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Elastocaloric cooling is emerging as a promising alternative to conventional vapor compression systems due to its potential for energy savings and significant temperature lift compared to other solid-state cooling technologies. This technology harnesses the latent heat associated with the martensitic phase transition of shape memory alloys to generate the desired cooling or heating effect. This paper comprehensively reviews the fundamentals of elastocaloric cooling systems, including the thermodynamics cycle and various materials used. It also presents the latest advancements in elastocaloric systems, focusing on heat transfer enhancement, actuator development, and prototype summaries. Additionally, this paper introduces a new non-dimensional performance parameter to evaluate different elastocaloric prototypes and discusses key aspects necessary to achieve potentially high-performance elastocaloric devices. Finally, we propose an approach for future elastocaloric device development. [ABSTRACT FROM AUTHOR]

The focus of this paper is to investigate the practicality of incorporating immersion cooling methods to mitigate the temperature elevation of motors utilized in hybrid aircraft. Air cooling, oil jacket cooling, slot-channel oil cooling and immersion cooling techniques are each applied to a permanent magnet synchronous motor. When a hybrid aircraft is operating, the amount of fuel it carries is limited and decreases over time. In this case, the normal operating time of the motor is investigated in this paper. The study shows that for the motors in this paper, immersion cooling is the most effective with a limited amount of coolant and takes the longest time to reach the upper temperature limit, which can be improved by 5.6 times compared to slot-channel cooling. This paper serves as a reference for the design of motors for hybrid aircraft utilizing immersion cooling technology. [ABSTRACT FROM AUTHOR]

Challenges in drilling nickel-based superalloys, such as Inconel 718 (IN718), are multifaceted. High requirement of hole surface quality in drilling such alloy must deal with extreme material properties and complex process condition in drilling operation. This paper presents an experimental investigation on the effect of PVD coated solid carbide drills under different internal cooling schemes on hole quality in drilling IN 718 alloy. Three types of solid carbide drills were used in the series of drilling experiments, including PVD coated and uncoated drills, and different design in the number of internal cooling channels, two channels and four channels. The objective of the investigation is to assess the effect of coating and efficiency of internal cooling on surface quality in drilling IN718 alloy. Surface quality on drilled holes in terms of roughness, burr formation, subsurface deformation and strain hardening has also been measured and analyzed on the machined specimen. The roughness and burr size on drilled holes demonstrated little differences among the three types of testing drills. Surface roughness was severely deteriorated by the chip trapped in the hole leaving scratch and smears on the surface. Nevertheless, the scheme of internal cooling channels and PVD coating exhibited noticeable influence on quality of drilled hole surface. [ABSTRACT FROM AUTHOR]

Zirconolite (CaZrTi 2 O 7) glass-ceramic is considered as a potential stable matrix for the immobilization of Pu or minor actinides (Np, Am, Cm). In this work, the phase combination and evolution of glass (SiO 2 –Al 2 O 3 –Na 2 O–CaO–ZrO 2 –TiO 2 –B 2 O 3) with La as an actinide surrogate were investigated during the process of heating and cooling. By employing controlled cooling process, the zirconolite glass-ceramic with a controllable crystal size was successfully fabricated in borosilicate glass. The results demonstrate that heating and cooling exhibit distinct phase combinations. Both crystallization temperature and duration exert a significant influence on the composition of crystalline phases and microstructure. During the cooling of the melt, an increased degree of supercooling leads to an enhanced crystallization of zirconolite and a significant reduction in crystal size. The experimental results demonstrate that the optimal condition for preparing zirconolite glass-ceramic is held at 950 °C, for 4 h by one-step method, at which time the crystal exhibits a slender acicular morphology with a size of about 30 μm. Most of the simulated nuclides are enriched in crystals, and the rest are dissolved in glass. Zirconolite exhibits thermodynamic instability at elevated temperatures (1000 °C–1100 °C). Following the phase transformation, a proportion of Zr sequestered by titanite, while any excess Zr is either remain dissolved in the glass or gets precipitated as baddeleyite. For La, Al and other elements previously fixed in zirconolite, they are re-released to the glass and partially fixed by titanite, which may be detrimental to the long-term release behavior of the waste forms. In the aqueous durability test, both zirconolite glass-ceramic and phase transformation samples exhibited a low leaching rate, with LR Si , LR Zr , and LR La values of approximately 5 × 10−3, 4 × 10−6, and 6 × 10−6 g·m−2·d−1, respectively, after 28 days of leaching. By controlling the cooling process (one-step method), this paper provides useful information on the preparation of zirconolite glass-ceramic. [ABSTRACT FROM AUTHOR]

This paper presents a promising solution to superheat of stratospheric airship with radiative cooling envelope, which has no change in pneumatic profile, structural weight, and power consumption. In this study, a multilayer nanoparticle-polymer metamaterial (MNPM) is hierarchically designed to provide reflectivity across visible wavelength and emissivity in atmospheric window. In this paper, the specimens and ball models are firstly fabricated, the cooling performances of which are tested for ground experiments. The temperatures of MNPM and silica/Ag specimens are 6.7 °C and 10.8 °C at noon in Tianjin. The inner gas and surface temperatures of MNPM scale ball are 11.7 °C and 14.6 °C, lower than silica/Ag by 4.5 °C and 4.6 °C, respectively. Subsequently, the flight experiments verify the cooling performance of MNPM, the maximum temperature of which is lower than the control group by 15.4 °C in stratosphere. Finally, the FLUENT simulations illustrate the cooling performance of stratospheric balloon and airship equipped with solar panel. The MNPM has a better cooling capacity for the internal helium and top surface throughout the day and a weak warming capacity for the bottom surface at night. Considering solar panels, the MNPM reduces the helium temperature by 8.1 °C, and the day-night superheat of the helium temperature is only 19.8 °C. [ABSTRACT FROM AUTHOR]

• To improve data center performance, it must be efficiently cooled. • This paper undertakes a detailed examination of the most recent cooling optimization techniques. • Several methods are discussed like regular air conditioning, free cooling, and liquid cooling. • An assessment of overhead and underfloor air delivery technologies is presented. • The effects of baffles, variable airflow control, and server placement are investigated. In order to increase data centers' efficiency and performance, a proper cooling system should be applied. This article provides a comprehensive assessment which explores current cooling optimization technologies for data centers. Standard traditional technologies like air conditioning, free cooling, and liquid cooling are investigated. Their limitations as well as proposed improvements are thoroughly discussed. The article also delves into underfloor and overhead air supply technologies, presenting their advantages and drawbacks. The review introduces novel approaches at the rack level cooling, including baffles, variable airflow management, and optimal server placement. Key findings stress the efficacy of optimized airflow systems and innovative rack-level cooling, underlining their role in reducing energy consumption and enhancing overall performance. Notably, potential energy savings of up to 67.2 % compared to traditional methods are demonstrated. The adoption of advanced cooling technologies, such as direct and indirect natural cooling, liquid-cooling cold plates, submersion, heat pipe, and thermosiphon-based cooling, exhibits promising energy efficiency gains and reduced Power Usage Effectiveness (PUE) values. Research into content-specific efficiency enhancements, adaptable energy-saving tactics, and all-encompassing server power consumption models is necessary. To work toward future sustainable, energy-efficient data centers, researchers should investigate how CRACs and server fans interact, find ways to integrate thermal and power management, and how artificial intelligence can be used to cool servers in an eco-friendly way. [ABSTRACT FROM AUTHOR]

