Showing papers on "Temperature control published in 2021"

Modeling and Analysis of Heat Dissipation for Liquid Cooling Lithium-Ion Batteries

Abstract: To ensure optimum working conditions for lithium-ion batteries, a numerical study is carried out for three-dimensional temperature distribution of a battery liquid cooling system in this work. The effect of channel size and inlet boundary conditions are evaluated on the temperature field of the battery modules. Based on the thermal behavior of discharging battery obtained experimental measurements, two temperature control strategies are proposed and studied. The results show that the channel width of the cooling plates has a great influence on the maximum temperature in the battery module. It is also revealed that increasing inlet water flow rate can significantly improve the heat transfer capacity of the battery thermal management system, while the relationship between them is not proportional. Lowering the inlet temperature can reduce the maximum temperature predicted in the battery module significantly. However, this will also lead to additional energy consumed by the cooling system. It is also found that the Scheme 5 among various temperature control strategies can ensure the battery pack working in the best temperature range in different depths of discharge. Compared with the traditional one with a given flow rate, the parasitic energy consumption in Scheme 5 can be reduced by around 80%.

Temperature, Ageing and Thermal Management of Lithium-Ion Batteries

Abstract: Heat generation and therefore thermal transport plays a critical role in ensuring performance, ageing and safety for lithium-ion batteries (LIB). Increased battery temperature is the most important ageing accelerator. Understanding and managing temperature and ageing for batteries in operation is thus a multiscale challenge, ranging from the micro/nanoscale within the single material layers to large, integrated LIB packs. This paper includes an extended literature survey of experimental studies on commercial cells investigating the capacity and performance degradation of LIB. It compares the degradation behavior in terms of the influence of operating conditions for different chemistries and cell sizes. A simple thermal model for linking some of these parameters together is presented as well. While the temperature appears to have a large impact on ageing acceleration above room temperature during cycling for all studied cells, the effect of SOC and C rate appear to be rather cell dependent.Through the application of new simulations, it is shown that during cell testing, the actual cell temperature can deviate severely from the reported temperature depending on the thermal management during testing and C rate. It is shown, that the battery lifetime reduction at high C rates can be for large parts due to an increase in temperature especially for high energy cells and poor cooling during cycling studies. Measuring and reporting the actual battery (surface) temperature allow for a proper interpretation of results and transferring results from laboratory experiments to real applications.

Fast and Accurate Control Strategy for Portable Nucleic Acid Detection (PNAD) System Based on Magnetic Nanoparticles.

Abstract: Portable nucleic acid detection (PNAD) systems are performed for sample processing, amplification and detection automatically in an individual device realizing "sample in, answer out." For this goal, numerous function modules should be integrated in a diminutive device, in which temperature controller is one of the most important modules. In a nucleic acid detection process, both sample processing and polymerase chain reaction (PCR) require fast and accurate temperature control to increase concentration and purity of the extraction product and to improve amplification efficiency. In this paper, a dual-channel temperature controller for PNAD systems is developed, which contains a printed circuit board (PCB) and an integrated control program with a fast and accurate control strategy. According to the principle of nucleic acid detection based on magnetic nanoparticles, the controller can work in different modes such as high-precision heating control for nucleic acid extraction, rapid thermal cycle control for PCR, and rate adjustable constant heating/cooling control for melting curve. Evaluatively, the average heating/cooling rate of the module can exceed about 6 C/s, while the temperature fluctuation was less than ± 0.1°C, which can meet the demands of PNAD systems very well.

Quasi-distributed fiber optic sensor-based control system for interstitial laser ablation of tissue: theoretical and experimental investigations

Abstract: This work proposes the quasi-distributed real-time monitoring and control of laser ablation (LA) of liver tissue. To confine the thermal damage, a pre-planning stage of the control strategy based on numerical simulations of the bioheat-transfer was developed to design the control parameters, then experimentally assessed. Fiber Bragg grating (FBG) sensors were employed to design the automatic thermometry system used for temperature feedback control for interstitial LA. The tissue temperature was maintained at a pre-set value, and the influence of different sensor locations (on the direction of the beam propagation and backward) on the thermal outcome was evaluated in comparison with the uncontrolled case. Results show that the implemented computational model was able to properly describe the temperature evolution of the irradiated tissue. Furthermore, the realized control strategy allowed for the accurate confinement of the laser-induced temperature increase, especially when the temperature control was actuated by sensors located in the direction of the beam propagation, as confirmed by the calculated fractions of necrotic tissues (e.g., 23 mm3 and 53 mm3 for the controlled and uncontrolled LA, respectively).

