Lower Surface Temperature Research Articles

Surface Temperature Experienced and Irrigation Effects on Artificial Turf

Artificial turf has gained widespread use in sporting fields as it is considered a water-saving and maintenance-free alternative to natural turfgrass. However, the high surface temperatures that occur during the day are a potentially important unfavorable feature of artificial turfgrass. The objective of this study was to establish the temperatures experienced on an artificial turf surface and to evaluate the effect of irrigation on artificial turf surface temperature. Data was collected over five surfaces across a sports facility on the campus of the University of Thessaly in Larissa, Greece. Results showed surface temperatures on artificial turf (AT) as significantly higher than running track (RT), asphalt (AS), bare soil (BS), and natural grass (NG), with maximum surface temperatures of 72oC. Solar radiation accounted for most of the variation in surface temperature of the artificial turf (r2=0.92) as opposed to air temperature (r2=0.38), and relative humidity (r2=0.50). To lower surface temperature, four irrigation regimes were used (1x60 min, 1x30 min, 2x15 min, and 3x5 min water application). Irrigation reduced the surface temperature by as much as 30°C compared to the unirrigated surface, but these low temperatures were maintained for 90 to 120 minutes long. The most effective cooling effect occurred when water was applied in a 3-cycle, 5-minute duration, where the irrigated surface temperature remained below the unirrigated surface throughout the time after the first watering.

Opinion: A research roadmap for exploring atmospheric methane removal via iron salt aerosol

Abstract. The escalating climate crisis requires rapid action to reduce the concentrations of atmospheric greenhouse gases and lower global surface temperatures. Methane will play a critical role in near-term warming due to its high radiative forcing and short atmospheric lifetime. Methane emissions have accelerated in recent years, and there is significant risk and uncertainty associated with the future growth in natural emissions. The largest natural sink of methane occurs through oxidation reactions with atmospheric hydroxyl and chlorine radicals. Enhanced atmospheric oxidation could be a potential approach to remove atmospheric methane. One method proposes the addition of iron salt aerosol (ISA) to the atmosphere, mimicking a natural process proposed to occur when mineral dust mixes with chloride from sea spray to form iron chlorides, which are photolyzed by sunlight to produce chlorine radicals. Under the right conditions, lofting ISA into the atmosphere could potentially reduce atmospheric methane concentrations and lower global surface temperatures. Recognizing that potential atmospheric methane removal must only be considered an additive measure – in addition to, not replacing, crucial anthropogenic greenhouse gas emission reductions and carbon dioxide removal – roadmaps can be a valuable tool to organize and streamline interdisciplinary and multifaceted research to efficiently move towards understanding whether an approach may be viable and socially acceptable or if it is nonviable and further research should be deprioritized. Here we present a 5-year research roadmap to explore whether ISA enhancement of the chlorine radical sink could be a viable and socially acceptable atmospheric methane removal approach.

Inactivation of microorganisms on surfaces of a refrigerator compartment with low-pressure mercury lamps

Household refrigerator compartments and cold chain systems are highly susceptible to microbial contamination. To minimize the surface-contact disease transmission, low-temperature surfaces must be inactivated. Currently, there is no environmentally friendly and convenient means for surface sterilization at low temperatures. This investigation proposed the use of low-pressure mercury lamps to sterilize the bottom surface of a refrigerator. The mercury lamps emitted UVC irradiation and were mounted horizontally on the sidewalls of the refrigerator compartment to inactivate Escherichia coli (E. coli) on the bottom surface. The measured irradiances and E. coli inactivation efficiencies were used to validate the surface-to-surface (S2S) model. The impacts of the refrigeration temperature (20 °C, 4 °C, and −18 °C, respectively) on the UVC output and E. coli sterilization efficiency were evaluated. And so did for the impacts of the relative humidity (ranging from 45 % to 85 % at 4 °C). The required time for operation of the UVC lamps to reach a 3-log reduction in E. coli was calculated for different lamp placements. The results revealed that the UVC emission of low-pressure mercury lamps decreases remarkably with the temperature. The necessary UVC irradiation dose to achieve the same inactivation efficiency increases as the temperature decreases. To extend the operating life of UVC lamps, the installed lamps should make the irradiance distribution on the target surface as uniform as possible.