The internal coolant supply (ICS) allows a cooling lubricant to be used efficiently in terms of quantity and application. Especially in processes in which access to the cutting zone is impeded by the workpiece and the tool, an ICS can deliver cooling lubricant to the cutting zone. While an ICS has already been successfully implemented in numerous machining processes, there is a lack of fundamental research regarding its use in circular sawing. In this paper, an analysis of an ICS in circular sawing is presented. It showed that an ICS with a significantly reduced amount of coolant improved the thermal tool load, the chip form as well as the workpiece surface quality. [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]

In this paper, we utilized a eutectic gallium-indium liquid metal (LM) with high thermal conductivity to immerse carbon-based phase change material (PCM) capsules to acquire a PCM-LM composite. This produced a scalable, thermally stable, mechanically reliable, high thermally conductive, and leakage-free material. This composite was then applied as a heat mitigator for CPU cooling. Results demonstrate that clear improvements could be made compared to traditional pin-fin heat-sink cooling. Here the continuous full-load operating time could be prolonged by 414.3%. Moreover, the temperature difference between the idle and full-load operating states could be significantly decreased, and prevent damage from thermal stress. Significantly, a 23% energy-saving performance was attained because of the thermal buffering effect and high responsive ability of the composite. Guidelines for an effective match between the heat absorption of the composite and the heat generation from the CPU could also be established. Here the proposed PCM-LM composite can be applied to other PCM-based energy storage industries and efficient temperature control applications, contributing to carbon neutralization and global warming mitigation. [ABSTRACT FROM AUTHOR]

The map of radiative cooling potential shows that the radiative cooling power can reach up to 100 W/m2 for its application in different climatic zones. However, the effect of building deployment on the city-scale application of radiative cooling is generally ignored in majority of existing studies, which overestimates the cooling benefit. This paper investigates the cooling benefit of implementing radiative cooling on a city-scale by considering building deployment. To determine the effect of building deployment on the radiative cooling potential, the city of Xi'an in China is modeled using COMSOL and verified with real weather data. Then, the thermal response of buildings with radiative cooling envelopes is discussed in detail. Finally, carbon emission reduction is derived at the city-scale by applying radiative cooling considering building deployment. The results show that the estimated radiative cooling power is approximately decreased by 14.7% for the ideal broadband surface and 47.1% for the ideal selective surface on the selected day by considering building deployment on a city-scale. Furthermore, carbon emission reductions of 0.52 gCO 2 /(m2⋅h) and 0.16 gCO 2 /(m2⋅h) can be achieved from the roof and walls on the selected day by applying radiative cooling material on both the roof and walls. This study can provide guiding significance for the large-scale application of radiative cooling in cities. [ABSTRACT FROM AUTHOR]

• 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]

Designing components for thermo-mechanical loads is a challenging process. While mechanical loads like forces or pressure demand a stiff and thick-walled design, thermal loads create temperature gradients, resulting in thermo-mechanical stress from the structure's temperature proportional and, therefore, uneven expansion. In contrast to a pure mechanical load case, an initial design before optimization can already include stress levels beyond the limit of the material. Therefore, common optimization approaches for a preliminary design use exemplary systems with low-temperature gradients, so thermal stresses do not exceed the limit. From there, energy density is used to calculate the topology optimizations sensitivity and therefore decide which elements to remove and which to keep. This paper describes a novel approach for reducing thermo-mechanical stress by following the stress corresponding temperature gradients from the heat source to the sink to calculate a new sensitivity that helps to grow cooling channels. The optimization is exemplarily shown on a piston for internal combustion engines. While handling delta temperatures of 600K, results show a reduction in thermo-mechanical stress while reducing the component's mass. Because the approach reduces critical stress in a component, it allows the initial design (before the topology optimization) to have stress levels way above yield strength. [ABSTRACT FROM AUTHOR]

• Thermohydraulic characteristics of microchannel direct liquid cooling were studied. • The influence of axial thermal conduction was considered. • The influence factors of wall temperature uniformity were analyzed. • Effect of swing on thermohydraulic characteristics of microchannels was studied. • Performance factor was defined to evaluate microchannel comprehensive performance. In this paper, the thermohydraulic characteristics of direct liquid cooling in rectangular microchannels were studied under swing condition. Deionized water was used as the coolant. The effects of coolant flow rate, coolant inlet temperature, microchannel equivalent diameter and heating power on the thermohydraulic performances were studied. In addition, the wall temperature uniformity and axial heat conduction effect were discussed. Furthermore, the influence of swing speed on the performances of microchannel direct liquid cooling was studied. The performance factor was defined to evaluate the microchannel comprehensive thermohydraulic performance. The results show that the transition Reynolds number of microchannels with equivalent diameters of 0.9–1.6 mm is between 500 and 2000. The wall temperature uniformity is improved with the increase of coolant flow and the decrease of coolant inlet temperature. The axial heat conduction demonstrates a great influence on the microchannels, which accounts for about 40%-50% to the total heat. With the increase of swing speed, the drag coefficient decreases slowly within 4%. Meanwhile, the flow rate should be in 0.14–0.2 L/min to obtain an optimal effect of the performance factor. [ABSTRACT FROM AUTHOR]

In metal cutting processes, the use of cutting fluids shows significant effects on workpiece surface quality by reducing thermo-mechanical loads on cutting tool and workpiece. The effect of the coolant on the workpiece temperature is difficult to determine experimentally due to the limited accessibility of the process. To overcome the experimental limitations and quantify the cooling effect, a coupling approach has been developed that combines chip formation simulation using finite element method (FEM) and cutting fluid simulation using computational fluid dynamics (CFD). This paper presents the working principle of the new approach and applies it to orthogonal cutting to investigate the thermal stresses of the workpiece under the influence of the cutting fluid. [ABSTRACT FROM AUTHOR]

Many industrial machining operations are carried out under wet machining conditions. Modelling and simulating fluid-structure-interactions and conjugate heat transfer are still a challenge nowadays. In this paper, temperature dependent heat transfer coefficients (HTC) h(T) are experimentally estimated for wet machining-like conditions in a jet cooling experiment. The transient temperature is thereby used to solve an Inverse Heat Transfer Problem for HTC function estimation. Determined HTC are applied as input in related jet cooling simulation using the Finite-Pointset-Method (FPM) to validate the modeling approach. Additionally, wet cutting simulations numerically highlight the influence of determined HTC h(T) on turning. [ABSTRACT FROM AUTHOR]

Heat reduces the performance of machine tool spindles. In particular, the heating of the shaft leads to numerous undesirable effects. Fluid-based shaft cooling systems exist but are expensive and energy-intensive. For this reason, a novel, liquid-free shaft cooling concept is researched. Heat is transferred from a rotating heat exchanger to a non-rotating and cooled structure through a narrow air gap. In this paper, the cooling potential of this concept is identified simulatively and experimentally by quantifying the heat transfer coefficients as well as the generated air friction. For the first time, a suitable simulation setup for the modelling of such heat exchangers is presented, providing a fundamental contribution to the design of liquid-free cooling systems. [ABSTRACT FROM AUTHOR]