A Review on Temperature Control of Proton Exchange Membrane Fuel Cells

Abstract: This paper provides a comprehensive review of the temperature control in proton exchange membrane fuel cells. Proton exchange membrane (PEM) fuel cells inevitably emit a certain amount of heat while generating electricity, and the fuel cell can only exert its best performance in the appropriate temperature range. At the same time, the heat generated cannot spontaneously keep its temperature uniform and stable, and temperature control is required. This part of thermal energy can be classified into two groups. On the one hand, the reaction heat is affected by the reaction process; on the other hand, due to the impedance of the battery itself to the current, the ohmic polarization loss is caused to the battery. The thermal effect of current generates Joule heat, which is manifested by an increase in temperature and a decrease in battery performance. Therefore, it is necessary to design and optimize the battery material structure to improve battery performance and adopt a suitable cooling system for heat dissipation. To make the PEM fuel cell (PEMFC) universal, some extreme situations need to be considered, and a cold start of the battery is included in the analysis. In this paper, the previous studies related to three important aspects of temperature control in proton exchange membrane fuel cells have been reviewed and analyzed to better guide thermal management of the proton exchange membrane fuel cell (PEMFC).

Concepts, Roadmaps and Challenges of Ovenized MEMS Gyroscopes: A Review

Abstract: The MEMS gyroscope by means of oven control, or the so-called ovenized MEMS gyroscope, isolates the die from the external environment and utilizes a closed-loop temperature control system. It is thought to be important as it does not produce bias, scale factor drift made by thermal variations. Hence, a better temperature stability of the device is expected, which potentially benefits greatly the next generation of high-performance MEMS sensor. Herein, we attempt to provide a comprehensive review of many areas of the ovenized gyros, consisting of principle, key technology, the state-of-the-art results and suggestions. The thermal error mechanism and the importance of temperature control are introduced. The descriptions of the principles and characteristics of both on-chip and off-chip architectures are provided. To suppress heat dissipation at the package level, thermal resistance models based on conduction, convection, and radiation are established and analyzed. In terms of heating drive energy efficiency, comparisons have been made within VCCS (Voltage-Controlled Current Source), V-I (Voltage-to-Current) converters and PWM (Pulse Width Modulation), followed by the analysis of SSP (Single Set Point) and MSP (Multiple Set Point) algorithms. With regards the feedback control system, a systematic discussion on its common temperature detection methods, including CMOS PTAT (Proportional To Absolute Temperature), RTD (Resistance Temperature Detector) and TCF (Temperature Coefficient of Frequency) is presented. The control algorithms and limitations for the temperature control are also presented. At the end, we compared and discussed the most representative ovenized gyros to date, followed by suggestions to future development trends.

A rapid and controllable acoustothermal microheater using thin film surface acoustic waves

Abstract: Temperature control within a microreactor is critical for biochemical and biomedical applications. Recently acoustothermal heating using surface acoustic wave (SAW) devices made of bulk LiNbO3 substrates have been demonstrated. However, these are generally fragile and difficult to be integrated into a single lab-on-a-chip. In this paper, we propose a rapid and controllable acoustothermal microheater using AlN/Si thin film SAWs. The device’s acoustothermal heating characteristics have been investigated and are superior to other types of thin film SAW devices (e.g., ZnO/Al and ZnO/Si). The dynamic heating processes of the AlN/Si SAW device for both the sessile droplet and liquid within a polydimethylsiloxane (PDMS) microchamber were characterized. Results show that for the sessile droplet heating, the temperature at a high RF power is unstable due to significant droplet deformation and vibration, whereas for the liquid within the microchamber, the temperature can be precisely controlled by the input power with good stability and repeatability. In addition, an improved temperature uniformity using the standing SAW heating was demonstrated as compared to that of the travelling SAWs. Our work shows that the AlN/Si thin film SAWs have a great potential for applications in microfluidic heating such as accelerating biochemical reactions and DNA amplification.

