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Core Models Reconstruction of Refrigeration System for Simulation and Corresponding Simplified Models

Author: WangZhan
Tutor: ZhangGuoQiang
School: Hunan University
Course: Heating,Gas Supply, Ventilation and Air Conditioning Engineering
Keywords: Refrigeration system Simulation Qualitative reconstruction Numerical problems Neural Network Simplified alternative model
CLC: TU831.3
Type: Master's thesis
Year: 2005
Downloads: 122
Quote: 1
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Abstract

Refrigeration system simulation, the simulation accuracy and speed is always a contradiction. In order to obtain accurate simulation results, we must create a relatively complex models and procedures for distributed parameter model, to obtain the stability of the calculation results, the number of units typically two hundred or more. This requires a longer simulation time (especially the heat exchanger) for the purposes of the calculation of a single member is not a big problem, it is therefore necessary to carry out, for the system simulation and control strategy simulation purposes, it will seriously affect the simulation speed certain simplified. Classical theory in the long-term theoretical research and practical application has been confirmed qualitatively reasonable, is relatively mature, stronger than the complete neural network to establish a simple black box model for the control of the trend. So, the traditional numerical simulation model and neural network combined with the traditional model to ensure the correctness of the qualitative direction, and the introduction of neural networks to establish the corresponding simplified alternative model for quantitative treatment, a combination of traditional methods and neural network. In this combination, the neural network is only as a function approximation to use. In other words, the first to establish an accurate model, and then seek a simple alternative model. This will ensure the qualitative correctness of the simulation, but also increase the simulation speed of about 2 to 3 orders of magnitude. This article during the first core model of the refrigeration system on the basis of extensive literature reading, qualitative reconstruction suitable for systems with component model. Capillary approximate integral method, a new algorithm process, reconstruction of a one-dimensional countercurrent condenser and evaporator distributed parameter model, analysis and the establishment of small vapor compression refrigeration system's overall general algorithm and special conditions known algorithms. Dissect the hidden numerical problems in the previous model, to correct the error of the previous model imperceptible qualitative, and the corresponding solutions. The author based on neural network, the establishment of a distributed parameter model corresponds to a simplified model. Detailed analysis and optimize the various components of the model in the two-phase area of ??each parameter Discrimination relations, the establishment of a simplified model based on distributed parameter model, to obtain a good approximation effect can significantly improve the simulation speed to establish the utility of the system simulation with the component model basis. Ensure a good approximation of the effect of the case, the calculation speed is improved approximately 2 to 3 orders of magnitude, provides a good practical process for the system simulation research directions. It should be noted that each member is simplified, and as a distributed parameter model of the sample compared, a simplified model of the capillary higher degree of approximation, a simplified model of the heat exchanger as a single member, the maximum absolute error is also reasonable range. However, due to the distributed parameter model calculations and the actual working conditions a certain deviation, there is the risk of expanding the overall actual error. Moreover, when used in the system simulation, due to the multiple iterations of the system, it may result in systematic errors superimposed expanded. Therefore, the simplified model of the subsequent follow-up work must be the accuracy of self-correction, this author has not been able to complete the work.

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