Search Results (659)

A single-tank molten-salt heat-exchanger storage system is promising for small-scale industrial heat supply, yet transient natural convection and heat transfer in closed tanks remain insufficiently understood. This study develops a physical model and performs numerical simulations of a top-heated single-tank sensible thermal storage unit using a realistic post-discharge, non-uniform initial temperature field. During charging, an upward plume forms near the heating rod, with heat concentrated around the rod and weak flow in remote regions. Two large-scale circulation cells separated by an inclined thermocline are observed, and the interface shifts downward over time. To address short storage duration, a segmented-heating strategy is proposed by varying the heating-section height. Results show that heater height strongly governs flow and storage performance: compared with full-length heating, 2/3-, 1/2-, and 1/3-length configurations extend storage duration by 93%, 100%, and 103.9%, respectively. Lowering the heating zone toward the tank bottom effectively prolongs storage and improves thermal efficiency. Full article

This paper presents the results from in-lab chassis dynamometer testing of two battery electric vehicles of the same make and model: a 2022 model year vehicle with a heat pump and a 2020 model year vehicle with a resistive positive temperature coefficient (PTC)-type heater. The vehicles were tested over a series of standard drive cycles at −10 °C, −7 °C, 0 °C, and 25 °C to determine the impacts of the different heating systems on vehicle energy consumption and driving range in cold temperatures. The results indicate that in most (but not all) heating situations the heat pump heated its vehicle’s cabin more efficiently than the PTC heater did, especially at 0 °C. At the lowest temperature, −10 °C, the heat pump used more energy than the PTC heater on cold-start but was more efficient than the PTC heater once the cabin was warmed up. Over standard drive cycles and using SAE J1634 calculation methods to obtain a single range value for each cycle type, the improvement in the percentage of driving range retained by the heat pump-equipped vehicle over the PTC heater-equipped vehicle varied between 1% and 15% depending on ambient conditions and drive cycle, with the average advantage in percentage range retained being 7% over the UDDS cycle, 7% over the HWFET cycle, and 4% over the US06 cycle for all cold temperatures combined. Full article

Electric vehicles (EVs) experience substantially reduced driving range in cold weather, primarily due to cabin heating energy demands. This paper proposes a control allocation strategy for positive temperature coefficient (PTC) heater-based electric minibus cabin thermal management, aimed at minimizing energy consumption. The strategy is of a hierarchical structure, where a supervisory PI cabin temperature controller commands the heating power demand, which is then achieved through optimal allocation and low-level control of the cabin inlet air temperature, coolant pump flow, and radiator blower air flow control inputs. Based on the assumption of fast heating system dynamics relative to cabin thermal dynamics, quasi-steady-state optimization of control input allocation is carried out by employing a grid-search algorithm over a dataset resulting from high-fidelity simulations. For the system heat-up transient conditions, where the steady-state allocation proves to be suboptimal, dynamic programming is applied on a validated reduced-order model to optimize the control trajectories. Insights gained through control trajectory optimization are then used to develop a rule-based modification of the control allocation strategy for the heat-up scenario. Simulation verification of the overall control system demonstrates energy consumption reduction in the range from 4 to 12% when compared to the industrial baseline system across both steady-state and transient operating conditions. Full article

