Thermal Constraints Research Articles

Rising seawater temperatures affect the fitness of Rhopilema nomadica polyps and podocysts and the expansion of this medusa into the western Mediterranean

Since first reported in the eastern Mediterranean in the 1970s, the swarm-forming scyphomedusa, Rhopilema nomadica, has been continuously expanding westward. We examined the effect of temperature on the benthic stages of this jellyfish (polyps, podocysts, and strobilae) to assess whether it can survive and reproduce in the western Mediterranean temperature regime (12.2-26.2°C). In the first experiment, polyps and podocysts were maintained at 4 constant temperatures (12, 18, 24, and 30°C) for 55 d. In the second experiment, temperatures were gradually reduced over 14 d, kept constant for 18 d, and then gradually brought back to 25°C. High temperatures proved beneficial to polyp survival and asexual reproduction, yet in some cases, polyps were able to survive temperatures as low as 12°C. Strobilation occurred at temperatures between 22 and 30°C. Podocyst production, excystment, and strobilation all take place following a temperature increase, and excystment of podocysts occurs mainly during the first 2 wk following podocyst production. We propose that the role of podocysts in R. nomadica is mainly to increase the current season’s polyp population, contributing to swarm formation rather than as a means to maintain polyp populations during harsh environmental conditions. Since polyps are able to survive winter temperatures in the western basin (12°C) and reproduce by podocysts and strobilation during summer temperatures (24°C), thermal constraints will probably not restrict the expansion of R. nomadica into the western Mediterranean. Expected future climate change conditions will increase the performance and range expansion of this species.

Customized Optical Fiber Birefringent Sensors to Multipoint and Simultaneous Temperature and Radial Strain Tracking of Lithium‐Ion Batteries

AbstractBatteries are seen as a vital piece for actual carbon‐neutral world needs. However, as they basically operate through extremely exothermic electrochemical events, special attention must be paid to their thermal and volumetric constraints, where continuous and accurate monitoring is of great importance. Considering it, customized optical sensors, based on fiber Bragg gratings recorded in birefringent PANDA fibers (FBG‐PANDA), are developed and instrumented in a coiled configuration into a cylindrical Li‐ion battery (LiB) to simultaneously track temperature and radial strain during galvanostatic cycles, in three different battery locations, for the first time. The maximum temperature and radial strain variations are achieved in the middle and at the end of the discharge steps. This thermal behavior is correlated with the internal heat generation and transfer of thermal energy processes, with a tendency to accumulate in the LiB central zone.Good feasibility and reproducibility are observed in the optical sensor's performance and demonstrated that by operating as a multiparameter decouple system, they can decrease the complexity and intrusiveness in batteries, by using only one optical fiber line. The reported results are in accordance with the literature, indicating that such sensors could be consistently used for future applications regarding battery safety parameters sensing.

Multi-zone building control with thermal comfort constraints under disjunctive uncertainty using data-driven robust model predictive control

Multi-zone building control with thermal comfort constraints under disjunctive uncertainty using data-driven robust model predictive control

Coordinated preparation and recovery of a post-disaster Multi-energy distribution system considering thermal inertia and diverse uncertainties

Low-probability but high-impact extreme events, such as floods, earthquakes, hurricanes, etc., could threaten the security of a multi-energy system, especially on the distribution level, and cause severe energy supply outages. In this paper, a coordinated restoration method is presented for the renewable energy-integrated multi-energy distribution system (MDS) with several coupling points to coordinate the preparation and load recovery stages after the extreme event. First, the MDS restoration is comprehensively modeled with coupled power and thermal network constraints. Especially, the thermal inertia, which is in the form of pipe storage and thermal demand response of smart buildings to serve as a buffer when the source fails, is fully utilized to reduce the energy supply cost after disasters. Secondly, both preparation and load recovery stage measures are employed to facilitate efficient and reliable system restoration. Furthermore, multiple uncertainties from the renewable generation and power demands in the MDS restoration are dealt with via a risk-averse two-stage stochastic programming approach. Finally, simulation results validate the effectiveness of our method and its superiority over the traditional restoration methods.