This paper studies improving the performance of an adsorption system by improving raw bentonite as an adsorbent. Acid treatment has been used for the pretreatment of raw bentonite. Then, a composite and activated adsorbents are prepared by bentonite impregnated in salt hydrates (CaCl 2 and (NH 4) 2 CO 3). XRD, nitrogen adsorption isotherm, water vapor adsorption isotherm and kinetics are used to characterize raw and modified bentonite. Experimental results of adsorption isotherms and kinetics have been fitted using Dubinin–Astakhov equilibrium model and linear driving force model. MATLAB software has been used to solve a simulation model of an adsorption desalination system with and without heat recovery (HR). The effect of the modified adsorbents on the adsorption system performance has been investigated. The results illustrated that the surface area and pore volume of Bent/CaCl 2 increased by about 200% and 500%, respectively, compared to raw bentonite. The Bent/CaCl 2 was predicted to have the highest water uptake (0.82 kg H2O.kg−1). Bent/CaCl 2 was predicted to have a SDWP of 11.5 m3.ton−1 per day with SCP 326 W.kg−1 and COP 0.52 at 85 °C desorption temperature. Also, the SDWP was predicted to achieve 26 m3.ton−1 per day with HR under the same conditions. The SDWP can be increased to 29 m3.ton−1 at 95 °C desorption temperature. • The Bent/CaCl 2 has gained the most surface area and total pore volume (148.2 m2/g and 0.193 cm3/g). • Bent/CaCl 2 achieved high C ads with 0.8 kg H2O /kg at 90% P/P s. • Bent/CaCl 2 achieved the highest performance with SDWP 11.5 m3/ton per day and SCP 326 W/kg and COP 0.52 for the ADC cycle. • The highest SDWP is achieved as 26 m3/ton per day with utilizing Bent/CaCl 2. [ABSTRACT FROM AUTHOR]

• The performances of passive radiative cooling (PRC) coatings with ideal emittance on each surface of PV tile were compared theoretically. • The PRC coating with high broadband emissivity on the rear surface could realize a cooling effect of 3.6 °C in the field test. • The ground emissivity had a significant impact on the cooling effect of the PRC on the rear surface. • The cooling capacity of the PRC on the rear surface was proved to be immune to the impact of humidity. Temperature is one of the key factors to limit the conversion efficiency of photovoltaic modules. Passive radiative cooling (PRC) technology commonly used in the energy-saving applications is hopeful to improve this situation. In this paper, photovoltaic tile covered with PRC coating was studied to evaluate the feasibility of PRC technology. A thermal model was proposed to theoretically calculating the temperature distribution of PV tile module along the thickness direction. Two kinds of PRC coatings with different ideal infrared spectrums applied on the front and rear surface of PV tile was compared to assess the thermal and electrical performances. Then the optimum infrared spectrum and coating location of PRC coating for PV tile were determined, which means that the PRC coating with ideal broadband emittance applied on the rear surface of PV tile would be the best choice. A commercial radiative coating (CRC) with broadband emittance was applied on the rear surface of PV tile to ensure the cooling effect. The results indicated that the CRC on the rear surface could cool PV tile module down by 3.6 °C, and increase the efficiency by ∼ 0.33% under the average irradiance of 930 W/m2. Environmental parametric investigations demonstrated that the ground emissivity had a significant impact on the cooling effect of the optimal radiative coating (ORC) on the rear surface of PV tile. Moreover, the cooling capacity of the ORC was proved to be immune to the impact of humidity. [ABSTRACT FROM AUTHOR]

This paper investigates the cooling of a photovoltaic panel using a water-based absorber (PV / T). The study focuses on improving the performance of the PV panel by controlling overheating and exploiting the retained heat as thermal energy. The studied system consists of an aluminum absorber welded with circular water tubes placed under the photovoltaic module. Several parameters effects on the PV panel's performance were investigated, including the diameter of the inner tube, the water inlet velocity, and the water inlet and outlet configurations by a simulation using CFD method. To have a more realistic study, we developed a subroutine (UDF) to integrate the climate data recorded on a summer day in Oujda city (Eastern Morocco). The findings indicate that controlling the overheating of the PV / T by the cooling technique significantly improved the thermal and electrical efficiency. Whereby, the average temperature of the PV panel decreased to 26.8 °C compared to the case without cooling. In addition, it was found that both increasing the tube diameter and the water inlet velocity positively influence the PV cells temperature. Considering the four cooling configurations studied, it can be concluded that the PV cells temperature decreases from the five-tube-by-five configuration to the one-tube-by-one configuration, beside, its can gives a more uniform temperature across the PV panel. • The proposed new PVT system provides a temperature reduction of 26.8°C compared to the conventional module. • The temperature of the panel decreases with the increase of the water inlet velocity and the tube diameter. • The tube-by-tube configuration of the absorber allows a better temperature distribution and a lower PV cell temperature. [ABSTRACT FROM AUTHOR]

In the process of urban development, a large number of industrial heritages are in needs of being renovated as a result of the failure of meeting new needs. However, there has not yet formed an innovative and sustainable update design process. Based on the analysis of the problems existing in the renewal and reconstruction of industrial heritages, this paper, hereinafter, will establish an innovative design system by way of introducing extenics and BIM and combining the formalized and innovative advantages of extenics and the characteristics of BIM: information storage, processing and visual programming. In combination with the design of practical cases, this essay conducted the system, to verify its rationality and effectiveness; to discover limitations in its operation, and as the ultimate purpose, to propose directions for further research. [ABSTRACT FROM AUTHOR]

• RCS cooling by SG is essential for mitigation of MSGTR, SBLOCA-LOSI, and SBO. • PAFS was developed as an advanced safety design feature to replace the active AFWS. • The MSGTR, SBLOCA-LOSI, and SBO in 1,000 MW e PWR with PAFS are analyzed by RELAP5. • The effects of PAFS for accident mitigation and operator actions are investigated. Multiple Steam Generator Tube Ruptures (MSGTR), Small Break Loss of Coolant Accident with Loss of Safety Injection (SBLOCA-LOSI), and Station Blackout (SBO) are Design Extension Condition (DEC) accidents where the SG secondary-side cooling with operator actions are essential for the mitigation of the accidents. In the Republic of Korea, the Passive Auxiliary Feedwater System (PAFS) was developed to replace the active Auxiliary Feedwater System (AFWS). It is important to examine the existing accident mitigation strategies and evaluate whether they can be effectively applied to DECs using PAFS as well. To investigate the changes in accident mitigation characteristics and operator actions when PAFS is implemented instead of AFWS, the DEC accidents such as MSGTR, SBLOCA-LOSI, and SBO are analyzed with RELAP5/MOD3.3. Research results presented in this paper have significant implications and can be utilized to improve the accident mitigation strategies and the operator training for DEC accidents where PAFS is implemented. [ABSTRACT FROM AUTHOR]

Heat fluxes of GaN-based high electron mobility transistors (HEMTs) can reach dozens of kilowatts per square centimeter, and the heat is generated only within a small area with feature size of micrometer to millimeter length scales, which poses a huge challenge for thermal management. In this study, an embedded microfluidic cooling solution is proposed to dissipate heat from the hotspots, and thermal test vehicles are fabricated using the Micro-Electro-Mechanical System (MEMS) process. Cooling performances of hotspots with sizes ranging from 40 × 40 μm2 to 500 × 500 μm2 and varying locations are demonstrated. Thermal resistances of the test samples are analysed and the heat transfer coefficient can achieve 1.5 × 105 W/(m2∙K) using embedded microchannel cooling. We propose a compound plate spreading thermal resistance model to demonstrate the effect of the dielectric layer and the size of the heat source on heat dissipating capability of the microfluidic cooling system. Based on the thermal spreading model, when the heat source is small, integrating high thermal conductivity materials near the heat source can reduce its total thermal resistance by two orders of magnitude. By balancing the heat spreading resistance with the convective resistance of microchannel cooling, we find that ∼1 mm can be considered as the critical length for distinguishing the primary thermal management approach for different sized hotspots. This paper provides useful design guidelines for embedded microchannel cooling of devices with localized heat generation patterns, such as HEMT devices. [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]

