of active cooling techniques reported better performance with PV temperature reduction as high as 55 °C. Hybrid cooling also leads to some promising performance improvements. Characteristics and performance of various cooling methods are explained in this review to provide future researchers with valuable insight and direction. This could lead to much better improvements in these cooling techniques in the near future. [ABSTRACT FROM AUTHOR]

Measurement while drilling (MWD) for high temperature well has always been a worldwide problem. So far, no effective active cooling method has been applied to MWD. In this paper, a new active cooling method based on insulated pipe is proposed. Three calculation models: theoretical model, numerical model - segmentation and numerical model - overall are established. In the theoretical model, a one-dimensional heat transfer control model is established, taking the fluid inside the insulated tube as the research object and considering the thermal resistance of the insulated tube and the heat entering the fluid through the tube wall. By iterating the boundary conditions of numerical model-segmentation, the heat transfer problem of insulated pipes with a length to diameter ratio exceeding 1000 is solved. By copying, translating, and stitching finite length meshes, the overall grid model of numerical model - overall is achieved. The calculation results of the three models mutually verify their reliability. The research results indicate that external cold fluid technology can be used for active cooling underground when the cold fluid is water. The mass flow rate of cold fluid and the heating time are the key factors affecting the temperature of cold fluid reaching the bottom hole. The cooling effect can be significantly improved by reducing the injection temperature of cold fluid and increasing cold fluid flow rate.

Abstract Amidst the industrial transformation and upgrade, the new energy vehicle industry is at a crucial juncture. Power batteries, a vital component of new energy vehicles, are currently at the forefront of industry competition with a focus on technological innovation and performance enhancement. The operational temperature of a battery significantly impacts its efficiency, making the design of a reliable Thermal Management System (TMS) essential to ensure battery safety and stability. Cylindrical power batteries are widely utilized in the industry. This article outlines the four main structures and their drawbacks of TMS for cylindrical power batteries. Among these structures, air cooling falls short in meeting high heat dissipation requirements. Liquid cooling is expensive, intricate, and adds considerable weight. Phase Change Materials (PCM) are not yet prevalent in practical applications. Similarly, heat pipes are relatively uncommon in large high-power battery packs. To better align with the new energy vehicle industry’s demands for top-notch performance, cost-effectiveness, eco-friendliness, and reliability, this paper strongly recommends delving deeper into composite cooling solutions. The construction of an economically viable and fully optimized composite cooling method is poised to become a significant scientific challenge for future research endeavors.

Among renewable resources, solar energy is abundant and cost effective. However, the efficiency and performance of photovoltaic panels (PVs) are adversely affected by the rise in the surface temperature of solar cells. This paper analyzes the idea of utilizing thermoelectric modules (TEMs) to enhance the efficiency and performance of PV panels. The proposed hybrid solar thermoelectric generation (HSTEG) system employs TEMs as thermoelectric coolers (TECs) to enhance panel efficiency and as thermoelectric generators (TEGs) to convert excess heat into additional electricity. This study includes an extensive evaluation of the proposed idea using MATLAB Simulink and experimental validation in indoor as well as outdoor environments. The use of TECs for the active cooling of the PV system leads to an increase in its efficiency by 9.54%. Similarly, the passive cooling by TECs along with the additional power generated by the TEGs from the excessive heat led to an increase in the efficiency of the PV system of 15.50%. The results demonstrate the HSTEG system's potential to significantly improve PV panel efficiency and energy generation, offering a promising avenue for advancing solar energy technology. [ABSTRACT FROM AUTHOR]

Amidst the industrial transformation and upgrade, the new energy vehicle industry is at a crucial juncture. Power batteries, a vital component of new energy vehicles, are currently at the forefront of industry competition with a focus on technological innovation and performance enhancement. The operational temperature of a battery significantly impacts its efficiency, making the design of a reliable Thermal Management System (TMS) essential to ensure battery safety and stability. Cylindrical power batteries are widely utilized in the industry. This article outlines the four main structures and their drawbacks of TMS for cylindrical power batteries. Among these structures, air cooling falls short in meeting high heat dissipation requirements. Liquid cooling is expensive, intricate, and adds considerable weight. Phase Change Materials (PCM) are not yet prevalent in practical applications. Similarly, heat pipes are relatively uncommon in large high-power battery packs. To better align with the new energy vehicle industry's demands for top-notch performance, cost-effectiveness, eco-friendliness, and reliability, this paper strongly recommends delving deeper into composite cooling solutions. The construction of an economically viable and fully optimized composite cooling method is poised to become a significant scientific challenge for future research endeavors. [ABSTRACT FROM AUTHOR]

Microvascular materials containing internal microchannels are able to achieve multi-functionality by flowing different fluids through vasculature. Active cooling is one application to protect structural components and devices from thermal overload, which is critical to modern technology including electric vehicle battery packaging and solar panels on space probes. Creating thermally efficient vascular network designs requires state-of-the-art computational tools. Prior optimization schemes have only considered steady-state cooling, rendering a knowledge gap for time-varying heat transfer behavior. In this study, a transient topology optimization framework is presented to maximize the active-cooling performance and mitigate computational cost. Here, we optimize the channel layout so that coolant flowing within the vascular network can remove heat quickly and also provide a lower steady-state temperature. An objective function for this new transient formulation is proposed that minimizes the area beneath the average temperature versus time curve to simultaneously reduce the temperature and cooling time. The thermal response of the system is obtained through a transient Geometric Reduced Order Finite Element Model (GRO-FEM). The model is verified via a conjugate heat transfer simulation in commercial software and validated by an active-cooling experiment conducted on a 3D-printed microvascular metal. A transient sensitivity analysis is derived to provide the optimizer with analytical gradients of the objective function for further computational efficiency. Example problems are solved demonstrating the method’s ability to enhance cooling performance along with a comparison of transient versus steady-state optimization results. In this comparison, both the steady-state and transient frameworks delivered different designs with similar performance characteristics for the problems considered in this study. This latest computational framework provides a new thermal regulation toolbox for microvascular material designers. [ABSTRACT FROM AUTHOR]

