Search Results (309)

This study employs a multi-method, high-precision research approach to evaluate the thermal comfort performance of a window-based direct evaporative cooling (DEC) air conditioning system installed in a university dormitory building (50 rooms) in Beijing. To compensate for the insufficiency of single-day test data, the study was conducted continuously for 30 days from 1 June to 30 June 2026 (00:00–23:59 daily). Eight calibrated sensor sets were deployed in each of the 50 rooms (that is, eight fixed sensor sets per room × 50 rooms = 400 synchronously logged spatial measurement points, each integrating a fixed SHT35 temperature/humidity sensor with a matched hot-wire anemometer probe; this unusually dense, building-scale simultaneous deployment is uncommon in previous dormitory studies), recording data simultaneously across all rooms throughout the test period with the DEC units continuously operating. The research integrates field physical measurement data, standardized subjective questionnaire surveys (200 within-person paired questionnaires, each pairing a student’s retrospective recall of the pre-DEC condition with an in situ vote collected during DEC operation), and advanced computational thermophysiological modeling results based on the frameworks of ISO 7730–2021 and ASHRAE Standard 55–2023. Environmental parameters, including dry-bulb temperature (Ta), relative humidity (RH), and air velocity (Va), were monitored at eight spatially distributed points per room with a 10 Hz sampling frequency and a one-hour median resolution. The mean radiant temperature (Tr) was approximated as equal to Ta due to the absence of globe temperature measurements, and this simplification is discussed as a limitation. Simultaneously, through a single-session questionnaire (June 24–30) compliant with ISO 10551 and the Appendix B requirements of ANSI/ASHRAE Standard 55, which paired each respondent’s retrospective recall of the early-June pre-DEC (non-cooled) condition with a concurrent vote collected during DEC operation—a recalled-pre/concurrent-post design rather than two separate real-time pre-/post-intervention surveys—data on clothing ensembles, activity levels, and subjective thermal sensation votes (TSV) were collected. The acquired data were input into a customized simulation platform developed in the Fortran language (which was debugged and cross-validated against the ISO 7730/ASHRAE Standard 55 reference implementation to within 0.01 PMV scale units), which employs the Fanger two-node thermoregulation model to accurately calculate and predict the predicted mean vote (PMV), predicted percentage of dissatisfied (PPD) occupants, new effective temperature (ET*), and standard effective temperature (SET*). The results indicate that the DEC unit achieved a stable outlet temperature reduction of Δt = 3.87 °C (inlet temperature 31.72 °C, outlet temperature 27.85 °C), with an average wet-bulb air temperature of 18.66 °C and an average outlet relative humidity of 58.3% (inlet RH: 42.1%), confirming the expected humidifying effect of direct evaporative cooling while maintaining an average indoor relative humidity of 42.07%—a result particularly relevant to Beijing’s dry-to-semi-humid summer environment, where evaporative cooling is thermodynamically favorable. Because no DEC-off baseline period was monitored, the measured indoor conditions are reported as observational associations with DEC operation rather than as effects attributable exclusively to the unit; the pre-DEC satisfaction level was recalled retrospectively within the same single session and is therefore subject to recall/contrast bias; and all energy-saving figures are theoretical nameplate estimates rather than metered energy consumption. Full article

Thermoelectric air conditioning (TEAC) systems are gaining attention as refrigerant-free, solid-state cooling technologies due to their compactness, low noise, and environmental benefits. However, their widespread application is constrained by low energy efficiency and the limited experimental understanding of the coupled influence of electrical and aerodynamic operating parameters. Most existing studies address thermoelectric cooling under isolated conditions or rely on theoretical modeling, leaving a clear gap in the experimental quantification of the interactive effects of applied voltage and air velocity on system performance. To address this gap, the present study experimentally investigates a laboratory-scale TEAC system equipped with four thermoelectric cooler (TEC) modules (model TEC1-12706). The system was tested under controlled conditions by varying the input voltage from 6 to 12 V and the air velocity from 1 to 3 m/s. Key performance indicators, including cooling capacity, power consumption, cold-side temperature, and coefficient of performance (COP), were systematically measured and analyzed. The results show that increasing the applied voltage from 6 to 12 V enhances cooling capacity by approximately 50.4%, while significantly increasing electrical power consumption, leading to a 59% reduction in COP due to intensified Joule heating. Conversely, increasing air velocity improves convective heat transfer, resulting in a COP enhancement of about 24% with relatively stable power input. The findings highlight a clear trade-off between cooling capacity and energy efficiency and identify a practical operating region for balanced TEAC performance. Full article