A New Low Switching Frequency Control of Regenerative CHB Drive With Low-Voltage Ride-Through Capability

In conventional medium-voltage high-power cascaded H-bridge (CHB) drive, a three-phase rectifier is adopted in each power cell to provide isolated dc-bus voltage for the output H-bridge. This limits the application of the conventional CHB drive, where regeneration capability is desired. The regenerative CHB drive can be made possible by replacing the diode rectifier with a three-phase IGBT-based active-front-end (AFE) rectifier in each power cell. However, due to thermal constraints in the high-power medium-voltage drives, the first challenge of the regenerative CHB drive is to deal with the extra switching losses introduced by the IGBT devices. Another challenge of the grid-tied regenerative CHB drive is to handle the low-voltage sags in the power grid without triggering unnecessary downtime in transients. In this article, a novel low-switching frequency control strategy is proposed for the AFEs in the regenerative CHB drive with low-voltage ride-through (LVRT) capability. The main harmonic contents generated by the AFEs with the proposed control strategy can be eliminated by the existing phase-shifting transformer in the CHB drives. This allows meeting with IEEE STD 519-2014 requirement with a 60 Hz switching frequency to minimize the extra introduced switching losses in steady state. Moreover, LVRT capability is integrated into the proposed control scheme with reduced current sensor count. Accompanied with videos, the experiments on a seven-level regenerative CHB drive are implemented to validate the feasibility of the proposed control scheme, which can be extended to regenerative CHB drives with any voltage levels.

Effect of the secondary microcontact state induced by the all-factor thermal effect on bidirectional thermal contact performance

Contact interfaces are widespread in electronic systems, and the heat dissipation problem caused by the thermal contact resistance (TCR) has seriously affected the overall performance. Previous studies often disregarded the effect of the secondary microcontact state induced by thermal effects such as thermal stress and thermal softening on thermal contact performance, such as TCR, contact interface temperature distribution nonuniformity (CITDN), and the thermal rectification effect. Therefore, this paper proposes a thermomechanical coupled numerical model that considers the secondary microcontact state induced by all-factor thermal effects, and the effect of the thermal effect on bidirectional thermal contact performance under different temperatures, thermal expansion coefficients and constraints is revealed. Furthermore, a method to control the thermal rectification coefficient by controlling the contact gap was proposed. The results show that the influence of thermal effects on TCR and CITDN at high temperatures, with high thermal expansion coefficients and under strong constraint conditions cannot be disregarded and that the influence of temperature and thermal expansion coefficient on the strong constraint side is greater than that on the weak constraint side. The thermal rectification effect is effectively enhanced by adjusting the initial contact gap determined by the thermal expansion coefficient, elastic modulus and temperature.

Local Energy Market-Consumer Digital Twin Coordination for Optimal Energy Price Discovery under Thermal Comfort Constraints

The upward trend of adopting Distributed Energy Resources (DER) reshapes the energy landscape and supports the transition towards a sustainable, carbon-free electricity system. The integration of Internet of Things (IoT) in Demand Response (DR) enables the transformation of energy flexibility, originated by electricity consumers/prosumers, into a valuable DER asset, thus placing them at the center of the electricity market. In this paper, it is shown how Local Energy Markets (LEM) act as a catalyst by providing a digital platform where the prosumers’ energy needs and offerings can be efficiently settled locally while minimizing the grid interaction. This paper showcases that the IoT technology, which enables control and coordination of numerous devices, further unleashes the flexibility potential of the distribution grid, offered as an energy service both to the LEM participants as well as the external grid. This is achieved by orchestrating the IoT devices through a Consumer Digital Twin (CDT), which facilitates the optimal adjustment of this flexibility according to the consumers’ thermal comfort level constraints and preferences. An integrated LEM-CDT platform is introduced, which comprises an optimal energy scheduler, accounts for the Renewable Energy System (RES) uncertainty, errors in load forecasting, Day-Ahead Market (DAM) feed in/out the tariff, and a fair price settling mechanism while considering user preferences. The results prove that IoT-enabled consumers’ participation in the energy markets through LEM is flexible, cost-efficient, and adaptive to the consumers’ comfort level while promoting both energy transition goals and social welfare. In particular, the paper showcases that the proposed algorithm increases the profits of LEM participants, lowers the corresponding operating costs, addresses efficiently the stochasticity of both energy demand and generation, and requires minimal computational resources.