• New efficient integrations of absorption, adsorption, and HDH plants are investigated. • Four innovative scenarios are proposed and compared to productivity and energy utilization. • The maximum improvement in productivity was between 1.57 and 2.94 m3.day−1 at 120 °C. • The maximum obtained GOR was between 1.38 and 1.75 at 120 °C. • The proposed integration demonstrates remarkable energy utilization efficiency. Thermal desalination technologies have been developed recently to solve some pressing problems, such as high energy expenditure, increasing fuel costs, and environmental problems related to conventional plants. However, these technologies still need to be enhanced in terms of water production and gain output ratio (GOR). This paper presents innovative and efficient combined thermal desalination plants consisting of absorption (ABDS), adsorption (ADDS), and humidification-dehumidification (HDH) desalination units to enhance energy utilization, water production, and overall system performance. Four innovative combined desalination plants employing different external heat recovery scenarios are presented and compared. The result from each scenario is evaluated and compared with those of the standalone ABDS and with other studies found in the literature at the same heat source temperatures. The heat source is mainly utilized to drive the ABDS plant. The ADDS and HDH are driven by the heat rejection from the ABDS components with different external heat recovery scenarios. Results illustrated that the maximum freshwater production generated from the proposed scenarios ranges between 1.57 and 2.94 m3.day−1 with a GOR of between 1.38 and 1.75 at 120 °C. Raising heat source temperatures from 55 to 120 °C decreased the improvement in the water productivity from 618.5 to 224 % and decreased the enhancement in the GOR from 222.8 to 99 %. In scenarios where the ADDS and HDH are driven by the heat rejection from the absorption and condensation process of the ABDS, the maximum freshwater production results from the ABDS unit. On the other hand, in scenarios where the ADDS and HDH are driven by the outlet hot water from the ABDS-generator, the maximum freshwater production is obtained from the HDH unit. The finding provided that the proposed innovative scenarios have an effective improvement in overall system performance indicators. [ABSTRACT FROM AUTHOR]

The application of combined cooling, heating, and power (CCHP) systems to generate both electricity and heat is growing quickly due to their high potential of lessening primary energy utilization, cost, and negative environmental impacts. This paper introduces a comprehensive review of hybrid fuel-assisted-solar powered Stirling engine-based combined cooling, heating, and power (HFSDSS-CCHP) systems. This article summarizes the typical configurations of SDSS CCHP systems, their energetic, economic, and environmental performances, as well as their operation strategies. The advantages and disadvantages of each system have been discussed. Thermodynamic models for the system components of solar - powered Stirling engines for the CCHP system are briefly presented. Besides, the most widely accepted performance indicators for guiding the Stirling engine-based CCHP system improvements are highlighted. Moreover, this review discusses the recent developments and performance analyses of CCHP systems. It is anticipated that the data gathered in this review will shed light on the promising technology of the Stirling engine for micro-trigeneration to pave the way for their marketability and extend their worldwide applications. • Recent technologies of hybrid solar - powered Stirling engine-based CCHP) systems are presented. • Recent developments allowed them to high potential for market penetration. • Operational strategies should be further investigated. • Formal indicators for energetic, economic, and environmental performances should be developed. [ABSTRACT FROM AUTHOR]

• Impact of double rows on air/mist film cooling is studied for the first time. • Sellers prediction model is appropriately modified for double rows. • Modified sellers method is proved to be more suitable for air/mist film cooling. • Air/mist film cooling effectiveness is accurately correlated by the modified model. Improving the multi-row film cooling effectiveness of turbine vanes and blades is becoming increasingly important, and the configuration design of the multi-row holes is becoming increasingly complex. This paper presents a simulation study of the air/mist film cooling characteristics on double-row-hole flat plates and makes predictions about spanwise-averaged cooling effectiveness using a modified Sellers superposition method. The effects of blowing ratio, row spacing, row arrangement, droplet diameter, and mist mass ratio on film cooling are systematically investigated. It is found that the injected mist improves the film cooling effectiveness under all operating conditions for the coolant air. The air/mist cooling is particularly effective at a blowing ratio of 1.25 or a row spacing of 5 D with the staggered two-row holes. The improvement in cooling effectiveness increases with increasing mass ratio or decreasing droplet diameter of the mist. Furthermore, the spanwise-averaged cooling effectiveness can be accurately predicted by modifying the classical Sellers superposition model. This study lays the foundation for accurately predicting the distribution of air/mist film cooling effectiveness of turbine vanes and blades, and helps to promote the development of practical air/mist film cooling technology. [ABSTRACT FROM AUTHOR]

• Exact solution for radial CO 2 injection with Joule-Thomson cooling & heat exchange. • Heat exchange by Newton's law yields temperature profile stabilisation with time. • The Joule-Thomson effect can significantly decrease reservoir temperature. • Analytical model allows estimating the injection rates that avoid hydrate formation. This paper discusses axi-symmetric flow during CO 2 injection into a non-adiabatic reservoir accounting for Joule-Thomson cooling and steady-state heat exchange between the reservoir and the adjacent layers by Newton's law. An exact solution for this 1D problem is derived and a new method for model validation by comparison with quasi 2D analytical heat-conductivity solution is developed. The temperature profile obtained by the analytical solution shows a temperature decrease to a minimum value, followed by a sharp increase to initial reservoir temperature on the temperature front. The temperature distribution head of the front is determined by the initial reservoir temperature, while the solution behind the front is determined by the temperature of injected CO 2. The analytical model exhibits stabilisation of the temperature profile and the cooled zone. The explicit formula for temperature distributions allows determining the maximum injection rate that avoids hydrate formation. [Display omitted] [ABSTRACT FROM AUTHOR]

The ITER Neutral Beam Test Facility (NBTF) is hosted in Padua and includes two experiments: MITICA, the 1 MeV full-scale prototype of the ITER HNB injector, and SPIDER, the 100 keV full-size ITER Radio Frequency (RF) negative ion source. SPIDER and MITICA experiments are actively cooled by Ultrapure Water (UPW) to electrically insulate in-vessel components that are biased to high voltage levels. Water conductivity is an important monitored parameter to ensure components' insulation by limiting the leakage current of active cooled equipment. A very low conductivity water is especially important in MITICA, where components need to operate up to 1 MVdc, an insulation level beyond the actual industrial standard. Careful selection of suitable materials for any in-vessel (vacuum insulation) and out-vessel component (air insulation) is of utmost importance, as their interaction with water and different environment may affect their chemical and mechanical properties. Additionally, materials selection can severely influence water chemical characteristics: cooling circuits are made of metals (copper, aluminium, steel) and insulating materials (plastic, rubber) when connecting parts at different electric potentials. During the first years of cooling plant exploitation, it was shown that water degrades more quickly than estimated by design. The Primary Circuits (PCs) that showed the most severe water degradation during operation are SPIDER and MITICA power supply ones, respectively called PC01 and PC08. This paper describes the results of specific experimental tests performed on MITICA PC08 to evaluate possible causes of water degradation and detect sources of contaminants that might compromise future experimental campaigns. The cooling circuit was subdivided in different sections and water circulation tests were performed at constant temperature and flowrate. Water samples were collected and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analyses were performed to quantify the type and amount of metals released. Moreover, components samples collected along their cooling circuits were characterized by Scanning Electron Microscope (SEM) technique to detect undesired contaminants and immersed in UPW to study their corrosion behaviour using metal release tests. [ABSTRACT FROM AUTHOR]