Frosting characteristics of microchannel heat exchangers: Parametric studies and correlation development

Recently, microchannel heat exchangers (MCHX) have been widely used in heat pump systems due to their high surface-to-volume ratio and high efficiency of heat transfer. However, when the MCHX operates in frosting conditions, its performance is adversely affected. To study the frost formation and distribution characteristics of MCHX, a comprehensive parametric study was performed for the MCHX with a larger fin pitch. The effects of fin geometries and environmental parameters on the frosting characteristics of MCHX were studied. Fin height (Fh) can effectively inhibit frost formation, which is due to the increase of surface temperature with the increase of Fh. When Fh increased from 6.0 mm to 11.8 mm, the frost time increased by 30.5 %. However, the increase in Fh also brings the penalty of reduced heat transfer rate. The effect of fin depth (Fd) on frost formation performance is small because the frost is mainly deposited in the front part, resulting in the rear fin cannot work efficiently. Fin pitch (Fp) is the most significant structural parameter affecting frosting performance. When Fp increases from 1.6 mm to 4 mm, the frosting time increases by 4 times and frost mass increased by 2.2 times. This is because with the increase of Fp, the frost blocking in the front part can be effectively delayed, and the distribution uniformity of the frost layer is improved. Lower surface temperature and higher humidity ratio significantly promote frost formation and reduce the uniformity of frost distribution. When the inlet temperature is reduced from −5 °C to −8 °C, the frosting time is shortened by 2.15 times, and the frost mass is reduced by 55.7 %. When the relative humidity increases from 76 % to 92 %, the frosting time is shortened by 2.15 times, and the frost mass is reduced by 42.5 %. The air velocity has a minor impact on the growth rate of frost in the front part. However, as the air velocity increases, the uniformity of frost distribution is significantly improved. When the air velocity increased from 1.1 m s−1 to 2.2 m s−1, the mass of accumulated frost increased by 29.5 %. Furthermore, frost thickness and air-side heat transfer coefficient correlations were developed by testing 12 samples. The developed heat transfer coefficient correlation can accurately capture the changing trend of the j-factor. This study provides a fundamental understanding of the frosting characteristics of MCHX and can effectively guide the louvered fin optimization.

The interaction of surface orientation and roughness on nanofluid sub-cooled flow boiling

This experimental study examined the subcooled-flow boiling of water-alumina nanofluids with 0.1 vol % concentration. The study aimed to explore how surface roughness, fluid velocity, and surface orientation influenced the subcooled flow boiling heat transfer (SFBHT). A cross-sectional area of 2 × 3 cm2 and a length of 1.20 m are the dimensions of the plexiglass channel in the experimental setup. A copper heater was embedded at the bottom surface of the channel. The results of the experiment revealed that the surface roughness had a positive effect on SFBHT for horizontal channels, and it depended on the surface configuration. The heat flux increases by 233 % and 98.27 % at low and high fluid velocity (0.5 and 0.9 m/s) by changing the surface roughness from 0.65 to 4.4 μm, respectively. The fluid velocity did not have uniform impacts on SFBHT for higher and lower surface temperatures. When altering the fluid velocity from 0.5 m/s to 0.9 m/s, the heat flux experiences significant variations: The overall heat fluxes are 56.52 % and −35.86 % for rough surface at lower and higher surface temperature, respectively. Depending on whether the surfaces were smooth or rough, the SFBHT performance varied due to the surface configuration. The boiling heat transfer (BHT) performance increased for smooth surfaces but decreased for rough surfaces by changing the surface orientation in both negative and positive directions. The overall heat fluxes increase by about 72.84 % and 66.67 % at smooth surface for both positive and negative inclination, respectively. They are about −32.94 % and −29.82 % at rough surface for both positive and negative inclination, too. The rate of surface roughness’ effects on SFBHT reduces by enhancing the surface angles.