Transparent heaters intended for skin-contacting applications must simultaneously satisfy optical transparency, mechanical compliance, thermal uniformity, and operational safety under biologically relevant temperature ranges. Here, we evaluate the applicability of a TiO₂/Ag/SiO₂ (TAS) dielectric–metal–dielectric transparent heater as a functional biomaterial platform for wearable and skin-integrated thermal systems. By systematically optimizing each layer thickness of the TAS structure, the heater achieves high visible-light transmittance (average of 86.6%) together with low sheet resistance on the order of 7.7 Ω/sq for low-voltage operation. The TAS heater demonstrates rapid and reproducible Joule-heating behavior, showing fast thermal response with short thermal time constants and spatially homogeneous temperature distributions without localized hot spots. Stable electrothermal performance is maintained under repeated on/off cycling and during cyclic mechanical bending down to small radii, confirming excellent mechanical stability under repeated bending relevant to wearable applications. Importantly, direct on-skin evaluations conducted by attaching the device to a human elbow reveal conformal contact, uniform heating at therapeutically relevant temperatures (50–70 °C), and stable operation under dynamic bending and extension. The absence of thermal inhomogeneity during motion highlights the intrinsic stability of the TAS architecture for skin-interfaced use. Given the high optical visibility, mechanical compliance, thermal uniformity, and electrothermal stability, the proposed TAS architecture represents a promising functional biomaterial platform for wearable thermotherapy, skin-mounted healthcare devices, and human-interactive thermal systems operating under continuous mechanical deformation and direct skin contact. Full article

This paper presents a thermodynamic modelling and performance analysis of a 217 MW coal-fired steam power plant, based on operating data from the only currently active coal-fired unit in Croatia. The study provides a concise technical description of the plant and a detailed thermodynamic analysis of energy flows across all major components of the steam cycle. The analysis was carried out using two complementary approaches: analytical calculations based on standard thermodynamic balance equations and numerical simulations performed with the commercial software Ebsilon Professional Version 17.00. The results obtained by both methods were validated against data reported in the literature and showed deviations within acceptable limits. Using the validated model, the influence of the number of regenerative feedwater heaters on overall plant efficiency was analysed. Additionally, sensitivity analyses were conducted to evaluate the influence of selected parameters, including the fuel net calorific value (NCV), the terminal temperature difference (TTD) of feedwater heaters, and pressure drops within the regenerative system. The results show that increasing the TTD from 2 K to 8 K reduces the net thermal efficiency from approximately 37.01% to 36.79%, while variations in pressure drop have a negligible effect on plant performance. Finally, a CO₂ emission cost analysis was conducted for each configuration, and conclusions regarding efficiency improvement and emission reduction were drawn. It was found that removing any regenerative feedwater heat exchanger decreases the observed overall plant efficiency by approximately 0.55% on average and increases plant CO₂ emissions by approximately 0.025 Mt per year on average. Full article

Advanced high-temperature fluid reactors (ARs), such as sodium fast reactors (SFRs) and molten salt cooled reactors (MSCRs) utilize high-temperature fluids at ambient pressure. To melt the fluid during reactor startup and prevent fluid freezing during cooldown, the thermal–hydraulic systems of such ARs include heater zones consisting of specific heaters with controllers, temperature sensors, and thermal insulation. The failure of heater zones due to insulation material degradation or improper installation, resulting in parasitic heat losses, can lead to fluid freezing. The detection of faults using a heat-transfer model is difficult because of a lack of knowledge of the experimental details. Data-driven machine learning of heater zone temperature time series offers a viable alternative. In this study, we benchmarked the performance of recurrent neural networks (RNNs) in an analysis of heat-up transient temperature time series of heater zones installed on a liquid sodium vessel. The RNN models include long short-term memory (LSTM) and gated recurrent unit (GRU) networks, as well as their bi-directional variants, BiLSTM and BiGRU. Anomalous temperature points were designated using a percentile-based threshold applied to residual fluctuations in the detrended temperature time series. Additionally, the impact of the exponentially weighted moving average (EWMA) method on detection accuracy was examined. The RNN models’ performance was assessed using precision, recall, and F₁ score metrics. Results demonstrated that RNN models effectively detect anomalies in temperature time series with the best models for each heater zone achieving F₁ scores of over 93%. To explain the variations in RNN model performance across different heater zones, we used Kullback–Leibler (KL) divergence to quantify the relative entropy between training and testing data, and the Detrended Fluctuation Analysis (DFA) to assess long-range temporal correlations. For datasets with strong long-range correlations and minimal relative entropy between training and testing data, GRU is the best-performing model. When the data exhibits weaker long-term correlations and a significant relative entropy between training and testing distributions, BiGRU shows the best performance. For the data sets with intermediate values of both KL divergence and DFA, the best performance is obtained with LSTM and BiLSTM, respectively. Full article