Fault Gouge Dating in the Spanish Pyrenees: Fault Ages, Thrust Propagation Sequence, Wall‐Rock Provenance, and Thermal Constraints

AbstractDating brittle faults by the growth of authigenic illite in fault gouge allows for direct testing of kinematic models of orogenic evolution, such as in‐sequence versus out‐of‐sequence thrusting, and the presence of orogenic “pulses” of deformation on multiple thrusts simultaneously. We present illite gouge ages from five thrust faults along the Ter and Freser rivers in the south‐eastern Pyrenees fold‐and‐thrust belt dated by Ar‐Ar methods. The ages show in‐sequence thrusting for the south‐eastern Pyrenees fold‐thrust belt during the Eocene and early Oligocene, ranging from 49.5 + 4.4 Ma for the inboard Freser Antiformal Stack to 31.9 ± 3.9 Ma for the frontal L’Escala Thrust. Foreland progression of ages is preserved, although overlapping of ages of the frontal thrusts permits the interpretation of a period of more rapid fault displacement around 35 Ma. Shortening rates for the Ter‐Freser section range from 1.2–2.7 km/my, with strain rates ranging from 7.0 × 10−16 s−1 to 1.6 × 10−15 s−1 The latest Paleozoic ages of the cataclastically derived component inferred from the gouge dating methodology are shown to be pooled 2M1 illite/mica ages of wall rock sediments and have geological meaning. These inferred mica ages of the thrust wallrocks in the southeastern Pyrenees indicate Hercynian‐age micas were deposited in the Southern Pyrenean foreland basin as early as the late Cretaceous. Previous thermochronometer and Δ47 temperatures from syn‐faulting calcite veins constrain temperature of clay gouge formation in the Ter‐Freser section at 50–210°C, with most likely temperatures of 50–160°C, consistent with previous studies.

Computing marine plankton connectivity under thermal constraints

Ocean currents are a key driver of plankton dispersal across the oceanic basins. However, species specific temperature constraints may limit the plankton dispersal. We propose a methodology to estimate the connectivity pathways and timescales for plankton species with given constraints on temperature tolerances, by combining Lagrangian modeling with network theory. We demonstrate application of two types of temperature constraints: thermal niche and adaptation potential and compare it to the surface water connectivity between sample stations in the Atlantic Ocean. We find that non-constrained passive particles representative of a plankton species can connect all the stations within three years at the surface with pathways mostly along the major ocean currents. However, under thermal constraints, only a subset of stations can establish connectivity. Connectivity time increases marginally under these constraints, suggesting that plankton can keep within their favorable thermal conditions by advecting via slightly longer paths. Effect of advection depth on connectivity is observed to be sensitive to the width of the thermal constraints, along with decreasing flow speeds with depth and possible changes in pathways.

Inspecting heat transport phenomenon in the flow of non-Newtonian fluid in the presence of Newtonian heating and inclined slip: fractional derivative framework

A fractional model is considered to the present thermodynamic aspect of heat and fluid flow of second-grade fluid with a porous medium. The mixed convection features and inclined directional magnetic force are also enrolled. The convective thermal constraints are utilized for assessing the heat transfer properties. The erect vertical with the porous medium induced the flow. Two fractional approaches, Caputo-Fabrizio (CF) and Caputo-time algorithms, are utilized for the computation of analytical tasks. The integration is facilitated with the Laplace technique. Stehfest and Tzou’s techniques are used for evaluating the Laplace inverse transformation. The physical parameters’ contribution to altering the velocity and temperature profile is justified. It is noted that velocity and temperature profiles decrease for the non-singular parameters. More decrement in velocity and temperature profiles is associated with the Caputo-time model.

