Temperature Control Strategy Research Articles

Fuel cell plug-in hybrid electric vehicle thermal management strategy in parking time for low-temperature environments

This work presents a thermal management strategy for fuel cell hybrid electric vehicles under low-temperature conditions. Protecting the fuel cell system (FCS) and battery pack from such operating conditions prevent their degradation and performance decay. Thus, an approach similar to the keep-warm strategy is proposed to avoid the well-known issues related to the thaw-at-start methods, as well as promote a rapid startup after long parking periods. Particularly, the present work proposes a strategic synergy between the battery pack recharging and thermal management during the parking phase, so as to minimize the fuel consumption, while featuring vehicle to grid functionality and rapid startup of the vehicle when resuming driving. Such thermal management strategy was evaluated via simulation analyses, considering the transient thermal dynamics of the FCS and battery pack under low-temperature conditions and the temperature control strategy. The results outlined how proper exploitation of plugin functionalities, beyond introducing innovative vehicle-to-grid (V2G) concepts to suitably link driving to parking phases energy management, also allows for low-temperature safe thermal management of involved electrochemical devices. Finally, an economic analysis demonstrated that the proposed plugin-based vehicle to grid scenario presents a cost-saving potential of up to 56 % with respect to non V2G charge-sustaining one.

Kinetic study on the reaction routes in the oxidation of K/A oil by nitric acid with microreactors

A continuous-flow microreactor system was applied to evaluate the detailed kinetics of the reaction routes involved in the oxidation of K/A oil by nitric acid, which is essential to obtain an in-depth comprehension of complex reaction mechanisms, having important guiding significance for the two-stage temperature control strategy. 6-hydroxyimino-6-nitrohexanoic acid (AMNA) was identified as a major intermediate and its presence was confirmed through UPLC-MS and 1H NMR characterizations. A multi-step reaction kinetic model was developed, revealing good prediction with the experimental results. Finally, the model was applied to investigate the effects of operating parameters on the reaction routes distribution and reaction rate. The simulation results showed that high temperature and nitric acid concentration contributed to high selectivity of adipic acid through promoting the AMNA route, and greatly reduced the required reaction time, indicating that the accurate control over the conditions in this rapid and strongly exothermic process was of paramount importance.

Characteristic Prediction and Temperature-Control Strategy under Constant Power Conditions for Lithium-Ion Batteries

Accurate characteristic prediction under constant power conditions can accurately evaluate the capacity of lithium-ion battery output. It can also ensure safe use for new-energy vehicles and electrochemical energy storage. As the battery voltage continues to drop under constant power conditions, the battery current output will accordingly increase, which brings a risk of thermal runaway in instances of weak heat dissipation. Therefore, knowing how to control the battery temperature is very critical for safe use. At present, the model-based method for characteristic prediction and temperature control has been used by most scholars, and that is also the key to this method. This work firstly extends a cell model to a pack-based electrochemical two-dimensional thermal coupling model, considering the heterogeneity of different cells inside the pack, and obtains the model parameters for a prismatic lithium-ion battery with a rated capacity of 42 Ah. Characteristic prediction under constant power conditions is then conducted based on an iterative solution method. Validations of characteristic prediction indicate the convenience of the developed models, with average absolute errors of voltage and temperature less than 36 mV and 0.4 K, respectively, and power error less than 0.005%. Finally, two model-based temperature feed-forward control strategies with lower cooling costs and shorter prediction times were developed based on the battery characteristic predictions, which leaves room for further controller development.