Optimization and Mechanism Study of Bonding Properties of CFRP/Al7075 Single-Lap Joints by Low-Temperature Plasma Surface Treatment

This paper studied favorable low-temperature plasma (LTP) surface treatment modes for Carbon Fiber Reinforced Polymer (CFRP)/Al7075 single-lap joints using complex experimental methods and analyzed the failure modes of the joints. The surface physicochemical properties of CFRP after LTP surface treatment were characterized using scanning electron microscopy (SEM), contact angle tests, and X-ray photoelectron spectroscopy (XPS). The influence mechanism of LTP surface treatment on the bonding properties of CFRP/Al7075 single-lap Joint was studied. The results of the complex experiment and range analysis showed that the favorable LTP surface treatment parameters were a speed of 10 mm/s, a distance of 10 mm, and three repeat scans. At these parameters, the shear strength of the joints reached 30.76 MPa, a 102.8% improvement compared to the untreated group. The failure mode of the joints shifted from interface failure to substrate failure. After low-temperature plasma surface treatment with favorable parameters, the CFRP surface exhibited gully like textures, which enhanced the mechanical interlocking between the CFRP surface and the adhesive. Additionally, the surface free energy of CFRP significantly increased, reaching a maximum of 78.77 mJ/m2. XPS results demonstrated that the low-temperature plasma surface treatment led to a significant increase in the content of oxygen-containing functional groups, such as C-O, C=O, and O-C=O, on the CFRP surface.

Evaluation and development of surface layer scheme representation of temperature inversions over boreal forests in Arctic wintertime conditions

Abstract. In this study, the Noah land surface model used in conjunction with the Mellor–Yamada–Janjić surface layer scheme (hereafter, Noah-MYJ) and the Noah multiphysics scheme (Noah-MP) from the Weather Research and Forecasting (WRF) 4.5.1 mesoscale model are evaluated with regard to their performance in reproducing positive temperature gradients over forested areas in the Arctic winter. First, simplified versions of the WRF schemes, recoded in Python, are compared with conceptual models of the surface layer in order to gain insight into the dependence of the temperature gradient on the wind speed at the top of the surface layer. It is shown that the WRF schemes place strong limits on the turbulent collapse, leading to lower surface temperature gradient at low wind speeds than in the conceptual models. We implemented modifications to the WRF schemes to correct this effect. The original and modified versions of Noah-MYJ and Noah-MP are then evaluated compared to long-term measurements at the Ameriflux Poker Flat Research Range, a forest site in interior Alaska. Noah-MP is found to perform better than Noah-MYJ because the former is a two-layer model which explicitly takes into account the effect of the forest canopy. Indeed, a non-negligible temperature gradient is maintained below the canopy at high wind speeds, leading to overall larger gradients than in the absence of vegetation. Furthermore, the modified versions are found to perform better than the original versions of each scheme because they better reproduce strong temperature gradients at low wind speeds.

MAS:Eu-YAG:Ce composite phosphor converters with excellent thermal performance and enhanced color rendering index for high-power white LDs

Phosphor converters with excellent thermal performance and high color rendering index (CRI) demonstrate vast application prospects in the field of laser diodes (LDs) lighting. Nevertheless, the significant heat accumulation within the converters and the absence of red spectral components pose challenges in achieving both a high saturation threshold and a high CRI for Y3Al5O12:Ce phosphor converters destined for white LDs. In this work, Mg2Al4Si5O18:Eu/Y3Al5O12:Ce (MAS:Eu/YAG:Ce) composite phosphor converters with excellent thermal performance and enhanced CRI were designed and fabricated for reflective laser lighting. Impressively, MAS:Eu/YAG:Ce phosphor-glass-ceramic composites (PGCC) retained a remarkable 97.8 % of the room temperature emission intensity at 150 °C. The reasons for this could be attributed to the strong thermal quenching resistance exhibited by MAS:Eu phosphors, as well as the ultra-thin glass bonding layer of about 150–200 μm. Meanwhile, by integrating the MAS:Eu/YAG:Ce PGCC with a 450 nm laser source, white LD devices operating in a remote excitation mode were fabricated. These white LDs demonstrated an improved CRI of 76 and maintained a low surface temperature of 131.7 °C under an ultra-high laser power density of 47.8 W/mm2 (laser power ∼ 4.70 W). Moreover, the maximum luminous flux and luminous efficiency of the white LDs were 484 lm and 103 lm/W, respectively. Therefore, the design of MAS:Eu/YAG:Ce composite phosphor converters offers a new approach for the development of high-power white LDs.