THERMAL RADIATION IMPACT AND CATTANEO-CHRISTOV THEORY FOR UNSTEADY FLOW OF MAXWELL FLUID OVER STRETCHED CYLINDER WITH INCONSISTENT HEAT SOURCE/SINK

Examination of thermal and solutal energy with sophisticated guesstimate of thermal radiation bearing. Conveyance portents in Maxwell fluid pour thru the gain of Cattaneo-Christov double diffusion theory is fulfilled in this artefact. Unsteady 2D flow of Maxwell fluid with variable thermal conductivity over the stretching cylinder with thermal emission and heat source/sink is deliberated here. We verbalize the partial differential equations (PDEs) under particular molds for the governing physical tricky of heat and mass transportation in Maxwell fluid by using double diffusion of Cattaneo-Christov model rather than classical Fourier's and Fick's law. Numerical technique $4^{\text {th }}$ order Runge-Kutta method is employed for the solution of ordinary differential reckonings (ODEs) which are obtained from governing PDEs under the apt resemblance transformations. In the interpretation of acquired fallouts, we beheld that for fitting upshots the tenets of unsteadiness constraint should be less than one. The higher tenets of Maxwell parameter deteriorations the flow field but increase the energy transport in the fluid flow. Both temperature and attentiveness scatterings in Maxwell liquid deterioration for sophisticated tenets of thermal and attentiveness relaxation time constraint. Alike, trifling thermal conductivity constraint also augments the temperature field. Auxiliary, the rate of heat transfer deteriorations.

Self-support topology optimization considering distortion for metal additive manufacturing

This paper proposes a self-support topology optimization method that considers distortion to improve the manufacturability of additive manufacturing. First, a self-support constraint is proposed that combines an overhang angle constraint with an adjustable degree of the downward convex shapes and a thermal constraint for heat dissipation in the building process. Next, we introduce a mechanical model based on the inherent strain method in the building process and propose a constraint that can suppress distortion. An optimization problem is formulated to satisfy all constraints, and an optimization algorithm based on level-set-based topology optimization is constructed. Finally, two- and three-dimensional optimization examples are presented to validate the effectiveness of the proposed topology optimization method.

Feasible operation region of an electricity distribution network

In the course of net zero carbon transition, electricity distribution networks are faced with great challenges brought by increasing total and peak demand due to the electrification of transport and heat, as well as the significant uncertainties from renewable power generation and customer behaviors (such as electric vehicle travelling behaviors). Therefore, distribution network operators (DNOs) need effective tools to assess the capability of distribution networks in integrating generation and demand to conduct active management and efficient expansion of networks. However, conventional scenario-based assessment methods only provide conservative and limited information on the network capability, also with exponentially increased computational burden. By contrast, another stream of methods with different philosophy, named as operation region-based methods, describe the overall picture of the network capability analytically with little computational power needed. However, the existing linearized analytical regions, which are mainly applied to electricity transmission networks, cannot describe the capability of distribution networks accurately enough. To solve these problems, a novel feasible operation region (FOR) method with quadratic analytical expressions was proposed to characterize the range of the operating states of distribution networks, where the thermal and voltage constraints will not be violated. The FOR is a geometry in a high-dimensional space, and thus a high-dimensional error analysis approach was further developed for validating the proposed method. The boundary errors are described by multiple distance functions and operational indices, and the conservativeness of the analytical boundaries are quantified. An 11 kV radial distribution network from the United Kingdom Generic Distribution System (UKGDS) was used for the case study. The simulation results show that the quadratic analytical boundaries well approximated the real boundaries of FOR. The maximum errors for thermal and voltage boundaries would maximally cause an overcurrent up to 116 % and an undervoltage down to 0.96p.u., which are able to satisfy the requirements of engineering practice. Compared to the existing linear approximation (termed as hyperplane expressions) of FOR boundaries, the proposed quadratic expressions were proved to have higher accuracy.

