Control Of Thermal Processes Research Articles

Improvement of the Wear Resistance of Ferrous Alloys by Electroless Plating of Nickel

The electroless nickel (Ni) and composite nickel – nanodiamond (Ni+DND) coatings are investigated in this study. The method EFTTOM-NICKEL for electroless nickel plating with nanosized strengthening particles (DND 4-6 nm) is applied for the coating deposition. The coatings are deposited on ferrous alloys samples. The wear resistance of the coatings is performed by friction wear tests under 50-400 MPa loading conditions – in accordance with a Polish Standard PN-83/H-04302. The microstructure observations are made by optic metallographic microscope GX41 OLIMPUS and the microhardness is determined by Vickers Method. Tests for wear resistance, thickness and microhardness measurements of the coatings without heat treatment and heat treatment are performed. The heat treatment regime is investigated with the aim to optimize the thermal process control of the coated samples without excessive tempering of the substrate material. The surface fatigue failure is determined by contact fatigue test with the purpose to establish suitable conditions for production of high performance materials.

Control of a Thermal Airflow Process - Part I: System Identification

This article was motivated from a practical work on modeling and control of a time-delayed thermal airflow process using adaptive techniques. The work was divided into two parts: (I) the modeling of the process using system identification methods, with main concerns to the numerical robustness of the identification, and (II) the digital control of the process using adaptive self-tuning control, with main concerns to the adaptation of the controller to changes in the process dynamics. This article presents the first part of the work. The thermal airflow system was represented by an ARMAX model, whose parameters were identified using the Recursive Least Squares method, based on two approaches: the Matrix Inversion Lemma, and the Bierman’s UD Factorization. The results obtained show that the last approach has greater numerical robustness and is more suitable for applications of adaptive control – the second part of the work, described in a separate article.

Control of a Thermal Airflow Process - Part II: Adaptive Self-Tuning Control

This article was motivated from a practical work on modeling and control of a time-delayed thermal airflow process using adaptive techniques. The work was divided into two parts: (I) the modeling of the process using system identification methods, with main concerns to the numerical robustness of the identification, and (II) the digital control of the process using adaptive self-tuning control, with main concerns to the adaptation of the controller to changes in the process dynamics. This article concerns the second part of the work. An adaptive self-tuning controller was implemented to improve the performance of the thermal airflow process. At each sampling interval, the process model is updated using an on-line identification strategy developed in the first part of the work. Based on the identification, the controller is self-tuned to compensate for eventual changes in the process parameters. Intentional disturbances were made in the process dynamics in order to evaluate the adaptation performance of the control system.

Robust stability of thermal control systems with uncertain parameters: The graphical analysis examples

This paper is intended to present the investigation of robust stability for integer order or fractional order feedback control loops affected by parametric uncertainty and time-delay(s) with special emphasis on the thermal control systems. The applied graphical method is based on the numerical calculations of the value sets and the zero exclusion condition. Three robust stability examples inspired by control of the real-world thermal processes are used for demonstration of the technique applicability. Namely, the work deals with the analysis of a shell-and-tube heat exchanger which was identified as the (integer order) time-delay model with parametric uncertainty, a heat transfer process modeled as the fractional order time-delay plant with parametric uncertainty, and a heating–cooling system with a heat exchanger described by the anisochronic model with internal delays and parametric uncertainty.

Применение современных информационных технологий в учебном процессе и научных исследованиях

The article describes the main trends of applying modern information technologies (ITs) in education for scientific research purposes, in advanced training and retraining of specialists in power engineering. The trends are illustrated on the examples of application of the above-mentioned ITs at the Departments of Thermal Power Plants and Automated Thermal Process Control Systems of the Thermal and Nuclear Power Engineering Institute within the National Research University “Moscow Power Engineering Institute”. It is shown that the University management pays much attention to the centralized provision of educational process and scientific research with the information technologies of new generation. Additionally in order to improve the educational process and taking into account the particular qualities of the specialists graduated, modern educational laboratories and centers of the world level have been created and successfully operating at these departments providing the necessary conditions for applying the latest achievements in various fields of science and technology. The state of affairs in these three main trends of applying ITs is analyzed: in modern software systems, new-generation training simulators and interactive forms of education.

On the efficiency of solving optimal control problems by means of fast automatic differentiation technique

An efficient method is introduced for solving the problems of optimal control of thermal processes with phase transitions. The following statement is formulated and proved: the time of computing the components of the gradient of the objective function by means of the proposed method does not exceed the time of computing two values of the function.