Online implementation of a soft actor-critic agent to enhance indoor temperature control and energy efficiency in buildings

Abstract: Recently, a growing interest has been observed in HVAC control systems based on Artificial Intelligence, to improve comfort conditions while avoiding unnecessary energy consumption. In this work, a model-free algorithm belonging to the Deep Reinforcement Learning (DRL) class, Soft Actor-Critic, was implemented to control the supply water temperature to radiant terminal units of a heating system serving an office building. The controller was trained online, and a preliminary sensitivity analysis on hyperparameters was performed to assess their influence on the agent performance. The DRL agent with the best performance was compared to a rule-based controller assumed as a baseline during a three-month heating season. The DRL controller outperformed the baseline after two weeks of deployment, with an overall performance improvement related to control of indoor temperature conditions. Moreover, the adaptability of the DRL agent was tested for various control scenarios, simulating changes of external weather conditions, indoor temperature setpoint, building envelope features and occupancy patterns. The agent dynamically deployed, despite a slight increase in energy consumption, led to an improvement of indoor temperature control, reducing the cumulative sum of temperature violations on average for all scenarios by 75% and 48% compared to the baseline and statically deployed agent respectively.

Operating a Commercial Building HVAC Load as a Virtual Battery Through Airflow Control

Abstract: Virtual battery (VB) is an innovative method to model flexibility of building loads and effectively coordinate them with other resources at a system level. Unlike a real battery with a dedicated power conversion system for charging control, methods are required for operating building loads to deviate from the baseline to respond to grid signals. This article presents a VB control for a commercial heating, ventilation, and air conditioning (HVAC) system to follow the desired power consumption in real-time by adjusting zonal airflow rates. The proposed method consists of two parts. At the system level, a mixed feedforward and feedback control is used to estimate the desired total airflow rate. At the zone level, two priority-based algorithms are then proposed to distribute the total airflow rate to individual zones. In particular, a zonal airflow limit estimation method is proposed using machine-learning techniques, in contrast to physics-based thermal models in existing studies, to more accurately capture zonal thermal dynamics and improve temperature control performance. An office building on the Pacific Northwest National Laboratory campus is implemented in EnergyPlus, and used to illustrate and validate the proposed control.

On-line melt pool temperature control in L-PBF additive manufacturing

Abstract: Laser powder bed fusion is a promising additive manufacturing technology which has enabled the fabrication of complex-shape, custom-designed, and cost-effective parts with no need for expensive tools and dies. Despite the numerous advantages of this technology, inconsistency in the microstructure and, consequently, the mechanical properties of the fabricated components in the building direction makes it quite challenging to obtain uniform parts in the as-built state. This issue originates from the layer-by-layer melt pool temperature variation caused by the layer-wise nature of this process when a fixed set of process parameters is applied. Accordingly, a layer-wise melt pool temperature control system is beneficial in manipulating the process parameters and therefore adjusting the melt pool temperature. In this study, three different controllers, namely, simple proportional (P), adaptive P, and sliding mode, were designed to control the melt pool temperature in the building direction for Inconel 625 superalloy. An analytical-experimental model was introduced to evaluate the performance of controllers through simulation. A monitoring system having a two-color pyrometer was used to online monitor the temperature for use by the controllers as a feedback signal. The microstructure and microhardness of the final products were evaluated prior to and after employing the melt pool temperature controllers. Compared to the scenario with constant process parameters, the implementation of these controllers led to improved microhardness and microstructure uniformity, resulting from the reduced variation in the primary dendrite arm spacing. The lessons learned from this study can assist in the fabrication of functionally graded materials with engineered microstructures.

Online model for indoor temperature control based on building thermal process of air conditioning system

Abstract: Since there are lots of influencing factors in indoor temperature regulation process of air conditioning system in the large-public building, it is difficult to establish an accurate mathematical model and to implement model-based online control. This paper proposes an online modeling method for indoor temperature regulation characteristic according to building thermal process. A physical-data driven model, which takes the state-space equation solution representation form as the reference structure, is proposed, and the model parameters are identified based on the multiple linear regression analysis . Then, experimental and simulation studies in online and offline have been carried out to validate the proposed modeling method. The contribution of this study is to provide an online model, which can not only retain system physical property but also be updated online simply. The proposed model with building thermal process property will be benefit for terminal controller design for indoor temperature regulation in the air conditioning system.

