Example Of Heat Exchanger Research Articles

Fault-tolerant control for a class of linear interconnected hyperbolic systems by boundary feedback

This paper considers a fault-tolerant control problem for a class of interconnected linear hyperbolic partial differential equation systems. Both subsystem faults and coupling faults are considered. Firstly, the well-posedness of the faulty system is analyzed by using semigroup theory. Secondly, for the fault-free case, a stabilizing boundary feedback control based on small-gain theorem is proposed. Consequently, in the presence of faults, fault recoverability conditions are established that maintain the stability of the faulty systems. The fault-tolerant control strategies are also provided. A heat exchanger example is taken to illustrate the effectiveness and practicality of the proposed methods.

Fabrication and Analysis of Counter Flow Helical Coil Heat Exchanger

Heat recovery is the capture of energy contained in fluids otherwise that would be lost from a facility. Heat sources may include heat pumps, chillers, steam condensate lines, hot flue gases from boiler, hot air associated with kitchen and laundry facilities, exhaust gases of the engines, power-generation equipment. Helical coil heat exchanger is one of the devices which are used for the heat recovery system. A heat exchanger is a device used to transfer heat between two or more fluids with different temperatures for various application including power plants, nuclear reactors, refrigeration & air condition system, automotive industries, heat recovery system, chemical processing and food industries. Common examples of heat exchangers in everyday use are air pre- heaters and conditioners, automobile radiators, condensers, evaporators, and coolers In present paper analysis of counter flow heat exchanger is done and then variations of various dimensionless numbers i.e. Reynolds Number, Nusselt's Number and Dean's number are studied.

Numerical computation of 3D heat transfer in complex parallel heat exchangers using generalized Graetz modes

We propose and develop a variational formulation dedicated to the simulation of parallel convective heat exchangers that handles possibly complex input/output conditions as well as connection between pipes. It is based on a spectral method that allows to re-cast three-dimensional heat exchangers into a two-dimensional eigenvalue problem, named the generalized Graetz problem. Our formulation handles either convective, adiabatic, or prescribed temperature at the entrance or at the exit of the exchanger. This formulation is robust to mode truncation, offering a huge reduction in computational cost, and providing insights into the most contributing structure to exchanges and transfer. Several examples of heat exchangers are analyzed, their numerical convergence is tested and the numerical efficiency of the approach is illustrated in the case of Poiseuille flow in tubes.

Adaptive Observer Based Data-Driven Control for Nonlinear Discrete-Time Processes

In this paper, two adaptive observer-based strategies are proposed for control of nonlinear processes using input/output (I/O) data. In the two strategies, pseudo-partial derivative (PPD) parameter of compact form dynamic linearization and PPD vector of partial form dynamic linearization are all estimated by the adaptive observer, which are used to dynamically linearize a nonlinear system. The two proposed control algorithms are only based on the PPD parameter estimation derived online from the I/O data of the controlled system, and Lyapunov-based stability analysis is used to prove all signals of close-loop control system are bounded. A numerical example, a steam-water heat exchanger example and an experimental test show that the proposed control algorithm has a very reliable tracking ability and a satisfactory robustness to disturbances and process dynamics variations.

Nonlinear process identification and predictive control by multiparameter models

According to the multi-model approach a nonlinear dynamical process is approximated in different working points by local valid linear models. The global valid model output is calculated as the weighted sum of the sub-model outputs. The parameters of the Gaussian weighting function can be chosen by optimization. The computation time can be reduced if instead of the model outputs the parameters (for example static gain and time constant) of the local valid models are merged. The global valid nonlinear model can be used e.g., for model based predictive control. The new, multi-parameter method is illustrated by a heat exchanger example.

Nonlinear Process Identification and Predictive Control by the Weighted Sum of Multi-Model Outputs

Most industrial processes are nonlinear. In such a case only a nonlinear model valid for the whole working area can ensure a good controller design. The nonlinear process is approximated by a multi-model consisting of the intelligent combination of some linear sub-models. As a very practical way the following identification strategy was used: independent model parameter estimation in the different working points and the calculation of the global valid model output as the weighted sum of the sub-models. As a weighting function the Gaussian function is used. The parameters of the Gaussian function were chosen either without or with optimization of the identification cost function. The global valid nonlinear model was used for model based predictive control. A heat exchanger example illustrates the method.