Comparison of airf low environmental effects on thermal fabrics

Smart thermal textiles are becoming increasingly popular and temperature precision is one of the important targets in their industrialization and commercialization. Some thermal products do not rely on temperature sensors but rather the input electric current pulse to achieve thermal control. In this situation, the surrounding environment, especially ventilation, can greatly affect the thermal control process. Therefore, in this paper, a case study of an apparel system will be provided to study the effect of airflow on the heating process of thermal fabric. The relationship between temperature precision and ventilation is determined when the air flows at any angle to the surface of the thermal fabric. The results show that the thermal conductivity is proportional to the wind speed when the wind speed is high; in contrast, when the wind speed is near to zero, the thermal conductivity of the thermal fabric will not proportionally tend to zero as the result of self-generated heat transfer. This research also shows that the air inflow angle and the wind direction has little effect on the heat dissipation of thermal fabric. This research may generate the data archive and become a valuable reference for future soft thermal studies. It is expected that the developed system will span multidisciplinary gaps and contribute to a new form in a precise and controllable way within the textile industry.

Technology of Ultrasonic Control Of Gas-Shielded Welding Process

A new approach to implementation of electrode metal transfer control under MAG, MIG welding is suggested. The process ensures control of thermal and crystallization processes, stabilizes the time of electrode metal drop formation. The results of the research allow formulating the basic criteria of electrode metal transfer control via ultrasonic exposure, determining the conditions of producing a more equilibrium structure of deposit metal.

Nature inspired, multi-functional, damage tolerant thermal spray coatings

Abstract Design and fabrication of ceramic materials that simultaneously provide adequate strength and toughness is of importance in engineering applications. Nature has demonstrated it is feasible to achieve this duality in properties through a combination of materials and microstructural engineering. The nacreous layer within the abalone shell is perhaps the most notable demonstration of such combined properties through unique combination of ceramic and polymeric material in an ordered, layered assembly. Recent studies have shown that through appropriate control of thermal spray processes and post-spray polymer infiltration of the deposited ceramic, it is possible, to some extent, to harness nacre's microstructural attributes resulting in the material's dramatic improvement in both strength and toughness. This paper seeks to build upon previous work of layered, natural inspired design seen in nacreous materials, with an emphasis on abrasion and contact damages. Two distinct thermal spray ceramic templates, one nacreous analogue and one standard thermal spray template, have been reproduced here and evaluated with regards to their functional performance e.g. abrasive wear and particle impact. The results from this study confirm the mechanical property improvements after polymer infiltration, and further show that it is indeed feasible to achieve improved surface properties from natural design principles and processing innovations.

Improving Processes of Mechanized Pulsed Arc Welding of Low-Frequency Range Variation of Mode Parameters

A new technology of low-frequency modulation of the arc current in MAG and MIG welding is presented. The technology provides control of thermal and crystallization processes, stabilizes the time of formation and crystallization of the weld pool. Conducting theoretical studies allowed formulating the basic criteria for obtaining strong permanent joints for high-duty structures, providing conditions for more equilibrium structure of the deposited metal and the smaller width of the HAZ. The stabilization of time of the formation and crystallization of the weld pool improves the formation of the weld and increases productivity in welding thin sheet metal.

Technology of ultrasonic control of gas-shielded welding process

A new approach to implementation of electrode metal transfer control under MAG, MIG welding is suggested. The process ensures control of thermal and crystallization processes, stabilizes the time of electrode metal drop formation. The results of the research allow formulating the basic criteria of electrode metal transfer control via ultrasonic exposure, determining the conditions of producing a more equilibrium structure of deposit metal.

Ultrafast laser processing of materials: from science to industry.

Processing of materials by ultrashort laser pulses has evolved significantly over the last decade and is starting to reveal its scientific, technological and industrial potential. In ultrafast laser manufacturing, optical energy of tightly focused femtosecond or picosecond laser pulses can be delivered to precisely defined positions in the bulk of materials via two-/multi-photon excitation on a timescale much faster than thermal energy exchange between photoexcited electrons and lattice ions. Control of photo-ionization and thermal processes with the highest precision, inducing local photomodification in sub-100-nm-sized regions has been achieved. State-of-the-art ultrashort laser processing techniques exploit high 0.1–1 μm spatial resolution and almost unrestricted three-dimensional structuring capability. Adjustable pulse duration, spatiotemporal chirp, phase front tilt and polarization allow control of photomodification via uniquely wide parameter space. Mature opto-electrical/mechanical technologies have enabled laser processing speeds approaching meters-per-second, leading to a fast lab-to-fab transfer. The key aspects and latest achievements are reviewed with an emphasis on the fundamental relation between spatial resolution and total fabrication throughput. Emerging biomedical applications implementing micrometer feature precision over centimeter-scale scaffolds and photonic wire bonding in telecommunications are highlighted.

Optimal Control of Nonstationary Thermal Process with Axial Symmetry

Optimal Control of Nonstationary Thermal Process with Axial Symmetry

Airways in Apartment Buildings as a Method of Thermal Control

In general, the majority of modern apartment buildings are rather high. Altitude of such structures attains 50 meters. It is clear that for such high structures every extra meter of elevation costs a lot. For this reason, architects are trying to avoid adding attics above the last floor of the buildings. However, attic is not only an architectural element. It is an important part of the thermal control process of the entire building, especially of the apartments located on the last floor. In this article, construction of airways under the roof is suggested and discussed in detail. Airway acts as an attic, but has a significantly lower construction cost due to the lower height. Application of this technology allows providing comfortable microclimate on the living quarters in an economical way.

