Rate Of Heat Loss Research Articles

Theoretical and experimental study on the effect of the heat shield on the trough solar cavity receiver in alpine areas

The large heat loss of the cavity receiver limits its application in parabolic trough collectors, matching the environmental factors in alpine areas, in this paper, adding a glass cover plate as a heat shield at the aperture of the trough inverted trapezoidal cavity receiver is investigated. To quantify the optimization of the system performance by adding, an analytical study is carried out for the cavity receiver using theoretical calculations of heat transfer and indoor experimental tests, while “thermal uniformity” is introduced as an indicator of the temperature distribution inside the cavity, and further verifies experimentally by the outdoor real-area environment. The findings indicate that adding a heat shield is significantly effective in reducing heat loss in windy areas. At the flow rate of 250 L/h and inlet temperature of 323 K, the maximum experimental heat loss value is significantly reduced by 70.01 % in the range of 1–5 m/s wind speeds compared to the one without a heat shield. When the wind direction is from −60° to 60°, the heat loss inside the cavity is small after adding, forming a stable stratified flow, and the thermal uniformity decreases by only 0.02, indicating that the stability of the temperature field inside the cavity is high. Furthermore, outdoor validation experiments demonstrate a slower change in heat loss rate with adding the heat shield compared to without, the growth rate of the former is close to 1/3 that of the latter, with a maximum suppressed heat loss rate of 23.49 %. This study provides the theoretical basis and data guidance for optimizing cavity receiver performance in alpine areas.

Non-evaporative heat dissipation across the beaks and casques of large forest hornbills

Heat loss across the beak is an important thermoregulatory mechanism among birds, particularly in large-beaked taxa such as toucans (Ramphastidae) and hornbills (Bucerotidae). The number of species investigated remains limited, as does our understanding of how the functional significance of this pathway varies with environmental variables such as humidity, with little previous research on species inhabiting humid environments. We used infrared thermography to test the hypothesis that large (600 – 1300 g) Afrotropical forest hornbills use their beaks and casques as thermal radiators. We collected data over air temperatures (Tair) of 15 - 34°C for wild-caught trumpeter hornbills (Bycanistes buccinator) and captive-bred silvery-cheeked hornbills (Bycanistes brevis) and black-casqued hornbills (Ceratogymna atrata). Surface temperatures of the beaks and casques (Tbeak) tracked Tair below 24-25°C, but at higher Tair, the Tbeak – Tair gradient increased to maximum values of 10-12°C. Maximum rates of beak heat loss were 2.5 – 3.8 W, equivalent to 31-83 % of estimated resting metabolic heat production. Facial skin showed also evidence for active regulation of heat loss. We also analysed the scaling of the inflection Tair above which the Tbeak – Tair gradient increases (Tinflection) by combining our data with published and three unpublished values. We found that Tinflection decreases with increasing body mass (Mb), with the relationship best described by the linear regression model Tinflection = -9.134log10Mb + 50.83, with Mb in g.

Investigating the performance of an affordable parabolic dish collector with double glass vacuum cavity cover

Parabolic dish collectors (PDC) are one of the most important ways to concentrate solar energy. In this study, the performance of a low-cost parabolic dish collector with high average output temperatures is investigated. The low-cost PDC has a 45 ° edge angle and a circular receiver. A vacuum double-glazed cavity is used to keep heat inside the receiver and reduce the rate of heat losses. On clear and cloudy days, tests were conducted with thermal oil as a heat transfer fluid (HTF) to analyze the performance of the PDC. The results show that the change in temperature of the heat transfer fluid between the open and closed ends of the cavity receivers affected the receiver heat gain, thermal efficiency, and exergy efficiency. It was also found that the HTF has the highest exit temperature of 221 °C, with an average radiation intensity of 1032 W/m2. With 48.4 % thermal efficiency and 9.1 % exergy efficiency, the results showed the best performance. When it came to total efficiency, PDC showed its highest value of 46.2 % at 13:17 p.m. on January 4th, 2024.