PID Controlling Approach Based on FBG Array Measurements for Laser Ablation of Pancreatic Tissues

Abstract: In this article, we propose a temperature-based proportional–integral–derivative (PID) controlling algorithm using highly dense fiber Bragg grating (FBG) arrays for laser ablation (LA) of ex vivo pancreatic tissues. Custom-made highly dense FBG arrays with a spatial resolution of 1.2 mm were fabricated with the femtosecond point-by-point writing technology and optimized for LA applications. In order to obtain proper PID gain values, finite element method-based iterative simulation of different PID gains was performed. Then, the proposed algorithm, with numerically derived PID gains, was experimentally validated. In the experiments, the point temperature was controlled at different distances from the laser fiber tip (6.0, 7.2, 8.4, and 10.8 mm). The obtained results report robust controlling and correlation between controlled distance and the resulting area of ablation. The results of the work encourage further investigation of FBG array application for LA control.

Influence of temperature on the performance and life cycle of storage batteries

Abstract: The paper addresses the influence of temperature on the operating life of storage batteries used in autonomous electric transport. We analyzed the studies describing the relationship between the temperature factor and the storage battery life cycle, substantiated the need for temperature control of storage batteries, and considered the existing temperature control systems. Taking into account the advantages and disadvantages of the systems under consideration, we propose a system that provides the best efficiency of storage battery temperature control.

Investigation on the performance enhancement of baffled cold plate based battery thermal management system

Abstract: Liquid cooling is an efficient thermal management method. In response to the lightweight and compact demand faced by the development of battery thermal management system (BTMS), a thin baffled cold plate for liquid-based BTMS was designed. The accuracy of the simulation was verified through experiment. The influence of structure parameters on the heat transfer performance was explored. A structure optimization method called local connection was proposed for heat transfer enhancement. The baffled cold plate was applied to BTMS with battery at 3 C discharge rate to explore the effect on the temperature control performance. The results show that local connection optimization can simultaneously improve the comprehensive heat transfer performance and temperature uniformity of the baffled cold plate, and the maximum increase can be 24.71% and 6.71% respectively compared to Case 0–4-L75. The effect of the improvement is affected by the spacing, position, number of the local slits and the distance between the local slit and the channel corner apex. Local connection optimization can reduce the power consumption of baffled cold plate based BTMS while ensuring the temperature control performance, which can save energy.

A Review of Thermal Property Enhancements of Low-Temperature Nano-Enhanced Phase Change Materials

Abstract: Phase change materials (PCMs) are of increasing interest due to their ability to absorb and store large amounts of thermal energy, with minimal temperature variations. In the phase-change process, these large amounts of thermal energy can be stored with a minimal change in temperature during both the solid/liquid and liquid/vapor phase transitions. As a result, these PCMs are experiencing increased use in applications such as solar energy heating or storage, building insulation, electronic cooling, food storage, and waste heat recovery. Low temperature, nano-enhanced phase change materials (NEPCM) are of particular interest, due to the recent increase in applications related to the shipment of cellular based materials and vaccines, both of which require precise temperature control for sustained periods of time. Information such as PCM and nanoparticle type, the effective goals, and manipulation of PCM thermal properties are assembled from the literature, evaluated, and discussed in detail, to provide an overview of NEPCMs and provide guidance for additional study. Current studies of NEPCMs are limited in scope, with the primary focus of a majority of recent investigations directed at increasing the thermal conductivity and reducing the charging and discharging times. Only a limited number of investigations have examined the issues related to increasing the latent heat to improve the thermal capacity or enhancing the stability to prevent sedimentation of the nanoparticles. In addition, this review examines several other important thermophysical parameters, including the thermal conductivity, phase transition temperature, rheological affects, and the chemical stability of NEPCMs. This is accomplished largely through comparing of the thermophysical properties of the base PCMs and their nano-enhanced counter parts and then evaluating the relative effectiveness of the various types of NEPCMs. Although there are exceptions, for a majority of conventional heat transfer fluids the thermal conductivity of the base PCM generally increases, and the latent heat decreases as the mass fraction of the nanoparticles increases, whereas trends in phase change temperature are often dependent upon the properties of the individual components. A number of recommendations for further study are made, including a better understanding of the stability of NEPCMs such that sedimentation is limited and thus capable of withstanding long-term thermal cycles without significant degradation of thermal properties, along with the identification of those factors that have the greatest overall impact and which PCM combinations might result in the most significant increases in latent heat.