Radiative cooling (RC) is a passive cooling technology that has been used to cool photovoltaic (PV) panels since it does not consume energy or produce pollution. Previous studies employed RC materials above the PV panels to directly enhance the thermal emission, thereby lowering the temperature, but this method interfered with the absorption of the sunlight simultaneously, and thus reduced the power conversion efficiency (PCE). In this paper, an indirect cooling system for PV panels based on RC was proposed, consisting of the PV module, RC module, cold storage module, and piping system. The RC module was arranged between the adjacent PV panels, and the generated cold energy was used to cool the PV panels through the water system. Experimental results showed that the system without cold storage module reduced the average temperature of PV panels by 13.6 °C and 10.6 °C respectively in summer and autumn, and increased the PCE by 1.21% and 0.96%, respectively. After employing the cold storage, the cold energy generated at night by the RC module was stored for daytime use, then the average temperature of PV panels was reduced by 17.8 °C and 16.6 °C in summer and autumn, and the PCE was increased by 1.69% and 1.51%, respectively. Moreover, a cover shield and large water tank capacity could further improve the system efficiency. In addition, the proposed system has an economic payback period of 8 years and is expected to increase at least 2.8 billion kWh of PV power generation in 2050. • An indirect cooling system for PV panels based on radiative cooling was proposed. •The average temperature was reduced by 17.8 °C, and the PCE was increased by 1.69%. •A cold storage module was used to further improve the cooling performance. •The employment of cover shield and the volume of the water tank were discussed. •The economic payback period is 8 years. [ABSTRACT FROM AUTHOR]

In reciprocating diamond wire sawing of quartz glass, the reversing and acceleration and deceleration will cause the position change of diamond wire, resulting in the discontinuous wire sawing in the reversing stage, so as to leave residual material on the processing surface and form wire marks. Also, the cutting load will cause diamond wire deformation as bow shape, and affect the machining accuracy. In this paper, the evaluation of DWS machining performance of quartz glass focus on the sawing time, cutting force and vibration, wire tension, machining surface flatness and roughness, surface morphology and wire state. The theoretical analysis of wire mark was carried out, and the simplified wire bow model of quartz glass sawing was established. The existence of wire mark and wire bow were verified by detecting the 3D contour of the slice. In addition, a diamond wire electrical discharge sawing (DWEDS) was performed to find the differences to DWS in the above indicators. Experiments were presented in jet cooling and bath cooling conditions. It was found that the cutting force, vibration, and wire tension of DWEDS are more stable than that of DWS. The DWEDS has been proved helpful to improve machining performance of quartz glass from surface roughness, sawing time, processing state, and wire bow control as it reduces the macro cutting force acting on the diamond wire although the discharge effect is weak. The SEM of slice surface and diamond wire showed no significant difference between DWEDS and DWS. Also, the influence of feed speed and cooling methods on machining performance was investigated. [ABSTRACT FROM AUTHOR]

This paper models the retrofitting of traditional rural dwellings in Uganda by introducing passive cooling and daylighting measures. With climate change, outdoor temperatures in parts of the Global South will become unbearable. Communities will be forced to spend more time indoors and thus require further cooling and daytime lighting for thermal and visual comfort. Passive measures can address this while also attenuating energy consumption and diversifying energy use. For the first time, these measures are combined and modelled for those purposes in a rural developing country context where there is limited access to electricity. Using SketchUp and EnergyPlus™, we simulate 15 scenarios of passive cooling and daylighting measures for two baseline scenarios: electrified mud hut and semi-permanent dwelling. Those are also feasible scenarios for similar greenfield unelectrified architectures. The results from the simulated scenarios on electrified dwellings include energy savings, and from these, payback periods are calculated. Two cost-effective scenarios are identified. For mud huts, combining shading (through vegetation) with a centralised fibre optic solar concentrator enables an annual reduction of 31 % of energy consumption. For semi-permanent dwellings, painting rooftops white combined with the integration of solar water light bulbs reduces energy consumption by 47 %. In terms of payback periods for the selected scenarios, the former is four years and nine months, while the latter is two months. • Modelling of passive cooling and daylighting measures in North Ugandan dwellings • Design of mud hut and semi-permanent structures based on field surveys • Extensive presentation of rationale of selection for passive measures • Combination of passive measures into scenarios for energy performance evaluation • Assessment of energy savings, costs and scenarios payback periods [ABSTRACT FROM AUTHOR]

Since the onset of the 21st century, the number of data centers has been increasing continuously, and the energy consumption of these data centers has aroused people's attention. Many experiments have been conducted to reduce the energy consumption in data center cooling, and free cooling utilization based on the mechanically driven two-phase cooling loop (MTCL) system has been proven to be an effective solution for energy saving. This paper reviews the research on and developments in the practical application of the MTCL system for data center cooling in recent decades. It presents a detailed summary of the progress of research on the MTCL system in data centers. The aim is to provide an improved understanding of the system and promote the application of this system in data center energy saving. [ABSTRACT FROM AUTHOR]

Piezoelectric stack actuators (PESAs) are usually used in applications requiring a fast response, high resolution, and high accuracy. Self-heating during continuous drive with a large voltage amplitude at high frequencies can damage PESAs and limit the driving conditions. A sufficient cooling method is necessary to increase the driving frequency and driving amplitude. This paper proposes a direct forced liquid cooling system for PESAs and experimentally and numerically evaluates the PESA temperatures when employing this cooling system. Silicone oil, which is an excellent electrical insulator, and has a high heat transfer coefficient and good stability, was selected as the coolant. The proposed forced liquid cooling can suppress the temperature rise to about 10% of that achieved through natural heat dissipation. With an input voltage amplitude of 50 V pk at a frequency of 10 kHz, the PESA cannot be continuously driven with natural heat dissipation. Using the proposed liquid cooling, the temperature of the PESA resin coating was kept well below the upper limit given by the manufacturer. Furthermore, the internal temperature of the PESA was estimated from heat transfer analysis using a finite element model. This confirmed that the internal temperature of the PESA was lower than the Curie temperature. • Proposed forced liquid cooling is 10 times more effective than natural cooling. • Selection of silicone oil as a coolant with high insulation and high durability. • Heat transfer analysis of internal temperature of a piezoelectric stack actuator. • Electrodes of piezo stacked actuator reduce the internal temperature rise by 1/3. [ABSTRACT FROM AUTHOR]

• A radiant cooler composed of new high molecular polymer. • Near-infrared reflectivity is strengthened by a simple structure of three-layer film. • Thermal radiation control in three different bands is realized. • Enhanced cooling effect of the radiator can be achieved. • Considerable significance for the photovoltaic daytime radiative cooling. Passive daytime radiative cooling is a promising new field for solving the energy shortage all over the world. Especially for passive radiant cooling technology on photovoltaic field, the radiant cooling film must also have high transmittance, which undoubtedly puts forward higher requirements. At present, monocrystalline silicon photovoltaic cell are the dominant products in the photovoltaic market. Many passive cooling equipment such as temperature plates, fins, and phase change blocks will increase the weight and the complexity of photovoltaic cell, so radiative cooling thin films are attracting more and more attention due to lightweight and easy replacement. In this paper, it is proposed a composite structure of polyethylene glycol terephthalate (PET) film combined with a high-reflective layer in part of the wave band, which has a maximum transmittance of 0.97 in 0.3–1.1 μm and a maximum reflectance of 0.91 in 1.1–4.0 μm. In addition to the transmittance and reflectivity of the corresponding wavelength, the effects of electrical efficiency and cooling power are also studied. It was found that the photoelectric conversion efficiency increased, meanwhile the cooling power 211.34 W·m−2 can be reached, and the working temperature of the photovoltaic cell can be reduced by 11.65℃ under the maximum temperature 75.80℃ in normal operating conditions. Due to its excellent performance, this proposed structure may have potential practical applications in daytime radiation cooling of photovoltaic cells on sale. [ABSTRACT FROM AUTHOR]