Double-skin façades (DSFs) can moderate heat transfer and airflow between the outdoor environment and the building interior; however, their performance in hot-arid climates is highly dependent on cavity geometry, ventilation arrangement, and the interaction between the airflow and any active cooling surfaces. The objective of this study is to establish, under a single idealised extreme hot-arid design point, how sealed, ventilated and actively cooled double-skin façade cavities differ in their predicted temperature, velocity and turbulent kinetic energy fields, and which arrangements merit controlled follow-up study. The four configurations are treated as an idealised comparative case study rather than as validated building-performance predictions. This exploratory study uses computational fluid dynamics (CFD) to compare the aerothermal behaviour of four DSF cavity configurations under prescribed external air and outer-wall temperatures of 50 °C, an inner-wall temperature of 24 °C, and an external inlet velocity of 3.06 m/s. The configurations comprise a sealed 0.4 m cavity (M1), a wind-driven ventilated 0.4 m cavity (M2), the same ventilated cavity with six 25 mm cooling pipes at 10 °C (M3), and a concept-stage lateral-flow arrangement combining a 0.10 m cavity, a 0.025 m slit and four 80 mm cooling pipes at 10 °C (M4). The simulations employ the standard k-ε turbulence model with fixed thermal boundary conditions. Along the reported sampling lines, M1 exhibited a nearly uniform air temperature of approximately 45.7 °C, whereas M2 remained close to the imposed 50 °C external-air temperature. M3 produced lower temperatures in the immediate vicinity of the cooling pipes, but most of the sampled profile remained near ambient conditions. M4 exhibited a broader spanwise temperature range of approximately 26.9–50 °C, with local pipe-adjacent air temperatures approaching 24 °C and cooler regions developing along parts of the lateral flow path. The findings provide preliminary concept-screening evidence and support further controlled parametric analysis, higher-fidelity modelling, and experimental validation. Full article

To address the limited cooling range of ventilation in deep, high-temperature development headings and the lack of coordinated design between coil-based cooling and the ventilation system, this study proposes a coupled “twin-forcing–coil” cooling scheme. Building on conventional overlap (forcing–exhausting) ventilation, a rear-mounted second forcing duct is added to the conventional overlap (force–exhaust combined) auxiliary ventilation system, forming a dual-duct forcing, single-exhausting configuration—hereafter termed the “twin-forcing–single-exhausting” (TFSE) system—that provides a booster (relay) air supply to mitigate the along-path attenuation of cooling capacity and the short-circuiting of cold air; an in situ heat-exchange coil wall further provides supplementary cooling where ventilation-based temperature control weakens. Using a development heading at the 790 m level of a metal mine in Yunnan as the engineering background, a three-dimensional numerical model coupling the roadway, ventilation system, and coil wall was established and validated against nine field monitoring points, showing average relative errors of approximately 1% for temperature and 2–3% for humidity, comparable to the measurement uncertainty of the field instrumentation. Because the numerical model does not account for evaporative and condensation phase-change processes, two supplementary development headings with standing water at the face were used for validation; results showed that model error increases with water accumulation and heading length, indicating the model’s applicability is limited to conditions with intact surrounding rock and minimal seepage. Six operating cases were designed with duct placement and coil spacing as variables. Results show that single-duct ventilation cooling decays markedly beyond 30 m from the face, whereas twin-forcing booster (relay) air supply effectively extends the cooling range, reducing the 30–70 m section temperature by 2.7–2.9 K; the second duct should be positioned where the first duct’s cooling capacity begins to attenuate but is not yet depleted. Based on only two spacing configurations tested (10 m and 15 m), coil-staggered spacing showed limited effect on cooling performance under the field conditions examined; this preliminary finding requires validation across a broader range of spacings. Among the chilled-water conditions tested, an inlet temperature of 280.65 K and a flow velocity of 0.5 m/s offered a reasonable trade-off between cooling uniformity and economic efficiency. Under the boundary conditions and equipment parameters of this case, energy consumption estimates further indicate that the cooling effect per unit electricity consumption of twin-forcing ventilation is roughly 6–8 times that of coil-based cooling, primarily due to pumping losses over the ~240 m chilled-water delivery distance. This energy penalty indicates that coil-based cooling is better suited as a localized, short-distance supplementary measure rather than as a means of extending the cooling range over long distances. Full article