Bioconvective Homann flow of tangent hyperbolic nanofluid due to spiraling disk with convective and zero mas flux constraints

The phenomenon of bioconvection in nanomaterials presents novel applications in the biotechnology, biofuels, enzymes, biomedical engineering and energy systems. Current exploration explores the applications of bioconvection in Homann flow of nanofluid due to spiraling of disk theoretically. The generalized model namely tangent hyperbolic fluid is used to predicts the rheological and thermal impact. The stability of nanofluid is ensured with interaction of motile microorganisms. The Boungrino nanofluid model with thermophoresis and Brownian motion features is used to perform the analysis The thermal distribution of nanofluids is proceeded by utilizing the zero mass thermal constraints. The similarity variables are introduced in order to estimating the dimensionless formulation. The Keller Box method with higher efficiency is imposed with implicit finite difference numerical algorithm. The main observations reveal that with enhancing the radial velocity and azimuthal velocity decreases with increasing sparling angle. For highly viscous case, a decrement in the azimuthal velocity has been observed.

Overheating control in additive manufacturing using a 3D topology optimization method and experimental validation

Overheating is a major issue especially in metal Additive Manufacturing (AM) processes, leading to poor surface quality, lack of dimensional precision, inferior performance and/or build failures. A 3D density-based topology optimization (TO) method is presented which addresses the issue of local overheating during metal AM. This is achieved by integrating a simplified AM thermal model and a thermal constraint within the optimization loop. The simplified model, recently presented in literature, offers significant computational gains while preserving the ability of overheating detection. The novel thermal constraint ensures that the overheating risk of optimized designs is reduced. This is fundamentally different from commonly used geometry-based TO methods which impose a geometric constraint on overhangs. Instead, the proposed approach takes the process physics into account. The proposed method is validated via an experimental comparative study. Optical tomography (OT) is used for in-situ monitoring of process conditions during fabrication and obtained data is used for evaluation of overheating tendencies. The novel TO method is compared with two other methods: standard TO and TO with geometric overhang control. The experimental data reveals that the novel physics-based TO design experienced less overheating during the build as compared to the two classical designs. A study further investigated the correlation between overheating observed by high OT values and the defect of porosity. It shows that overheated regions indeed show higher defect of porosity. This suggests that geometry-based guidelines, although enhance printability, may not be sufficient for eliminating overheating issues and related defects. Instead, the proposed physics-based method is able to deliver efficient designs with reduced risk of overheating.

Optimal Design of the Flexure Mount for Optical Mirror Using Topology Optimization Considering Thermal Stress Constraint

An optical mirror assembly is an opto-mechanically coupled system as the optical and mechanical behaviors interact. In the assembly, a flexure mount attached to an optical mirror should be flexible in the radial direction, but rigid for the remaining degrees of freedom for supporting the mirror rigidly and suppressing the wavefront error of the optical mirror. This work presents an optimal design of the flexure mount using topology optimization with thermal stress constraint. By simplifying the optical mirror assembly into finite shell elements, topology optimization model was built for efficient design and good machinability. The stress at the boundary between the optical mirror and the mount together with the first natural frequency were applied as constraints for the optimization problem, while the objective function was set to minimize the strain energy. As a result, we obtained the optimal design of the flexure mount yielding the improved wavefront error, proper rigidity, and machinability.

