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Air‐sea interaction in late boreal winter is studied over the extratropical North Atlantic (NA) during 1960–2020 by examining the relationship between sea‐surface temperature (SST) and total turbulent heat flux (THF). The two quantities are positively correlated on interannual timescales over the central‐midlatitude and subpolar NA, suggesting the atmosphere on average drives SST and THF variability is independent of SST. On decadal timescales and over the central‐midlatitude NA the correlation is negative, suggesting ocean processes on average drive SST and THF variability is sensitive to SST. The correlation is positive over the subpolar NA. There, interannual and decadal THF variability is governed by the North Atlantic Oscillation (NAO). During the major late 20th and early 21st century SST increase in the subpolar NA diminishing oceanic heat loss associated with a weakening NAO was observed. This study suggests that the atmosphere is more sensitive to SST over the central‐midlatitude than subpolar NA. Plain Language Summary: The relationship between the sea‐surface temperature (SST) and air‐sea heat exchange, is studied over the extratropical North Atlantic (NA) for late boreal winter during 1960–2020. This relationship provides information about the roles of atmospheric and oceanic processes in driving SST variations. We consider two regions, the central‐midlatitude (35°N–50°N) and subpolar (50°N–60°N) NA. Over both regions, the atmosphere tends to drive the variations on the short interannual timescales. On the longer decadal timescales and over the central‐midlatitude NA, oceanic processes tend to drive the SST anomalies that in turn influence the air‐sea heat exchange. Air‐sea heat exchange over the subpolar NA is mostly driven by the North Atlantic Oscillation on interannual and decadal timescales, which is the leading mode of internal atmospheric variability in winter. This study suggests that the atmosphere is more sensitive to SST over the central‐midlatitude than subpolar NA. Key Points: Regional variation in the nature of air‐sea interaction over the extratropical North Atlantic (NA) north of 35°NTimescale dependence in relationship between sea‐surface temperature (SST) and turbulent heat flux over the central‐midlatitude NAThe atmosphere is more sensitive to SST variability over the central‐midlatitude than subpolar NA [ABSTRACT FROM AUTHOR]

• A novel SRBC/ARC using CO 2 -based mixtures as working fluids is investigated. • Thermo-economic comparative studies are carried out for the novel system. • The key parameters are identified that determine the system performance. • The precoolers of the systems are predesigned using a segmented design method. CO 2 –Kr (mass fraction of 0.755/0.245) has enormous development potential as a Brayton cycle working fluid. To reduce the limitation of ambient temperature on the supercritical CO 2 –Kr Brayton cycle, this paper develops a thermo-economic model of a coupled system of a supercritical recompression Brayton cycle (SRBC) and an absorption refrigeration cycle (ARC). The ARC utilizes the waste heat from the SRBC to further reduce the inlet temperature of the main compressor. The influences of ammonia–water ARC and LiBr–H 2 O ARC on the coupled system performance are analyzed and compared. The variations of the thermo-economic performance of the systems under different operating parameters are explored, and the impact of each variable on the cycle efficiency and cost is evaluated using a multiple regression linear method. From the perspective of predesign, mathematical models of precoolers with different systems are established. The results show that the coupled ARC improves the cycle efficiency of SCO 2 –Kr BRC by 9.76 %, reduces system cost by 27.01 % when ambient temperature is 25 °C, in addition, the heat loss and size of the precooler is greatly reduced. The inlet temperature and pressure ratio of the turbine are found to be the dominant parameters in determining the thermo-economic performance of the system. [ABSTRACT FROM AUTHOR]

• Temperature-distributed refrigeration power is transferred from inside a regenerator. • Temperature-distributed transfer coefficient (TTC) increases with discrete points. • Internal DC transfer method eliminates radial thermal resistance and improves TTC. • Combining DC flow and discrete method increases TTC up to 90 %. • TTC of these new methods is 1–2 times higher than previous transfer methods. The temperature-distributed regenerative refrigeration cycle utilizes the real-gas properties to generate the temperature-distributed refrigeration power and improves the cooling performance and liquefaction rate of cryogenic gases. The temperature-distributed refrigeration power is distributed in the volume of the regenerator. It is challenging to transfer this distributed refrigeration power, and the regenerative heat loss is usually inevitable. The transfer process of the temperature-distributed refrigeration power is studied in this paper. A comprehensive investigation into associated influencing factors is presented in this paper. Furthermore, a parameter of the temperature-distributed transfer coefficient (TTC) is proposed to evaluate the transfer process. This study extends into a broader range of the discrete transfer method from liquid-helium temperatures to ambient temperatures and further analyzes the rules from scattered points to multiple points. The internal DC flow method is adopted to eliminate the radial thermal resistance and improve the TTC, recognizing the constraints of the traditional distributed transfer method (coiling heat exchange tubes outside the regenerator). The TTC of the distributed method with the DC flow is improved around 1–2 times by optimizing the mass flux of multi-strand DC flow and temperature range. It is also improved 1.5–2 times by combining the DC flow and discrete method. Additionally, the TTC is improved about 1–1.5 times with the DC flow when using the refrigeration power for gas liquefaction. [ABSTRACT FROM AUTHOR]

We show that powder pressed specimens of nickel can be sintered to 99.96% density by injecting electrical current, without the use of a furnace. Full sintering could be accomplished in 10 to 52 s by changing the current rate from 5 to 1 A/s. In all instances, the samples sintered abruptly at a current density of ∼20 A mm−2. The grain size of the sintered samples was somewhat larger than the nickel powder particle size (∼60 μm vs. 40 μm). Tensile testing yielded a yield strength of 98 MPa, ultimate tensile stress of 323 MPa, and ductility of ∼17%. Four in‐operando measurements are reported: (i) sintering, (ii) the change in resistance with current density, (iii) the temperature, and (iv) electroluminescence. The change in resistance during flash sintering exhibited a high peak followed by a steep decline in resistance; the transient is attributed to the breakdown of particle–particle interface resistance. The same cycle repeated with the flash‐sintered, dense sample, did not show the spike, and gave reproducible results. The resistance data for these latter cycles, when viewed as a function of temperature exhibited sigmoidal behavior: initially lower, and then higher than the literature values. This unusual behavior reflects the influence of defects generated during flash. We have also measured the endothermic enthalpy, expressed by the difference between the in situ input electrical energy and the radiation, convection, and specific heat losses. Dividing by the formation energy of Frenkel pairs yields the concentration of defects, estimated to be 0.3–0.4 mol %. These concentrations are far above thermal equilibrium; it is concluded that flash of metals is a far from equilibrium phenomenon. [ABSTRACT FROM AUTHOR]