Considering the substantial increase in deployment, photovoltaics are hovering to emerge as the predominant worldwide energy producer in the foreseeable future. Nevertheless, the operating efficiency and endurance of photovoltaic (PV) systems are significantly stalled by the heightened operating temperatures encountered by solar radiation. This article comprehensively analyzes novel active and passive PV cooling techniques, encompassing their operational mechanisms, cooling efficiency, and eventual implementations in solar devices. Extensive scholarly research has examined various PV cooling methods and techniques to optimize system cooling and efficiency. The primary goal of this effort is to compile a reference for future researchers and specialists by reviewing and comparing the results of current investigations. The study also comprised a bibliometric analysis that provides valuable insights into the influence of research on incorporating cooling systems into solar systems. These insights play a decisive role in recognizing new trends and progressing the field towards more efficient systems, hence advancing upcoming development. Furthermore, an extensive classification and assessment of every conceivable cooling technology was furnished to facilitate a comparison among diverse cooling methodologies. The research was structured in a tabular manner, containing the following details for each cooling technique: solar panel type, cooling method, cooling fluid or substance used, research category, average temperature reduction resulting from cooling, and enhanced electrical efficiency. The study indicates that cooling methods significantly enhance electrical efficiency, with potential increases varying from 0.28 % to 97.6 %. Additionally, this application is assessed to decrease the solar panel's operative temperature, ranging from 0.8 °C to 39.9 °C.

BackgroundWildland firefighters (WFFs) regularly face demanding physical and environmental conditions during their duties, such as high ambient temperatures, challenging terrains, heavy equipment and protective gear. These conditions can strain thermoregulatory responses, leading to increased fatigue and posing risks to their health and safety. This study examined the effectiveness of two cooling interventions during physical activity in hot environments.MethodsEight active male WFFs participated, comparing the effects of wearing a cooling vest (VEST) and personal protective equipment removal (PASSIVE) against a control condition (PPE). Participants walked on a treadmill at a speed of 6 km·h−1 for approximately 75-min under hot conditions (30°C and 30% relative humidity). Incremental slope increases were introduced every 15 min after the initial 20 min of activity, with 5-min passive recovery between each increment. Physiological and perceptual parameters were monitored throughout the protocol.ResultsSignificant main effects (p

In minimally invasive surgery, such as cardiac ablation, magnetically steered catheters made of variable‐stiffness materials can enable higher dexterity and higher force application to human tissue. However, the long transition time between soft and rigid states leads to a significant increase in procedure duration. Here, a fast‐response, multisegmented catheter is described for minimally invasive surgery made of variable‐stiffness thread (FRVST) that encapsulates a helical cooling channel. The rapid stiffness change in the FRVST, composed of a nontoxic shape memory polymer, is achieved by an active cooling system that pumps water through the helical channel. The FRVST displays a 66 times stiffness change and a 26 times transition enhancement compare with the noncooled version. The catheter allows for selective bending of each segment up to 127° in air and up to 76° in water under an 80 mT external magnetic field. The inner working channel can be used for cooling an ablation tip during a procedure and for information exchange via the deployment of wires or surgical tools. [ABSTRACT FROM AUTHOR]

Steady, continuous, and homogeneous cooling of photovoltaic panels that consume less energy for circulation of coolant is extremely important for preventing higher energy loses especially in hotter conditions. In this study, a novel steady continuous active cooling application with water, as the coolant, was applied in a compact photovoltaic/thermal hybrid system in order to find out the effects of coolant mass flow rate and to optimize the required amount of cooling for maximizing electrical efficiency by measuring the real load voltage and current values formed on the resistive load designed for the selected photovoltaic module. It is found that the reduction in panel temperature for the cooled panel can be accepted to be enough, especially for 31.38 kg/h coolant mass flow rate, since the operating temperatures of the cooled panel reached quite near to the ambient temperature. The means of the temperature reduction for cooled panels were between 13.06°C and 13.74°C as compared with the referent panel. The increase rate of average power for the cooled operations were in between 6-8%, while the instantaneous power increase, especially in midday periods, were reached to its highest values between 13% and 15% in comparison to the referent panel. The highest percent increase in power output was derived as 7.62% for the ṁ = 31.38 kg/h coolant mass flow rate at 12:30 pm. The highest daily cumulative electrical energy production was observed for the coolant mass flow rate of 39.66 kg/h, with 6.3% of increase. [ABSTRACT FROM AUTHOR]

The thermal error stability (STE) of the spindle seriously affects the machining accuracy of a machine tool, however existing empirical heating model-based active cooling strategies mainly focus on suppressing the spindle's overall thermal deformation and cannot effectively stabilize the thermal error. This study regards the "active cooling-spindle" system as a feedback control system and employs a data-driven thermal error model to provide feedback. Thus, the spindle thermal error can be stabilized for a long time owing to the homeostasis of the feedback control system under disturbance. A mechanical spindle with an external cooling scheme is taken as the study object. Bearings are the primary heat sources of the mechanical spindle; thus, the angular contact ball-bearing heat generation is precisely modeled based on local heat sources analysis of bearing components, elastohydrodynamic lubrication, and micro-contact theory. Thermal simulation of the spindle under varying-coolant temperature cooling is conducted to pre-validate the thermal error suppression and variation trend influencing effect, and obtain the Reference Input of Thermal Error (RITE) for the feedback control under different work conditions. Subsequently, a spindle thermal error feedback control system is developed, including computation, cooling, and real-time monitoring modules with inter-communication. Finally, the thermal error feedback control strategy is applied on the mechanical spindle, and experimental comparisons with constant coolant temperature cooling show that the thermal equilibrium time is advanced by 61.46%, 59.16%, 40.51%, and 58.08%. The thermal error variation range (TEVR) after the preheating stage is reduced to1.92, 1.52, 1.91, and 1.69 μm, respectively. The significant reduction in TEVR validated the effectiveness of the proposed strategy for spindle thermal error stabilization. [ABSTRACT FROM AUTHOR]