Understanding the extent of detectability and heat transfer characteristics of hidden defects on metal-based envelopes

Metal hidden defects can either be due to corrosion or voids. The extent of their detectability and heat transfer characteristics, particularly with light-colored surface paints and assembly configurations, have been less explored. Observing surface thermal contrast and rate of temperature change (RTC) during “long-pulse” excitation can detect hidden defects regardless of the metal type, paint color, and assembly configuration. However, results from the active thermography approach only indicate their presence and not their location and type. Corroded layers have a lower surface temperature and RTC due to faster heat transfer, while pitted layers have a higher surface temperature and RTC.

Numerical modelling and experimental validation on the discharging performance of paraffin/graphite matrix composite with various configurations of bulk density and wall temperature

Graphite material in the form of expanded has proven to be an effective material to remedy the low thermal conductivity of paraffin storage medium. The present work focuses on the solidification performance of carbon-based approach via graphite matrix composite with phase change to eliminate the bottleneck of low thermal conductivity issue of phase change materials for thermal energy storage applications beyond the current literature. Paraffin/graphite matrix composites with various bulk density values of 0 kg/m3 (Case 1), 23 kg/m3 (Case 2), 50 kg/m3 (Case 3), 100 kg/m3 (Case 4), and 143 kg/m3 (Case 5) under various operating conditions of wall temperature (Twall: 15 °C, 25 °C, 35 °C, and 45 °C), which mimic real applications' fluid temperature, are performed numerically in detail. The numerical model was validated with experimental outputs performed by the authors. Numerical results show that paraffin/graphite matrix composites have a great potential for the solidification/discharging process to recover the heat stored in the charging/melting period. Uniform and rapid solidification behaviour is achieved with the paraffin/graphite matrix composite in terms of conduction-dominated heat transfer via abundant thermal bridges compared to the pure paraffin case. Higher bulk density values and lower cold surface temperatures present superior performance in solidification rate and thermal energy recovery rate. However, the effect of the bulk density is slowed down with the beyond of certain value of bulk density (100 kg/m3). For 100 kg/m3 (Case 4) at Twall = 15 °C, the heat recovery rate is enhanced by 31.17 times and 3.84 times compared to the 0 kg/m3 and 23 kg/m3. The heat recovery rate of 100 kg/m3 is improved by 350.8 % for Twall = 15 °C in comparison with Twall = 45 °C. The total solidification rate (t = 17.5 min) increased by 90.94 % and 62.94 % for 100 kg/m3 at Twall = 35 °C compared to 0 kg/m3 and 23 kg/m3, respectively.

Analysis and design of fast flow liquid Li divertor for fusion nuclear science facility (FNSF) using coupled plasma boundary and LM MHD/heat transfer codes *

The SOLPS-ITER code is utilized to analyze the boundary plasma associated with a fast-flow lithium (Li) divertor configuration in the fusion nuclear science facility (FNSF) tokamak and identify operational regimes with acceptable divertor and core conditions. Plasma transport from the SOLPS-ITER code has been coupled with a liquid metal (LM) MHD/heat transfer code to model a Li open-surface divertor design and assess its impact on the scrape-off-layer (SOL) and core plasma performance. Simulations with only Neon (Ne) impurity seeding have been conducted to evaluate its impact on meeting FNSF design demands for the divertor and upstream plasma parameters. Simulation results indicate that Ne seeding significantly mitigates divertor heat flux but potentially reduces both upstream electron and main ion density due to fuel dilution. The combined application of Ne seeding and deuterium (D2) puffing is required to satisfy the FNSF design requirements on upstream density ( ne,sepOMP ∼1× 1020 m−3) and divertor energy flux ( q⊥,maxOdiv < 10 MW m−2). D2 puffing plays a role in counteracting upstream density drops and augmenting energy and momentum losses through atomic and molecular processes.The inlet Li flow velocity is systematically varied across a wide range to identify acceptable flows and corresponding LM surface temperatures. This comprehensive analysis identifies the acceptable Li flow parameters, LM surface temperature, and emitted Li fluxes necessary to meet the major design constraints. The emitted Li fluxes exhibit minimal impact on the main plasma at surface temperatures up to approximately ∼525 ∘C, corresponding emitted Li fluxes of up to φ Li ∼2 ×1023 atoms s−1. Uncertainties in the Li emission processes from the surface are also investigated, primarily influencing Li loss in the lower surface temperature range ( <525∘ C), with simulation results indicating a minor impact on the divertor and upstream plasma. Conversely, evaporation predominantly drives the Li loss processes at higher surface temperature ranges ( >525∘ C), contaminating both the divertor and upstream plasma.