This study investigates the deposition of silicon nitride (SiN) thin films for advanced semiconductor applications, with a specific focus on overcoming thermal challenges in plasma-enhanced atomic layer deposition (PE-ALD) at an elevated temperature of 550 °C. At such high temperatures, a critical obstacle is wafer warpage induced by thermal and mechanical stress, which increases localized thermal contact resistance and degrades film uniformity. To address this, a wafer chucking function was integrated into a monopolar electrostatic chuck (ESC) heater. The ESC secures the wafer to the heater surface, effectively mitigating warpage and ensuring a uniform temperature distribution. Chucking performance was verified by monitoring lift-up motor torque variations and plasma parameters, such as self-bias voltage (Vdc) and peak-to-peak voltage (Vpp), confirming the formation of stable electrostatic coupling. A comparative analysis was conducted between SiN films deposited with and without a chucking voltage of +1000 V. Statistical evaluation across repeated experimental runs (n = 3) confirmed that ESC chucking significantly enhanced spatial uniformity without altering the fundamental PE-ALD growth mechanism. Notably, the application of ESC chucking suppressed the localized temperature drop at the wafer periphery, reducing the in-wafer temperature gradient from 7~8 °C to 2~3 °C. This thermal stability resulted in improved thickness uniformity (variation < 1 Å) and an increase in film density from 2.83 to 2.94 g/cm³. Furthermore, the physical contact between the wafer and the heater effectively eliminated backside deposition to near-zero levels. Pattern evaluation revealed an exceptional step coverage of 99% in high-aspect-ratio (20:1) structures. These results suggest that ESC-assisted PE-ALD provides a robust and reproducible method for high-quality SiN deposition by minimizing thermally induced film variations. Full article

In research related to cognitive performance, temperature is often regarded as a core influencing factor and has received significant attention. However, as a key component of the building thermal environment, solar radiation and its mechanism of action on cognitive performance have rarely been studied. This paper conducts a laboratory study, using an infrared radiation heater to simulate the thermal effect of solar radiation, and explores the age-related differences between the elderly and the young in thermal comfort, electroencephalogram (EEG) activity, and cognitive ability under three radiation intensities (0 W, 500 W, and 1000 W). The results show that age has a relatively small impact on subjective thermal responses but a significant impact on mental state and cognitive performance. In the infrared radiation environment, the alertness (ALV score) of the elderly remains more stable, while young people show an increased sense of drowsiness. EEG analysis indicates that the frontal lobe logarithmic power of both groups of subjects is 4.55–6.79% higher than the average of other brain regions. High radiation (1000 W) inhibits the EEG activity of young people but triggers compensatory activation in the elderly, thus reducing age-related neural differences. Cognitive tests show that compared with the non-radiation condition, high infrared radiation (1000 W) significantly improves the cognitive levels of the elderly in terms of attention (CPT: +1.53%), response ability (DLT: +0.78%) and visual search ability (VST: +2.04%), while these abilities decline in young people (CPT: −2.78%, DLT: −1.21%, VST: −3.82%). The correlation analysis between EEG and cognitive tests identifies that the right frontal electrodes (F4, F8) and the occipital O1 may be potential candidate electrodes for evaluating the cognitive performance of the elderly and young people. This study provides crucial objective physiological evidence for clarifying the relationship between heat sources such as the thermal effect of solar radiation, which “acts directly on the human body”, and human thermal comfort and cognitive performance. Full article