Solar energy has emerged as a standout alternative among the various types of renewable energies due to availability and minimal upfront expense in energy conversion. One of the most comprehensive methods to utilize solar energy potential is photovoltaic (PV) systems that apply a phenomenon called “photovoltaic effect”. However, one major obstacle to the widespread use of PV is their optimal working temperature. The PV performance is based on heat distribution on surface of the panel that need to be decreased. From previous literature reviews on PV cooling, it is found there's insufficient attention given to discussing the vital and standardized parameters necessary for evaluating the efficiency of cooling techniques for PV systems. Hence, in this article, several updated studies on PV cooling technology are discussed including passive, active and combined cooling. Besides that, the performance assessment methods are also elaborated including temperature-dependent PV efficiency difference factor (FTDED), temperature dependent photovoltaic power difference factor (FTDPD), PV power difference factor (FED), power ratio (R), PV cooler lifespan efficacy factor (FLSE), production cost effectiveness factor (FCE), modified production cost effectiveness factor (FMCE), and cost and area effectiveness factor (FCAE). It was found that the PV cooling has some major challenges to be addressed in future studies including cost, maintenance requirement, energy consumption especially for active cooling methods and performance under extreme conditions. Hence, recommendations are given for the purpose of tackling some of these challenges.

Solar energy is seen as a good option to replace fossil fuels in electricity generation. However, PV panels produce unnecessary heat energy during power generation which increases the temperature and affects the efficiency of PV cells. This article investigates the performance of PV modules using aluminum heat sinks and forced air cooling techniques. A cooling circuit configuration connecting a 6-inch pipe plenum with 5 T-shaped pipes is installed under the solar cell to provide better cold air distribution to the PV panels. The study was conducted on-site and in real-time conditions in a public hospital with high energy consumption as it operates continuously throughout the year. The combination of the two methods has optimized the performance of solar panels in terms of efficiency and electrical energy output. The average electrical efficiency of the studied PV panels is 17% and is very close to the PV module efficiency of 19.38% under standard test conditions (STC). The actual energy yield recorded for the installed PV panel is 12.35% higher than the estimated solar energy output under nominal operating cell temperature (NOCT) conditions. The results of the study show that solar energy generation can be optimized by considering the design, use of materials and proper cooling methods even when using the same solar panel.

Objectives. Postural imbalance can result from hyperthermia-mediated muscular fatigue and is a major factor contributing to injuries from falling. The objective of this study was to investigate the effect of exercise-induced hyperthermia and the impact of cooling on postural balance while wearing fire-fighters' protective clothing (FPC) in a hot environment. Methods. A portable force platform measured postural balance characterized by postural sway patterns using center of pressure metrics. Twelve healthy, physically fit males were recruited to stand on the force platform once with eyes open and once with eyes closed before and after treadmill exercise (40% ...O2max) inside an environmental chamber under hot and humid conditions (30 °C and 70% relative humidity) while wearing FPC. Subjects participated in two randomly assigned experimental phases: control and cooling intervention. Results. A significant increase in physiological responses and postural balance metrics was observed after exercising in the heat chamber while wearing FPC. Cooling resulted in a significant effect only on postural sway speed after exercise-induced hyperthermia. Conclusions. Hyperthermia can negatively alter postural balance metrics, which may lead to an increased likelihood of falling. The utilization of body cooling reduced the thermal strain but had limited impact on postural balance stability. [ABSTRACT FROM AUTHOR]

To solve the problem of high temperature thermal damages to the mine underground driving working face of a dry-hot-rock-enriched area, an active cooling method for fracturing water injection of the surrounding rock of the deep mine is proposed based on analysis of the heat dissipation mechanism of the surrounding rock. An artificial thermal reservoir is formed in the high temperature rock mass around the tunneling roadway by stimulation, such as a high pressure crack, and the heat energy of the surrounding rock is extracted by heat exchange of the heat-carrying fluid and the high temperature rocks mass to reduce the ambient temperature of the roadway. The design of a downhole water injection cooling system based on enhanced geothermal system technology is presented and a simplified enhanced geothermal system heats collection model is used for fluid-enclosure. Numerical simulation of the temperature field of the rock coupling shows that the temperature of the surrounding rock can be effectively reduced by increasing the water injection speed and fracture porosity, and improvement of the underground thermal environment can improve the working efficiency. For a water injection rate of 14 m/s and porosity of 0.18, the average cross-section temperature was 41.95 °C which is nearly 5 C lower than the original rock temperature of46.85 °C. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) has been widely used due to its advantages of low cost and high efficiency. However, one of the unsolved problems in WAAM is the heat accumulation. In this study, the compressed argon‐based interlayer active cooling (AC) process is employed to reduce heat accumulation, and the influence mechanism on microstructure and mechanical properties of Ti–6Al–4V samples are revealed. It is shown in the results that the introduction of interlayer AC leads to the interlayer temperature decreases from 468 to 53 °C, and the widths of prior‐β grains and αGB are refined. The increase of cooling rate (380–604 °C s−1) results in the transformation of large‐sized colonies into finer basket weave structure, accompanied by the production of martensite α'. The finer basket weave structure increases the strength of the samples, while the narrower αGB and the high‐angle grain boundaries increase the resistance of crack propagation. The high dislocation density caused by the faster cooling rate increases the plastic deformation to a certain extent. As a result, the interlayer AC improves the strength and plasticity of the samples simultaneously, the samples change from brittle and ductile‐mixed fracture to ductile fracture mode. [ABSTRACT FROM AUTHOR]