Model based development of temperature control schemes for fighter aircraft ECS

The performance of Temperature Control System (TCS), a sub-system of an advanced fighter ECS (Environmental Control System) is studied for its operations both in on-ground and in-air conditions. The standard Bootstrap air cycle system is considered with ACM (Air Cycle Machine) as the main component, which consists of a compressor and a turbine, to produce the cold air. ECS, in particular TCS, is responsible in maintaining the required cockpit or cabin temperature. As the fighter aircraft doesn’t require cabin air recirculation, the cabin temperature depends solely on the supply air thermal conditions. The cabin temperature regulation is realized by controlling the supply conditions by maintaining required temperature at ACM outlet and at the entrance duct to the cabin. These temperatures are critical parameters that necessitates appropriate controller to keep the cabin in a good comfortable state. ECS of a fighter aircraft is highly complex and nonlinear than commercial aircraft. The control logics applied, on this system, will drive the actuators or TCVs (Temperature Control Valves) to keep the requisite cabin temperature. The control logics applied on the controller to be simple and appropriate to meet the requirements of fighter aircraft ECS. This shall minimize the control cycle oscillation and subsequent supply air temperature instabilities. This paper explains novel cabin temperature control schemes and their influence on the ECS performance especially during the transient operation. The complete architecture of the control schemes along with system components are modelled in AMESim and the comparison is made for different operating conditions. Finally, a novel variable time-delay based method to control the cabin supply air temperature is proposed.

Performance and Economic Analysis of the Multi-Energy Complementary Heating System under Different Control Strategies in Cold Regions

Multi-energy complementary heating (MECH) is the most promising and potential heating technology of the future. However, owing to the increase in energy types, the system is complex, and the operation procedure cumbersome. In addition, due to the uncertainty of climate conditions, it is difficult to develop a general control strategy suitable for all heating systems. In order to study the optimal control strategy of MECH systems with solar, biomass, and electric energy as three heat sources in cold regions, the system heating was tested over different periods during the entire heating season for rural residential buildings in cold regions, and the operating performance of the system was evaluated. The MECH experiment, based on the optimal control strategy, was compared with other different heating systems, and the economic and environmental benefits of the system were further evaluated. The results showed that, compared with room temperature control strategy (RS-CON), the control strategy of the heat storage tank (HST-CON) with sufficient solar energy (SE) can afford a higher solar fraction by 10%, more HST heating hours, and lower operating costs and CO2 emissions. During heating operation, Mode 3 [biomass boiler (BB) + heat storage tank (HST) heating] was the best heating mode. At the end of the heating period, Mode 5 (HST heating) met the indoor heat demand and had a significant energy-saving effect. From the perspective of the whole heating season, HST-CON heating operation can generate lower energy consumption costs and achieve almost zero CO2 emissions. This study is of great significance because it provides an engineering reference for the rational the utilization of MECH systems in cold regions.

Cooling load comparison of rooms conditioned with radiant cooling panels and all-air HVAC systems (ASHRAE RP 1729)

Radiant cooling systems have the potential for efficient chiller operation by using a higher chilled water temperature when compared to all-air systems. This affects the system efficiency, but it is not clear how the cooling load for these two systems is different. The present experimental study investigates differences between (i) room cooling load and (ii) overall heat transfer for (a) radiant and (b) all-air systems. It compares the thermal performance of these two systems for identical rooms considering different heat gains: (1) solar heat gain, (2) internal convective gains, and (3) internal radiative gains. Results show that for the same indoor air temperature the peak load is slightly higher for radiant systems (10% or smaller), regardless of the type of space heat gain. When considering thermal sensation, the performance of the two systems can be compared instead at the same operative temperature. The results also show that the cooling load for a radiant system depends greatly on the temperature control strategy (air vs operative temperatures). When operative temperature is used for the system control, the design load for radiant panels is almost the same as that of all-air systems, regardless of the type of the dominant space heat gain.

Numerical study of fuzzy-PID dual-layer coordinated control strategy for high temperature uniformity of space lithium-ion battery pack based on thermoelectric coolers

Excessive temperature difference within the battery pack is an important reason for its reduced energy conversion efficiency and reliability. A fuzzy-PID dual-layer coordinated control strategy with high temperature uniformity based on thermoelectric coolers is proposed for the thermal problems of the lithium-ion battery pack for space applications. The dynamics model of the battery thermal management system is established, and the open-loop characteristics of the lithium-ion battery pack under the influence of the discharge time of the lithium-ion battery pack in an orbital cycle, the thermal-optical properties of the satellite surface, and the volume flow rate of the working medium in the cold-plate are numerically studied during the orbital operation. The control effect of the fuzzy-PID dual-layer coordinated controller is numerically evaluated, and the results show that it can maintain the average temperature of the Li-ion battery pack in the predetermined optimal temperature range of 15– 35 °C under complex thermal disturbances, and the maximum temperature difference does not exceed 1.7 °C, which is 76.7 % smaller than that without active control, and the minimum temperature difference is only 0.06 °C. This temperature control strategy can significantly improve the temperature adaptability of the space Li-ion battery pack and help further improve its operational performance and reliability.