A computational fluid dynamics and conjugate heat transfer (CFD+CHT) methodology is developed for the thermal simulation of a commercial prismatic ${\mathrm{LiFePO}}_4$ cell under charging and discharging operating conditions. The approach couples a three-dimensional representation of the battery, including a simplified description of its internal layered structure, with an electrochemical–thermal heat-generation model implemented as a temperature- and time-dependent volumetric source term. The heat source is applied within the active layers of the cell and updated during the transient simulation according to the local thermal state and to the evolution of the state of charge. The methodology is applied to 1C and 2C cycles under natural convection and forced-air cooling at free-stream velocities of $10\mathrm{m}{\mathrm{s}}^{-1}$ and $20\mathrm{m}{\mathrm{s}}^{-1}$. A dedicated wind-tunnel campaign is carried out on the same cell, instrumented with type-K thermocouples distributed over its external surfaces, to provide experimental data for model validation. The results show that the proposed framework accurately reproduces the main wall-temperature trends observed experimentally. Under natural convection, the temperature distribution remains nearly uniform, whereas forced convection produces more pronounced vertical and in-plane gradients. For the charge cycles, the comparison between CFD predictions and end-of-cycle measurements yields a mean absolute error (MAE) of ${0.66}^{\circ }\mathrm{C}$ and a root-mean-square error (RMSE) of ${0.82}^{\circ }\mathrm{C}$ over 168 measurement locations. The discharge cycles yield a comparable level of agreement (MAE ${0.65}^{\circ }\mathrm{C}$, RMSE ${0.81}^{\circ }\mathrm{C}$ over 168 probe points), confirming the predictive capability of the methodology for both operating modes. Full article

The scientific paper is focused on research into the effect of the end tanks’ material on the automotive engine’s radiator and the effect of the air-cooling mode on the efficiency of heat dissipation under engine idling conditions. Aluminium (AL) and plastic (PL) end tanks are compared when changing the cooling mode by fan on the radiator F1, the ram air fan F2 in the range of 6 to 10 m/s, and their combination F1+F2, in relation to cooling time and heat transfer parameters. The temperature parameters of the coolant during the cooling process are evaluated, and the values for the heat transfer rate, total heat transfer coefficient, and thermal efficiency are calculated. The correlating equations are created for the total heat transfer coefficient depending on the cooling mode. The AL radiator is more efficient in terms of total heat transfer coefficient compared to the PL radiator, ranging from 15.3% to 66.4% for all cooling modes. The combination of F1 and F2 cooling modes resulted in more efficient heat dissipation from both radiators. In the combined cooling mode, with a ram air velocity of 10 m/s, the PL radiator achieved maximum thermal efficiency of 94.3% at the cooling time of 55 s. The full-aluminium radiator is suitable for high-performance applications. Full article