This figure shows the results from the CoolPINNs framework for forward and inverse problems. Heat is supplied to the bottom of the plate, and the top surface is free to convect and radiation. A flowing fluid through an embedded vasculature—in the shape of a sine wave—regulates the plate's temperature. The forward problem calculates the temperature field, whereas the inverse problem predicts thermal conductivity using noisy temperature data. [Display omitted] Emerging technologies like hypersonic aircraft, space exploration vehicles, and batteries avail fluid circulation in embedded microvasculatures for efficient thermal regulation. Modeling is vital during the design and operational phases of these engineered systems. However, many challenges exist in developing a modeling framework. What is lacking is an accurate framework that (i) captures sharp jumps in the thermal flux across complex vasculature layouts, (ii) deals with oblique derivatives (involving tangential and normal components), (iii) handles nonlinearity because of radiative heat transfer, (iv) provides a high-speed forecast for real-time monitoring, and (v) facilitates robust inverse modeling. This paper addresses these challenges by availing the power of physics-informed neural networks (PINNs). We develop a fast, reliable, and accurate Scientific Machine Learning (SciML) framework for vascular-based thermal regulation—called CoolPINNs: a PINNs-based modeling framework for active cooling. The proposed mesh-less framework elegantly overcomes all the mentioned challenges. The significance of the reported research is multi-fold. First , the framework is valuable for real-time monitoring of thermal regulatory systems because of rapid forecasting. Second , researchers can address complex thermoregulation designs since the approach is meshless. Finally , the framework facilitates systematic parameter identification and inverse modeling studies, perhaps the most significant utility of the current framework. [ABSTRACT FROM AUTHOR]

Abstract In minimally invasive surgery, such as cardiac ablation, magnetically steered catheters made of variable‐stiffness materials can enable higher dexterity and higher force application to human tissue. However, the long transition time between soft and rigid states leads to a significant increase in procedure duration. Here, a fast‐response, multisegmented catheter is described for minimally invasive surgery made of variable‐stiffness thread (FRVST) that encapsulates a helical cooling channel. The rapid stiffness change in the FRVST, composed of a nontoxic shape memory polymer, is achieved by an active cooling system that pumps water through the helical channel. The FRVST displays a 66 times stiffness change and a 26 times transition enhancement compare with the noncooled version. The catheter allows for selective bending of each segment up to 127° in air and up to 76° in water under an 80 mT external magnetic field. The inner working channel can be used for cooling an ablation tip during a procedure and for information exchange via the deployment of wires or surgical tools.

The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous indoor thermal conditions. This study performed a critical review on the state-of-the-art of cooling strategies, with special attention to their performance under heatwaves and power outages. We proposed a definition of resilient cooling and described four criteria for resilience—absorptive capacity, adaptive capacity, restorative capacity, and recovery speed —and used them to qualitatively evaluate the resilience of each strategy. The literature review and qualitative analyses show that to attain resilient cooling, the four resilience criteria should be considered in the design phase of a building or during the planning of retrofits. The building and relevant cooling system characteristics should be considered simultaneously to withstand extreme events. A combination of strategies with different resilience capacities, such as a passive envelope strategy coupled with a low-energy space-cooling solution, may be needed to obtain resilient cooling. Finally, a further direction for a quantitative assessment approach has been pointed out.

The transport of temperature-sensitive biological samples (blood, medicines, patient samples, vaccines, organs, etc.) to hard-to-reach places remains a challenge. This is especially true in places where infrastructure is limited, for which the use of unmanned aerial vehicles (UAVs) is an attractive solution. In this project, a cooling system compatible with on-board drone applications for the delivery of samples that require cold temperature storage and transportation was built, tested, and characterized. Specifically, a miniature polystyrene cooling unit with Peltier coolers was designed and built, enabling temperatures as low as −10 °C within the unit to be achieved. Further, passive and active cooling control strategies including the use of active feedback-control were explored to achieve a consistent temperature range between 2 °C and 8 °C. Finally, calculations of on-board power and battery weight required to achieve target cooling performance as a function of ambient environmental conditions are presented. Overall, this study presents an important step towards the design and development of drone-based technologies for temperature-sensitive sample delivery.

Among renewable resources, solar energy is abundant and cost effective. However, the efficiency and performance of photovoltaic panels (PVs) are adversely affected by the rise in the surface temperature of solar cells. This paper analyzes the idea of utilizing thermoelectric modules (TEMs) to enhance the efficiency and performance of PV panels. The proposed hybrid solar thermoelectric generation (HSTEG) system employs TEMs as thermoelectric coolers (TECs) to enhance panel efficiency and as thermoelectric generators (TEGs) to convert excess heat into additional electricity. This study includes an extensive evaluation of the proposed idea using MATLAB Simulink and experimental validation in indoor as well as outdoor environments. The use of TECs for the active cooling of the PV system leads to an increase in its efficiency by 9.54%. Similarly, the passive cooling by TECs along with the additional power generated by the TEGs from the excessive heat led to an increase in the efficiency of the PV system of 15.50%. The results demonstrate the HSTEG system’s potential to significantly improve PV panel efficiency and energy generation, offering a promising avenue for advancing solar energy technology.

Hydrocarbon fuels are promising energy sources and coolants for hypersonic vehicles. A clear understanding on the oxidation mechanism discrepancies of different cracked endothermic hydrocarbon fuels is essential for the performance and thermal management of hypersonic vehicles. Kinetic analyses on the pathway flux, sensitivity, and producing rate were performed to reveal the intrinsic relationships between the composition variation and laminar flame speeds of different pyrolysis products. A skeletal mechanism containing 68 species and 326 reactions was developed and validated by the targeted properties of the pyrolysis products. Analyses showed the flame speed discrepancies were resulted from the kinetic effect of the composition variations. The main oxidation pathways and consumption rates of the key intermediates were hardly changed with composition variation in the pyrolysis products. Sensitivity analyses found the flame speeds of pyrolysis products were mainly affected by the H/O/OH addition reactions of C0–C2 species. Their sensitivity coefficients were independent of the composition variations. Analyses on the rate of product (ROP) indicated the composition variation has a significant effect on the ROPs of H/O/OH radicals. Pyrolysis products including compositions of higher H/C ratios can produce higher contents of H, O, and OH radicals for the flame, resulting in higher laminar flame speeds.

