Temperature Decrement Research Articles

Decoding the Early Universe: Exploring a Merger Scenario for the High-Redshift Cluster JKCS041 using Numerical Models

Abstract JKCS041 (z = 1.8) is one of the most distant galaxy cluster systems known, seen when the Universe was less than 4 billion years old. Recent Sunyaev-Zeldovich (SZ) observations show a temperature decrement that is less than expected based on mass estimates of the system from X-ray, weak gravitational lensing and galaxy richness measurements. In this paper we seek to explain the observables - in particular the low SZ decrement and single SZ peak, the projected offset between the X-ray and SZ peaks of ≈220 kpc, the gas mass measurements and the lensing mass estimate. We use the GAMER-2 hydrodynamic code to carry out idealized numerical simulations of cluster mergers and compare resulting synthetic maps with the observational data. Generically a merger process is necessary to reproduce the observed offset between the SZ and X-ray peaks. From our exploration of parameter space, seen a few tenths of a Gyr after first core passage, two components with total mass of ≈2 × 1014M⊙, mass ratio of ≈2:3, gas fraction of 0.05 − 0.1 and Navarro, Frenk and White (NFW) mass density profile concentrations c≈5 are scenarios that are consistent with the observational data. For consistency with the SZ and X-ray measurements, our simulations exclude total mass in excess of ≈3 × 1014M⊙, primarily based on the SZ signal. The mass ratio is constrained by the SZ-X-ray offset and magnitude of the SZ signal, ruling out systems with equal and vastly different masses.

Co-combustion of municipal sewage sludge and food wastes-derived anerobic digestates: Combustion characteristics, HCl/NO/SO2 emission and ash behaviors

Co-combustion of sewage sludge (SS) and food wastes-derived anerobic digestate (AD) is a promising way of waste-to-energy. Therefore, it is crucial to examine their combustion performance, ash behaviors, and gaseous pollutants emissions during the combustion of AD-SS blends using a thermogravimetric analyzer and a tube furnace combustion system. Results show that obvious interactions between AD and SS are observed in their co-combustion process. In terms of comprehensive combustion index, co-combustion can improve their combustion performance with the decrement of burnout temperature and enhanced combustion reactivity. Higher blending ratio of AD favors the increment of their ash fusion temperature, i.e., from 1109 to 1403 °C for deformation temperature due to the formation of high melting point minerals (i.e., Ca9Fe(PO4)7, 2CaO·Al2O3·SiO2). Significant in-situ reduction of NO and HCl as well as self-desulfurization is observed during the combustion of AD-SS blends. Compared to the theoretical values, the emission amount of HCl, NO, and SO2 is reduced by 0.13, 1.39, and 0.35 mg·g−1, respectively at 850 °C and blending ratio of AD to SS = 0.75:0.25. These phenomena are associated with the reducing environment and reducing substances by their high volatiles as well as the abundant minerals such as CaCO3 and Fe2O3 in AD and SS. However, high combustion temperature is unfavorable for chlorine fixation. This work provides a better understanding of their thermal behaviors, ash characteristics, and gaseous pollutants emission characteristics to realize their stable and clean incineration.

Effect of Hydrogen Addition on Soot Reduction in Diffusion Flames

This study explores the effects of hydrogen addition on soot reduction in methane-air diffusion flames, employing computational analysis coupled with chemical equilibrium and k-epsilon combustion turbulence models. By varying the fuel mixture with hydrogen mass percentages ranging from 0% to 11%, alterations in flame behaviour were observed. Results revealed a notable increase in maximum flame temperature at 1.3% hydrogen addition, attributed to enhance combustion efficiency, while subsequent additions led to temperature decrements due to dilution effects. Concurrently, soot production exhibited a general decrease, with reductions quantified up to 96.7% compared to baseline conditions, primarily due to improved oxidation and decreased carbon content. Additionally, the position of maximum flame temperature and soot mass fraction shifted along the axial direction owing to hydrogen's higher flammability compared to methane-air diffusion. These findings offer insights into optimizing flame characteristics for reduced particulate matter emissions, emphasizing the potential of hydrogen addition in mitigating soot formation in diffusion flames.

