Reduction Of Heat Load Research Articles

Unintended consequences of English school stock energy-efficient retrofit on cognitive performance of children under climate change

School building stock retrofit forms a key part of UK's commitment to net-zero carbon target by 2050. However, with a changing climate, the retrofit of school buildings may have unintended consequences on classroom thermal environments and cognitive performance of children in non-heating seasons. This paper aims to quantify the impact of school stock retrofit in accordance with increasingly tightening energy efficiency regulatory requirements on cognitive performance of English children, while also exploring the potential adaptation measures under climate change. The results indicate that English schools that undergo envelope insulation exhibit higher Cognitive Performance Loss (CPL) of children compared to their original conditions. Passive climate adaptation measures, especially increased daytime ventilation rate was found to be an effective strategy for mitigating the impact of climate change on cognitive performance. However, the benefits of passive measures will diminish as the climate warms, while air conditioning will be required to maintain cognitive performance loss at relatively low levels. In addition to the reduction of heating load, envelope insulation can provide benefits for English schools in cooler climatic regions from both cognitive performance and energy point of view. The study calls for the CPL to be added as one of the key performance indicators when considering the long-term impact of climate change on schools. This would enable policy makers and relevant stakeholders to make more holistic decisions regarding school stock retrofit while ensuring that classrooms are conducive to learning.

Experimental and numerical investigation of integrating energy recovery ventilation into a thermodynamic-potential-based passive dehumidification system using renewable energy

To decrease the latent heat load of the air-conditioning system in residential buildings, we proposed a passive dehumidification and mechanical ventilation system that integrates energy recovery ventilation (ERV) into a passive dehumidification and solar collection (PDSC) system that can intelligently regulate the indoor hygrothermal environment, referred to as the PSE (PDSC & ERV) system. Field studies were conducted by monitoring the indoor temperature and humidity changes in the operating conditions using various systems. With the PSE system, the absolute humidity difference between the indoor and outdoor air was the most significant, and its ability to maintain a stable indoor relative humidity was the most remarkable compared with other systems. The PSE model had the lowest latent and total heat load compared with the exhaust-only ventilation model equipped with a standard insulated envelope without moisture adsorption and desorption function. Regression analysis showed that the higher the outdoor temperature, absolute humidity, relative humidity, and solar radiation in summer, the more significant the PSE system's latent heat load reduction effectiveness. Linear correlation between absolute humidity and energy-saving performance was the most evident, with a coefficient of determination as high as 0.98, illustrating the suitability of PSE systems for hot and humid areas.

Reduction of heat load in an air-conditioned bus employing phase change material integrated glass window and roof: A coupled numerical and analytical approach

The study aims to analyze the heat load in an air-conditioned bus cabin by attaching a layer of phase change material to its roof and window glass. Enthalpy equation coupled with momentum and continuity equations has been solved in PCM layer, whereas only the diffusion equation is solved in roof and glass to obtain the spatiotemporal distribution of the temperature. A significant reduction in temperature on the inner and outer surfaces of the glass window and roof is noticed when PCM is attached. The inner surface of the glass shows a temperature reduction from 310 K to 301.5 K at 2.00 P.M, whereas the roof reveals a significant decrease of 14 K temperature when PCM is glued underneath. PCM helps keep the temperature at the inner surface under 302 K up to 12.00 pm However, the temperature rises to 308 K when PCM is not attached. The PCM thickness has a significant impact on temperature. An increase in thickness from 6 mm to 12 mm leads to a temperature reduction of 3 K to 4 K. Focusing on the performance of PCM, Na2SO4.10 H2O as a PCM is found to be beneficial since the phase change process (liquid fraction between 0 and 1) exists for a longer duration due to its high latent heat of fusion. The reduction in temperature using PCM is implicitly reflected in curtailing the total heat load in the cabin. Approximately 5 kW (45%) reduction in total heat load has been achieved using a 12 mm PCM layer on glass and roof during the peak time of solar radiation, substantially saving fuel and battery energy.