It is imperative to mitigate the convective heat loss from the receiver to improve the overall efficiency of the parabolic dish concentrator. In this study, the reductions of convective heat loss from the cylindrical‐hemispherical receiver are numerically analyzed and the model was validated by the experimental data from literature. In the first case, the impact of the glass cover on convective heat loss is examined under conditions of both natural and forced convections at various receiver orientations (γ = 0°, 30°, 60°, and 90°). Numerical results clearly demonstrate that the use of a glass cover significantly reduces the intrusion of surrounding air into the receiver cavity which leads to an enhancement of the stagnation zone inside the cavity and, as a consequence, a noticeable reduction in convective heat loss is observed. To perform analysis of the receiver with glass cover under forced convective condition, the wind velocities over the receiver are considered in the range of 1–6 m/s. The maximum reduction of convective heat loss using the glass cover is achieved to be 58.44% with wind velocity of 5 m/s at γ = 60°. In the second case, the influence of air curtain at the receiver aperture under natural convective heat loss conditions is analyzed. The analysis incorporates three variables: receiver orientation (γ = 0°–60°), nozzle width (Lnoz ${L}_{\mathrm{noz}}$ = 0.002–0.004 m), and nozzle outlet velocity (Vnoz ${V}_{\mathrm{noz}}$ = 0.5–3.5 m/s). The results show that the air curtain minimizes the outflow of receiver inside air and results in an improvement in the stagnation zone inside the cavity. The maximum effectiveness of the air curtain is found to be 43.2% at nozzle width of Lnoz ${L}_{\mathrm{noz}}$ = 0.004 m and nozzle velocity of Vnoz ${V}_{\mathrm{noz}}$ = 1.5 m/s at receiver orientation of 60°. It is also noteworthy that the optimal nozzle velocity decreases with the increase of nozzle widths. [ABSTRACT FROM AUTHOR]

The peak explosion pressure and maximum rate of pressure rise of explosions in confined spaces are key safety parameters to evaluate the hazard of processes running in closed vessels and to design enclosures able to withstand explosions or of their vents used as relief devices. These properties are examined in the present paper, for hydrogen-hydrocarbon-air mixtures at sub-atmospheric pressures, using propane and n -butane as test fuels and variable hydrogen ratios between 0 and 0.3. The experimental study was carried out in a sphere and a cylindrical chamber at room temperature and sub-atmospheric pressures (between 0.3 and 1.0 bar). On the basis of pressure recordings, the characteristic explosion indices, i.e., the maximum explosion pressure (p max), maximum rate of pressure rise ((dp/dt) max), deflagration index (K G), and time to peak pressure (θ max) were derived. Numerical simulations were used to determine the adiabatic explosion pressures and adiabatic flame temperatures of isochoric combustion. The effects of initial pressure (p 0), hydrogen concentration, and shape and size of the explosion vessel on explosion indices are discussed. For each hydrogen concentration of the blended fuels, linear correlations p max = f(p 0) and (dp/dt) max = f(p 0) were found. In addition, the heat loss to the walls during explosion propagation was estimated on the basis of the difference between the adiabatic and experimental explosion pressures. The amount of heat lost increases with the increase of hydrogen blending ratio and vessel asymmetry. • Hydrogen-blended propane-air and butane-air explosions were studied in two closed vessels. • The experiments were performed at various initial pressures between 0.3 and 1.0 bar. • As Hydrogen blending ratio increases, the explosion pressure, the maximum rate of pressure rise, and the severity factor increase. • The increase of hydrogen blending ratio results in the decrease of the explosion times. • The observed variations depend largely on the volume and shape of the explosion vessel. [ABSTRACT FROM AUTHOR]

The high energy consumption of water bath heaters in city gate stations due to heating the passing gas is always a significant concern. A suggested approach is to apply a shell and tube heat exchanger to raise efficiency or utilize heat losses. This study first examined the impact of the geometrical parameters of a heat exchanger, e.g., baffle cut, baffle number, tube pitch, and tube diameter, on heat transfer, pressure drop, and exchanger price as objective functions and estimated the optimal point of the exchanger's geometry based on the TOPSIS algorithm. Then, the feasibility of replacing a shell and tube exchanger with a water bath heater in city gate stations was probed. The shell and tube exchanger was simulated and analyzed by Ansys Fluent software. The results showed that increases in the baffle cut from 20 to 50%, tube pitch from 1.3 to 1.9, and tube diameter from 21.3 mm to 42.2 mm reduced heat transfer by 10, 3, and 7% and pressure drop by 9, 10 and 11%, respectively, while a surge in the number of baffles from 2 to 5 raised pressure drop and heat transfer by 14 and 12%, respectively. The outcomes associated with the economic analysis of replacing an exchanger revealed that this replacement decreased fuel consumption and led to reduced contamination, on the one hand, and cost conservation, on the other hand, such that the net present value index zeroed in less than 5 years. [ABSTRACT FROM AUTHOR]

In this paper, a novel tubular solar air heater is introduced. In this air heater, the hot boundary layer is drawn into the absorber tube and can provide thermal energy at moderate temperatures. Several different cases were simulated and a correlation was proposed to predict the collector's effectiveness as a function Rayleigh number and Reynolds number. An equation was derived to find the effectiveness of this collector. Finally, a real case was studied with non-uniform solar flux distribution, as well as radiation heat loss. Good agreement was found between the results and those derived by the proposed analytical method. For different suction values, the first-law and the second-law efficiencies were calculated. Based on the exergy analysis, exergy destruction in absorption is the dominant factor that is unavoidable in low-temperature collectors. It was shown that there is an optimum suction value at which the second-law efficiency is maximized. At the optimum point, temperature rise can reach 54 K, which is hardly possible with a flat plate collector. Based on the exergy analysis, the relation between tube wall temperature and air outlet temperature in their dimensionless forms at the optimum working condition was derived, and it was shown that effectiveness at the optimum working condition is around 0.5. This means that the air temperature rise shall be half of the temperature difference between collector wall and the ambient temperatures. A high outlet temperature besides the low cost of construction and maintenance are the main advantages of this air heater. With such a high temperature rise, this type of collector can increase the use of solar energy in domestic applications. [ABSTRACT FROM AUTHOR]

In a parabolic dish system, the heat losses from the cavity receiver significantly suppress the system's efficiency and may increase its overall cost. Several existing researches have numerically and experimentally developed the different cavity receiver models by modifying their inclinations, design geometrics, and structure. The conductive loss does not occur much in the cavity receivers compared to the convective loss. So, the analysis of convective loss is more critical in the cavity receivers; however, the accurate prediction of convection loss is quite complex due to the temperature distribution near the cavity. This prime aim of the paper is to comprehensively review the existing literature related to design configurations of cavity receivers and heat loss analysis to set a platform for performance improvement via design modifications. The study emphasizes the effect of geometric parameters like the structure of cavity receivers, shape and sizes, and angle of inclinations with the ground. Structural configurations, especially the hemispherical, cylindrical, conical, and trapezoidal cavity receivers utilized for the solar dish collector (SDC), are investigated between the years 1980 to 2022. A comparison is made based on heat loss models and research outcomes. Besides, the Nusselt correlation model used for predicting heat losses is also carried out in this review by varying the effects such as inclination, aperture ratio, wind effect, etc. This review supports the solar cavity designers for experimentally investigating and simulating a new modified solar cavity receiver with minimization and accurately predicting convective losses. [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs) can cause devastating impacts in coastal marine ecosystems, particularly in shallow marginal seas, thereby making the understanding of the drivers of these events of paramount importance. Here, drivers for summer and winter MHWs are explored for the period 1980–2016 in the Baltic Sea, a mid-latitude marginal sea with a permanent haline water-column stratification located on the northwestern European shelf. It was found that summer MHWs are mainly forced by local meteorological conditions over the open water. They are caused by a dominant blocking over Scandinavia promoting anomalous strong shortwave downflux, calm winds, and low vertical mixing with colder sub-thermocline waters. Wintertime MHWs are linked to the advection of warm and moist air originating from the North Atlantic. These air masses lower the oceanic net heat loss at the sea surface primarily in the form of reduced latent and sensible heat losses. Vertical ocean dynamics are also affected during winter MHWs. This study finds a strengthened coastal up- and downwelling due to anomalous strong westerly winds during the time before MHWs culminate in their maximal surface extension. [ABSTRACT FROM AUTHOR]