Thermal energy storage performance of biaxial voided RCC roof slab integrated with macroencapsulated PCM for passive cooling of buildings

Building space heating and cooling power consumption is growing due to population and economic growth. Integrating phase change materials (PCMs) into various building envelope components is being explored to enhance thermal energy storage capacities. Specifically, roofs exposed to direct sunlight significantly promote thermal energy transfer to the interior, increasing the space heating and cooling requirements. In this study, thermal energy storage performance of a biaxial voided roof slab integrated with PCM is experimentally investigated under ambient conditions and compared with a normal reinforced concrete (RCC) without PCM. PCM selection, characterization, and metal void former development are performed, followed by macroencapsulation and integration into the roof slab. Thermal performance measures are evaluated, including temperature profile, heat flux, thermal load, time lag, and decrement factor. Financial viability indicators such as electricity cost savings, payback period, and CO2 emissions savings are also assessed. The results show PCM integrated biaxial voided roof slab reduces interior temperature by upto 7.2 °C during sunny hours, heat transfer to the interior by upto 60.6 %, and thermal load by upto 54 %. In addition, considering heating and cooling, it offers an average daily saving of 0.06 USD/kWh/m2 and a payback period of about 5.7 years. Further, it gives CO2 emissions savings of upto 13.7, 12.3, and 4.3 kgCO2/kWh for lignite-, coal-, and natural gas-fired power plants. Furthermore, its mean time lag is 4.2 h, with a decrement factor of 0.75 compared to 3.9 h and 0.85 for the normal RCC unit. The study makes significant contribution to knowledge by providing a unique, simple yet highly effective PCM macroencapsulation integration technique for roof slabs and insights into its thermal performance under the hot weather conditions.

Bipolar endo-epicardial RF ablation: Animal feasibility study

BackgroundBipolar radiofrequency ablation (B-RFA) is a method used to treat the arrhythmia substrate resistant to unipolar ablation. Few studies have addressed endo-epicardial B-RFA. ObjectiveThe aim of the study was to evaluate chronic lesions resulting from endo-epicardial B-RFA and to determine optimal settings for such procedures in an animal model. MethodsIn 7 pigs, up to 5 radiofrequency applications per animal were performed with 2 electrodes placed on both sides of the left ventricular free wall. Current was delivered for 60 seconds by a generator dedicated for B-RFA with power settings of 25, 30, 35, 40, and 50 W. ResultsAt 12 weeks after ablation, 31 lesions were assessed. Their maximal cross-sectional area ranged from 7.2 to 68 mm2 and correlated with total power delivered (r = 0.53), with temperature increment at the endocardial catheter (r = 0.65), and inversely with temperature decrement at the epicardial catheter (r = 0.54). For power values between 30 and 40 W, the lesion area did not differ significantly (P = .92). Lesion depth ranged from 1.9 to 11 mm and correlated with impedance decrement (r = 0.5). Lesions were transmural in 8 cases. Lesion depth/wall thickness ratio was on average 0.6 ± 0.3, with the smallest value for 25 W (0.5 ± 0.3) and the largest for 50 W (0.8 ± 0.3). Steam pops occurred at a power range of 30–50 W, with an incidence of 1 in 5 applications, with 1 case of fatal tamponade at 40 W. Impedance decrement, endocardial catheter temperature increment, and endocardial electrogram amplitude decrement were greater during applications with steam pops. ConclusionChronic lesions resulting from endo-epicardial B-RFA appear smaller and less often transmural compared with acute lesions described in the literature. The incidence of steam pops during endo-epicardial B-RFA is relatively high even at low powers.