125 Could yeast derivatives change beef cattle water intake in different scenarios?

Abstract Adequate water intake is linked to greater dry matter intake, heat loss, and productivity. To measure the water intake of beef cattle reared in groups, two experiments were carried out in Brazil (South East/Middle East) using water throughs coupled with scales (Intergado, Betim, Brazil) and RFID individual identification systems, allowing the recording of individual water intake of animals. In experiment 1, young bulls (n = 96; 105 d on feed - feedlot) were randomly assigned to four treatments: 1) Control, no yeast derivative; 2) AY – 7 g·animal⁻¹·d⁻¹, Autolyzed Yeast grown on sugarcane molasses (RumenYeast, ICC, Brazil); 3) YM – 3 g·animal⁻¹·d⁻¹, yeast rich in soluble Yeast Metabolites; 4) YB – 5 g·animal⁻¹·d⁻¹, Yeast Blend (live Yeast plus autolyzed Yeast). Diets (adaptation, growing, and finishing) x treatments were treated as fixed effects on the complete randomized design. In experiment 2, backgrounding bull calves (n = 32) reared on grazing and 710 g/d of protein supplements (90 d) were randomly assigned to two treatments: 1) Control, no yeast derivative; 2) AY – 7 g·animal⁻¹·d⁻¹, Autolyzed Yeast (RumenYeast), the means were subjected to ANOVA analyses. In both experiments, additives were inserted into the diet (mineral premix or supplement), animals were the experimental unit, and differences were declared significant at P < 0.05. Yeast derivatives increased (P < 0.05) water intake in both experiments (Figure 1). The average increment in water intake (L·animal⁻¹·d⁻¹ was 13.9%. Interestingly, the increment in relation to control was noted for all yeast derivatives and scenarios covered by the experiments (feedlot adaptation diet, feedlot growing diet, feedlot finishing diet, and grazing system). Until now, there seems to be no literature explanation for our findings. However, these results could help to explain the positive effects of yeast derivatives on rumen pH, protein microbial flow, and thermal stress since greater water intake increases the passage rate of rumen fluid and body heat loss. Statistical correlations may not be understood as a cause-consequence link. However, when dealing with a new question, correlations may give us a path to go on and investigate. Malheiros et al. (2023) noted a negative correlation between water intake and rumen dimethylamine. Autolyzed yeast can strongly decrease the concentration of rumen methylamines in cows facing subacute acidosis (Humer et al., 2018). Niacin metabolism should also be investigated since its supplementation enhances cows’ blood niacin levels and water intake. Yeast derivatives are rich in niacin, and autolyzed yeast supplementation can increase blood niacin and body heat loss during summer (Dias et al., 2018), probably increasing water need. In conclusion, yeast derivatives increased the water intake of beef cattle, and this finding adds to the understanding of how yeast derivatives supplementation benefits ruminants.

Feature size specific processing parameters for additively manufactured Ti-6Al-4V micro-strut lattices

The material properties of individual micro-struts are critical to the overall success of lattice structures. These properties can be significantly compromised by defects inherited from powder bed fusion processes. Among these defects, porous inclusions are well understood to have a detrimental effect on mechanical properties; posing a high risk to the implant under loading. While the majority of these defects can be avoided through optimisation of printing parameters, this has generally only been done for traditional bulk components with no in-designed porosity. Furthermore, a number of studies have observed changes in the frequency of such porous inclusions as feature size is reduced, indicating a size effect. This also suggests that the optimal parameters for bulk material are not necessarily translatable to the individual micro-struts which build the lattice. In this study, the relationship between parameter optimisation and feature size was investigated. Here, a higher energy density input was required for processing micro-strut lattices with an optimised relative density, than it was for bulk components. This could be attributed to faster rates of heat loss in micro-strut samples on account of their increased surface-to-volume ratio. The consequential improvement in mechanical properties was also assessed. An increase in both strength and stiffness could be largely attributed to an increase in the percentage volume of load bearing material, while improvements in failure strain were largely driven by minimisation of stress concentrations around the irregular pore morphologies. Fatigue properties did not improve beyond the effects of yielding. Rather, crack initiation was dominated by surface defects; which on account of their surface free energy, experience a much higher stress intensity factor.