Radiation heating tests to evaluate low-emissivity porous ceramics coatings for stand-off thermal protection systems

Diffuse reflection of thermal radiation transfer by Mie scattering can provide a thermal barrier without conversion leading to conduction heat transfer. Applying such a system to internal thermal insulating materials of a stand-off thermal protection systems (TPS) provides an efficient means of preventing thermal radiation transfer. Porous MgAl2O4 ceramics have high thermal resistance because of their low radiation absorption over a wide range from visible to near-infrared wavelengths. For this study, after porous MgAl2O4 ceramics was coated onto a fibrous insulator surface, we investigated its application to stand-off TPS, especially targeting reusable space transportation systems. Direct infrared heating tests were conducted in vacuum. Indirect infrared heating tests were done using graphite as a surface panel in an arc-heated wind tunnel with a high heat flux rate. The apparent thermal conductivity was obtained from the unsteady-state thermal history of the infrared heating experiment using an arc-heated wind tunnel to evaluate the radiation thermal barrier effects of the porous MgAl2O4 ceramics. The low emissivity of porous MgAl2O4 ceramics suppressed heat input and maintained a low surface temperature. Results suggest that thermal radiation transfer was suppressed and that the apparent thermal conductivity of the fibrous insulator was reduced.

Impact of environmental factors on Biomphalaria pfeifferi vector capacity leading to human infection by Schistosoma mansoni in two regions of western Côte d'Ivoire

AbstractBackgroundIntestinal schistosomiasis remains a worrying health problem, particularly in western Côte d'Ivoire, despite control efforts. It is therefore necessary to understand all the factors involved in the development of the disease, including biotic and abiotic factors. The aim of this study was to examine the factors that could support the maintenance of the intermediate host and its vectorial capacity in western Côte d'Ivoire.MethodsData on river physicochemical, microbiological, and climatic parameters, the presence or absence of snails with Schistosoma mansoni, and human infections were collected between January 2020 and February 2021. Spearman rank correlation tests, Mann–Whitney, analysis of variance (ANOVA), and an appropriate model selection procedure were used to analyze the data.ResultsThe overall prevalence of infected snails was 56.05%, with infection reaching 100% in some collection sites and localities. Of 26 sites examined, 25 contained thermophilic coliforms and 22 contained Escherichia coli. Biomphalaria pfeifferi was observed in environments with lower land surface temperature (LST) and higher relative air humidity (RAH), and B. pfeifferi infection predominated in more acidic environments. Thermal coliforms and E. coli preferred higher pH levels. Lower maximum LST (LST_Max) and higher RAH and minimum LST (LST_Min) were favorable to E. coli, and lower LST_Max favored coliforms. The presence of B. pfeifferi was positively influenced by water temperature (T °C), LST_Min, RAH, and precipitation (Pp) (P < 0.05) and negatively influenced by pH, total dissolved solids (TDS), electrical conductivity (EC), LST_Max, and mean land surface temperature (LST). The parameters pH, TDS, EC, LST_Min, LST, and Pp had a positive impact on snail infection, while LST_Max had a negative impact on infection. Only pH had a positive effect on coliform and E. coli abundance. Of the 701 people examined for human schistosomiasis, 73.13% were positive for the point-of-care circulating cathodic antigen (POC-CCA) test and 12.01% for the Kato–Katz (KK) test. A positive correlation was established between human infections and the abundance of Biomphalaria (r2 = 0.879, P = 0.04959).ConclusionsThe results obtained reflect the environmental conditions that are conducive to the maintenance of S. mansoni infection in this part of the country. To combat this infection as effectively as possible, it will be necessary not only to redouble efforts but also to prioritize control according to the level of endemicity at the village level.Graphical

High frequent cyclic ablations of AlSi alloy modified C/C-SiC-ZrB2-ZrC at different temperatures