Sliding mode control design for a rapid thermal processing system

A sliding mode control strategy is developed for temperature control of a rapid thermal processing (RTP) system to enhance temperature accuracy and uniformity when heating in this work. Temperature dynamics of the RTP is nonlinear and infinite-dimensional while order of the controller should be finite due to implementation limitations. Developing a nonlinear low-order controller for the system is important if accurate and uniform control of the temperature is required. This work addresses this issue by developing a sliding mode controller based on the dominant modes of the system. The schemes are applied to a RTP system and excellent performances are achieved.

Identification of Thermal Process Based on Relevance Vector Machine and Firefly Algorithm

Thermal process usually has the characteristics of nonlinearity and uncertainty, so it is difficult to establish the nonlinear model by the traditional method of describing the dynamic mathematical model of thermal process and accurately implement optimal control of thermal process. This paper provides an identification method of thermal process based on relevance vector machine and firefly algorithm, and the modeling results are compared with those by minimal resource allocation network and support vector regression. The simulation results show that the method is effective, and the model has high accuracy and can be directly used in control algorithm based on the model.

Real-time optimal control of a special distributed parameter system

The problem of constructing positional solutions under the real-time optimal control of a parabolic system is considered. A method for finding an approximate solution of the problem is justified. According to the method, the problem is reduced to the optimal control problem for a large dynamical ordinary differential system, which is solved by applying a dynamical version of the dual linear programming method. The fundamental matrix of the homogeneous part of the system is quasi-decomposed to save computation time at the iterations of the method. An optimal controller is described whereby the current optimal feedback values (positional solution) are constructed in real time. Numerical results are presented for the control of thermal processes in a rod.

Real‐time monitoring of thermal processes by reduced‐order modeling

SummaryThis work presents a simple technique for real‐time monitoring of thermal processes. Real‐time simulation‐based control of thermal processes is a big challenge because high‐fidelity numerical simulations are costly and cannot be used, in general, for real‐time decision making. Very often, processes are monitored or controlled with a few measurements at some specific points. Thus, the strategy presented here is centered on fast evaluation of the response only where it is needed. To accomplish this, classical harmonic analysis is combined with recent model reduction techniques. This leads to an advanced harmonic methodology, which solves in real time the transient heat equation at the monitored point.In order to apply the reciprocity principle, harmonic analysis is used in the space‐frequency domain. Then, Proper Generalized Decomposition, a reduced order approach, pre‐computes a transfer function able to produce the output response for a given excitation. This transfer function is computed offline and only once. The response at the monitoring point can be recovered performing a computationally inexpensive post‐processing step. This last step can be performed online for real‐time monitoring of the thermal process. Examples show the applicability of this approach for a wide range of problems ranging from fast temperature evaluation to inverse problems. Copyright © 2014 John Wiley & Sons, Ltd.

Photoinduced degradation of organic solar cells with different microstructures

An in situ measurement setup is established to investigate the photoinduced degradation effects in a controllable inert gas ambient environment for the two different microstructures of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyricacid methyl ester (PCBM) bulk-heterojunction organic solar cells. The two devices are fabricated with the solvent vapor drying process followed by a thermal annealing (vapor drying device) and only a normal thermal annealing process (control device), respectively. Their power conversion efficiencies (PCEs) and aging features are compared. Their different degradation behaviors in light absorption are confirmed. In addition, irradiation-induced changes in both nanostructure and surface morphology of the P3HT:PCBM blend films treated with two different fabrication processes are observed through scanning electron microscopy and atomic force microscopy. Aggregated bulbs are observed at the surfaces for control devices after light irradiation for 50 h, while the vapor drying devices exhibit smooth film surfaces, and the corresponding device features are not easy to degrade under the aging measurement. Thus the devices having solvent vapor drying and thermal annealing show better device stabilities than those having only the thermal annealing process.

Control of Thermal Conductance of Peltier Device Using Heat Disturbance Observer

SummaryIn industry, temperature control and heat flow control are now applied in many thermal devices, including Peltier devices, which facilitates heat transfer by the Peltier effect. Generally, temperature control compensates for heat flowing from the external environment, while heat actively flows into the system during heat flow control. Thus, temperature control and heat flow control differ from each other. However, there have been no detailed discussions of a thermal control process in which the thermal conductance control ranges between 0 and ∞. This paper focuses on thermal conductance control and the construction of a thermal conductance control system for a Peltier device using a heat disturbance observer. When using the thermal conductance controller, the thermal conductance control is altered and the system becomes thermally compliant with the external environment. This paper also presents experimental results that confirm the validity of the proposed control system. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 185(4): 44–52, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22411