Thermal storage and loss characteristics of underground water pits of solar district heating systems in Xizang Plateau, China

Large-scale thermal storage systems are crucial for solar district heating systems. Currently, there is less engineering guidance on the heat loss patterns of underground water pits, especially in the special climatic conditions of the Xizang Plateau. Therefore, this study analyzes the heat transfer characteristics of underground water pits in the plateau climate. A cylindrical underground water pit model is constructed, and the heat loss law of underground water pits of the heating season and seasonal heat storage is investigated under multiyear operation. The results show that the heat loss rate of the underground water pit with seasonal heat storage is 0.8 % higher than that of the heating season heat storage for the same volume. The difference in heat loss between the two heat storage modes is small. The heat loss from the top, sides and bottom of an underground water pit accounted for 34.2 %, 36 % and 29.8 % of the heat loss in the first year, respectively. The percentages of heat loss from each surface after ten years of operation were 46.7 %, 36.6 %, and 16.7 %. In addition, the functions of storage volume and heat loss per unit volume of the first year in Xizang were fitted. The relationship equation between heat loss per unit volume of the first year and the annual heat loss per unit volume in the nth year was obtained. This study provides support for the heat loss of underground water pits that operate continuously for many years.

Improved heat transfer mathematical model forpyramid shaped seasonal heat storage water pit and the influence of boundary conditions

Seasonal heat storage can make use of urban waste heat for low-carbon heating throughout the year. Previous models for pyramid shaped water pit have limited adaptability and ignore the impact of soil temperature in the early stages of operation on the performance of water pits. This article combines two classic mathematical models to establish a mathematical model that can adapt to various sizes of inverted pyramid shaped water pits. The validation of this model was conducted using experimental data from 60000 m3 water pit of Dronninglund, and the influence of boundary conditions for this module were calculated and discussed. The results showed that the root mean square errors of the simulated top, bottom, and average temperature of the water pit were 3.07 °C, 2.39 °C, and 1.37 °C, with relative deviation ratios of 4.25 %, 2.27 %, and 6.62 %, respectively. Furthermore, it was found that for every 5 °C increase in the set average soil temperature, the storage efficiency of the water pits increases by 0.4 %∼0.5 %. In the case of common top insulation of the water pit, the total heat loss at the top, side walls, and bottom are 66.83 %, 31.8 %, 1.37 %. While considering comprehensive insulation in all directions, the heat loss rate for the top, side walls, and bottom are similar with the former, being 67.84 %, 30.79 %, and 1.37 %, respectively. The proposal and findings of this article provide a basis for simplified optimization planning and design of large-scale seasonal heat storage systems.