With the development of offshore wind turbine single power toward levels beyond 10 MW, the increase in heat loss of components in the nacelle leads to a high local temperature in the nacelle, which seriously affects the performance of the components. Accurate reconstruction and control of thermal turbulence in the nacelle can alleviate this problem. However, the physical environment of thermal turbulence in the nacelle is very complex. Due to the intermittent and fluctuating nature of turbulence, the turbulent thermal environment is highly nonlinear when coupled with the temperature field. This leads to large reconstruction errors in existing reconstruction methods. Therefore, we improve the sparse reconstruction method for compressed sensing (CS) based on the concept of virtual time using proper orthogonal decomposition (POD). The POD-CS method links the turbulent thermal environment reconstruction with matrix decomposition to ensure computational accuracy and computational efficiency. The improved particle swarm optimization (PSO) is used to optimize the sensor arrangement to ensure stability of the reconstruction and to save sensor resources. We apply this novel and improved PSO-POD-CS coupled reconstruction method to the thermal turbulence reconstruction in the nacelle. The effects of different basis vector dimensions and different sensor location arrangements (boundary and interior) on the reconstruction errors are also evaluated separately, and finally, the desired reconstruction accuracy is obtained. The method is of research value for the reconstruction of conjugate heat transfer problems with high turbulence intensity. [ABSTRACT FROM AUTHOR]

In recent decades, the Arctic Ocean has undergone changes associated with enhanced poleward inflow of Atlantic and Pacific waters and increased heat flux exchange with the atmosphere in seasonally ice-free regions. The associated changes in upper-ocean heat content can alter the exchange of energy at the ocean–ice interface. Yet, the role of ocean heat content in modulating Arctic sea ice variability at sub-seasonal timescales is still poorly documented. We analyze ocean heat transports and surface heat fluxes between 1980–2021 using two eddy-permitting global ocean reanalyses, C-GLORSv5 and ORAS5, to assess the surface energy budget of the Arctic Ocean and its regional seas. We then assess the role of upper-ocean heat content, computed in the surface mixed layer (Qml) and in the 0–300 m layer (Q300), as a sub-seasonal precursor of sea ice variability by means of lag correlations. Our results reveal that in the Pacific Arctic regions, sea ice variability in autumn is linked with Qml anomalies leading by 1 to 3 months, and this relationship has strengthened in the Laptev and East Siberian seas during 2001–2021 relative to 1980–2000, primarily due to reduced surface heat loss since the mid-2000s. Q300 anomalies act as a precursor for wintertime sea ice variability in the Barents and Kara seas, with considerable strengthening and expansion of this link from 1980–2000 and 2001–2021 in both reanalyses. Our results highlight the role played by upper-ocean heat content in modulating the interannual variability of Arctic sea ice at sub-seasonal timescales. Heat stored in the ocean has important implications for the predictability of sea ice, calling for improvements in forecast initialization and a focus upon regional predictions in the Arctic region. [ABSTRACT FROM AUTHOR]

Large and downed woody fuels remaining behind a wildfire's flame front tend to burn in a smoldering regime, producing large quantities of toxic gases and particulate emissions, which deteriorates air quality and compromises human health. Smoldering burning rates are affected by fuel type and size, the amount of oxygen reaching the surface, and heat losses to the surroundings. An external wind has the dual effects of bringing fresh oxidizer to the fuel surface and porous interior, while at the same time enhancing convective cooling. In this work, a series of experiments were conducted on single and adjacent poplar dowels to investigate the effect of fuel geometry and wind speed on smoldering of woody fuels, including its burning rate and combustion products. Dowels had variable thickness (19.1 and 25.4 mm), aspect ratios, and arrangement (number of dowels and spacing between them). Using measurement of mass loss, CO, and HC production as indicators of the smoldering intensity, the results indicate that the arrangement of smoldering objects significantly affects burning rates and emissions. Specifically, spacings of 1/8 and 1/4 of the dowel thickness enhanced the smoldering process. The smoldering intensity was also enhanced by increased external wind (ranging between 0.3 m/s and 1.5 m/s), but its effect was dependent upon the spacing between the dowels. The convective losses associated with the spacing were further investigated with a simplified computational model. The simulations show that the wind significantly increases convective losses from the smoldering surfaces, which in turn may offset the increase in smoldering intensity related to the higher oxygen flux at higher wind speeds. [ABSTRACT FROM AUTHOR]

Accurately calculating the annual yield of floating PV (FPV) systems necessitates incorporating appropriate FPV-specific heat loss coefficients into the calculation, including both wind-dependent and wind-independent factors. The thermal behavior of several FPV systems has been investigated within this study, through the analysis of heat loss coefficients across various system sizes and configurations. Over a one-year period, data were collected from two measurement sites with three distinct systems: two ~50 kWp demonstrator-scale setups of Solarisfloat (azimuthal tracking) and Solar Float (East-West orientation) and a 2 MWp commercial-scale East–West system by Groenleven. The Solarisfloat demonstrator revealed a wind-dependent heat loss coefficient of 3.2 W/m3Ks. In comparison, the Solar Float demonstrator system displayed elevated wind-dependent heat loss coefficients, measuring 4.0 W/m3Ks for the east-facing module and 5.1 W/m3Ks for the west-facing module. The Groenleven system, which shares design similarities with Solar Float, showed lower wind-dependent heat loss coefficients of 2.7 W/m3Ks for the east-facing module and 2.8 W/m3Ks for the west-facing module. A notable discrepancy in the wind-dependent coefficients, particularly evident under a north wind direction, indicates a more efficient convective cooling effect by the wind on the demonstrator scale system of Solar Float. This could possibly be attributed to improved wind flow beneath its PV modules, setting it apart from the Groenleven system. Additionally, a thermal model founded on a 'balance-of-energy' methodology, integrating water temperature as a variable was introduced. The heat loss coefficient, dependent on the surface water temperature, fluctuated around zero, depending on whether the water temperature surpassed or fell below the ambient air temperature. It can be concluded that it is not of added value to introduce this floating specific heat loss coefficient parameter, as this parameter can be integrated in the wind speed independent Uc parameter. [ABSTRACT FROM AUTHOR]

Accurate evaluation of the wind convection heat transfer coefficient (hw) for solar‐based systems is essential, especially for solar desalination systems. Thermal behavior and productivity of solar stills are highly affected by the external heat loss through the glass cover. This paper describes a new experimental approach to estimate the hw on the glass cover of the conventional single‐slope solar distiller (CSS). Indoor experiments have been conducted under steady‐state conditions for a wind speed between 0 and 3 m/s. The hw has been evaluated through an energy balance performed on the distiller's glass cover. The results showed that increasing the wind speed increases the hw (from 5.64 to 31.57 W/m2 K) and enhances the distillation rate (from 5.28 to 7.61 mL/min). A new relationship for the hw was proposed for the CSS and compared with the experimental data available in the literature. The comparison shows that the obtained results are close to the data from solar systems, with a deviation ranging from 27.4% to 37%. However, a significant deviation was obtained with earlier models derived from flat plates (from 29.5% to 59%). [ABSTRACT FROM AUTHOR]