Optimal sizing and control strategy of low temperature solar thermal utility systems

This work describes the development of an integrated method for the design of networks of flat plate solar collectors and a temperature control strategy. The main stages of this methodology include the optimization of single collector geometry, size and structure of the network, energy storage system, and design of a temperature control system. Solar network inlet temperature and flow rate are maintained at its optimal value and outlet temperature is conditioned to meet the process specifications. Comparison with common temperature control based on the manipulation of network inlet flow rate is presented. A case study to supply 480 l/min of water at 70 °C is analysed. Results shows that the network operates efficiently throughout the year using the alternative control strategy. In terms of the solar network design, the results indicate a reduction of 52.3% in payback time compared to networks that use commercial collectors, reduction of 21.4% in payback compared to the purchase and installation of a natural gas boiler, and reduction in CO2 equivalent gas emissions of 759.6 t/y. In terms of the operation, the results show a reduction in pumping costs of about 24,584 USD/y, compared to the control strategy based on flow rate manipulation.

Thermal design analysis for SuperTruck II lithium-titanate battery pack

This paper presents a systematic thermal management analysis for a new lithium-titanate-oxide battery pack to be installed in a SuperTruck II, Class 8 hybrid truck. The authors investigate the feasibility of mounting the battery pack inside the vehicle and air-cooling it with fans supplying conditioned air from the cabin. Moreover, the cells within each module are to be immersed in a heat-transfer fluid to improve temperature homogeneity. A multi-stage thermal analysis is performed to ensure adequate thermal regulation of the battery under the proposed design, considering installation and operational constraints. The authors perform thermal and electrical characterization tests on a single cell. Results inform the development of computational fluid dynamics models of the cells, modules, and pack. Module-level analysis shows that the cell temperatures can be maintained below their upper operational limit of 55 °C with module wall-to-air heat transfer coefficients between 10 and 20 Wm−2K−1. Pack-level analysis of distinct configurations determines effective airflow paths for adequate heat transfer and delivers a final battery pack design that achieves sufficient cooling and temperature uniformity. A reduced-order electrothermal model is developed to rapidly predict the transient battery performance and to develop a temperature control strategy.

A modelling method for large-scale open spaces orientated toward coordinated control of multiple air-terminal units.

The temperature distribution is always assumed to be homogeneous in a traditional single-input-single-output (SISO) air conditioning control strategy. However, the airflow inside is more complicated and unpredictable. This study proposes a zonal temperature control strategy with a thermal coupling effect integrated for air-conditioned large-scale open spaces. The target space was split into several subzones based on the minimum controllable air terminal units in the proposed method, and each zone can be controlled to its own set-point while considering the thermal coupling effect from its adjacent zones. A numerical method resorting to computational fluid dynamics was presented to obtain the heat transfer coefficients (HTCs) under different air supply scenarios. The relationship between heat transfer coefficient and zonal temperature difference was linearized. Thus, currently available zonal models in popular software can be used to simulate the dynamic response of temperatures in large-scale indoor open spaces. Case studies showed that the introduction of HTCs across the adjacent zones was capable of enhancing the precision of temperature control of large-scale open spaces. It could satisfy the temperature requirements of different zones, improve thermal comfort and at least 11% of energy saving can be achieved by comparing with the conventional control strategy.Electronic Supplementary Material (ESM)the Appendix is available in the online version of this article at 10.1007/s12273-022-0942-8.