Measurement while drilling (MWD) plays an important role in controlling well trajectory, improving drilling efficiency and saving drilling cost. In recent years, a large number of high-temperature wells have appeared, which makes the traditional MWD instruments no longer applicable. So far, no active cooling method has been successfully applied to MWD instruments for high-temperature oil and gas wells. This paper presents a new active cooling method for air drilling by utilizing the throttling and cooling of drilling gas, and the cooling system is designed. An axisymmetric numerical model of internal fluid is established, and different drilling gas flow channel design methods are discussed. The research results indicate that the wall temperature of the cooling section is much higher than the center fluid temperature, but lower than the ambient temperature, and can be used for active cooling of downhole drilling instruments. Compared with other design methods, the supersonic nozzle designed using the Bezier method has better parallelism of the gas in cooling section. The diffusion capability of straight wall diffuser is better than that of curved wall diffuser, and it can withstand greater back pressure. For straight wall diffuser, increasing the throat length and reducing the contraction and expansion angle can improve the diffusion capacity, but they also lead to a longer diffuser.

Simple Summary: Heat-related illness (HRI) is a potentially fatal disorder that can occur in dogs following exercise or exposure to hot environments. While many risk factors can affect the probability of HRI occurring, the priority for treating dogs with HRI is early and rapid reduction in their core body temperature to limit disease progression. Cold-water immersion (conductive cooling) and water spray with air movement (evaporative cooling) are the recommended treatments for dogs with HRI, with cooling attempts in dogs with HRI being strongly advised to take place prior to transportation for veterinary care. This retrospective study of cooling methods used in UK veterinary practices during 2016–2018 reports that just 21.70% of dogs were cooled prior to transport, and only 23.97% of dogs were cooled using the recommended methods between 2016 and 2018. These results highlight the need for clearer messaging to the public and to veterinary professionals on optimal management of dogs with HRI, with priority on promoting wider sharing of the advice to "cool first, transport second". The management of heat-related illness (HRI) in dogs has received limited attention in the veterinary literature, especially regarding effective cooling methods. Guidelines published in 2016 for prehospital management of dogs with HRI advised "cool first, transport second", and recommended using cold-water immersion and evaporative cooling (water application with air movement) as the optimal approaches to reduce the patient's temperature. The current retrospective cross-sectional observation study analysed electronic patient records from the VetCompass programme to describe the cooling methods used in dogs with HRI presented to primary care veterinary practices during 2016–2018. Of 623 HRI events identified, 341 (54.74%, 95% CI 50.81–58.60%) included information on cooling in their clinical record. Of these, 74/341 (21.70%, 95% CI 17.65–26.38%) were cooled prior to transport for veterinary care. Overall, 23.97% (95% CI 19.24–29.44%) were cooled using one of the two recommended cooling methods, whilst the most common cooling method recorded was the application of wet towels (51.31%, 95% CI 45.34–57.24%). Canine cooling guidance and messaging in both the public and veterinary sectors requires urgent review to ensure that the most effective cooling methods are promoted because delays to canine temperature reduction worsen patient outcomes. [ABSTRACT FROM AUTHOR]

Cooling enhances the energy conversion efficiency and output of photovoltaic (PV) panels. In this work, the effects of natural convection, forced convection, and evaporative cooling on the performance of polycrystalline PV panels were investigated. The output and efficiency of a cooled PV panel were monitored and compared to those of an uncooled PV panel under the same conditions. The cooling was conducted using an insulated channel installed below a PV panel. Natural convection cooling was investigated for various channel air gaps (H = 30, 60, 90, and 120 mm). Natural convection currents in the cooling channels were capable of cooling the panel with wide air gaps. In forced convection cooling, the air was introduced by fans installed at the bottom opening of the cooling channel with various air velocities (ua = 1, 2, and 3 m/s). Evaporative natural convection cooling was performed by a wetted fabric along the lower surface of the cooling channel, whereas evaporative forced convection cooling by pushing air along the wetted lower surface of the channel. The experimental data showed that the panel efficiency and output increased due to cooling. The experimental results of natural convection cooling revealed that the use of an air gap of 120 mm to cool the solar panel contributed to an increase in the panel daily energy production and efficiency by 1.7% and 1.2%, respectively. For forced convection cooling, using air at a speed of 3 m/s increased the daily energy production by 4.4% and the efficiency by 4%. Natural convection evaporative cooling increased the daily energy production and the efficiency by 3.6% and 2.7%, respectively. Forced convection evaporative cooling contributed, at a speed of 2 m/s, to an increase in the daily energy production by 3.8% and an increase in efficiency of 3.8%.

A photovoltaic (PV) cell is very sensitive to temperature changes where decreasing temperature plays the main role in the increase of PV electrical efficiency and output power. Therefore, researchers used different techniques for cooling PV modules to avoid immoderate heating PV modules and to decrease the panel temperature, resulting in raising power output, energy efficiency, performance, and life of the panel. In the present work, PV panels are cooled by forced convection. Cooling airflow characteristics and panel temperature distribution are examined using computational fluid dynamics (CFD). In order to evaluate CFD predictions, experimental measurements are obtained in a sunny day on 23rd September 2021 for the period from 10 AM to 4 PM. The experimental measurements are performed on three different arrangements of PV panels. The uncooled panel was considered as the reference case. Two different cooling methods were examined: PV panels with forced air-cooling using a lower duct and supplying air using the blower, and PV panels with forced air-cooling using small fans arranged symmetrically on the backside of the PV panels. The temperatures determined by the CFD calculations are compared to the experimentally measured temperatures and it was found to be in good agreement. The results showed that cooling PV using small backside fans can enhance the performance and achieve a maximum total increase of 2.1% in PV panel efficiency with 7.9% saving energy. Using the blower cooling technique achieves a maximum total increase of 1.34% in PV panel efficiency with 4.2% saving energy.

