Temperature control is widely used in industrial processes, where Programmable Logic Controller (PLC)-based PID controllers are preferred for their robustness and ease of implementation. However, their compact structure and parameter tuning require a good understanding of system dynamics. While PLC-based thermal control systems have been widely reported, an experimentally validated model-based control (MBC) approach integrated with a comprehensive performance evaluation of industrial controllers appears to be lacking in the literature. This study presents the experimental and theoretical investigation of a PLC-based thermal system implemented with a Siemens S7-1200 PLC and a two-degree-of-freedom (2-DoF) PID controller. The experimental thermal system comprises a PT100 sensor and a 100 W resistive heater mounted in a prismatic plexiglass chamber (20 × 13 × 9.5 cm) with an insulated bottom surface. The system output is the temperature measured by the PT100 sensor, while the heater is driven by a pulse-width modulation (PWM) signal through a solid-state relay. Various open-loop and closed-loop tests are conducted on the experimental system. The thermal process is first characterized experimentally via system identification to obtain a mathematical model from input-output data. Although the thermal plant inherently exhibits nonlinear behavior due to transport delay and heat-transfer mechanisms, an equivalent linear model with a delay time is identified to facilitate controller synthesis using classical linear control theory. The accuracy of the identified model is experimentally verified through open-loop tests using an industrial commissioning methodology based on sequential pretuning and classical fine-tuning. Then, theoretical analysis is conducted to further evaluate the performance of the auto-tuned controller in closed-loop tests. Based on the validated model, equivalent FD-PID controllers are designed using controller parameters obtained from the PLC auto-tuning procedure. The closed-loop responses obtained from the MBC simulations are compared with the experimental results. The results demonstrate that the experimental dynamic behavior of the thermal system is accurately predicted by the MBC, despite the presence of unknown internal parameters in the Siemens PLC PID_Compact block. In addition, the effect of the setpoint weighting parameters of a 2-DoF PID controller on control performance is experimentally investigated to further improve the performance achieved by the auto-tuning procedure. The closed-loop performance specifications are evaluated using normalized results to ensure a fair comparison despite different initial temperatures. Overall, the proposed MBC design approach provides an effective method for the analysis and design of PLC-controlled thermal systems across a range of operating temperatures.
With the rapid development of microelectronics technology, electronic devices are evolving toward higher performance and greater integration, posing serious thermal management challenges, as chip overheating may compromise their stable operation. Boiling phase-change heat transfer is a key approach for addressing thermal management in high-performance electronic devices. To further enhance its heat transfer performance, this study investigates the effects of four surface structures and thickness-constrained spacing on pool boiling heat transfer. A thickness-constraints boiling experimental platform was built, and four surfaces—copper plate, two layers #200 mesh (2*#200 mesh), spiral woven mesh composite flat mesh (SFCM), and spaced spiral woven mesh (SSWM)—were designed and fabricated. Boiling morphologies and heat transfer performances were examined at restricted spacings of 5.7, 0.7, and 0.4 mm. Experimental results indicate that spatial confinement shortens the bubble nucleation to escape cycle, thereby enhancing boiling heat transfer as spacing decreases. At 100 W heat load, the surface temperature (Tc) of the copper block at 0.1 mm confined spacing was about 5 °C (4.7%) lower than that at 5.7 mm. At 5.7 mm spacing and power above 25 W, the Tc order from low to high was SSWM, 2*#200 mesh, SFCM, and copper surface. When spacing was reduced to 0.4 mm, the order changed to SSWM, copper surface, 2*#200 mesh and SFCM. Among all configurations, the SSWM exhibited the best boiling heat transfer performance. Consequently, designing an ultra-thin confined structure above the heat source may help to improve heat transfer, and applying a SSWM-like structure is expected to further reduce the heat source temperature, offering guidance for optimizing design of phase-change dissipation devices.