Comprehensive evaluation on conjugate heat transfer and thermal stress performance of film cooling

Film cooling is a commonly used cooling technology in gas turbines, which could reduce heat load by spreading cooling air. However, it faces the problem of stress concentration in structures with holes. The present work focuses on conjugate heat transfer and thermal stress characteristics for a flat film cooling plate through an experimentally validated numerical approach. It discusses the effect of three geometry factors: inclination angle, compound angle, and ellipticity. An engine case simulation and a laboratory case simulation are compared to validate the analogy principle of conjugate heat transfer and thermal stress analysis derived from theoretical analysis. According to the analogy principle, the laboratory flat plate film cooling cases are set to conduct numerical studies. The maximum Mises stress of the film hole is equal to the product of the reference stress and the stress concentration factor. The reference Mises stress is proportional to the overall cooling effectiveness. The stress concentration factor is mainly related to the geometry of the film hole. Reducing the inclination angle of the film hole from 90° to 30° increases the overall cooling effectiveness and drastically increases the stress concentration factor from 2.7 to 5.5. Based on a cylinder hole with a 30° inclination angle, increasing the compound angle enhances the overall cooling effectiveness and slightly increases the stress concentration factor. Based on a cylinder hole with a 30° inclination angle, increasing the ellipticity increases the overall cooling effectiveness and reduces the stress concentration factor. With the increase of ellipticity from 0 to 4, the stress concentration factor decreases from 5.5 to 2. Elliptical film holes are ideal for future low-stress, high-cooling-efficiency turbine blades to extend the life of cooling vanes.

Experimental and numerical study on thermal performances of a modular hydronic thermal barrier wall with heat injection system in filler cavities

The hydronic thermal barriers with dynamically adjustable thermal performance have become one of the highly anticipated solutions for opaque envelope insulation while improving the efficiency of the use of low-grade energy. In response to the technical constraints encountered by conventional hydronic thermal barrier walls (i.e., CHTBs) when it comes to enhancing heat transfer, the concept of modular hydronic thermal barrier walls (i.e., MHTBs) was introduced. The MHTB incorporates a heat injection system within its filler cavities, a feature designed to promote the overall thermal performance of the opaque enclosure structure. The performance enhancement described is mainly achieved through active management of the thermal conductivity of the filling material within the vicinity of fluid pipes. In this study, field thermal performance assessments were carried out during winter conditions in three reduced-scale experimental rooms. The southern boundary of these test rooms adopts walls with different configurations, i.e., MHTB, CHTB, and traditional thermal insulation wall. Subsequently, a comprehensive investigation regarding the impacts of filling materials on the energy performances of MHTB was conducted through numerical simulations. The outcomes demonstrated a substantial reduction in heat loss through the south wall by using MHTB, leading to reduced room thermal discomfort. In particular, with a charging temperature set at 35.0 °C, the inner surface temperature of MHTB displayed a noteworthy increase of 10.3 °C compared to that of the traditional thermal insulation wall, resulting in a significant reduction in heat load by a factor of 7.4. Additionally, it was observed that the filler material within the pipe cavity played a vital role in shaping MHTB's thermal performance. For instance, considering the case with a heat injection temperature of 25.0 °C, a doubling of thermal conductivity resulted in an enhancement of 0.24 W/m2 in heat gain on the outer surface and an overall increase of 0.04 MJ in total injected heat. This study demonstrated the positive effect of MHTB on optimizing the efficiency of hydronic thermal barriers and guided their further application and research.

The behavior and control of injected impurity in the closed divertor of HL-2A

Excessive heat load on the divertor target has been identified as a major challenge for present and future tokamaks. Divertor detachment achieved by injecting radiating impurity is an effective method to reduce heat load onto the divertor target surface. However, extremely serious effects on the core plasma could be given by the injected extrinsic impurity, such as fuel dilution and cooling due to energy radiation loss by the impurity in the core plasma region. Therefore, understanding the impurity behavior and then controlling the impurity content during divertor impurity injection are important issues of a tokamak. The closed divertor has the advantage of realization of divertor detachment and the Huan Liuqi-2A (HL-2A) tokamak has a very closed symmetrical divertor structure. In this work, experiments and SOLPS-ITER simulation gave the picture of the impurity behavior and showed that the friction force can play a more key role in screening and controlling radiated impurity, comparing with pressure/temperature gradient force during detachment in HL-2A with the closed divertor. Increasing the degree of divertor detachment (DoD), the screening ability of the divertor is strengthened, which is conducive to the control of impurity ions. It implies that the injected impurity can be confined in the closed divertor under detachment and, to some extent, the effect of DoD or impurity gas flux on main plasma can be attenuated for HL-2A with extrinsic impurity gas injection. During divertor detachment, the screening effect of N+ and Ar+ ions is stronger than that of Ne+ ions. As a result, the behavior and control of impurity with impurity injection in the closed divertor of HL-2A are presented with experimental and simulated results, which gives meaningful understanding and suggestion for heat load mitigation and controlling the effect of impurity in HL-2A and other tokamaks.