Modified C/C composites are promising candidates to the advanced piston of internal engine, pantograph slide plate and rapid-fire gun barrel. To understand the corrosion in the working conditions of these thermal components, cyclic ablations of C/C-SiC-ZrB2-ZrC (C/C-SZZ) were carried out in high frequent impacted combustions at different temperatures (700–2300 ℃). Parallel study of AlSi alloy modified C/C-SiC-ZrB2-ZrC (C/C-SZZ-AS) which had lower cost was performed synchronously for comparison. Results indicated that the ablation rates of both the composites went down with decreased temperature while C/C-SZZ-AS presented a faster decline. Compared with C/C-SZZ, the pressure infiltrated AlSi alloy matrix of C/C-SZZ-AS raised the conductivity and specific heat capacity but reduced the emissivity, which led to a lower surface temperature and thermal gradient during ablation. And combined with the better plasticity and toughness of the alloy matrix, C/C-SZZ had stronger ablation resistance below 1500 ℃ in the serious thermal shock. At temperature above 1500 ℃, excessive phase transformation of the AlSi alloy matrix caused more defects and strengthened the mechanical erosion. And then the faster consumption of the AlSi alloy resulted in the greatly worsened ablation property of C/C-SZZ at 2300 ℃.

Analysis of frost layer growth behavior on cryogenic surfaces in ultralow dew point environments by experimental tests and numerical simulations

Maintaining an ultralow dew point is essential for the operation of transonic cryogenic wind tunnels, as it significantly influences aerodynamic characteristics. Even in extremely dry conditions, minute quantities of frost can form on cryogenic surfaces, which compromises data quality. Conducting experiments on frost desublimation in such ultralow dew point environments poses significant challenges due to the demanding experimental conditions. Therefore, this study aimed to explore the desublimation characteristics of cryogenic surfaces in ultralow dew point environments and to address the challenges of experimental investigations under such extreme conditions. Initially, the study experimentally investigated frost formation by assessing the impact of various factors, such as temperature and water vapor content. It was observed that the type of frost formed depended on the water vapor content, and altering the surface temperature influenced the growth region of the frost crystals. The irregular growth of the frost layer on low-temperature surfaces was evident, as temperature markedly affected both the growth rate and the diffusion direction of frost formation. Moreover, the process of trace water frost formation was simulated using a dispersive multiphase model, predicting the frost layer's thickness. The numerical results suggest that the frost layer is micrometers thick, with a minimum thickness of 20 μm. A nonlinear relationship was identified between frost growth and dew point level. This research lays the groundwork for a deeper understanding of desublimation characteristics in ultralow dew point environments and for further investigation of low-temperature heat and mass transfer phenomena.

Adopting a hot film to measure thickness of an ice layer under sweeping wind

Ice can easily form on low-temperature surfaces. To prevent damage caused by undesirable ice, the presence of ice on a surface together with the ice thickness must be determined. This investigation proposed to measure the thickness of an ice layer under sweeping wind using a hot film and two thermocouples. On the basis of the steady temperature gradient in the ice layer and the solved ice-layer surface temperature from the main stream, the ice layer thickness was obtained. The model required the heat flux through the ice layer and the measured steady temperature rise at the ice surface adjacent to the heater. The ice thickness determined by the proposed method was compared with that measured with a microcalliper. In addition, CFD was used to generate temperature data to evaluate the proposed method for the ice layer blown by high-speed winds. The results demonstrated that the proposed method could accurately measure the thickness of the ice layer under wind blowing at 5–300 m/s. The relative discrepancy in the inferred ice thickness with the microcalliper-measured thickness was <10%, and the accuracy of the method increased with the wind speed.

Highly reflective TiO2 layer on AlN substrate: Enabling high quality laser lighting

Phosphors in glass films (PiFs) is considered ideal conversion materials for laser lighting, but heat dissipation issue is the main challenge limiting its development. Therefore, it is urgent to find more excellent heat dissipation materials. Herein, we proposed to use AlN with high thermal conductivity as the substrate, and innovatively introduced TiO2 coating to improve the interface reflection ability and solve the possible problems of shedding and cracking. After a series of optimizations, the LSN PiG-TiO2-AlN (PTA) color converter obtained a high thermal conductivity of 29W m−1k−1 and a low surface temperature. At an input power of 5.2W, the luminous efficiency can reach 175 lm/W and the relative initial intensity can still be maintained by 95.3% at 200 °C. Benefiting from the extremely strong heat dissipation capacity of the AlN substrate, the LSN PTA color converter maintains its relative luminous intensity at 95 % of the initial intensity after 24 h of continuous illumination, which is the best value recorded so far. In addition, LSN PTA is combined with CaAlSiN3:Eu2+ phosphor to achieve high-quality white light with a CRI of 82.5. The above results indicate that LSN PiG-TiO2-AlN color converters have a promising research prospect in the field of laser lighting.