Ice accretion along aircraft leading edges, particularly at stagnation line parting strips, remains difficult to remove using conventional electrothermal anti-icing systems. These systems require continuous high-power heating to maintain the stagnation region above the melting point, often exceeding 10–12 kW/m². This study introduces an Ice Cavitation Deicer (ICD) that removes ice through rapid, localized cavitation generated within a thin melt layer formed at the ice–surface interface. In the proposed approach, a short pulse of electric current melts a 1–10 µm interfacial layer and causes a cavitation impulse of approximately 1–10 MPa. This impulse ejects the stagnation-line ice in a direction normal to the surface, often against the external airflow, enabling the immediate aerodynamic removal of the remaining ice. Analytical modeling based on the energy conservation principle was used to determine the optimal foil geometry, thermal pulse parameters, thermal stress, and material selection. Experiments with various metallic foils and substrate materials validated the predicted ejection behavior. The impulses were sufficient to fracture and eject ice 1–10 mm thick. The observed ice fragment velocities varied from 1 m/s to 10 m/s. Compared with conventional thermal anti-icing, the ICD concept reduces power consumption by approximately two orders of magnitude while offering rapid and reliable leading-edge deicing. The low power requirements, rapid response, and compatibility with thin-foil heater architectures make ICD a promising technology for both conventional and electrified aircrafts, UAVs, rotorcrafts, and other platforms where power availability is limited. This manuscript presents the first theoretical and experimental research on the ICD method and is a concept-proof work. Further research and development are required before the ICD is ready to be tested in flight. Full article

This study proposes a novel redesign of a solar water heater prototype by integrating a stationary compound parabolic concentrator (CPC) internally within a standard collector housing. Unlike conventional flat-plate systems or external trough collectors, this design aims to enhance thermal efficiency while maintaining a compact footprint suitable for residential retrofitting in tropical climates. The system’s thermal performance was analyzed using a 3D finite element method (FEM) based on the convection-diffusion equation, with a specific focus on a 2 cm focal length configuration designed to fit spatial constraints. The simulation results indicated a maximum water temperature of 62.9 °C under concentrated solar flux, while the experimental prototype achieved a maximum temperature of 55.0 °C under corresponding field conditions. The comparative analysis reveals a temperature discrepancy of approximately 8 °C (12.5%), which is attributed to the simplified boundary conditions neglecting radiative losses in the model. Despite this deviation, the proposed parabolic design demonstrated a distinct thermal enhancement compared to the conventional baseline. These findings validate the technical feasibility of the compact internal concentrator, offering a low-cost, high-performance alternative for domestic water heating applications. Full article

High-precision thermal regulation in semiconductor process equipment is critical for product quality, yet it is challenged by actuator transport delays, limited actuator bandwidth due to hardware dynamics, and broadband inlet disturbances in temperature-controlled process fluids. This paper presents a systematic solution integrating architecture optimization with a physics-informed hybrid prediction model to enable effective feedforward compensation. Frequency-domain analysis justifies placing the temperature fluctuation attenuator (TFA) upstream of the heater to filter mid-to-high-frequency disturbances without compromising feedback stability. To address actuation delays, a Physics-CNN-LSTM predictor is developed using a residual learning strategy. This framework employs a mechanism model for baseline estimation and a deep learning network to correct persistent low-frequency residuals caused by unmodeled dynamics. Comparative experiments on industrial data demonstrate that the model achieves a Root Mean Square Error (RMSE) of $3.56\times {10}^{-5}$ K under low-to-mid-frequency inlet disturbances, reducing error by approximately 51.8% compared to a standard LSTM. The model also exhibits strong robustness against disturbance frequency shifts ($R^2>0.996$ on unseen data). Furthermore, closed-loop simulations confirm that the proposed feedforward compensation enhances temperature stability in high-precision thermal control. Full article