Household biomass gasifier stoves (HBGSs) are used in remote areas using natural firewood that is burned in the HBGS for general purposes, such as cooking and warming in winter. The heat dissipation from the walls is assumed to be heat loss. This paper evaluates the electrical performance of thermoelectric generators (TEGs) using heat recovered from the hot walls of an HBGS, considering the effect of three primary air valve angles of 0°, 9°, and 18°. The heat recovered from the HBGS that is electrically transferred through a TEG is assessed. The results showed that the wall heat loss increases with the primary air valve angle of the HBGS. The upper zone near the HBGS gas combustion zone exhibits higher wall temperatures than the middle and lower zones, with a maximum wall temperature of 140°C resulting in an output voltage of 2.55 V. However, the middle and lower zones are also considered as their capacities are consistent with the TEG temperature range. The heat loss from the HBGS is considerably larger than that from other heat sources, and the specific heating area of the heat source is a variable that should be considered to increase the number of TEGs to achieve the desired output values for practical applications. Furthermore, this research serves as a guideline for applying TEGs to recover waste heat from various applications. [ABSTRACT FROM AUTHOR]

Thermoelectric power generation (TPG) is a novel method where carriers within a conductor migrate from the hot end to the cold end, generating a potential difference under a temperature gradient. Due to hysteresis, this potential difference fluctuates periodically with environmental temperature changes. Therefore, implementing a self-adaptive module during operation is crucial to enhance output voltage stability. Using LTspice, we simulated a TPG system, incorporating a boost module for a DC/DC boost circuit and a self-adaptive module with a logic-level controlled current electronic switch. Analysis results demonstrated nonlinear power generation growth with increasing temperature differences. Conversely, power generation decreased with rising internal resistance R0, thermal resistance Rq, and heat capacity Cq of the entire system. Notably, changes in R0 and Cq values had a more pronounced impact compared to Rq values. Under constant thermoelectric electromotive force conditions, a 1.5× growth in R0 led to a corresponding 1.5× power growth, while a 1.5× growth in Rq resulted in a 1.06× power growth. Furthermore, a 1.5× growth in Cq under the same Tcold value caused greater heat loss, subsequently reducing power output. After constructing the self-adaptive module, the TPG system effectively rectified and stabilized the floating potential difference within the voltage drop range of the field-effect transistor conduction tube, optimizing output to 50 from 600 ms. The self-adaptive TPG system designed in this research exhibits practical significance and potential applications in precision measurement instruments. [ABSTRACT FROM AUTHOR]

To reduce the volume of landfill sludge, a more environmentally friendly technology is used to study the effects of different freeze–thaw–vacuum pretreatment modes. In addition to the cumulative effect of cooling time within different temperature bands, we analyse the temperature difference loss rate of shallow sludge over the period of cooling. During the annular freezing process, the mechanism of ice front formation is revealed by exploring the energy transfer process of landfill sludge. When repeated freeze–thaw–vacuums are performed, the pretreatment modes of a single pre-freeze–thaw and two consecutive pre-freeze–thaws are compared. The superiority of two modes is discussed in the light of local differences in dewatering performance and overall settlement trend characteristics. Furthermore, the final micromorphological structure indicates that the repeated freeze–thaw–vacuum pretreatment mode of sludge is affected by its depth to a certain extent. It is found that factors such as sludge depth and radial water migration have a significant impact on the time accumulative effect and energy transfer of frozen sludge. The sludge treatment mode of two consecutive pre-freeze–thaws has a better effect on the overall dewatering and reduction. [ABSTRACT FROM AUTHOR]

Trunk shakers perform a forced vibration that should be set according to tree species and architecture to efficiently detach fruits. However, manufacturing companies produce designs that are poorly customisable according to different trees. This work presents a prototype that is configurable in amplitude and frequency of vibration, which has been developed to generate the different vibration patterns required by various fruit trees. To study the feasibility of the developed technology, we built a test bench with a post, to which we fixed olive, almond and orange tree branches, and tested different configurations of the machine (frequencies from 12.25 to 20.75 Hz and eccentricities from 58 to 86 mm). Acceleration values were recorded at different points: the trunk shaker, the post in the grip, the top of the post, and in each branch. We recorded a large loss of acceleration transmissibility between the shaker and the post (20%–60%) due to existing frictions that dissipate energy through heat loss. There is a non-linear increase between vibration frequency and the resultant acceleration value recorded, as well as with increasing eccentricity. The shaker was able to provide a different vibration pattern in each configuration, affecting the transmission of vibration in each of the branches studied, for which mean acceleration transmissibility ranged between 82% (almond), 104% (olive) and 136% (orange). [ABSTRACT FROM AUTHOR]

Electrocaloric effect and loss-induced self-heating are simultaneously investigated in single-crystalline relaxor 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 by a direct, high-resolution method. Transients of the total temperature change for few-cycle electric field pulses allow to distinguish and individually determine the contributions from electrocaloric effect and self-heating with millikelvin temperature and submillisecond temporal resolution. Simultaneous dielectric measurements make the comparison of observed self-heating to hysteresis losses possible, where very good agreement is found. The loss factor as a figure of merit for electrocaloric materials is directly obtained from the combined determination of caloric temperature change and losses. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) plays an important role in industrial applications with intermittent generation of thermal energy. In particular, the implementation of latent heat thermal energy storage (LHTES) technology in industrial thermal processes has shown promising results, significantly reducing sensible heat losses. However, in order to implement this technology, a proper selection of materials is important. In this study, a new multi-criteria phase change material (PCM) selection methodology is presented, which considers relevant factors from an application and material handling point of view, such as hygroscopicity, metal compatibility (corrosion), level hazard, cost, and thermal and atmospheric stability. The methodology starts after setting up the system requirements where the PCM will be used, then a material screening is able to find all possible candidates that are listed with all available properties as listed before. Then, a color map is produced, with a qualitative assessment of material properties drawbacks, hazard level, melting enthalpy, and price. The experimentation starts with a preliminary set of tests on hygroscopicity and one-week corrosion test, which allows disregarding PCMs and selecting a short list of potential PCMs that would need further characterization before the final selection. [ABSTRACT FROM AUTHOR]

Flat plate solar collectors are extensively used in buildings, however due to excessive heat losses, these collectors are not efficient. Metal foams can enhance the thermal efficiency in expense of higher pumping power. A numerical simulation is carried out to investigate the influence of geometrical characteristics of porous medium on the pressure drop and heat transfer. An innovative design with gradually increasing or decreasing height is proposed. Porous block consists of three smaller blocks, two rectangular blocks at the inlet and outlet connected with a trapezoidal block. Non-dimensional height and length of the rectangular blocks vary between 0.2–0.6 and 0.1–0.9 respectively, and the optimum geometry of the porous block is proposed. Central composite design is conducted to find an optimum geometrical design and 25 design points have been investigated. The main target of this optimization is the simultaneous increment of Nusselt and decrement of pressure drop. Results demonstrate that porous block with non-dimensional inlet and outlet height of 0.9 and 0.5 and inlet and outlet length of 0.4 and 0.4 respectively, result in the highest Nu (= 15.2). Comparing the optimal results with those of a conventional rectangular porous block with constant height of 0.9 represents that in the optimum design Nu is only 7.23% less than that of the conventional design, while, pressure drop is improved up to 38.46% in the proposed geometrical design. Additionally, response surface methodology has been carried out and results have been reported in response surface plots. [ABSTRACT FROM AUTHOR]