Volume viscosity of inhomogeneous fluids: a Maxwell relaxation model

Volume viscosity is one of the most important and fundamental parameters in hydrodynamics. It measures the momentum loss caused by a volume deformation rather than shape deformation. So it is closely related to numerous phenomena in fluid dynamics. However, most of the existing related researches focus on the bulk fluids, but there is still a lack of in-depth understanding of the bulk viscosity of inhomogeneous fluids. In this work, a novel theoretical method is proposed for the inhomogeneous volume viscosity in the framework of Maxwell viscoelastic theory. In this proposal, the local relaxation time is calculated by using the viscous and elastic properties of the bulk fluids. Accordingly, the inhomogeneous volume viscosity can be obtained by combining the calculations of the local relaxation time and the local relaxation modulus. It is advantageous in the theoretical sense over the conventional LADM, because it takes into account the underlying correlation much better. On the one hand, the local infinite-frequency modulus is more accurate. On the other hand, by using an appropriate weight function to calculate the weight, the correlation effect can be better considered . As an application, the volume viscosity of the confined Lennard-Jones fluid in slit pore is investigated, and the influences of bulk density, temperature, pore width and adsorption strength are calculated and analyzed. The results indicate that these factors can significantly modulate the volume viscosity of the confined fluid. Specifically, the positive correlation between the volume viscosity and the local density leads to the oscillation of viscosity profile in the pore. Besides, the occurrence of capillary condensation in the cases of lower density and lower temperature makes the inhomogeneous viscosity rather different from that of bulk gaseous phase. Further, this study shows that the inhomogeneous volume viscosity usually increases with temperature decreasing, or with adsorption strength increasing. This is again the result of its dependence on the fluid structure in the pore. Furthermore, the influence of pore width on the inhomogeneous volume viscosity indicates that the excluded volume plays a decisive role. This can be attributed to the fact that it exerts a direct influence on the deformation of the fluid. Moreover, comparison between the volume and shear viscosity is also conducted and analyzed. In general, this study can be beneficial to deepening the understanding of volume viscosity in the confined fluids, and can provide reliable theoretical support for studying related issues in hydrodynamics.

Effect of Mg doping at Fe/Cr site on magnetic and optical properties of Gd2FeCrO6 double perovskite

The influence of Mg doping on structural, magnetic and optical characteristics of Gd2FeCrO6, Gd2Fe0.75Mg0.25CrO6 and Gd2FeCr0.75Mg0.25O6 double perovskites has been systematically investigated. The monoclinic crystal structure with the P21/n space group is confirmed by powder X-ray diffraction data. From the scanning electron microscopy graphs, we noticed few nearly spherical and dumbbell-shaped grains for all compounds with an average grain size of about 76 - 85 nm. The magnetic studies demonstrated the presence of a weak ferromagnetic transition with antiferromagnetic background at low temperatures for all the samples. A decrement in the transition temperature of Gd2FeCrO6 (TC = 8.14 K) is observed on Mg doping, which is due to the smaller ionic radii of Mg at the Fe/Cr site in Gd2Fe0.75Mg0.25CrO6 and Gd2FeCr0.75Mg0.25O6 double perovskites. By analyzing the UV–visible spectroscopic absorption data, direct band gaps around 3 eV are concluded for pure and Mg doped Gd2FeCrO6 double perovskites, validating their application in wastewater photocatalysis.

The CMB Cold Spot as predicted by foregrounds around nearby galaxies

Context. The non-Gaussian Cold Spot surrounded by its hot ring is one of the most striking features of the cosmic microwave background (CMB) and has generated significant attention in the literature. It has been speculated that either new physics or the Integrated Sachs-Wolfe effect induced by the presence of a cosmic void at relatively high redshift could account for the observations. Aims. Here, we investigate if the newly discovered systematic decrease in the CMB temperature in the neighbourhood of nearby galaxies may create such a strong temperature depression. In particular, we note that the largest galaxy group complex in the local Universe, the Eridanus super-group with its neighbouring groups, is in the Cold Spot area. Our goal is to analyse observational galaxy data to characterise the neighbourhood of the Cold Spot, explore the properties of these galaxies, and thereby make a prediction of the galaxy induced CMB temperature decrement in this region. Methods. We used the Planck SMICA maps, and as foreground tracers, galaxies from the publicly available observational catalogues: 2MRS, 6dF, and HIPASS, which include information on redshifts, positions, magnitudes, and other astrophysical characteristics. We applied previously explored mean temperature profile shapes to model the expected temperature decrement from the galaxies in the Cold Spot area. Results. Even after correcting for the mean low temperature of the Cold Spot region, we find that the temperature decrement around galaxies is significantly stronger than the mean decrement in other parts of the sky. We discuss whether this could be attributed to the fact that the Cold Spot area coincides with one of the regions populated by the most HI deficient galaxies. Modeling the foreground temperature profile that is mainly associated with spiral galaxies in this location, we find a particularly strong temperature decrement due to the presence of the late-type overabundant largest group complex in the nearby universe. A Cold Spot shape that largely overlaps with the CMB Cold Spot is observed. Conclusions. We conclude that the coincidence of the only nearby spiral-rich group complex located in the Cold Spot region, and the success of the modelling performed, adds strong evidence to the existence of a local extragalactic foreground that may account for the observed temperature depression, alleviating the tension with the Gaussian field that is otherwise expected in the CMB.