• A novel structure for the active pressure management of a storage tank is proposed. • The evolutions of temperature and flow during the whole process are illustrated. • A heat-pipe-like and a redistributor work mode are uncovered in different zones. Inevitable evaporation process occurring in liquid hydrogen storage may bring about safety risks associated with over-pressure and hydrogen discharge. Using a cryogenic refrigerator to compensate for the heat leakage is expected to eliminate the risk of hydrogen vent, realizing long-term lossless storage. Presently, active lossless storage technology applied on civil fields has rarely been studied. This paper presents a numerical study on the dynamic evolution process within an active cooling system of a liquid hydrogen tank. The accuracy of the model is validated with an average deviation of 0.47%. During the self-pressurized process, the maximum temperature difference is more than 26 K in the ullage zone. After cooling capacity being introduced, a three-stage depressurization process appears. Minor cooling capacity that is less than heat leakage can still realize pressure management. Further analyses show two operating modes similar to gravity heat pipes and thermal redistributors occurring in the ullage and the liquid zone, respectively. This work suggests the effectiveness of active cooling on controlling the ullage pressure, which may be applicable to future hydrogen refueling stations and intercity hydrogen transportation. [ABSTRACT FROM AUTHOR]

Thermoelectric energy conversion based on flexible materials has great potential for applications in the fields of low-power heat harvesting and solid-state cooling. Here, we show that three-dimensional networks of interconnected ferromagnetic metal nanowires embedded in a polymer film are effective flexible materials as active Peltier coolers. Thermocouples based on Co-Fe nanowires exhibit much higher power factors and thermal conductivities near room temperature than other existing flexible thermoelectric systems, with a power factor for Co-Fe nanowire-based thermocouples of about 4.7 mW/K 2 m at room temperature. The effective thermal conductance of our device can be strongly and rapidly increased by active Peltier-induced heat flow, especially for small temperature differences. Our investigation represents a significant advance in the fabrication of lightweight flexible thermoelectric devices, and it offers great potential for the dynamic thermal management of hot spots on complex surfaces. [ABSTRACT FROM AUTHOR]

Plate structures with active cooling are widely used, and rapid evaluation of the temperature performance is of interest. In this paper, an analytical model is proposed for the prediction of maximum temperature and temperature distribution of plate structures with active cooling channel. The analytical model has three types of input parameters including thermal boundary conditions, material properties, and geometry parameters. Solution procedures under different thermal boundary conditions, including heat flux and convective heat transfer, are discussed respectively. The model with heat flux boundary (MHF) is established based on the principle of energy conservation. The model with convective heat transfer boundary (MCHT) is established based on the method of second-order function fitting the real heat flux distribution. The materials of the plate structures are aluminum alloy and titanium alloy. The results show that the analytical model is able to predict the maximum temperature with an error of less than 4% compared to the numerical method. The analytical model is able to quickly and accurately evaluate the thermal protection performance of the active cooling structure. [ABSTRACT FROM AUTHOR]

Overcoming the issue of photovoltaic (PV) module productivity at high temperatures is one of the most critical obstacles facing its use. PV cells are made of silicon, which loses its properties at high temperatures, degrading the PV module work. The present research compares cotton wicks integrated with rectangular aluminium fins (CWIRAFs) submerged in water as passive cooling with an absorbing plate and copper pipes attached at the PV module backside as active cooling. Compared with the PV module without cooling, CWIRAFs have better performance with the PV module than active cooling owing to evaporative cooling and increased heat dissipation area represented by wet cotton bristles integrated. The PV module is exposed to significant performance degradation without cooling in hot climate conditions. As a result, using CWIRAFs with the PV module had reduced the temperature by 31.4%, increased the power by up to 66.6%, and increased the electrical efficiency from 3.12 to 8.6%. Active cooling methods have reduced the PV temperature by 20.8%, increased the power by 56.7%, and enhanced electrical efficiency by 7.9%. Removing excess heat from the backside of the PV module via circulating water has improved the thermal efficiency and overall efficiency of the PVT system by about 26.3 and 34.2%, respectively. [ABSTRACT FROM AUTHOR]

The active cooling technology that can reduce the combustor temperature is commonly used to protect the scramjet. In order to further improve the performance of active cooling, the structural weight reduction, cooling efficiency and stress level of the cooling channel must be considered simultaneously. In this paper, new types of lattice channels for active cooling were designed and compared with the conventional cooling channel in terms of weight reduction, thermal and structural performance. The results showed that, at the same channel height, the cooling channel with staggered lattice arrays has the optimal comprehensive performance: the weight reduction effect reaches 39.93%; the wall temperature drops significantly, and the maximum Nu number is 2.155 times of the conventional channel. The flow field analysis showed that horseshoe vortices formed by the impact effect and hairpin vortices near the trailing edge are the main factors of heat transfer enhancement. The disturbed boundary layer and the excited turbulent kinetic energy also contribute much to enhance the heat transfer. In addition, due to the HTE-induced increment of metal tensile strength, the system reliability of lattice channel is better than the conventional one. [ABSTRACT FROM AUTHOR]

The current paper aims to present a cooling concept for future centralized platforms of ECUs (Electronic Control Units) from the automotive industry that involves grouping multiple electronic devices into a single system and cooling them with forced convection dielectric coolant. The enhancement consists of replacing the inside air of the module with a dielectric coolant that has a higher thermal conductivity than air and employing an additional prototype system that aids in forced liquid cooling. To meet automotive requirements, the experiments were exposed to an ambient temperature of 85 °C. Temperature measurements on these solutions' hot spots were compared to those on a thermal paste-only reference electronic module. This study used DFSS (Design for Six Sigma) techniques to determine the ideal pump flow rate, fan air flow rate, and liquid volume in the housing, leading to an optimization in heat dissipation. Finding a trustworthy transfer function that could forecast the impact of the crucial design parameters that had been found was the main goal. The electronics cooled by forced convection coolant improved heat dissipation by up to 60% when compared to the reference module. This demonstrates that the DoE (Design of Experiments) method, which is based on a limited number of measurements, can estimate the behavior of the ECU without the need for a more involved theoretical framework. [ABSTRACT FROM AUTHOR]