• The film cooling performance of tip with inclined cavity bottom is experimental studied. • The blade tip with inclined cavity bottom enhances cooling performance at some blowing ratios. • The blade tip with cavity bottom inclined to suction side can reduce the aerodynamic loss. The gas turbine blade tip poses as one of the most challenging areas for blade cooling, primarily due to its intricate three-dimensional flow characteristics, which make it one of the primary contributors to aerodynamic loss within the turbine stage. In this paper, the adiabatic film cooling effectiveness (η) distributions at five squealer tip structures (Original, PS7.5, PS15, SS7.5, SS15) with varying inclined angles of cavity bottom surface were obtained using pressure sensitive paint technique (PSP) under five coolant blowing ratios (BR = 0.4, 0.8, 1.2, 1.6, 2.0). Combined with the numerical simulations verified by the experimental data, the tip flow field details were described to reveal the cooling characteristics of the tip region. The results indicate that, at low BR s, the film hole downstream exhibits apparent cooling traces, which are most pronounced at the SS15 tip. With the increase of BR , the cooling traces gradually fade, and the area-averaged film cooling effectiveness (η Α-avg) rises. At low BR s (BR = 0.4, 0.8), the η Α-avg of the SS15 tip is 12.8 %, and 8.4 % higher than that of the Original tip, respectively. At BR = 1.6, the η Α-avg of the PS15 tip is the highest, 3.9 % higher than that of the Original tip. The η Α-avg of SS7.5 is the lowest at all BR s. In addition, the pitch-averaged η (η avg) of PS7.5 at some BR s is higher in the front part of the tip, compared to the Original tip. At BR = 1.2, the area-averaged total pressure loss coefficient ( C p t ¯)of the PS7.5 and PS15 is 1.46 % and 1.58 % higher than that of the Original tip, respectively. However, the C p t ¯ of the SS7.5 and SS15 is 1.77 % and 10.28 % lower than that of the Original tip, respectively. [ABSTRACT FROM AUTHOR]

• A flat plate heat pipe with dimensions of 500 × 200 × 3 mm3 and containing 19 independent microchannels inside is developed. • CFD modeling based on the VOF model and improved Lee model was performed to reproduce the heat transfer behaviors. • The ANN model agrees well with the simulated data with MSE and R of 1.30 × 10-5 and 0.9990, respectively. • The model constructed can provide an effective tool for the adaptation and optimization of heat pipe in 5G base station. To address the significantly increased heat dissipation requirements of 5G base stations, a flat plate heat pipe (FPHP) of 500 × 200 × 3 mm3 comprising of 19 independent channels was developed. To solve the problem of simulation distortion due to the high superheat of the initial boiling of the working fluid in the ultra-long channel of 490 × 5 × 1.5 mm3, this paper adopts the Lee model considering the superheat, and simulates based on the Volume of fluid method, and the simulation results are compared with the experiments, and the average relative error is less than 5 %. The FPHP was explored at 100–500 W heat power and filling ratio of 30 %-70 %, depending on the application scenarios of the base station. By partitioning the 19 channels and calculating the thermal resistance of the FPHP based, an Artificial neural network (ANN) model with 10 hidden layer nodes is established based on 675 data sets. The results showed that the mean square error and correlation coefficient were 1.30 × 10-5 and 0.9990. The ANN prediction results are validated, the mean relative error is 5.4 %, demonstrating that the ANN model can be an effective tool to optimize the FPHP for the telecommunication equipment. [ABSTRACT FROM AUTHOR]

Energy scarcity in various regions worldwide not only adversely affects people's quality of life but also hinders overall development. Pakistan is among the nations grappling with energy shortages, with high consumption and limited generation, resulting in a substantial energy shortfall of 2500 MW. Floating photovoltaic (FPV) systems present an attractive solution for harnessing solar energy, particularly where land availability is constrained. These systems offer benefits such as conserving water and land while delivering higher power output compared to conventional terrestrial PV systems. While the advantages of FPV systems are generally recognized, research on their specific characteristics remains limited. This paper aims to address this gap by providing a comprehensive review of FPV technology and its potential applications, particularly in Pakistan. By comparing ground-mounted and FPV systems, the study explores the economic, technological, and environmental implications of FPV adoption in regions with similar geographical profiles. The analysis highlights not only the cooling impact of water, which enhances the efficiency of FPV systems, but also other key aspects such as cost-effectiveness, site preparation, and environmental impact. Output power of FPV and land based obtained are 390 kW and 370 kW at irradiances of 180kW/m2and 170 kW/m2 at temperature from 30 to35°C respectively. The findings demonstrate the viability of FPV systems and emphasize that by leveraging the characteristics of water temperature, it becomes feasible to more accurately predict the electricity generation potential of FPV systems. This synthesis offers new insights and underscores the potential for FPV adoption in areas facing similar energy challenges. [Display omitted] • FPV Systems' rise in solar energy generation in Pakistan was analyzed. • FPV systems performance was compared with ground PV systems. • FPVS research gaps with emphasis in Pakistan are discussed. • New insights about water's cooling impact on FPVS are presented. [ABSTRACT FROM AUTHOR]

• A Bayesian optimization is conducted utilizing an automated framework to enhance the trade-off between heat transfer and pressure drop using spline-based two-dimensional pin-fin arrays. • The optimization objectives include minimization of pressure drop, maximization of heat transfer, and maximization of efficiency. • The maximization of efficiency optimization yields designs which balanced aerodynamic characteristics with total surface area, leading to enhanced thermal performance. • Pin-fin arrays using four splines outperform all other geometries due to the symmetric nature of the shape generation. Pin-fin arrays are crucial in the cooling of aerospace components. Specifically, pin-fins find extensive usage in the trailing edge of turbine blades, primarily due to the harsh operating conditions these blades experience. With the development of additive manufacturing, complex internal geometries that were previously too expensive to manufacture are now feasible. This advancement has created a new pin-fin design space to be explored. In this paper, Bayesian optimization (BO) is conducted to find the pin-fin array that optimizes the trade-off between heat transfer and pressure drop in a two-dimensional channel. The complexity of the pin-fin geometry varies, and is controlled by the number of connecting piece-wise cubic splines used to close the shape. Different designs are obtained using 3-, 4-, 5-, and 6-splines in a staggered pin-fin array orientation. The optimization objectives included the minimization of pressure drop, the maximization of heat transfer, and the maximization of efficiency. It is found that the pin-fins which utilize 4-splines outperform all others due to their symmetric characteristics. The performances of the pin-fin array plateaus after increasing the complexity beyond 5-splines. It is concluded that the optimization objective significantly influences the final shape characteristics and behavior. As expected, the pressure drop minimization finds aerodynamic shapes while heat transfer maximization increases the total surface area in the channel. The maximization of efficiency results in a balance of aerodynamic shapes and total surface area. [ABSTRACT FROM AUTHOR]

Heating up of photovoltaic modules during operation results in a significant power output reduction. This effect is especially relevant in regions with the highest photovoltaic potential, where irradiance and ambient temperature are particularly high. In this paper, a novel low enthalpy geothermal cooling system that improves the efficiency of a commercial solar module is described and experimentally validated. Two heat exchangers, one attached to the backside of the module, and another introduced inside a 15 m deep borehole, are connected in a closed circuit. A water-based coolant is pumped through the system, evacuating the excess heat from the module, and dissipating it underground in a clean and efficient manner, without additional water consumption after filling the system. The performance of the cooling system was experimentally tested by implementing it, for the first time, in a single-axis solar tracking isolated photovoltaic facility. Extensive tests were carried out in Spain, between September 2021 and August 2022 under a wide variety of environmental conditions. The efficiency improvement system has demonstrated its technical feasibility over a one-year period, showing a peak net efficiency improvement up to 13.4 %. Moreover, a positive net efficiency improvement has been demonstrated all year long, even during the winter months. [ABSTRACT FROM AUTHOR]