The efficiency of the parabolic dish system is significantly impacted by the thermal energy lost from the receiver. Well-established correlations can be used to determine the energy's conduction and radiation modes. However, due to the complex flow behavior near the cavity receiver, estimating the loss of convective heat is difficult. Surprisingly, the majority of studies has solely examined forced convection from the cavity and has not considered the impact of the dish structure. The presence of the dish structure may alter the local wind patterns near the cavity, which may also affect heat loss. Given the importance of an improved thermal model, the behavior of the wind flow must thus be investigated by adding the dish structure. The numerical results obtained in this work confirm that the dish has a significant impact on the flow in the cavity region. Under normal operating conditions, the cavity receiver is protected from the free stream flow by the dish architecture. Because the local flow velocity is relatively low near the receiver, there is a noticeable reduction in heat loss from the device. [ABSTRACT FROM AUTHOR]

Based on the irreversible closed Braysson cycle model constructed by predecessors which included the heat leakage loss, internal irreversibility loss and thermal resistance loss and finite-time thermodynamics, NSGA-II algorithm is applied to conduct multi-objective optimization for the dimensionless ecological function ( E ¯ ), efficiency (η ), dimensionless power density ( P ¯ d ) and dimensionless power output ( P ¯ ) of different objective combinations with logarithmic temperature ratio (x ) of working fluid and heat conductance distribution (u ) of heat exchangers as design variables. The best multi-objective optimization scheme is picked by three decision-strategies, and the relations among four optimization goals and the optimal design variables are analyzed when quadruple-objective optimization is conducted. The conclusions are as follows: when conducting quadruple-objective optimization, when the optimal x ascends, the P ¯ ascends, the η and E ¯ firstly ascend and then descend, the P ¯ d descends. When conducting triple-objective optimization with objectives of P ¯ - η - E ¯ , the value of deviation index gained by LINMAP decision-strategy is 0.2251 and the smallest, so this scheme is the best. Multi-objective optimization can find the optimal compromise among various optimization objectives, and the results provide certain guidance and reference for the relevant research and design of the Braysson cycle. [ABSTRACT FROM AUTHOR]

Double skin facades (DSF) aim to save energy reducing the heat losses in buildings. They are visually appeal while allowing to use daylight efficiently. Such facade systems can reduce glare and distribute daylight evenly in the interior when compared to conventional facade systems. That is a result of cavities between two glass facades and locating sun shading elements in them, although this system provides a high level of transparency. As their primary purpose of application is to ensure thermal performance and ventilation, most studies in literature have focused on these. This study started with the hypothesis that studies examining daylight performance in DSFs are more limited than studies examining thermal performance and that daylight optimization methods are not used sufficiently in DSFs. In this context, the study aims to analyze studies focusing on daylight performance of DSFs. The review targets results of such current studies to guide future ones providing feedback knowledge. This may help to better technical developments in such facades and make them prevail in constructions or in retrofitting So, it contributes to literature in this sense. Recent studies are shown in tabulated form and interpreted in detail with graphics. considering their methodologies, daylight parameters and findings. Results show that the daylight parameter is one of the most important issues that architects or designers should consider from the moment they start the design, and they should make their designs based on the optimum penetration of daylight into the building. Consequently, this review presents that the use of daylight optimization has started to be used in recent studies dealing with DSFs. A DSF design can optimally get daylight into the interior can be made by using this method more frequently. [ABSTRACT FROM AUTHOR]

Adsorbents heated using solar energy can be used to achieve thermal energy storage and sorption refrigeration with low environmental impacts. This research compares two different methods of heating adsorbents with solar energy to store thermal energy: (1) by exposing the adsorbents to incident light transmitted through a solar collector window, and (2) by heating a highly absorbing solar collector cover, and then transferring the heat from this solar absorber to adsorbents located beneath it. To carry out this comparison experiments are conducted for three cases of adsorbent beds using zeolite 13X and water as the adsorbent-adsorbate pair. In the first case, the top of the adsorbent bed is a polycarbonate sheet, and the zeolites are heated directly by solar-simulated light transmitted through this sheet. In the second case, a blackened aluminum sheet is placed beneath the polycarbonate sheet to generate heat by absorbing incident light. For the third case, the blackened aluminum absorber is placed directly on top of the zeolite beads and the absorber is isolated from the walls of the reactor to avoid heat losses. The outcomes reveal an energy storage density (ESD) of 43.6 kWh/m³ (63.4 Wh/kg) when light is directly incident onto the zeolite 13X and an ESD of 33.3 kWh/m³ (48.4 Wh/kg) when light is incident onto a blackened absorber plate that transfers heat to Zeolite beads residing beneath it. However, ESD values were improved to 48.9 kWh/m³ (71.0 Wh/kg) when the blackened absorber plate was thermally insulated from the walls of the adsorbent bed. These results demonstrate the importance of an optimal absorber arrangement in enhancing the adsorption process for the purpose of elevating energy storage densities. [ABSTRACT FROM AUTHOR]

Energy absorption and flow through a nest is an important aspect of embryonic development in many reptile species including turtles. To date, few studies have explicitly attempted to quantify the energy flow through turtle nests, opting instead for the simplified approach offered by temperature index models. However, the quantification of the energy can provide an explicit abiotic link that can link biological models to biometeorological and ecohydrological processes and models. We investigated the energy flow through turtle nests occupying different bedrock morphologies within a Canadian Shield Rock Barren landscape, in Ontario, Canada. The taxons studied were Spotted Turtle (Clemmys guttata), Midland Painted Turtle (Chrysemys picta marginata), and Blanding's Turtle (Emydoidea blandingii). Nest temperature and soil moisture were measured in 2018 and 2019 using sensors placed in the soil adjacent to 12 turtle nest cavities. Three main rock morphologies were identified for each nest location, Crevice, Ledge, and Flat types, that are in order of decreasing bedrock percentage contact with the nest site. Ground heat flux and change in heat storage were determined using the calorimetric method for each nest, while the direction of energy flux between the atmosphere and the underlying rock was also determined. The Crevice nest morphology experienced the lowest ground heat flux on average (1.56 × 10−1 W m−2) and lowest cumulative heat storage (230 MJ) compared to the Flat (440 MJ) and Ledge (331 MJ) nests. However, over the diurnal cycle, large heat gains by Flat nests were mostly balanced out by nighttime heat losses. While Crevice nests saw the lowest daily heat storage gains, they experienced much lower heat losses over the evening period compared to the other nest types. Furthermore, we found that 59% of the energy is directed from the underlying bedrock into the Crevice nest, highlighting the importance of the bedrock in controlling thermal dynamics in the turtle nesting habitat. The lower variability in energy parameters for Crevice nest types can be attributed to higher amounts of nest‐to‐bedrock contact, compared to the flat nest types. Our results indicate that Crevice morphology may be ideal for turtles nesting at their northern limits because minimal heat loss during the evening can result in a more stable thermal incubation environment. Future conservation and habitat restoration efforts should consider the importance of bedrock morphology and prioritize the protection of Crevice nest sites. Furthermore, this work highlights important opportunities for potential interdisciplinary work between ecologists, climatologists, biologists, and hydrologists, specifically the integration of ecohydrological and biological models. This work also underscores the potential uncertainty of climate change impacts on turtle egg hatching success and nest sex ratios. [ABSTRACT FROM AUTHOR]