Synthesis of highly grafted MWCNTs with epoxy silane to improve curing, thermal and mechanical performances of epoxy nanocomposites

Hydrophobic CNTs have weak interfacial interactions to epoxy matrix which causes their agglomeration and significant decline in the thermal/electrical/mechanical of epoxy nanocomposites. In this research, multi walled carbon nanotubes (MWCNTs) were acid treated at three different times to prepare nanotubes with the highest functional groups on surface. Thereafter, the best functionalized nanotubes were surface modified using 3-glycidyloxypropyltriethoxysilane (GPTES) at different concentrations to prepare GPTES@MWCNTs nanoparticles with the highest silane grafting content. The unmodified, acid treated and GPTES@MWCNTs were characterized carefully. The pure, functionalized and silane modified nanotubes were then applied to epoxy resin at 0.5 to 2 wt% and the mechanical, curing, thermo-mechanical and morphological features of the nanocomposites were assessed. It was declared that the unmodified MWCNTs (at 0.5 wt%) caused about 35 % decline in enthalpy of curing and 24 °C decrement in decomposition temperature of the epoxy polymer. However, the modified nanotubes enhanced the curing enthalpy and decomposition temperature of the polymer by 95 % and 31 °C compared to the unmodified nanocomposites, respectively. It was also found that the GPTES@MWCNT containing nanocomposite (at 0.5 wt%) showed enhanced tensile, flexural and compressive strengths by 69, 106 and 34 % compared to the pristine epoxy sample and 47, 73 and 25 % compared to the unmodified nanocomposite, respectively. It also caused 54 % and 13 °C improvement in the storage modulus and Tg compared to the unmodified nanocomposite.

Achieving enhanced cryogenic toughness in a 1 GPa grade HSLA steel through reverse transformation of martensite

The effect of microstructure on crack resistance and cryogenic toughening in a 3.5 wt% Ni high-strength low-alloy (HSLA) steel was investigated. Multistage heat treatments involving quenching (Q), lamellarization (L), and tempering (T) were applied to prepare the HSLA steels with various microstructures, focusing on the reverse transformation and reconfiguration of martensite, as well as its influence on impact crack formation and propagation behavior by multi-scale characterizations. The results indicate that lamellarization treatment has little influence on tensile properties, but significantly improves impact toughness in the QL and QLT specimens, which exhibit over 30 % increment in Charpy V-notch (CVN) absorbed energy Et tested in range from RT to −196 °C, over 25 °C decrement in ductile-brittle transition temperature (DBTT), and much higher crack propagation energy Ep and higher ratio of Ep/Et, as compared with the as-quenched (AQ) and QT specimens. The lamellarization treatment also contributes to a significant refinement effect on martensitic block size, caused by fresh martensite transformation from the reversed austenite, resulting in an increment in high angle grain boundaries (HAGBs), with introduction of a small amount of retained austenite (RA) as well. Therefore, the impact crack resistance and cryogenic toughness is improved in specimens processed with lamellarization treatment, due to the enhancement in crack deflection and hindering effect of the HAGBs, as well as toughening effect by in situ austenite-to-martensite transformation of the RA. Based on the present study, a 1 GPa grade HSLA steel with high ductility and excellent cryogenic toughness can be produced.

Investigation of heat transfer augmentation and friction factor in twisted tape-based earth-to-air-heat exchanger: a CFD-based analysis

Earth air heat exchangers (EAHES) are an innovative way to heat and cool buildings by utilising the earth’s natural temperature. Utilizing twisted tape (TT) as an enhancement technique in the EAHE can significantly boost heat transfer passively. This study employs CFD simulations (Ansys Fluent 2022) with SST turbulence model for a fixed Reynolds number range (20,000–52,000). The Twist Ratio (y/w), representing the number of turns of TT inserts, is a critical roughness parameter. The ground temperature across whole soil domain is held constant at 26.7°C. Numerical results are validated against available data showing a close match, particularly at the outlet temperature. Maximum decrement in temperature at exit of EAHE for smaller twist ratio(y/w) is 19.53% as compare from conventional (plain pipe) EAHE for cooling mode. Nusselt number increment of the current design is 50.41% more than the previous design with TT inserts of Re = 51344, number of turns(y/w) = 15, respectively and for friction factor the maximum increment is 2.253 times without TT inserts EAHE at Re = 20573 for 15 turns, respectively. The maximum thermal performance factor improves by 1.19 times with TT inserts in EAHE, achieved at 15 turns and a Reynolds number of 51,344. Abbreviations: EAHE: earth to air heat exchanger; TT: twisted tape; LES: Large Eddy Simulation; RANS: Reynolds-Averaged Navier-Stokes.