The guide shield is positioned on the exterior of the bearing strut of the turbine rear frame, serving the dual purpose of insulating from hot gas and providing rectification. However, the guide shield still faces the severe risk of the external high-temperature environment for the advanced aero-engine. The conventional cylindrical hole exhibits inadequate spanwise cooling performance. To enhance film cooling effectiveness (η) for the guide shield, a new type of V-shaped cratered diffusion (VSCD) hole is proposed in this paper. The η of the guide shield is measured by the pressure-sensitive paint (PSP) technique. The effect of the density ratio (DR = 1.0, 1.5, and 2.6) and blowing ratio (BR = 0.5, 0.75, 1.0, 1.25, and 1.5) on the η of the guide shield is considered. Furthermore, the interaction of the mainstream and the coolant also is predicted by the numerical simulation with the RANS method. The results indicate that the VSCD hole can decline the jet momentum of the cooling film, which greatly increases the adhesion of the coolant on the central line of the hole. The introduction of the V-shaped crater creates a diversion effect, leading to the emergence of areas with the heightened η on both sides of the outlet of the V-shaped crater. Increasing the DR of the coolant, the η of all the guide shields is dramatically enhanced. As the BR grows, the coverage of the coolant on the guide shield is raised, whereas, the growth ratio gradually decreases. Compared to cylindrical holes, VSCD holes exhibit more pronounced advantages at higher BR s. At BR s of 0.5, 1.0, and 1.5, the area-average η values increase by 18.2%, 20.7%, and 24.5% respectively for VSCD holes. The proposed VSCD hole can significantly improve the η and provide an optional scheme for efficient cooling of the guide shield under practical conditions. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of a cooling system designed for concentrated photovoltaic (PV) systems. To enhance the performance of system and reduce operating temperature, mini-channels have been integrated onto the PV cells. Heat transfer improvement in these mini-channels is proposed by integrating ribbed grooves in a parallel alignment on their sidewalls. Water is used as a cooling fluid having laminar flow regime maintained within the Reynolds number between 100 and 500. The mini-channel is subjected to a constant heat flux, and various parameters, such as rib height, pitch, and angle are examined in order to assess their impact on Nusselt number, thermal resistance, temperature fluctuations, and friction factor variation. Subsequently, by identifying the optimal rib dimensions, the rib arrangement is further investigated. Results demonstrate that compared to a smooth channel, the presence of ribs reduces thermal resistance by up to 25.9 % as the Reynolds number increases. Furthermore, increasing rib height induces more vortices behind the obstacles, enhancing heat transfer between the fluid and channel walls. Additionally, by altering the rib arrangement, thermal resistance decreases significantly, with the maximum reduction of 32.14 % observed in the case of a two-blade configuration. Moreover, the integration of blades leads to a maximum 111.96 % increase in the Nusselt number compared to a smooth channel. In this context, the 2-blade and 4-blade configurations result in a maximum reduction of 6.48 K in the channel base temperature compared to the optimized ribbed mini-channel. These findings offer valuable insights into enhancing the performance of concentrated PV systems through innovative cooling strategies. [ABSTRACT FROM AUTHOR]

• Presents an analytical solution for thermal spreading in a cylindrical body with spatially varying side wall cooling. • A series solution is derived, with coefficients shown to be the solution of a set of linear algebraic equations. • Impact of key non-dimensional parameters on temperature field and thermal resistance is investigated. • Results are shown to be in excellent agreement with past work for special cases. • Results are of relevance for edge cooling of microprocessor chips as well as batteries. Thermal spreading and constriction resistance play an important role in thermal management of a variety of engineering systems, including semiconductor devices. Moreover, thermal contact resistance at interfaces between materials is also governed by spreading and constriction processes. Most of the past literature on theoretical modeling of thermal spreading from a source into a larger body assumes an adiabatic side wall, whereas several recent thermal management problems involve active cooling at the side wall. This work addresses such scenarios by solving the thermal spreading problem in a finite thickness cylinder with spatially varying convective heat transfer on the side wall. An eigenfunction-based series solution for the temperature field is written, the coefficients of which are shown to be governed by a set of coupled algebraic equations. Results are shown to agree well with past work for special cases of the general analysis presented here. Thermal spreading resistance is computed for a number of practical scenarios, including step function, periodic and sinusoidal convective cooling on the side wall. In each case, it is shown that the temperature distribution is consistent with the nature of the spatially varying boundary condition. A key theoretical insight from this work is that under certain conditions, the classical definition of thermal spreading resistance may become negative due to the presence of two heat sinks in the problem. Therefore, analysis based on total resistance may be more appropriate. This work offers a significant generalization of past papers, making it possible to analyze realistic thermal management problems, in which, side wall cooling plays an important role. [ABSTRACT FROM AUTHOR]

• A new data center cooling system integrating heat recovery with free cooling is proposed. • The system can work selectively in four different modes according to conditions and demands. • Stable performance of each mode and dynamic performance in mode switching are obtained. • Annual power consumption and heat recovery analysis are conducted in five cities. Rapid growth of data centers has caused a huge increase in energy consumption. Utilizing natural cold resources and harvesting waste heat are two promising ways to reduce the total power consumption of data centers. This paper proposes an integrated system of free cooling and heat recovery. The system has four working modes: mechanical cooling, mechanical heat recovery, pump free cooling and pump heat recovery. Experimental results show that pump free cooling mode can achieve an energy efficiency ratio of 7.99 when outdoor temperature is 2 °C, and different modes can be switched smoothly. The applicability of this system has been evaluated in five different cities in China. The results show that annual average energy efficiency ratio can reach 6.18 and free cooling time can take up as high as 72.9% during operation in Xining. The system can harvest the most heat in Harbin, 7930.96 kW∙ h per year, while the least in Guangdong, 645.31 kW∙ h per year. This means that this new system has relatively great application prospects in northern cold cities of China, while is moderately limited in southern cities. [ABSTRACT FROM AUTHOR]

Although the solar-powered absorption chiller is recently a trending technology for space cooling of buildings, it requires a bulky thermal storage device and complex installations to achieve all-day cooling. In this paper, a new system that couples the solar-driven absorption chiller and radiative sky cooling is proposed to realize 24-h continuous cooling with less floor space and smaller thermal storage. This system involves a specialized module that utilizes the medium temperature flat panel solar collector on its top layer and a selective radiative cooling absorption layer on the bottom layer; The top layer faces the sky during the daytime to collect solar thermal energy to drive the absorption chiller, and it will be flipped to the bottom layer at nighttime to realize radiative cooling. The proposed system is analyzed by coupling the steady-state models of each subsystem and a cooling load model, which are later applied to evaluate the cooling performance under varying weather conditions within a day. The simulation results show that the system can stably meet the cooling demand of 70 m 2 room while only needing half the floor area and a thermal storage tank that is 4 times smaller than the traditional PT-AC system. • A new system combined AC and RSC is proposed to realize 24-h continuous cooling at smaller space and thermal storage. • The steady-state model of this system is analyzed and compared with the traditional PT-AC. • This system can meet the room heat load during most of the day except sunset. • The performance can be improved significantly by reducing the convection and conduction heat loss. • This system only needed a 4 times smaller thermal storage tank and half the floor space. [ABSTRACT FROM AUTHOR]