Reducing losses of energy and destroyed exergy requires optimizing the space between double glazings. Air's poor thermophysical characteristics limit its ability to reduce heat loss in double-glazed Photovoltaic thermal (PV-T) systems. The aim of this study is to investigate how gases like argon, xenon, krypton, sulfur dioxide, and carbon monoxide, when trapped within double glazing and positioned between the inner glass and the absorber (PV model), affect the efficiency, useful heat energy, overall heat loss coefficient, and outlet temperature of the Photovoltaic thermal panel. The research uses the new Eismann correlation to repeatedly measure heat transfer in spaces filled with gases, helping to find the best distances. He also looks into how these gases impact exergy efficiency, destruction energy, and system energy. Among these rare gases, Xenon performs the best in terms of thermal performance, followed by Krypton and Argon when compared to air. Specifically, their total combined efficiency of different filling gases is 49.35% (Xenon), 48.72% (Krypton), 48.02% (Argon), 47.71% (sulfur dioxide), 47.05% (carbon monoxide), and 46.92% (air). The ideal gas-filled spaces for these total combined efficiencies are 5 mm for Xenon, 6 mm for Krypton, 9 mm for Argon and sulfur dioxide, and 10 mm for carbon monoxide and air. The exergy approach confirms these results, showing the same optimal gas-filled space widths. [ABSTRACT FROM AUTHOR]

The application of fins as a solar heat absorber on solar still desalination has gained attention to enhance productivity, efficiency and cut heat losses. Considering the effectiveness of fin configuration, it is still the focus of development by many researchers. To determine the optimum height configuration, this study conducted an experimental analysis of hollow circular fin (HCF) height as variation during the day testing under the Kentingan Sebelas Maret University climates. Moreover, the hollow circular fin is constructed utilizing the SS302 material. The variation used is conventional CS4, which incorporates the supplementary heights of 20 mm, 40 mm, and 60 mm for the hollow circular fins. Overall, the study has identified a consistent decrease in efficiency as the HCF increases, with efficiency gains of 40.96%, 35.39%, and 29.16%. However, different circumstances yield favorable outcomes, exhibiting a notable improvement of 10.30% and 5.57% in enhanced efficiency for 20 mm and 40 HCF, respectively, compared to conventional solar stills against the analysis that can evaluate the energy loss through the partition and solar still wall. A correlation analysis was conducted using both experimental productivity data and analysis prediction data to ensure that this experiment analysis yielded excellent results compared to others. [ABSTRACT FROM AUTHOR]

This study examined the influence of various chemical reaction mechanisms and heat loss conditions on the prediction of longitudinal combustion instability in the Continuous Variable Resonance Combustor (CVRC). To assess the impact of chemical reaction mechanisms on the prediction of longitudinal combustion instability modes, both global and skeletal mechanisms were used, while adiabatic wall conditions were employed to eliminate the effects of heat loss. To evaluate the effect of heat loss conditions on the prediction of combustion instability modes, investigations were conducted under three different conditions: adiabatic wall, isothermal wall, and considering thermal radiation using the simple P1 model and the gray gas model. Radiative heat loss was calculated using a radiative convection boundary condition, while heat loss through wall convection was ignored. The dominant frequency, temperature field, pressure field, and combustion instability development mechanism were analyzed based on the numerical results and compared with experimental data and previous numerical studies. The use of a skeletal mechanism and the consideration of heat loss were found to reduce the difference in combustion instability mode frequency compared to experimental data. The results showed that maintaining an isothermal wall temperature effectively decreased the difference in the dominant frequency compared to experiments, but had limitations in reducing pressure fluctuation amplitudes. Additionally, incorporating thermal radiation did not significantly decrease the difference in the first mode frequency compared to experimental data, although it kept the range of pressure fluctuations within a reasonable level. Therefore, this study underscores the importance of accurate temperature prediction for evaluating thermal-acoustic instability frequencies and highlights the necessity of using a chemical reaction mechanism that accurately predicts the adiabatic flame temperature and heat loss conditions. • We investigated the impact of modeling choices on the prediction of instability. • Global and skeletal reaction mechanisms overestimated instability frequencies. • Radiative heat loss was found negligible for temperatures under 2500 K. [ABSTRACT FROM AUTHOR]

The mistral is a northerly gap‐wind regime blowing through the Rhone Valley in Southern France. It is held responsible for the sea‐surface cooling necessary to produce deep convection in the Gulf of Lion through turbulent ocean heat loss. The mistral is tightly connected to lee‐cyclogenesis in the Gulf of Genoa, where topography forces substantial downward motion. Dry intrusions (DIs) are airstreams forming the descending branch of extratropical cyclones. Known to induce cold and dry surface anomalies, DIs are potential contributors to enhanced surface evaporation during mistral. In this study, a climatological database (ERA‐INTERIM, 1981–2016) of mistral–DI co‐occurrence is constructed, allowing quantification of the impact of DIs on the mistral evaporative hot spot for the first time. We find that, on average, mistral–DI evaporation rates are doubled, compared to mistral without DIs. Moreover, cluster‐composite analysis reveals amplifications exceeding 300% between dynamically similar mistral events, with response to DIs. Daily latent heat‐flux anomalies in the Gulf of Lion are decomposed into contributions from the various parameters to analyse the mistral evaporation response to DIs. Mistral–DI events are shown to produce extreme evaporation rates through increased mistral wind speeds. The results highlight the downward momentum flux delivered by DIs to the mistral at the Gulf of Lion as the primary driver of the evaporation amplification mechanism. We further explore the variability between different mistral–DI events and conclude that extreme mistral–DI evaporation events are linked to descending air trajectories entering the Gulf of Lion at an early stage of their lifetimes. These DIs charge the mistral with maximum vertical momentum fluxes, which act to intensify surface winds and hence evaporation rates. [ABSTRACT FROM AUTHOR]

A field campaign in a valley near Seefeld, Austria, well known for the frequent occurrence of cold‐air pools, was conducted to identify the processes leading to the formation and erosion of the cold‐air pool. Here, we focus on a case study in January 2020 that featured cold‐air pool formation interrupted by a wind disturbance. Simulations with the Weather Research and Forecasting model were performed at a horizontal grid spacing of 40 m and compared with measurement results. The model was able to reproduce the intense cooling in the beginning of the night and the cold‐air pool erosion in the middle of the night caused by the wind disturbance, but stronger winds than observed prevented the cold‐air pool from fully re‐establishing in the model after the disturbance. The dominant cooling processes were long‐wave radiative heat loss and turbulent exchange, both of which are parametrized and cool the air locally. Advection was the most important warming contribution during the cold‐air pool disturbances, especially its cross‐valley and vertical components. Owing to numerical constraints and the shallow nature of the cold‐air pool, its extent was limited to the lowest model level. Further improvements to the cold‐air pool's representation in the model would require a finer grid resolution. [ABSTRACT FROM AUTHOR]