This study presents a comprehensive thermal analysis, design, and optimization framework for electrothermal heating systems integrated into composite wing structures. Thermal behavior is first investigated using finite volume simulations conducted with a commercial solver. An in-house thermal solver is then developed based on the governing heat transfer equations and a second-order finite difference discretization scheme. The in-house solver is validated against the commercial solver, showing a maximum deviation of less than 1%. The validated solver is subsequently coupled with a genetic algorithm to perform multi-objective optimization of the electrothermal heating system. A novel correlation for the convection heat transfer coefficient over airfoil surfaces is developed based on extensive turbulent flow simulations and a genetic algorithm. The developed correlation equation has significantly lower percent relative error (from 34% to 6%) compared to flat plate correlations. The developed convection coefficient is incorporated into the optimization process. Key design variables, including heat generation intensity, heater strip dimensions, and the thermal conductivity of composite and surface protection materials, are included in the optimization process. An original objective function is formulated to simultaneously minimize electrical power consumption, prevent ice formation on the external surface, and limit internal temperatures to safe operating ranges for composite materials. The optimized design is evaluated under both spatially varying and constant convection heat transfer coefficients to assess the impact of convection modeling assumptions. The proposed methodology provides a unified and extensible framework for the optimal design of electrothermal ice protection systems and can be readily extended to three-dimensional composite wing configurations. Full article

To address the issue of energy conservation of high-pressure heater systems in feedwater temperature elevating, this paper proposes an advanced control strategy based on a self-disturbance-compensating generalized predictive control (GPC) algorithm. Combined with the control of high-pressure heater water level, the feedwater temperature is controlled. Aiming at the high inertia and significant delay in high-pressure heater systems, a GPC algorithm is introduced to effectively compensate for system dynamic lag. Concurrently, to tackle multi-source and unmeasurable disturbances during high-pressure heater operation, an extended state observer is presented for their real-time observation and compensation. This significantly enhances the control system’s disturbance rejection capability, while maximizing the heat transfer efficiency of the high-pressure heater and reducing irreversible losses in the thermal system. Simulation experiment results demonstrate that the proposed method achieves superior stability and control performance compared to relevant control methods for feedwater temperature regulation, offering a solution to enhance the thermal economy of the power plant. Full article

Magnetron sputtering serves as a key method for fabricating functional thin films used in transparent film heaters. However, as heater designs become more intricate, achieving uniform film deposition on nonrectangular areas induces localized overheating owing to current density crowding, compromising long-term reliability of the device. To address this limitation, a simulation-assisted design and fabrication strategy is presented to realize a uniform temperature profile through the precise regulation of the sheet resistance distribution of the film. Initially, an electrothermal-coupled finite element model was established using COMSOL Multiphysics to inversely determine the spatial gradient of sheet resistance required for achieving a uniform thermal distribution. Subsequently, a custom-designed mesh shadow mask was used to locally adjust the flux of indium tin oxide (ITO) sputtered particles, enabling the establishment of a relationship between the mask’s aperture geometry and the resulting particle deposition profile. The magnetic field and plasma simulations were integrated to model particle transport and design a specialized gradient aperture-based shadow mask, enabling the deposition of an ITO film with a controlled sheet resistance gradient in a single magnetron sputtering step. Experimental results demonstrated that the proposed method decreased the maximum temperature variation by 8.25 °C and reduced the standard deviation of the surface temperature by 82.1% at an average temperature of 45 °C within a defined nonrectangular heating region, demonstrating a substantial improvement in temperature uniformity relative to conventional uniform coating processes. Full article

Residential heat pumps have advanced over the past decade to allow for operation at colder temperatures. However, the challenges of frost accumulation and defrosting the outdoor coil remain. The goal of this study was to evaluate the impact of the control algorithms that determine when a heat pump needs to defrost and when the base pan heater runs on the overall heating efficiency of the heat pump. In this study, which occurred during the 2023–2024 heating season, we measured the performance of a ductless air-source heat pump installed in Fairbanks, Alaska, USA. The heat pump was instrumented to measure the electrical input and the thermal output, as well as selected internal variables and indoor and outdoor environmental conditions. The heat pump was first operated with factory default control algorithms associated with the initiation of defrost and control of the base pan heater. These factory default algorithms focused on aggressively defrosting the outdoor coil and keeping the base pan ice-free. In the middle of the winter, these algorithms were changed to focus on reducing defrost cycles and increasing efficiency, while the heat pump continued to be operated and monitored. The results showed that significant increases in efficiency are possible by improving the defrost and base pan heater control algorithms. Full article