Sparrow search algorithm applied to temperature control in PEM fuel cell systems

Working temperature is a critical parameter that influences the performance of proton exchange membrane fuel cells (PEMFCs). Appropriate thermal management can improve the efficiency of PEMFCs and prevent irreversible internal damage such as membrane degradation. To solve the slow response and poor dynamic performance of traditional temperature control strategies, the dynamic temperature mode of PEMFCs is established and a temperature control strategy based on the sparrow search algorithm-proportional integral differential (SSA-PID) is proposed in this study. The performance of the SSA-PID temperature control is verified by the simulations of current step change, vehicle dynamic load, and working parameter variation. The results show that the proposed method has the advantages of fast convergence, better dynamic performance, and anti-disturbance ability. The maximum power density of the SSA-PID temperature controller is 6.58% and 12.94% higher than GA (genetic algorithm)-PID and traditional PID controllers, respectively. Moreover, the proposed method can ensure temperature fluctuations within 0.5 K under dynamic disturbance.

Investigation on the Temperature Distribution Uniformity of an Extrusion-Based 3D Print Head and Its Temperature Control Strategy

Extrusion-based 3D printing for thermoplastic polymers manifests potential for the fabrication of biocompatible and biodegradable scaffolds. However, the uncontrollable shape of printed filaments usually negatively impacts on the printing processes. Non-uniform temperature in the print head is a primary cause of inaccuracy in the diameter of filaments formed during the process of extruding thermoplastic polymers. Therefore, the temperature distribution inside the print head must be controlled accurately. This study developed a novel print head configuration with two groups of controllable heat sources for extrusion-based printing of thermoplastic polymers. Subsequently, a numerical thermal analysis based on the finite element method (FEM) was conducted to investigate the temperature field in the print head during the heating process. Moreover, a temperature control strategy is proposed under which the temperature distribution of the print head can be regulated. The temperature uniformity can be improved with the proposed temperature control strategy. Lastly, groups of printing trials were implemented, and the printed filaments showed excellent uniformity of diameter when temperature distribution uniformity was controlled in the print head.

Study on dynamic model and dynamic characteristics of Delingha 50 MW trough solar field

China General Nuclear Power Group (CGNPC) Delingha 50 MW parabolic trough solar thermal power plant is the first commercial trough solar plant in China, and its solar field consists of 190 parallel heat collecting loops. For large-scale trough solar plant, balancing the flow rate of heat absorbing medium in each loop and stabilizing the outlet temperature are the key technologies and difficult problems. Regarding the Delingha 50 MW solar field as the research object, this paper mainly focusing on the dynamic characteristics of flow and heat transfer in the solar field. The hydrodynamic calculation model and the heat transfer dynamic model are established on the real-time dynamic simulation platform STAR-90. With the actual operation data, the built solar field model is validated by comparing the simulation results. On this basis, the disturbance simulations of direct normal irradiance (DNI), heat transfer oil’s mass flow and heat transfer oil’s inlet temperature are carried out. The dynamic response curves of disturbance and the thermal inertia time constant of the loops are obtained. The conclusions lay a theoretical foundation for the formulation of outlet medium’s temperature control strategy in the solar field of large-scale trough solar thermal power generation system.

Design of a Proportional-Control-Based Advanced Control Strategy for Independent Temperature and Humidity Control of a Pre-Cooled Desiccant Air Cooling System

In this study, the control of a desiccant-wheel-based evaporative cooling system with a double-layer dew-point cooler system is emphasized. There are two dew-point evaporative coolers in the system and the air taken inside is subjected to pre- and post-cooling processes. The dehumidification process of the air taken in is carried out by the desiccant wheel after the pre-cooling process. A proportional-based control strategy has been developed to adjust the temperature and relative humidity of the room quickly and robustly with different operation modes for actuators to bring comfort with less energy consumption. In addition, an automatic Stop/Run mode has been added to the control strategy to save extra energy. With the developed control strategy, enabling the actuators to switch between the operation modes, more energy savings are achieved compared to both traditional ON/OFF and proportional controls. The accuracy and applicability of the developed control strategy were analyzed and it was observed that the room comfort reached the desired levels successfully under all disruptive effects. The control inputs and the energies consumed by all the actuators were investigated and it was determined that 21.19% more energy savings are provided by adding the automatic Stop/Run feature. With the multi-mode control strategy, a total of 40.90% less energy consumption is achieved compared to the classical ON/OFF control technique. Thus, it is seen that the controller developed for the desiccant-wheel-based evaporative cooler is a viable method to provide fast and robust comfort conditions with less energy.