Battery thermal management systems (BTMSs) are essential for maintaining the performance, efficiency, durability, and safety of electric-vehicle battery packs. Although fin-enhanced air-cooled BTMSs offer a simple and leakage-free cooling solution, their practical implementation is often limited by increased weight, insufficient temperature uniformity, and restricted heat-dissipation capability under high thermal loads. This study numerically investigates a compact air-cooled BTMS for two types of cylindrical lithium-ion batteries using aluminum and polypropylene (PP-$\beta$) circumferential fins in inline and staggered cell arrangements. Unlike previous fin-based air-cooling investigations, the present study combines a compact 2 × 4 battery pack with transverse and longitudinal center-to-center cell pitches of 1.2D, a direct comparison between metallic and lightweight polymer fins, and an assessment of two 18650 battery types with different capacities, thermophysical properties, and heat-generation characteristics. A three-dimensional steady-state conjugate heat-transfer model was developed in ANSYS Fluent to evaluate the effects of fin number, fin material, cell arrangement, ambient temperature, and inlet airflow velocity under discharge rates ranging from 1 C to 4 C. The results reveal that increasing the number of fins consistently reduced the maximum cell temperature but increased the pressure drop. The inline configuration generally achieved a lower maximum temperature and higher Nusselt number (Nu), whereas the staggered arrangement maintained a substantially lower pressure drop. Relative to the corresponding finless configurations, the Nu increased by 64.4–71.2% for the inline arrangement and 86.4–98.1% for the staggered arrangement. Polypropylene fins provided thermal performance close to that of aluminum fins in terms of maximum temperature while reducing the total fin mass by approximately 44.8%; however, aluminum fins maintained better temperature uniformity. These findings quantify the trade-offs among thermal performance, pressure drop, compact cell spacing, and system weight, providing design guidance for compact fin-enhanced air-cooled BTMSs. Full article

In response to issues such as disordered airflow distribution and prominent local hotspots in campus non-standard data centers, this study took a non-standard raised-floor air-supply data center at a university in Hangzhou as the research object, and used a combination of on-site measurements and computational fluid dynamics (CFD) numerical simulation to investigate the optimization of the thermal environment. The temperature and air velocity of the data center were measured using a handheld hot-wire anemometer, and a standard k-ε turbulence model was established on the 6SigmaDC platform (now Cadence Reality DC Design Pro, version 2024.1). Model accuracy was confirmed through grid independence verification with three mesh levels and statistical error metrics (MAE, MBE, RMSE) across multiple measurement zones. The results show that the mean absolute error of temperature does not exceed 0.9 °C in all zones and the mean absolute error of air velocity does not exceed 0.20 m/s, indicating that the model effectively reproduces the airflow distribution and thermal environment of the data center. On this basis, to address the uneven airflow distribution in the underfloor plenum, an optimization strategy was proposed that involved the installation of composite baffles and the coordinated adjustment of variable floor tile openings. Eight representative simulation scenarios were designed, with the coefficient of variation and air supply uniformity index as evaluation indicators. Results indicate that the combined effect of perforated baffles and variable floor tile openings is the optimal strategy, reducing the range of net airflow among air supply outlets from 0.100 to 0.077 m³/s, decreasing the coefficient of variation from 12.8% to 10.8%, and increasing the air supply uniformity index by 10.7%. Whole-room thermal environment verification shows that the optimal scheme reduces the supply heat index (SHI) from 0.42 to 0.35, with an estimated PUE reduction of about 0.03, achieving both airflow uniformity improvement and energy-saving benefits. By improving the cooling efficiency and reducing the PUE, this retrofit strategy contributes to the sustainable operation of small-to-medium-sized campus data centers, supporting energy efficiency and carbon footprint reduction goals under green campus and low-carbon initiatives. Full article

To advance the goals of carbon peaking and carbon neutrality alongside the global energy transition, energy conservation and carbon reduction in refrigeration and air-conditioning systems have garnered widespread attention. Dew-point evaporative cooling (DPEC) represents a promising energy-efficient cooling technology, whose performance is strongly governed by the water supply strategy. This study presents a systematic comparison of falling-film and atomization water supply modes on a counter-flow DPEC test bench featuring 3D-printed palm fiber filament walls. Experiments were conducted over inlet air temperatures of 32–50 °C, velocities of 1.3–4.0 m/s, and a range of water supply temperatures. The results demonstrate that the falling-film mode yields 15–25% higher dew-point efficiency than the atomization mode under baseline operating conditions. Water supply temperature (15–30 °C) exerts a negligible influence on falling-film cooling performance. The hybrid falling-film–atomization mode achieves the highest cooling capacity in the medium-to-low air velocity range, with a maximum wet-bulb efficiency of 1.15, while the falling-film mode yields the highest COP of up to 2.2. These findings offer experimental guidance for optimizing water supply strategies in fiber-wall DPEC systems. Full article