A set based approach to detection and isolation of faults in multivariable systems

In this paper, we propose a set based approach for detecting faults in input/output channels of a closed-loop multivariable system. This approach works with deterministic bounds on measurement noises, disturbances, and fault signals, which may be attractive in some applications. The fault detection problem is formulated as an optimization problem in the state space framework. The dimensionality of the optimization problem increases with time. In order to allow the problem dimension to be fixed at a pre-specified value, a moving horizon based approach is proposed. When the horizon is moved, a parallelotope covering the feasible region of the initial state is propagated by using the ‘Recursive Optimal Bounding Parallelotope’ methodology. Diagnosis of the location of a fault is carried out by using a series of detection tests. The usefulness of the algorithm for detection and diagnosis is demonstrated by using a heat exchanger example.

Reduced spurious solutions by using intersection algorithm in qualitative simulation

Abstract A method is presented to incorporate the intersection algorithm into the elimination of spurious solution and shrinkage of ambiguous variables in qualitative simulations. Since, for a given model structure, the qualitative simulation is sound but incomplete, the spurious solutions are inevitably included in the solution set. To be appropriately applied to these solutions, it is important to reduce the spurious solutions. Since the true solution is always existing in the solution, by incorporating them into the intersection of solutions, one can quickly reduce the spurious solutions. A heat exchanger example is used to illustrate the effectiveness of this method. Through this complicated example, the simulation results show that spurious solutions can be reduced from 26 to 4, and the number of ambiguous variables is reduced from 9 to 2. Results also show that the proposed method is effective in reducing spurious solutions in qualitative simulation.

Weighted residual methods and the suboptimal control of distributed parameter systems†

A suboptimal control algorithm for distributed parameter systems is developed in a framework which synthesizes weighted residual methods and mathematical programming. The heat exchanger example of Koppel et al. (1968) is employed for introducing the algorithm. First, the Galerkin procedure with polynomial modes is applied to obtain a lumped ODE model for the distributed parameter system. Then the state and control variables of the lumped control problem are approximated by cubic splines on a uniform mesh. Through collocation at the knots, the ODE model is reduced to a sot of linear algebraic equations and the suboptimal control is determined from the solution of a quadratic programming problem with sparse matrices. Numerical results for the heat exchanger example are presented and compared with those obtained by the authors (Neuman and Sen 1972) using the Ritz-Trefftz algorithm (Bosarge and Johnson 1970) for the lumped control problem. For this example, the two algorithms yield essentially identical resul...

A rapid sub-optimal control algorithm for distributed parameter regulator problems †

Through the heat exchanger example of.Koppel et at. (1968) u rapid sub-optimal control algorithm is developed for optimal regulator problems in linear distributed parameter systems. The Galerkin approximation is first applied to obtain a lumped ODE model for the distributed parameter system. Then, a sub-optimal open-loop control for the resulting linear ODE optimal regulator problem is obtained through the Ritz-Trefftz algorithm of Bosarge and Johnson (1970). One-dimensional polynomial basis functions (modes) are employed to approximate both time and spatial behaviour throughout. To facilitate mode selection, emphasis is placed upon sequential ono-dimensional approximations rather than upon a single multidimensional approximation. Applications of the resulting algorithm are characterized by low storage and on-line computational requirements. Numerical results for the heat exchanger example are presented and compared with those currently available in the literature. Performance of the algorithm with a small number of polynomial modes is assessed and experimental user-oriented guidelines are provided.

Optimal feedback control of a class of linear tubular processes

AbstractOptimal output feedback control low requiring measurment of the output only has been considered for a class of tubular processes. The advantage of this formulation, which requires a single measurement of the output only, over a previous result which requires an infinite number of measurements, has been demonstrated through a heat exchanger example. However, when the terminal time is grater than the residence time of fluid, a time‐delay element is needed.