Effect of typical low-impact development measures on control of thermal loads from urban stormwater runoff

Ground hardening in urban areas increases the risk of thermal enrichment in surface rainwater runoff. Moreover, the thermal pollution from rainwater runoff has become an important problem that damages the urban aquatic environment. Current studies have focused mainly on the potential hazard caused by runoff thermal pollution to aquatic microorganisms. However, there are few studies on the efficacy of controlling runoff thermal load through low-impact development (LID) and renovation in urban areas. The effects of LID modification were evaluated by monitoring the characteristics of the runoff thermal load on each underlying surface in the study area and conducting laboratory-scale bioretention experiments. The results showed that the initial thermal effect of each underlying surface was significant after the start of rainfall, based on the thermal load. Ceramic granules are remarkable bioretention fillers. Their average heat load and volume reduction rates are 55.6 % and 32.7 %, respectively. After LID modification, the thermal load of surface runoff in the study area decreased to 73.42 % under similar rainfall conditions. After the secondary treatment of the bioretention facility, the total thermal load of the outflow facility was 31.40 % of that before renovation. The peak thermal load reduced by 69.15 % and was delayed for 10 min. The control effect differed statistically.

CLEAN: Cryogenic Link for Electric Aircraft Propulsion

We propose a thermally efficient and power-dense high-temperature superconducting (HTS) cable (CLEAN Cable) as well as a thermally efficient, mechanically rugged, and easily attachable/detachable cryogenic-to-ambient power link (CLEAN Connector). The bundled design enables high gravimetric power density and node-less tapping of power. The CLEAN Connector minimizes ambient heat leaking into the cryogenic environment by magnetically coupling the cryogenic section to the ambient counterpart via a high-frequency isolated DC/DC converter. The proposed high-frequency operation reduces the core size of the cryogenic/ambient transformer that provides electrical and thermal isolation while enabling quick connection. The proposed CLEAN technologies provide the following advantages – (1) Reduced heat load; (2) High gravimetric power density; (3) <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> –1 system redundancy; (4) Minimum ambient heat leak into the cryogenic system; (5) High vibration/mechanical stress tolerance; (6) Partial discharge (PD) free at high-altitudes; (7) Easy cryogenic and ambient system connection; (8) Inherent fault detection and isolation.

Shade of solar panels relieves heat load of sheep

Use of solar panels as shading resource combines better animal welfare, generation of renewable energy and animal production in the same area. This concept is termed Animal Agrivoltaics. In this study we integrated behavioural and physiological data in order to determine benefits provided by shade of solar panels on heat stress indicators of sheep. Nine adult Corriedale ewes (Body mass: 70 ± 12 kg; fleece length: 70 ± 5 mm) had miniature temperature loggers attached on them for every-minute samplings of wool-surface, skin and vaginal temperature, from 08:00 to 17:00 h, along 20 consecutive days. Ewes also had shade-use behaviour directly and continuously monitored. Ewes were kept in a paddock shaded with a roof structure that consists of ten photovoltaic panels (shade availability: 2.14 m2 animal−1). Over the study period, ewes were exposed to levels of solar radiation as much as 900 W m−2. From 08:00 to 17:00 h, regardless of the duration of sun exposure or in the shade of solar panels, the vaginal temperature of ewes remained within a narrow range (38.5 ºC - 39.2 ºC). At levels of solar irradiance above 500 W m−2, ewes increased wool-surface temperature by 10 ºC and skin temperature by 2 ºC with increasing heat load and time exposed to sun. Under such circumstances, they were more likely to move to shade of solar panels. Between 10:00 and 14:00 h, shade of solar panels provided to ewes 30 % less radiant heat load than if they were exposed to sun. As a result, as the time in shade increased, the wool-surface temperature of ewes was reduced by 7 ºC - 8 ºC, and skin temperature by 1.0 ºC - 1.5 ºC. In conclusion, this study provides strong evidence that shade of solar panels efficiently reduces heat load in sheep.