Whole-infrared-band camouflage with dual-band radiative heat dissipation

Advanced multispectral detection technologies have emerged as a significant threat to objects, necessitating the use of multiband camouflage. However, achieving effective camouflage and thermal management across the entire infrared spectrum, especially the short-wave infrared (SWIR) band, remains challenging. This paper proposes a multilayer wavelength-selective emitter that achieves effective camouflage across the entire infrared spectrum, including the near-infrared (NIR), SWIR, mid-wave infrared (MWIR), and long-wave infrared (LWIR) bands, as well as the visible (VIS) band. Furthermore, the emitter enables radiative heat dissipation in two non-atmospheric windows (2.5–3 μm and 5–8 μm). The emitter’s properties are characterized by low emittance of 0.270/0.042/0.218 in the SWIR/MWIR/LWIR bands, and low reflectance of 0.129/0.281 in the VIS/NIR bands. Moreover, the high emittance of 0.742/0.473 in the two non-atmospheric windows ensures efficient radiative heat dissipation, which results in a temperature decrement of 14.4 °C compared to the Cr reference at 2000 W m−2 input power density. This work highlights the role of solar radiance in camouflage, and provides a comprehensive guideline for developing multiband camouflage compatible with radiative heat dissipation, from the visible to LWIR.

Radio-continuum decrements associated to shadowing from the central warp in transition disc DoAr 44

ABSTRACT Warps have often been used to explain disc properties, but well-characterized examples are important due to their role in disc evolution. Scattered light images of discs with central gaps have revealed sharp warps, such that the outer rings are shadowed by tilted inner discs. The near-infrared intensity drops along the ring around T-Tauri star DoAr 44 have been interpreted in terms of a central warp. We report new ALMA observations of DoAr 44 in the continuum at 230 and 350 GHz (at ∼10 au), along with a new epoch of Spectro Polarimetric High-contrast Exoplanet REsearch (SPHERE)/Infrared Dual-band Imager and Spectrograph differential polarized imaging taken during excellent weather conditions. The ALMA observations resolve the ring and confirm the decrements proposed from deconvolution of coarse 336 GHz data. The scattered light image constrains the dips, which correspond to a misaligned inner disc with a relative inclination ξ = 21.4 $^{+6.7}_{-8.3}$ deg. The SPHERE intensity profile shows a morphological change compared to a previous epoch that may be interpreted as a variable orientation of the inner disc, from ξ ∼ 30 deg to ξ ∼ 20 deg. The intensity dips probably correspond to temperature decrements, as their mm-spectral index, $\alpha ^{230 \textrm {GHz}}_{350 \textrm {GHz}} \sim$ 2.0 ± 0.1, is indicative of optically thick emission. The azimuth of the two temperature decrements are leading clockwise relative to the infrared-dips, by η = 14.95 deg and η = 7.92 deg. For a retrograde disc, such shifts are expected from a thermal lag and imply gas surface densities of Σg = 117 ± 10 g cm−2 and Σg = 48 ± 10 g cm−2. A lopsided disc, with contrast ratio fr = 2.4 ± 0.5, is also consistent with the large continuum crescent.

Synthesis and evaluation of the cobalt-promoted NiO/CaO.2Al2O3 catalysts in CO2 methanation reaction: Effect of different promoters