Conventional air-conditioners in data centers generally have the problems of high energy consumption and poor cooling effect. In this paper, a composite cooling system with pump-driven heat pipe and vapor compression operation modes is proposed to solve the above problems. The system adopts pump supply liquid technology and rack-level terminals. The cooling effect, energy efficiency, and annual performance of the system are analyzed in this paper. In terms of energy efficiency, the coefficient of performance in vapor compression mode is 6.6–3.8 (outside temperature is 15–35 °C); the coefficient of performance in heat pipe mode is 15.8–9.7 (outside temperature is −15–15 °C). In terms of the cooling effect, the novel system performs well for temperature control accuracy, and the on-demand supply cooling of each rack can be realized. In terms of the annual performance of the typical city, the annual average coefficient of performance of the novel system in vapor compression mode increases by 8.5% compared with the system adopting direct expansion technology. The power usage effectiveness of the data center that adopts the novel cooling system can reach 1.23 which satisfies the current standard. • A rack-level data center cooling system adopting pump supply liquid technology is presented. • The cooling effect and energy efficiency performance are analyzed through experimental study. • The on-demand supply cooling of each rack can be realized. • The power usage effectiveness of the data center adopting the novel cooling system can reach 1.23 in the typical city. [ABSTRACT FROM AUTHOR]

Due to the higher practicability and annual utilization, the dual-use heat pump systems are more popular in practical demonstrations. Although there are various kinds of designs for such system, most of them focus on the performance enhancement in heating mode and pay little attention to the cooling capacity. The proposed three-dimensional composite heat exchanger structure based on a concentrator plus fins could not only improve the total output in heating mode but also lower the condensing temperature by shading the solar energy with the concentrator to improve the cooling COP. Different from previous study, this paper focus on the improvement potential in cooling mode of the novel system. Experiments are carried out and used for the validation of mathematical model. By analyzing the physical state of the refrigerant during the cycle, the mechanism is revealed in detail and depth. Results show that the dryness decrease at evaporator inlet caused by the condensing temperature drop is the main reason for capacity improvement, while the mass flow rate also has crucial impact. With high mass flow rate, the mean cooling COP of proposed system could be as high as 3.1, 0.16 higher than the system without concentrator shading. • The paper presents the improvement impact in the cooling cycle. • Experiments are carried out for the validation of distributed parametric model. • The decreased dryness at the evaporator inlet explains for the increased cooling. • Lower condensing temperature may cause lower cooling energy with fixed throttling. • Proposed system could get a mean cooling COP of 3.1, 0.16 higher than irradiated system. [ABSTRACT FROM AUTHOR]

In a hydrogen station that operates with direct fueling through the use of a 700 bar boost compressor, the outlet hydrogen temperature can significantly increase, stressing the chiller system. This paper evaluates improvements that can be made to the auxiliary cooling system integrated with the compressor. Both theoretical modeling and experiments were performed at Cal State LA Hydrogen Research and Fueling Facility. The findings suggest that adjusting the auxiliary closed-loop cooling system from 15 °C to 10 °C reduced the station energy consumption and decreased the demand on the station chiller that needed to provide −20 °C hydrogen at the hose. The overall energy consumption for a single fueling reduced by between 2.86 and 9.43% for the set of experiments conducted. After the temperature of the closed-loop cooling system was reduced by 5 °C, the boost compressor outlet temperature dropped from 46-50 °C–40 °C and consequently at the hose the hydrogen temperature declined by 3 °C. Results were scaled up with a forecast on the number of daily refueling events. With a low number of daily fuelings, the proposed set-up showed a minor influence on the overall station energy consumption. However, the benefits were more pronounced for a connector station with sales at 180 kg/day, where the energy efficiency improved by between 1.4 and 5.5%, and even more so for a higher capacity station at 360 kg/day, where the improvement was between 2.9 and 8%. [Display omitted] • Hydrogen Station with two booster compressors and a hydrogen chiller. • Water process chiller tuning-up and new-set-up. • Hydrogen Refueling Process Energy Reduction. • Results scaled up by forecasting the number of fueling events. • Pilot, Connector, and Main Stations Evaluation. [ABSTRACT FROM AUTHOR]

In this paper, the experimental and numerical investigations of both swirling hybrid rocket motors without and with the design of regenerative cooling (RC hereafter), using 90%-wt H 2 O 2 and polypropylene (PP) as the liquid oxidizer and the solid fuel, respectively, were performed and compared. We implemented a new design of regenerative cooling using the oxidizer to transfer the heat generated from combustion. A series of ground horizontal hot-fire tests, which include the catalytic-bed only and the motor without/with RC were performed to measure the propulsion performance related parameters. The resulting C* efficiency of the RC design with catalytic-bed only remained in comparison with the one without RC. With a similar initial combustion chamber geometry, the RC implementation resulted in a better engine Isp efficiency from 96.3 to 98.6 with a lower O/F ratio from 6.49 to 5.94. In addition, the topologies of the burned fuel grain surface were optically measured by a 3D laser scanner. The resulting variation of regression rates between the upstream and downstream fuel for the chamber with the RC was smaller than case without the RC. Moreover, a simplified semi-empirical computational fluid dynamics (CFD) model based on the measured regression rates was constructed for investigating the physical phenomenon inside the hybrid rocket combustion chamber. The simulations show that a higher swirling number in the later portion of the port was found for the RC case. By concerning about the different O/F ratios and port size of the burned fuel, a series of simplified numerical CFD investigation with a fixed O/F and a fixed port size varying the regression rates from upstream to downstream fuel systematically with the same average region rate was performed to complement the semi-empirical CFD simulations. The results showed that there were two distinct regions including an upstream non-classical region dominated by the gas impingement of gas and a downstream classical region caused by the swirling effect of gases. In the non-classical region, the calculated distributions of the swirling numbers of the former are essentially the same for all the cases no matter what the magnitude of the regression rate is, while in the classical region higher swirling numbers are found for the case of more uniform distribution of regression rates. Heat generated near the upstream of the fuel grain was transferred more efficiently through the design of RC, which makes the resulting fuel regression more uniform than that without RC. The resulting swirling efficiency in the RC case was higher than that without RC. The HRM with RC hence had a better engine Isp efficiency with a lower O/F ratio. • Hybrid rocket motors with the design of regenerative cooling improves the propulsion efficiency. • Optical 3D scanner precisely measures the solid fuel topology. • The results of the proposed numerical model for hybrid rocket combustion are in good agreement with experiments. [ABSTRACT FROM AUTHOR]

This paper presents the results from end milling of Inconel 718 with a newly designed and manufactured minimum quantity lubrication (MQL) delivery system. This involves spraying electrically charged tungsten disulphide (WS 2) nano particles dispersed in vegetable oil through pressurised air as a coolant/lubricant. This method improved the cooling and lubrication during machining. Tool life, surface integrity and cutting forces obtained from end milling Inconel 718 with this new system are compared with conventional flood and MQL cooling/ lubrication. The electrically charged WS 2 nanofluid was found to increase tool life by ≈10% and significantly improve surface integrity. [ABSTRACT FROM AUTHOR]

A new PEMEC system without integrated cooling channels inside the PEMEC stack is analyzed in this paper. An external energy source is integrated into the heat exchanger to control the stable operation of the system. Based on the balance of charge, mass and energy, the models of both the stack and the system are established. The influences of operating parameters, such as inlet water flow rate, inlet water temperature and current density, on the PEMEC stack performance are investigated, and the energy efficiency and exergy efficiency of the PEMEC system under both the heat dissipation condition and the adiabatic condition are discussed. The results show that the purpose of keeping the operating temperature of the stack can be achieved by regulating the inlet water temperature and flow rate. A relatively good operating mode is a low inlet temperature, an insulated stack and a current density in range of 1.0 and 2.0 A/cm2. The present work can provide some guidances for the optimum design of the PEMEC system. [ABSTRACT FROM AUTHOR]