The Chain of Processes Forming Porphyry Copper Deposits—An Invited Paper

Abstract Porphyry-related mineral deposits are giant geochemical anomalies in the Earth’s crust with orders-of-magnitude differences in the content and proportion of the three main ore metals Cu, Au, and Mo. Deposit formation a few kilometers below surface is the product of a chain of geologic processes operating at different scales in space and time. This paper explores each process in this chain with regard to optimizing the chances of forming these rare anomalies. On the lithosphere scale, deposits with distinct metal ratios occur in provinces that formed during brief times of change in plate motions. Similar metal ratios of several deposits in such provinces compared with global rock reservoirs suggest preceding enrichment of Au or Mo in lithospheric regions giving rise to distinct ore provinces. The largest Cu-dominated deposits and provinces are traditionally explained by selective removal of Au during generation or subsequent evolution of mantle magmas, but the possibility of selective Cu pre-enrichment of lithosphere regions by long-term subduction cannot be dismissed, even though its mechanism remains speculative. Evolution of hydrous basaltic melts to fertile magmas forming porphyry Cu deposits requires fractionation toward more H2O-rich magmas in the lower crust, as shown by their adakite-like trace element composition. The prevailing interpretation that this fractionation leads to significant loss of chalcophile ore metals by saturation and removal of magmatic sulfide might be inverted to a metal enrichment step, if the saturating sulfides are physically entrained with the melt fraction of rapidly ascending magmas. Ascent of fertile magma delivers a large mass of H2O-rich ore fluid to the upper crust, along points of weakness in an overall compressive stress regime, within a limited duration as required by mass and heat balance constraints. Two mechanisms of rapid magma ascent are in debate: (1) wholesale emplacement of highly fractionated and volatile-rich granitic melt into a massive transcrustal channelway, from which fluids are exsolved by decompression starting in the lower crust, or (2) partly fractionated magmas filling a large upper crustal magma chamber, from which fluids are expelled by cooling and crystallization. Transfer of ore-forming components to a hydrothermal ore fluid is optimized if the first saturating fluid is dense and Cl rich. This can be achieved by fluid saturation at high pressure, or after a moderately H2O rich intermediate-composition melt further crystallizes in an upper crustal reservoir before reaching fluid saturation. In either case, metals and S (needed for later hydrothermal sulfide precipitation) are transferred to the fluid together, no matter whether ore components are extracted from the silicate melt or liberated to the ore fluid by decomposition of magmatic sulfides. Production and physical focusing of fluids in a crystallizing upper crustal magma chamber are controlled by the rate of heat loss to surrounding rocks. Fluid focusing, requiring large-scale lateral flow, spontaneously occurs in mushy magma because high water content and intermediate melt/crystal ratio support a network of interconnected tubes at the scale of mineral grains. Calculated cooling times of such fluid-producing magma reservoirs agree with the duration of hydrothermal ore formation measured by high-precision zircon geochronology, and both relate to the size of ore deposits. Ore mineral precipitation requires controlled flow of S- and metal-rich fluids through a vein network, as shown by fluid inclusion studies. The degree of hydrothermal metal enrichment is optimized by the balance between fluid advection and the efficiency of cooling of the magmatic fluid plume by heat loss to convecting meteoric water. The depth of fluid production below surface controls the pressure-temperature (P-T) evolution along the upflow path of magmatic fluids. Different evolution paths controlling density, salinity, and phase state of fluids contribute to selective metal precipitation: porphyry Au deposits can form at shallow subvolcanic levels from extremely saline brine or salt melt; high-grade Au-Cu coprecipitation from coexisting and possibly rehomogenizing brine and vapor is most efficient at a depth of a few kilometers; whereas fluids cooling at greater depth tend to precipitate Cu ± Mo but transport Au selectively to shallower epithermal levels. Exhumation and secondary oxidation and enrichment by groundwater finally determine the economics of a deposit, as well as the global potential of undiscovered metal resources available for future mining.

Insights into the development of small-volume long lava flows: A case study of the Coalstoun Lakes Volcanic Field, southeast Queensland, Australia

Long lava flows exceeding 50 km in length are usually produced during large-volume flood basalt eruptions (>100 to 10,000 km3) but can also occur from small to moderate-volume (<30 km3) basaltic eruptions in continental intraplate monogenetic volcanic fields. Eruptive volume, therefore, is not an a priori barrier to producing long lava flows. Key factors that promote long lava flows include efficient lava transport systems that minimise heat loss, long-lived and sustained effusion rates to maintain flow advancement, and lava flow across low topographic gradients (<1°-10°) with minimal topographic barriers.Here, we focus on an anomalously young and poorly studied basaltic monogenetic volcanic field in southeast Queensland, Australia, that formed part of the broader intraplate volcanism in eastern Australia since the Late Cretaceous. The Coalstoun Lakes Volcanic Field (CLVF) comprises three lava fields: the Barambah Basalt Flow Field, the Deep Creek Flow Field and the Hunters Hill Flow Field. Basalt from the Barambah Basalt Flow Field has been redated here by Ar40/Ar39 analysis of groundmass material, yielding a weighted mean age of 0.520 ± 0.016 Ma. The Barambah Basalt Flow Field contains most of the eruptive volume and has advanced up to 165 km from the vent. The Hunters Hill and the Deep Creek flow fields are comparatively smaller in volume and have advanced ∼30 and ∼ 20 km from the vent, respectively. Lava tubes are only known from proximal regions and do not appear to be a significant factor in promoting long run-out in the CLVF. Flow confinement and utilisation of existing drainage networks are features of both lava flow fields, and advancement down the sand-based and ephemeral Burnett River significantly promoted long run-out despite low topographic gradients.New whole-rock geochemical data on our CLVF samples indicates that all lavas are hawaiites, a common feature of other Quaternary long lava flows globally. Overall, there is some compositional variation, but a cryptic zonation is readily apparent in trace element abundances, which helps to further distinguish the flow fields as the products of separate but closely spaced eruptions. The combination of field and geochemical data indicates that the long lava flow of the Barambah Basalt Flow Field resulted from a sustained and relatively low effusion eruption, creating a pāhoehoe flow field that continuously advanced across the landscape, utilising a drainage system that guided lava flow and helped to circumvent any topographic barriers.

