Thermofluid Systems Research Articles

Thermo-Fluid Analysis Using Linear Graph Theory.

When we obtain analytical results for a mechanical system by numerical analysis, we may consider many kinds of physical influence, including electricity, mechanical vibration, heat, and flow. However, it is difficult to deal with each system simultaneously. In this study, with the aim of the convenient analysis of a thermo-fluid system, analysis using linear graph theory is derived, and the transient response analysis for a piping system is carried out. Furthermore, in order to examine the validity of this analysis method, the finite-element method is carried out and its results compared with the simulation results. Through these studies, it is concluded that the convenient method is useful in analyzing mechanical systems including the thermo-fluid system.

A Failure Isolation Strategy for Thermofluid System Diagnostics

The application of microprocessor-based diagnostic strategies to industrial processes provides improved system reliability while reducing maintenance costs. The prompt detection and classification of system anomalies enables reduced troubleshooting by technicians and minimizes the misclassification of system degradations. In this paper, an experimental-based multiple hypothesis failure isolation scheme for small-scale thermofluid systems is presented. The proposed classification strategy combines dynamic modeling, control theory, multivariate statistics, and pattern recognition to develop a methodology that may be tailored for a variety of applications. The primary goal of this study is the reduction of modeling activities associated with the set of hypothesized failure modes. The overall performance of the isolation scheme is investigated for a series of experimentally simulated heat pump failures.

A course on microprocessor-based control systems

A course on microprocessor-based control systems in which an associated laboratory provides hands-on experience for concepts introduced in lectures is described. Laboratory experiments emphasize a variety of electromechanical and thermofluid control systems. Students begin at the gate and transistor level, progress through assembly software development, and finish by implementing data acquisition and control software on particular devices. The course is taught to both senior undergraduate students and first-year graduate students. >

Linearizing Transformations for the Thermal Dynamics of Gas Compression Processes

Linearizing transformations provide insight into gas compression processes frequently encountered in chemical and thermofluid systems as well as in hydraulic and pneumatic control elements. Significant nonlinear dynamic effects, resulting in hysteresis and energy dissipation, obviate the common use of polytropic exponents. However, these same effects are simply quantified through the analysis of an imbedded log-linear system. Response predictions for the linearized and nonlinear models are compared for both harmonic and transient inputs.

Extended Kalman Filter for Reconstruction of a Nonlinear Thermofluid System

Extended Kalman filter technique is used to develop an observer for a nonlinear thermofluid system, namely a heat pump. The observer’s optimal gain matrix is designed based on the eigenvalue distribution, integration time step, and stability of the system along a desired trajectory. The observer response is compared with experimental data and very good agreement is obtained.

Application of Bond Graphs to Thermofluid Processes and Systems

Over the past few years a study was focused on the development of bond graphs for thermofluid processes and systems using the true power variables of temperature and time rate of change of entropy. This paper summarizes results of the study. Discussion begins with the study of a simple case of single phase incompressible fluid flow and ends with a completely general case of multiphase, variable density flow. Variations in density require introduction of the momentum equation to the bond graph. Inclusion of entropy as a state variable necessitates the use of Gibb’s equation and its representation by means of bond graphs. This paper presents these formulations and representations, and compares dynamic results predicted by bond graphs with those of classical approaches.

Representation of Measured Ejector Characteristics by Simple Eulerian Bond Graph Models

Ejectors (or jet pumps) are highly reliable pure fluidic devices very commonly used in power plants, propulsion systems, petrochemical processes and other thermofluid systems. However, little off-design data has been available in a form suitable for dynamic simulation and control system design. Fortunately, concerns of the nuclear industry have recently led the Idaho National Engineering Laboratory (INEL) to obtain, from their LOFT Test Support facility, ejector test data sufficiently extensive to formulate a complete model accurately describing all flow conditions. Thus an elementary fixed-constant bond graph structure will approximate complete ejector characteristics, while a model only slightly more complex fits all INEL data within experimental scatter.

An Introduction to the Dynamics and Control of Thermofluid Processes and Systems

An Introduction to the Dynamics and Control of Thermofluid Processes and Systems

Microprocessor-Based Failure Detection of Heat Pumps

Thermofluid processes and system undergo spatial and temporal variations in both fluid and thermal properties. Therefore, they are highly nonlinear and coupled. This paper presents an approach to failure detection of a heat pump. The technique involves modeling of the system, design of an observer and statistical analysis for failure identification. This paper focuses on the first two major steps. A bond graph approach is used to model the heat pump and an extended linear observer technique is used to derive an optimal state estimator for the nonlinear thermofluid system. A Z-151 microcomputer is used to implement the observer and other required software. The results of the model and the observer are compared with experimental data and very good agreement have been obtained.

Decoupling control of a thermofluid system

Decoupling control of a thermofluid system

State variables and pseudo bond graphs for compressible thermofluid systems

State variables and pseudo bond graphs for compressible thermofluid systems

熱流体系の騒音に関する研究会報告(研究会報告No.71)

熱流体系の騒音に関する研究会報告(研究会報告No.71)