HVAC Control Systems for a Negative Air Pressure Isolation Room and Its Performance

The controlled environment room, called an isolation room, has become a must have for medical facilities, due to the spreading of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), to isolate the high risk infected patients. To avoid the transmission of the virus through airborne routes, guidelines were published by the government and the association. A medical facility must comply with this document for high-risk patient treatment. A full-scale N class isolation room was built at Syiah Kuala University to investigate the performance in terms of the controller, temperature, pressure, humidity, and energy consumption. The isolation room was equipped with a proper capacity heating, ventilating, and air conditioning (HVAC) system, which consisted of an air conditioning compressor and a negative pressure generator (NPG), and its installation was ensured to fulfil the guidelines. Since the current NPG was controlled manually, a computer-based control system was designed, implemented, and compared with the manual control. The results showed that the computer-based control outputs better stability of pressure and electric power. For that reason, a computer-based control was chosen in the real case. To investigate the performance of the isolation room, a 24 h experiment was carried out under different parameter setups. The results showed that improvement of the control strategy for temperature and humidity is still necessary. The energy consumption during the activation of the NPG for the recommended negative pressure was slightly different. An additional piece of equipment to absorb the heat from the exhaust air would be promising to improve the energy efficiency.

Composting effect and antibiotic removal under a new temperature control strategy

The main objective of this study was to investigate the feasibility of a new temperature control strategy in the co-composting process to accelerate operation cycle and remove antibiotics from mixed organic wastes. The evaluation of the composting process showed that composting with temperature control (TC) was completed within 14 days. The final compost of TC exhibited a 10% higher degradation of organic matters, more humus formation and 11.25% lower heavy metals concentration than conventional composting (CC), which fully met the Chinese National Agricultural Organic Fertilizer Standard requirements. The degradation extent and kinetic of macrolides, tetracyclines, sulfonamides and fluoroquinolones showed that the removal efficiency of total antibiotics in TC was 23.58% higher than CC, with less half-life, which was significantly correlated with higher temperature. Particularly, the highest removal was observed for sulfonamides (87.45%) in TC, the half-life of which was reduced by 75.95% compared with CC. The higher degradation rate was attributed to enhanced decomposition of unstable antibiotics and degrading activity of microbes at high temperature. The microbiological analysis showed that the external heating led to a distinct composition and succession of bacterial community in TC. Firmicutes, Proteobacteria, Actinobacteriota and Bacteroidota were dominant and the emergence of Patescibacteria and Chloroflexi at cooling period in TC proved that the later composting environment was in an oligotrophic state. Current research provided a promising rapid composting approach for high-quality fertilizer production and antibiotic management in organic waste disposal.

Spider-based FOPID controller design for temperature control in aluminium extrusion process

Abstract Based on the exit temperature in the aluminium extrusion process, the quality of the aluminium bars is obtained in the industries. Control of temperature plays a significant role to obtain the quality of the aluminium bars or rods. Problems are still encountered in the design of proper temperature control schemes in the industries. A new control scheme is presented here, to address the temperature control in the aluminium extrusion process. Spider-based fractional-order PID controller scheme is simulated for the aluminium extrusion plant using MATLAB and its toolbox. It gives the improved result for reducing the time delay, rise time and settling time in the process. Integral square error performance criteria are considered an objective function. The minimization of objective function gives good results. Comparisons of the presented control scheme with the conventional control methods are presented.