This work is concentrated on designing of CO2 methanation process over nickel-based catalysts doped by different promoters (CuO, Cr2O3, Co3O4, Fe2O3, and MnO2) supported on CaO.2Al2O3 powder. The CaO-Al2O3 powder was fabricated by mechanochemical method, and catalysts were synthesized via a wet impregnation procedure. The characterization properties of all samples were tested by XRD, BET, TPR, FESEM, and EDS-mapping analyses. The optimum amount of NiO was selected at 10 wt% along with CaO:Al2O3 as support with the molar ratio of 1:2. The Co-doped catalyst showed the lowest pore size (9.4 nm) and the highest surface area (106 m2.g−1) among the promoted catalysts. The results exhibited that the Co3O4(3)-NiO(10)/CaO.2Al2O3 catalyst possessed superior catalytic performance in the CO2 methanation reaction. The results illustrated that the increase in cobalt oxide percentage up to 3 wt% improved catalytic performance. However, further augmentation in the Co3O4 from 3 to 7 wt% diminished the specific surface area. According to the performance tests, carbon dioxide conversion and methane selectivity were 83.1% and 99.5% at 450 °C under operating conditions (GHSV = 18,000 ml.gcat−1.h−1 and H2:CO2 = 4:1) over this catalyst. The processing conditions including calcination temperature, reduction temperature, GHSV, feed ratio, and long-term stability test were also examined over the selected catalyst. Outcomes revealed that CO2 conversion increased with a decrement in calcination temperature from 650° to 450°C. Also, chosen catalyst reduced at 650 °C showed the highest performance. Besides, catalytic performance enhanced by raising feed ratio (H2:CO2) from 2:1 to 5:1 and decreased with augmentation of GHSV from 12,000 to 30,000 ml.gcat−1.h−1. Moreover, Co3O4(3)-NiO(10)/CaO.2Al2O3 catalyst possessed high stability during 14 h time on stream.

Field experimental test and performance analysis of a novel hybrid CdTe PV glass module integrated with phase change materials

In this study, a novel hybrid semi-transparent CdTe PV glass module integrated with a middle phase change materials (PCMs) layer is proposed and fabricated. Detailed fabrication process of the CdTe-PCM PV glass module (CdTe-PCMG) is illustrated. A field experimental test rig was constructed to evaluate and compare its comprehensive performance with the single CdTe PV glass (CdTe-SG). Several groups of continuous full-day experiments were conducted under different ambient condition days in Hefei. Main results are: (1) Utilization of PCM can effectively improve the PV module's electrical output, with an average daily increase ratio of 6.67% on the daily total electricity generation compared with SG among the ten investigated sunny days. Daily average ηe were respectively 7.63% and 8.31% for SG and PCMG; (2) PCM has realized effective cooling to the PV glass, with the maximum temperature differences between SG's and PCMG's external PV surface of 16.56 °C, 26.32 °C and 18.60 °C for the three groups of experiments. Average temperature decrement factors of the PCMG external surface were respectively 0.76, 0.72 and 0.67 compared with SG. This novel PCMG module has a promising application potential in energy-saving and indoor thermal comfort improvement when applied as building window.

A possible common explanation for several cosmic microwave background (CMB) anomalies: A strong impact of nearby galaxies on observed large-scale CMB fluctuations

Context. A new and hitherto unknown cosmic microwave background (CMB) foreground has recently been detected. A systematic decrease in CMB temperatures around nearby large spiral galaxies points to an unknown interaction with CMB photons in a sphere up to several projected megaparsecs around these galaxies. Aims. We investigate to what extent this foreground may impact the CMB fluctuation map and create the so-called CMB anomalies. Methods. Using the observed temperature decrements around the galaxies, and making some general assumptions about the unknown interaction, we propose a common radial temperature profile. By assigning this profile to nearby galaxies in the redshift range z = [0.004, 0.02], we created a foreground map model. Results. We find a remarkable resemblance between this temperature model map, based on nearby galaxies, and the Planck CMB map. Compared to 1000 simulated maps, we find that none of them show such a strong correlation with the foreground map over both large and small angular scales. In particular, the quadrupole, octopole, and ℓ = 4 and ℓ = 5 modes correlate with the foreground map to a high significance. Furthermore, one of the most prominent temperature decrements in the foreground map coincides with the position of the CMB cold spot. Conclusions. The largest scales of the CMB, and thereby the cosmological parameters, may change significantly after this foreground component is properly corrected. However, a reliable corrected CMB map can only be derived when suitable physical mechanisms are proposed and tested.