Solar cells lose efficiency as the operating temperature increases under normal operating conditions, resulting in a very significant power output reduction. This issue is most relevant in areas with the highest photovoltaic energy harvesting potential, where irradiance and ambient temperature are particularly high. A novel cooling system for commercial photovoltaic modules based on low-enthalpy geothermal cooling is proposed in this paper. Excess heat is evacuated from the solar module in a clean and efficient manner by a single-phase and close-loop cooling circuit that uses the underground as a natural heatsink. In addition, a thermoelectrical theoretical model is presented, that allows the optimization of the flowrate and the maximization of the extra power generation of the cooled module. A prototype was manufactured and tested in outdoor conditions in September 2021 in Spain. Test results are in good agreement with the theoretical model, which has been used for prediction of the performance of the system for a typical meteorological year in the region. A peak efficiency improvement of 10.7% is calculated for the month of July, with an optimal flowrate of 1.8 l/min per square meter of solar module. A yearly weighted average power gain of up to 4.9% is also calculated. [ABSTRACT FROM AUTHOR]

Overall, a rapid increase in the thermal error of the spindle can seriously deteriorate the machining accuracy of the machine tool. A closed-loop thermal error control system was presented to stabilize the thermal error in machining processes. The closed-loop system employed an active cooling system as the actuator and relies on a thermal error model to provide feedback. Thermal measurements of the spindle can be severely disturbed by the temperature-varying coolant recirculation, leading to the invalidity of the data-driven regression models. A physical-based model that can accurately reflect the combined effect of the cooling and heating sources was established via a thermal resistance-capacity network. A modified AdaBoost framework with a statistics-based weights updating mechanism was used to train physical-based models and ensemble them into an optimal model, which is translucent to be empirically supervised. Through thermal testing experiments, it was shown that the physical-based ensemble model provided satisfactory feedback for the closed-loop control system, where the thermal error variation ranges were less than 1.5 μm throughout the experimental processes. Furthermore, employing the proposed closed-loop control system and with the use of the physical-based ensemble model, the total machining error was reduced by 70.33% compared to that of the constant temperature cooling. The study findings demonstrate that the method of closed-loop spindle thermal error control employing the physical-based ensemble model is effective and feasible for enhancing machining accuracy. [ABSTRACT FROM AUTHOR]

A photovoltaic (PV) cell is very sensitive to temperature changes where decreasing temperature plays the main role in the increase of PV electrical efficiency and output power. Therefore, researchers used different techniques for cooling PV modules to avoid immoderate heating PV modules and to decrease the panel temperature, resulting in raising power output, energy efficiency, performance, and life of the panel. In the present work, PV panels are cooled by forced convection. Cooling airflow characteristics and panel temperature distribution are examined using computational fluid dynamics (CFD). In order to evaluate CFD predictions, experimental measurements are obtained in a sunny day on 23rd September 2021 for the period from 10 AM to 4 PM. The experimental measurements are performed on three different arrangements of PV panels. The uncooled panel was considered as the reference case. Two different cooling methods were examined: PV panels with forced air-cooling using a lower duct and supplying air using the blower, and PV panels with forced air-cooling using small fans arranged symmetrically on the backside of the PV panels. The temperatures determined by the CFD calculations are compared to the experimentally measured temperatures and it was found to be in good agreement. The results showed that cooling PV using small backside fans can enhance the performance and achieve a maximum total increase of 2.1% in PV panel efficiency with 7.9% saving energy. Using the blower cooling technique achieves a maximum total increase of 1.34% in PV panel efficiency with 4.2% saving energy. [ABSTRACT FROM AUTHOR]

Cooling enhances the energy conversion efficiency and output of photovoltaic (PV) panels. In this work, the effects of natural convection, forced convection, and evaporative cooling on the performance of polycrystalline PV panels were investigated. The output and efficiency of a cooled PV panel were monitored and compared to those of an uncooled PV panel under the same conditions. The cooling was conducted using an insulated channel installed below a PV panel. Natural convection cooling was investigated for various channel air gaps (H = 30, 60, 90, and 120 mm). Natural convection currents in the cooling channels were capable of cooling the panel with wide air gaps. In forced convection cooling, the air was introduced by fans installed at the bottom opening of the cooling channel with various air velocities (u a = 1, 2, and 3 m/s). Evaporative natural convection cooling was performed by a wetted fabric along the lower surface of the cooling channel, whereas evaporative forced convection cooling by pushing air along the wetted lower surface of the channel. The experimental data showed that the panel efficiency and output increased due to cooling. The experimental results of natural convection cooling revealed that the use of an air gap of 120 mm to cool the solar panel contributed to an increase in the panel daily energy production and efficiency by 1.7% and 1.2%, respectively. For forced convection cooling, using air at a speed of 3 m/s increased the daily energy production by 4.4% and the efficiency by 4%. Natural convection evaporative cooling increased the daily energy production and the efficiency by 3.6% and 2.7%, respectively. Forced convection evaporative cooling contributed, at a speed of 2 m/s, to an increase in the daily energy production by 3.8% and an increase in efficiency of 3.8%. [ABSTRACT FROM AUTHOR]

Wire arc additive manufacturing (WAAM) allows for quick, large component manufacturing with fast deposition rates while leveraging readily available wire feedstock that is significantly cheaper than metal powder. However, the increased deposition rate of this process requires enhanced thermal management as failures can occur due to overheating. A common strategy to mitigate overheating is to dwell, or pause, between individual layers; however, this can significantly increase build times and eliminate the advantage of additive manufacturing being able to manufacture components quickly. To help mitigate this issue, this study explores the use of active cooling to maintain process control and to decrease overall build time. Conductive cooling applied to either the bottom or side of the print substrate was explored. Results from this study showed that bottom build plate active cooling can be used to decrease dwell times by up to 50% and decrease cool-down to room temperature after the building process by up to 75%. Results from this study demonstrate that the use of active cooling strategies for WAAM can be used for better thermal control over the process and should be further investigated. [ABSTRACT FROM AUTHOR]