An innovative approach to the improved radiating divertor concept by supersonic molecular beam injection on HL-2A

The ‘puff-and-pump’ radiating divertor condition is a promising approach for the reduction of excessive thermal power loading on the divertor targets. The divertor supersonic molecular beam injection (SMBI) system installed on HL-2A strongly enhances the capacity of the divertor heat load control. This system has a faster time response than the divertor gas puffing (GP) system. Divertor heat load control capacity has been compared between these two techniques by experiments on HL-2A and simulations. Experimental results suggest that the divertor SMBI system reduces the divertor heat flux peak to a lower level with less time delay than that for the divertor GP system, owing to a higher injection rate and particle velocity. Simulations by SOLPS demonstrate that a high injection rate shortens the function time which is defined by the time interval between the arrival of the particles at the divertor plasma edge and the reduction of divertor electron temperature. High velocity of SMBI injected neutral gas particle also shortens the particle flight time to arrive at the edge. Less flight time and function time lead to a faster response of the divertor SMBI system compared to the divertor GP system. In addition, simulations by EMC3-EIRENE also suggest that, compared to the GP system, stronger heat load reduction of the SMBI system can also be caused by deeper deposition of gas source owing to its higher particle velocity.

Optimizing energy efficiency in HSCW buildings in China through temperature-controlled PCM Trombe wall system

This study investigates the use of PCM-TWS (phase change material Trombe wall) as a solution for improving energy efficiency in HSCW region buildings in China. The study found that the optimal parameters for PCM-TWS include a phase change temperature of 20–30° Celsius, a latent heat of 175–225 kJ/kg, and an air gap and indoor air exchange rate of 0.12 m³/s. The results indicate that the use of PCM-TWS can significantly reduce heat load and improve thermal comfort, with a 71.53% reduction in heat load during the heating season. The payback period for the PCM TWS investment ranges from 6.56 to 11.18 years, the investment in PCM TWS appears to be attractive and economically valuable. This study contributes to the current body of knowledge on the use of PCM TWS for improving energy efficiency in HSCW buildings in China.

Recent progress of plasma exhaust concepts and divertor designs for tokamak DEMO reactors

The power exhaust concept and an appropriate divertor design are common critical issues for tokamak DEMO design activities which have been carried out in Europe, Japan, China, Korea and the USA. Conventional divertor concepts and power exhaust studies for recent DEMO designs (Pfusion = 1 – 2 GW, Rp = 7 – 9 m) are reviewed from the viewpoints of the plasma physics issues and the divertor engineering design. Radiative cooling is a common approach for the power fusion scenario. Requirements on the main plasma radiation fraction (fradmain = Pradmain/Pheat) and the plasma performance constrain the divertor design concept. Different challenges contribute to optimizing the future DEMO designs: for example, (i) increasing the main plasma radiation fraction for ITER-level Psep/Rp designs and simplifying the divertor geometry, and (ii) extending ITER divertor geometry with increasing divertor radiation (Praddiv) for larger Psep/Rp ≥ 25MWm−1 designs. Power exhaust simulations with large Psep = 150 – 300 MW have been performed using integrated divertor codes considering an ITER-based divertor geometry with longer leg length (1.6 – 1.7 m), as in a common baseline design. Geometry effects (ITER like geometry or more open one without baffle) on the plasma detachment profile and the required divertor radiation fraction (fraddiv = Praddiv/Psep) were key aspects of these studies. All simulations showed that the divertor plasma detachment were extended widely across the target plate with a reduction in the peak heat load of qtarget ≤ 10 MWm−2 for the large fraddiv = 0.7 – 0.8, while the peak qtarget location and value were noticeably different in the partially detached divertor. Simulation results also demonstrated that radial diffusion coefficients of the heat and particle fluxes were critical parameters for DEMO divertor design, and that effects of plasma drifts on outboard-enhanced asymmetry of the heat flux, suggested the need for longer divertor leg to ensure the existence of a detached divertor operation with qtarget ≤ 10 MWm−2.Integrated design of the water cooled divertor target, cassette body (CB) and cooling pipe routing has been developed for each DEMO concept, based on the ITER-like tungsten monoblock (W-MB) with Cu-alloy cooling pipes. Engineering design adequate under higher neutron irradiation condition was required. Therefore, inlet coolant temperature (Tcool) was increased. In current designs, it still shows a large potential variation between 70 °C and 200 °C. The influence of thermal softening on the Cu-alloy (CuCrZr) pipe was fostered near the strike-point when the high qtarget of ∼10 MWm−2 was studied. Improved technologies for high heat flux components based on the ITER W-MB unit have been developed for EU-DEMO. Different coolant conditions (low- and high-Tcool) were provided for Cu-alloy and reduced activation ferritic martensitic (RAFM) steel heat sink units, respectively. The high-Tcool coolant was also considered for the CB and supporting structures. Appropriate conditions for the high-Tcool coolant, i.e. 180 °C/ 5 MPa (EU-DEMO) and 290 °C/ 15 MPa (JA-DEMO, CFETR and K-DEMO), will be determined in the future optimizations of the divertor and DEMO design.