Permeability and Groundwater Flow Dynamics in Deep‐Reaching Orogenic Faults Estimated From Regional‐Scale Hydraulic Simulations

AbstractNumerical modeling is used to understand the regional scale flow dynamics of the fault‐hosted orogenic geothermal system at the Grimsel Mountain Pass in the Swiss Alps. The model is calibrated against observations from thermal springs discharging in a tunnel some 250 m underneath Grimsel Pass to derive estimates for the bulk permeability of the fault. Simulations confirm that without the fault as a hydraulic conductor the thermal springs would not exist. Regional topography alone drives meteoric water in a single pass through the fault plane where it penetrates to depths exceeding 10 km and acquires temperatures in excess of 250°C. Thermal constraints from the thermal springs at Grimsel Pass suggest bulk fault permeabilities in the range of 2e−15 m2–4.8e−15 m2. Reported residence times of >30,000 and 7 years for the deep geothermal and shallow groundwater components in the thermal spring water, respectively, suggest fault permeabilities of around 2.5e−15 m2. We show that the long residence time of the deep geothermal water is likely a consequence of low recharge rates during the last glaciation event in the Swiss Alps, which started some 30,000 years ago. Deep groundwater discharging at Grimsel Pass today thus infiltrated the Grimsel fault prior to the last glaciation event. The range of permeabilities estimated from observational constraints is fully consistent with a subcritical single‐pass flow system in the fault plane.

Experimental Assessment of Cryogenic Cooling Impact on Induction Motors

In this work, an experimental assessment of the influence of cryogenic cooling in a conventional induction motor is presented. The performance of a fractional kilowatt induction motor is evaluated when submerged in liquid nitrogen. Using the single-phase equivalent electric circuit, the influence of the temperature and skin-effect is analyzed in the variation of the machine's parameters, under ambient and cryogenic conditions. Also, the variation of the iron core and mechanical losses are evaluated. An analytical methodology is proposed to estimate the change of motor performance under cryogenic conditions. For the analyzed induction motor, measurements are performed to verify the predicted machine performance. The experimental tests in cryogenic conditions show the possibility of achieving higher efficiency levels with more than double the nominal torque. Also, due to the cryogenic environment, there was no thermal constraint in the operation of the induction motor.

Desensitized Optimal Control of Electric Aircraft Subject to Electrical–Thermal Constraints

This article proposes a desensitized optimal control (DOC) methodology to enhance the trajectory robustness of electric aircraft. First, a comprehensive multiphysics model of electric aircraft is built based on the first principle. An emphasis is put on the battery pack characteristics led by the cell unevenness. Thereafter, the optimal control technique is applied to study the influence of thermal effects and battery unevenness on flight performance. Furthermore, to alleviate the impact of cell unevenness, the crude control scheme is augmented by DOC. The proposed method generates a more robust reference trajectory for aircraft against cell unevenness. Processor-in-the-loop tests prove that the trajectory is trackable via a tracking controller. Compared to the standard trajectory optimization and nonlinear model predictive control, the proposed method significantly reduces the sensitivity of battery pack temperature regarding cell unevenness with acceptable computational effort.

QuadStream

Streaming rendered 3D content over a network to a thin client device, such as a phone or a VR/AR headset, brings high-fidelity graphics to platforms where it would not normally possible due to thermal, power, or cost constraints. Streamed 3D content must be transmitted with a representation that is both robust to latency and potential network dropouts. Transmitting a video stream and reprojecting to correct for changing viewpoints fails in the presence of disocclusion events; streaming scene geometry and performing high-quality rendering on the client is not possible on limited-power mobile GPUs. To balance the competing goals of disocclusion robustness and minimal client workload, we introduce QuadStream , a new streaming content representation that reduces motion-to-photon latency by allowing clients to efficiently render novel views without artifacts caused by disocclusion events. Motivated by traditional macroblock approaches to video codec design, we decompose the scene seen from positions in a view cell into a series of quad proxies , or view-aligned quads from multiple views. By operating on a rasterized G-Buffer, our approach is independent of the representation used for the scene itself; the resulting QuadStream is an approximate geometric representation of the scene that can be reconstructed by a thin client to render both the current view and nearby adjacent views. Our technical contributions are an efficient parallel quad generation, merging, and packing strategy for proxy views covering potential client movement in a scene; a packing and encoding strategy that allows masked quads with depth information to be transmitted as a frame-coherent stream; and an efficient rendering approach for rendering our QuadStream representation into entirely novel views on thin clients. We show that our approach achieves superior quality compared both to video data streaming methods, and to geometry-based streaming.