Suppressing battery thermal runaway and preventing its propagation have become critical safety challenges. This work investigates the suppression performance and cooling limits of compressed air foam (CAF) on prismatic NCM lithium-ion batteries. Single-cell tests were conducted to compare free burning, water spray, and CAF suppression, while module-scale tests were performed under CAF flow rates up to 12 L/min. Results show that CAF provides more sustained cooling to control battery fire than water spray, because it forms a stable foam blanket, enabling continuous liquid drainage, improved surface wetting, and prolonged evaporative cooling. In the single-cell comparison, CAF achieves a maximum cooling power of 3.0 kW and a maximum equivalent heat transfer coefficient of 350 W/m2⋅K, doubling that of water spray. The module-scale tests show 3 L/min is insufficient due to boil-off crisis, leading to a prolonged quenching process. Increasing the flow rate to 6 L/min improves liquid replenishment but remains insufficient to fully overcome the vapor barrier. At 12 L/min, the high-momentum foam spray penetrates the vapor layer and promotes transition/nucleate boiling at the cell surface, achieving a maximum cooling rate of 8.3 K/s and a maximum equivalent heat transfer coefficient of 7.0 kW/m2⋅K. These findings demonstrate that effective foam suppression of battery fires requires both sufficient coolant volume and high cooling power. Therefore, optimizing foam delivery intensity is essential for improving battery fire suppression and preventing thermal runaway propagation.
Quantifying temperature and species concentration in non-uniform McKenna flat flames via laser absorption spectroscopy (LAS) is critical for understanding reaction kinetics and validating kinetic models, numerical simulations and diagnostic techniques in fundamental combustion research. Traditional discrete tomography approaches suffer from limited performance with sparse sampling, while existing profile fitting strategies rely on extensive multispectral and prior field information to address the multi-solution issue. This work introduces spatial spectra from multiple radial positions into profile fitting, achieving high-precision inversion using only two absorption lines. Experiments were conducted at various heights above premixed CH4/air McKenna flames (Φ = 0.8, 1.0) using the H2O absorption lines at 6807.83 cm−1 and 7444.36 cm−1, yielding quantitative, high-resolution, two-dimensional temperature and H2O mole fraction distributions. Validation against thermocouple measurements identifies ΔR = 6 mm as a critical sampling resolution threshold for balancing accuracy, stability, and simplicity for the standard McKenna burner investigated in this study. Uncertainty analysis reveals that the inversion performance is highly dependent on both the number of optical paths and their spatial arrangements. This study provides a more robust optical measurement scheme for the quantitative diagnostics of axisymmetric reactive flows.
This study investigates the asymmetric oil discharge behavior and thermal performance of tapered roller bearings with under-race lubrication using Computational Fluid Dynamics (CFD) simulations and oil discharge experiments. A dimensionless large-end oil discharge ratio is introduced to quantify lubricant partition between the two bearing ends. The predicted discharge behavior is validated experimentally over 2000-6000 rpm, with a maximum relative deviation below 4%. Results show that centrifugal effects promote lubricant migration toward the large end, leading to dominant large-end discharge under most conditions. Increasing oil flow rate weakens preferential large-end discharge and improves cooling, although the additional thermal benefit becomes limited when the flow rate increases from approximately 105 to 140 L/h. Increasing rotational speed reduces lubricant retention and intensifies thermal accumulation; at 105 L/h, the area-averaged oil volume fraction on the roller and cage surfaces decreases by approximately 83% from 2000 to 6000 rpm. Shifting the oil inlet holes toward the small end and increasing the inlet hole diameter suppress preferential large-end discharge and improve thermal behavior, whereas increasing the number of inlet holes provides limited benefit. A 4 mm shift toward the small end reduces the large-end oil discharge ratio by approximately 13% at 3000 rpm. These results indicate that optimizing inlet-hole axial position and diameter is more effective than simply increasing inlet-hole number or oil-supply rate, providing practical guidance for under-race lubrication design and thermal management of tapered roller bearings.