A comparative evaluation of energetic and exergetic performance parameters in syrup purification and evaporation lines

AbstractConsidering the global challenges of environmental destruction, limited fossil reserves, and the reduction of the share of energy in the final price of the product, a detailed evaluation of energy‐intensive systems is needed to improve performance. The syrup heating process is one of the basic processes in sugar factories. In this study, the syrup heating system in the purification and evaporation lines, located in the Urmia sugar plant, was evaluated, analyzed, and compared with energy and exergy analysis. Also, the subsystems of the syrup heating process were evaluated with thermodynamic analysis. Mass, energy, and exergy balances were carried out by coding in EES software, and energetic and exergetic operational parameters were extracted. The heat loss rate and exergy destruction rate in the syrup heating system of the purification line were calculated as 121.29 and 404.36 kW, respectively, and in the syrup heating system of the evaporation line as 112.70 and 238.62 kW, respectively. The recovery potential rate was 134.99 kW for the purification line and 37.70 kW for the evaporation line. The stability index and exergy efficiency for the purification line were calculated as 3.03% and 67.01% for the purification line and 6.54% and 84.71% for the evaporation line. The results of the thermodynamic analysis showed that the syrup heating process in the purification line has weaker performance from the energetic and exergetic point of view, is accompanied by large losses, and imposes a greater environmental burden. Accordingly, it is suggested that the improvement of the syrup heating performance in the purification line should be prioritized for engineering optimization and redesign in sugar processing plants.Practical applicationsMonitoring the operational state of the systems and determining system losses are critical steps in food thermal processing. A practical and accurate method to evaluate the purification and evaporation lines is required to improve the thermal efficiency. According to exergy analyses, the performance of the syrup heating process in the purification line is low due to large losses and imposes a greater environmental burden. Therefore, the improvement of the syrup heating performance in the purification line should be prioritized for engineering optimization and redesign in sugar processing plants.

The Critical Ambient Temperature Threshold for Safe Fan Use in Young Adults During Extreme Heat Exposure

Introduction: The electric fan may be an effective, low-cost heat resilience solution during extreme heat. Fans have been shown to attenuate the rise in cardiovascular and thermal strain relative to still air in young adults, particularly during exposure to more humid conditions. When ambient temperature exceeds skin temperature, a fan improves sweat evaporation from the skin surface, which counterbalances the increased rate of convective heat gain. However, at higher air temperatures, the increased convective heat gain may exceed the rate of evaporative heat loss resulting in net heat gain and increasing physiological strain. The purpose of the present study was to identify the critical ambient temperature limit, where increased physiological strain will be observed, with a fan in comparison to still air. Method: To date, 6 participants (4 females; 24±9 y; 72.8±17.8 kg; 1.8±0.2 m) have completed two 180-minute temperature ramp heat-exposures (37°C to 47°C at ~0.05°C/min, 25%RH) on separate days. Wearing standardized t-shirts and shorts, the participants remained seated while either i) facing an electric fan (5.3±0.9 m/s) or ii) in still air (0.1±0.0 m/s). Rectal and skin temperature, heart rate, blood pressure, whole-body sweat loss, thermal comfort, and thermal sensation were measured every 10 minutes. Results: Rectal temperature was similar between fan and still air up to 43°C (P&gt;0.92), however was greater with a fan from 44°C onwards (p&lt;0.05). Skin temperature was higher with a fan compared to still air throughout the exposure (p&lt;0.001). Heart rate was similar between fan and still air until 44°C (P&gt;0.61), after which heart rate was higher with a fan (p&lt;0.05). Mean arterial pressure was not different between fan and still air at any air temperature (P=0.53). The rate pressure product was higher with a fan compared to still air when the ambient temperature exceeded 44°C (p&lt;0.05). Whole-body sweat losses were greater with a fan (1215±250 g) compared to still air (675±103 g, P=0.006). No differences between fan and still air were observed for thermal comfort (P=0.22) or thermal sensation (P=0.73) throughout the temperature ramp protocol. Conclusion: When ambient temperature exceeds 43°C, electric fan use results in greater physiological strain at rest in young healthy adults relative to still air. This research was supported by Dr. Ravanelli’s Natural Sciences and Engineering Research Council of Canada Discovery Grant (PIN#2022-05096). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Quenching extinction of solid sphere diffusion flames induced by a sudden removal of gravity