A novel control scheme to mitigate temperature profile variation in a SOFC System

Maintaining temperature profile in a solid oxide fuel cell (SOFC) is one of the essential issues that need to be addressed during the load tracking. In this paper, a novel control scheme with three-loop structure is developed to mitigate SOFC temperature profile variation. This scheme can simply implemented by three variable-speed blowers. The first blower is an anode recirculation blower used to maintain anode inlet temperature, the second one is a cathode recirculation blower used to maintain cathode inlet temperature, and the last one is an air blower used to maintain cathode outlet temperature. Compared with other simple schemes with only one-loop or two-loop structure, the scheme with three-loop structure achieves the best performance in mitigating SOFC internal temperature profile variation and guaranteeing a safe margin on operation limits. With a 10% system load step drop, the three-loop control scheme presents the best performance in rapidity and stability, with a much smaller overshoot, a much shorter settling time, and the smallest ITAE criterion. The SOFC temperature profile variation is also smallest (deviating within 4.7 K). Time-dependent temperature gradient is much less than 3.0 K/min. Temperature gradient is significant less than 10 K/cm. Steam to carbon ratio is also kept more than 2.0. Furthermore, the three-loop control scheme can perform high system efficiency, which reaches 53.9% at the 90% load. As a result, the three-loop SOFC temperature control scheme is robust in safe and efficient operation.

Effect of Nutrient Solution Cooling in Summer and Heating in Winter on the Performance of Baby Leafy Vegetables in Deep-Water Hydroponic Systems

Hydroponics has become a popular production technology for leafy greens in greenhouses. However, year-round production of cool-season leafy greens remains challenging due to costly heating and cooling during winter and summer seasons, depending on location. Therefore, the objective of this study is to investigate the effect of nutrient solution cooling and heating in deep-water hydroponic systems on the performance of several leafy green vegetables. Two experiments of nutrient solution cooling during the summer season and another two experiments of nutrient solution heating during the winter season were conducted in Texas, USA in 2020–2021. Lettuce (Lactuca sativa L.) ‘Bergams Green’ and ‘Red Mist’, Pak Choi (Brassica rapa subsp. chinensis) ‘Purple Magic’ and ‘White Stem’, and spinach (Spinacia oleracea L.) ‘Mandolin’ and ‘Seaside’ were grown in the summer experiments, and only the two lettuce cultivars were grown for the winter experiments. For both cooling and heating studies, six deep-water culture systems were used with two treatments: cooling (23 °C) vs. no cooling, and heating (22 °C) vs. no heating, with three replications in each experiment. In the nutrient solution cooling study, spinach was the most heat-sensitive species, and ‘Mandolin’ was more heat-tolerant than ‘Seaside,’ as evidenced by its lower mortality rate in both experiments. Lettuce and pak choi grew well and solution cooling increased shoot fresh weight in both lettuce cultivars and in ‘White Stem’ pak choi but not in ‘Purple Magic’ pak choi. Conversely, during the winter season, solution heating increased shoot fresh weight of both lettuce cultivars; however, ‘Red Mist’ was more responsive than ‘Bergams Green’ lettuce. These results indicate the potential to increase crop yield by controlling nutrient solution temperature throughout the year, depending on the season. Also, there were genotypic differences in both cooling and heating experiments, indicating that more research is needed to determine the species-dependent and even cultivar-dependent nutrient solution temperature control strategies to achieve optimum year-round production.

Research on the temperature control strategy of thin-wall parts fabricated by laser direct metal deposition

To solve the problem that the macro-size, microhardness, and mechanical properties of the laser direct metal deposition (DMD) of thin-walled parts are inconsistent due to the heat accumulation, an improved three-dimensional finite element heat propagation model was developed to simulate the temperature evolution of the single-pass multi-layer thin-walled parts. The results show that the heat accumulation is contributed to the transformation of the heat dissipation mechanism from three-dimensional to two-dimensional, while the residual heat of the former layer has no significant effect on the heat accumulation of the current layer. The optimized strategy of decreasing laser power gradually is more effective than the optimized strategy of increasing the time interval between layers in maintaining the stability of the molten pool. The integrated optimized strategy of parabolic-shape laser power decreasing and time interval of 5 s is the most effective method to reduce the heat accumulation in the DMD of thin-walled parts. The thin-walled parts with an optimized deposition process have a more uniform width, finer microstructure, and higher microhardness. This work provides theoretical guidance for reducing the heat accumulation during DMD thin-walled parts and is beneficial to improving the uniformity of mechanical properties of thin-walled parts.