Thermal comfort shapes occupant health, well-being, and productivity and influences the sustainability and energy efficiency of the built environment. The Predicted Mean Vote (PMV) is the most widely used thermal comfort index, yet four of its six input parameters—globe temperature, clothing insulation, metabolic rate, and air velocity—require specialized, costly equipment or occupant self-reporting, which has long limited its practical large-scale application. This study introduces a machine learning (ML) framework aimed at estimating these four parameters using indoor and outdoor air temperature and relative humidity as its only sensor inputs, complemented by readily available contextual information and individual activity profiles. It exploits the climatic coupling of globe temperature and air velocity to the indoor–outdoor environment and the temperature- and activity-driven behavioral patterns that govern clothing insulation and metabolic rate. The proposed framework achieved strong predictive performance, explaining 85% of the variance in actual PMV values (R² = 0.85), with a near-zero mean residual (−0.041) and a residual standard deviation of 0.286. Approximately 91% of absolute errors fell below 0.5 PMV units—a deviation unlikely to shift the assigned thermal comfort category. Mapped to thermal comfort categories, predictions reached 80% accuracy, with a macro-averaged precision of 0.81 and recall of 0.80, exhibiting the highest performance for neutral and warm conditions while performing less accurately for cool discomfort. These results suggest that standard temperature and humidity sensors, combined with basic contextual information and individual activity profiles, could support reliable PMV-based thermal comfort assessment, advancing scalable, sensor-light comfort monitoring for energy-efficient, sustainable buildings. Full article

Amidst global carbon neutrality goals, China’s building energy consumption gains prominence, with heating and cooling exceeding 50% of the total. Underground structures leverage inherent geological thermal inertia to significantly reduce ventilation energy demands. This study employs combined field measurements and numerical simulations to investigate heat exchange mechanisms and performance in underground hydropower station air intake tunnels. Four representative tunnels (Sichuan, Fujian, Hebei, Yunnan) served as case studies, monitoring air temperature, humidity, velocity, and wall temperature. Field-monitored parameters informed a computational fluid dynamics (CFD) model, enabling quantitative analysis of rock thermal conductivity, inlet air velocity, and wall temperature effect on heat exchange efficiency. Research shows that: (1) significant seasonal adaptive characteristics exist, achieving peak cooling efficiency (69.04%, summer) and heating efficiency (78.86%, winter); (2) rock thermal conductivity is the primary efficiency determinant—quartzite tunnels exhibited 11.8% higher average efficiency than tuff tunnels; and (3) inlet air velocity negatively correlates with efficiency, exceeding 90% at 0.1 m/s but declining to 69% at 1.5 m/s. This work provides a theoretical basis for optimizing energy-efficient ventilation in underground engineering and validates the pivotal role of rock thermal inertia in reducing operational building energy consumption. Full article

In this study, the cooling performances of various nanofluids were compared under the operating conditions of a real automobile radiator, based on an internal combustion engine vehicle cooling system whose experiments had been previously completed. In the analyses, the radiator inlet fluid temperature was fixed at 70 °C, air inlet velocities were set to 6, 8, and 10 m/s, and fluid flow rates were taken as 17, 19, and 21 L/min. Under these conditions, the cooling capacities were evaluated for three different working fluids whose thermophysical properties were experimentally determined: 100% pure water, water-based 0.3% ZnO nanofluid, and water-based 0.3% ZnO + CuO hybrid nanofluid. Within the scope of this study, a Computational Fluid Dynamics (CFD) model was developed based on the aforementioned experimental parameters and validated with a maximum deviation of 6%. Using the validated model, additional CFD analyses were performed for water-based 0.3% Al₂O₃ and TiO₂ nanofluids, whose thermophysical properties were also experimentally determined, and their cooling performances were assessed. Based on the experimental and numerical results obtained, the highest cooling capacity was determined to be 20.8 kW in the 0.3% TiO₂ nanofluid, representing a 69.1% increase in cooling capacity compared to pure water. These findings clearly demonstrate that the use of nanofluids significantly enhances heat transfer performance in automotive cooling systems. Full article