Fabrication of boron nitride reinforced carboxymethyl modified lignin-based re-crosslinkable hydrogel with excellent heat dissipation ability

In this work, a series of re-crosslinkable hydrogels comprising carboxymethylated lignin, PVA and 3-aminophenylboronic acid (3-ABA) was successfully synthesized. Incorporation of polydopamine (PDA) coated boron nitride (PDA@BN) endowed the hydrogel with significantly improved heat dissipation ability, mechanical strength and swelling resistance. The hydrogel containing 20 % of PDA@BN, namely Gel-20 %BN displayed an initial degradation temperature of 131 ℃ and a high thermal conductivity of 3.74 W/m·K, surpassing a plethora of different biobased hydrogels. Gel-20 %BN maintained stable morphology even under continuous heating at 200 ℃ for 15 min and exhibited low surface temperatures without undergoing melting or decomposition, thus demonstrating remarkable heat dissipation capability. The re-crosslinked hydrogel, referred to as Re.Gel-20 %BN, retained similar performance to Gel-20 %BN, maintaining excellent heat dissipation characteristics and stability at 130 ℃ over an extended period. Further investigation is warranted to explore degradation or recovery methods of this hydrogel in reservoir conditions, aiming to minimize the environmental impact of petroleum extraction and contribute to a greener and more sustainable oil production process.

The Dipole Mode of Summer Wet‐Bulb Temperature Over Eastern China and the Possible Mechanisms

AbstractOne prominent mode of the variability in the summer wet‐bulb temperature (WBT) over eastern China exhibits a distinct north‒south dipole pattern. This pattern demonstrates a positive center in northern China (NC), while a negative center is observed in southern China (SC). Our results indicate that the dipole mode of WBT could be partially ascribed to the impact of spring snow anomalies in eastern Europe–western Siberia (EEWS). The reduction in the snow depth, coupled with dry soil conditions, enhances the surface heat flux and consequently leads to an increase in the near‐surface air temperature. The signal of soil moisture could persist from spring to summer, stimulating the generation of zonal Rossby waves. Consequently, the significant wave flux anomalies propagate from EEWS downstream and influence the atmospheric circulation over eastern China. These patterns play a role in the increase in the surface air temperature and moisture accumulation over NC, ultimately leading to the establishment of the dipole mode of WBT over eastern China in summer. Further analysis indicates that the atypical low sea surface temperature in the tropical Ocean, induced by the El Niño‐Southern Oscillation, establishes a climatic context favorable for the persistence of an anomalous cyclone in the Northwest Pacific (NWP) throughout the summer season. The strengthened convection over the NWP and SC induces a dipole pattern of atmospheric circulation by stimulating a meridional wave train. This pattern creates favorable temperature and moisture conditions, contributing to the development of the dipole mode of the summer WBT across eastern China.

Experimental Analysis of the Improvement of Heat Transfer in Tube Heat Exchangers via Passive Flow Generators Using Wire Coil Inserts

Abstract Due to their high performance and low-cost demands, internally treated tube heat exchanger surfaces are one of the passive heat transfer enhancements that have caught the industry&amp;#39;s attention. At bulk temperatures of 30 &amp;#176;C, an experiment for the insertion of 1 mm and 0.5 mm wire coils with a constant pitch length of 8 mm was carried out in this study. The results on the improvement of heat transfer, including the velocity profile, Nusselt number, friction factor, and thermal enhancement efficiency, were significant. Based on a lower surface temperature recorded beyond the uncertainty value, the results demonstrated an improvement in heat transfer for smaller diameters of wire coil inserts. Interestingly, this improvement is concentrated at low Reynolds numbers, indicating that there may be a point at which an increase in wire thickness does not necessarily result in an equivalent improvement in heat transfer. For both wire thicknesses, a Nusselt number increase of up to 5 times was observed. The friction factor penalty, however, varies depending on the wire thickness, with a higher magnitude (3.2-fold increase) obtained for 1mm as opposed to a 1.8-fold increase for the lower counterpart. This distinction results in the 0.5 mm coil insert gaining better overall performance with an average of 2.2 for the thermal performance ratio, further solidifying the advantage of this technique for enhancing heat transfer in conduits.