The response of a diffusion flame around a PMMA solid sphere to a sudden transition to zero-gravity is investigated both experimentally and numerically. The initial flame is established in normal gravity with a low speed forced flow in a 17% oxygen by volume atmosphere. An abrupt (step change) normal-to-zero gravity transition occurs when the test package is released in the drop tower. The dynamic flame response is recorded by video and modeled numerically. By the end of the 5.18-s drop, the flame tip retreats, and the flame base may either remain stabilized near the forward stagnation region or extinguish depending on several parameters. The two parameters investigated are: forced flow velocity and the degree of preheating in the surface layer of the solid sample. The amount of preheating or equivalently the conductive flame heat loss rate to the solid interior is varied by controlling the duration of the normal gravity burning before releasing to microgravity. The heat loss is quantified by using embedded thermocouples to measure the solid subsurface temperature gradient near the stagnation point. The detailed numerical model reveals details of the flow field and flame structure including oscillatory extinction and quantifies the various transient gas-solid surface energy balance terms.

Long-term heat storage opportunities of renewable energy for district heating networks

This study compares different thermal heat storage solutions existing in the market, fuelled with energy from different renewable energy sources with a focus on integrating thermal heat storage into the district heating grid. The paper is based on a case in the municipality of Silkeborg, Denmark, which has the largest solar thermal panel plant in Northern Europe. A theoretical approach was used to compare with assumed excess power from wind and solar in the DK1 area, with Silkeborg's allocated excess power at 0.01%. This yielded overall efficiencies between η = 0.739–0.765 and η = 0.864–0.895 for the Silkeborg solar thermal plant. Four different thermal heat storage solutions were compared: tank thermal energy storage, pit energy storage, aquifer thermal energy storage and borehole energy storage (BTES). The analysis showed that, of the four solutions compared, BTES was the best for storing thermal energy for a longer period of time, with the lowest heat loss rate of 0.6% and the highest efficiency of up to 89.5%. However, some complications make it difficult to establish a BTES storage solution, since it is very much dependent on earth conditions and initial capital.

Enhancement the solar box cooker performance using steel fibers

AbstractThe use of fossil fuel and wood for cooking poses health, environmental, and economic challenges, especially with the growing population. This has led to an increase in the trend towards the use of clean and sustainable cooking sources, including solar cookers. This experimental study aims to contribute by enhancing the performance of a solar box cooker (SBC) according to the concept of porous media via adding steel fibers inside the box as a modified SBC and comparing it with a conventional SBC. The stagnation test to determine the first figure of merit and the load test to determine the second figure of merit, standard boiling time, and cooker optothermal ratio were conducted under the outdoor conditions of Baghdad city. Also, an energy and exergy efficiency analysis, and calculating the rate of heat loss by three water loads heating and cooling tests. The results revealed that the modified SBC has a higher thermal performance than the conventional SBC.

Lunar Mare Lava Flow Dynamics and Emplacement: Predictions of Non-Newtonian Flow Dynamics, Syn- and Post-emplacement Cooling and Volatile Release Patterns, and Vertical and Lateral Flow Structure Development

We apply basic principles of magma ascent from deep source regions and its eruption into a low-gravity vacuum environment to develop a theoretical treatment of the fluid dynamics and thermodynamics of mare basalt lava flow emplacement and evolution on the Moon. The vacuum conditions influenced the release of volatiles in magma passing through lava fountains, thus controlling the syn- and post-emplacement vesicularity of the resulting deposits. To explain observed lengths and volumes of Mare Imbrium–type flows, high (106–105 m3 s−1) initial magma eruption rates were needed. Combined with low lunar magma viscosity, these caused flows to be initially turbulent. Resulting high radiative heat loss and consequent high crystallization rates caused rapid non-Newtonian rheological evolution and suppression of turbulence at tens of kilometers from vents. Slower cooling rates in the subsequent laminar parts of flows imply distinctive crystal growth rate histories. In a four-phase sequence, (i) initial transient dike-tip gas release followed by (ii) Hawaiian fire fountain activity with efficient volatile loss (iii) transitioned to (iv) Strombolian explosions in a lava lake. Late-stage lava now able to retain volatiles intruded and inflated existing flow deposits after flow front advance ceased. Volatiles forced out of solution by second boiling as lava cooled caused additional inflation. Low gravity and lack of atmospheric pressure commonly produced very vesicular lava. Escape of such lava through cracks in flow crusts is a possible source of ring-moat dome structures; collapse of such lava may explain irregular mare patches.