Metal–Organic Frameworks (MOFs) Based Electrospun Nanofiber Membrane for Passive Indoor Moisture Control

Metal–organic frameworks (MOFs), an emerging class of porous sorbents, have become one of the most promising functional materials for indoor moisture regulation. However, the practical application of MOFs in building environments is challenging. Common shaping forms of MOFs (e.g., pellets, tablets, monoliths, granules, coating, etc.) may lead to agglomeration of MOF particles, higher usage costs, low efficiency, and material waste. Here, we report a new MOF-based electrospun nanofiber membrane with high porosity, light weight, and a large surface-area-to-volume ratio. MOF nanoparticles distributed on the fibers can fully contact moisture in the air, thus significantly enhancing MOFs’ utilization and performance. The results of the moisture adsorption test show that the improved MOF membrane has significantly higher water vapor uptake than most conventional hygroscopic materials and textiles in built environments. A building energy model was established to evaluate the MOF membrane’s effect on building energy consumption under different climates worldwide. The simulation results show that the MOF membrane can efficiently moderate indoor moisture fluctuation and has excellent energy-saving potential. The latent heat load reduction rate in summer can be up to 80–90% in arid/semi-arid climates and around 50% in temperate climates in a purely passive manner.

Experimental study on sorption–desorption characteristics of natural composite desiccant with metal embedment

The present study investigates the effect on total moisture sorption, moisture sorption rate, moisture desorption rate, and reduction in the temperature of dehumidified air of metal-embedded natural composite desiccants (MENCDs), which can be used in dehumidification systems. A natural composite desiccant, in which the unutilized portion of the spherical desiccant material is replaced with a metallic ball, is proposed. Stainless steel balls with a diameter of 4.75 and 6.35 mm are used to make different thickness ratios (TR = 1, 0.525, and 0.365) of MENCDs. The natural composite desiccant is prepared from dried cow dung and polyvinyl pyrrolidone with a ratio of 3:1. Experiments are conducted to find the optimum thickness ratio of MENCDs. The total moisture sorption, moisture sorption rate, total heat load reduction, and exergy efficiency of these dehumidification systems are investigated under different relative humidities (RH = 65% to 85%), and at a constant temperature and velocity. Desorption characteristics are tested under 328 K and 5% RH. The total moisture sorption of MENCDs with a TR of 0.365 is found to be 11.84 g/100 g, which is 17% higher compared to natural composite desiccants (i.e., TR = 1) at 85% RH, whereas, the total moisture sorption rate is 0.4 g/100 g⋅min, which is 20.57% higher for TR of 0.365 compared to TR = 1. Moisture desorption rate for TR = 0.365 is 16.66% higher compared to TR = 1. The average exergy efficiency of these systems is 60%. The average exergy efficiency of these composite desiccants with a TR = 0.365 is 9.6% higher compared to TR = 1. The average total heat load reduction for composite desiccants with a TR = 0.365 is 24% higher compared to TR = 1. The experimental study shows that the MENCDs will help to increase total heat load reduction, sorption and desorption rate, and total moisture sorption of dehumidified air with optimum thickness ratio for enhanced utilization of a composite desiccant for dehumidification systems.