Aim The study aimed to determine the current status of face mask use, deep body temperature measurement, and active cooling in patients suffering from heat stroke and heat exhaustion in Japan. Methods This was a prospective, observational, multicenter study using data from the Heatstroke STUDY 2020–2021, a nationwide periodical registry of heat stroke and heat exhaustion patients. Based on the Bouchama heatstroke criteria, we classified the patients into two groups: severe and mild‐to‐moderate. We compared the outcomes between the two groups and reclassified them into two subgroups according to the severity of the illness, deep body temperature measurements, and face mask use. Cramer's V was used to determine the effect sizes for a comparison between groups. Results Almost all patients in this study were categorized as having degree III based on the Japanese Association for Acute Medicine heatstroke criteria (JAAM‐HS). However, the severe group was significantly worse than the mild‐to‐moderate group in outcomes like in‐hospital death and modified Rankin Scale scores, when discharged. Heat strokes had significantly higher rates of active cooling and lower mortality rates than heat stroke‐like illnesses. Patients using face masks often use them during labor, sports, and other exertions, had less severe conditions, and were less likely to be young male individuals. Conclusions It is suggested that severe cases require a more detailed classification of degree III in the JAAM‐HS criteria, and not measuring deep body temperature could have been a factor in the nonperformance of active cooling and worse outcomes.

Omni-directional magnetic field generators (or Omnimagnets) are devices with several potential applications, such as capsule endoscope and magnetic guidance of a cochlear implant. An Omnimagnet heats due to the Joule effect and the resulting excessive temperatures may cause device failure. Thermal analysis of an Omnimagnet can provide operational limits to prevent device failure due to excessive heating; however, as the device is still new, the thermal performance of the Omnimagnet has not yet been completely studied. The thermal behaviour of two Omnimagnets with some structural differences are numerically and experimentally studied in this work. A lumped-capacitance model is validated with experimental results showing the model Normal Root Mean Square Error for both Omnimagnets to be less than 12 % . Results show that increasing the size of the Omnimagnet by about 16 % , slows the rate of temperature increase within the Omnimagnet by 44 % . In addition, a constant frame temperature heat sink at 0 ∘ C decreases the steady-state temperature of the outer solenoid by approximately 29 % when the outer solenoid is powered at 10 A. [ABSTRACT FROM AUTHOR]

In recent years, global automotive industries are going through a significant revolution from traditional internal combustion engine vehicles (ICEVs) to electric vehicles (EVs) for CO2 emission reduction. Very similarly, the aviation industry is developing towards more electric aircraft (MEA) in response to the reduction in global CO2 emission. To promote this technology revolution and performance advancement, plenty of electronic devices with high heat flux are implemented on board automobiles and aircraft. To cope with the thermal challenges of electronics, in addition to developing wide bandgap (WBG) semiconductors with satisfactory electric and thermal performance, providing proper thermal management solutions may be a much more cost-effective way at present. This paper provides an overview of the thermal management technologies for electronics used in automobiles and aircraft. Meanwhile, the active methods include forced air cooling, indirect contact cold plate cooling, direct contact baseplate cooling, jet impingement, spray cooling, and so on. The passive methods include the use of various heat pipes and PCMs. The features, thermal performance, and development tendency of these active and passive thermal management technologies are reviewed in detail. Moreover, the environmental influences introduced by vibrations, shock, acceleration, and so on, on the thermal performance and reliability of the TMS are specially emphasized and discussed in detail, which are usually neglected in normal operating conditions. Eventually, the possible future directions are discussed, aiming to serve as a reference guide for engineers and promote the advancement of the next-generation electronics TMS in automobile and aircraft applications. [ABSTRACT FROM AUTHOR]

The present work provides an overview on an additive manufacturing (AM) design case of a novel battery cell lid structure (patent pending) for electrical vehicle applications. The benefits of AM have not yet been explored on metal case structures of prismatic battery cells. The method allows the manufacturing of complex hollow structures and integration of multiple functions in one part. The main challenge is to address thermal management in an optimal location in the battery cell. More efficient charging and discharging by maintaining the batteries at optimum operating conditions allows a longer battery lifetime. Recent research shows that elevating the charging temperature enables significantly shorter charging times. The aim of this study is to develop a lid structure to support higher peak current, faster charging, and reduced production steps and enable mass customization. The optimum performance simulated with computational fluid dynamics calculations is realized to determine the optimum design. The design case study is verified via laser powder bed fusion prototypes. This study shows that it is possible to produce integrated thermal management liquid channels to the battery lid. Significant improvement is achieved with localized battery cell temperature management. The novel design integrates six critical functionalities of the lid in one part. The design of the features is optimized to avoid support structures in AM and to maximize the number of parts in the printing chamber volume. The better thermal management extends the driving range of the vehicle and improves vehicle safety. Reducing the parts significantly simplifies cell production. [ABSTRACT FROM AUTHOR]

Enhancing the cold load/storage (CLS) functional cemented paste backfill (CPB) technological cooling effect is crucial given the deep mine escalating heat damage. Single optimization schemes such interval boards insulation, higher emissivity, active cooling, and integrated optimization schemes of the aforementioned measures are suggested in order to improve the cooling impact of CLS functional CPB. Firstly, active cooling was implemented to isolate the heat source and protect the cooling capacity. Experiments indicate that this approach can extend the period of time that the stope temperature is maintained below the temperature threshold. Secondly, thermal insulation material is applied to the interval boards of the stope and the CLS functional CPB to decelerate the cooling transfer rate. When the stope temperature reaches the recommended upper limit, remove the insulation material. The results show that 1 mm insulation material is the most economical and environmentally friendly option. However, when the temperature difference inside the backfill is slight, the effect of the radiation coating is not significant. The best-optimized cooling method obtained in this paper is to take active cooling around the stope and CLS functional CPB, and then paste 1 mm insulation material on the interval boards. • Multi-scheme comparison and optimization. • An experimental platform was established to verify the numerical simulation results. • CFD numerical simulation is used to obtain the temperature distribution. • Multi-angle study of cold source and heat transfer process. [ABSTRACT FROM AUTHOR]