Effect of phase change cooling vest on related thermal regulation factors in moderately hot environments

Phase change cooling vests (CV) are mostly developed to improve people's thermal comfort in warm or hot environments. In this paper, the effect of a CV on related thermal regulation factor was studied. Physiological parameters (including skin temperature, sweat rate, fingertip blood flow, and ear canal temperature) and conductive heat flux were measured in three air temperature conditions (27, 29, and 31 °C). Results found that compared with no cooling vest (NCV) conditions, the maximum decrement in local skin temperature for the back and chest with CV was 2.5 and 2.1 °C, and for the mean skin temperature (Tmsk), the decrement was 0.8 °C. Simultaneously, the mean conductive heat flux of the back and chest with CV was significantly increased by 28.3% and 234.4%, respectively (p < 0.01). The total sweat rate (SR) of subjects using CV was decreased by 14%–18%. The SR of the forehead was positively correlated with the overall thermal sensation and comfort. With the use of CV, the fingertip blood flow (Qfinger) tended to decrease. As the experimental temperature elevated, the impact of the CV on Qfinger was more effective. However, there was no difference in Qfinger and ear canal temperature between the CV and NCV conditions. The results provided a better understanding of the improving effect of CV on human thermal comfort from the perspective of thermal regulation.

Thermal analysis of concrete bricks-embedded phase change material: A case study under hot weather conditions

This research experimentally examines the thermal behaviour of concrete brick-based PCM layer/capsules during severe hot summer days in southern Iraq. Three bricks were fabricated in which one brick was integrated with a PCM layer (BL) and another integrated with PCM capsules (BC), while the third was left bare without PCM (BR) for comparison. The thermal performance of bricks was assessed considering the inner and outer surface temperature difference, decrement factor, time lag and average surface temperature fluctuation reduction. Besides, the mechanical strength decline of each brick was investigated to show their applicability in real constructions. Experimental results designated that BL and BC performed better than BR, in which the temperature across the brick was shaved by up to 5 °C with a 30–60 min time lag. Generally, BL exhibited slightly better thermal performance than BC; nonetheless, it showed a sharp decline in compression strength. Conclusively, the brick-based PCM layer was thermally better than that-based PCM capsules, but the latter has superior mechanical properties.

Optical cooling at the optimal SPR angle of a glass–ITO–CdSe/ZnS(QDs) interface

In practice, cooling effects must dominate over heating associated with nonradiative decay and multiphonon emission to attain optical cooling in semiconductors. Although quantum confinement nanostructures (e.g., quantum dots [QDs]) have been used to reduce the self-absorption of anti-Stokes luminescence, their low quantum efficiency precludes high light extraction, thus reducing net cooling generation. Superficial plasmon resonance (SPR) generated in some metal–dielectric interfaces provides an efficient way to tune and enhance the optical properties and photoluminescence (PL) of QDs. In this work, the optimal SPR angle (θSPR) was used to enhance the PL of CdSe/ZnS core–shell QDs, and hence their cooling properties, in a glass–indium tin oxide–QD interface. Three excitation wavelengths (λexc = 405, 532, and 640 nm) were used to evaluate the cooling properties. The best results were obtained when λexc = 640 nm. A PL increment and temperature decrement (Δt) of 2-fold and 4 °C, respectively, were obtained at θSPR in 50 min due to the generation of anti-Stokes PL by the QDs and the enlargement of such generated PL because of the presence of the SPR effect at the interface.

Experimental investigation on the ethane pulsating heat pipe under asymmetric heating

A three-dimensional cylindrical copper pulsating heat pipe (PHP) with ethane as the working fluid is designed. Experiments are conducted to study the thermal performance of the ethane PHP under the asymmetric heating mode. The evaporation section is divided into two parts: the left part and the right part. The left and right evaporators are provided with different heat inputs to study the temperature oscillation and heat transfer performance. Three cases are carefully studied: no heat input on the left evaporator, the fixed heat input on the left evaporator, and the fixed total heat input. Experiments are also conducted on the PHP operated in the temperature range of −100 ∼ −20 °C. Results demonstrate that when no heating on the left evaporator, the minimum right heat input to form the circulating flow is 40 W. The maximum allowable heat flux is 88419.41 W/m2, which is the 200 W heat input. When there is no heating on the left evaporator, as the heat input on the right side increases, the temperature oscillation experiences: small oscillation, severe fluctuation, stable operation, slight fluctuation, stable operation, and intermittent fluctuation. The heating on the left evaporator relieves the stagnation caused by the movement lag of the working fluid and promotes the flow motion. When the total heat input is fixed, the overall thermal resistance of the PHP is little influenced by the exchange of the heat input of the left and right evaporators, instead, it is decided by the amount of the total heat input. The decrement of the working temperature improves the amplitude of the temperature oscillation but also results in the degradation of the thermal performance of the PHP. The optimal working temperature is discovered to be −40 °C.