The urban utility tunnel is an indispensable part of modern engineering construction. However, the fire risk cannot be ignored due to the narrow space and limited ventilation of the utility tunnel. A study of smoke filling is performed in a 1/8-scaled utility tunnel (25 m × 0.5 m × 0.45 m). Five heat release rates (5, 10, 15, 20 and 25 kW) and four positions of fire sources are used for tests. The initial position of the one-dimensional smoke movement of strong plume is determined. Based on the traditional model, the longitudinal temperature attenuation model of tunnel smoke is established with consideration of radiation and convection heat losses. The theoretical value of the longitudinal temperature rise of smoke is in good agreement with the experimental value. A one-dimensional spreading velocity model is established that coincides well with the experimental value, and the relative error is less than 20%. The spreading velocity of smoke is increased by the heat release rate. The velocity of the smoke spreading at the near end is smaller than that at the center, due to the long spreading route. The current conclusions disclosed in this study provide important guidance for the ventilation design of utility tunnels for fire smoke scenarios. [ABSTRACT FROM AUTHOR]

This study experimentally and computationally investigates the heat transfer capability of supercritical carbon dioxide (sCO2) single jet impingement. The evaluated jet Reynolds number range is between 80,000 and 600,000, with a nondimensional jet-to-target surface spacing of 2.8. CO2-impinging jet stagnation conditions were maintained at approximately 200 bar and a temperature of ~400 °C for most experiments. The goal is to understand how changes in the aforementioned parameters influence heat transfer between the working fluid and the heated surface. Additionally, due to the elevated Reynolds numbers and difference in thermodynamic properties between air and CO2, air-derived impingement correlations may not be appropriate for CO2 impingement; these correlations will be evaluated against experimental sCO2 impingement data. At the time of this study, no sCO2 impingement data was available relevant to sCO2 power cycles. The target surface is a 1.5-in. diameter copper block centered on the 3 mm jet orifice. A mica heating element bolted to the bottom of the copper block provides a uniform heat flux. Thermocouples embedded in the copper block are used to determine the surface temperature. Nusselt numbers obtained from experimental sCO2 test data are compared to area-averaged Nusselt numbers from air-derived correlations. The comparisons showed that air correlations drastically underpredict the heat transfer when sCO2 is used as the working fluid. A modified sCO2 correlation using experimental data at discussed conditions is derived based on an existing air correlation. A CFD study is also performed to further investigate sCO2 heat transfer characteristics, and assess the numerical model applicability to this problem type. [ABSTRACT FROM AUTHOR]

A pilot plant comprising membrane distillation is tested for coordinated inlet temperature for the feed and cold streams with a fixed difference. Selected inlet temperature differences of 30, 40, and 50 °C were examined. It is found that water production increases with both temperature difference and inlet feed temperature. Specifically, the water production at a temperature difference of 50 °C can be 13%, and 30% higher than that at a temperature difference of 40, and 30 °C, respectively. The measurements of the mass flux were used to validate the internal mass and heat transfer equations which proved to provide an excellent prediction of the water production with up to 3.7% average error. The measurements of the exit temperature of the brine and permeate streams were used to confirm the macroscale heat balance equations. They revealed a considerable discrepancy between the heat supplied by the feed stream and the heat transferred between the two channels as well as between the heat gained by the cold stream and the heat supplied. The first discrepancy is ascribed to the existence of environmental heat loss at the feed side. The second discrepancy is attributed to the existence of environmental heat loss and the contribution of the heat of condensation to additionally warm up the cold stream. [ABSTRACT FROM AUTHOR]

Advanced control strategies for delivering heat to users in a district heating network have the potential to improve performance and reduce wasted energy. To enable the design of such controllers, this paper proposes an automated plant modeling framework that captures the relevant system dynamics, while being adaptable to any network configuration. Starting from the network topology and system parameters, the developed algorithm generates a state-space model of the system, relying on a graph-based technique to facilitate the combination of component models into a full network model. The accuracy of the approach is validated against experimental data collected from a laboratory-scale district heating network. The verification shows an acceptable average normalized root-mean-square error of 0.39 in the mass flow rates delivered to the buildings, and 0.15 in the network return temperature. Furthermore, the ability of the proposed modeling technique to rapidly generate models characterizing different network configurations is demonstrated through its application to topology optimization. The optimal design, obtained via a branch and bound algorithm, reduces network heat losses by 15% as compared to the conventional length-minimized topology. [ABSTRACT FROM AUTHOR]

Thermoelectric devices (TEDs) show great potential for waste heat energy recycling and sensing. However, existing TEDs cannot be self‐adapted to the complex quadratic surface, leading to significant heat loss and restricting their working scenario. Here, surface‐conformable origami‐TEDs (o‐TEGs) are developed through programmable crease‐designed origami substrates and the screen‐printing TE legs. Compared with "π" structured TEDs, the origami design (with heat conductive materials) changed the heat‐transferring direction of the laminated TE legs, resulting in an enhancement in enlarging ΔT/THot and Vout by 5.02 and 3.51 times. Four o‐TEDs with different creases designs are fabricated to verify the heat recycling ability on plane and central quadratic surfaces. Demonstrating a high Vout density (up to 0.98 −2at ΔT of 50 K) and good surface conformability, o‐TEDs are further used in thermal touch panels attached to multiple surfaces, allowing information to be wirelessly transferred on a remote display via finger‐writing. [ABSTRACT FROM AUTHOR]

Fitting gaps are a critical factor affecting the efficiency of high-pressure, large-scale plunger pumps. In actual work, fitting gaps change under liquid pressure and temperature rise, and the fluid flow in the annular channel changes under the fitting gap, in turn affecting the fitting gap. Therefore, on the basis of the thermo-fluid–structure interaction, a thermodynamic analysis model of plunger friction pairs is established in this work. The model considers the heat production due to plunger pair friction, frictional head loss, local head loss and heat dissipation caused by the fluid and air. Given that heat production and dissipation are greatly affected by annular channel flow, the deformation and leakage equations of the large-scale annular channel are established on the basis of pressure and temperature rise. In consideration of the gap deformation, gap flow, heat production, and heat dissipation of the plunger, a thermal balance equation is established, and the temperature rise of the plunger pair under different initial gaps is analyzed. In addition, a plunger pump experiment system is built to test the temperature rise of the plunger pair. Results show that the model can effectively predict the temperature of the plunger friction pair. The research results can provide a theoretical basis for the design of large-scale, high-pressure gap seals. [ABSTRACT FROM AUTHOR]