Физиологические показатели равнозубой бурозубки (Sorex isodon, Eulipotyphla) при непродолжительном пребывании в холодной воде

The physiological indices of small mammals caught in the natural environment are used to assess their living conditions, analyze the impact of various factors on populations, identify the mechanisms of animal adaptation to these factors, and for other purposes. At the same time, pitfall traps with water are often used to capture animals, especially shrews. The water temperature in such traps is characterized by rather low values. Even a relatively short stay of animals in cold water can lead to changes in their physiological parameters, which must be taken into account. The aim of this study was to evaluate such changes in shrews, on example of Sorex isodon. The variability of the physiological parameters of shrews during immersion in cold water is also of interest from the point of view of their physiology of thermoregulation. Shrews are among the smallest mammals, and therefore are characterized by high rates of heat loss. At the same time, these animals are active all year round and are widely distributed in the northern regions, where they are often exposed to acute cold exposure. The physiological mechanisms of adaptation of shrews to such conditions are still insufficiently studied. The study was conducted in late July-August 2016 on immature young-of-the-year even-toothed shrews (Sorex isodon Turov, 1924). The capture of shrews was carried out in the vicinity of Magadan (Russia). Before the start of the experiment, the caught animals had been kept individually for 2 days in plastic containers (37x26x26 cm) at room temperature with the provision of water and food ad libitum. Control animals were decapitated under ether anesthesia after keeping. The experimental animals were placed in a container with water preliminarily cooled to 4.5-9°C (6.5°C on average). After the swimming intensity of the shrews significantly decreased, they were also subjected to anesthesia and decapitation. The experimental group consisted of 22, and the control group consisted of 21 animals. The following physiological indices were determined in the shrews: blood glucose level, glycogen and lipid content in the liver, mass of internal organs and fat reserves, and the number of bone marrow cells in the femur. For statistical analyses, the Mann-Whitney U-test was used. The average swimming time of S. isodon in the experiment was 5.8 minutes. A relatively short immersion in cold water led to a significant change in the values of some physiological parameters in S. isodon. The indices of energy metabolism showed greatest differences between the control and experimental groups of animals. The level of blood glucose in S. isodon in the test group was significantly higher (See Fig. 1). On the contrary, the liver glycogen content in shrews sharply decreased after the experimental treatment. The level of this carbohydrate in the experimental group was 80% less than in the control. Acute cold exposure also provoked a fairly rapid change in the mass of fat reserves in S. isodon. The absolute and relative mass of the interscapular adipose tissue of S. isodon decreased by 11.9% and 10.7%, respectively, and that of the inguinal adipose tissue, by 20.9% and 18.8%, respectively (See Table 1). Differences in the mass of some shrew organs were also significant. The absolute and relative weight of the spleen was higher in the experimental animals. After exposure to cold water, S. isodon also had a higher relative heart mass than controls, although the differences in the absolute mass of this organ were insignificant. On the contrary, the absolute mass of shrew kidneys decreased after immersion in cold water. All other physiological indices showed no significant differences between the groups of control and experimental S. isodon. Thus, a relatively short stay of shrews in cold water provokes a significant change in the mass of their adipose tissue and some organs. High demand for glucose during acute cold stress leads to rapid depletion of liver glycogen. The rate of reduction of fat reserves in shrews under cold exposure is also quite high and exceeds that of most other mammals. It is known that in regions characterized by severe climatic conditions, the rate of reserve fat mobilization is of great importance for the survival of small mammals. The ability to quickly store and spend fat reserves, therefore, seems to be an important adaptation of shrews to living in cold climates.