Effects of casing cooling slot purge on heat transfer in turbine blade tip and casing

In recent years, heat transfer in turbine tips and casings has received extensive attention. To further improve heat transfer in the casing region, casing cooling slot purge is proposed as a strategy to effectively control the high heat load. In this study, the effects of different cooling groove geometries and aerodynamic parameters on the heat transfer coefficient and net heat load reduction of the blade tip and casing cooling efficiency are compared numerically when the outlet isentropic Ma is 0.96. The results show that the casing cooling slot purge can realize cooling of the casing, tip groove surface, and tip area of the suction surface. A better cooling effect could be obtained by reducing the coolant slot angle at the same flow rate. By increasing the coolant injection angle, the cooling efficiency of the casing and the inner surface of the groove is improved.

Prospects for Creating a New Generation of Ice banks for Systems with Uneven Heat Loads

BACKGROUND: The rational application of thermal energy storages with phase transition for objects of the food industry with significantly uneven heat loads is discussed in this article. The drawbacks of existing ice banks, suppressing their spread, are analyzed. Possible methods of addressing these problems during the designing process are considered.&#x0D; AIM: Development of a new generation of ice banks with a high intensity of ice melting processes and the ability to adjust the heat load.&#x0D; MATERIALS AND METHODS: The brand-new discharge method based on the film flow around ice surfaces is proposed. The proposed approach allows us to optimize the heat load and provide the maintenance of the required ice water temperature. The laboratory sample of the coaxial film heat exchanger (FHE) was designed by the authors.&#x0D; RESULTS: Experimental results in the operating range of the levels of supplied water temperatures 20 ℃, 40 ℃, and 60 ℃ and mass flow rates 15, 30, 45, and 60 kg/min are carried out. The experimental results confirmed that the development construction of the FHE with the film mechanism of the heat transfer provides increasing efficiency in orders of magnitude in comparison with ice banks with bulk melting. The reduced heat load with a mass flow rate of 60 kg/min and medium temperature on 60 ℃ was 220240 kW/m2, and the maximal reduced heat load of the upper layer of coil reached 1300 kW/m2. The generalization of the results showed the application prospects of film ice banks in the refrigeration systems of various industrial and agricultural objects.

Study on hypersonic drag and heat reduction of a spiked blunt body with multiple flat aerodisks and rear opposing jets

The performance of a proposed drag and heat reduction scheme that combines multiple flat aerodisks and the rear opposing jet is numerically investigated using compressible Reynolds Averaged Navier-Stokes (RANS) equations coupled with the shear stress transport (SST) turbulence model. Results show that the introduction of the multiple flat aerodisks and the rear opposing jet push the reattachment shock wave away from the blunt body and reduce the intensity of reattachment shock wave as well. Compared with the configuration with only a spike and a conical aerodisk, the present configuration shows a reduction in peak pressure and peak heat flux of the blunt body surface by 70.21% and 84.84%, respectively. Furthermore, the impact of configuration parameters (i.e., jet pressure ratio, spike length, aerodisks diameter, number, and position) on the flow field, drag and heat reduction performance are also investigated. The results reveal that increasing the jet pressure ratio can enhance the performance of drag and heat reduction. Increasing the length of the spike can get a better drag reduction performance. Increasing the diameter of flat aerodisk Ⅲ significantly enhances the compression of hypersonic free stream to reduce the intensity of reattachment shock wave. The configuration with four flat aerodisks has better drag and heat reduction performance. Compared with the baseline configuration, the maximum reduction of peak pressure and peak heat load of the blunt body surface can be achieved by moving the flat aerodisk Ⅱ forward.

Behavioural responses of a large, heat-sensitive mammal to climatic variation at multiple spatial scales.