The year-round rising demand for fresh, high-quality vegetables has driven rapid growth in South Korea’s protected horticulture since the 1990s, resulting in widespread greenhouse installations across South Korea. However, maintaining optimal indoor environmental conditions in greenhouses remains challenging owing to extreme seasonal variations. During summer, indoor temperatures may exceed 35 °C despite active cooling systems; meanwhile, large temperature gradients between the indoor and outdoor environments require effective heating strategies in the winter. A key technology for stabilizing crop productivity and mitigating spatial environmental imbalances is the use of air circulation fans, which promote uniform distribution of temperature, humidity, and CO₂. This study investigates the airflow dispersion characteristics of agricultural circulation fans using computational fluid dynamics (CFD) simulations to support improved airflow distribution within greenhouses. The target facility was a multi-span Venlo-type greenhouse. Six circulation fans were installed 5.8 m above the ground, and their airflow patterns were analyzed under different layout scenarios, including uniform spacing and zigzag arrangements. The results showed that a single fan generated an effective airflow area of up to 193.14 m² and a dispersion distance of 60.34 m. When all fans were aligned in the same direction, airflow distribution was less efficient compared with configurations where central fans were reversed or installed in a zigzag pattern. Specifically, staggered arrangements improved the overall airflow distribution, with the volume-averaged air velocity increasing from 0.290 to 0.369 m/s. The study concludes that fan installation spacing and arrangement significantly influence airflow distribution and uniformity in greenhouses. Full article

Human innovation has continually expanded the boundaries of knowledge, from mastering atomic science to reaching the Moon and now into the era of Industry 4.0, where artificial intelligence, the Internet, and advanced additive manufacturing turn imagination into reality. Among these achievements, hypersonic vehicles represent a pinnacle of technological advancement. Modern vehicles reach speeds exceeding Mach 27 (approximately 9300 m/s), where the air at the leading edges transforms into a chemically reactive, thermally ionized plasma. At such velocities, stagnation temperatures climb to 9000–12,000 K (8726.85–11,726.85 °C), creating one of the most extreme environments encountered by any human-made system—conditions under which conventional materials cannot survive without advanced cooling strategies. To address this challenge, researchers worldwide have developed and experimentally validated a range of thermal protection and leading-edge cooling techniques. This review presents the historical evolution of hypersonic vehicles, highlights recent advancements, examines the key challenges posed by sustained hypersonic flight, and surveys state-of-the-art cooling strategies. The discussion emphasizes methods that combine passive, active, adaptive, and hybrid approaches to protect vehicle integrity under extreme thermal loads, providing insight into the current and future capabilities of hypersonic thermal management. Full article

The automotive panoramic roof exhibits a large-size and thin-wall geometry, with a length-to-thickness ratio approaching the thousand level. This geometric feature makes its forming quality highly sensitive to forming conditions. During the glass molding process, variations in temperature evolution, loading, and cooling parameters may lead to residual stress accumulation and springback deformation, thereby affecting dimensional accuracy and final forming quality. In this study, a full-process finite element model was established and combined with an L16(4^5) orthogonal design to investigate the effects of five key process parameters—heating temperature, holding time, quenching air velocity, quenching air pressure, and quenching time—on the mean residual stress and mean springback displacement in the glass molding process (GMP). The results showed that, within the given parameter ranges, heating temperature, holding time, and quenching time had relatively pronounced effects on the mean residual stress; the mean residual stress was relatively low when the heating temperature was 680 °C, the holding time was 3 s, and the quenching time was 12 s. Heating temperature, quenching air velocity, and quenching time had relatively pronounced effects on the mean springback displacement; the mean springback displacement was relatively low when the heating temperature was 677.5 °C, the quenching air velocity was 13 m/s, and the quenching time was 10 s. Based on the orthogonal analysis, regression models for the mean residual stress and mean springback displacement were further developed, and parameter combinations were screened using the NSGA-III method. Experimental validation showed that the relative error of the mean residual stress was controlled within 15%, indicating that the established model could, to some extent, capture the relationship between process parameters and forming quality indicators, thereby providing guidance for precision forming and process optimization of large-scale thin-walled automotive panoramic roofs. Full article