Simple model combined with data assimilation to forecast buoyancy-driven ceiling jet propagation in tunnel fires

Faster-than-real-time forecast for the ceiling jet head propagation is crucial for evacuation guidance and rescue operation in the early stages of tunnel fires. The ceiling jet head propagation is driven by buoyancy and thus significantly dominated by the heat transfer process in the head region. Simplified models have been established but proved challenging in forecasting complex dynamic processes. The cumulative deviations induced by the model limitations and the input parameter uncertainties lead to distorted forecast during the ceiling jet dynamic propagation process, thereby constraining the applicability of such models in practical scenarios. In this study, an assimilation method, the ensemble Kalman filter (EnKF), was combined with a simple theoretical model to forecast the ceiling jet propagation. Using the EnKF to assimilate the monitored local data, the key input parameters such as mass flow rate m˙ and the temperature of the ceiling jet head Ts are corrected in real time, thus alleviating model prediction deviation. Meanwhile, a heat loss rate correction coefficient λα, introduced to correct the heat loss rate during the ceiling jet propagation process, is dynamically estimated as well. This enables the model to characterize the heat transfer process more accurately, consequently ensuring faster-than-real-time forecasts of the subsequent propagation stage. Finally, the forecasting effectiveness of the proposed combined method was examined in a 1:6 reduced-size experimental tunnel fire scenario and full-scale simulated tunnel fire scenarios with various fire source locations, tunnel geometries, and suddenly changing HRR. In response to the demand of minimizing both the type and quantity of sensors in practical applications, a factor analysis was also performed to examine the robustness of this method. The results exhibited good adaptability to different fire scenarios with very limited monitored data.

Effect of adiabatic ground on thermofluidic behavior and cooling time analysis from a hollow tube

Efforts are made to elucidate natural convection around a tube placed on/close to the adiabatic ground in a stagnant ambient air within laminar regime. Thermofluidic characterization is carried out by employing important governing input quantities, such as Rayleigh number gap and aspect ratio The heat loss rate from the inner surface drops abruptly when the tube is placed on the ground. The growth rate of heat loss rate with is relatively more abrupt at higher value of for a constant Nusselt number on outer wall is found to increase monotonically as grows continually for a constant and whereas an opposite trend is anticipated for Nusselt number on inner wall The reduction gradient of with is considerably lower at lower value of in comparison to higher Again, two distinguished zones are identified (Zone A and B), namely, (i) zone A, where the effect of ground on the thermofluidic behvaiour around the tube is observed, and (ii) zone B suggests no effect of ground. Furthermore, cooling time estimation is performed by considering the initial temperature of the cylinder as the wall temperature at time 0 s. The required cooling time reduces considerably with the rise of for a particular and Lastly, a new correlation for Nusselt number has been anticipated. It shows quite satisfactory agreement within ±6% of the computational data.

NUMERICAL ANALYSIS OF COMPOUND PARABOLIC SOLAR COLLECTOR WITH TWO GLASS COVERS

In a compound parabolic solar collector, a glass cover is normally used for decreasing the rate of heat loss from the absorber. In this paper, a solar collector with two glass covers and a concentration ratio of 1.6 is simulated and examined for the purpose of higher performance. The distance between covers is 45 mm and the cavity of solar collector is filled with air. Due to the temperature gradient, the turbulent free convection airflow takes place inside the cavity. As the main aim, the effect of the second glass sheet on performance improvement is examined. Towards this end, the equations govern to the turbulent buoyant airflow in the collector’s cavity was numerically solved by the finite element method using the COMSOL Multiphysics software. Also the conduction equation is employed for temperature computation in the solid elements. Numerical findings demonstrate the effective role of the second glass sheet in decreasing the rate of heat loss from solar collectors and a more than 6% increase in the thermal efficiency of the studied test cases is found because of the second glass sheet. Comparison between the numerical findings of free convection airflow with experimental data shows good consistency.

Neutrino Emission of Neutron-Star Superbursts

Superbursts of neutron stars are rare but powerful events explained by the explosive burningof carbon in the deep layers of the outer envelope of the star. In this paper we perform a simulation ofsuperbursts and propose a simple method for describing the neutrino stage of their cooling, as well as amethod for describing the evolution of the burst energy on a scale of several months. We note a universalrelation for the temperature distribution in the burnt layer at its neutrino cooling stage, as well as theunification of bolometric light curves and neutrino heat loss rates for deep and powerful bursts. We pointout the possibility of long-term retention of the burst energy in the star’s envelope. The results can be usefulfor interpretation of superburst observations.