Climate warming creates energetic challenges for endothermic species by increasing metabolic and hydric costs of thermoregulation. Although endotherms can invoke an array of behavioural and physiological strategies for maintaining homeostasis, the relative effectiveness of those strategies in a climate that is becoming both warmer and drier is not well understood. In accordance with the heat dissipation limit theory which suggests that allocation of energy to growth and reproduction by endotherms is constrained by the ability to dissipate heat, we expected that patterns of habitat use by large, heat-sensitive mammals across multiple scales are critical for behavioural thermoregulation during periods of potential heat stress and that they must invest a large portion of time to maintain heat balance. To test our predictions, we evaluated mechanisms underpinning the effectiveness of bed sites for ameliorating daytime heat loads and potential heat stress across the landscape while accounting for other factors known to affect behaviour. We integrated detailed data on microclimate and animal attributes of moose Alces alces, into a biophysical model to quantify costs of thermoregulation at fine and coarse spatial scales. During summer, moose spent an average of 67.8% of daylight hours bedded, and selected bed sites and home ranges that reduced risk of experiencing heat stress. For most of the day, shade could effectively mitigate the risk of experiencing heat stress up to 10°C, but at warmer temperatures (up to 20°C) wet soil was necessary to maintain homeostasis via conductive heat loss. Consistent selection across spatial scales for locations that reduced heat load underscores the importance of the thermal environment as a driver of behaviour in this heat-sensitive mammal. Moose in North America have long been characterized as riparian-obligate species because of their dependence on woody plant species for food. Nevertheless, the importance of dissipating endogenous heat loads conductively through wet soil suggests riparian habitats also are critical thermal refuges for moose. Such refuges may be especially important in the face of a warming climate in which both high environmental temperatures and drier conditions will likely exacerbate limits to heat dissipation, especially for large, heat-sensitive animals.

AEROTHERMODYNAMICS OF COMBINED SPIKE AND COUNTERFLOW JET TECHNIQUE FOR REACTING HYPERSONIC FLOWS

Computational investigation is carried out to estimate the drag force and surface heating load for hypersonic reacting flows. An in-house viscous nonequilibrium finite volume-based reacting gas solver has been utilized. This solver is capable of investigating 11 chemical elementary reactions and temperature-dependent specific properties to reveal the effect of lower as well as higher freestream stagnation enthalpy conditions. Initially, the calorically perfect-gas and real-gas model-based simulations are carried out to understand the real-gas effects in the presence of a metallic spike. Computed surface pressure and heat flux are compared for the freestream stagnation enthalpy of 2 MJ/kg. The real-gas model predicts a 5&amp;#37; higher drag and 57.21 kW/m&lt;sup&gt;2&lt;/sup&gt; higher peak heat flux compared to the perfect-gas model. However, lower enthalpy conditions predict almost the same drag force for any spike length. Further, a counterflowing jet is installed at the root of the spike, and flow field alterations are studied for this proposed integrated configuration. The root jet further pushes the conical shock in the upstream direction and provides an extra-large recirculation zone. Here, the possibility of drag and surface heat flux reduction is very much evident due to the decrease in surface pressure and presence of low-temperature jet gas in the vicinity of the object. Various freestream stagnation enthalpies, as well as the jet pressures, are considered to investigate the performance alterations by the combination technique. It is observed that the drag and surface heat load reduction efficiency of the combined configuration decreases with an increase in the freestream stagnation enthalpy. Moreover, it increases when increasing the root jet pressure for given enthalpy conditions. Hence, instead of attaching a long spike at the stagnation region of a blunt-shaped object, the use of a short spike and low-pressure root jet is recommended for a better reduction in drag and surface heat load.

Parameter study of L–H transition for plasma operation scenario development in JA DEMO

We have investigated the L–H transition in JA DEMO, a design concept of the steady-state tokamak fusion demonstration reactor. We develop an L–H transition model, which determines the minimum pedestal growth time such that a power ratio, the net plasma loss power across the separatrix over the L–H threshold power, is maintained at a constant value during pedestal growth for a given external heating power. We conduct parameter studies using an integrated modeling code, considering impurity transport. The dependence of the heating power and time required for the L–H transition on the plasma density, temperature, threshold power, impurity density fraction, and impurity transport coefficients is clarified. We evaluate the appropriate impurity density fraction for the L–H transition and the divertor heat load reduction. The fraction depends on the impurity transport coefficients and external heating power. The obtained results are necessary to confirm the L–H transition feasibility and to develop the plasma operation scenario consistent with the various engineering constraints in a design-stage reactor. The heating power required for the L–H transition turns out to be lower than the power supposed to be installable in the current design activities of JA DEMO.