Achieving flame stabilization in micro-combustors presents an extremely challenging task due to enhanced heat loss resulting from the high surface-to-volume ratio and short residence time. Increase in flame stability enhances the feasibility and energy output from micro-combustor. Therefore, in this work, we have simulated a non-premixed hydrogen air microcombustor, which can provide higher flame stability along with good combustion efficiency. Initially a non-premixed numerical model of 16 mm length and 1 mm channel height was validated with published numerical and experimental results and thereafter, a circular bluff-body of 0.4 mm diameter was integrated with it and its synergistic effects were investigated. Due to the bluff-body attachment, the blow-out limit of micro-combustor increases from air intake velocity of 17.4 m/s to 32.5 m/s for a given equivalence ratio. Moreover, this bluff-body attachment helps the micro-combustor to maintain a high combustion efficiency for higher air inlet velocities. Formation of a low velocity zone along with pool filled with primary molecules (like H and OH) are the main reasons behind this flame stability and high combustion efficiency.However, a unique "flame street" phenomenon is observed as the air velocity surpasses 28 m/s before reaching blowout. This phenomenon is characterized by an array of oval-shaped flamelets forming in the downstream section of the micro-combustor. Detailed studies indicate that the flame streets are caused due to stretching of the flame. Furthermore, this flame street phenomenon also has a notable impact on the combustion efficiency of the microchannel. It is observed that combustion efficiency sharply decreases with the formation of flame streets, further emphasizing the far-reaching consequences of this phenomenon. • Microscale combustor flame stability challenges: high heat loss from elevated surface-to-volume ratios. • 2D numerical model explores flame stability in confined hydrogen-air non-premixed flame in a narrow channel. • Circular bluff body extends flame blowout limit, highlighting geometry's impact on stability. • Discovery of "flame street" phenomenon reveals complex mechanisms, impacting microchannel combustion efficiency. [ABSTRACT FROM AUTHOR]

The commercialization of a solar technology necessitates the fulfillment of specific requirements both regarding efficiency and stability to enter and gain space in the photovoltaic market. These aims are heavily dependent on the selection of suitable materials, which is critical for suppressing any reliability risks arising from inherent instabilities. Focusing on the absorber material, herein the most suitable low bandgap lead‐tin composition candidate for all‐perovskite tandem applications is investigated by studying their degradation mechanisms with both widely available and advanced characterization techniques. Three irreversible degradation processes are identified in narrow bandgap Pb‐Sn perovskite absorbers: 1) Tin (Sn) oxidation upon air exposure, 2) methylammonium (MA) loss upon heat exposure, and 3) formamidinium (FA) and cesium (Cs) segregation leading to impurity phase formation. From an industrial perspective, it is proposed to refocus attention on FASn0.5Pb0.5I3 which minimizes all three effects while maintaining a suitable bandgap for a bottom cell and good performance. Moreover, a practical and highly sensitive characterization method is proposed to monitor the oxidation, which can be deployed both in laboratory and industrial environments and provide useful information for the technological development process, including, the effectiveness of encapsulation methods, and the acceptable time windows for air exposure. [ABSTRACT FROM AUTHOR]

One of the drivers of life's diversification has been the emergence of "evolutionary innovations": The evolution of traits that grant access to underused ecological niches. Since ecological interactions can occur separately from mating, mating-related traits have not traditionally been considered factors in niche evolution. However, in order to persist in their environment, animals need to successfully mate just as much as they need to survive. Innovations that facilitate mating activity may therefore be an overlooked determinant of species' ecological limits. Here, we show that species' historical niches and responses to contemporary climate change are shaped by an innovation involved in mating--a waxy, ultra-violet-reflective pruinescence produced by male dragonflies. Physiological experiments in two species demonstrate that pruinescence reduces heating and water loss. Phylogenetic analyses show that pruinescence is gained after taxa begin adopting a thermohydrically stressful mating behavior. Further comparative analyses reveal that pruinose species are more likely to breed in exposed, open-canopy microhabitats. Biogeographic analyses uncover that pruinose species occupy warmer and drier regions in North America. Citizen-science observations of Pachydiplax longipennis suggest that the extent of pruinescence can be optimized to match the local conditions. Finally, temporal analyses indicate that pruinose species have been buffered against con-temporary climate change. Overall, these historical and contemporary patterns show that successful mating can shape species' niche limits in the same way as growth and survival. [ABSTRACT FROM AUTHOR]

Photothermal catalytic CO2 hydrogenation holds great promise for relieving the global environment and energy crises. The "nano‐greenhouse effect" has been recognized as a crucial strategy for improving the heat management capabilities of a photothermal catalyst by ameliorating the convective and radiative heat losses. Yet it remains unclear to what degree the respective heat transfer and mass transport efficiencies depend on the specific structures. Herein, the structure‐function relationship of the "nano‐greenhouse effect" was investigated and optimized in a prototypical Ni@SiO2 core‐shell catalyst towards photothermal CO2 catalysis. Experimental and theoretical results indicate that modulation of the thickness and porosity of the SiO2 nanoshell leads to variations in both heat preservation and mass transport properties. This work deepens the understandings on the contributing factor of the "nano‐greenhouse effect" towards enhanced photothermal conversion. It also provides insights on the design principles of an ideal photothermal catalyst in balancing heat management and mass transport processes. [ABSTRACT FROM AUTHOR]

To explore the impact of well spacing on the in situ high-temperature air injection for three-dimensional shale oil recovery, this study constructed six different well-spacing physical models of shale oil for investigation. By comparing factors such as temperature distribution, cumulative oil production volume, heating rate factor, and specific energy consumption per unit volume of shale oil among the six different well-spacing models, the influence of well spacing on the in situ high-temperature air injection for three-dimensional shale oil recovery was analyzed. The results showed that all six shale oil models exhibited a ripple pattern, advancing along the fractured fissures from the heating well to the production well. Model I, Model II, Model III, Model IV, Model V, and Model VI completed the full decomposition of the shale region at 2610, 1530, 1800, 3510, 4050, and 6660 days, respectively. The heating rate factor reached its peak at 1800, 900, 1440, 2340, 3240, and 3960 days. Model III had the lowest specific energy consumption per unit volume of shale oil, which was 905.41 kW/m3. Using Model III for three-dimensional shale oil injection with high-temperature air in situ recovery will shorten the heating time and reduce heat loss. [ABSTRACT FROM AUTHOR]

• Velocity characteristics at the injection pipe outlet is affected by the pressure wave in injection pipe. • There is a backflow at the injection pipe outlet. • The amount of backflow varies against the injection pipe length and decrease under resonant condition. • A backflow may cause a heat loss by heating liquid refrigerants from the flash tank. • Reducing a backflow using the resonance is advantageous for improving the COP of vapor injection cycle. The vapor injection cycle with flash tank and two stage compressor is known as an efficient cycle. It is known that the intermediate pressure is a key factor for COP improvement and pressure change during the injection process could reduce the COP. However, the effect of the pulsating intermediate pressure of a two-stage compressor on COP is not clear. In a previous study, the authors experimentally showed that COP varied with injection pipe length. There seemed to be a correlation between COP and the resonance phenomenon caused by pressure pulsation in the injection pipe. However, the mechanism of COP improvement is not well understood. In this study, a one-dimensional simulation model was developed to clarify the mechanism and was verified with the experimental results. The simulation results show that resonance in the injection pipe does not increase the injection mass flow rate into the suction pipe. On the contrary, backflow occurs in the injection pipe and the backflow ratio is minimum in the resonant condition. Due to the high temperature of the backflow coming from the discharge pipe, the saturated vapor from the flash tank is easily heated, causing heat loss and lower COP. It was found that COP can be improved by using resonance to suppress the backflow. [ABSTRACT FROM AUTHOR]